Adaptations to hydrothermal vent life in Kiwa tyleri, a new species of yeti crab from the East Scotia Ridge, Antarctica

Hydrothermal vents in the Southern Ocean are the physiologically most isolated chemosynthetic environments known. Here, we describe Kiwa tyleri sp. nov., the first species of yeti crab known from the Southern Ocean. Kiwa tyleri belongs to the family Kiwaidae and is the visually dominant macrofauna of two known vent sites situated on the northern and southern segments of the East Scotia Ridge (ESR). The species is known to depend on primary productivity by chemosynthetic bacteria and resides at the warm-eurythermal vent environment for most of its life; its short-range distribution away from vents (few metres) is physiologically constrained by the stable, cold waters of the surrounding Southern Ocean. Kiwa tylerihas been shown to present differential life history adaptations in response to this contrasting thermal environment. Morphological adaptations specific to life in warm-eurythermal waters, as found on – or in close proximity of – vent chimneys, are discussed in comparison with adaptations seen in the other two known members of the family (K. hirsuta, K. puravida), which show a preference for low temperature chemosynthetic environments

The evolution and population genetics of hydrothermal vent megafauna from the Scotia Sea

This project used a variety of genetic markers to investigate the evolution and population genetics of hydrothermal vent fauna that were recovered from the Scotia Sea, in the Atlantic sector of the Southern Ocean. The origins of one of these species, an undescribed species of Kiwa sp. found on the East Scotia Ridge (ESR) and its constituent family Kiwaidae, a group of vent and seep-associated decapod squat lobsters (infraorder Anomura) was investigated using a concatenated nine-gene dataset and key divergences were dated using fossil calibrations. These results confirm earlier research showing Kiwaidae reside in the superfamily Chirostyloidea, but form a monophyletic clade with the non-chemosynthetic family Chirostylidae and not Eumunididae. Chirostyloid families diverged in the Cretaceous, although extant Kiwaidae radiated in the Eocene, consistent with many other chemosynthetic taxa that appear recently derived. The basal tree position of Pacific species (and the Alaska location of a likely stem-lineage kiwaid fossil) suggests kiwaids originated in the East Pacific. Within a Southern Hemisphere clade, the divergence between the southeastern Pacific K. hirsuta and a non-Pacific lineage (Kiwa sp. ESR and Southwest Indian Ridge kiwaids) is no earlier than 25.9 Ma, consistent with a spread from the Pacific into the Scotia Sea and beyond via now-extinct active ridge connections or mediated by a Miocene onset of the Antarctic Circumpolar Current (ACC) through a newly-opened Drake Passage. This project also investigated the population genetics of three undescribed species found at two vent fields ~ 440 km apart at either end of the ESR: Kiwa sp., a peltospirid gastropod and Lepetodrilus sp. limpets. Lepetodrilus sp. was also found at the Kemp Caldera, a submerged part of the South Sandwich Islands (SSI). Analyses of cytochrome c oxidase subunit 1 (COI) as well as microsatellite loci developed from Roche 454 sequence libraries revealed no differentiation along the ESR for all three species consistent with panmixia, or the dominance of non-equilibrium processes between vent field colonies within a metapopulation, possibly enhanced further by cold-induced arrested larval development. Despite apparent connectivity along the ESR, both COI and microsatellites revealed differentiation between ESR limpets and Kemp Caldera limpets ~ 95 km to the east, possibly owing to the hydrographic isolation of the caldera. Both COI and microsatellite diversity patterns were consistent with recent ( These results highlight the role of larval dispersal of vent fauna along active spreading ridges, both in maintaining vent metapopulations across vent colonies prone to stochastic birth and extinction in the short term, but also in the spread of taxa globally and the formation of biogeographic provinces. The likelihood that the three species presented here exist at vents east of the ESR and SSI, prompts further exploration along ridges in the South Atlantic, in order to investigate the effect of the ACC in enhancing gene flow and delineating biogeographic provinces.This thesis is not currently available in ORA

Examples of the differences in assemblages and localities of <i>Kiwa tyleri</i> from the Southern Ocean vent fields.

<p>A) Individual male <i>Kiwa tyleri</i> at the orifice of a "black-smoker" fluid exit on the "Dog's Head" Chimney complex [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127621#pone.0127621.ref001" target="_blank">1</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127621#pone.0127621.ref006" target="_blank">6</a>], E2 vent field; B) Female (left) and male (right) on the lower part of the "Dog's Head" chimney complex; C) "<i>Kiwa B</i>" assemblage (left) adjacent to "<i>Kiwa A</i>" assemblage (right) at the "Black & White" chimney at the E9 vent field; D) "<i>Kiwa B</i>" assemblage "Crab City" at the E2 vent field; E) "<i>Kiwa B</i>" assemblage at the "Black & White" chimney at the E9 vent field; F) Zoomed in section to show the dense multilayer aggregations of the "<i>Kiwa B</i>" assemblage at the "Black & White" chimney, both male and female individuals can be identified from chela dimorphism; G) Small individual <i>Kiwa tyleri</i> associated with the "<i>barnacle assemblage</i>" at the "Black & White" chimney; H) Brooding females away from the influence of direct fluid flow at "Anemone Field" E2 vent field; note: ROV slurp gun visible. Scale bar: 5cm (A,B,C,F,G); Scale bar: 10 cm (E,F,H).</p

<i>Kiwa tyleri</i> sp. nov.; paratype, male (NHMUK 2015.2792).

<p>A) lateral view; C) dorsal view; E) ventral view, sternal plastron; G) dorso-lateral view; holotype, female (NHMUK 2015.2791) B) lateral view; D) dorsal view, F) ventral view, sternal plastron, with gonopore on first segments of pereopod 3 (arrow); note: sternal plastron with remnants of setae (methodological artefact, see methods section); H) paratype, large male (NHMUK 2015.2793) (all images based on micro-focus X-CT).</p

Phylogenetic position of Kiwaidae.

<p>Bayesian inference phylogenetic tree based on 16S and 18S fragments. Strong node support (posterior probability of 1.0) is evident for the monophyly of <i>K</i>. <i>hirsuta</i> and <i>Kiwa tyleri</i> sp. nov.</p

List of Primers used in the study.

<p>List of Primers used in the study.</p

<i>Kiwa tyleri</i> sp. nov.; paratype, large male (NHMUK 2015.2793).

<p>A) lateral view; B) dorsal view; C) frontal view; D) ventral view, sternal plastron; E) dorsal view.</p

Hydrothermal vents on the East Scotia Ridge (ESR).

<p>The Scotia Sea showing the ESR in relation to the Scotia Plate and adjacent plates. Hydrothermal vent sites (E2, E9) as indicated.</p

<i>Kiwa tyleri</i> sp. nov.

<p>A) type material, female, dorsal view; B) type material, male, dorsal view; note presence of single specimen of limpet (<i>Lepetodrillus</i> sp.) on carapace; C) paratype, male (NHMUK 2015.2793) frontal view; D) paratype, male (NHMUK 2015.2793) dorsal view.</p