Asajirus indicus ( Oka, 1913 )

Maggioni, Tamara, Rimondino, Clara, Taverna, Anabela, Reyna, Paola, Lagger, Cristian, Alurralde, Gastón, Calcagno, Emilia & Tatián, Marcos, 2022, Abyssal ascidians (Chordata, Tunicata) from the Weddell Sea, Antarctica, including a new Styela species and stomach content identifications, Zootaxa 5093 (3), pp. 296-314 : 310-311

Asajirus indicus ( Oka, 1913)

Figure 9

Hexacrobylus indicus Oka 1913: 6 .

Asajirus indicus: Kott 1989: 521-524 , fig. 1; Sanamyan K. & Sanamyan N. 2006: 339-342; fig. 19, and synonymy; Maggioni et al. 2018.

Hexadactylus indicus: Monniot C. & Monniot F. 1990: 271 , figs. 1I, 16.

Material examined: 70°40’S, 14°43’W, station 7, 3000 m, 22 Feb 2005, one specimen.

Description. The only specimen collected measures 3.1 cm long and 2.3 cm wide. With the exception of the oral lobes, the rest of the tunic is completely covered by detritus and sand. The ventral side has short and thin projections. The tunic is transparent, thin and flexible except for the region that surrounds the oral siphon, where it becomes thicker. Surrounding the oral aperture there are six prominent oral lobes with pinnate borders, two of which are bigger than the remaining four. The atrial siphon, situated at approximately one fifth of the distance from the oral siphon, consists of a tiny, almost unnoticeable, hole. The oral siphon is innervated by a series of longitudinal and circular very well developed muscle fibers. The elongated atrial siphon is also innervated by a series of thinner longitudinal and circular muscle fibers. There are no oral tentacles. Instead, there is a thick muscle cap arranged transversely across the first section of the oral siphon, except for a small dorsal orifice that connects directly with a prominent esophagus. The neural ganglion has two pairs of anterior nerves and one thick posterior nerve that divides into two thinner ones. There are two longitudinal bands of ventral muscles that extend on each side of the mid ventral line of the body and join at the posterior end, and a series of thinner concentric circular fibers on each side of the mid-dorsal region of the body. The rest of the mantle is transparent and thin. The pharynx is short and has two circular perforations that connect with lateral pharyngeal chambers which, in turn, open to the atrial cavity. The stomach occupies the totality of the ventral region. It is connected with a big and plicated hepatic pouch situated over it through a short duct. The gut-loop is closed. The border of the anus has two lobes. The ovoid renal sac is situated ventrally, between the oral siphon and the gut. There is one gonad on each side of the body. The ovaries, tubular and slightly curved, are full of yellowish ovocytes. The gonoducts are short and open near the anus. The testicular follicles are composed of numerous whitish lobes at the distal ends of the ovaries. The sperm ducts are also short and open directly into the atrial cavity.

Stomach contents. In the stomach of this specimen we found: one fragment of a copepod (undet.); a head fragment of another copepod (undet.); and a Brachyura zoea larva.

Remarks. This is the first register of the species in the Weddell Sea. Asajirus indicus has one of the largest known geographic ranges within Ascidiacea.

Figures

FIGURE 9. Asajirus indicus.