Tetranemertes arabica, Cherneva & Ellison & Zattara & Norenburg & Schwartz & Junoy & Maslakova, 2023

Cherneva, Irina, Ellison, Christina I., Zattara, Eduardo E., Norenburg, Jon L., Schwartz, Megan L., Junoy, Juan & Maslakova, Svetlana A., 2023, Seven new species of Tetranemertes Chernyshev, 1992 (Monostilifera, Hoplonemertea, Nemertea) from the Caribbean Sea, western Pacific, and Arabian Sea, and revision of the genus, ZooKeys 1181, pp. 167-200 : 167

Tetranemertes arabica sp. nov.

Fig. 9D-F

Diagnosis.

Pink body color distinguishes T. arabica sp. nov. from T. bifrost sp. nov., T. rubrolineata , T. unistriata sp. nov., T. ocelata sp. nov., T. pastafariensis sp. nov., and T. paulayi sp. nov. It differs from T. antonina and T. hermaphroditica by having a basis posteriorly bilobed, stylet spirally sculpted. It most resembles T. majinbuui sp. nov. from which it is widely separated geographically. It is currently unknown whether it has separate sexes; if so, then it would distinguish it from T. hermaphroditica , a simultaneous hermaphrodite. DNA barcodes characterize this species unambiguously, clearly differentiating it from all other sequenced species of the genus (Table 5 ).

Material examined.

Type material is deposited with the Florida Museum of Natural History. Holotype BOMAN_08050 (UFID 1087), in the form of anterior and posterior preserved for histology, and midbody in 95% ethanol, and paratype BOMAN_08300 (UFID 1085) in the form of anterior and posterior preserved for histology, and midbody in 95% ethanol. See Table 1 for additional specimens, accession numbers, and Table 2 for collecting information.

Description.

External appearance of live specimens. Body is pale to deep pink. Larger individuals have deeper coloration. Pink specks scattered throughout epidermis, as well in the stylet region of the proboscis. Body long and thin, thread-like, widest at the level of the cerebral ganglia and cephalic furrow (Fig. 9D ). Anterior end is least pigmented, semi-translucent. Eyes (25-35) are arranged in four longitudinal rows, two rows on top of each other on either side of head. Anterior tip of head bluntly rounded. A single ventro-lateral cephalic furrow is in front of cerebral ganglia, shaped as a shallow anteriorly directed “V” (Fig. 9F ). Posterior cephalic furrow is lacking.

Rhynchocoel and proboscis. Rhynchocoel and proboscis very short (<1/3 body length), with stylets found within the anterior-most quarter of the body. All examined individuals (n = 8) possessed a posteriorly forked basis and spirally sculpted stylets (Fig. 9E ).

Reproduction. Ripe males observed in January 2022.

Habitat.

Coral rubble, shell hash, rocks encrusted with coralline algae and vermetid tubes; between the depths of 2-30 m.

Geographic distribution.

Currently only known from the Arabian Sea (Mirbat, Dhofar Governorate, Oman).

Etymology.

Species epithet refers to the type region of the species, the Arabian Sea (and the coast of the Arabian Peninsula).

Figures

Figure 9. Tetranemertes arabica sp. nov. and Tetranemertes paulayi sp. nov. from the Arabian Sea (Oman), and Tetranemertes sp. ETP 001 from Eastern Tropical Pacific A-C Tetranemertes paulayi. Individual BOMAN- 07013, holotype, external appearance in life (A), and head compressed under coverglass (B) to show number and arrangement of eyes, and cephalic furrow (arrowhead). Note orange blood vessels (inset, and white arrowheads). Individual BOMAN- 08291, paratype (C), stylets, viewed through the body wall of an individual compressed under coverglass (hence the orange tinge), inset emphasizes sculpted stylets (individual BOMAN- 08302) D-F Tetranemertes arabica. Individual BOMAN- 09099, external appearance in life (D), proboscis armature (E). Inset on E shows sculpted stylets (individual BOMAN- 08030). Individual BOMAN- 08050, head compressed under coverslip to show arrangement of eyes (F). Note the pink tinge to the body wall and proboscis wall, and orangish cerebral ganglia G Tetranemertes sp. ETP 001 from the Pacific coast of Panama (individual SMPP 0632). Scale bars: 3 mm (A); 0.2 mm (B, F); 50 μm (C and insets on C, E); 100 μm (E); 2 mm (D); 0.5 mm (G).