Reinhardorhynchus ryukyuensis Van Steenkiste, Wakeman, & Leander 2024, sp. nov.
Creators: name: Tsuyuki, Aoi
name: Reyes, Jhoe
name: Oya, Yuki
name: Wakeman, Kevin C.
name: Leander, Brian S.
name: Van Steenkiste, Niels W. L.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Rhabdocoela
Koinocystididae
Reinhardorhynchus
Reinhardorhynchus ryukyuensis

description: Reinhardorhynchus ryukyuensis Van Steenkiste, Wakeman, & Leander sp. nov.
Fig. 2
Material examined.
Holotype: Japan • 1; Okinawa Prefecture, Onna; 26 ° 28 ' 52.7 " N, 127 ° 50 ' 18.8 " E; Feb. 2019; coarse mixture of sand, coral fragments, and shell hash from an intertidal seagrass bed; Niels Van Steenkiste and Kevin Wakeman leg.; one individual worm in a single slide [Holotype: NSMT - Pl 6458];
Paratype: Japan • 1; locality same as for holotype; Feb. 2019; Niels Van Steenkiste and Kevin Wakeman leg.; one individual worm in a single slide; [Paratype: NSMT - Pl 6459].
Other material.
Japan • 1; locality same as for holotype; Feb. 2019; Niels Van Steenkiste and Kevin Wakeman leg.; two genomic DNA extracts from two individuals stored at - 20 ° C; GenBank: LC 807766 (18 S rDNA; 1,760 bp), LC 807768, LC 807769 (28 S rDNA; 1,675 bp).
Type locality.
Japan, Okinawa Prefecture, Onna (26 ° 28 ' 52.7 " N, 127 ° 50 ' 18.8 " E).
Diagnosis.
Species of Reinhardorhynchus with conjuncta-duplex type male copulatory organ composed of a proximal globular part, a weakly sclerotized cylindrical middle part, and a distal penis papilla. Sclerotized structures of the copulatory organ consist of two large, separate hooks at the transition between the middle part and penis papilla and a distal girdle of two semi-elliptical plates bearing five smaller hooks. One larger hook with collared striated base, 29–31 μm long, pointing proximally; the other larger hook straight, with striated base, 29–34 μm long, pointing distally. The smaller distal hooks are 9–17 μm long. Female system with bipartite female duct, muscular bursal stalk, large bursa, and pouch of female glands.
Description.
General morphology. Animals are 840–1060 μm long (x ̄ = 935 μm; n = 4), transparent, and have two eyes (Fig. 2 A, B). General organization and internal morphology are consistent with other species of Reinhardorhynchus, as described by Diez et al. (2021). The large, typical koinocystidid proboscis (pr, Fig. 2 A, B) is about 1 / 4 of the body length (215–233 μm; x ̄ = 224 μm; n = 3), with a well-developed juncture sphincter. Ciliated cellular epidermis with needle-like rhabdites is present all over the body.
The globular pharynx (ph, Fig. 2 A, B) is at about 50 % of the body length, followed by an intestine (i, Fig. 2 A, B) that runs all the way to the posterior end. The oesophagus (oe, Fig. 2 A, B) is visible as a clear, transparent zone bordered by oesophageal glands right behind the pharynx.
Male reproductive system. Paired testes are located in front of the pharynx (t, Fig. 2 A, B). The conjuncta-duplex type male copulatory organ (165–195 μm; x ̄ = 180 μm; n = 4) is inverted-pear shaped and encompasses the prostate vesicle (pg, Fig. 2 A – C). This prostate vesicle is composed of gland necks of prostate glands originating extracapsularly, extending into the middle part of the copulatory organ, and opening distally into the ejaculatory duct. The bulbous proximal part of the prostate vesicle is surrounded by circular muscles (cm, Fig. 2 D), while the cylindrical middle part is surrounded by two layers of oblique muscles (om, Fig. 2 D) and an inner layer of longitudinal muscles (ilm, Fig. 2 D). The walls of the middle and distal parts of the copulatory organ are weakly sclerotized (scl, Fig. 2 C, D) and distally form a penis papilla (pp, Fig. 2 C, D), which enters into the male genital atrium (ma, Fig. 2 C, D). The entire copulatory organ is encased in an outer layer of longitudinal muscles (olm, Fig. 2 C, D). Paired seminal vesicles (sv, Fig. 2 A – C) merge right before entering the copulatory organ proximally and form the ejaculatory duct (ed, Fig. 2 D). The necks of the prostate glands and the ejaculatory duct run throughout the entire length of the copulatory organ and into the penis papilla.
The male copulatory organ is provided with sclerotized structures consisting of two larger separate hooks and a girdle of five smaller interconnected hooks (lh 1 – lh 2, sh 1 – sh 5, Fig. 2 E – H). The two larger hooks are positioned at the transition of the cylindrical middle part to the penis papilla and point in opposite directions. The proximally pointing larger hook (lh 1, Fig. 2 E – H) measures 29–31 μm (n = 2) and is provided with a collared striated base. The distally pointing larger hook (lh 2, Fig. 2 E – H) is straight, measures 29–34 μm (n = 2), and has a striated base that seems to be continuous with the weakly sclerotized layer. The five distal, smaller hooks are connected by a complex sclerotized girdle surrounding the distal tip of the penis papilla. The smaller hooks sh 1 (15–17 μm; n = 2) and sh 2 (10–13 μm; n = 2), and sh 3 (10–13 μm; n = 2) and sh 4 (9–12 μm; n = 2) are each connected through a semi-elliptical base, respectively. The base of the smaller hook sh 5 (10–12 μm; n = 2) seems to connect both semi-elliptical bases into an open girdle.
Female reproductive system. The female structures are located caudal to the pharynx and include paired ovaries (ov, Fig. 2 B, C), a female duct (fd, Fig. 2 B) consisting of two parts (fd 1 and fd 2, Fig. 2 C), and a very muscular bursal stalk (bs, Fig. 2 B – D) guarding the entrance to a large bursa (bu, Fig. 2 B, C). At its proximal end, the female atrium (fa, Fig. 2 B, C) receives the female duct, the bursal stalk, and a pouch of female glands (fg, Fig. 2 B, C). The female duct is separated from the female atrium by a small sphincter. A uterus (u, Fig. 2 B) is present between the male and female atria. Vitellaria and the common gonopore could not be observed in the live animals.
Etymology.
Species epithet based on its occurrence on the Ryukyu Islands.
Distribution.
Okinawa Islands, Japan.
description: Published as part of Tsuyuki, Aoi, Reyes, Jhoe, Oya, Yuki, Wakeman, Kevin C., Leander, Brian S. & Van Steenkiste, Niels W. L., 2024, Marine microturbellarians from Japan, with descriptions of two new species of Reinhardorhynchus (Platyhelminthes, Rhabdocoela, Koinocystididae), pp. 877-895 in Zoosystematics and Evolution 100 (3) on pages 877-895, DOI: 10.3897/zse.100.120244