Cheliplana subproximalis Diez & Reygel & Artois 2019, sp. n.

Cheliplana subproximalis sp. n.

(Fig. 5)

http://zoobank.org/ urn:lsid:zoobank.org:act: 2FEAA7C3-F447-4B35-8FC7-7DD2FBAB3C6D

Material. Observations on live animals, whole mounted afterwards. Two whole mounts from Bueycabón (type locality) (November 18, 2018), one of which is designated holotype (FMNH https://id.luomus.fi/KV.611), the other one reference material (HU X.1.06), intertidal, upper 10 cm of the fine-grained sand, salinity 31 ‰. One whole mount from Las Sardinas (June 22, 2016), intertidal, upper 10 cm of fine-grained sand, salinity 33 ‰ (HU X.1.07).

Etymology. The epithet refers to the fact that the seminal duct opens into de copulatory bulb, a little bit distally from the latter’s proximal end.

Diagnosis. Species of Cheliplana with proboscis hooks 16 µm long and muscular hook supports 7 µm long. Seminal duct opens into the copulatory bulb, subterminally at the latter’s proximal end. At the same level, two separate ducts of unknown origin enter the prostate vesicle. The copulatory bulb ends in a sclerotized cap 16 µm long, which is asymmetrical distally. The spiny cirrus is 48 µm long. It is a narrow tube, widening slightly at the level of the distal cap. The spines are 3 µm long distally and 0.5 µm long in the widened part.

Description. Animals 0.4–0.7 mm long (x = 0.5 mm; n = 3), measured on the whole mounts, translucent, pinkish coloured, without eyes. Proboscis (Fig. 5A: pr, 5B) with curved hooks 13–18 µm long (x = 16 µm; n = 4); muscular hook supports 5–8 µm long (x = 7 µm; n = 4). Pharynx (Fig. 5A: ph) 1/7–1/8 of the body length in live animals. Pharynx connects to the mouth via a long spiny prepharyngeal cavity (Fig. 5A: pph), twice as long as the pharynx. Mouth (Fig. 5A: m) opens ventrally, subterminally at the anterior body end.

Testis (Fig. 5A: t) located postero-laterally from the pharynx, connected to two seminal vesicles. Seminal vesicles (Fig. 5A; C–E: sv) and atrial organs located in the last fourth of the body. Seminal vesicles distally fused to form a short seminal duct (Fig. 5C: sd). Seminal duct opens into the copulatory bulb a bit distally from the latter’s proximal end. The copulatory bulb (Fig. 5 C–E) comprises the prostate vesicle and the spiny cirrus. Prostate vesicle (Fig. 5A & 5 C–E: pv) with two proximal ducts (Fig. 5C & 5E: x), which enter the vesicle at the level of the entrance of the seminal duct. It is not clear where exactly these ducts come from (gland necks of the prostate glands?). Distally, the copulatory bulb ends in a sclerotized cap (Fig. 5 C–E: sc). Sclerotized cap distally asymmetric, 10–20 µm long (x = 16 µm; n = 3) and 6–10 µm at its widest point (x = 8 µm; n = 3). Spiny cirrus (Fig. 5A, 5C & 5E: ci) 62–66 µm long (x = 64 µm; n = 2; measured from the most proximal spines to the most distal tip). In the distal portion of the cirrus, the cirrus widens a bit and the spines are 2–3 µm long (x = 3 µm; n = 12). In this part it is surrounded by a sclerotized cap. Proximally from this part, spines are very fine and less distinguishable, about 0.5 µm long.

The vitellarium (Fig. 5A: vi) extends between the pharynx and the copulatory bulb. Kidney-shaped ovary (Fig. 5A: ov) (with the oocytes in a row, diminishing in diameter from the most distal one to the most proximal one) and bursa located caudally from the common gonopore.