A multi-gene dataset reveals a tropical New World origin and Early Miocene diversification of croakers (Perciformes: Sciaenidae)

Spotting mistakes: Reappraisal of Spotted Drum Stellifer punctatissimus (Meek & Hildebrand, 1925) (Teleostei: Sciaenidae) reveals species misidentification trends and suggests latitudinal sexual dimorphism

A major part of the described species is understudied, falling into the Linnean shortfall. This is a major concern for cryptic species, which require integrative approaches to better evaluate their diversity. We conducted morphological analyses using specimens of Stellifer punctatissimus, S. gomezi, and S. menezesi to reassess their taxonomical identity. We evaluated the allometric and sexual components of the morphology of the Stellifer punctatissimus species complex, and tested and discussed species hypotheses. The combined evidence of our work and previous studies agrees with the current morphological hypothesis of three species, as opposed to the two-lineage molecular hypothesis. However, as cryptic species, they overlap in most their traits, especially females and juveniles. Previously unaccounted variation of allometric and sexually dimorphic characters in this species complex revealed a confounding effect that might explain past and current taxonomic errors. Taxonomical practice of using body depth as a diagnostic character had led to juveniles and females being, respectively, described as a different species or wrongfully identified. Hence, taxonomical studies demand better assessment of allometric and sexual dimorphism components. Herein, we present new characters in a key to the Atlantic species of Stellifer, which disclose size and sexual variation unnoticed in previous studies. The contrasting growth patterns among these species could imply distinct habitat use. As a result, it could be suggested that such species are under different threats, which highlights the need of differential management and conservation strategies.

A trawl collected dataset of Johnius (Actinopterygii, Sciaenidae) species in central-western Taiwanese waters

Background

Sciaenidae is one of the most important coastal fisheries in Taiwan, both in production and economic value. It is also significant as the main targetted diet of Chinese white dolphins, Sousachinensis, especially for the genus Johnius, such as J.taiwanensis, J.belangerii and J.distinctus, which is primarily found in central-western Taiwan coastal waters. Despite an abundance of Johnius species occurrences reported in the Global Biodiversity Information Facility (GBIF) and the Taiwan Biodiversity Information Facility (TaiBIF) data portals (Mozambique, Australia, Taiwan, Korea, India, Indonesia, South Africa, Pakistan, Vietnam and China), there are no specific datasets that properly document the regional distribution of this genus, especially in Taiwanese waters. Thus, this paper describes a dataset of genus Johnius occurrences in waters on the central-western coast of Taiwan. The data collection for the present study was conducted from 2009 until 2020 and comprised 62 sampling events and 133 occurrence records. All fish specimens were collected by trawling in Miaoli, Changhwa and Yunlin Counties, Taiwan and brought back to the lab for identification, individual number count and body weight measurement. These processing data have been integrated and established in the Taiwan Fish Database and published in GBIF. This dataset contains six Johnius species and 2,566 specimens, making it comprehensive Johnius fish fauna and spatial distributional data on the coastal habitat in central-western Taiwanese waters.

New information

This dataset contains 133 occurrence records of Johnius species (Sciaenidae) with 2,566 specimens, making it the most extensive public dataset of Johnius distribution records in Taiwan. The publication of this dataset through the TaiBIF and GBIF dataset platforms demonstrated that the number of Johnius spatial and temporal records in Taiwan waters is influenced by the topographical structure of the Changyun Rise (CYR) in combination with the cold current of the China Coastal currents and bound with the warm currents of the Kuroshio and the South China Sea on the central-western coast of Taiwan. The data serve as the foundation for understanding the biogeography and Johnius species ecology in Taiwan's coastal waters, which present a 2°C water temperature difference split at the CYR.

Species delimitation by DNA barcoding reveals undescribed diversity in Stelliferinae (Sciaenidae)

Stelliferinae is the third most speciose subfamily of Sciaenidae, with 51 recognized species arranged in five genera. Phylogenies derived from both morphological and molecular data support the monophyly of this subfamily, although there is no general consensus on the intergeneric relationships or the species diversity of this group. We used the barcoding region of the cytochrome oxidase C subunit I (COI) gene to verify the delimitation of Stelliferinae species based on the Automatic Barcode Gap Discovery (ABGD), Generalized Mixed Yule Coalescence (GMYC), and Bayesian Poisson Tree Process (bPTP) methods. In general, the results of these different approaches were congruent, delimiting 30-32 molecular operational taxonomic units (MOTUs), most of which coincided with valid species. Specimens of Stellifer menezesi and Stellifer gomezi were attributed to a single species, which disagrees with the most recent review of this genus. The evidence also indicated that Odontoscion xanthops and Corvula macrops belong to a single MOTU. In contrast, evidence also indicates presence of distinct lineages in both Odontoscion dentex and Bairdiella chrysoura. Such results are compatible with the existence of cryptic species, which is supported by the genetic divergence and haplotype genealogy. Therefore, the results of the present study indicate the existence of undescribed diversity in the Stelliferinae, which reinforces the need for an ample taxonomic review of the fish in this subfamily.

A new freshwater Ceratomyxa species (Myxozoa: Ceratomyxidae) parasitizing a sciaenid fish from the Amazon Basin, Brazil

Myxozoans of Ceratomyxidae Doflein, 1899 are common coelozoic parasites of marine life, and are also found less frequently in freshwater fish. The present study describes Ceratomyxa ranunculiformis n. sp. as a new freshwater myxosporean species infecting the gall bladder of the Amazonian sciaenid Plagioscion squamosissimus. The new Ceratomyxa was described based on its host, myxospore morphology, ribosomal rDNA gene sequencing, parasite distribution, and phylogenetic analysis. Immature and mature plasmodia were tadpole-shaped or pyriform, and exhibited slow undulatory motility. The myxospores were elongated and crescent-shaped in the frontal view, with a sutural line between two valves, which had rounded ends. The measurements of the formalin-fixed myxospores were: average length 4.9 (4.0-6.6) μm, average thickness 37.6 (32.4-43.9) μm, average posterior angle 165° (154°-173°). Two ovoid polar capsules of equal size, average length 2.0 (1.4-3.0) μm and average width 1.9 (1.4-2.4) μm, were located adjacent to the suture and contained polar filaments with 2-3 coils. The integrated comparative analysis of the morphological characteristics and molecular analyses of the ribosomal rDNA genes supported the identification of a new species of coelozoic Ceratomyxa. Maximum likelihood analyses showed the new species clustering within a well-supported clade, together with all the other Amazonian freshwater ceratomyxids.

Form function of sulcus acusticus of the sagittal otolith in seven Sciaenidae (Acanthuriformes) species using geometric morphometrics (southwestern Atlantic)

The morphology of otoliths determines the function they perform, and it is influenced by genetic and environmental factors. Knowing those relationships is necessary to understand the role of hearing in fish. The objectives of this work were: exploring the shape of the sulcus of the sagittal otolith in seven species of Sciaenidae, in relation to sound production, and analyzing whether the shape and size of the sulcus can be used as a phylogenetic character. For this purpose, geometric morphometry analysis was carried out using landmarks data. It was found that there is an influence of size on the shape of the sulcus, and significant differences were found between the shapes of the sulcus (permutational multivariate analysis of variance). Three general shapes of the sulcus were identified (using principal component analysis, canonical variate analysis, and clustering): (1) in species that produce sounds at dominant frequencies <350 Hz, the deformation of the sulcus showed a tendency towards circularity of the ostium; (2) in those species that produce sounds at frequencies >350 Hz, the ostium showed a flattened ovoid shape, and the cauda increased its length; (3) the species that do not produce sounds, did not show any modifications, relative to the form of consensus. Despite finding sister species that presented similar sulcus shapes in the phylogeny, the results did not confirm that this can be used as a phylogenetic character. This work discusses whether the combined effects of phylogenetic legacy and natural functional selection have led to convergent evolution for the sulcus form. The differences presented by the sulcus of species that occupy the same clade, could indicate that there is a displacement of characters. The sagittal otolith and the sensory macula associated with the sulcus acusticus are highly plastic structures that are subject to strong evolutionary pressure in relation to environmental and behavioral factors, resulting in great variability in shapes that can be associated with a specific character. The variation in the shape of the sulcus would allow the analysed species to coexist in the same coastal soundscapes, without losing their particular hearing needs, even in case of overlapping their spatial and temporal distribution areas.

The Phylogenetic Relationships of the Family Sciaenidae Based on Genome-Wide Data Analysis

Uncertainty and controversy exist in the phylogenetic status of the Sciaenidae family because of the limited genetic data availability. In this study, a data set of 69,098 bp, covering 309 shared orthologous genes, was extracted from 18 genomes and 5 transcriptomes of 12 species belonging to the Sciaenidae family and used for phylogenetic analysis. The maximum likelihood (ML) and Bayesian approach (BA) methods were used to reconstruct the phylogenetic trees. The resolved ML and BA trees showed similar topology, thus revealing two major evolutionary lineages within the Sciaenidae family, namely, Western Atlantic (WA) and Eastern Atlantic−Indo−West Pacific (EIP). The WA group included four species belonging to four genera: Cynoscion nebulosus, Equetus punctatus, Sciaenops ocellatus, and Micropogonias undulatus. Meanwhile, the EIP group formed one monophyletic clade, harboring eight species (Argyrosomus regius, A. japonicus, Pennahia anea, Nibea albiflora, Miichthys miiuy, Collichthys lucidus, Larimichthys polyactis, and L. crocea) from six genera. Our results indicated that the Western Atlantic (WA) group was more ancient in the studied species, while the Eastern Atlantic−Indo−West Pacific (EIP) group was a younger group. Within the studied species, the genera Collichthys and Larmichthys were the youngest lineages, and we do not suggest that Collichthys and Larmichthys should be considered as one genus. However, the origin of the Sciaenidae family and problems concerning the basal genus were not resolved because of the lack of genomes. Therefore, further sampling and sequencing efforts are needed.

Otolith shape analysis supports three cryptic species in the Stellifer punctatissimus complex (Acanthuriformes: Sciaenidae)

Abstract Sciaenidae species (croakers and drums) are known for specializations in their sensory apparatus, such as otoliths and lateral line. Within this family, some Stelliferinae members remain taxonomically unresolved due to their cryptic aspects and low phenotypic disparities. Stellifer punctatissimus comprises a species complex putatively formed by three species on morphological grounds, but molecular data have indicated only two evolutionary lineages. Herein, we tested the hypothesis that this complex is composed of Stellifer gomezi (GM), S. menezesi (MN), and S. punctatissimus (PC), using the otolith shape and morphology to differentiate them. Seventy-seven sagittal otoliths (GM = 30, MN = 30, PC = 17) were photographed to outline the otolith contour by Elliptical Fourier descriptors. Ten otoliths for each group were used to detect shape variation in the sulcus acusticus through semilandmarks. Differences in otolith shape contour were recorded among the species by PERMANOVA (Pseudo-F = 4.02, df = 2, p < 0.001) and corroborated by the Linear Discriminant Analysis, which demonstrated three partially segregated groups with satisfactory re-classification rates. A larger sulcus acusticus (GM and MN), rounded projection (PC), and distinct rectangularity pattern were also recorded. Our results support the morphological hypothesis and thus contribute to narrowing the taxonomic gaps in Sciaenidae.

Fish assemblage patterns in a subtropical estuary in southern Brazil

Abstract: In this study, the relationship between fish assemblage structure and environmental factors was analyzed in a bay in southern Brazil. Fish were collected every two months between February and December 2002 at six sampling sites using bottom trawl nets. Abiotic data (salinity, temperature, rainfall, and depth) and biotic data (number of individuals, biomass, and total length of individuals from each species) were obtained. In total, 56 fish species representing 27 families were collected. Assemblage structure varied with seasonality, as was evidenced by the variation in temperature and rainfall in each season. Catches showed a high abundance of demersal fishes, particularly Genidens genidens, Eucinostomus gula, and E. argenteus.

Comparative Phylogeography and Phylogeny of Pennah Croakers (Teleostei: Sciaenidae) in Southeast Asian Waters

A broad-scale comparative phylogeographic and phylogenetic study of pennah croakers, mainly Pennahia anea, P. macrocephalus, and P. ovata was conducted to elucidate the mechanisms that may have driven the diversification of marine organisms in Southeast Asian waters. A total of 316 individuals from the three species, and an additional eight and six individuals of P. argentata and P. pawak were employed in this study. Two genetically divergent lineages each of P. argentata and P. anea (lineages L1 and L2) were respectively detected from the analyses based on mitochondrial cytochrome b gene data. Historical biogeography analysis with a multi-gene dataset revealed that Pennahia species most likely originated in the South China Sea and expanded into the eastern Indian Ocean, East China Sea, and northwestern Pacific Ocean through three separate range expansions. The main diversifications of Pennahia species occurred during Miocene and Pliocene periods, and the occurrences of lineage divergences within P. anea and P. argentata were during the Pleistocene, likely as a consequence of cyclical glaciations. The population expansions that occurred after the sea level rise might be the reason for the population homogeneity observed in P. macrocephalus and most P. anea L2 South China Sea populations. The structure observed between the two populations of P. ovata, and the restricted distributions of P. anea lineage L1 and P. ovata in the eastern Indian Ocean, might have been hampered by the northward flowing ocean current at the Malacca Strait and by the distribution of coral reefs or rocky bottoms. While our results support S. Ekman’s center-of-origin hypothesis taking place in the South China Sea, the Malacca Strait serving as the center of overlap is a supplementary postulation for explaining the present-day high diversity of pennah croakers centered in these waters.

Morphology and molecular phylogeny of Pauciconfibuloides amazonica gen. n. sp. n. (Platyhelminthes, Monogenoidea) parasitizing the Amazonian croaker Plagioscion squamosissimus

An integrative study was performed to understand the phylogenetic relationships of an undescribed, freshwater species of microcotylid parasitizing Plagioscion squamosissimus from the Amazon River Basin. Based on morphological and molecular analysis (18S rDNA and partial 28S rDNA genes), a new genus is proposed to accommodate this new species, Pauciconfibuloides amazonica gen. n. sp. n. The new genus is closely related to Protastomicrocotylinae and Pauciconfibula by sharing the vagina, male copulatory organ, and genital atrium all unarmed. However, Pauciconfibuloides gen. n. can be distinguished from those taxa by the prostatic system and position of the vaginal pore. Molecular phylogenetic inference suggests a sister relationship with species of Polylabris (Prostatomicrocotylinae), but to date, there are no available 18S or 28S rDNA sequences of Pauciconfibula to be compared. This is the first report of a microcotylid parasitizing a freshwater sciaenid from South America.

Chromosome-scale assembly and high-density genetic map of the yellow drum, Nibea albiflora

The yellow drum (Nibea albiflora) is an economically important sciaenid fish in East Asian countries. In this study, we sequenced and assembled a near-complete gynogenetic yellow drum genome. We generated 45.63 Gb of Illumina short-reads and 80.27 Gb of PacBio long-reads and assembled them into a 628.01-Mb genome with a contig N50 of 4.42 Mb. Twenty-four chromosomes with a scaffold N50 of 26.73 Mb were obtained using the Hi-C analysis. We predicted a set of 27,069 protein-coding genes, of which 1,581 and 2,583 were expanded and contracted gene families, respectively. The most expanded genes were categorised into the protein binding, zinc-ion binding and ATP binding functional pathways. We built a high-density genetic linkage map that spanned 4,300.2 cM with 24 linkage groups and a resolution of 0.69 cM. The high-quality reference genome and annotated profiles that we produced will not only increase our understanding of the genetic architecture of economic traits in the yellow drum, but also help us explore the evolution and unique biological characteristics of sciaenid fishes.

Characterization of the sex differentiation and gonadal development in small yellow croaker (Larimichthys polyactis) and its hybrid (L. polyactis ♀ × L. crocea ♂)

Interspecific hybridization has been considered as a possible approach to improve biological traits and has been applied in aquaculture practices. In the present study, artificial hybridization was carried out in the small yellow croaker (SYC; Larimichthys polyactis) ♀ × large yellow croaker (LYC; L. crocea) ♂ by artificial insemination, and the processes of sex differentiation and gonadal development in SYC and its hybrid were investigated under controlled conditions. Histological analysis of SYC larvae showed that migrating primordial germ cells (PGCs) were observed at 4 days post-hatching (dph), a genital ridge was formed on the dorsal side of the peritoneum at 6 dph, and a pair of primary gonads was first observed at 10 dph. Signs of the differentiated ovary and ovarian cavity were observed at 45 dph. However, some presumptive testes showed alterations in morphology, including an increase in the number of oocytes and an enhanced basophilia at 50 dph. These presumptive testes seemed to alter again, and numerous gonial cells were arranged in cyst-like groups with several degenerating oocytes that developed into residual body-like structures during 60-90 dph. Compared with SYC, the hybrid had a lower number of PGCs and showed retarded gonadal development at the early stage. Ovarian differentiation in the hybrid was observed at 50 dph, while testicular differentiation occurred at 60 dph. The presence of vitellogenic oocytes and spermatozoa at 360 dph in the hybrids suggested that hybrid individuals can undergo successful gametogenesis in females and males, respectively. Overall, the present results suggest that morphological sex differentiation occurred at 40 and 50 dph in SYC and its hybrid, respectively, both of which have normal gametogenesis. Moreover, some level of heterosis (hybrid vigor) occurred in the growth of the hybrid (total length and body weight) compared with that in the growth of SCY over time. Gonadal development of the hybrid was also found to be advanced at 360 dph. The present information will contribute to the potential use and management of these fish for aquaculture.

Recreated Ancestral Opsin Associated with Marine to Freshwater Croaker Invasion Reveals Kinetic and Spectral Adaptation

Rhodopsin, the light-sensitive visual pigment expressed in rod photoreceptors, is specialized for vision in dim-light environments. Aquatic environments are particularly challenging for vision due to the spectrally dependent attenuation of light, which can differ greatly in marine and freshwater systems. Among fish lineages that have successfully colonized freshwater habitats from ancestrally marine environments, croakers are known as highly visual benthic predators. In this study, we isolate rhodopsins from a diversity of freshwater and marine croakers and find that strong positive selection in rhodopsin is associated with a marine to freshwater transition in South American croakers. In order to determine if this is accompanied by significant shifts in visual abilities, we resurrected ancestral rhodopsin sequences and tested the experimental properties of ancestral pigments bracketing this transition using in vitro spectroscopic assays. We found the ancestral freshwater croaker rhodopsin is redshifted relative to its marine ancestor, with mutations that recapitulate ancestral amino acid changes along this transitional branch resulting in faster kinetics that are likely to be associated with more rapid dark adaptation. This could be advantageous in freshwater due to the redshifted spectrum and relatively narrow interface and frequent transitions between bright and dim-light environments. This study is the first to experimentally demonstrate that positively selected substitutions in ancestral visual pigments alter protein function to freshwater visual environments following a transition from an ancestrally marine state and provides insight into the molecular mechanisms underlying some of the physiological changes associated with this major habitat transition.

Chromosome-Level Genome Assembly and Annotation of a Sciaenid Fish, Argyrosomus japonicus

Argyrosomus japonicus is an economically and ecologically important fish species in the family Sciaenidae with a wide distribution in the world's oceans. Here, we report a high-quality, chromosome-level genome assembly of A. japonicus based on PacBio and Hi-C sequencing technology. A 673.7-Mb genome containing 282 contigs with an N50 length of 18.4 Mb was obtained based on PacBio long reads. These contigs were further ordered and clustered into 24 chromosome groups based on Hi-C data. In addition, a total of 217.2 Mb (32.24% of the assembled genome) of sequences were identified as repeat elements, and 23,730 protein-coding genes were predicted based on multiple approaches. More than 97% of BUSCO genes were identified in the A. japonicus genome. The high-quality genome assembled in this work not only provides a valuable genomic resource for future population genetics, conservation biology and selective breeding studies of A. japonicus but also lays a solid foundation for the study of Sciaenidae evolution.

The complete mitochondrial genome of Menticirrhus littoralis (Sciaenidae, Perciformes) and its phylogeny

We describe the mitochondrial genome of the Menticirrhus littoralis and infer the phylogenetic position of Menticirrhus in the family Sciaenidae. The genome contains 16,499 base pairs distributed in gene regions (13 protein-coding regions, 2 rRNAs and 22 tRNAs) and a control region (CR). Our phylogenetic analysis suggests, with strong statistical support, that Menticirrhus is a sister group of the other sciaenids.

Diversity, phylogeny, and historical biogeography of large-eye seabreams (Teleostei: Lethrinidae)

The large-eye seabreams or Monotaxinae is one of two subfamilies in the Lethrinidae, a family of perch-like coral reef fishes. Despite its widespread occurrence and its commercial interest in the tropical Indo-West Pacific (IWP), this subfamily has traditionally been considered a taxonomically difficult group. Based on 268 samples collected from all 15 known large-eye seabream species throughout their distribution ranges, we investigated the taxonomic diversity and phylogenetic relationships in the subfamily. From the results of multiple analyses on four gene markers, we confirmed the monophyly of all four genera in the subfamily (Gnathodentex, Gymnocranius, Monotaxis and Wattsia). We confirmed the occurrence of two species in the genus Monotaxis. We reported 15 delimited species within the most speciose genus Gymnocranius, four of which are potentially new species. The time-calibrated phylogenetic reconstruction enabled us to clarify the evolutionary history of the large-eye seabreams and to infer past patterns of species distribution. The most recent common ancestor to the Monotaxinae likely occurred in the central IWP ca. 32 million years ago. A burst of species diversification likely took place during the Mid- to Late Miocene, coinciding with tectonic change in the central IWP region. This gave rise to most extant lineages in Gymnocranius. The observed geographic distribution patterns in the subfamily most likely point to the central IWP as the area of origin and diversification. This was followed by multiple events of centrifugal range expansion towards either the Indian Ocean or the western Pacific Ocean, or both. Our results thus provide new support for S. Ekman's center-of-origin hypothesis.

DNA barcoding identifies three species of croakers (Pisces, Sciaenidae) in the ichthyoplankton of the High Paraná River

In the province of Misiones (Argentina), the filling of the Yacyretá Reservoir (Argentina-Paraguay) to its final dimensions in 2011 formed new aquatic ecosystem, e.g., Garupá Stream was converted into a subreservoir. Reports have been made in this stream of adult individuals and spawning of the Family Sciaenidae, excellent colonizers of modified environments. The larvae of this family are morphologically similar, particularly among Pachyurus and Plagioscion species, making taxonomic differentiation difficult. In the present work, sciaenidae larvae were characterized molecularly at the cytochrome c oxidase subunit I gene in order to determine which species use this environment for reproduction. Additionally, genetic distances, Barcode Index Number (BIN) and Automatic Barcode Gap Discovery method (ABGD) were estimated and phylogenetic trees were reconstructed. The results indicated the presence of Plagioscion ternetzi and Pachyurus bonariensis larvae, and for the first time in tributaries of the region, Plagioscion squamosissimus. The incorporation of P. bonariensis and P. squamosissimus to the faunistic assemblage of ichthyoplankton in the Garupá Stream supports better characterization of the species richness of this secondary watercourse modified by the Yacyretá Reservoir, and advancement in our understanding of use of this area for reproduction.

Habitat transitions alter the adaptive landscape and shape phenotypic evolution in needlefishes (Belonidae)

Habitat occupancy can have a profound influence on macroevolutionary dynamics, and a switch in major habitat type may alter the evolutionary trajectory of a lineage. In this study, we investigate how evolutionary transitions between marine and freshwater habitats affect macroevolutionary adaptive landscapes, using needlefishes (Belonidae) as a model system. We examined the evolution of body shape and size in marine and freshwater needlefishes and tested for phenotypic change in response to transitions between habitats. Using micro-computed tomographic (µCT) scanning and geometric morphometrics, we quantified body shape, size, and vertebral counts of 31 belonid species. We then examined the pattern and tempo of body shape and size evolution using phylogenetic comparative methods. Our results show that transitions from marine to freshwater habitats have altered the adaptive landscape for needlefishes and expanded morphospace relative to marine taxa. We provide further evidence that freshwater taxa attain reduced sizes either through dwarfism (as inferred from axial skeletal reduction) or through developmental truncation (as inferred from axial skeletal loss). We propose that transitions to freshwater habitats produce morphological novelty in response to novel prey resources and changes in locomotor demands. We find that repeated invasions of different habitats have prompted predictable changes in morphology.

Complete mitochondrial genome and the phylogenetic position of a new species, Johnius taiwanensis (Perciformes: Sciaenidae) from Chinese waters

In this study, the complete mitogenome of a new species, Johnius taiwanensis (Chao et al. 2019) was obtained. Its mitogenome is 18,451 bp in length, consisting of 37 genes with the typical gene order and direction of transcription in vertebrates. Gene rearrangement was found in J. taiwanensis. The overall nucleotide composition is: 24.2% A; 18.0% C; 21.1% G, and 36.7% T. Sizes of the 22 tRNA genes range from 66 to 75 bp. Two start codons (ATG and GTG) and three stop codons (TAG, AGA and TAA/TA/T) were detected in 13 protein-coding genes. In the Bayesian tree based on the complete mitogenomes of 26 species (including J. taiwanensis) from the family Sciaenidae, all nodes were strongly supported. The result shows that J. taiwanensis was placed as sister to the Trewavas croaker J. trewavasae of the same genus. The mechanism of gene rearrangement in the genus Johnius merits further investigation.

Evolution and losses of spines in slug caterpillars (Lepidoptera: Limacodidae)

Larvae of the cosmopolitan family Limacodidae, commonly known as "slug" caterpillars, are well known because of the widespread occurrence of spines with urticating properties, a morpho-chemical adaptive trait that has been demonstrated to protect the larvae from natural enemies. However, while most species are armed with rows of spines ("nettle" caterpillars), slug caterpillars are morphologically diverse with some species lacking spines and thus are nonstinging. It has been demonstrated that the evolution of spines in slug caterpillars may have a single origin and that this trait is possibly derived from nonstinging slug caterpillars, but these conclusions were based on limited sampling of mainly New World taxa; thus, the evolution of spines and other traits within the family remains unresolved. Here, we analyze morphological variation in slug caterpillars within an evolutionary framework to determine character evolution of spines with samples from Asia, Australia, North America, and South America. The phylogeny of the Limacodidae was reconstructed based on a multigene dataset comprising five molecular markers (5.6 Kbp: COI, 28S, 18S, EF-1α, and wingless) representing 45 species from 40 genera and eight outgroups. Based on this phylogeny, we infer that limacodids evolved from a common ancestor in which the larval type possessed spines, and then slug caterpillars without spines evolved independently multiple times in different continents. While larvae with spines are well adapted to avoiding generalist predators, our results imply that larvae without spines may be suited to different ecological niches. Systematic relationships of our dataset indicate six major lineages, several of which have not previously been identified.

Phylogenetic relationships of the species of Plagioscion Gill, 1861 (Eupercaria, Sciaenidae)

The genus PlagioscionGill, 1861 (Sciaenidae; Eupercaria) is currently composed of five valid species (P. squamosissimus, P. auratus, P. magdalenae, P. ternetzi and P. montei) widely distributed in South America. This study seeks to test the monophyly of Plagioscion and develope an hypothesis of phylogenetic relationships among the species of the genus, based on the analysis of 28 characters of external and internal morphology and behavior. The ingroup consists of the five species of Plagioscion. The outgroup was composed of eight species of the genera Ctenosciaena, Cynoscion, Isopisthus, Larimus, Macrodon and Pachyurus. Cladistic analysis yielded a single most parsimonious cladogram (L = 50, CI = 0.60 and RI = 0.72). The monophyly of genus Plagioscion was supported by the presence of five synapomorphies, corroborating previous studies. The single most parsimonious cladogram recovered the following hypothesis of relationships among the species of the genus: ((P. squamosissimus + P. ternetzi) (P. magdalenae (P. montei + P. magdalenae))). Comments about all characters are presented.

Near-complete genome assembly and annotation of the yellow drum (Nibea albiflora) provide insights into population and evolutionary characteristics of this species

Yellow drum (Nibea albiflora) is an important fish species in capture fishery and aquaculture in East Asia. We herein report the first and near-complete genome assembly of an ultra-homologous gynogenic female yellow drum using Illumina short sequencing reads. In summary, a total of 154.2 Gb of raw reads were generated via whole-genome sequencing and were assembled to 565.3 Mb genome with a contig N50 size of 50.3 kb and scaffold N50 size of 2.2 Mb (BUSCO completeness of 97.7%), accounting for 97.3%-98.6% of the estimated genome size of this fish. We further identified 22,448 genes using combined methods of ab initio prediction, RNAseq annotation, and protein homology searching, of which 21,614 (96.3%) were functionally annotated in NCBI nr, trEMBL, SwissProt, and KOG databases. We also investigated the nucleotide diversity (around 1/390) of aquacultured individuals and found the genetic diversity of the aquacultured population decreased due to inbreeding. Evolutionary analyses illustrated significantly expanded and extracted gene families, such as myosin and sodium: neurotransmitter symporter (SNF), could help explain swimming motility of yellow drum. The presented genome will be an important resource for future studies on population genetics, conservation, understanding of evolutionary history and genetic breeding of the yellow drum and other Nibea species.

Revision of Bairdiella (Sciaenidae: Perciformes) from the western South Atlantic, with insights into its diversity and biogeography

ABSTRACT The sciaenid genus Bairdiella comprises a group of relatively small fishes found in inshore waters and estuaries of the western Atlantic and eastern Pacific. Despite recent analyses of the phylogenetic relationships of Bairdiella, there has been no comprehensive revision of the alpha taxonomy of the species of the genus. Bairdiella ronchus from the western Atlantic, has a complex taxonomic history, with four junior synonyms recognized. Based on morphological and molecular evidence, this study indicates that B. ronchus represents a species complex. The species is therefore redescribed and its geographic range is redefined. Bairdiella veraecrucis, which is currently recognized as a junior synonym of B. ronchus, is revalidated, and a new species of the genus is described from the Atlantic coast of Brazil. Finally, inferences are made on the diversity and biogeography of the B. ronchus species complex.

Hybrid Sterility in Fish Caused by Mitotic Arrest of Primordial Germ Cells

Sterility in hybrid animals is widely known to be due to a cytological mechanism of aberrant homologous chromosome pairing during meiosis in hybrid germ cells. In this study, the gametes of four marine fish species belonging to the Sciaenid family were artificially fertilized, and germ cell development was examined at the cellular and molecular levels. One of the intergeneric hybrids had gonads that were testis-like in structure, small in size, and lacked germ cells. Specification of primordial germ cells (PGCs) and their migration toward genital ridges occurred normally in hybrid embryos, but these PGCs did not proliferate in the hybrid gonads. By germ cell transplantation assay, we showed that the gonadal microenvironment in hybrid recipients produced functional donor-derived gametes, suggesting that the germ cell-less phenotype was caused by cell autonomous proliferative defects of hybrid PGCs. This is the first evidence of mitotic arrest of germ cells causing hybrid sterility in animals.

Complete mitochondrial genome and the phylogenetic position of the blackmouth croaker Atrobucca nibe (Perciformes: Sciaenidae)

In this study, the complete mitogenome of the blackmouth croaker Atrobucca nibe was obtained. Its mitogenome is 16,842 bp in length, consisting of 37 genes with the typical gene order and direction of transcription in vertebrates. The overall nucleotide composition is: 27.2% A; 31.2% C; 16.4% G and 25.2% T. Sizes of the 22 tRNA genes range from 66 to 74 bp. One start codons (ATG) and three stop codons (TAG, AGA, and TAA/TA/T) were detected in 13 protein-coding genes. In the Bayesian tree based on the complete mitogenomes of 20 species (including A. nibe) from the family Sciaenidae, all nodes were strongly supported. The result suggested that A. nibe was subsequent to the group with genera Otolithes, Chrysochir, Megalonibea, Pennahia, Nibea, Dendrophysa, and Johnius.

Phylogeny of the subfamily Stelliferinae suggests speciation in Ophioscion Gill, 1863 (Sciaenidae: Perciformes) in the western South Atlantic

Phylogenies based on morphological and molecular data confirm the monophyly of the subfamily Stelliferinae; however, there is no consensus on the intergeneric and interspecific relationships in the group. Previous studies suggested the non-monophyly of Ophioscion and Stellifer, and possible cryptic species in Ophioscion punctatissimus. Therefore, we used mitochondrial (16S rDNA and COI) and nuclear (Rhodopsin, EGR1, and RAG1) regions to examine phylogenetic relationships among species of this subfamily. Our results confirmed the monophyly of Stelliferinae and supports the close relationship among Bardiella, Corvula and Odontoscion, which form a sister group to Stellifer and Ophioscion. Notwithstanding, all the results support the non-monophyly of Stellifer and Ophioscion and we suggest that a taxonomic revision should consider Ophioscion as a junior synonym of Stellifer. Moreover, O. punctatissimus was grouped into two clades, with the O. punctatissimus lineage I (LI) being closer to O. scierus from the eastern Pacific than to the O. punctatissimus lineage II (LII). The most recent common ancestor (TMRCA) for the O. scierus and O. punctatissimus LI and O. punctatissimus LII clade dates from 7.2 (HPD: 4.3-10.5) Ma, whereas TMRCA for the O. scierus and O. punctatissimus LI clade dates from 5.3 (HPD: 2.4-8.6) Ma, indicating that speciation processes may be related to the rise of the Isthmus of Panama. Phylogeographic analyses corroborate the hypothesis of speciation in O. punctatissimus. These results suggest that lineages of O. punctatissimus originated from distinct ancestors and, by morphological similarity, were considered the same taxon. A taxonomic revision should be performed to validate the species status of such lineages.

Fish DNA barcoding around large marine infrastructure for improved biodiversity assessment and monitoring

Accurate species-level identification is pivotal for environmental assessments and monitoring. The PERU LNG terminal is composed of large marine infrastructure located on the central coast of Peru. Since construction, taxonomically challenging species such as drum fishes (Sciaenidae) have been attracted to the new hard-bottom habitat. We conducted a DNA barcoding study to investigate fish diversity and constructed a DNA barcode reference library. We examined 56 vouchered specimens and identified 24 unique species. Intra- and interspecific divergence estimates ranged between 0 and 0.64% and 11 and 35.5%, respectively. We assessed the efficiency of the reference library to identify 29 non-vouchered specimens. We had 82.5% efficiency by using both our reference library (n = 17) and GenBank (n = 24). We highlight the importance of implementing molecular barcoding for complementing biodiversity assessments in marine environments. This study represents a first step towards generating a comprehensive DNA barcode reference library for marine fishes in Peru.

Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity

We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that loss of the fresher-water historic salinity regime could alter the adaptive factors maintaining distinction between the broadly distributed Gulf-endemic Colpichthys regis and the narrowly restricted Delta-endemic Colpichthys hubbsi, the species that experienced dramatic environmental change. In this altered environmental context, these long-isolated species (as revealed by Cytochrome b sequences) show genotypic (RAG1, microsatellites) evidence of active hybridization where the species ranges abut, as well as directional introgression from C. regis into the range center of C. hubbsi. Bayesian group assignment (STRUCTURE) on six microsatellite loci and multivariate analyses (DAPC) on both microsatellites and phenotypic data further support substantial recent admixture between the sister species. Although we find no evidence for recent population decline in C. hubbsi based on mitochondrial sequence, introgression may be placing an ancient ecological species at risk of extinction. Such introgressive extinction risk should also pertain to other ecological species historically sustained by the now changing Delta environment. More broadly, salinity gradient associated ecological speciation is evident in silverside species pairs in many estuarine systems around the world. Ecological species pairs among other taxa in such systems are likely poorly understood or cryptic. As water extraction accelerates in river systems worldwide, salinity gradients will necessarily be altered, impacting many more estuary and delta systems. Such alteration of habitats will place biodiversity at risk not only from direct effects of habitat destruction, but also from the potential for the breakdown of ecological species. Thus, evolutionary response to the anthropogenic alteration of salinity gradients in estuaries merits investigation as the number of impacted systems increases around the globe, permitting parallel study of multiple systems, while also permitting a conservation management response to help preserve this little championed component of biodiversity.

Comparative cytogenetics in three Sciaenid species (Teleostei, Perciformes): evidence of interspecific chromosomal diversification

Background

Species belonging to the Sciaenidae family present a karyotype composed by 48 acrocentric chromosomes and are thus considered a striking example of chromosomal conservation. In this family, three species are extensively studied including Larimichthys crocea, Larimichthys polyactis and Nibea albiflora due to their importance in fishery and aquaculture in East Asia. Despite abundant data of population genetics available for some of them, cytogenetic information on these species is still scarce and obtained by conventional cytogenetic protocols. Therefore, a more detailed cytogenomic investigation was performed in these species to analyze their karyotype differentiation using conventional staining techniques and fluorescence in situ hybridization to map several repetitive DNAs.

Results

The three species showed a slight karyotype differentiation with 4sm + 2st + 42a in L. polyactis, 20st + 28a in L. crocea and 48a in N. albiflora. Additionally, the mapping of repetitive sequences further revealed a number of interspecific differences among them. Particularly, 18S and 5S rDNA sites showed syntenic arrangements in N. albiflora and non-syntenic arrangements in both Larimichthys species. The microsatellites (CA)₁₅ and (GA)₁₅ showed conspicuous terminal clusters in some chromosomes of all species. On the other hand, (CGG)₁₀ repeats, Rex6 elements and U2 snRNA displayed a scattered distribution on the chromosomes.

Conclusions

Although the three Sciaenid species examined displayed a general pattern of karyotypic conservatism, we explored chromosomal diversification among them. The diversificated karyotypic macrostructure is followed by intergeneric evolutionary diversification of the repetitive sequences. The data indicate some degree of intergeneric evolutionary diversification at chromosomal level, and suggest the evolutionary dynamics among Sciaenid species, higher than previously thought. The present cytogenetic data provide new insight into the chromosomal diversification in Sciaenidae, and contribute to inferring the chromosomal rearrangements and trends of karyotype evolution in this fish group.

Diplectanids (Monogenea) parasitic on sciaenid fish from Peru with the proposal of Pseudorhamnocercoides n. gen., the description of Rhamnocercus dominguesi n. sp. and the redescription of Rhamnocercoides menticirrhi Luque and Iannacone, 1991

Rhamnocercoides menticirrhi Luque and Iannacone, 1991 is redescribed from newly collected material of snakehead kingcroaker Menticirrhus ophicephalus (Jenyns, 1840) from Peru, and as a result of this redescription, the diagnosis of Rhamnocercoides is emended. Rhamnocercus dominguesi n. sp. is described from the Peruvian banded croaker Paralonchurus peruanus (Steindachner, 1875). It differs from congeneric species mainly in the morphology of the male copulatory organ (with distal and proximal portion of the external tube expanded and distal portion of the internal tube uncovered by external tube) and the number of peduncular spines (18-22, arranged in 2 longitudinal rows). Pseudorhamnocercoides n. gen. is proposed for species with two longitudinal rows of peduncular spines with anterior and posterior roots, two longitudinal rows of acicular spines associated with peduncular spines, a medial constriction in the ventral bar and more than six haptoral accessory spines at level of the ventral bar with fan-like distal extremity. Rhamnocercoides stichospinus (Seamster and Monaco, 1956) is transferred to Pseudorhamnocercoides n. gen as Pseudorhamnocercoides stichospinus (Seamster and Monaco, 1956) n. comb (assigned as type species).

Three monogeneans parasitic on marine sciaenid fish from Peru including description of Cynoscionicola veranoi n. sp. (Microcotylidae), and redescription of C. americanus Tantaleán, Martínez and Escalante, 1987 and Hargicotyle sciaenae Oliva and Luque, 1989 (Diclidophoridae)

Cynoscionicola veranoi n. sp. (Monogenea: Microcotylidae) is described based on specimens collected from the gills of lorna drum Sciaena deliciosa (Tschudi, 1846) (Sciaenidae) from Peru. The new species can be differentiated from the other congeneric species by the combination of the following characteristics: (1) haptor with two types of clamps, (2) number and shape of the spines in anterolateral pouches of genital atrium (10-11 curved spines and 3-4 short and bifid spines with a knob in each lateral margin), (3) number and shape of the spines in posterolateral pouches of genital atrium (13-18 bifid spines), (4) 4-6 small spherical unarmed pouches in the genital atrium, and (5) 10-15 testes. In addition, a redescription of Cynoscionicola americanus Tantaleán, Martínez and Escalante, 1987 and Hargicotyle sciaenae Oliva and Luque, 1989 (Diclidophoridae) based on examination of type material and newly collected specimens from snakehead kingcroaker Menticirrhus ophicephalus (Jenyns, 1840) and S. deliciosa (type hosts), respectively, are provided herein.

Complete mitochondrial genome and the phylogenetic position of the Pawak croaker Pennahia pawak (Perciformes: Sciaenidae)

In this study, the complete mitogenome of the Pawak croaker Pennahia pawak was first determined. This mitogenome is 16,408 bp in length, and consists of 37 genes with the typical gene order and direction of transcription in vertebrates. The overall nucleotide composition is: 27.7% A, 29.5% C, 15.9% G, and 26.9% T. Sizes of the 22 tRNA genes range from 66 to 75 bp. One start codons (ATG) and two stop codons (AGA and TAA/TA/T) were detected in 13 protein-coding genes. In the Bayesian tree based on the complete mitogenomes of 17 species (including P. pawak) from the family Sciaenidae, all nodes were strongly supported. The phylogenetic results suggested that P. pawak has the closest relationship to the silver croaker P. argentata, a species from the same genus.

Molecular exploration of hidden diversity in the Indo-West Pacific sciaenid clade

The family Sciaenidae, known as croakers or drums, is one of the largest perciform fish families. A recent multi-gene based study investigating the phylogeny and biogeography of global sciaenids revealed that the origin and early diversification of this family occurred in tropical America during the Late Oligocene-Early Miocene before undergoing range expansions to other seas including the Indo-West Pacific, where high species richness is observed. Despite this clarification of the overall evolutionary history of the family, knowledge of the taxonomy and phylogeny of sciaenid genera endemic to the Indo-West Pacific is still limited due to lack of a thorough survey of all taxa. In this study, we used DNA-based approaches to investigate the evolutionary relationships, to explore the species diversity, and to elucidate the taxonomic status of sciaenid species/genera within the Indo-West Pacific clade. Three datasets were herein built for the above objectives: the combined dataset (248 samples from 45 currently recognized species) from one nuclear gene (RAG1) and one mitochondrial gene (COI); the dataset with only RAG1 gene sequences (245 samples from 44 currently recognized species); and the dataset with only COI gene sequences (308 samples from 51 currently recognized species). The latter was primarily used for our biodiversity exploration with two different species delimitation methods (Automatic Barcode Gap Discovery, ABGD and Generalized Mixed Yule Coalescent, GMYC). The results were further evaluated with help of four supplementary criteria for species delimitation (genetic similarity, monophyly inferred from individual gene and combined data trees, geographic distribution, and morphology). Our final results confirmed the validity of 32 currently recognized species and identified several potential new species waiting for formal descriptions. We also reexamined the taxonomic status of the genera, Larimichthys, Nibea, Protonibea and Megalonibea, and suggested a revision of Nibea and proposed a new genus Pseudolarimichthys.

Complete mitochondrial genome and the phylogenetic position of the tigertooth croaker Otolithes ruber (Perciformes: Sciaenidae)

In this study, the complete mitogenome of the tigertooth croaker Otolithes ruber was first determined. This mitogenome is 16,589 bp in length, and consists of 37 genes with the typical gene order and direction of transcription in vertebrates. The overall nucleotide composition is: 27.4% A; 29.1% C; 16.1% G and 27.4% T. Sizes of the 22 tRNA genes range from 66 to 74 bp. Four start codons (ACG, CTG, GTG and ATG) and three stop (AGA, TAG and TAA/TA/T) codons were detected in 13 protein-coding genes. In the Bayesian treebased on the complete mitogenomes of 18 species (including O. ruber) from the family Sciaenidae, all nodes were strongly supported. The phylogenetic results suggested that O. ruber was closed to the black-spotted croaker Protonibea diacanthus.

Proposed synonymy for Micropogonias altipinnis (Günther 1864), Micropogonias ectenes (Jordan & Gilbert 1882), and Micropogonias megalops (Gilbert 1890)

Within the Sciaenidae family, the genus Micropogonias is composed of three recognized species along the Pacific coast of Mexico: Micropogonias altipinnis, M. ectenes, and M. megalops. These species exhibit overlapping diagnostic characters, which make species identification difficult. This study ties morphological differences (meristic, morphometry of body, and otolith) with DNA sequences (CO1 and 16S fractions of mtDNA and 28S of nDNA) among Micropogonias species in the Pacific. Meristic analysis showed a latitudinal variation among the three species in the number of rays, the number of gill rakers, and length of the longest spine of the dorsal fin. Discriminant analysis of morphometric characters (body and otolith) showed three morphological entities (p < 0.001). However, the mean genetic divergences among the three species with partial sequences of mtDNA (CO1 and 16S), and nuclear (28S) were lower than those reported at the interspecific level (>2%). Genetic results suggest that the three species are one species and that the differences in meristics and morphometry could be the result of phenotypic plasticity or incipient speciation. In this sense, M. ectenes and M. megalops are proposed as junior synonyms of M. altipinnis.

New case of lateral asymmetry in fishes: A new subfamily, genus and species of deep water clingfishes from Papua New Guinea, western Pacific Ocean

The unusual clingfish Protogobiesox asymmetricus n. gen, n. sp. is described on the basis of four specimens collected in deep water off the north coast of Papua New Guinea in 2012. The species is characterized by its 9-10 dorsal rays, 8 anal rays, 17-24 pectoral-fin rays, 15 principal caudal-fin rays, 3 gills, third arch with 3 gill rakers, 34-35 total vertebrae, with asymmetrical lateral bending starting behind the skull, bent at an angle of 85°-92°; skull asymmetrical in frontal view; skin naked, surface of head and body without striae; disc without adhesive papillae. A new subfamily Protogobiesocinae is described for this species and Lepadicyathus mendeleevi Prokofiev, 2005, which is redescribed. The new subfamily is compared within the family; keys to the subfamilies of Gobiesocidae and the species within the new subfamily are presented; its phylogenetic relationship to other gobiesocids is inferred based on a multi-locus DNA dataset.

Complete mitochondrial genome and the phylogenetic position of the bighead pennah croaker Pennahia macrocephalus (Perciformes: Sciaenidae)

The complete mitogenome of the bighead pennah croaker Pennahia microcephalus was first determined in this study. It is 16,508 bp in length with the typical gene order and transcriptional direction in vertebrates containing 37 genes. The overall nucleotide composition is 27.5% A; 31.2% C; 16.0% G, and 25.3% T. The sizes of the 22 tRNA genes range from 68 to 75 bp. Two start (ATC and ATG) and three stop (AGA, TAG, and TAA/TA/T) codons were found in the protein-coding genes. In the Bayesian tree, all nodes were strongly supported based on the complete mitogenomes of 16 species from the family Sciaenidae. The phylogenetic results suggested P. macrocephalus has the closest relationship to the silver croaker P. argentata, a species from the same genus.

Influence of cladogenesis on feeding structures in drums (Teleostei: Sciaenidae)

Drums (family Sciaenidae) are common in tropical to temperate coastal and estuarine habitats worldwide and present a broad spectrum of morphological diversity. The anatomical variation in this family is particularly evident in their feeding apparatus, which may reflect the partitioning of adult foraging habitats. Adult and early life history stage sciaenids may display ecomorphological patterns in oral and pharyngeal jaw elements but because sciaenids are hierarchically related, the morphological variation of the feeding apparatus cannot be analyzed as independent data. Morphological patterns have been identified in three sciaenid genera from the Chesapeake Bay but it is not known if these patterns are present in other genera of the family and if such patterns are constrained by phylogenetic history. In this study, phylogenetic comparative methods were applied to two sets of oral jaw data obtained from growth series of 11 species of cleared and double-stained Chesapeake Bay sciaenids and alcohol-preserved museum specimens representing 65 of the 66 recognized genera to determine the magnitude of phylogenetic dependence present in the structure of the oral jaws using a recent molecular phylogeny of the family. Pagel's lambda, a measure of phylogenetic signal, was low for pelagic sciaenids in premaxilla, lower jaw, and ascending process lengths, indicating influence of selective forces on the condition of these traits. Conversely, for benthic sciaenids, phylogenetic signal was high for lower jaw and ascending process lengths, indicating significant phylogenetic constraint for their condition in these taxa. Pagel's lambda was intermediate for premaxilla length in benthic sciaenids, suggesting that the length of the premaxilla is influenced by a mix of selective forces and phylogenetic constraint. Although the ecomorphological patterns identified in the oral jaws of scaienids are not entirely free of phylogenetic dependence, selective forces related to foraging are likely driving the evolution of these structures.

The historical biogeography of groupers: Clade diversification patterns and processes

Groupers (family Epinephelidae) are a clade of species-rich, biologically diverse reef fishes. Given their ecological variability and widespread distribution across ocean basins, it is important to scrutinize their evolutionary history that underlies present day distributions. This study investigated the patterns and processes by which grouper biodiversity has been generated and what factors have influenced their present day distributions. We reconstructed a robust, time-calibrated molecular phylogeny of Epinephelidae with comprehensive (∼87%) species sampling, whereby diversification rates were estimated and ancestral ranges were reconstructed. Our results indicate that groupers originated in what is now the East Atlantic during the mid-Eocene and diverged successively to form six strongly supported main clades. These clades differ in age (late Oligocene to mid-Miocene), geographic origin (West Atlantic to West Indo-Pacific) and temporal-spatial diversification pattern, ranging from constant rates of diversification to episodes of rapid radiation. Overall, divergence within certain biogeographic regions was most prevalent in groupers, while vicariant divergences were more common in Tropical Atlantic and East Pacific groupers. Our findings reveal that both biological and geographical factors have driven grouper diversification. They also underscore the importance of scrutinizing group-specific patterns to better understand reef fish evolution.

Grunt variation in the oyster toadfish Opsanus tau: effect of size and sex

As in insects, frogs and birds, vocal activity in fishes tends to be more developed in males than in females, and sonic swimbladder muscles may be sexually dimorphic, i.e., either larger in males or present only in males. Male oyster toadfish Opsanus tau L produce a long duration, tonal boatwhistle advertisement call, and both sexes grunt, a short duration more pulsatile agonistic call. Sonic muscles are present in both sexes but larger in males. We tested the hypothesis that males would call more than females by inducing grunts in toadfish of various sizes held in a net and determined incidence of calling and developmental changes in grunt parameters. A small number of fish were recorded twice to examine call repeatability. Both sexes were equally likely to grunt, and grunt parameters (sound pressure level (SPL), individual range in SPL, number of grunts, and fundamental frequency) were similar in both sexes. SPL increased with fish size before leveling off in fish >200 g, and fundamental frequency and other parameters did not change with fish size. Number of grunts in a train, grunt duration and inter-grunt interval were highly variable in fish recorded twice suggesting that grunt parameters reflect internal motivation rather than different messages. Grunt production may explain the presence of well-developed sonic muscles in females and suggests that females have an active but unexplored vocal life.