Tetrastemma polyakovae, Sagorny & Döhren & Rouse & Tilic, 2022

Sagorny, Christina, Döhren, Jörn von, Rouse, Greg W. & Tilic, Ekin, 2022, Cutting the ribbon: bathyal Nemertea from seeps along the Costa Rica margin, with descriptions of 2 new genera and 9 new species, European Journal of Taxonomy 845 (1), pp. 132-174 : 161-162

Tetrastemma polyakovae sp. nov.

urn:lsid:zoobank.org:act:0A69EED8-5057-4882-A12C-AB4FC69B7B63

Fig. 8M–N

Diagnosis

Tetrastemma polyakovae sp. nov. can be attributed to the genus Tetrastemma based on the strong support for a sister group relationship between the three species of this genus included in the analysis.

Etymology

For Dr Neonila E. Polyakova, in recognition of her contributions to the study of deep-sea nemerteans.

Material examined

Holotype COSTA RICA • spec. (ethanol); methane seep Mound 12; 8.93030° N, 84.31260° W; depth 997 m; 24 Oct. 2018; Jorge Cortés and Oliver Ashford leg.; collected by HOV Alvin, Dive 4978; GenBank: ON186259 , ON036056 , ON021857 , ON182051 ; SIO-BIC N258.

Paratype COSTA RICA • 1 spec. (ethanol; entirely used up in DNA extraction; only image and DNA available); same collection data as for holotype; 8.93° N, 84.31° W; depth 996–999 m; GenBank: ON036057 , ON021858 , ON182050 ; MZUCR Nemertea Collection MZUCR-101-01 (ex SIO-BIC N 255) .

Description

Specimens 15 mm long and 1 mm in diameter. Body rounded. Two pairs of cephalic furrows. Head not demarcated from rest of body, rounded. Body coloration pale orange to brownish. Internal organs well visible through body wall ( Fig. 8M–N ).

Remarks

The new species is attributed to the genus Tetrastemma based on the executed phylogenetic analyses. This species is sister to Tetrastemma strandae sp. nov. ( Fig. 7 ). Intraspecific pairwise p-distances are 2%, whereas interspecific distances between T. polyakovae sp. nov. and the two newly described species vary between 7% and 8%. Distance between this species and Tetrastemma stimpsoni is 12.5%.

Figures

Fig. 8. Live images of eumonostiliferous hoplonemerteans collected along the Costa Rica margin and the NE Pacific. A. Chernyshevia escarpiaphila sp. nov., paratype (SIO-BIC N112). B. Chernyshevia escarpiaphila sp. nov., paratype (SIO-BIC N266). C. Octocoral Paragorgia sp. (SIO-BIC Co3054) with several specimens of Alvinonemertes dariae sp. nov., holotype (arrows; ex SIO-BIC N262). D. Alvinonemertesdariaesp.nov.,holotype(exSIO-BICN262).E.Antipathariancoral(SIO-BICCo3031) with specimens of Alvinonemertes dagmarae sp. nov., holotype (SIO-BIC N260). F. Alvinonemertes christianeae sp. nov., holotype (SIO-BIC N253). G. Alvinonemertes claudiae sp. nov., holotype (ex SIO-BIC N231). H. Alvinonemertes tatjanae sp. nov., holotype (SIO-BIC N119). I. Eumonostilifera (SIO-BIC N259). J–L. Tetrastemma sundbergi sp. nov., holotype (SIO-BIC N256) whole animal (J), dorsal view of head (K), and ventral view of head (L). M. Tetrastemma polyakovae sp. nov. (MZUCR Nemertea Collection MZUCR-101-01).N. Tetrastemma polyakovae sp. nov., holotype (SIO-BIC N258), with everted proboscis. O. Eumonostilifera (SIO-BIC N109).

Fig. 7. Maximum likelihood (ML) tree for the monostiliferan supermatrix based on the concatenated four gene dataset (16S, COI, 18S, H3). Black circles indicate nodal support of 100/100/1.0; asterisks indicate nodal support of either 100/ or /1.0. Alternative branches found in the BI analysis are given as blue dotted lines. Sonnenemertes cantelli Chernyshev, Abukawa & Kajihara, 2015 and Micrura callima Sundberg & Gibson, 1995 were used for outgroup rooting. Specimens belonging to new species are given in bold. Specimen-ID, sampling locality, and depth (for deep-sea species) are provided.