Schizochilus favus, 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 : 23-26

Schizochilus favus sp. n.

( Fig. 13 , 14 A–B)

http://zoobank.org/ urn:lsid:zoobank.org:act:23613044-29FD-45CF-A694-B984B0164D12

Material. Observations on live animals, whole mounted afterwards. Six whole mounts from Siboney (type locality) (February 7, 2016), one of which is designated holotype ( FMNH https://id.luomus.fi/KV.621), the others in HU (X.1.27– X.1.31), intertidal, upper 20 cm of the fine-grained sand, salinity 35 ‰.

Etymology. The epithet reflects the fact that the bases of the cirrus spines together have the appearance of a honeycomb. Lat. favus : honeycomb.

Diagnosis. Species of Schizochilus with a single large testis rostrally from the pharynx. Spiny cirrus 37 μm long; spines about 2 μm long in the proximal half of the cirrus and 7 μm long in the distal half. The bases of the spines are arranged in such a way that in the live animal they have the appearance of a honeycomb. Inside the cirrus a ±36-μm-long stylet is present. Copulatory organ without a distal cap.

Description. Live animals about 1–1.5 mm long, 0.6–1.4 mm long in the whole mounts (x = 1 mm; n = 5), translucent, without eyes. Habitus and internal organisation as in S. espinosai sp. n.. Proboscis ( Fig. 13A : pr) 84– 88 μm long (x = 86 μm; n = 6), with a pair of gland sacs ( Fig. 13A : pg) that enter the proboscis at its proximal end. Rostrally from the proboscis, in the proximal tip of the body, a pair of brownish-pink glands ( Fig. 13A : gl) can be found, one on each body side. The brain ( Fig. 13A : br) is located caudally from the proboscis. Pharynx ( Fig. 13 A–B: ph) has a diameter of 93–98 μm (x = 96 μm; n = 4), and is located at 70%.

A large testis, up to 272 μm long in one whole mount ( Fig. 13 A–B: t), is located rostrally from the pharynx. Two vitellaria ( Fig. 13 A–B: vi) extend between the brain and the copulatory bulb, one at each side of the body. The rest of the genital organs are situated in the caudal fourth of the body, with the ovary and the bursa near to the caudal body end. Copulatory bulb ( Fig. 13A : cb, 14A–B) comprising the prostate vesicle and a spiny cirrus. Spiny cirrus ( Fig. 13B : ci, 13C–F, 14A–B) 34–38 μm long (x = 37 μm; n = 5) and 9–11 μm wide (x = 10 μm; n = 5). In the proximal half of the cirrus, the spines are about 2 μm long (n = 18); in the distal half they are 5–12 μm long (x = 7 μm; n = 12). The spines are arranged in such a way, that their bases together form a honeycomb-like struc- ture (see Fig. 13C ), mainly in the distal half of the cirrus. Inside the cirrus lies a tubular stylet, 35–37 μm long (x = 36 μm; n = 2) and 8–12 μm wide proximally (x = 10 μm; n = 4). This stylet bears longitudinal ridges (see Fig. 13D , 14A ). In general the stylet is not well visible because the spines hamper observation. Often only the proximal part is visible, as shown in Fig. 14A . The copulatory bulb does not form a sclerotized cap surrounding its distal tip. The common gonopore opens at 90%.

Figures

FIGURE 13. Schizochilus favus sp. n.. A, body. B, distal end of the body. C–F, different views of the cirrus and the stylet.A–B, from a live animal. C–F, from whole mounts.

FIGURE 14. Copulatory bulb of the species of Schizochilus without distal sclerotized cap in the cirrus. A–B, Schizochilus favus sp. n.. C, Schizochilus bueycabonensis sp. n.. D, Schizochilus lanzarotensis (from the holotype: SMNH Type-8911). A–D, from whole mounts. A, from a reference specimen (HU X.1.27). B–C, from the holotype.