Stylostomum mixtomaculatum Pitale & Apte 2019, sp. nov.
Creators: name: Pitale, Reshma
name: Apte, Deepak
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Rhabditophora
Polycladida
Euryleptidae
Stylostomum
Stylostomum mixtomaculatum

description: Stylostomum mixtomaculatum sp. nov.   
(Figure 8, 9)  
 Etymology: ‘ mixtum ’ meaning mixed, ‘ maculatum ’ meaning having maculae or blotches. Two kinds (dark and light) of maculae found on the dorsal surface.   
 Type material: Holotype: One specimen (BNHS-Pclad 034, 3.1 mm x 2.39 mm) as sagittal sections of reproductive structures (41 slides). Collected 14-2-2012 at Undi—type locality.   
Species also reported from Mandvi, Ratnagiri, Poshitra (22.418975° N 69.228166° E) and Dwarka (22.240323° N 68.957424° E) in Gujarat, west coast of India.  
 Paratype: One specimen (BNHS-Pclad 0200, 3.19 mm x 2.36 mm), intact, collected on 14-2-2012 at Undi; One specimen (BNHS-Pclad 0201, 3.72 mm x 2.79 mm) collected on 1-11-2012 at Mandvi, Ratnagiri.   
 Distribution: This species is so far known only from its type locality and other areas as mentioned above.   
 Diagnosis: Oval, translucent creamish-buff dorsal surface with black minute spots arranged in a circular manner forming maculate appearance. Minute white dots found across the dorsal surface; margin clear.   
 Description:   
Colour: Semi-transparent creamish body, appears buff-primrose yellowish when fully fed and intestinal branches are full of food material (Fig. 8A). White minute dots found evenly distributed over dorsal surface; sometimes continue to be present on the margin. Several brown-black minute dots organised in circular manner forming maculae, found arranged unevenly on the dorsal surface. Some of these dots are tightly packed and dark, and become prominent whereas most of the blotches appear comparatively light (Fig. 8A, B and C). These maculae show prominent dotted border. All the specimen showed a combination of dark-light maculae. Milky white specks in some specimen were noticed representing ovaries. Margin clear and ventral surface cream colour.  
Form: Circular, elongated while creeping.  
Pseudotentacles: reduced but minute stumps observed only during creeping.  
Eyespots: Two small groups of cerebral eyespots (4 prominent ocelli) in a colourless area, 0.46 mm from the anterior margin (Fig. 8D). Cluster is about 0.17 mm. At dorsal, fore-end eye cluster contains 15–18 ocelli, found extended along the margin up to the length of cerebral eye cluster.  
Digestive system: Pharynx typical of the genus, tubular (0.51 mm) opens into the main intestine (Fig. 8G). 7–8 lateral intestinal branches are seen, and anterior branch. This frontal extension of main intestinal branch reaches almost half the length of the pharynx (Fig. 8G, 9B). Lateral branches sub-divided.  
Gonopores: Mouth and one male gonopore common (Fig. 8C and 9B), present 1.02 mm distant from anterior margin, measuring 0.082 mm. Female gonopore 0.24 mm behind the male gonopore/mouth and 1.22 mm distant from anterior margin, measuring 0.057 mm. (Fig. 8C, E)  
Male reproductive system: (Fig. 8F and G, 9B) Large oval seminal vesicle (0.28 x 0.096 mm) found arranged slightly perpendicular to the ventral body wall. Small rounded prostatic vesicle (0.06 x 0.07 mm), placed below the pharynx and ventral to the seminal vesicle. Short ejaculatory duct extends forward, unites with prostatic duct and passes into the slender pointed penis.  
Female reproductive system: (Fig. 8F, 9B) Wide-oval female atrium (0.11mm) enters into a vagina with deep lateral invagination (0.07 mm) for cement pouches. Cement glands are seen densely disposed. Vagina extends dorsally (0.07 mm), turns posterior and subsequently opens into the uterine spaces. Uterine vesicle (0.19 x 0.14 mm) visible. Two elongated uteri filled with oocytes appear on either side of the median line (Fig. 9A) and in some specimen, are visible through ventral surface (Fig. 8C, E).  
 Taxonomic remarks. The presence of a common opening for mouth and male copulatory apparatus, uterine vesicles and uteri, absence of anastomoses but subdivisions of the intestinal branches and presence of a frontal extension of the intestine place this species in the genus Stylostomum. In terms of the number of cerebral and pseudotentacular eye spots, S. mixtomaculatum sp. nov. resembles S. sanjuania. Otherwise the new species markedly differs from other valid species of this genus in terms of colour patterns, number of cerebral eyespots and pseudotentacular eyespots.   
 Faubel (1984) described the genus Parastylostomum as varying from Stylostomum by having postero-ventrally oriented prostatic vesicle and absence of uterine vesicles. S. mixtomaculatum sp. nov. resembles Parastylostomum maculatum in terms of the number of cerebral eyespots.   
 The specimens were always seen over the compound ascidian Eudistoma sp. and even egg mass was noticed. Moreover, the colouration (primrose yellowish) observed within the specimens matched exactly with the Eudistoma sp. (Fig. 9C, D, E).
description: Published as part of Pitale, Reshma & Apte, Deepak, 2019, Intertidal Euryleptid polyclads and description of a new Stylostomum Lang, 1884 from Maharashtra, India, pp. 317-339 in Zootaxa 4652 (2) on pages 328-329, DOI: 10.11646/zootaxa.4652.2.5, http://zenodo.org/record/3363816