Styela cearense Filho & Lotufo, 2015, n. sp.

Styela cearense n. sp.

(Figures 1–4)

Nomenclatural act at Zoobank: A8D7CFC0-9CD2-4DD1-9A0C-D845A7A31CFD

Type material. Holotype: MZUSP 0 0 122, artificial pilings at the Praia da Pedra Rachada, Paracuru, Ceará State (03°23’53.03”S; 039°00’54.03”W), about 80km western Fortaleza city, ~ 2m depth, in November 21 th 2011.

Paratypes: five specimens from same date and location are deposited at MZUSP under numbers 0 0 123 to 0 0 127. Etymology. The specific name refers to the Brazilian state (Ceará) where this species was collected.

External appearance. The specimens measure up to 8mm long with tunic. They were removed from the substratum with other members of the local fouling community, such as barnacles, hydroids and sponges, but also other colonial ascidians. Tunic color is light brown, thin, but tough and resistant, and is covered with fouling (Fig.1), including small filamentous algae. The tunic surface is slightly wrinkled, with some projections especially at the anterior region. Individuals were found very close to each other, but the adhering tunic surface among them can be readily separated.

Internal morphology. Individuals are about 3–4mm long without tunic. The body wall is thin and translucent, allowing seeing the internal organs. White pigmented patches are present on the external and internal walls of both siphons. Siphons are tubular, short, and close to each other, but the presence of lobes could not be clearly detected. Branchial siphon is smaller and apical, while the atrial one is located more laterally. Many fine, small tentacles (more than 80) are present at the base of the atrial siphon, concentrated in the dorsal portion (Fig. 2 A). Small scales with two spines (~6,25µm) lining the atrial velum and reflex tunic of the branchial siphon (Fig. 2 B). Fine muscular bands present in almost the whole body wall, except on the most ventral portion, arranged toward the siphons as a network. There are 22–36 filiform oral tentacles, of three or four size orders. The neural gland is short, occupying half of the dorsal portion. Dorsal tubercle is round and salient with an opening varying from a simple oval form to a C shape (Fig. 3). The peripharyngeal band is a single lamella forming a dorsal “V” that continues in a slender, smooth edged dorsal lamina. The branchial sac has four well-developed folds on both sides, with longitudinal vessels varying between 33–40 on left, and 29–41 on right side. The branchial formula of the holotype and two paratypes are:

There are 3–6 stigmata per mesh, crossed by parastigmatic vessels (Fig. 2 C), being 3 stigmata per mesh most often observed. The gut has primary and secondary loops, occupying about half of the body length, firmly attached to the body wall by strong tissue connections. Oesophagus is relative long, sometimes straight, not curved. The yellowish stomach is slightly elongated, with 22 longitudinal folds, a finger-like gastric caecum at the posterior end, and a gastro-intestinal connective tissue between the posterior section of the stomach and the mid-section of the intestine, crossing over the primary gut loop. The anus opens near the base of the atrial siphon, with a smooth edge, but it may look slightly lobed due to contraction (Fig. 2 D). Endocarps varying in number from 7–21, slender, attached to the body wall, but never on the gonads—one of them always present into the primary intestinal loop; the number of endocarps seems to be variable by side and individual size as well. Two hermaphroditic gonads are attached to the body wall, located laterally, being one gonad on each side of body (Fig. 4); ovary is yellowish, cylindrical and elongated, generally curved, and filled by many small oocytes; testis follicles are whitish, irregular shaped, arranged along the middle but mainly on the distal part of the ovary—there is rarely a follicle on its proximal section. The number of follicles was always larger on the right side (12–13) than on the left side (9–11).

Remarks. Of all 73 species of Styela currently known, 29 species (~40%) have one gonad on each side of body, almost all of them described from cold and deep waters of the Indo-Pacific Ocean. Of these, twelve species also have four branchial folds and were thoroughly compared with Styela cearense in order to establish its singularity. A tabular key for all Styela species with a single gonad on each side is presented in order to enable direct comparisons and allow their identification (Tab. 1).

The Atlantic Styela similis Monniot, 1970 is the most similar to S. cearense. This first species was described from deep waters of the Gulf of Gascony (Monniot, 1970), and also reported from Biaçores (Monniot & Monniot, 1973), but it has usually less oral tentacles, a smaller stomach, with a different caecum, lobed anal border and a different gonad structure (up to 20) that make them clearly different.

Other known species that present one gonad plus four branchial folds on each side of the body are significantly different from S. cearense: Styela calva Monniot, Monniot and Millar, 1976 does not have endocarps and present less stomach folds (Monniot, Monniot, & Millar, 1976); Styela coriacea (Alder & Hancock, 1848) has much less stomach folds, more oral tentacles and lobed anus (Tokioka, 1967; Van Name, 1945); Styela gelatinosa (Traustedti, 1886) is larger, with more stomach folds and numerous rounded testis follicles (Millar, 1966; Van Name, 1945); Styela izuana (Oka, 1934) has long atrial tentacles, pyloric caecum absent, and testis follicles arranged along the whole ovary (Tokioka, 1953, 1967); Styela macrenteron Ritter, 1913 is larger, with more stomach folds, as well as oral tentacles and stigmata per mesh (Van Name, 1945); Styela monogamica Oka, 1935 has only one testis follicle and pyloric caecum absent (Oka, 1935); Styela multitentaculata Sanamyan and Sanamyan, 2006 is smaller, with a dorsal lamina slightly toothed and lobed anus (Sanamyan & Sanamyan, 2006); Styela rustica Linnaeus, 1767 is larger, with the stomach not very regularly plicated, less oral tentacles, and gonads with a sinuous ovary plus a large ovoid testis follicle (Millar, 1966; Van Name, 1945); Styela squamosa Herdman, 1881 has more stomach folds, a large testis follicle and lobed anal margin (Sanamyan & Sanamyan, 2006); Styela tholiformis (Sluiter, 1912) has a different kind of gonad, with the male follicles exclusively on the distal-tapered part of the ovary (Van Name, 1945).

? = undescribed character

Reference: 1 —Bonnevie 1896; 2 —Sluiter 1904; 3 — Sluiter 1912; 4 — Ritter 1913; 5 — Oka 1935; 6 — Van Name 1945; 7 — Tokioka 1953; 8 —Tokioka 1963; 9 — Millar 1966; 10 — Tokioka 1967; 11 — Monniot & Monniot 1968; 12 —Kott 1969; 13 — Monniot & Monniot, 1970; 14 —Millar 1970; 15 — Monniot 1970; 16 — Monniot & Monniot 1970; 17 — Monniot 1971; 18 — Monniot & Monniot 1973; 19 —Millar 1975; 20 — Monniot, Monniot & Millar 1976; 21 — Monniot 1978; 22 — Millar 1982; 23 —Monniot & Monniot 1985; 24 —Monniot & Monniot 1988; 25 —Monniot & Monniot 1991; 26 — Monniot 1993; 27 —Monniot 1994; 28 —Young & Vazquez 1997; 29 —Sanamyan & Sanamyan 1999; 30 —Monniot 2002; 31 —Monniot & Monniot 2003; 32 — Sanamyan & Sanamyan 2006; 33 —Sanamyan & Sanamyan 2012.