Cryptic diversity and venom glands in Western atlantic clingfishes of the genus acyrtus (Teleostei: Gobiesocidae)

A new cryptic species of Imparfinis (Siluriformes: Heptapteridae) from the Orinoco River basin, revealed by an iterative approach

An iterative analysis of Imparfinis, combining phylogenetic analysis based on cytochrome oxidase gene and multivariate morphometrics, revealed a new cryptic species from the Andean tributaries of the Orinoco River basin, which is described here. The new species is sister to a clade constituted by Imparfinis hasemani and Imparfinis pijpersi, both from the river basins of the Guiana Shield, being also the most geographically proximate species. Nonetheless, the new species is most similar in general appearance to Imparfinis guttatus from the Madeira and Paraguay River drainages, being almost undistinguishable by conventional characters of external morphology, differing only by morphometric attributes overall. The new species can be distinguished from the remaining congeners by a unique combination of characters, including lower lobe of caudal fin darker than upper lobe, maxillary barbel reaching or surpassing pelvic-fin insertion, 12-15 gill rakers on first gill arch, 40-42 total vertebrae and 9-10 ribs. The new species constitutes the only representative from the Orinoco River basin belonging to Imparfinis sensu stricto.

Recent dispersal and diversification within the clingfish genus Acyrtus (Actinopterygii: Gobiesocidae), with the description of a new western Atlantic species

Abstract The genus Acyrtus (Gobiesocidae) is represented by four valid species distributed in the western Atlantic, and a recently described fifth species from the eastern Pacific. Here, we describe a new species endemic to Trindade Island, Brazil, and provide the first phylogenetic inference for the genus including all representatives. The new species can be distinguished from all its congeners by meristic and morphometric characters, as well as genetic differences. It presents low genetic diversity and, contrarily to other Trindade Island endemic fishes, shows no evidence of recent population growth. Our phylogeny reveals cryptic species and the paraphyletic nature of Acyrtus, which included Arcos nudus (western Atlantic) in a clade that separated from Arcos erythrops (tropical eastern Pacific) around 20 Mya. The three species found in the Brazilian Province, including one that remains undescribed, form a monophyletic clade which colonized the western South Atlantic around 2.6 Mya. Our study suggests that Arcos nudus should be placed in Acyrtus, and that the relationships among the closely-related Gobiesocidae genera Acyrtus (mostly from the Atlantic Ocean) and Arcos (from the Pacific Ocean) need further investigation.

A new species of the genus Acyrtus on the eastern Pacific: A cornerstone for the evolution and biogeography of the genus

The genus Acyrtus Schultz, 1944 currently includes four species distributed in the western Atlantic (WA), three occurring from the Bahamas to the southern Caribbean, and one endemic to the Fernando de Noronha Archipelago in north-east Brazil. We describe a new species of Acyrtus based on morphology and genetics from several individuals caught at artificial hard substrates deployed between 10 and 16 m deep at Malpelo Island, Colombian Pacific. The Malpelo clingfish, Acyrtus arturo new species, differs from all its WA congeners by a combination of morphology, meristics and genetics. This species is unique within Acyrtus in having the greatest number of caudal rays (12-13). It can also be distinguished by the greater body height (19.8-27.8% standard length), its longer disc (34.0-39.1% standard length) and the greater distance between anus and disc (13.9-18.1% standard length). A. arturo sp. nov. is the first Acyrtus so far recorded from the eastern Pacific and adds to the already high number of fishes endemic to Colombia's remote oceanic territory of Malpelo.

A multi-locus approach to elucidating the evolutionary history of the clingfish Tomicodon petersii (Gobiesocidae) in the Tropical Eastern Pacific

Marine species that are widely distributed in the Tropical Eastern Pacific (TEP) has served as a model for studying biogeographic patterns resulting from the effects of intraregional habitat discontinuities and oceanographic processes on the diversification and evolution of cryptobenthic reef fishes. Tomicodon petersii, a clingfish (Gobiesocidae) endemic to the TEP, is found on very shallow rocky reefs from central Mexico to northern Peru, and in the Cocos and Galapagos islands. We evaluated the effect of likely biogeographic barriers in different parts of the TEP on the diversification process of this species. We used one mitochondrial and three nuclear DNA markers from 112 individuals collected across the distribution range of T. petersii. Our phylogenetic results showed the samples constituted a monophyletic group, with three well-supported, allopatric subgroups: in the Mexican province, the Panamic province (from El Salvador to Ecuador), and the Galapagos Islands. The split between the Mexican and more southerly clades was estimated to occur at the end of the Miocene ca. 5.74 Mya, and the subsequent cladogenetic event separating the Galapagos population from the Panamic population at the junction of the Pliocene and Pleistocene, ca. 2.85 Mya. The species tree, Bayesian species delimitation tests (BPP), STACEY, and substantial genetic distances separating these three populations indicate that these three independent evolutionary units likely include two unnamed species. The cladogenetic events that promoted the formation of those genetically differentiated groups are consistent with disruptive effects on gene flow of habitat discontinuities and oceanographic processes along the mainland shoreline in the TEP and of ocean-island isolation, in conjunction with the species intrinsic life-history characteristics.

Unravelling the taxonomy of an interstitial fish radiation: Three new species of Gouania (Teleostei: Gobiesocidae) from the Mediterranean Sea and redescriptions of G. willdenowi and G. pigra

The clingfish (Gobiesocidae) genus Gouania Nardo, 1833 is endemic to the Mediterranean Sea and inhabits, unlike any other vertebrate species in Europe, the harsh intertidal environment of gravel beaches. Following up on a previous phylogenetic study, we revise the diversity and taxonomy of this genus by analysing a comprehensive set of morphological (meristics, morphometrics, microcomputed tomography imaging), geographical and genetic (DNA-barcoding) data. We provide descriptions of three new species, G. adriatica sp. nov., G. orientalis sp. nov. and G. hofrichteri sp. nov., as well as redescriptions of G. willdenowi (Risso, 1810) and G. pigra (Nardo, 1827) and assign neotypes for the latter two species. In addition to elucidating the complex taxonomic situation of Gouania, we discuss the potential of this enigmatic clingfish genus for further ecological, evolutionary and biodiversity studies that might unravel even more diversity in this unique Mediterranean fish radiation.

A new genus and two new species of miniature clingfishes from temperate southern Australia (Teleostei, Gobiesocidae)

A new genus and two new species of miniature clingfishes are described based on specimens collected from dense stands of macroalgae in intertidal and shallow subtidal areas along the coast of southern Australia. The new genus, Barryichthys, is distinguished from other genera of the Gobiesocidae by unique features of the adhesive disc, including elongate papillae in adhesive disc regions A and B, the reduction and/or loss of several elements of the cephalic lateral line canals, the lower gill arch skeleton, and the neurocranium, and by having two distinct types of pectoral-fin rays. Barryichthyshutchinsi is described based on 19 specimens (12.4–18.7 mm SL) from Western Australia and South Australia. Barryichthysalgicola is described based on 22 specimens (9.0–21.0 mm SL) from Victoria, New South Wales and Tasmania. The new species are distinguished from each other by characters of body and head shape, vertebral counts, and aspects of live colour pattern. The new genus shares several characters in common with Parvicrepis, another genus of miniature gobiesocids from southern Australia that also inhabits macroalgae habitats. The many reductions and novel characters of Barryichthys are discussed within the context of miniaturisation.

A new genus and species of clingfish from the Rangitāhua Kermadec Islands of New Zealand (Teleostei, Gobiesocidae)

Flexorincus, new genus and species, is described from 15 specimens (14.0–27.2 mm SL) collected from shallow (0–9 meters) intertidal and sub-tidal waters of the Rangitāhua Kermadec Islands, New Zealand. The new taxon is distinguished from all other members of the Gobiesocidae by a combination of characters, including a heterodont dentition comprising both conical and distinct incisiviform teeth that are laterally compressed with a strongly recurved cusp, an oval-shaped opening between premaxillae, a double adhesive disc with a well-developed articulation between basipterygia and ventral postcleithra, and many reductions in the cephalic lateral line canal system. The new taxon is tentatively placed within the subfamily Diplocrepinae but shares a number of characteristics of the oral jaws and the adhesive disc skeleton with certain members of the Aspasminae and Diademichthyinae.

The hidden half: ecology and evolution of cryptobenthic fishes on coral reefs

Teleost fishes are the most diverse group of vertebrates on Earth. On tropical coral reefs, their species richness exceeds 6000 species; one tenth of total vertebrate biodiversity. A large proportion of this diversity is composed of cryptobenthic reef fishes (CRFs): bottom-dwelling, morphologically or behaviourally cryptic species typically less than 50 mm in length. Yet, despite their diversity and abundance, these fishes are both poorly defined and understood. Herein we provide a new quantitative definition and synthesise current knowledge on the diversity, distribution and life history of CRFs. First, we use size distributions within families to define 17 core CRF families as characterised by the high prevalence (>10%) of small-bodied species (<50 mm). This stands in strong contrast to 42 families of large reef fishes, in which virtually no small-bodied species have evolved. We posit that small body size has allowed CRFs to diversify at extremely high rates, primarily by allowing for fine partitioning of microhabitats and facilitation of allopatric reproductive isolation; yet, we are far from understanding and documenting the biodiversity of CRFs. Using rates of description since 1758, we predict that approximately 30 new species of cryptobenthic species will be described per year until 2050 (approximately twice the annual rate compared to large fishes). Furthermore, we predict that by the year 2031, more than half of the described coral reef fish biodiversity will consist of CRFs. These fishes are the 'hidden half' of vertebrate biodiversity on coral reefs. Notably, global geographic coverage and spatial resolution of quantitative data on CRF communities is uniformly poor, which further emphasises the remarkable reservoir of biodiversity that is yet to be discovered. Although small body size may have enabled extensive diversification within CRF families, small size also comes with a suite of ecological challenges that affect fishes' capacities to feed, survive and reproduce; we identify a range of life-history adaptations that have enabled CRFs to overcome these limitations. In turn, these adaptations bestow a unique socio-ecological role on CRFs, which includes a key role in coral reef trophodynamics by cycling trophic energy provided by microscopic prey to larger consumers. Although small in body size, the ecology and evolutionary history of CRFs may make them a critical component of coral-reef food webs; yet our review also shows that these fishes are highly susceptible to a variety of anthropogenic disturbances. Understanding the consequences of these changes for CRFs and coral reef ecosystems will require us to shed more light on this frequently overlooked but highly diverse and abundant guild of coral reef fishes.

A new species of sea urchin associating clingfish of the genus Dellichthys from New Zealand (Teleostei, Gobiesocidae)

A new species of clingfish, Dellichthys trnskiisp. n. is described on the basis of 27 specimens, 11.9-46.0 mm SL, collected from intertidal and shallow coastal waters of New Zealand. It is distinguished from its only congener, D. morelandi Briggs, 1955 by characters of the cephalic sensory system and oral jaws, snout shape, and colouration in life. A rediagnosis is provided for D. morelandi, which is shown to exhibit sexual dimorphism in snout shape.

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.

Integrative approach revises the frequently misidentified species of Sardinella (Clupeidae) of the Indo-West Pacific Ocean

To deal with the difficulties of species differentiation and delimitation among the commercially important sardines from the genus Sardinella, an integrative approach was adopted, incorporating traditional taxonomy with four DNA markers (coI, cytb, 16s and nuclear rag2). Combining these methodologies has enabled a thorough re-description of three of the most common species of Sardinella of the Indo-west Pacific Ocean: white sardinella Sardinella albella, fringescale sardinella Sardinella fimbriata and the goldstripe sardinella Sardinella gibbosa, as well as a description of a new species, Gon's sardinella Sardinella goni, from the island of Boracay, Philippines. In addition, extensive widespread sampling of S. gibbosa reveals a significant genetic separation between the populations from the western Indian Ocean and the west Pacific Ocean, despite no supporting morphological differentiation. An updated morphological key of the species of Sardinella of the Indo-west Pacific Ocean is also provided in order to minimize future misidentifications within these economically important taxa. Finally, the genetic and morphological variabilities within and between the investigated species are used to discuss their biogeographical distribution and possible processes of speciation.