Iris Segura-García

Within-shelter behaviour of the spotted spiny lobster, Panulirus guttatus (latreille), in simulated communal dens: an exploratory study

Panulirus guttatus is a sedentary spiny lobster that dwells in the coral reef habitat. We conducted an exploratory study to describe the within-shelter behaviour of groups of 4–6 individuals of P. guttatus in simulated communal dens deployed in tanks. Lobsters displayed a diel within-shelter activity rhythm, with a peak shortly before dawn due to an increase in agonistic interactions among sheltered individuals. In a single-chamber cave, aggressions resulted in the constant rearrangement of individuals in the den, related to their preference to cling to the walls. In a triple-chamber cave, the largest male often defended one chamber, but the remaining individuals tended to aggregate in one of the other two chambers during the day. These trends suggest that P. guttatus is a gregarious lobster, but that this gregariousness is influenced by the amount of available shelters and by temporary, size-related social hierarchies. This hypothesis should be tested with fully replicated experiments to help understand the patterns of shelter utilization of P. guttatus in the coral reef habitat.

Eco-evolutionary processes generating diversity among bottlenose dolphin, tursiops truncatus, populations off Baja California, Mexico.

For highly mobile species that nevertheless show fine-scale patterns of population genetic structure, the relevant evolutionary mechanisms determining structure remain poorly understood. The bottlenose dolphin (Tursiops truncatus) is one such species, exhibiting complex patterns of genetic structure associated with local habitat dependence in various geographic regions. Here we studied bottlenose dolphin populations in the Gulf of California and Pacific Ocean off Baja California where habitat is highly structured to test associations between ecology, habitat dependence and genetic differentiation. We investigated population structure at a fine geographic scale using both stable isotope analysis (to assess feeding ecology) and molecular genetic markers (to assess population structure). Our results show that there are at least two factors affecting population structure for both genetics and feeding ecology (as indicated by stable isotope profiles). On the one hand there is a signal for the differentiation of individuals by ecotype, one foraging more offshore than the other. At the same time, there is differentiation between the Gulf of California and the west coast of Baja California, meaning that for example, nearshore ecotypes were both genetically and isotopically differentiated either side of the peninsula. We discuss these data in the context of similar studies showing fine-scale population structure for delphinid species in coastal waters, and consider possible evolutionary mechanisms.

Post-glacial habitat release and incipient speciation in the genus Delphinus

The role of ecological and changing environmental factors in the radiation of species diversity is a fundamental question in evolutionary biology. Of particular interest is the potential for these factors to determine the boundary between what we would consider differentiation among populations and incipient speciation. Dolphins in the genus Delphinus provide a useful test case, exhibiting morphological variation in beak length, coloration and body size across their wide geographic distribution, and in particular among coastal and more pelagic habitats. Two species have been proposed, D. delphis and D. capensis, but morphologically similar allopatric populations are not monophyletic, indicating that the mostly coastal ‘long-beaked’ D. capensis form is not a single globally distributed species. However, the sympatric populations in the Eastern North Pacific currently designated as these two species are both morphologically and genetically differentiated. Here we use microsatellite DNA and mitochondrial DNA markers to investigate the evolutionary mechanisms that led to this incipient speciation event. We used coalescent and assignment methods to investigate the timing and extent of reproductive isolation. Our data indicate that although there is some level of on-going gene flow, the putative species found in the Eastern North Pacific are reciprocally monophyletic. The timing of isolation appears to be associated with regional changes in paleoceanographic conditions within the Holocene timeframe.

Panulirus argus virus 1 detected in oceanic postlarvae of Caribbean spiny lobster: implications for disease dispersal.

Panulirus argus virus 1 (PaV1), a pathogenic virus that specifically attacks Caribbean spiny lobsters Panulirus argus, was recently detected in newly settled postlarvae of P. argus. As PaV1 appears not to be vertically transmitted, infected postlarvae likely acquire PaV1 from the water, but whether this can occur in oceanic waters where the planktonic larvae (phyllosomata) metamorphose into nektonic postlarvae remains unknown. Late-stage phyllosomata and postlarvae of P. argus were collected at distances of 2 to 100 km from the Caribbean coast of Mexico in 2 oceanographic cruises. Most postlarvae were caught in the upper meter of water, usually along with masses of floating Sargassum algae. A PaV1-PCR assay was used to test 169 phyllosomata (stages VI-X) and 239 postlarvae. All phyllosomata tested negative, but 2 postlarvae, 1 from each cruise, tested positive for PaV1. These postlarvae were collected at 55 and 48 km offshore over depths of 850 and 1800 m, respectively, suggesting that postlarvae can acquire PaV1 in offshore waters. We hypothesize that floating Sargassum may be an environmental reservoir for PaV1. The PaV1 allele (460 pb) found in an infected postlarva was more closely related to PaV1 alleles found in lobsters from Puerto Rico than in lobsters from any other location (including Mexico), suggesting high gene flow and long-distance dispersal of PaV1, consistent with previous studies of high genetic connectivity across the Caribbean.

Genetic characterization of the artisanal mud crab fishery in Myanmar

Fish are important for food supply, especially in developing countries. In Southeast Asia, including Myanmar, the mud crab fishery is an important livelihood that represents a valuable source of income and food to coastal communities. However, the increasing demand for mud crab in domestic and international markets and poor management has generated concern about the status of this fishery across Southeast Asia. In this region, at least four species of mud crab in the genus Scylla are recognised but their correct identification and occurrence remain to be fully explained. Relying on accurate taxonomic identification of mud crab species represents the cornerstone of the successful implementation of management plans as life history biology and relative exploitation rates may vary by species due to gear susceptibility. Toward this aim, tissue samples from mud crabs were collected from four fishing communities of the Mergui archipelago, in the Tanintharyi region of southern Myanmar. All crab samples were DNA barcoded for species identification through sequencing. This study is the first genetic characterization of the mud crab fishery in Myanmar and revealed that Scylla olivacea was the only species found in the sampled fisheries of the Tanintharyi region. The populations studied across the Mergui archipelago did not show evidence of genetic structure, but gene flow appeared to be limited among conspecifics from neighbouring countries.