Sea stars from sunken woods Caymanostella scrippscognaticausa, Caymanostella davidalani and Caymanostella loresae

NEWS - Three species of sea stars from specimens collected from sunken woods at several locations along the Pacific margin of Costa Rica and near the Gulf of California (Mexico): Scripps sea star (Caymanostella scrippscognaticausa sp. nov.), David Alan Lewis sea star (Caymanostella davidalani sp. nov.) and Lores López Gómez sea star (Caymanostella loresae sp. nov.)

Caymanostellidae Belyaev 1974 have been found in logs from sinkholes at depths ranging from ~414 m to 6780 m in the Pacific, Atlantic and Indian Oceans. The first described species C. spinimarginata Belyaev 1974 was collected in the Cayman Trench, Caribbean Sea, at depths of 6740-6780 m.

Four species of Caymanostellidae are C. spinimarginata Belyaev 1974, C. admiranda Belyaev & Litvinova 1977, C. phorcynis Rowe 1989 and C. madagascarensis Belyaev & Litvinova 1991 which are morphologically identifiable based on the unique shape and arrangement of the abactinal plates, the shape of the abactinal spinelets, the shape of the madreporite and the position of the gonopores.

However, all specimens reported to date are interpreted as adults and there is no record of earlier life stages. Molecular data for Caymanostellidae are also very limited. Several past studies that have produced molecular phylogenies have relied on different molecular markers and have not included data for all members of the clade.

Researchers on expeditions to the Pacific rim of Costa Rica and the Gulf of California, Mexico, collected specimens of varying sizes found in wood located on seamounts and methane seeps. They analyzed them using molecular and morphological approaches to support the placement of these specimens as new species.

Adult C. scrippscognaticausa has a stellate body. Juveniles pentagonal to subpentagonal. Abactinal plates oval to polygonal shaped with curved margins. Abactinal armament spiniform and sparsely distributed.

Central disc plates of various sizes but similar shapes and imbricating in irregular cycles. One row of dorsal-lateral plates on each side of a row of carinal plates which are less discernible closer to arm base. Terminal plates are square-shaped.

Each inferomarginal plate is larger than adjoining superomarginal plate. Gonopores visible, located in notches at the radial margin of the proximal-most superomarginal plates. Madreporite single pore or slit to complex grooves. Wide, robust adambulacral spines.

This species is only known from the Pacific margin of Costa Rica, confirmed from depths of 990–1010 m and possibly a wider depth range. C. scrippscognaticausa is named after the Scripps Family group “Cousins for Causes” for their generous donation to support research in this study.

C. davidalani has a subpentagonal body. Thin epidermis. Arms broad. Abactinal plates oval to polygonal shaped with curved margin, tightly overlapping. Abactinal armament spiniform and sparsely distributed. Central disc plates imbricate irregularly.

One row of dorsal-lateral plates on each side of a row of carinal plates. Terminal plate rectangular-shaped. Each inferomarginal plate larger than the adjoining superomarginals. Gonopores visible, located in notches at the radial margin of the proximal-most superomarginal plates. Adambulacral spines thorny, narrow and elongated.

This species is known only from the Pacific margin of Costa Rica, 1002–1887 m. C. davidalani is named after David Alan Lewis, in appreciation of his support of marine biodiversity research and the Scripps Institution of Oceanography Benthic Invertebrate Collection.

C. loresae has a pentagonal or subpentagonal body. Thick epidermis. Dense and granuliform abactinal armaments. Central disc plates circular, imbricating irregularly. Gonopores visible, piercing through the proximal-most superomarginal plates. Madreporite with branching grooves.

One row of dorsal-lateral plates on each side of a row of carinal plates until arm tip. Terminal plate slightly trapezoidal. Inferomarginals more elongate than adjoining superomarginals. Short adambulacral spines covered with thick epidermis.

This species is known only from the Tamayo Fracture Zone, Gulf of California (Mexico), at a depth of 3054 m. C. loresae is named after Lores López Gómez in recognition of his unwavering commitment to advancing gender equality and his compassionate sense of justice.

Three new species extend the known distribution of Caymanostellidae into the eastern Pacific Ocean. These species also include the first report of this family, including juvenile specimens, from a fallen tree that occurred near a methane seep.

Phylogenetic analysis is consistent with previous studies regarding the distant relationship between Xyloplax and Caymanostellidae, as well as the placement of Xyloplax within Velatida and Caymanostellidae within Valvatida.

The terminal monophyly of Caymanostellidae is confirmed and restored with strong support, except for the Histone H3 sequence of Caymanostella which is instead resolved as a sister lineage to all valvatids sampled.

The researchers interpret these results as likely the consequence of misidentification. The only available sequence of C. spinimarginata (Taiwanese “Caymanostella spinimarginata”) was obtained from a specimen collected in the Western Pacific, and there are no data for the type locality of this species in the Caribbean Sea.

Without comparison with data on C. spinimarginata from the type locality, the researchers cannot be certain about the identity of this specimen. For the same reason, the taxonomic assignment of other publicly available Caymanostella sequences used in this study remains uncertain as none of them originated from the type locality.

Because of this uncertainty, the taxonomic assignment of the new species to Caymanostella rather than to Crinitostella is ambiguous to some extent, given that C. laguardai is found among the terminal Caymanostella, as a sister group to C. scrippscognaticausa. The conspicuous gonopores are morphologically similar to those in other species of the genus.

Original research

Zihui Shen, Nicolás Mongiardino Koch, Charlotte A. Seid, Ekin Tilic & Greg W. Rouse (2024). Three New Species of Deep-Sea Wood-Associated Sea Stars (Asteroidea: Caymanostellidae) from the Eastern Pacific. Zootaxa 5536 (3): 351–388, DOI:10.11646/zootaxa.5536.3.1

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