Carcharodorhynchus nativus, 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 : 18-20

Carcharodorhynchus nativus sp. n.

( Fig. 11 )

http://zoobank.org/ urn:lsid:zoobank.org:act:D3B6D290-80A3-44F8-99CA-F7CC6CC66BF8

Material. Observations on live animals, whole mounted afterwards. One whole mount from Bueycabón (type locality) (November 18, 2018), designated holotype ( FMNH https://id.luomus.fi/KV.616), intertidal, upper 10 cm of fine-grained sand, salinity 31 ‰. Five whole mounts from El Masío (June 30, 2016) (HU X.1.14– X.1.18), intertidal, upper 10 cm of medium-grained sand, salinity 33 ‰.

Etymology. Species named in tribute to the autochthonous populations (named “nativos” in Spanish) who dwelled around the distribution area of the new species before, and few years after the discovery of Cuba by Christopher Columbus.

Diagnosis. Species of Carcharodorhynchus with asymmetric proboscis; largest lip 119 µm long and smallest 95 µm long. In the smallest lip, the denticles are 1–2 µm long, ordered in four rows. In the largest lip, the denticles are 0.3–0.5 µm long in the basal half, ordered in six to seven rows, and 1–2 µm long in the distal half, ordered in four to six rows. Spiny cirrus 45 μm long; densely covered with small spines, which are 3 µm long proximally, 6 µm in the midpart, and 9 µm distally.

Description. Live animals slender, 1–1.5 mm long, light-brown to orange-brown, without eyes. There is a pale belt near the posterior body end, corresponding to the single adhesive girdle. Epidermis opaque, thick, hampering the study of the internal morphology on live animals. Proboscis ( Fig. 11A : pr, 11B–C) asymmetric: largest lip 105–146 µm long (x = 119 µm; n = 3), smallest 85–112 µm long (x = 95 µm; n = 3). In the smallest lip, denticles are 1–2 µm long, ordered in four rows. In the largest lip, denticles are 0.3–0.5 µm long in the basal half, ordered in six to seven rows, and 1–2 µm long in the distal half, ordered in four to six rows. The toothed belts are continuous between both lips. In live animals, spherical to oval-shaped glands ( Fig. 11B : prg) were observed along the internal surface of the lips. Pharynx ( Fig. 11A : ph) 64–142 µm in diameter (x = 100 µm; n = 3), located at 60%. Several diatoms were observed in the gut.

Testes were observed only in one specimen (Bueycabón). There is one pair, which is located rostrally from the pharynx. Copulatory bulb ( Fig. 11A : cb, 11D–E) located caudally from the pharynx. Two elongated seminal vesicles ( Fig. 11 D–E: sv) narrow towards the copulatory bulb, which they enter separately. Elongated copulatory bulb 86–101 μm long (x = 92 µm; n = 3), comprising the prostate vesicle and the spiny cirrus. Prostate vesicle ( Fig. 11 D–E: pv) spherical, 31–37 μm long (x = 35 µm; n = 3). At the place where the seminal vesicles enter the prostate vesicle, two small vesicles ( Fig. 11E : ev) can be observed, which are the necks of prostate glands. Spiny cirrus ( Fig. 11 D–E: ci) 46–48 μm long (x = 45 µm; n = 3) and 9–10 μm wide proximally (n = 2). Spines densely packed together. Proximally the spines are 2–3 µm long (x = 3 µm; n = 10), in the middle part 5–7 µm (x = 6 µm; n = 10), and distally 8–10 µm (x = 9 µm; n = 10). Distally from the cirrus, the copulatory bulb continues as a long and nar- row male atrium ( Fig. 11E : ma) towards the common genital atrium.

Paired vitellaria lie at both body sides, between the brain and the copulatory bulb. Globular bursa located caudally from the copulatory bulb. Globular ovaries located caudally from the bursa.

Discussion on Carcharodorhynchus . The new species from Cuba can easily be attributed to Carcharodorhynchus as they show all diagnostic features of the genus. Species of that genus all have a proboscis consisting of two sturdy lips that bear belts of small teeth (= denticles) at their inner surface, and have two ovaries, whereas most other schizorhynchs only have one ( Meixner 1938; Ax 1951; Schilke 1970a; Reygel et al. 2014). All species have a very similar habitus and internal organisation, and can mainly be distinguished from each other based on details in the structure of the proboscis (symmetric or asymmetric), the shape and organisation of the proboscis denticles, and the morphology of the copulatory organ proper.

Seventeen species of Carcharodorhynchus have been described, only one of which ( C. flavidus ) was described with a proboscis with separated belts of teeth; i.e. the rows of teeth of the ventral and dorsal lip are separated from each other by an area lacking teeth at the place where the two lips join each other (see Brunet, 1967). This characteristic “basal gap” is also seen in two of the new species: C. smilodon sp. n. and C. papillaris sp. n.. Our examination of the specimen of C. polyorchis L’Hardy, 1963 deposited in the SMNH (Nr. 54059) clearly shows that also in this species this ‘basal gap’ is present, a fact never mentioned in literature. As such, the four species mentioned are clearly different from all other species of Carcharodorhynchus . The subtle differences distinguishing C. polyorchis and C. flavidus pertain to the presence/absence of an adhesive belt, the presence/absence of pigment grains in the epidermis and details in the male genital system, and are discussed by Brunet (1967). The length of the cirrus in the specimens of C. flavidus collected in Cuba (26–35 µm) clearly fits the range provided by Brunet (1967) (15–39 µm), as did that of the populations recorded from North Carolina (19–22 μm; Whitson et al. 2011), Lanzarote (26–67 μm; Gobert et al. 2017) and from Sardinia (30–34 μm; Gobert et al. 2017). Whether the different populations represent a complex of ‘cryptic’ species or whether C. flavidus is a very wide-spread species remains enigmatic.

Carcharodorhynchus smilodon sp. n. and C. papillaris sp. n. resemble C. flavidus most as they both lack pigment granules, possess an adhesive belt near the caudal end, and have long-drawn seminal vesicles (in C. smilodon sp. n.). Carcharodorhynchus smilodon sp. n. is extremely similar to C. flavidus , and can mainly be distinguished from that species by the dimensions of the denticles on the proboscis belts. Carcharodorhynchus smilodon sp. n. has denticles of 2 µm long at the base of the lips, whereas the most distal ones are ± 5 µm long (up to 6 µm long for the largest ones). In C. flavidus , denticles are at most 3 µm long, and are more or less of the same length over the entire length of the proboscis lips, without large size differences.

Carcharodorhynchus papillaris sp. n. can easily be distinguished from C. flavidus , as well as from all other species of Carcharodorhynchus as it is the only representative of Carcharodorhynchus with a single seminal vesicle and a copulatory bulb without any hard structures. All other species show a stylet, a spiny cirrus, or a combination of both. Carcharodorhynchus spiniferus sp. n. and C. nativus sp. n. both have a cirrus only. Carcharodorhynchus spiniferus sp. n. differs from all the other species in that the cirrus is armed with large, up to 23-µm-long spines proximally, and much shorter spines distally. In all other species with an armed cirrus the spines are more or less equally long over the entire length of the cirrus (except for C. nativus sp. n.; see further), and never as long as 25 µm. Moreover, the tooth that each of the larger spines in the cirrus of C. spiniferus sp. n. shows is a unique feature within the genus.

Carcharodorhynchus nativus sp. n. is characterized by the cirrus spines very densely packed together: proximally 2–3 µm long, 5–7 µm long in the middle part, and 8–10 µm long distally. Such an arrangement is unique within the genus. As to proboscis dentition, the distribution pattern as seen in C. nativus sp. n. is similar to that in C. spiniferus sp. n., with two regions of denticles of different lengths, which is a quite an uncommon feature within Carcharodorhynchus . In C. worsaae Reygel, Janssens & Artois, 2014 , the denticles also show differences in length and morphology. On the longer proboscis lip of this species, each field is proximally armed with denticles ±1 μm wide and more distally denticles of ±2.5 μm wide. The most distal part shows denticles up to 6.5 μm wide and 2.5 μm high with a pointed end bending towards the base of the proboscis. The smaller proboscis lip bears denticles of the same size and with the same arrangement as the distal zone of the larger lip (see Reygel et al. 2014). However, this situation differs from that in the two species from Cuba. In C. spiniferus sp. n. the largest lip bears triangular denticles ± 0.3 µm long in the proximal third, and ± 0.6 µm in the middle and distal thirds; in the smallest lip the denticles are equal in size; ±0.6-µm-long. In C. nativus sp. n. the largest lip bears denticles 0.3–0.5 µm long in the basal half and 1–2 µm long in the distal half; in the smallest lip the triangular denticles are 1–2 µm. The proboscis of C. isolatus Schilke, 1970 also bears two kind of teeth: proximally in the largest lip the denticles are triangular and 2.4 µm long, and distally there are shark-teeth shaped and 4.8 µm long. In the smallest lip the teeth are similar to those in the distal part of the largest lip. Also C. longicirrus Noldt & Hoxhold, 1984 and C. tabulaeferus Noldt & Hoxhold, 1984 bear denticles of two different sizes on the proboscis: the smallest lip and the proximal part of the largest lip bears 0.5-µm-long teeth, and in the largest one there are 1.2 µm long ( C. tabulaeferus ) or 0.9–1.2 µm long ( C. longicirrus ). Furthermore, the cirrus of C. nativus sp. n. (45 µm long) and C. spiniferus sp. n. (50 µm long) greatly differs from that of C. isolatus (14 µm long and armed with small spines), C. tabulaeferus (25 µm long and armed with 9-µm-long spines), and C. longicirrus (90 µm long and bears three cuticular strips and 10-µm-long spines) (see Schilke 1970a; Noldt & Hoxhold 1984).

Figures

FIGURE 11. Carcharodorhynchus nativus sp. n.. A, body. B–C, proboscis. D–E, copulatory bulb. A–B, from a live animal. C–E, from whole mounts. C–D, from the holotype. E, from a reference specimen (HU X.1.14).