Gnosonesima smithi sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act: B4D62E7F-8DF1-4A52-B9BC-463E850837D3

Ocean Census species No. 364

(Fig. 2)

Diagnosis. Species of Gnosonesima unpigmented and without eyes. Male copulatory bulb including a ~96-µm-long, proximally bent stylet, ending in sharp tip. Two ovaries are present. Bursa opening through a posterior vagina.

Etymology. Species named after Prof. Dr Julian Smith III (Winthrop University, North Carolina) due to his extraordinary contribution to the study of microturbellarians.

Material. Two specimens studied alive, one of them whole mounted and designated holotype (USNM 1694166).

Description. The specimens measured 397–460 µm long (x̄ = 429 µm; n = 2), with the anterior end pointing and the posterior broad (Fig. 2A). They were colourless and without eyes. The pharynx (Figs. 2A, 2B: ph) was 149–164 µm long (x̄ = 157 µm; n = 2) and 47–60 µm at its widest posterior point (x̄ = 54 µm; n = 2). The internal pharynx (Figs. 2A, 2B: iph) was 38–41 µm long (x̄ = 40 µm; n = 2) and 26–29 µm at its widest (x̄ = 28 µm; n = 2).

The genital organs were in the mid- to posterior regions of the body. There were two testes (Figs. 2A, 2C: t) connected to a single seminal vesicle (Fig. 2A–C: sv). The seminal vesicle opened in the proximal part of the male bulb, which encloses the prostate vesicle (Fig. 2B–C: pv) and a 91–100-µm-long stylet (x̄ = 96 µm; n = 2). The stylet (Figs. 2A–C: st, 2D–E) is proximally bent and ends in a distal sharp tip. Distally, the walls of the ejaculatory duct appeared slightly sclerotized (Fig. 2C: x). The male accessory organ (Fig. 2A–C: ao) was a short, globular sac that proximally contains a bundle of glands. It lacked the stalk-like connection to the male gonopore observed in some other species. The male gonopore opened at about 50%.

There were two ovovitellaria (Figs. 2A, 2C, 2F–G: ov), which fuse posteriorly, and a bursa (Figs. 2C, 2F–G: b) posterior to the male organs. In one of the specimens, studied only alive, the bursa extended posteriorly and opened subterminally through a vagina (2F–G: va); in the second specimen (holotype) the vagina was not observed. The female gonopore (Fig. 2C: fg) opened at about 80%.