Integrative methods reveal multiple drivers of diversification in rice paddy snakes

Divergence dating analyses in systematics provide a framework to develop and test biogeographic hypotheses regarding speciation. However, as molecular datasets grow from multilocus to genomic, sample sizes decrease due to computational burdens, and the testing of fine-scale biogeographic hypotheses becomes difficult. In this study, we use coalescent demographic models to investigate the diversification of poorly known rice paddy snakes from Southeast Asia (Homalopsidae: Hypsiscopus), which have conflicting dates of origin based on previous studies. We use coalescent modeling to test the hypothesis that Hypsiscopus diversified 2.5 mya during the Khorat Plateau uplift in Thailand. Additionally, we use ecological niche analyses to identify potential differences in the niche space of the two most widely distributed species in the past and present. Our results suggest Hypsiscopus diversified ~ 2.4 mya, supporting that the Khorat Plateau may have initiated the diversification of rice paddy snakes. We also find significant niche differentiation and shifts between species of Hypsiscopus, indicating that environmental differences may have sustained differentiation of this genus after the Khorat Plateau uplift. Our study expands on the diversification history of snakes in Southeast Asia, and highlights how results from smaller multilocus datasets can be useful in developing and testing biogeographic hypotheses alongside genomic datasets.

Sea snake harvest in the gulf of Thailand

Conservation of sea snakes is virtually nonexistent in Asia, and its role in human-snake interactions in terms of catch, trade, and snakebites as an occupational hazard is mostly unexplored. We collected data on sea snake landings from the Gulf of Thailand, a hotspot for sea snake harvest by squid fishers operating out of the ports of Song Doc and Khanh Hoi, Ca Mau Province, Vietnam. The data were collected during documentation of the steps of the trading process and through interviewers with participants in the trade. Squid vessels return to ports once per lunar synodic cycle and fishers sell snakes to merchants who sort, package, and ship the snakes to various destinations in Vietnam and China for human consumption and as a source of traditional remedies. Annually, 82 t, roughly equal to 225,500 individuals, of live sea snakes are brought to ports. To our knowledge, this rate of harvest constitutes one of the largest venomous snake and marine reptile harvest activities in the world today. Lapemis curtus and Hydrophis cyanocinctus constituted about 85% of the snake biomass, and Acalyptophis peronii, Aipysurus eydouxii, Hydrophis atriceps, H. belcheri, H. lamberti, and H. ornatus made up the remainder. Our results establish a quantitative baseline for characteristics of catch, trade, and uses of sea snakes. Other key observations include the timing of the trade to the lunar cycle, a decline of sea snakes harvested over the study period (approximately 30% decline in mass over 4 years), and the treatment of sea snake bites with rhinoceros horn. Emerging markets in Southeast Asia drive the harvest of venomous sea snakes in the Gulf of Thailand and sea snake bites present a potentially lethal occupational hazard. We call for implementation of monitoring programs to further address the conservation implications of this large-scale marine reptile exploitation.

Phylogeography of the Mekong mud snake (Enhydris subtaeniata): the biogeographic importance of dynamic river drainages and fluctuating sea levels for semiaquatic taxa in Indochina

During the Cenozoic, Southeast Asia was profoundly affected by plate tectonic events, dynamic river systems, fluctuating sea levels, shifting coastlines, and climatic variation, which have influenced the ecological and evolutionary trajectories of the Southeast Asian flora and fauna. We examined the role of these paleogeographic factors on shaping phylogeographic patterns focusing on a species of semiaquatic snake, Enhydris subtaeniata (Serpentes: Homalopsidae) using sequence data from three mitochondrial fragments (cytochrome b, ND4, and ATPase-2785 bp). We sampled E. subtaeniata from seven locations in three river drainage basins that encompassed most of this species' range. Genetic diversities were typically low within locations but high across locations. Moreover, each location had a unique suite of haplotypes not shared among locations, and pairwise φ(ST) values (0.713-0.998) were highly significant between all location pairs. Relationships among phylogroups were well resolved and analysis of molecular variance (AMOVA) revealed strong geographical partitioning of genetic variance among the three river drainage basins surveyed. The genetic differences observed among the populations of E. subtaeniata were likely shaped by the Quaternary landscapes of Indochina and the Sunda Shelf. Historically, the middle and lower Mekong consisted of strongly dissected river valleys separated by low mountain ranges and much of the Sunda Shelf consisted of lowland river valleys that served to connect faunas associated with major regional rivers. It is thus likely that the contemporary genetic patterns observed among populations of E. subtaeniata are the result of their histories in a complex terrain that created abundant opportunities for genetic isolation and divergence yet also provided lowland connections across now drowned river valleys.

High level of cryptic species diversity revealed by sympatric lineages of Southeast Asian forest frogs

Amphibians tend to exhibit conservative morphological evolution, and the application of molecular and bioacoustic tools in systematic studies have been effective at revealing morphologically 'cryptic' species within taxa that were previously considered to be a single species. We report molecular genetic findings on two forest-dwelling ranid frogs from localities across Southeast Asia, and show that sympatric evolutionary lineages of morphologically cryptic frogs are a common pattern. These findings imply that species diversity of Southeast Asian frogs remains significantly underestimated, and taken in concert with other molecular investigations, suggest there may not be any geographically widespread, forest-dwelling frog species in the region. Accurate assessments of diversity and distributions are needed to mitigate extinctions of evolutionary lineages in these threatened vertebrates.

Foraging ecology of the Tokay gecko, Gekko gecko in a residential area in Thailand

Abstract

The foraging behavior of Gekko gecko was observed at the visitor complex of the Khao Khiao Open Zoo at the Khao Khiao-Khao Chomphu Wildlife Sanctuary in Chon Buri Province, Thailand. Foraging parameters of G. gecko (foraging period, time spent moving, foraging attempts, foraging success, prey size consumed, and foraging distance) did not vary significantly between males, females, and juveniles. Individuals foraged between 18:01 and 09:00 hrs. Peak emergence time was between 18:01 and 20:00 hrs. Peak retreat time was between 04:01 and 07:00 hrs. Major food items included insects of the orders Lepidoptera, Orthoptera, and Coleoptera. Prey sizes of males, females, and juveniles were not significantly different, indicating no prey size selection. This may have been due to low insect availability in the habitat. Gekko gecko tended to be a sit-and-wait forager spending most of the time waiting for active prey. However, it sometimes foraged more actively when insect abundance was relatively high. Foraging behavior of males tended to be more variable than females and juveniles. In addition, variation in foraging parameters among individuals was noted. Foraging strategies of G. gecko observed in this study are interpreted in the context of optimal foraging theory.

Snake circumvents constraints on prey size

For animals who are unable to take bites out of their food, the size of the food item that can be consumed is constrained by the maximal size of the mouth opening (gape)--snakes are an example of gape-limited predators and they usually swallow their prey whole. Here we describe unique feeding behaviours in two closely related species of snake, which circumvent their gape limitation by removing and consuming pieces from newly moulted crabs that are too large to be swallowed intact. This evolutionary innovation is surprising, as the needle-like teeth and highly mobile bones that facilitate the capture and engulfment of large, whole prey by snakes are ill-suited both to cutting and to generating large bite forces.

Patterns of Distribution of Two Barnacle Species on the Mangrove Crab, Scylla serrata

Two lepadomorph barnacle species, Octolasmis angulata and O. cor, were commonly found living together in the branchial chambers of the mangrove crab, Scylla serrata. Patterns of distribution are a reflection of cyprid choice at crab ecdysis. Among the 6648 barnacles observed, there were roughly twice as many O. cor as O. angulata (3670 to 1758). The remaining barnacles were indistinguishable as to species and included 1014 immatures, 168 cyprids, and 38 peduncles. The spatial distributions of both O. angulata and O. cor on the gills of Scylla serrata are nonrandom, uneven, and do not reflect available surface area. Both species are distributed differently on the hypobranchial (inside) and epibranchial (outside) surfaces of the gills. Both species are distributed differently on the gills of immature (<70 mm carapace width) and mature (>70 mm) crabs. Our data also show that the distribution patterns vary with different densities. Support is presented for the hypothesis that current flow through the gill chamber may be an important factor influencing site selection by cyprids.

Age of the Mangrove Crab Scylla serrata at Colonization by Stalked Barnacles of the Genus Octolasmis

Cyprid larvae of the lepadomorph Octolasmis colonize the gill chambers of the edible mangrove crab, Scylla serrata (Forskaal, 1755), sometimes in debilitating numbers. We set out to determine when, in the life cycle of the host, barnacle infestation begins. A total of 856 mangrove crabs, ranging in size from 10.9 to 132.3 mm carapace width (instars 5 to 18), were collected from natural populations in Phuket, Thailand, and examined for these barnacles. Almost a third harbored one or more barnacles. The smallest crab to host a barnacle was 34.3 mm (instar 10); 233 smaller crabs, representing instars 5-9, had none. Infestations by more than one barnacle were uncommon among crabs of less than 70 mm carapace width (instar 13). The percentage of crabs hosting barnacles increased as the crabs approached sexual maturity, and the magnitude of infestation on individual crabs increased with their size. The distribution of octolasmids on the gills of immature crabs differed from that on mature crabs. In the former, all barnacles were on the inside of the gill surfaces and none were on the outside, whereas in the latter, 11% were on the outside of the gills. The numbers of barnacles on the inside and the outside of the gills is a function of the number of barnacles in the gill chamber. The major inhalant aperture size, and gill chamber size were eliminated as possible factors limiting infestation. Instars 10 and 11 may be suboptimal for infestation by octolasmids because the intermolt time between instars does not allow sufficient time for production of barnacle nauplii. Current data do not permit us to distinguish the relative influences of microhabitat use, host hormonal changes, and behavioral changes on infestation.

Venom neutralization by rattlesnake serum albumin

The blood serum of the eastern diamond back rattlesnake (Crotalus adamanteus) neutralizes lethal doses of C. adamanteus venom in mice. The protective capacity of the serum is associated with the serum albumin, rather than the immunoglobulin fraction of the blood. Neither the serum nor its albumin fraction form precipitin bands on immunophoresis against venom.