Pseudoceros auranticrinis Dixit, Raghunathan & Chandra, 2017, sp. nov.

Pseudoceros auranticrinis sp. nov.

(Figures 2–5)

Type material. Holotype: One specimen (19 × 9 mm) as serial sections (3 Slides), remainder of animal in 70% ethanol. Collected on 16.12.2015, subtidally at 10 m depth; Kamorta Island (Lat: 08°02.159’N, Long: 93°32.951’E), Andaman and Nicobar Islands, India (ZSI/ANRC-14836).

Distribution. Species only known so far from type locality.

Diagnosis. Background colour of dorsal surface is light cream. Except margins, rest of the body is mottled with brown; numerous white and dark brown spots all over the brown shaded area (Fig.2); median region dark coloured and a very thin and faint orange median line is visible. Pseudotentacles orange (Fig. 3A) with some white spots. Numerous blue spots on margins.

Etymology. Named from Latin; aurantius (adj.) = orange, crinis = tentacle.

Description. Live. Body elongate, slightly tapering at posterior side and smooth at margins without ruffles. Background body color white to cream with brown shading all over body except margins; darker medially; very faint, thin, broken orange median line is visible which starts from anterior half of the body and runs till posterior end without touching margin; on close examination, a thin white line also visible in median region which starts right from cerebral eye spot and faints off near mid portion of body. Numerous white and brown spots present all over the coloured area; white mottling visible in posterior region (Fig. 3A). Pseudotentacles made from simple folds of anterior margin, orange in color with some white spots; numerous eyespots present on ventral side (Fig. 3 C). Margin speckled with blue spots of variable sizes.

Preserved. Cerebral eyespot cluster with about 46 eyes (Fig. 3 D). Ventrally cream in colour with clearly visible ruffled pharynx, pharyngeal mouth, male pore, female pore, sucker and intestine (Fig. 3 B). Preserved specimen cream coloured due to loss of pigments during fixation. Male and female pore are 1.12 mm apart while female pore and sucker are 1.23 mm apart. The total distance between pharyngeal mouth and sucker is 4.38 mm. Pharynx ruffled with seven folds and male pore is situated between last pair of pharyngeal folds. Body wall composed of ciliated epithelium that surrounds the entire body. A distinct but very thin basement membrane separates epithelial cells from underlying muscular layers. Dorsally, thickness of epithelium varies from 50–55 µm while ventrally it is 35–40 µm.

Reproductive characters. Measurements refer to length in a 19 mm long worm, the holotype. A large, oblong and heavily muscularized seminal vesicle (644 × 409 µm) is present (Fig. 4 A and 5). Adjacent to it, rounded and thick layered prostatic vesicle (232 × 159 µm), straight above the penis base is present. Seminal and prostatic vesicle are situated in one plane and perpendicularly oriented to each other. Penis papilla conical in shape and 500 µm long with a small stylet. Male atrium ciliated with long flanking regions on both the sides. Female atrium 294 µm long with presence of cement pouch and cement glands (Fig. 4 B and 5). Vagina 454 µm long and oriented towards posterior region with highly nucleated wall.

Taxonomic remarks. Presence of characters like ruffled pharynx, one male pore, arrangement of eyes, smooth body, margin without ruffles and equal distance between gonopores place this newly described species in the genus Pseudoceros under the Family Pseudocerotidae. Pseudoceros auranticrinis sp. nov. exhibit no similarity with any of studied species in the genus Pseudoceros in terms of dorsal color pattern (Lang 1884; Laidlaw 1902; Prudhoe 1978, 1989; Hayman 1959; Kato 1934, 1937, 1938, 1944; Newman and Cannon 1994, 1996, 1997, 1998, 2003, 2005; Tayler et al. 2016) except Pseudoceros goslineri, which also exhibit more or less similar mottling and spots pattern but it differs from newly described species in colour of pseudotentacles, margins and ventral surface (pink).

In terms of marginal pattern, P. auranticrinis sp. nov. possesses margin made up of blue spots, quite similar to margin of P. indicus Newman & Schupp, 2002, P. laingensis Newman & Cannon, 1998 and P. vishnui sp. nov. described in the next section but none of the above-mentioned species show any similarity with newly described species in any other characters externally, especially the colour of pseudoctentacles. The difference in colour of pseudotentacles with respect to marginal colours is a unique character which is not common among Pseudocerotids. In almost all members of the genus Pseudoceros, the color of pseudotentacles remains in continuity with that of margin except in Pseudoceros sp. 2 and 13 (Newman and Cannon, 2005) which also possess different coloured pseudotentacles. Based on above mentioned characters, Pseudoceros auranticrinis sp. nov. is considered as a new species.