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Despite being one of the most abundant and highly exploited species in the Mexican Pacific Ocean, information on the biology of the silky shark, Carcharhinus falciformis is limited. The objective of the present study was to describe the reproductive biology of this species, based on 262 sharks (117 females and 145 males) caught from September 2004 to May 2006 in the Gulf of Tehuantepec, Mexico. The size of females ranged from 70 to 229 cm total length (TL); males measured from 69 to 220 cm TL. Female reproductive organ measurements showed that between 175 and 190 cm TL there was an increase in oviducal gland width (19–45 mm), as well as in uterus size (20–220 mm width). Mature males over 180 cm had calcified claspers, well-developed testes (184–282 mm) and presence of sperm in the seminal vesicles. The estimated length of males at first maturity was 180 cm, and that of females was 190 cm. Ovarian fecundity varied from 4 to 11 oocytes, and uterine fecundity varied from 2 to 14 embryos. We infer that mating occurs between May and June. We did not find sperm storage in the oviducal glands. Birth size was observed to be between 60 and 69 cm TL. No defined gestation period was observed. [ABSTRACT FROM PUBLISHER]

Twenty-one nominal species of Muricea have been reported in the Eastern Pacific with nine of them reported in the Mexican Pacific. We describe three new species of Muricea: Muriceaambarae sp. nov. and Muriceacacao sp. nov. , from rocky reefs on the central and the northern Gulf of California and the Pacific coast of Baja California Sur, and Muriceamolinai sp. nov. , from the Pacific coast of Baja California Sur. Muriceaambarae sp. nov. and M.cacao sp. nov. are taxonomically allied to the nominal species Muriceafruticosa Verrill, 1869 due to the morphological similarity of colony growth patterns and the phylogenetic closeness based on the mitochondrial MutS gene (mtMutS); but differ mainly in the calyx form and composition of sclerites. The main morphological differences between the new Muricea species are in their sclerite forms and color; M.ambarae sp. nov. has orange-colored colonies, thin leaf spindles and tuberculated blunt spindles, while M.cacao sp. nov. has dark brown colored colonies, strong spinous spindles and an absence of tuberculated blunt spindles. Muriceamolinai sp. nov. is phylogenetically close and morphologically similar to Muriceasquarrosa Verrill, 1869 in the growth form of the colony and tubular calyces; but has dark brown colored colonies and has calyces from the base to the branch tips. With these three new species, the total number of Muricea species reported in the Mexican northwest region increases to twelve and a total of 24 nominal species in the Eastern Pacific., Competing Interests: No conflict of interest was declared., (Osvaldo Hernández, Jaime Gómez-Gutiérrez, Carolina Galván-Tirado, Carlos Sánchez.)

A colonial ascidian of the genus Distaplia caused a mass mortality of the pen shell Atrinamaura (Sowerby, 1835) during June 2016 in the southwest of the Gulf of California (Mexico), with a significant socio-economic cost. Tentatively identified in previous works as Distapliacf.stylifera, a precise taxonomic determination was still lacking. In the present work, based on a detailed morphological study, it is confirmed that this aggressive species is Distapliastylifera (Kowalevsky, 1874). Originally described from the Red Sea, the species currently has a wide circumtropical distribution (with the exception of the Eastern Pacific to date) and is reported as introduced in parts of its range. The present account thus represents an important range extension of this species. However, when revising the original description and later observations, the reported variability of several characters makes it likely that the binomen is in fact a complex of species, as is common in other ascidians with wide distributions. A complete morphological and genetic study including populations from the entire range of distribution would be necessary to settle the status of D.stylifera . Taxonomic uncertainties hinder a correct interpretation of biogeographical patterns and inference on the origin of the studied population. Nevertheless, the known introduction potential of the species, coupled with an explosive growth in an anthropized environment, and the lack of any previous reports in the Eastern Pacific, strongly suggest that the investigated population represents yet another instance of ascidian introduction. From the point of view of management, its invasive behavior is cause for great concern and warrants mitigation measures., (Betzabé Moreno-Dávila, Leonardo Huato-Soberanis, Jaime Gómez-Gutiérrez, Carolina Galván-Tirado, Carlos Sánchez, Teresa Alcoverro, Eduardo F. Balart, Xavier Turon.)

The infraorder Anomura is a species-rich clade of decapod crustaceans recognized by its remarkable disparity in terms of morphology, anatomy, ecology, physiology, and behavior. This study assembled and characterized the complete mitochondrial genomes of two anomuran species, the hermit crab Coenobita clypeatus and the mole crab Emerita talpoida. The AT-rich mitochondrial genomes of C. clypeatus and E. talpoida are 16,469 bp and 15,810 bp long, respectively, and are composed of 13 protein-coding genes (PCGs), two ribosomal RNA genes, and 22 transfer RNA genes. A 1,390 bp and 553 bp long intergenic space is assumed to be the D-loop in C. clypeatus and E. talpoida, respectively. Mitochondrial synteny in C. clypeatus is identical to that reported in other congeneric hermit crabs while synteny in E. talpoida is identical to that described for the confamilial mole crab Stemonopa insignis. No major differences occur between the studied species and their respective congeneric / cofamilial species in terms of nucleotide composition and codon usage profiles of PCGs. Selective pressure analysis in PCGs, rarely conducted in anomuran crabs, indicate that all these mitochondrial PCGs experience purifying selection and that this purifying selection is stronger in some (i.e., cox family genes and cob) compared to other PCGs (e.g., atp8). Most of the tRNA genes exhibited a typical 'cloverleaf' secondary structure with few exceptions in the two studied species. In C. clypeatus, tRNA-Ser1 lacks the thymine pseudouracil cytosine (TΨC) loop while tRNA-Phe and tRNA-Tyr each exhibit a deletion of the dihydroxyuridine (DHU) loop but not the arm. In turn, in E. talpoida, tRNA-Phe and tRNA-Arg exhibit a deletion of the DHU loop but not the arm while tRNA-Ser1 lacks the TΨC arm. A phylogenomic analysis based on translated PCGs confirms the monophyly of the infraorder Anomura and retrieves most/all relationships at the superfamily and family level previously reported for anomurans. The analysis supports the monophyletic status of the families Albuneidae, Lithodidae, Coenobitidae, and Porcellanidae. In turn, the superfamily Paguroidea, and the families Paguridae and Diogenidae are polyphyletic., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The almaco jack, Seriola rivoliana, is a circumtropical pelagic fish of importance both in commercial fisheries and in aquaculture. To understand levels of genetic diversity within and among populations in the wild, population genetic structure and the relative magnitude of migration were assessed using mtDNA sequence data and single nucleotide polymorphisms (SNPs) from individuals sampled from locations in the Pacific and Atlantic Oceans. A total of 25 variable sites of cytochrome c oxidase subunit 1 and 3678 neutral SNPs were recovered. Three genetic groups were identified, with both marker types distributed in different oceanic regions: Pacific-1 in central Pacific, Pacific-2 in eastern Pacific and Atlantic in western Atlantic. Nonetheless, the analysis of SNP identified a fourth population in the Pacific coast of Baja California Sur, Mexico (Pacific-3), whereas that of mtDNA did not. This mito-nuclear discordance is likely explained by a recently diverged Pacific-3 population. In addition, two mtDNA haplogroups were found within the western Atlantic, likely indicating that the species came into the Atlantic from the Indian Ocean with historical gene flow from the eastern Pacific. Relative gene flow among ocean basins was low with r m < 0.2, whereas in the eastern Pacific it was asymmetric and higher from south to north ( r m > 0.79). The results reflect the importance of assessing genetic structure and gene flow of natural populations for the purposes of sustainable management., (© 2020 Fisheries Society of the British Isles.)

Eleven microsatellite loci were developed and characterized for the sablefish, Anoplopoma fimbria. The markers were identified from sequences obtained by next generation sequencing. Thirty samples from Aleutians Islands were genotyped. The amplifications were performed with three different annealing temperature and amplification products were visualized in ABI 3500 Genetic Analyzer. No evidence for scoring errors was detected by stuttering or due large allele dropout and neither of the loci presented a high null allele frequency (> 0.2). The number means of alleles per locus was of 12.21 and mean of observed and expected heterozygosity were of 0.60 and 0.75 respectively. The sablefish represents a resource of high commercial value on the coasts of Japan, Russia, Canada and west coast of the United States and these new primers could be useful to future diversity and structure population studies.

Determining the relative influence of biotic and abiotic factors on genetic connectivity among populations remains a major challenge in evolutionary biology and in the management and conservation of species. North Pacific hake (Merluccius productus) inhabits upwelling regions in the California Current ecosystem from the Gulf of California to the Gulf of Alaska. In this study, we examined mitochondrial DNA (mtDNA) and microsatellite variation to estimate levels of genetic differentiation of M. productus in relation to the role of oceanographic features as potential barriers to gene flow. Samples were obtained from nine sites spanning a large part of the geographic range of the species, from Puget Sound, Washington to Costa Rica. The microsatellite results revealed three genetically discrete populations: one spanning the eastern Pacific coast, and two apparently resident populations circumscribed to the Puget Sound and the northern Gulf of California (FST = 0.032, p = 0.036). Cytochrome b sequence data indicated that isolation between the Puget Sound and northern Gulf of California populations from the coastal Pacific were recent phenomena (18.5 kyr for Puget Sound and 40 kyr for the northern Gulf of California). Oceanographic data obtained from the Gulf of California support the hypothesis that permanent fronts within the region, and strong gradients at the entrance to the Gulf of California act as barriers to gene flow. A seascape genetics approach found significant genetic-environment associations, where the daytime sea surface temperature and chlorophyll concentrations were the best predictive variables for the observed genetic differentiation. Considering the potential causes of genetic isolation among the three populations, e.g. spawning areas in different latitudes associated with upwelling processes, oceanographic barriers, asymmetric migration and specialized diet, oceanographic barriers appear to be a likely mechanism restricting gene flow.

The live-bearing fish Xenotoca variata is representative of the viviparous Goodeinae subfamily (Goodeidae) from central Mexico. The mitogenome of the X. variata consist of 37 genes in 16,462 bp. Comparing with X. eiseni , the most related of the mitogenomes included, an identity of 91.1% was found and trna-met duplication in X. eiseni is absent in X. variata . The mitogenome provide important information for future studies in evolution of the live-bearing subfamily., Competing Interests: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper., (© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

The complete mitochondrial genome of the sablefish, Anoplopoma fimbria (Genbank accession KP777542) is 16,507 bp in size and contains the typical 37 genes (13 protein-coding, 2 ribosomal RNA, and 22 transfer RNA) found in teleosts mitogenomes. The genome varies in 118 positions with respect to another mitogenome sablefish specimen.

The mitogenome of the tropical gar, Atractosteus tropicus, (GeneBank accession number KJ531198) has a total length of 16,280 bp, and the arrangement consist of 13 protein-coding genes, 2 ribosomal RNA (rRNA) genes and 22 transfer RNA similar to other Lepisosteidae family mitogenomes.

The silky shark mitogenome (GeneBank accession number KF801102) has a total length of 17,774 bp, the base composition of the genomes was as follows: A (31.36%), T (30.18%), C (25.27%) and G (13.17%), which demonstrated an A + T-rich feature (61.64%), similar to other elasmobranch mitogenomes. The mitochondrial genome contained 13 protein-coding genes and 23 tRNA genes. The tRNA genes ranged from 70 to 72 bp. The gene order was the same as in other vertebrates and teleosts.