Reinhardorhynchus tahitiensis Jouk, Diez, Yurduseven, Reygel & Artois, 2021

Diez, Yander L., Monnens, Marlies, Aguirre, Rosa Isabel, Yurduseven, Rana, Jouk, Philippe, Van Steenkiste, Niels W. L., Leander, Brian S., Schockaert, Ernest, Reygel, Patrick, Smeets, Karen & Artois, Tom, 2021, Taxonomy and phylogeny of Koinocystididae (Platyhelminthes, Kalyptorhynchia) with the description of three new genera and twelve new species, Zootaxa 4948 (4), pp. 451-500 : 480-482

Reinhardorhynchus tahitiensis Jouk, Diez, Yurduseven, Reygel & Artois sp. n.

( Fig. 15 )

urn:lsid:zoobank.org:act:EBAAD8FF-E519-48FE-8846-20693BD0C5A3

Material and distribution. Observations on live specimens. Three whole mounts, one of which designated holotype ( FMNH https://id.luomus.fi/ KV.652), from Puna’auia (17°38’15”S; 149°36’47”W) (Type Locality), Pape’ete , Tahiti , Society Islands , French Polynesia (March 20, 2016), in front of the Méridien Hotel , sandy beach in front of coral heads with strong periodic currents, fine sand with detritus, about 0.5 m deep. Another whole mount from the same locality (March 1, 2016), in mixed sand with shell gravel, 1 m deep. Two serially-sectioned specimens from the type locality (October 3, 2017), 100 m from the seafront, sand patch in between coral heads, medium grained sand with some coral debris, 1.5 m deep. Three whole mounts from Avatoru , Rangiroa (14°58’48”S; 147°37’25”W), Tuamotu Archipelago, French Polynesia (March 7, 2016), second harbour, fine sand with detritus, 1.5 m deep. All the reference material deposited in HU ( XIII.4.20– XIII.4.27) .

Etymology. Species named after Tahiti, where most of the specimens were found.

Diagnosis. Species of Reinhardorhynchus gen. n. with the copulatory bulb encompassing the prostate vesicle, an armed cirrus and two distal hooks. Cirrus armed with four rows of triangular, ±3-μm-long spines. Rows ±93 μm, ±96 μm, ±41 μm, and ±49 μm long respectively. Longest two rows end in curved spines, which increase in length from the most proximal one (±6 μm long) to the most distal one (±27 μm long). Hooks ±24 μm long and ±18 μm wide at their base, ending bluntly with a very small, sharp tip directed sideways.

Description. The specimens are 1.1–1.3 mm long (x̄ = 1.2 mm; n = 4), yellowish, with two eyes. Habitus and general organisation as in R. riae sp. n. The epidermis is 6 μm thick. Rhabdites, 7–9 μm long, more numerous in the posterior 2/3 of the specimen, deeply embedded within the epidermis. Some rhabdites stain pinkish, others yellowish. At the distal end, caudal glands are present ( Fig. 15A : cgl).

The proboscis ( Fig. 15A : pr) is of the typical koinocystidid construction (see Brunet 1972; Karling 1980). It represents 10% of the body length and has the same detailed morphology as that of R. riae sp. n.; see above. Only two kinds of glands open through the caudal wall of the proboscis: coarse-grained basophilic glands and fine-grained eosinophilic ones.

The pharynx ( Fig. 15A : ph) has a diameter of 15% of the body length, and is located at 40%. Its morphology does not differ from that in R. riae sp. n. There are two types of pharyngeal glands: coarse-grained basophilic and coarse-grained eosinophilic ones. In one specimen several diatoms were observe. Proximally, the pharynx opens into the oesophagus ( Fig. 15A : oe).

A pair of testes ( Fig. 15A : t) is located rostrally from the pharynx. In the caudal body fourth, the vasa deferentia are swollen and form the seminal vesicles ( Fig. 15A & 15D : sv), which are lined by longitudinal muscles and fuse with each other just before entering the copulatory bulb. The copulatory bulb ( Fig. 15A & 15C : cb) is 208–245 μm long (x̄ = 228 μm; n = 7). It is lined by a coat of strong circular muscles, which are weakest distally. Proximally, prostate glands ( Fig. 15A : pg) open into the copulatory bulb. The prostate vesicle ( Fig. 15D : pv) contains two types of coarse-grained secretions: a basophilic and an eosinophilic one. Additionally, some fine-grained eosinophilic glands ( Fig. 15D : gl) lie inside the muscular wall of the copulatory bulb. The prostate ducts open into the cirrus. Nuclei of both the basophilic and the eosinophilic glands are extracapsular and could only be observed in live specimens. The cirrus is armed with four rows of spines ( Fig. 15A & 15D : spr). One row ( Fig. 15B–C : spr1) is 88–104 μm long (x̄ = 93 μm; n = 3), the second one ( Fig. 15B–C : spr2) 93–99 μm (x̄ = 96 μm; n = 3), the third one ( Fig. 15C : spr3) 40–42 μm (x̄ = 41 μm; n = 3), and the last one ( Fig. 15C : spr4) 49 μm (n = 3). The triangular spines that make up these rows are 2–4 μm long (x̄ = 3 μm; n = 30). The two largest rows distally end in large, curved, somewhat shark-tooth-shaped spines, increasing in length from the most proximal one (6 μm long) to the most distal one (27 μm long) (x̄ = 16 μm; n = 21). The two distal hooks ( Fig. 15B–D : h) are similar to each other: broad-funnel shaped, 23–26 μm long (x̄ = 24 μm; n = 12) and 13–23 μm wide at their base (x̄ = 18 μm; n = 12), and end bluntly. Depending on the degree of the squeezing and the orientation of the hooks, some specimens reveal that these distal ends bear a small sharp tip directed sideways. The copulatory bulb opens into the male atrium ( Fig. 15D : ma), which itself enters the common genital atrium ( Fig. 15D : ca) through the latter’s rostro-dorsal wall.

The ovaries ( Fig. 15A : ov) are oval-shaped and located rostrally from the copulatory bulb. The vitellaria occur as a large mass throughout almost the complete body of the animal. In some specimens, however, they seemingly extend as one or two rows of large follicles from just caudally of the testes to alongside the copulatory organs ( Fig. 15A : vi). The female duct is bipartite, with the proximal part ( Fig. 15A & 15D : fd1) more or less globular and filled with living sperm, the distal part ( Fig. 15D : fd2) more elongated. In one of the live specimens two separate spermpackages were observed within the proximal part of the female duct. A bundle of glands enters at the transition between the two compartments ( Fig. 15A & 15D : fgl). The female duct is lined by an anucleated epithelium and a layer of strong circular muscles. Distally, the female duct opens into the female atrium ( Fig. 15D : fa). The female atrium is surrounded by an inner weak circular and an outer longitudinal muscle layer. The epithelium of the female atrium could not be observed, probably because it is very low. The female duct enters the common atrium caudodorsally, but the exact point of entry could not be observed in the available material. The exact course of the oviducts could not be determined.

The common genital atrium is lined by a low, anucleated epithelium. The uterus ( Fig. 15D : ut) enters the common atrium caudally. It is lined by a nucleated epithelium and is surrounded by an inner layer of circular and an outer layer of longitudinal muscles. A sphincter separates the proximal third of the uterus from the distal part ( Fig. 15D : sph). Distally from the sphincter, a bundle of fine-grained eosinophilic glands ( Fig. 15D : ueg) enters the uterus. At its distal third, the uterus is surrounded by coarse-grained basophilic glands ( Fig. 15D : ubg). The common gonopore ( Fig. 15A & 15D : cg) is located at 90%. Caudally of the gonopore, a bursa ( Fig15A : b) is present.

Figures

FIGURE 15. Reinhardorhynchus tahitiensis sp. n.. A, general organisation (from a live animal). B–C, sclerotised structures of the copulatory bulb (from the holotype). D, sagittal reconstruction of the genital system from the left hand side. C with proximal end toward top of figure, B with proximal end toward left of figure.