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Eiji Shimizu - One of the best experts on this subject based on the ideXlab platform.

Harvey B. Lillywhite - One of the best experts on this subject based on the ideXlab platform.

  • structure and function of skin in the pelagic Sea Snake hydrophis platurus
    Journal of Morphology, 2019
    Co-Authors: Harvey B. Lillywhite, Gopinathan K Menon
    Abstract:

    We describe and interpret the functional morphology of skin of the Yellow-bellied Sea Snake, Hydrophis platurus. This is the only pelagic Sea Snake, and its integument differs from what is known for other species of Snakes. In gross appearance, the scales of H. platurus consist of non-overlapping, polygonal knobs with flattened outer surfaces bearing presumptive filamentous sensillae. The deep recesses between scales ('hinge') entrap and wick water over the body surface, with mean retention of 5.1 g/cm of skin surface, similar to that determined previously for the roughened, spiny skin of marine file Snakes, Acrochordus granulatus. This feature possibly serves to maintain the skin wet when the dorsal body protrudes above water while floating on calm oceanic slicks where they forage. In contrast with other Snakes, including three species of amphibious, semi-marine Sea kraits (Laticauda spp.), the outer corneous β-protein layer consists of a syncytium that is thinner than seen in most other species. The subjacent α-layer is also thin, and lipid droplets and lamellar bodies are seen among the immature, cornifying α-cells. A characteristic mesos layer, comprising the water permeability barrier, is either absent or very thin. These features are possibly related to (1) permeability requirements for cutaneous gas exchange, (2) reduced gradient for water efflux compared with terrestrial environments, (3) less need for physical protection in water compared with terrestrial ground environments, and (4) increased frequency of ecdysis thought to be an anti-fouling mechanism. The lipogenic features of the α-layer possibly compensate for the reduced or absent mesos layer, or produce layers of cells that comprise what functionally might be termed a mesos layer, but where the organization of barrier lipids nonetheless appears less robust than what is characteristically seen in squamates.

  • oceanic circulation models help to predict global biogeography of pelagic yellow bellied Sea Snake
    Biology Letters, 2016
    Co-Authors: François Brischoux, Cédric Cotté, Harvey B. Lillywhite, Frédéric Bailleul, Maxime Lalire, Philippe Gaspar
    Abstract:

    It is well recognized that most marine vertebrates, and especially tetrapods, precisely orient and actively move in apparently homogeneous oceanic environments. Here, we investigate the presumptive role of oceanic currents in biogeographic patterns observed in a secondarily marine tetrapod, the yellow-bellied Sea Snake ( Hydrophis [ Pelamis ] platurus ). State-of-the-art world ocean circulation models show how H. platurus , the only pelagic species of Sea Snake, can potentially exploit oceanic currents to disperse and maintain population mixing between localities that spread over two-thirds of the Earth's circumference. The very close association of these Snakes with surface currents seems to provide a highly efficient dispersal mechanism that allowed this species to range extensively and relatively quickly well beyond the central Indo-Pacific area, the centre of origin, abundance and diversity of Sea Snakes. Our results further suggest that the pan-oceanic population of this species must be extraordinarily large.

  • Oceanic circulation models help to predict global biogeography of pelagic yellowbellied Sea Snake
    Biology Letters, 2016
    Co-Authors: François Brischoux, Cédric Cotté, Harvey B. Lillywhite, Frédéric Bailleul, Maxime Lalire, Philippe Gaspar
    Abstract:

    It is well recognized that most marine vertebrates, and especially tetrapods,precisely orient and actively move in apparently homogeneous oceanic environments. Here, we investigate the presumptive role of oceanic currents in biogeographic patterns observed in a secondarily marine tetrapod, the yellow-bellied Sea Snake (Hydrophis [Pelamis] platurus). State-of-the-art world ocean circulation models show how H. platurus, the only pelagic species of Sea Snake, can potentially exploit oceanic currents to disperse and maintain population mixing between localities that spread over two-thirds of the Earth’s circumference. The very close association of these Snakes with surface currents seems to provide a highly efficient dispersal mechanism that allowed this species to range extensively and relatively quickly well beyond the central Indo-Pacific area, the centre of origin, abundance and diversity of Sea Snakes. Our results further suggest that the pan-oceanic population of this species must be extraordinarily large.

  • On the Abundance of a Pelagic Sea Snake
    Journal of Herpetology, 2015
    Co-Authors: Harvey B. Lillywhite, François Brischoux, Coleman M. Sheehy, Joseph B. Pfaller
    Abstract:

    Abstract We quantified the abundance of pelagic Sea Snakes, Hydrophis (= Pelamis) platurus, while following slicks that formed drift lines during 3 yr of reSearch in the Golfo de Papagayo, Costa Rica. The number of Snakes we observed floating on slicks varied greatly and ranged from 0 to 1,029 per hour. The largest number we observed was highly unusual in recent experience but comparable to earlier reports of Sea Snake aggregations in the historical literature. Snakes were more abundant on slicks with flotsam during early morning hours on clear, calm days. However, ‘decisions' of Sea Snakes to spend time floating on slicks are also influenced by other factors that are not known or are poorly understood. Neither temperature nor salinity influenced the number of Snakes we observed within the range of the parameters we encountered. We observed only a single Snake during 13 days of Searching during which there were red tide conditions with cold and turbid water disturbed almost daily by high winds. We also co...

  • preliminary insights into the phylogeography of the yellow bellied Sea Snake pelamis platurus
    Integrative and Comparative Biology, 2012
    Co-Authors: Coleman M. Sheehy, Joseph B. Pfaller, Alejandro Solorzano, Harvey B. Lillywhite
    Abstract:

    The yellow-bellied Sea Snake, Pelamis platurus (Elapidae, Hydrophiinae), has the largest distribution of any Snake species, and patterns related to its distribution and regional color variation suggest there is population structuring in this species. Here, we use mitochondrial (ND4, Cyt-b) and nuclear (RAG-1) DNA to (1) test whether genetic variation is associated with local variation in color pattern, and (2) assess whether large-scale patterns of genetic variation are correlated with geographic distribution across the Pacific Ocean. We found low levels of genetic variation and shallow population structure that are correlated with local variation in color pattern and with geographic distribution. The low levels of genetic divergence indicate a relatively high rate of gene flow throughout the Pacific region and/or a recent expansion of range, both of which could be attributable to the passive drifting of these Snakes on oceanic surface currents. The mtDNA data conform closely to a model of past exponential population growth, and this may have been associated with the species' large eastward and westward expansion of range. The pattern of low nucleotide and high haplotype diversity suggests that this population growth occurred in the relatively recent past. Data from drifting buoys can potentially act as informative models for predicting patterns of drifting in Pelamis and for generating additional testable hypotheses relating to its population structure and biogeography. Future studies should employ nuclear microsatellite markers to investigate population structure in this species at a finer scale. The exploitation of oceanic currents as a novel and highly efficient dispersal mechanism has likely facilitated gene flow throughout the Pacific Ocean in this uniquely pelagic species of Sea Snake, resulting in a distribution spanning over half of the earth's circumference.

Hiramitsu Suzuki - One of the best experts on this subject based on the ideXlab platform.

Nobuya Shirai - One of the best experts on this subject based on the ideXlab platform.

Tomoyuki Higuchi - One of the best experts on this subject based on the ideXlab platform.