Species boundaries in the Himantura uarnak species complex (Myliobatiformes: Dasyatidae)

Integrative species delimitation in the common ophiuroid Ophiothrix angulata (Echinodermata: Ophiuroidea): insights from COI, ITS2, arm coloration, and geometric morphometrics

Ophiothrix angulata (Say, 1825) is one of the most common and well-known ophiuroids in the Western Atlantic, with a wide geographic and bathymetric range. The taxonomy of this species has been controversial for a century because of its high morphological variability. Here we integrate information from DNA sequence data, color patterns, and geometric morphometrics to assess species delimitation and geographic differentiation in O. angulata. We found three deeply divergent mtDNA-COI clades (K2P 17.0-27.9%). ITS2 nuclear gene and geometric morphometrics of dorsal and ventral arm plates differentiate one of these lineages, as do integrative species delineation analyses, making this a confirmed candidate species.

Seasonal changes characterise the shark and ray assemblages in a subtropical shallow sandy habitat in the iSimangaliso Wetland Park, South Africa

Understanding how environmental drivers influence shark and ray spatial and temporal patterns can provide crucial knowledge for their evidence-based protection and long-term monitoring. However, information on which drivers of variation are most important for elasmobranch communities on soft sediments is limited. Using baited remote underwater stereo-video systems (stereo-BRUVs), we investigated how seasonal and environmental variables affected the elasmobranchs of the iSimangaliso Wetland Park marine protected area (MPA) in South Africa (SA). In total, 11 species were identified from 48 sites between 12 m and 33 m water depth in a sandy habitat. While species richness was similar across seasons, the total abundance of elasmobranchs recorded was higher in winter than summer. The species assemblage composition varied significantly between seasons, with the Human's whaler shark Carcharhinus humani prevalent in summer and the Critically Endangered whitespotted wedgefish Rhynchobatus djiddensis more abundant during winter. Most species were sighted throughout the entire depth range, but rays were more common in shallower waters (< 25 m depth), while C. humani and R. djiddensis were more common in the deeper depth zone of this study. This research provides baseline information about this previously unexplored sandy habitat for elasmobranchs in a site of regional and global significance. Records of species of conservation concern in the sampling area highlight the importance of protecting sand environments within an MPA.

To Be, or Not to Be: That Is the Hamletic Question of Cryptic Evolution in the Eastern Atlantic and Mediterranean Raja miraletus Species Complex

Despite a high species diversity, skates (Rajiformes) exhibit remarkably conservative morphology and ecology. Limited trait variations occur within and between species, and cryptic species have been reported among sister and non-sister taxa, suggesting that species complexes may be subject to stabilising selection. Three sibling species are currently recognised in the Raja miraletus complex: (i) R. miraletus occurring along the Portuguese and Mediterranean coasts, (ii) R. parva in the Central-Eastern Atlantic off West Africa and (iii) R. ocellifera in the Western Indian Ocean off South Africa. In the present study, the genetic variation at mitochondrial and nuclear markers was estimated in the species complex by analysing 323 individuals sampled across most of its geographical distribution area to test the hypothesis that restricted gene flow and genetic divergence within species reflect known climate and bio-oceanographic discontinuities. Our results support previous morphological studies and confirm the known taxonomic boundaries of the three recognised species. In addition, we identified multiple weakly differentiated clades in the Northeastern Atlantic Ocean and Mediterranean, at least two additional cryptic taxa off Senegal and Angola, a pronounced differentiation of ancient South African clades. The hidden genetic structure presented here may represent a valuable support to species' conservation action plans.

Eutetrarhynchus pacificus n. sp. (Cestoda: Trypanorhyncha) from Raja inornata Jordan & Gilbert (Batoidea: Rajiformes) off the coast of California with comments on congeners

Eutetrarhynchus pacificus n. sp. is described from the spiral valve of Raja inornata Jordan & Gilbert off the coast of California, USA. The new species is distinguished from E. ruficollis (Eysenhardt, 1829) and E. leucomelanus (Shipley & Hornell, 1906) in having acraspedote rather than craspedote segments and a saccate rather than a branched uterus. It is distinguished from E. platycephali Palm, 2004 in lacking an enlarged hook in the eighth row of the basal armature and from E. beveridgei Schaeffner, 2013, which has a basal swelling and a distinctive basal armature. A partial redescription of E. ruficollis, the type-species of the genus, is provided based on available museum specimens, highlighting the need for a comprehensive redescription of this species to better define the characteristics of the genus. The presence of an undescribed species in museum collections is also noted. Based on the 28S ribosomal gene, the new species clustered with Dollfusiella in a molecular phylogenetic tree. The delimitation of Eutetrarhynchus and its relationship with Dollfusiella is discussed.

Multiple cryptic species in the blue-spotted maskray (Myliobatoidei: Dasyatidae: Neotrygon spp.): An update

Previous investigations have uncovered divergent mitochondrial clades within the blue-spotted maskray, previously Neotrygon kuhlii (Müller and Henle). The hypothesis that the blue-spotted maskray may consist of a complex of multiple cryptic species has been proposed, and four species have been recently described or resurrected. To test the multiple cryptic species hypothesis, we investigated the phylogenetic relationships and coalescence patterns of mitochondrial sequences in a sample of 127 new individuals from the Indian Ocean and the Coral Triangle region, sequenced at both the CO1 and cytochrome b loci. The maximum-likelihood (ML) tree of concatenated CO1+cytochrome b gene sequences, rooted by the New Caledonian maskray N. trigonoides, yielded 9 strongly supported, main clades. Puillandre's ABGD algorithm detected gaps in nucleotide distance consistent with the ML phylogeny. The general mixed Yule-coalescent algorithm partitioned the dataset into putative species generally consistent with the ML phylogeny. Nuclear markers generally confirmed that distinct mitochondrial clades correspond to genetically isolated lineages. The nine main lineages identified by ML analysis were geographically distributed in a parapatric fashion, indicating reproductive isolation. The hypothesis of multiple cryptic species is thus validated.

Next generation sequencing yields complete mitogenomes of Leopard whipray (Himantura leoparda) and Blue-spotted stingray (Neotrygon kuhlii) (Chondrichthyes: Dasyatidae)

The Leopard whipray (Himantura leoparda) and Blue-spotted stingray (Neotrygon kuhlii) are distributed in the Indian and West Pacific Ocean and considered as complex species based on morphological and molecular evidences. In this study, we used the next-generation sequencing method to decode two complete mitogenomes of H. leoparda and N. kuhlii. The assembled mitogenome, consisting lengths of 17,690 bp for H. leoparda and 17,974 bp for N. kuhlii, shows 78% identity to each other. Both mitogenomes follow the typical vertebrate arrangement, including 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs genes and a non-coding control region of D-loop. D-loop with the lengths 1931 bp (H. leoparda) and 2243 bp (N. kuhlii) is located between tRNA-Pro and tRNA-Phe. The overall GC content is 40.3% for H. leoparda and 39.8% for N. kuhlii. The complete mitogenome of H. leoparda and N. kuhlii provides essential and important DNA molecular data for further phylogenetic and evolutionary analyses for stingray species complex.