Neokytorhynchus Ehlers & Ehlers, 1981

Diez, Yander L., Monnens, Marlies, Wuyts, Arlien, Brendonck, Luc, Reygel, Patrick, Schmidt-Rhaesa, Andreas & Artois, Tom, 2023, Taxonomy and phylogeny of Dalytyphloplanida Willems et al., 2006 (Platyhelminthes: Rhabdocoela), with the description of a new family, a new genus, and sixteen new species from Cuba and Panama, Organisms Diversity & Evolution (New York, N. Y.) 23 (4), pp. 631-681 : 645-646

Neokytorhynchus Ehlers & Ehlers, 1981 Neokytorhynchus pacificus Ehlers & Ehlers, 1981

( Figs. 4 and 5 )

Known distribution. Bahía Academy, Santa Cruz, Galapagos Islands ( Ehlers & Ehlers, 1981) .

Material and distribution. Canary Islands: Observations on live animals. Three whole mounts; ten sagittally; five horizontally; and six transversally oriented serial sections (HU XIX.2.40– XIX.2.50, XIX.3.01– XIX.3.13); and one specimen used for molecular analyses, collected in Lanzarote. Small bay just south of Orzola (7 October 2011), sheltered pool with a direct connection to the ocean; coarse sand with large pieces of lava rocks, 50–60 cm under water. Mala (October 13, 2011); intertidal, coarse, mixed, calcareous, volcanic sediment, upper 4–6 cm of sand, taken between rocks .

Remarks. The sectioned specimens are approximately 0.4 mm long, and 0.2 mm in width, smaller than that ones from The Galapagos (0.7 mm long; Ehlers & Ehlers, 1981). The structure of the epidermis, basal membrane, and subepidermal muscle layer is similar to what is described for other kytorhynchids (see Rieger, 1974). The anterior body invagination ( Figs. 4a–c and 5a, b : in) and the pharynx ( Figs. 4a, b, d and 5a, c : ph) are as that described for the specimens from The Galapagos.

The gonopore ( Fig. 4d : cg) is located ventrally and subcaudally and opens into the common genital atrium ( Figs. 4d and 5c : ca). No epithelial nuclei occur in this area. The epithelium is ruffled here, giving the appearance of cilia (pseudociliation). The round copulatory bulb ( Figs. 4b and 5a, c : cb) is lined with a nucleated epithelium ( Fig. 4d : ep1) and surrounded by a thin, longitudinal muscle layer ( Fig. 4d : lm). The bulb contains the single seminal vesicle ( Figs. 4a, d and 5a : sv) and a large prostate vesicle ( Figs. 4a, d and 5a, c : pv), which empty into a broad, bowl-shaped penis papilla ( Fig. 4a, d : pp). The penis papilla measures 25–34 µm in length and 33–44 µm in width (n = 2), at its broadest point, and empties in a relatively large male atrium. According to Ehlers and Ehlers (1981), the length of the whole copulatory bulb of N. pacificus is 50 µm. The quality of the holotype of N. pacificus did not allow us to measure the penis papilla. Notwithstanding, this structure in the original drawing of Ehlers and Ehlers (1981: Fig. 15 ) is approximately 33 µm long, consonant with the measured range of the specimens from Lanzarote.

The paired ovaries ( Fig. 4a, d : ov) are located at the caudal body end. The female duct ( Figs. 4d and 5a, c : fd) is lined with a high, nucleated epithelium ( Fig. 4d : ep2) and forms two seminal receptacles ( Fig. 4d : sr), separated by a constriction. However, the bundles of glands entering the female duct and described from the specimens from The Galapagos were not observed in the specimens from Lanzarote.

Figures

Fig.4 Neokytorhynchus pacifi- cus Ehlers & Ehlers, 1981. a, b Body organisation (live animals). c Schematic reconstruction from sagittal sections of the anterior invagination.d Schematic recon- struction from sagittal sections of pharynx and the genital sys- tems from the right side; the left ovary and the vitellaria are not drawn. a, b Structures oriented with the anterior end toward the top of the plate. c Structures oriented with the anterior end toward the left side of the plate. e Structures oriented with the anterior end toward the right side of the plate

Fig. 5 Neokytorhynchus pacificus Ehlers & Ehlers, 1981. Micrograph of the sections. Structures oriented with the anterior end toward the right side of the plate

Fig. 15 Male genital structures in the new species of Promesos- toma (from the holotype). a Promesostoma baculum sp. n. b Promesostoma cubanum sp. n. c Promesostoma cubitum sp. n. d Promesostoma panamaense sp. n. e Promesostoma roseaphar- ynx sp. n. f Promesostoma toryne sp. n. a, d–e Structures oriented with the anterior end toward the left side of the plate. b, c, f Structures oriented with the anterior end toward the top of the plate