Abstract
Abstract Keysercythere reticulatasp. nov. and Redekea abyssalissp. nov., collected from the wood fall submerged in the Kuril-Kamchatka Trench (Northwestern Pacific), are only the second records of the naturally occurring, wood-associated ostracod fauna from a depth of over 5000 m. At the same time, K. reticulata is the second and R. abyssalis is the third representative of their respective genera. While Keysercythere Karanovic and Brandão, 2015 species are free-living, deep-sea taxa, all Redekea de Vos, 1953 live symbiotically on the body surface of wood-boring isopods, Limnoria spp. Since R. abyssalis is the only genus representative found in the deep sea, we hypothesize that its ancestor colonized this ecosystem as a result of the symbiotic relationship. Newly collected material enabled us to update molecular phylogeny of Cythreoidea based on 18S rRNA gene sequences, especially to clarify the current systematics of the families Keysercytheridae, Limnocytheridae, and Paradoxostomatidae. The resulting phylogenetic tree supports a close relationship between Keysercythere and Redekea and a distant relationship between two Limnocytheridae lineages, Timiriaseviinae and Limnocytherinae. Consequently, we propose a transfer of Redekea from Paradoxostomatidae to Keysercytheridae, and erecting of the two limnocytherid subfamilies onto the family level. The phylogenetic analysis also implies a close relationship between the nominal Limnocytherinae genus and Keysercythere+Redekea clade, albeit with a low posterior probability, requiring further studies to clarify this.
Highlights
Wood debris is significant natural resource that provides food and habitat for various marine invertebrates whether it is washed ashore or sunk into shallow or deep seafloor
Wood-fall ostracods were first reported by de Vos (1953) who described three cytheroid ostracod species associated with the wood-boring isopod Limnoria lignorum (Rathke, 1799): Aspidoconcha limnoriae de Vos, 1953 and Redekea perpusilla de Vos, 1953 were described from the Netherlands part of the North Sea, while Laocoonella commensalis was described from the Caribbean Sea (Curaçao)
The aim of this study is to describe the two species and update current molecular phylogeny of Cythreoidea based on 18S rRNA gene, especially to clarify the position and systematics of Keysercytheridae, Limnocytheridae, and Paradoxostomatidae
Summary
Wood debris is significant natural resource that provides food and habitat for various marine invertebrates whether it is washed ashore or sunk into shallow or deep seafloor (see review by Schwabe et al 2015). The three genera, Aspidoconcha de Vos, 1953, Redekea de Vos, 1953, and Laocoonella de Vos and Stock, 1956 are members to the families Keysercytheridae (Karanovic and Brandão 2015), Paradoxostomatidae (de Vos and Stock 1956, Wouters and de Grave 1992), and Cytheruridae (McKenzie 1972, Maddocks and Steineck 1987), respectively. They are rare examples of symbiotic lineages in their respective families, because most of their relatives are free-living ostracods. Another ostracod family, Entocytheridae, consists of exclusively symbiotic species, and contains two species, Microsyssitria nhlabane Hart and Clark, 1984 and M. indica Hart, Nair and Hart, 1967, living commensally on the wood-boring isopod Sphaeroma terebrans Bate, 1866 (Hart et al 1967; Hart and Clark 1984)
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