Paraplanocera kalpeniensis Dixit & Sreeraj 2024, sp. nov.
Creators: name: Dixit, Sudhanshu
name: Sreeraj, Chemmencheri Ramakrishnan
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Polycladida
Planoceridae
Paraplanocera
Paraplanocera kalpeniensis

description: Paraplanocera kalpeniensis sp. nov.
(Figures 2−4)
Type Material
Holotype (16 x 12 mm): as sagittal sections: Regn. No. ZSI/WGRC/I.R.-Inv.22070; reproductive structures in seven slides; Kalpeni Island (10° 6’13.16”N, 73°39’5.44”E; Lakshadweep, India; tidal pools near northern tip, Oct 30,2019, Coll. Sreeraj C.R.)
Paratype (13 x 9 mm): intact; Regn. No. ZSI/WGRC/I.R.-Inv.22071; Kalpeni Island (10° 3’37.05”N, 73°38’19.78”E, Lakshadweep, India; near southern tip, November 02, 2019, Coll. Sreeraj C.R.).
Etymology
The specific name refers to the type locality, Kalpeni Island in Lakshadweep archipelago, where the type specimens were collected.
Type Locality
Kalpeni Island (10° 6’13.16”N, 73°39’5.44”E), Lakshadweep, India.
Description
[Based on holotype] External: Live- Body translucent and elongated oval; pinkish to orange coloured; yellowish tint towards margin; studded with numerous white irregular blotches on mid dorsal region (Fig. 2A). Marginal bands consist of three coloured bands; outer white rim followed by broken violet and purple band. Inner violet and purple bands interrupted with a white rim at numerous points. Nuchal tentacles slender with purple tips (Fig. 2A). Numerous tentacular eyes at the base of tentacles; cerebral or marginal eyes not observed. Pharynx ruffled; male and female gonopore separate.
Preserved: Specimen slightly curled with faded colours (Fig. 2B). White blotches are more pronounced on the discoloured median area (Fig. 2B). Tentacles stout post-fixation (Fig. 2D), 5.7 mm from the anterior margin; each preserved tentacle 1.2 mm long; tentacular eyes visible at base. Pharynx ruffled, 2.6 mm long with 7–8 folds, situated in median of body. Male and female gonopores 0.4 mm apart in the lower half of the body below the last pharyngeal fold. Prostatic vesicle, cirrus sac, bursa copulatrix, male gonopore, female gonopore and Lang’s vesicle visible in the preserved specimen (Fig. 2C).
Male reproductive system includes prostatic vesicle with a cirrus sac (1 mm long) encased in thick muscular sheath opening to the outside via male gonopore (Fig. 3A; 4). Prostatic vesicle (625 µm long and 582 µm wide) with thick folded internal epithelium accepting spermiducal bulbs from both sides (Fig. 4). Cirrus sac conical, tapered towards male gonopore. Two muscular folds split it into two divisions (Fig. 3A). The first without teeth, connected to the prostatic vesicle to receive sperm; the second lined with teeth that open to the outside via male gonopore (Fig. 3A; 4).
Female gonopore connects to vagina bulbosa via ciliated female atrium and cement pouch (Fig. 3B, 4) surrounded by cement glands. The vagina bulbosa is higlhy muscularized (Fig. 3B). The bursa copulatrix, located on the side of gonopores (Fig. 2C) is not visible in histology sections. The lumen of the bursa copulatrix towards the posterior end of the body leads to Lang’s vesicle (Fig. 2C).
Taxonomic remarks
The newly described species differs from all the congeners based on dorsal colour pattern, arrangement and colour of marginal bands, absence of cerebral eyes and differences in reproductive structures. Only 4 Paraplanocera species are described from the Indian Ocean to date: P. aurora Laidlaw, 1903, P. langi (Laidlaw 1902), P. marginata Meyer, 1922, and P. oligoglena (Schmarda 1859).
Paraplanocera kalpeniensis sp. nov. differs from P. aurora in dorsal colouration pattern. Though both the species show pink colour on the dorsum, P. aurora is mottled with lines and spots of yellowish white, while P. kalpeniensis sp. nov. has a few white spots but no lines. There is no marginal band in P. aurora, while a marginal band is present in P. kalpeniensis sp. nov. The cirrus lumen is lined by two kinds of spines, large & irregular and small & thorn shaped (Laidlaw 1903, Pg. 102) in P. aurora while in P. kalpeniensis sp. nov. the lumen has medium-sized teeth (Fig 3A).
Paraplanocera kalpeniensis sp. nov. differs from P. langi in the shape of the tentacles, and dorsal colouration pattern. The background colour of P. langi is white with few black chromatophores in comparison to the pink background colour of P. kalpeniensis sp. nov. The tentacles in P. langi are described as slightly bilobed (Laidlaw 1902, pg. 286) while slender tentacles are observed in P. kalpeniensis sp. nov. the lumen of penis in P. langi is lined with chitinous, not very thickly hooked spines (Laidlaw 1902, pg. 287) while there are no such chitinous hooked spines in P. kalpeniensis sp. nov.
Paraplanocera marginata, described from the Red Sea, differs from P. kalpeniensis sp. nov. on the basis of the dorsal colour, the colour of the marginal band, and presence of spines in the cirrus sac of the former. Paraplanocera marginata has an orange-yellow dorsal surface with scattered white spots, while the dorsal surface of P. kalpeniensis sp. nov. is pink with a yellow hue near the margin (Fig. 2A). The marginal band of P. marginata is either purple (Meyer 1922) or black with a submarginal black band (Prudhoe 1989; Rodríguez 2021) but P. kalpeniensis sp. nov. has violet and purple marginal bands with a white rim (Fig. 2A). There are no teeth but only spines in the cirrus of P. marginata in comparison with P. kalpeniensis sp. nov. which possesses only teeth (Fig. 3A).
Paraplanocera oligoglena, described from Sri Lanka, differs from P. kalpeniensis sp. nov. by exhibiting a translucent body with a brown dorsal surface, while P. kalpeniensis sp. nov. has a pinkish colour on the dorsum with many white blotches (Fig. 2A). Paraplanocera oligoglena is also characterised by the presence of two large teeth in the cirrus sac while there are no such large teeth but many medium-sized teeth in P. kalpeniensis sp. nov. (Fig. 3A).
The key differences between all known species of the genus Paraplanocera are provided in Table 1.
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 407-411, DOI: 10.11646/zootaxa.5446.3.5, http://zenodo.org/record/11101945