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Larval genetic information influences populations’ genetic pools, causing genetic homogenization or structuration. So, knowing about adult and larval genetic information is essential to understand processes such as connectivity. The aims are to evaluate Twospot flounder (Bothus robinsi, a fish with a high dispersal potential) larval pools’ genetic diversity, test if the larvae tend to mix or display collective dispersal, compare genetic information between larvae and adults and evaluate its connectivity. We used ddRADSEQ to genotype 1,034 single nucleotide polymorphic sites from B. robinsi larvae sampled in waters from the Bay of Campeche and the eastern Gulf of Mexico (GOM) and adults sampled on Florida’s continental shelf. Larvae were identified morphologically and by DNA barcoding. We estimated Fst-paired comparations, Principal Components Analysis (PCA), Discriminant Analyses of Principal Components (DAPC), and a Structure analysis to understand genetic trends. With the software COLONY, we made a sibship evaluation. We observed no significant heterogeneity among regions (Fst p-values>0.05). PCA, DAPC, and the Structure Analysis showed one genetic cluster, indicating genetic homogeneity. We did not detect full-sibs or half-sibs. We linked the results with the high dispersal potential of B. robinsi due to a long pelagic larval duration and the potential of ocean dynamics to transport and mix larvae from all GOM shelf areas. These findings suggest that the dispersal potential of B. robinsi is large enough to produce genetic connectivity in all GOM subpopulations and that time spent by its larvae in dispersal pathways is enough to mix larvae from different GOM subpopulations, indicating a panmictic population.

Loricifera is a group of marine, meiobenthic invertebrates of microscopic size that are found worldwide. The Loriciferan fauna of the Southern Gulf of Mexico (SGM) remains unknown. In the present study we report on the first exploration of the Loriciferans from the SGM, which is a strategic area for oil exploitation. The Loriciferan specimens were collected during deep-sea cruises XIXIMI-4 (August-September 2015) and XIXIMI-6 (August 2017), in which six out of 22 stations yielded specimens of Loricifera. A total of six specimens were found (although one of them was lost), namely two adults and four larval stages. Preliminary analyses based on the peculiarity of their morphological features indicate that the specimens include representatives of new species of Pliciloricus and Rugiloricus, an undescribed genus of Pliciloricidae and, possibly, an undescribed genus of Nanaloricidae. None of the specimens found could be assigned to previously described species. Since all specimens are either intermediate life cycle stages or poorly preserved, only a short description based on their morphological traits is provided here. Our findings are discussed from a comparative perspective with known Loriciferan species.

Deep-water sampling in the Perdido Fold Belt, Gulf of Mexico, Mexican Economic Exclusive Zone yielded five specimens of tardigrades belonging to the genus Coronarctus Renaud-Mornant, 1974. The specimens represent the first records of the genus for Mexico. Two two-clawed larvae and two four-clawed larvae of Coronarctus mexicus Romano, Gallo, D’Addabbo, Accogli, Baguley & Montagna, 2011 and a single four-clawed larval specimen of an undescribed Coronarctus species were identified. Taxonomic analysis of the specimens contributed to the knowledge of deep-sea and Mexican marine tardigrades, two data-poor areas of study.

The complete mitogenome of Thoosa mismalolli Carballo, Cruz-Barraza & Gómez, 2004 (Tetractinellida, Thoosidae) was sequenced. This is the first complete mitogenome of the suborden Thoosina and the third Tetractinellid so far. The mitochondrial genome of T. mismalolli was assembled based on reads obtained with the Illumina HiSeq platform. The length of complete mitogenome is 19,019 bp long and contained 14 protein-coding genes and 23 tRNA, with two tRNA genes. Phylogenetic reconstruction (maximum-likelihood) based on mitogenome of Tetractinellids, supports T. mismalolli as a sister group. This result is congruent with those obtained with molecular markers (CO1, 18S, and 28S), supporting the monophyletic status of Thoosa and providing additional molecular data in favor of the suborder Thoosina.

The role of habitat complexity has been widely neglected in the study of meiofaunal community patterns. We studied the intertidal nematode community of a structurally complex macrotidal beach exhibiting contrasting microhabitats (sandbars and runnels) to understand the influence of environmental gradients and habitat heterogeneity in the community structure. We tested whether topographical complexity affected (1) the zonation pattern in terms of abundance and diversity, and (2) local diversity by promoting compartmentalization into distinct faunal groups. Our analyses revealed three major faunal assemblages along the exposure gradient associated to differences in mean grain size and chlorophyll a. Diversity patterns involved a mid-intertidal peak, consistent with the intermediate disturbance hypothesis, and another peak at the limit with the subtidal region, consistent with the transition zone. These results highlight the predominance of environmental gradients in establishing intertidal zonation. However, microhabitats differed in environmental conditions and possessed significantly distinct nematofaunal communities. Runnels featured higher levels of taxonomic and functional diversity, many unique genera, and the community differed from the assemblage at the limit to the subtidal, stressing their role as distinct microhabitats. The nematofauna of the structurally complex beach was more diverse than the one from a homogeneous beach nearby, supporting the hypothesis that structural heterogeneity promotes diversity by compartmentalization and highlighting the importance of microhabitats in the assessment of biodiversity. Contrary to previous predictions, our results indicate potentially high regional marine nematode diversity in the Upper Gulf of California.

The GI microbiota of abalone contains a highly complex bacterial assemblage playing an essential role in the overall health of these gastropods. The gut bacterial communities of abalone species characterized so far reveal considerable interspecific variability, likely resulting from bacterial interactions and constrained by the ecology of their abalone host species; however, they remain poorly investigated. Additionally, the extent to which structural changes in the microbiota entail functional shifts in metabolic pathways of bacterial communities remains unexplored. In order to address these questions, we characterized the gut microbiota of the northeast Pacific blue (Haliotis fulgens or HF) and yellow (Haliotis corrugata or HC) abalone by 16S rRNA gene pyrosequencing to shed light on: (i) their gut microbiota structure; (ii) how bacteria may interact among them; and (iii) predicted shifts in bacterial metabolic functions associated with the observed structural changes. Our findings revealed that Mycoplasma dominated the GI microbiome in both species. However, the structure of the bacterial communities differed significantly in spite of considerable intraspecific variation. This resulted from changes in predominant species composition in each GI microbiota, suggesting host-specific adaptation of bacterial lineages to these sympatric abalone. We hypothesize that the presence of exclusive OTUs in each microbiota may relate to host-specific differences in competitive pressure. Significant differences in bacterial diversity were found between species for the explored metabolic pathways despite their functional overlap. A more diverse array of bacteria contributed to each function in HC, whereas a single or much fewer OTUs were generally observed in HF. The structural and functional analyses allowed us to describe a significant taxonomic split and functional overlap between the microbiota of HF and HC abalone.

The coral Porites sverdrupi is the only scleractinian endemic to the Gulf of California. Over the last 2 decades its populations have been restricted to 3 areas, La Paz Bay, Loreto Bay, and Concepción Bay. As this species faces a high risk of extinction, there is an urgent need for biological, ecological, and genetic information for the guidance of conservation efforts. This is the first study on genetic diversity and connectivity in the species. For this, we analyzed coral colonies from Loreto Bay and Concepción Bay. Our results show that there is high genetic diversity in P. sverdrupi at both sites, with significant genetic structure between them. This condition is caused by a combination of short pelagic larval duration, low dispersal potential between the populations, and local adaptation. Our results emphasize the need for more research in order to establish adequate conservation strategies.

We report the first mitochondrial genome of a Verongid sponge, Aplysina gerardogreeni from the Pacific Ocean. This has 19,620 bp and includes 14 protein-coding genes, 2 rRNAs genes, and 25 tRNAs genes. The gene arrangement was similar to the one found in two Caribbean Aplysina mitogenomes previously reported. Comparative analyses revealed a few substitutions among congeneric mitogenomes. The mitogenome of A. gerardogreeni could be useful to study the evolution of Verongimorpha group and also to identify adequate genes for its molecular systematics.

Geographic variation in external morphology is thought to reflect an interplay between genotype and the environment. Morphological variation has been well-described for a number of cetacean species, including the bottlenose dolphin (Tursiops truncatus). In this study we analyzed dorsal fin morphometric variation in coastal bottlenose dolphins to search for geographic patterns at different spatial scales. A total of 533 dorsal fin images from 19 available photo-identification catalogs across the three Mexican oceanic regions (Pacific Ocean n = 6, Gulf of California n = 6 and, Gulf of Mexico n = 7) were used in the analysis. Eleven fin shape measurements were analyzed to evaluate fin polymorphism through multivariate tests. Principal Component Analysis on log-transformed standardized ratios explained 94% of the variance. Canonical Discriminant Function Analysis on factor scores showed separation among most study areas (p

Mark-recapture techniques are fundamental for assessing marine mammal population dynamics and individual temporal patterns. Since biases imposed by field conditions are generally unknown, we simulated variations in sampling effort (m) and maximum individual catchability (r max) to analyze their effects on residency levels measured through the number of recaptures (occurrence, O), duration of stay (permanence, P), and average recurrence (periodicity, I) relative to a reference level of exhaustive daily sampling frequency. The number or recorded individuals (Dr) was also used to determine the performance of the simulations. Results for standardized (s) parameters showed that occurrences (Os) were proportional to m and were not influenced by r max. Individual permanence (Ps) and individual periodicity (Is) were 8-49% and 3-11.74 times lower than expected, respectively, depending on m and r max. Also, Os, Ps, and Is were not influenced by study duration, thus inter-study comparisons are feasible if m and r max are similar. Dr was 68-92% (r max= 0.01) and 1-8% (r max= 1.0) lower than expected depending on m. Longer studies were more accurate but greater effort did not significantly increase Dr estimates. The use of bimonthly sampling frequencies (m= 0.07) was barely accurate and predictions for incomplete datasets were poor. Survey field data were also analyzed from 14 published studies on 4 dolphin species and compared to daily sampling frequencies; resulting values for Os, Ps, and Dr were 62.4-93.3%, 11.6-66.4%, and 2.4-33.8% lower than expected, respectively; also Is was 2.3-7.3 times lower than expected. The model produced Dr values that were similar to population estimates from empirical data, and bias was smaller than 15% in 87.5% of the cases, thus simulation accuracy was deemed acceptable.Las técnicas de marcado-recaptura son fundamentales para evaluar la dinámica poblacional de mamíferos marinos y sus patrones temporales individuales. Se simularon variaciones en el esfuerzo (m) y la máxima capturabilidad individual (r max) para analizar los sesgos en la residencia individual, medida como el número de recapturas (presencia, O), la duración de la estancia (permanencia, P) y la recurrencia promedio (asiduidad, I), en relación con un muestreo exhaustivo de frecuencia diaria. También se analizó el número de individuos registrados (Dr) para determinar el desempeño de las simulaciones. Los resultados de los parámetros estandarizados (s) mostraron que la presencia (Os) fue proporcional a m sin ser influida por r max. La permanencia (Ps) y la asiduidad (Is) fueron 8-49% y 3-11.74 veces más bajas que lo esperado, respectivamente, dependiendo de m y r max. Los valores de Os, Ps e Is no cambiaron con la duración del muestreo y las comparaciones entre estudios son posibles siempre que m y r max sean similares. El valor de Dr fue entre 68-92% (r max= 0.01) y 1-8% (r max= 1.0) menor de lo esperado dependiendo de m. Aunque los estudios más largos fueron más precisos, un mayor esfuerzo no incrementó significativamente el valor de Dr. Los muestreos quincenales fueron poco precisos y las predicciones para datos incompletos fueron poco confiables. También se analizaron los datos de campo de 14 estudios publicados de cuatro especies de delfines y se compararon contra muestreos diarios; los resultados de Os, Ps y Dr fueron 62.4-93.3%, 11.6-66.4% y 2.4-33.8% más bajos de lo esperado, respectivamente; además, Is fue 2.3-7.3 veces más baja que lo esperado. El modelo produjo valores para Dr que fueron similares a las estimaciones poblacionales de los estudios empíricos, con un sesgo menor al 15% en 87% de los casos, por lo que se considera que la precisión del modelo es aceptable.

The Mexican rockfish Sebastes macdonaldi is the Northeast Pacific rockfish with the southernmost distribution, featuring isolated populations in the Gulf of California. We analysed seven microsatellite loci in 111 organisms collected throughout most of its geographical range to test long-standing hypotheses regarding its disjunct distribution. One locus was fixed and the number of alleles in polymorphic loci ranged from 2 to 24 (average 13.5). We found very high levels of polymorphism (overall He = 0.75) comparable to other congeneric species but no significant differences in genetic diversity among localities or between Pacific and Gulf of California populations (p > 0.1). Significant shifts in allelic and genotypic frequencies were detected at three loci, which resulted in a small but significant partitioning of genetic variance among California, Baja California and Gulf of California populations (FST = 0.007, p = 0.03) and between Gulf and Pacific populations (FST = 0.01, p = 0.004). The latter but not the former result was corroborated by analyses of molecular variance (AMOVA) using the number of distinct alleles (FST) and the sum of square differences of allele sizes (RST) as Euclidean distances. The evidence argues against contemporary gene flow between the gulf and the Pacific ocean and against an ancient invasion of the gulf with a founder effect. The small level of divergence favours a recent dispersal but a larger data set including DNA sequences amenable to phylogenetic analyses will help to test alternative hypotheses of dispersal versus vicariance.

ABSTRACT Geoduck clams have become the most profitable emerging fishery resource in Northwest Mexico, with profits of more than USS30 million during the last few years. The fishery targets two [...]

Biodiversity has diminished over the past decades with climate change being among the main responsible factors. One consequence of climate change is the increase in sea surface temperature, which, together with long exposure periods in intertidal areas, may exceed the tolerance level of benthic organisms. Benthic communities may suffer structural changes due to the loss of species or functional groups, putting ecological services at risk. In sandy beaches, free-living marine nematodes usually are the most abundant and diverse group of intertidal meiofauna, playing an important role in the benthic food web. While apparently many functionally similar nematode species co-exist temporally and spatially, experimental results on selected bacterivore species suggest no functional overlap, but rather an idiosyncratic contribution to ecosystem functioning. However, we hypothesize that functional redundancy is more likely to observe when taking into account the entire diversity of natural assemblages. We conducted a microcosm experiment with two natural communities to assess their stress response to elevated temperature. The two communities differed in diversity (high [HD] vs. low [LD]) and environmental origin (harsh vs. moderate conditions). We assessed their stress resistance to the experimental treatment in terms of species and diversity changes, and their function in terms of abundance, biomass, and trophic diversity. According to the Insurance Hypothesis, we hypothesized that the HD community would cope better with the stressful treatment due to species functional overlap, whereas the LD community functioning would benefit from species better adapted to harsh conditions. Our results indicate no evidence of functional redundancy in the studied nematofaunal communities. The species loss was more prominent and size specific in the HD; large predators and omnivores were lost, which may have important consequences for the benthic food web. Yet, we found evidence for alternative diversity-ecosystem functioning relationships, such as the Rivets and the Idiosyncrasy Model.