Pseudoceros bifascia Dixit & Sreeraj 2024, sp. nov.
Creators: name: Dixit, Sudhanshu
name: Sreeraj, Chemmencheri Ramakrishnan
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Polycladida
Pseudocerotidae
Pseudoceros
Pseudoceros bifascia

description: Pseudoceros bifascia sp. nov.
(Figures 5−7)
Type material
Holotype (10 x 6 mm): as sagittal sections; Regn. No. ZSI/WGRC/I.R.-Inv.22072; reproductive structures in seven slides; Agatti Island (10°52’5.79”N, 72°12’12.64”E; Lakshadweep, India; Near Eastern Jetty, Oct 27, 2019, Coll. Sreeraj C.R.)
Other material: One specimen, damaged during the course of tissue collection for DNA studies (specimen became very soft after coming in contact with ice and was damaged beyond recognition). 10 mm approx., used for DNA studies (no result), photographs used for colour determination.
Etymology
The specific name refers to the presence of two-coloured bands (black and orange) on pseudotentacles (Fig. 2B, E) i.e., two (bi in Latin) and band (fascia in Latin).
Type Locality
Agatti Island (10°52’5.79”N, 72°12’12.64”E), Lakshadweep, India.
Description
Live: Body small (15mm x 8 mm) and oval with smooth margin. White background colour with black pattern on the dorsum; thin interrupted orange marginal band followed by a wide white rim (Fig. 5A, B). A thin longitudinal stripe line runs from cerebral eyespot cluster to the posterior end without touching the orange marginal band (Fig. 5A, B). Pseudotentacles black-tipped, followed by an orange band and are simple folding of the anterior margin. Cerebral eye cluster horseshoe-shaped. Ventral surface cream in colour.
Preserved: Specimen yellowish after fixation (Fig. 5C). Male and female gonopores 0.7 mm apart; female gonopore and sucker 0.9 mm apart (Fig. 5D). Pharynx 2.2 mm long, ruffled with six to seven folds. Male gonopore situated very close to last pair of pharyngeal folds (Fig. 5D), and 4.4 mm from anterior margin. Cerebral eye cluster with ~45–50 eyes (Fig. 5E). Ventral tentaclular eyes distributed in limited area (Fig. 5F). Dorsal epidermis thick in comparison to ventral epidermis; dorsal epidermis thickness 47 to 51 µm; ventral epidermis 5 to 8 µm thick.
Male reproductive system single, consists of ventrally scattered testes (Fig. 6C), seminal vesicle, free prostatic vesicle, penis papilla in thick penis sheath housed in male atrium, which opens to the outside via male gonopore (Fig. 6A). An elongated slender-shaped, thick-walled seminal vesicle present, 470 µm long and 210 µm wide at widest point (Fig. 6A, B). Oval, thin-walled prostatic vesicle, 183µm long and 85 µm wide, present anterior to the seminal vesicle (Fig. 6B). Prostatic vesicle with smooth granular epithelial lining, ~3 to 5 µm thick. Male atrium simple without folds (Fig. 6B) housing unarmed conical penis papilla surrounded by thick penis sheath (Fig. 6B).
Female reproductive system consists of dorsally scattered ovaries (Fig. 6C), oviducts, vagina, cement pouch surrounded by numerous cement glands and female atrium (Fig. 6B). Vagina oriented towards the posterior body region, connecting to the oviducts (Fig. 6B). Vagina opens to short female atrium via cement pouch, which receives the secretion from cement glands. Female atrium opens to the exterior via female gonopore (Fig. 6B).
Taxonomic remarks
The colour pattern of Pseudoceros bifascia sp. nov. is distinct (white background with irregular black pattern; fluorescent longitudinal stripe and margins made up of interrupted orange band and white rim) thus, differentiating it from other congeners. However, three species, viz. Ps. scintillatus Newman & Cannon, 1994, Ps. scriptus Newman & Cannon, 1998 and Ps. zebra (Leuckart, 1828) possess colours of orange/yellow, black and white but are different in arrangement and patterns.
Pseudoceros scintillatus has a velvety black background with irregularly sized yellow-green maculae encircled with white and has an orange marginal band while Ps. bifascia sp. nov. has white background with an interrupted orange marginal band followed by wide white rim.
Pseudoceros scriptus has a cream-yellow background with black irregular maculae on the dorsum; white near the margin followed by an orange rim, but Ps. bifascia sp. nov. has an interrupted orange marginal band followed by wide white rim.
Pseudoceros zebra has a white background with irregular black bands or patches; wide yellow marginal band interrupted by white markings while Ps. bifascia sp. nov. though have white background and black patches, its marginal band is orange followed by a wide white rim.
In addition, the newly described species features a simple male atrium as opposed to the folded male atrium of Ps. scintillatus and Ps. scriptus. A specimen comparable to Ps. bifascia sp. nov. was photographed in the Red Sea (Pseudoceros sp. 19, Newman & Cannon 2003, Pg. 80 & 2005) and there has been no record of any similar specimen in literature or in any websites after then. This species was considered rare by Newman & Cannon (2003, pg. 80 & 2005). Thus, in light of the above-mentioned characters and comparisons, we describe Pseudoceros bifascia as new species to science.
description: Published as part of Dixit, Sudhanshu & Sreeraj, Chemmencheri Ramakrishnan, 2024, Two new polyclad (Platyhelminthes: Polycladida) flatworm species from the Lakshadweep Islands, India, pp. 405-419 in Zootaxa 5446 (3) on pages 413-416, DOI: 10.11646/zootaxa.5446.3.5, http://zenodo.org/record/11101945