Cheliplana verrucosa, Diez & Reygel & Artois, 2019

Diez, Yander L., Reygel, Patrick & Artois, Tom, 2019, Schizorhynchia (Platyhelminthes, Rhabdocoela) from eastern Cuba, with the description of fifteen new species, Zootaxa 4646 (1), pp. 1-30 : 9-12

Cheliplana verrucosa sp. n.

( Fig. 6 )

http://zoobank.org/ urn:lsid:zoobank.org:act:0F9C72C8-A3D2-4A73-96CC-2085293D1841

Material. Observations on one live animal, whole mounted afterwards, designated holotype ( FMNH https:// id.luomus.fi/KV.612), collected in Bueycabón (type locality) (February 6, 2018), sublittoral, fine-grained sand with organic matter, 0.5 m depth, salinity 33 ‰ .

Etymology. The epithet refers to the fact that the epidermal glands resemble small warts.

Diagnosis. Species of Cheliplana with the epidermis covered by glands that resemble warts, except in the posterior 20% of the body. Proboscis hooks bifurcate at the tip; main hook 15–16 µm long, smallest hook 5–6 µm long, muscular hook supports 16 µm long. Spiny cirrus 28 µm long proximally and 9 µm wide distally, constricted in the middle (4 µm wide); proximal spines 8 µm long, distal ones 4 µm long.

Description. Live animal about 0.7 mm long, pinkish coloured, without eyes. Epidermis covered by warts-like glands ( Fig. 6 A–D: w), except in the caudal 20% of the body. Small rounded rhabdites visible over the entire body surface. Proboscis ( Fig. 6B & 6D : pr, 6E) with hooks bifurcate at the tip, forming a second small hook; main hook 15–16 µm long (n = 2), smallest hook 5–6 µm long (n = 2); muscular supports 15–17 µm long (x = 16 µm; n = 2). Measured on the live animal, pharynx ( Fig. 6A & 6D : ph) 1/8–1/9 of the body length long, connected to the subterminal mouth ( Fig. 6D : m) by a long and spiny prepharyngeal cavity ( Fig. 6 A–B & 6D: pph) that is three times longer than the pharynx.

Testis ( Fig. 6D : t) located ventro-laterally from the pharynx. Testis connected to a single seminal vesicle ( Fig. 6 C–D & 6F–G: sv), opening proximally into the copulatory bulb. Prostate glands ( Fig. 6D & 6 F–G: prg) enter the copulatory bulb about at the entrance of the seminal vesicle. Copulatory bulb inverted-pear shaped, 49 µm long, comprising the prostate vesicle ( Fig. 6 C–D & 6F–G: pv) and the spiny cirrus. Spiny cirrus ( Fig. 6 C–D & 6F–G: ci) 28 µm long, 9 µm wide proximally, narrower at about its midpoint (4 µm), subdistally 12 µm wide, and narrowing to a distal triangular-shaped tip; as a whole the cirrus is arrow-like. Spines largest in the proximal end, 7–9 µm long (x = 8 µm; n = 4) and distally 4–5 µm long (x = 4 µm; n = 5).

Vitellarium ( Fig. 6D : vi) extends behind the pharynx to the beginning of the copulatory bulb. Ovary and globular bursa ( Fig. 6D : b) located caudally from the copulatory bulb. Ovary ( Fig. 6D : ov) kidney shaped, with the oocytes in a row, diminishing in diameter from the most distal to the proximal end of the ovary. Only a connection between the bursa to the common atrium was observed.

Discussion on Cheliplana . All the above-mentioned species show the typical features of the genus (see de Beauchamp 1927; Schilke 1970a): a proboscis consisting of two muscle bulbs (“hook supports”) with simple, curved hooks, and with soft, not-sclerotized sidepieces, a cylindrical (barrel-shaped) pharynx with a long, often spiny prepharyngeal cavity, and only one ovary.

The specimen of C. asica collected in Cuba shows the diagnostic features of the species mentioned in the original description by Marcus (1952). Within the genus, an unarmed cirrus ending in a simple papilla as in C. asica is unique. The ejaculatory duct in the specimen from Cuba (170 µm) is shorter than it is in the specimens from Brazil (280 µm). As no other morphological differences between the specimens of both populations were observed, we consider both populations to belong to the same species. Cheliplana terminalis , primarily described as a subspecies of C. asica by Brunet (1968), can be distinguished from C. asica by the long sclerotized ejaculatory which ends in a sclerotized cap. This is clearly present in the specimens from Cuba. The specimens of C. terminalis from Cuba (0.5–0.9 mm long) are noticeably smaller than the specimens recorded from Marseille (1.6 mm long) ( Brunet 1968), however, they are similar to the specimens from Somalia (about 1 mm long) ( Schockaert 1982). Unfortunately, no measures of the copulatory organ of specimens from Marseilles, Somalia and Kenya are available. However, as there seem to be no morphological differences between the specimens from Cuba and the specimens from the other populations, we prefer to keep them provisionally in the same species.

Cheliplana verrucosa sp. n. is unique within the genus due it has hook supports that are more or less as long as the hooks themselves. In all other species of Cheliplana , the hook supports are much shorter than the hooks. Considering that only one specimen was examined, it is unclear whether the difference in length between the two muscular hook supports of C. verrucosa sp. n. (see Fig. 6E ) is real, or was caused by squeezing. Also the epidermis of the anterior 80% of the body covered with wart-like glands was never recorded from any other species of Cheliplana . The detailed morphology and function of these glands is unknown. Distally bifurcate proboscis hooks as in C. verrucosa sp. n. are only known from C. paradoxa Noldt, 1989 . In C. paradoxa the proboscis hooks are larger (21–25 µm long) than in C. verrucosa sp. n. (17 µm long). Moreover, C. paradoxa has two seminal vesicles ( Noldt 1989), whereas in C. verrucosa sp. n. there is only one. Recently, Armonies (2018) erected a new genus, Dactyloplana Armonies, 2018 , to include C. paradoxa and Dactyloplana tridigitata Armonies, 2018 . The only feature distinguishing species of Dactyloplana from those of Cheliplana is the distally-split hooks in the former ones. However, considering the lack of other morphological differences and of molecular evidence, we decide here to keep both C. paradoxa and C. verrucosa sp. n. within the genus Cheliplana .

Also C. gibarenha sp. n. has only one seminal vesicle, a feature shared with only seven other species of Cheliplana : C. verrucosa sp. n., C. evdonini Karling, 1983 , C. marcusi ( Karling, 1956) Karling, 1983 , C. remanei ( Meixner, 1928) Karling, 1983 , C. sarnensis Gobert, Reygel & Artois, 2017 , C. schilkei Noldt, 1989 , and C. targa ( Marcus, 1952) Karling, 1983 . Cheliplana gibarenha sp. n. is the only one of these species in which the seminal vesicle has a caudal position, and in which the copulatory bulb is oriented forwards, both features unique even within the entire genus. Apart from that it can be distinguished from the other five species with only one seminal vesicle mostly by the detailed structure of the copulatory organ. In C. gibarenha sp. n. the copulatory bulb is very long, with a long cirrus, which only in its most distal, widened part bears small spines. In all other species the cirrus is either short or long, but always completely or for the greater part covered with spines, often showing several species-specific features of its own, such as the presence of an additional stylet in C. targa [for details on the other species: see Karling (1956, 1983); Noldt (1989)]. Of these species, C. marcusi is unique within the genus because its proboscis hooks bear a pair of denticles.

Cheliplana spuriaseminalis sp. n. is the only species of Cheliplana that has one atrophied and one functional seminal vesicle. Indeed, we could not observe any connection between the atrophied seminal vesicle and the testis. In C. uruguayensis Van Steenkiste, Volonterio, Schockaert & Artois, 2008 , there are also two morphologically different seminal vesicles. In this species, however, one show the basic morphology, while the second one is larger and surrounded by a thick muscle coat; both are connected to the single testis ( Van Steenkiste et al. 2008) and are filled with sperm, and hence seem to be functional. Members of the related genus Cheliplanilla Meixner, 1938 also have one seminal vesicle that ends blindly. However, in species of this genus both seminal vesicles contain sperm. More- over, species of Cheliplanilla all have denticles on the proboscis hooks, and have heavily-sclerotized rod-shaped proboscis sidepieces (see Meixner 1938; Brunet 1968; Schilke 1970a; Gobert et al. 2017), features not shared by C. spuriaseminalis sp. n..

Cheliplana spuriaseminalis sp. n. has a rather short unarmed cirrus. Only few other species of Cheliplana lack hard structures in the copulatory organ, and most of them have a very long (> 100 µm) unarmed cirrus ( C. asica , C. terminalis , C. vaginalis Karling, 1983 ). Only in C. rubescens Brunet, 1966 and C. hypergyna Boaden, 1965 , two species up to now known only from the Mediterranean, is the unarmed cirrus comparable in length to that of C. spuriaseminalis sp. n.. Cheliplana hypergyna can easily be distinguished by the highly muscular vagina that is subdivided into several compartments, which is easily seen even in live animals ( Boaden, 1965; own unpublished observations) and by the simple construction of the cirrus, which is no more than a sclerotized tube evenly tapering towards its distal end. According to Boaden, only the most distal part of the cirrus is eversible, and this part “ sometimes displays a number of fine ridges” ( Boaden 1965). Such ridges are recorded to be present over the entire length of the cirrus of C. rubescens but are lacking in C. spuriaseminalis sp. n.. The copulatory bulb of C. rubescens is most comparable to that of C. spuriaseminalis sp. n., apparently also showing the curve at about its midpoint (see Brunet 1966: Fig. 8 ). However, the cirrus of C. spuriaseminalis sp. n. is much less broad, widening abruptly only at the most distal end to a broad space surrounded by longitudinal muscles but without any ridges.

Cheliplana santiaguera sp. n. and C. subproximalis sp. n. have two functional seminal vesicles and a cirrus armed with spines, without stylet or accessory cirrus (or cirri). This is the most common situation in Cheliplana . Among species with such a combination of features, some species show a long, winding cirrus, only the complete distal part of which is provided with spines ( C. hiemalis Brunet, 1968 , C. pacifica Noldt & Hoxhold, 1984 , and C. euxeinos Ax, 1959 ). Other species ( C. setosa Evdonin, 1977 , C. evdonini ) have a short cirrus, typically consisting of three different regions (for details see Evdonin 1977; Karling 1983), which is not the case in Cheliplana santiaguera sp. n., nor in C. subproximalis sp. n. The remaining species can be divided into two groups, one consisting of species with a cirrus that is at most three times as long as broad ( C. gemmifera Noldt, 1989 , C. mamkaevi Evdonin, 1977 , C. microcirrus Noldt, 1989 , C. piriformis Brunet, 1968 , C. pusilla Brunet, 1968 ), the other group consisting of species with a cirrus that is relatively longer.

Cheliplana santiaguera sp. n. belongs to the latter group, with a cirrus that most resembles that of C. barringtonensis Noldt & Hoxhold, 1984 , C. californica Karling, 1989 , C. canariensis Gobert, Reygel & Artois, 2017 , C. elkhornica , and C. orthocirra Ax, 1959 . These species are characterised by a cirrus of moderate length, all between 25 µm ( C. barringtonensis ) and 75 µm ( C. elkhornica ) long. Cheliplana santiaguera sp. n. can be distinguished from most of these species because the spines are of equal length over the entire surface. Only in C. barringtonensis and C. elkhornica are the spines of equal size over the entire length. However, in C. elkhornica the spines of the cirrus are sturdier and longer than in C. santiaguera sp. n. (4–5 µm vs 0.5 µm), and the cirrus itself is also much longer in C. elkhornica than in C. santiaguera sp. n. (75 µm vs 25 µm). C. barringtonensis has a spiny cirrus of comparable length to that of C. santiaguera sp. n. (20 µm), but also in this species the spines are larger (2–3 µm) than in C. santiaguera sp. n.. Moreover, C. barringtonenis shows a typical narrowing of the distal end of the cirrus, which is unarmed and ends in a 12-µm-long cap that protrudes into the atrium (see Noldt & Hoxhold 1984), a feature that is unique within the group of species mentioned.

The copulatory organ of C. subproximalis sp. n. is most similar to that of C. hiemalis , as the ejaculatory duct is relatively long and shows a single curve. Both species, however, can easily be distinguished because the spiny cirrus in C. hiemalis is restricted to the most distal part of the copulatory organ, being only 12 µm long and covered with strong spines (see Brunet 1968). In C. subproximalis sp. n., the cirrus consists of two parts, a long proximal part covered with very fine spines, and a distal part of about 16 µm long, which is widened and covered by larger spines. This distal part lies within a sclerotized cap which is lacking in C. hiemalis . Moreover, in C. hiemalis the seminal duct only turns over ±90°, whereas in C. subproximalis sp. n. it shows a 180° turn, and the seminal vesicle is directed forwards. The subterminal entrance of the seminal duct into the prostate vesicle and the two ducts entering it at the same place are two features not recorded for any other species of Cheliplana in literature.

Figures

FIGURE 6. Cheliplana verrucosa sp. n.. A–B, anterior end of the body. C, copulatory bulb. D, general organisation. E, proboscis. F–G, copulatory bulb. A–D, from the live animal. E–G, from the holotype.

FIGURE 8. Carcharodorhynchus smilodon sp. n.. A, anterior half of the body. B–C, proboscis. D–E, copulatory bulb. F, ovary and cirrus. A, D, from the live animal. B–C, E–F, from the holotype.