Alvinonemertes dariae, 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 : 153-155

Alvinonemertes dariae gen. et sp. nov.

urn:lsid:zoobank.org:act:D94F4501-3FB4-4F11-8D9E-EB75E20EEB34

Figs 8C–D , 10A–G

Diagnosis

Alvinonemertes dariae gen. et sp. nov. is identified as member of the genus Alvinonemertes gen. nov. based on internal morphology and molecular data. It differs from all other species in the genus by its body coloration and pigmentation. It can be differentiated from A. claudiae gen. et sp. nov. (the only other species with internal data) by the length of the rhynchocoel (⅓ of body length vs whole body), the number of accessory stylets per pouch (2 vs 4-5) and the position of the cerebral organs (alongside brain vs in front of brain).

Etymology

Named for Dr Daria Krämer, acknowledging her contributions to nemertean taxonomy.

Material examined

Holotype

COSTA RICA • ♂ (fixed in formaldehyde and prepared as 23 slides with transverse sections, see cybertype); methane seep Parrita Seep ; 9.03268° N, 84.62127° W; depth 1407 m; 5 Nov. 2018; Jorge Cortés and Drew Bewley leg.; collected by HOV Alvin, Dive 4990; associated with an octocoral identified as Paragorgia Milne Edwards, 1857 ( SIO-BIC Co3054); SIO-BIC N281 (ex SIO-BIC N262).

Paratypes

COSTA RICA • 3 specs (fixed in ethanol); same collection data as for holotype; GenBank : ON186252 , ON036048 , ON021865 ; SIO-BIC N262 • 1 spec. (fixed in ethanol); same collection data as for holotype; MZUCR Nemertea Collection MZUCR-105-01 (ex SIO-BIC N262) .

Cybertype Images of serial sections of holotype: https://doi.org/10.5281/zenodo.5346500.

Description

Specimens 15 mm long and 0.7 mm in diameter. Body flattened. One pair of cephalic furrows. Head not demarcated from rest of body, rounded. Body coloration orange with several red pigment spots distributed over body surface. Internal organs well visible through body wall ( Fig. 8D ).

Epidermis in foregut region 30 µm thick. Body wall composed of two muscle layers (outer circular, inner longitudinal; Fig. 10B ). Esophagus opening subterminally; stomach without pouches ( Fig. 10B, D ); pylorus shorter than stomach; intestinal cecum with unpaired ventral process under stomach; intestine with several lateral pouches ( Fig. 10E ). Excretory system confined to foregut region, canals outside musculature ( Fig. 10D ). Precerebral septum closed. Rhynchocoel wall with two very thin muscle layers (outer circular, inner longitudinal), rhynchocoel approximately ⅓ of body length. Proboscis with outer circular, middle longitudinal, and inner circular muscle layers. Proboscis with central and accessory stylets. Stylet basis circular in cross section, two accessory stylet pouches with two stylets per pouch ( Fig. 10G ). Proboscis nerves not visible. Proboscis pore subterminal, ventral ( Fig. 10A ). Nervous system with thin outer neurilemma, without neurochord cells ( Fig. 10B–C ); dorsal and ventral commissures approximately same size. Lateral nerve cords with accessory nerve ( Fig. 10F ). Cerebral ganglia and lateral nerves in longitudinal muscle layer ( Fig. 10B ). Eyes absent. Cerebral organs less than half the size of brain lobes, alongside brain ( Fig. 10C ). Paired cerebral canal simple, unforked, opens laterally into cephalic furrows ( Fig. 10C ). Apical organ present, unpaired; cephalic glands extending to brain ( Fig. 10A–C ). Blood system consisting of cephalic loop, mid-dorsal vessel not forming vascular plug. Testes sac like, alternating with intestinal diverticula, ventral ( Fig. 10E ). Females unknown.

Ecology

The species seems to occur in close association with octocoral Paragorgia sp. as several nemertean specimens were sampled from one colony ( Fig. 8C ).

Remarks

Alvinonemertes dariae gen. et sp. nov. is attributed to the genus Alvinonemertes gen. nov. based on the executed phylogenetic analyses. In the concatenated analysis, this species is sister to the other four newly described species attributed to the genus Alvinonemertes ( Fig. 7 ).

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. 10. A–G. Alvinonemertes dariae gen. et sp. nov., holotype (SIO-BIC N281), transverse histological sections. H–N. Alvinonemertes claudiae gen. et sp. nov., holotype (SIO-BIC N283), transverse histological sections. A. Anterior tip of head with proboscis pore. B. Brain region. C. Anterior brain region with cerebral canal (arrowhead). D. Stomach region with excretory canal. E. Posterior body region with testes. F. Lateral nerve cord with accessory nerve in stomach region. G. Proboscis armature, accessory stylet pouches with accessory stylets. H. Anterior tip of head with proboscis pore. I. Region anterior to cerebral ganglia with well-visible cerebral canal (arrowhead). J. Anterior brain region. K. Pyloric region. L. Proboscis and mid-dorsal vessel in stomach region. M. Proboscis armature, circular basis of central stylet. N. Proboscis armature, accessory stylet pouches with accessory stylets. Abbreviations: an = accessory nerve; ap = accessory stylet pouch; as = accessory stylet; bl = blood vessel; br = brain; cg = cephalic glands; cm = circular muscle layer; co = cerebral organ; dl = dorsal brain lobe; ec = excretory canal; gd = gonoduct; i = intestine; ic = intestinal cecum; ip = intestinal pouches; lm = longitudinal muscle layer; ln = lateral nerve cord; mv = mid-dorsal vessel; p = proboscis; pe = proboscis epithelium; pp = proboscis pore; py = pylorus; rc = rhynchocoel; rd = rhynchodaeum; sb = stylet basis; st = stomach; t = testis; vl = ventral brain lobe. Scale bars: A–G = 100 µm; H–N = 30 µm.

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.