Enchiridium evelinae Marcus, 1949

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 : 33-34

Enchiridium evelinae Marcus, 1949

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Material examined and locality. One mature specimen (17 mm x 7 mm) as sagittal sections of reproductive structures (13 slides, MNRJ-PLAT 05). One juvenile specimen (11 mm x 3 mm) preserved in ethanol 70% (MNRJ- PLAT 06). Both collected 11 March 2009 at Brazil, RN, Extremoz, Praia de Santa Rita, 0 5o 41’44’’S, 35o11’39’’W, intertidal, under rocks. One specimen (14 mm x 6 mm) preserved in ethanol 70%. Collected 12 March 2009 at Brazil, RN, Nísia Floresta, Praia de Búzios, 0 6o 00’41’’S, 35o06’24’’W, intertidal, under rocks (MNRJ-PLAT 07).

Distribution. Originally described from São Paulo State, Southeastern Brazil ( Marcus 1949) and now reported to Rio Grande do Norte State, Northeastern Brazil. It is also known from Curaçao ( Marcus & Marcus 1968). This species is considered by Rawlinson (2007) as representative of seagrass habitat. We found our specimens both in a rocky shore dominated by ascidians and in another with algae, sponges and bryozoans.

Diagnosis. Body long and narrow; dorsal region cream colored with brown dots, more densely disposed in the median line; margin with orange dots; pharynx reaches 1/3 of the body length; seminal and prostatic vesicles highly muscularized; penis papilla and male atrium long.

Description. Color: Whitish body with brown dots; more densely located in the median line of the body. Yellow dots are also present ( Fig. 2 A) at the margin and between the brown dots of the main body. These dots disappear after fixation, and according to Marcus (1949), are lipoids.

Form: Body elongated and narrow. Anterior end rounded and posterior end somewhat bluntly pointed.

Tentacles: Absent.

Eyespots: Cerebral eyespots in two clusters ( Fig. 2 B). Each one presents 18 – 30 eyespots. Ocelli number apparently varies according to size. Each cluster extends through 0.5 mm. They are 1.5 – 1.1 mm from the anterior margin. Marginal eyespots form a scattered band that reaches 1.1 mm from the cerebral eyespots ( Fig. 2 B). This band begins at 0.1 mm from the margin and contains approximately 75 eyespots on each side until the brain level. After the brain, marginal eyespots get scarce and are disposed in a single row. In our specimens they do not reach the posterior end.

Digestive system: Pharynx voluminous and tubular; begins right behind the clusters of cerebral eyespots at 2.0 – 1.5 mm from the anterior margin. It is 3.5 mm long. Mouth opens at 1.5 – 2.0 mm of the anterior margin ( Fig. 2 C). Main intestine begins anteriorly to the gonads.

Epidermis and body wall: Below the thin ciliated epidermis there is a thick muscular layer that gives the animal its firm consistence. Ventral body wall thicker (epidermis 0.02 mm and muscular layer 0.09 mm) than the dorsal body wall (epidermis 0.01 mm and muscular layer 0.08 mm). Muscular layers are disposed as follow: diagonal, circular layer and longitudinal layer. Rhabdites visible and abundant on the dorsal surface. Sucker lies 7.5 mm from the anterior margin ( Fig. 2 C) is muscular, glandular and 0.2 mm large. Glandular mucous cells are present dorsally.

Gonopores: One male and one female gonopore present. Male gonopore is 5.7 mm distant from the anterior margin. Female gonopore is 1 mm distant from male gonopore ( Fig. 2 C).

Male reproductive system: Long penis papilla (0.31 mm) and stylet (0.02 mm) bent backwards ( Fig. 2 D). This makes the male atrium almost parallel to the body. Male atrium extends for 0.62 mm and its wall have about five folds. Accessory and prostatic vesicles spherical and muscular. Prostatic vesicle reaches 0.31 x 0.33 mm and located anteriorly to the seminal vesicle. Ejaculatory duct and sperm duct join in front of the prostatic vesicle. These ducts are also muscularized. Seminal vesicle oval, highly muscular and 0.4 x 0.6 mm large.

Female reproductive system: Vagina short and ciliated (0.29 mm) with extensions directed to the cement glands, in the cement pouches ( Fig. 2 D). Cement pouches 0.05 mm long. Uteri connect to the vagina anteriorly.

Taxonomic remarks. Most characteristics of our specimens fit the ones in the original description of E. evelinae ( Marcus, 1949) . The fact that in our specimens marginal eyespots do not reach the posterior end is in accordance with Marcus & Marcus (1968), who state that only larger animals have marginal eyes reaching the posterior end. The number of cerebral eyespots is also lower, probably because our specimens are smaller than those of the original description ( Marcus 1949). The two Western Atlantic Enchiridium species have the observed dotted coloration pattern and a long penis papilla. This had led to misidentification ( Hyman 1955). Marcus & Marcus (1968) pointed out that Enchiridium periommatum has a shorter pharynx (13% of the body length) compared to E. evelinae (26% of the body length). Our specimens fit the E. evelinae definition also in the distance between the cerebral and marginal eyes and in the length of the penis papilla, which distinguishes this species from other of the genus.

Figures

FIGURE 2. Enchiridium evelinae (MNRJ-PLAT 05). A— in vivo, dorsal view; B— anterior region with cerebral and marginal eyespots; C— ventral structures; D— sagittal section with indication of reproductive structures. ce: cerebral eyespots; cg: cement gland; cp: cement pouch; fg: female gonopore; it: main intestine; ma: male atrium; me: marginal eyespots; mg: male gonopore; mo: mouth; ph: pharynx; pv: prostatic vesicle; st: stylet; su: sucker; sv: seminal vesicle; ut: uteri; va: vagina.