Cheliplana pacifica Noldt & Hoxhold 1984
Creators: name: Gobert, Stefan
name: Diez, Yander L.
name: Monnens, Marlies
name: Reygel, Patrick
name: Van Steenkiste, Niels W. L.
name: Leander, Brian S.
name: Artois, Tom
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Rhabditophora
Rhabdocoela
Karkinorhynchidae
Cheliplana
Cheliplana pacifica

description: Cheliplana pacifica Noldt & Hoxhold, 1984
Material examined. Reference material. 10 serially sectioned specimens, including the holotype (P1851– P1860).
Known distribution. Galápagos archipelago, Ecuador (Noldt & Hoxhold 1984).
Remarks. Our observations correspond to those of Noldt & Hoxhold (1984). Specimens are 0.6 to 1.6 mm long. The body is not pigmented. A single, continuous haptic girdle is present near the caudal body end. The overall length of the proboscis is 22–38 μm, with 9–16-µm-long hook supports and slightly curved, 13–22-µm-long sclerotised hooks. Proboscis sidepieces have fine bristles. The oral cavity is lined with a thin, eosinophilic epithelium, partially transformed into sclerotised spines.A single testis is situated ventro-laterally alongside the pharynx. Seminal vesicles are 100–140 μm long and are surrounded by longitudinal muscles. The seminal vesicles and prostatic glands enter the 220–270-µm-long copulatory bulb proximally. The prostatic bulb, situated in the proximal part of the copulatory bulb, contains two distinct types of gland secretion and is surrounded by a separate layer of longitudinal muscles. The ejaculatory duct is partially sclerotised and widens distally to form a cirrus of ~50–60 μm long, provided with fine, 1–2-µm-long spines. Distally, the sclerotised cirrus wall is folded to form a 25–40-µm-long penis papilla. A sphincter is present in front of the insertion of the sclerotised cap. Two clusters of glands surround the common genital atrium: ventrally, around the common genital opening, a cluster of coarse-grained, basophilic glands, and more proximally, a cluster of fine-grained, eosinophilic glands. The female genital canal is short and connects the single ovary to the common genital atrium. The opening to the vagina externa is situated terminally. The distalmost part of the vagina forms a small bulbous region, which was not mentioned by Noldt & Hoxhold (1984), but was easily distinguished in the holotype. The vaginal pore is provided with a strong sphincter. The vagina externa leads into a long, sinuous bursa, which is made up of a mass of syncytial, parenchymatic tissue. A short, sclerotised spermatic duct is present between the bursa and ovary.
Noldt & Hoxhold (1984) mention a distinct difference in size, related to the locality where the specimens were found. The specimens from the type locality (Bahía Darwin) were consistently larger than the specimens from the Santa Cruz locality (total body length: 1.3–1.6 μm vs 0.6–0.9 μm respectively). The proboscis and copulatory organ show a similar variation in size.
description: Published as part of Gobert, Stefan, Diez, Yander L., Monnens, Marlies, Reygel, Patrick, Van Steenkiste, Niels W. L., Leander, Brian S. & Artois, Tom, 2021, A revision of the genus Cheliplana de Beauchamp, 1927 (Rhabdocoela: Schizorhynchia), with the description of six new species, pp. 453-494 in Zootaxa 4970 (3) on page 476, DOI: 10.11646/zootaxa.4970.3.2, http://zenodo.org/record/4766692