Reinhardorhynchus hexacornutus Jouk, Diez, Reygel & Artois sp. n.

(Fig. 11)

urn:lsid:zoobank.org:act: 45A01032-0A38-4976-9AF0-B2C6F277FC55

Material and distribution. Observations on live specimens, whole mounted afterwards. Five whole mounts, one

of which is designated holotype (FMNH https://id.luomus.fi/ KV.650), the others in HU (XIII.4.16– XIII.4.19), collected in Puna’auia (17°36’42”S; 149°36’51”W) (Type Locality), Pape’ete, Tahiti, Society Islands, French Polynesia (March 18, 2016), sediment with ripple marks, 50 cm deep, fine black sand .

Etymology. Species named after the presence of six hooks within the copulatory bulb.

Diagnosis. Species of Reinhardorhynchus gen. n. with the copulatory bulb encompassing the ejaculatory duct, a papillary cirrus, and six hooks. Ejaculatory duct runs through the copulatory bulb and opens distally into the male atrium. Papillary cirrus ±84 μm long, armed with nail-shaped spines, ±2 μm long proximally and ±1.2 μm distally. Hooks funnel-shaped, curved, and ending in a sharp tip, each of different size, ranging from 11μm long and 5 μm wide to 54 µm long and 23 µm wide.

Description. The specimens are 0.9–1.3 mm long (x̄ = 1.1 mm; n = 3), translucent, with a pair of eyes (Fig. 11A: e). The proboscis (Fig. 11A: pr) is of the typical koinocystidid construction (see Brunet 1972; Karling 1980), with a strong juncture sphincter. The pharynx (Fig. 11A: ph) has a diameter of 10% of the body length in live specimens, and is located at 30%.

Two testes (Fig. 11A: t) are positioned behind the pharynx. The vasa deferentia form the seminal vesicles (Fig. 11A–B: sv), which fuse to form a short seminal duct just before entering the copulatory bulb. The oval copulatory bulb is 125 μm long (n = 1) and encompasses the ejaculatory duct, a papillary cirrus, and six accessory hooks. The ejaculatory duct (Fig. 11B & 11J: ed) runs through the proximal part of the copulatory bulb and opens distally into the male atrium. The spiny part of the papillary cirrus (Fig. 11A–C & 11J–H: pc) is 73–91 μm long (x̄ = 84 μm; n = 4) and armed with nail-shaped spines. Proximally, these spines are 1.2–2.4 μm long (x̄ = 2 μm; n = 20) and dis- tally they decrease in size to ±1.2 μm (n = 15). Proximally, the papillary cirrus is enclosed in a papilla (Fig. 11A–C & 11J–K: pa), with a glandular organ opening into the cirrus. The accessory hooks (Fig. 11A: h, 11B & 11J–K: h1–h6, 11D–I) are funnel-shaped, curved, and ending in a sharp tip. They differ in size, ranging from 11 µm long and 5 µm wide at the base for the smallest one to 54 μm long and 23 µm wide for the largest one. The hooks are organised in two groups; one group is formed by hooks 1–4 (Fig. 11I, 11G, 11D & 11H, respectively) and the other group includes hooks 5–6 (Fig. 11F & 11E, respectively). The hooks 1–4 are located in a well-developed muscular sac.

The vitellaria (Fig. 11A: vi) extend along both sides of the body from the level of the pharynx to the copulatory organs. A pair of ovaries (Fig. 11A: ov) is located at the midbody, rostral to the copulatory bulb. The oocytes are organised in a row. The oviducts open into the proximal end of the female duct. The female duct (Fig. 11A: fd) opens into the female atrium through a strong sphincter. The muscular bursal stalk (Fig. 11A: bs) connects the caudallylocated bursa (Fig. 11A: b) to the female atrium. The common gonopore (Fig. 11A: cg) opens at 80%.