Tetranemertes unistriata, 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 unistriata sp. nov.

Fig. 7

Diagnosis.

Tetranemertes unistriata sp. nov. differs from most other described species of the genus by its color pattern: a single pale to dark pink mid-dorsal longitudinal stripe on a pale yellow to pale pinkish background. Resembles T. rubrolineata from Madagascar ( Kirsteuer 1965) in body color. Although tissue for DNA analysis is not available for T. rubrolineata from Madagascar, DNA sequences from individuals collected by SAM from the Arabian Sea and identified as T. rubrolineata clearly separate the two species. DNA barcodes of T. unistriata sp. nov. are also clearly distinct from those of all other sequenced species of the genus (Table 5 ).

Material examined.

Type material in the form of histological sections and tissue in 95% ethanol is deposited with the Smithsonian Institution’s National Museum of Natural History. Holotype: 490_071099_2 (USNM 1011574), paratype 490_070999_1 (USNM 1011573). Additional specimens, accession numbers, and collecting information can be found in Tables 1 , 2 .

Description.

External appearance of live specimens. Body thin, thread-like, a few centimeters in length, and less than a millimeter in width. Anterior and posterior ends are gently tapering, bluntly rounded. Color in life varies from pale yellowish orange to pale pink, with a continuous thin reddish or dark pink mid-dorsal longitudinal stripe that reaches from anterior to posterior tip of body (Fig. 7A ). Head the same width or slightly narrower than the rest of body, demarcated from the rest of body by a pair of ventral anterior cephalic furrows, nearly fused mid-ventrally to form a shallow anteriorly pointed “V” (Fig. 7B ). Rhynchostomopore appears as a short ventral slit, at the anterior tip of head. Small dark ocelli (9-12 on each side of head) are arranged in four longitudinal rows, the two rows on each side of head almost directly on top of one another (Fig. 7D, E ). The smaller individual from Oman had fewer ocelli (Fig. 7G, I ). Cerebral ganglia large, yellowish or pinkish, partly translucent, show through the body wall (Fig. 7D, E, G ). Cerebral organs small, inconspicuous.

Rhynchocoel and proboscis. Rhynchocoel length unknown, but likely restricted to anterior-most region of body. Proboscis short and thin. Stylets were examined in one ~ 8-cm long individual (paratype) from Japan, and the ~ 2 cm long individual from Oman. Central stylet with a straight spirally sculpted shaft, 20-50 μm long. Basis cylindrical, deeply forked posteriorly, 25-75 μm long (Fig. 7E ). Two accessory stylet pouches with 2 stylets each. Smaller individual from Oman had considerably smaller stylets and smaller cylindrical basis, rounded posteriorly (Fig. 7H ).

Reproduction. No data.

Habitat.

Free-living, marine. Among brown and branched calcareous algae at the depths of 1-2 m in the type locality in Japan. Among coral rubble at 4-9 m depths in Oman.

Geographic distribution.

Type locality is near Seto Marine Laboratory on the Pacific coast of Honshu Island, Japan. One other individual was collected by SAM in the Arabian Sea (Dhofar Governorate, Oman).

Etymology.

Specific epithet reflects the color pattern of living individuals.

Figures

Figure 7. Tetranemertes unistriata sp. nov. A-E based on sketches from live material (individuals 490 _ 070999 _ 1 through 490 _ 070999 _ 3) from Japan A external appearance in life B diagram of head in ventro-lateral view showing cephalic furrow C stylet and basis D, E anterior end in dorsal (D) and lateral (E) views showing number and arrangement of eyes, and cerebral ganglia E stylet and basis F, G appearance in life of individual BOMAN- 07032 from Oman: body shape (F), anterior end in incident light (G) showing size and position of cerebral ganglia and eyes, stylet apparatus (H), and compressed head region in transmitted light to show eye arrangement (I). Abbreviations: cf - cephalic furrow, cg - cerebral ganglion. Scale bars: 1 cm (A); 50 μm (C); 5 mm (F); 1 mm (G); 40 μm (H); 150 μm (I).