Phrikoceros mopsus ( Marcus, 1952 )

Bahia, Juliana, Padula, Vinicius & Delgado, Marlon, 2012, Five new records and morphological data of polyclad species (Platyhelminthes: Turbellaria) from Rio Grande do Norte, Northeastern Brazil, Zootaxa 3170, pp. 31-44 : 35-36

Phrikoceros mopsus ( Marcus, 1952)

( Fig. 3 )

Material examined and locality. One juvenile specimen (12 mm x 11 mm) preserved in ethanol 70%. Collected 9 March 2009 (MNRJ-PLAT 08). One mature specimen (17 mm x 11 mm) as sagittal sections of reproductive structures. Collected 11 March 2009 (16 slides, MNRJ-PLAT 09).

Two mature specimens (12 mm x 7 mm and 7 mm x 8 mm) preserved in ethanol 70%, collected 11 March 2009 (MNRJ-PLAT 10). All specimens collected at Brazil, RN, Extremoz, Praia de Santa Rita, 0 5o 41’44’’S, 35o11’39’’W, intertidal, under rocks.

Distribution. Originally described from Ilha de São Sebastião, São Paulo State ( Marcus 1952) and herein reported from Rio Grande do Norte State, Brazil. Also known from Antigua, Curaçao ( Marcus & Marcus 1968), Barbuda, Colombia ( Quiroga et al. 2004a) and Argentina ( Brusa et al. 2009; Bulnes et al. 2011). This species is considered as representative of reef habitats ( Rawlinson 2007).

Diagnosis. Body oval and elongated with deeply ruffled margin. dorsal region with reticulated, mottled pattern with white spots; median line darker than the rest of the body; margin with a dark line; four pseudotentacular eyespots groups located dorsally, four ventrally; main intestine entrance located in the anterior half of the body.

Description. Color: Background cream with brown reticulate pattern ( Fig. 3 A), combined with a mottled pattern of white spots ( Fig. 3 B). These white spots are better viewed in dark background. The body median line and pseudotentacles are of a darker brown. Dark line present throughout the body margin and only interrupted at pseudotentacle tips ( Fig. 3 A e 3B). Cerebral region and ventral surface uncolored. Form: Oval with deep ruffled margin characteristic of the genus ( Fig. 3 A).

Tentacles: Square-shaped simple folds of the margin with 1.3 mm length.

Eyespots: Cerebral eyespots located at 0.9 – 1.0 mm from the anterior margin. They extend through 0.2–0.3 mm and form a horseshoe shaped cluster. This cluster is densely formed and has about 35 ocelli. Tentacle eyespots are disposed in four ventral and four dorsal clusters. These clusters are of two types: located between the proper tentacle folds and located in the marginal fold that forms the tentacle. There is one of each cluster type in each tentacle both ventrally and dorsally. Dorsal pseudotentacular eyespots are about 30 in each cluster and ventral clusters have about 70 eyespots.

Digestive system: Pharynx ruffled with six simple folds. It reaches 3 mm length and it is 2 mm distant from the anterior margin. It is possible to distinguish the pharynx and main intestine in the dorsal view of the animal ( Fig. 3 A). Mouth opens at 2.5 mm from the anterior margin. Main intestine opens above the male reproductive system, extending posteriorly to the sucker and ending prior to the posterior margin.

Epidermis and body wall: Large sucker (0.5 mm) 1.2 mm distant from the female gonopore ( Fig. 3 D). Ventral epithelium (0.03 mm) slightly taller than the dorsal (0.02 mm). Both well developed. Rhabdites and pigment granules can be seen in the dorsal surface. Cilia better developed and rhabdites scarcer on the ventral surface. Muscular layers thin (0.009 mm dorsally and 0.017 mm ventrally) and composed by longitudinal, circular and diagonal fibers. Under the epidermis and muscular layers there is a loose parenchyma.

Gonopores: One male and one female gonopore present ( Fig. 3 D). Each measures 0.5 mm. Male gonopore 4.5 mm distant from the anterior margin. Female pore lies right behind the male gonopore. This distance can be longer, as described by Brusa et al. (2009), but in our specimens it is very short probably due to variations in fixation or specimen size.

Male reproductive system: One male system partially located under pharyngeal folds. Testes ventrally located ( Fig. 3 D). Seminal vesicle oblong and 0.39 x 0.24 mm large. Prostatic vesicle round (0.13 x 0.12 mm). This structure is anterior to the seminal vesicle and slightly dislocated to the left side of the body. Their ducts join near the penis papilla (0.18 mm). Penis papilla has a sclerotized stylet 0.1 mm long ( Fig. 3 C). Shallow male atrium (0.19 mm).

Female reproductive system: Short vagina (0.21 mm) surrounded by numerous cement glands ( Fig. 3 C). Cement pouches as shallow invaginations 0.07 mm from the female gonopore. Expanded oviducts containing eggs ( Fig. 3 C). Although smaller than other Phrikoceros mopsus specimen ( Brusa et al. 2009), our specimens were sexually mature and had oviducts full of eggs. These eggs had 0.08 mm diameter.

Taxonomic remarks. After Faubel’s (1984) revision, Newman & Cannon (1996) created the genus Phrikoceros . It has as diagnostic features deep marginal ruffles, simple pharyngeal folds and the arrangement of ventral and dorsal pseudotentacular eyes into distinct clusters. Quiroga et al. (2004b) recognized that Pseudoceros mopsus Marcus, 1952 has these characteristics and so reallocated the species to the genus Phrikoceros . Our results also corroborate this decision. Our specimens disagree from those of Brusa et al. (2009) in the distance between gonopores. This could be due to size of specimens, as our specimens are up to 17 mm long and theirs were 50 mm long, or to differences in body contraction during fixation. Bulnes et al. (2011) specimens are also large and have some differences related to our specimens. There are differences in coloration pattern, absence of rhabdites, body wall thickness and egg size. Mar del Plata specimens ( Bulnes et al. 2011) differ from those described by Brusa et al. (2009) and from our specimens on the muscular layers (theirs specimens outer muscular layer is circular), the junction of the ejaculatory and prostatic ducts (at the penis base in our specimen not at the stylet base) and spermiducal bulbs lacking. Those disparities between specimens may be not related to the size of specimens, as Brusa et al. (2009) described larger specimens than Bulnes et al. (2011), Marcus (1952) and this work. Molecular tools and more detailed comparative anatomic studies may clarify this question.

Figures

FIGURE 3. Phrikoceros mopsus. A – B (MNRJ-PLAT 08). A— in vivo, dorsal view; B— in vivo, dorsal view of specimen on a dark surface, with the mottled pattern of white spots visible. C – D (MNRJ-PLAT 09). C— sagittal section with indication of reproductive structures; D— ventral structures. cg: cement gland; fa: female antrum; fg: female gonopore; it: main intestine; ma: male atrium; mg: male gonopore; ph: pharynx; pt: pseudotentacles; st: stylet; su: sucker; sv: seminal vesicle; ut: uteri; vs: vas deferens.