Kymocarens morrisi, Diez & Monnens & Wuyts & Brendonck & Reygel & Schmidt-Rhaesa & Artois, 2023

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 : 672-673

Kymocarens

Representatives of Kymocarens are characterised by large and conspicuous anterior rhabdite tracts, a caudal adhesive tail plate, paired testes situated anterior to the pharynx, paired seminal vesicles, a tubular stylet, paired ovovitellaria with the ovaries most caudally, an atrial bursa connected to the common genital atrium, and each oviduct with a seminal receptacle ( Ehlers & Ehlers, 1981). All these features are present in the specimens from Cuba, justifying inclusion in the genus Kymocarens . However, in K. morrisi sp. n., the position of the ovaries is not completely clear. The ovaries seem to be located just caudal to the male copulatory organ ( Fig. 11a : ov).

The only molecular data available for Kymocarens is the sequence of the 18S rDNA gene of Kymocarens sp. ( Van Steenkiste et al., 2013). Unfortunately, we failed to amplify the 18S gene for K. morrisi and only the amplification of the 28S gene was succesful. Therefore, we did not include K. morrisi in the phylogenetic analyses. Consequently, we cannot address the monophyly of Kymocarens and the discussion of the new species is based on comparative morphology.

Three species of Kymocarens have previously been described, and K. morrisi sp. n. can be distinguished from these by the morphology of the stylet. In K. proxenetoides Ehlers & Ehlers, 1981 , the elongated and funnel-shaped stylet is 49–50 μm long, whereas in K. tibialis Ehlers & Ehlers, 1981 , it is 30 μm long with a complex distal end (see Ehlers & Ehlers, 1981; Willems et al., 2005a). In K. kanakorum Willems et al., 2005a , the stylet is 56 μm long and shows a typical transverse ridge distally ( Willems et al., 2005a). Kymocarens morrisi sp. n. displays a longitudinal slit in the proximal end of the stylet. This feature combined with the fact that the stylet bends over 90° at its midpoint are diagnostic for the new species. Furthermore, measuring 66–89 µm long, the new species possesses the longest stylet ever reported for a species of Kymocarens .

The general morphology of the atrial organs of K. morrisi sp. n. does not differ from that in K. proxenetoides and K. tibialis . However, the parenchymal sheath surrounding the bursa is unique for K. morrisi sp. n. Also, the sphincter on the distal aperture of the pharynx has never been reported in any other representative (but note that both features are unknown for K. kanakorum , as no sectioned material of this species exists).

Figures

Fig.11 Kymocarens morrisi sp. n. a Body organisation (live animal). b Schematic recon- struction from sagittal sections of the pharynx from the right side. c Schematic reconstruc- tion from sagittal sections of the genital system from the left side; the right oviduct, ovary, and vitellarium are not drawn. d, e Stylet. d From the holotype. a, d–e Structures oriented with the anterior end toward the top of the plate. b Structures oriented with the anterior end toward the right side of the plate. c Structures oriented with the anterior end toward the left side of the plate