Category: Biogeography

Indian Ocean vent stalked barnacle gets a name

A new co-authored paper published in Royal Society Open Science led by Hiromi Kayama Watanabe describes a new species of deep-sea stalked barnacle from Indian Ocean hydrothermal vents: Neolepas marisindica Watanabe, Chen & Chan in Watanabe et al., 2018. Furthermore, we also carried out phylogeographic investigation of deep-sea eolepadid stalked barnacles, leading to a better understanding of their evolution and biogeography. The paper is Open Access and available here: http://rsos.royalsocietypublishing.org/content/5/4/172408

 Abstract
Phylogeography of animals provides clues to processes governing their evolution and diversification. The Indian Ocean has been hypothesized as a ‘dispersal corridor’ connecting hydrothermal vent fauna of Atlantic and Pacific oceans. Stalked barnacles of the family Eolepadidae are common associates of deep-sea vents in Southern, Pacific and Indian oceans, and the family is an ideal group for testing this hypothesis. Here, we describe Neolepas marisindica sp. nov. from the Indian Ocean, distinguished from N. zevinae and N. rapanuii by having a tridentoid mandible in which the second tooth lacks small elongated teeth. Morphological variations suggest that environmental differences result in phenotypic plasticity in the capitulum and scales on the peduncle in eolepadids. We suggest that diagnostic characters in Eolepadidae should be based mainly on more reliable arthropodal characters and DNA barcoding, while the plate arrangement should be used carefully with their intraspecific variation in mind. We show morphologically that Neolepas specimens collected from the South West Indian Ridge, the South East Indian Ridge and the Central Indian Ridge belong to the new species. Molecular phylogeny and fossil evidence indicated that Neolepas migrated from the southern Pacific to the Indian Ocean through the Southern Ocean, providing key evidence against the ‘dispersal corridor’ hypothesis. Exploration of the South East Indian Ridge is urgently required to understand vent biogeography in the Indian Ocean.

Neolepas marisindica, Paratype specimens and in situ photographs

  • Watanabe HK*, Chen C, Marie DP, Takai K, Fujikura K, Chan BKK* (2018). Phylogeography of hydrothermal vent stalked barnacles: a new species fills a gap in the Indian Ocean ‘dispersal corridor’ hypothesis. Royal Society Open Science, 5: 172408. DOI: 10.1098/rsos.172408

New paper on diversity of Mollusca at a shallow vent

Lead-authored paper on shallow water hydrothermal vent molluscs published in journal Marine Biodiversity! Read online for free here: http://rdcu.be/wKVR

Mar Biodiv, doi:10.1007/s12526-017-0804-2

This paper reports diversity of molluscs inhabiting shallow water (10-30m deep only!) hydrothermal vent ecosystem off Kueishan Island, Taiwan. Unlike deep-sea hydrothermal vents no endemic molluscs were found, and the species present were a subset of species present in surrounding areas that are apprently able to tolerate the ‘extreme’ environment. We report a total of 13 core species including 12 gastropods and one chiton, and discuss their ecology at the shallow vents.

Representative specimens of the 13 mollusc species collected from shallow hydrothermal vents off Kueishan Island, Taiwan

New paper on a chiton ‘cryptic species complex’ published!

New paper dealing with a ‘cryptic species complex’ of polyplacophoran molluscs (chitons) published in Marine Biodiversity! Open access, please read here: http://bit.ly/2okQQ56

In this work, we present a case study of a total-evidence approach to resolving difficult and perplexing ‘cryptic species complexes’. A Pacific shallow water chiton Leptochiton rugatus (Carpenter in Pilsbry, 1892) is supposed to have a very wide range from Japan to Baja California, but has been previously suggested to comprise several cryptic species. Our genetic haplotype network using specimens across the range revealed four discrete clusters. Most strikingly, the haplotype of L. rugatus sensu stricto (California to Baja California) was very different in structure from that of the cluster ranging from the panhandle of Alaska to Oregon. The latter was found to have extremely high side fidelity and patchy distribution, and we present evidence that it is likely a brooder. The difference in life-history strategies between these two clusters account for the differences in their genetic structure. Although morphological differences were observed, these were minor and insufficient to guarantee each as species-level lineages alone. Only with the difference in life-history strategy could they be confidently recognised as separate species, the latter we described as L. cascadiensis sp. nov. after the Cascadia costal bioregion which it inhabits.

L. cascadiensis harbouring putative eggs in the pallial cavity

Things without names are difficult to rationalise, and are difficult to conserve; assigning names to species is therefore critical to understanding and conserving biodiversity. This study shows that combining evidence from molecules, morphology, and importantly life-history, is key to untangling ‘cryptic species complexes’ which have become increasingly discovered in the recent years. The take-home message: if you want to solve cryptic species problems, don’t forget to look at their way of life!

This is my first time getting involved with describing a chiton, yay! Chitons are awesome.

Sigwart JD, Chen C (2017). Brooding behaviour explains patchy distribution in a shallow-water invertebrate (Mollusca: Polyplacophora: Lepidopleurida). Marine Biodiversity, First Online, DOI: 10.1007/s12526-017-0688-1