Manuel Uribe-Alcocer

Spatial differentiation in the eastern Pacific yellowfin tuna revealed by microsatellite variation

Five eastern Pacific yellowfin tuna samples (four northern: 10–25°N, 95–130°W, and one southern: 16–18°S, 95–97°W), collected from fishing vessels between 1994 and 2002 were analyzed for variation at seven microsatellite loci to evaluate their spatial genetic homogeneity. Single-locus homogeneity exact tests revealed significant genetic differentiation caused by three of seven loci. Pairwise sample comparisons of multilocus allele-frequency homogeneity tests and subpopulation division (FST), revealed significant differentiation in comparisons between north equatorial samples and the south equatorial sample. AMOVA analysis among collections grouped as northern and southern populations separated by the equator in the eastern Pacific confirmed the differentiation observed. These results may be considered as preliminary evidence of the presence of discrete populations in the eastern Pacific yellowfin tuna. The possibility that the spatial differentiation observed corresponds to temporal variation or non-random sampling cannot be discarded. The genetic differences encountered need to be corroborated by increasing sample sizes, including temporal replicates, and by the use of an alternative marker.

Comparative population structure of three snook species (Teleostei: Centropomidae) from the eastern central Pacific

Three snook species, Centropomus viridis, Centropomus medius, and Centropomus robalito, from the eastern central Pacific, representing three of the four proposed phyletic lineages in the genus, were analyzed for genetic variability by means of allozyme and RAPD to evaluate the divergence between populations at different levels of dispersal ability and to evaluate the importance of barriers to dispersal in the population subdivision and genetic diversity. Levels of genetic diversity among species estimated by allozymes were similar and consistent with the observed levels of differentiation in marine fish species. Mean heterozygosity ranged from 0.089 for C. viridis to 0.10 for C. robalito. Genetic diversity for the snook species studied was slightly higher than the mean estimation reported in allozymes for 106 marine fish (0.055) and for anadromous fish species (0.043 to 0.057). Multilocus allele frequency homogeneity tests and population-subdivision estimates for both allozyme and RAPD markers revealed the existence of population structure in C. viridis and C. medius, in coincidence with geographic separation of samples, whereas no divergence was detected in C. robalito. This finding may be attributed to the greater population size of C. robalito, which originated by a recent population range expansion, and hence the potential for dispersal is mediated by larval drift. Fluctuations in population size and population range expansion are used to explain discrepancies between levels of genetic diversity and population structure in the studied species.

Fish Chromosomes as Biomarkers of Genotoxic Damage and Proposal for the Use of Tropical Catfish Species for Short-Term Screening of Genotoxic Agents

Aquatic systems are essential for life. Human subsistence and health are linked to these systems, as they are indispensable for food production through agriculture, livestock raising and fisheries and to industrial processes to satisfy society’s needs. However, these systems have often been converted, as negative by-products of progress, into reservoirs of wastes expecting natural degradation or recycling, or as long-term or permanent storage for materials of great endurance. The unawareness of the threat of a faster accumulation of wastes than what the systems can recycle, has turned the aquatic environments into regions of accumulation and concentration of dangerous genotoxic agents with serious risks to the organisms that depend directly or indirectly on water, that is, all living beings.

Complete mitochondrial DNA genome of bonnethead shark, Sphyrna tiburo, and phylogenetic relationships among main superorders of modern elasmobranchs

Elasmobranchs are one of the most diverse groups in the marine realm represented by 18 orders, 55 families and about 1200 species reported, but also one of the most vulnerable to exploitation and to climate change. Phylogenetic relationships among main orders have been controversial since the emergence of the Hypnosqualean hypothesis by Shirai (1992) that considered batoids as a sister group of sharks. The use of the complete mitochondrial DNA (mtDNA) may shed light to further validate this hypothesis by increasing the number of informative characters. We report the mtDNA genome of the bonnethead shark Sphyrna tiburo, and compare it with mitogenomes of other 48 species to assess phylogenetic relationships. The mtDNA genome of S. tiburo, is quite similar in size to that of congeneric species but also similar to the reported mtDNA genome of other Carcharhinidae species. Like most vertebrate mitochondrial genomes, it contained 13 protein coding genes, two rRNA genes and 22 tRNA genes and the control region of 1086 bp (D-loop). The Bayesian analysis of the 49 mitogenomes supported the view that sharks and batoids are separate groups.

Population Genetic Structure of the Bonnethead Shark, Sphyrna tiburo, from the Western North Atlantic Ocean Based on mtDNA Sequences

The population genetic structure of 251 bonnethead sharks, Sphyrna tiburo, from estuarine and nearshore ocean waters of the Western North Atlantic Ocean (WNA), was assessed using sequences of the mitochondrial DNA-control region. Highly significant genetic differences were observed among bonnetheads from 3 WNA regions; Atlantic coast of Florida, Gulf coast of Florida, and southwestern Gulf of Mexico (analysis of molecular variance, ΦCT = 0.137; P=0.001). Within the Gulf coast of Florida region, small but significant genetic differences were observed between bonnetheads from neighboring estuaries. These overall patterns were consistent with known latitudinal and inshore-offshore movements that occur seasonally for this species within US waters, and with the residency patterns and high site fidelity to feeding/nursery grounds reported in estuaries along the Atlantic coast of Florida and South Carolina. Historical demography also supported the occurrence of past population expansions occurring during Pleistocene glacial-interglacial cycles that caused drastic reductions in bonnethead population size, as a consequence of the eustatic processes that affected the Florida peninsula. This is the first population genetics study for bonnetheads to report genetic divergence among core abundance areas in US and Mexican waters of the WNA. These results, coupled with recent advances in knowledge regarding regional differences in life-history parameters of this species, are critical for defining management units to guide future management strategies for bonnetheads within US waters and across international boundaries into Mexico.

Variación morfológica del camarón café (Farfantepenaeus californiensis) en el Pacífico mexicano

espanolEl analisis multivariado de datos morfometricos se ha utilizado ampliamente en especies comerciales para definir unidades de pesca independientes. En la presente investigacion se analizo la diferenciacion del camaron cafe Farfantepenaeus californiensis (Holmes, 1900) del Pacifico mexicano mediante el analisis morfometrico de 171 individuos recolectados en 4 localidades y se comparo con la subdivision geografica que el Instituto Nacional de la Pesca establecio para el monitoreo de sus poblaciones. La variacion morfologica de cada muestra se estimo mediante el (CV%) promedio de 18 medidas. Se realizo un analisis discriminante utilizando proporciones estandarizadas de algunas de estas medidas y se calcularon las distancias de Manhattan entre las muestras; con estas se obtuvo un dendrograma por el metodo UPGMA en el cual la agrupacion de las localidades mostro una diferenciacion morfologica clinal, relacionada con un gradiente geografico. La baja variabilidad morfologica estimada al interior de las muestras permitio inferir que cada localidad conforma un grupo fenotipicamente homogeneo, aunque con claras diferencias entre si, que podrian estar relacionadas con las caracteristicas ambientales de cada localidad y con posibles variaciones geneticas entre las poblaciones. La diferenciacion morfologica del camaron cafe del Pacifico mexicano que se encontro en esta investigacion aporta elementos adicionales para sustentar la division geografica que el Instituto Nacional de la Pesca ha establecido para el estudio de la pesqueria del camaron. EnglishMultivariate analyses of morphometric data have been widely used to define independent fishing units for exploited species. In this study we analyzed the morphometric variability of 4 brown shrimp Farfantepenaeus californiensis (Holmes, 1900) locations from the Mexican Pacific to assess whether differentiation agrees with the geographical subdivision established by the Instituto Nacional de la Pesca to monitoring the brown shrimp populations. The morphologic variation of each sample was estimated through the variation coefficient (CV%) averaged over 18 measurements. A discriminant analysis was made using the standardized ratios for some of the measurements. Manhattan distances among samples were calculated to obtain a dendrogram with the UPGMA method where localities grouping showed a clinal pattern of morphological differentiation related to a geographical gradient. The low estimated morphologic variability within samples allowed us to conclude that each sampled locality conforms a phenotypically homogeneous group, with clear differences to the others. These differences could be explained on basis of the environmental characteristics of each locality in addition to possible genetic variations between populations. Thus, the morphological differentiation of the brown shrimp populations of the Mexican Pacific detected in this study provides additional elements to sustain the geographical division that the Instituto Nacional de la Pesca established to survey the shrimp fishery.

Molecular evidence supporting the expansion of the geographical distribution of the Brazilian cownose ray Rhinoptera brasiliensis (Myliobatiformes: Rhinopteridae) in the western Atlantic

The genus Rhinoptera is composed of eight species widely distributed in tropical, subtropical and temperate coastal waters, which inhabit bays, estuaries and river mouths. Cownose ray Rhinoptera bonasus has been reported to inhabit the Western Atlantic including the Gulf of Mexico and the Caribbean, whereas the Brazilian cownose ray R. brasiliensis has been considered endemic to the coast of Brazil. Recent reports of R. brasiliensis in the Gulf of Mexico bring about the question of whether the species has a wider range than previously reported. Here, the mitochondrial genes COI, Cytb, NADH2 and the nuclear gene RAG1 were used to distinguish among species and to confirm the presence of R. brasiliensis in the Gulf of Mexico. R. brasiliensis specimens collected along the southern Gulf of Mexico showed a remarkable genetic and morphological affinity when compared with R. brasiliensis specimens from Brazil, supporting the presence of the species in Mexico (from Veracruz through Campeche) and providing evidence that its distribution ranges from Brazil to the Caribbean Sea and the Gulf of Mexico. Both species overlap geographically to a large degree, leading to a reassessment of their conservation status. Our results also show that R. bonasus distribution in the Gulf of Mexico may be restricted to the northern portion, in US waters.

Complete mitochondrial genome of the porbeagle shark, Lamna nasus (Chondrichthyes, Lamnidae)

Abstract We report for the first time, the complete mitochondrial genome sequence of the porbeagle shark, Lamna nasus, from a specimen collected from offshore waters of New England, USA in the western North Atlantic Ocean. The genome structure of this species is similar to the other reported shark mitogenomes. The genome sequence has a total length of 16,697 bases; similar in size to the mtDNA genomes reported for other lamnid species. A Bayesian phylogenetic tree was reconstructed for the Lamnidae family using mitogenome sequences available in the Genbank.