Stolonica styeliformis Van Name, 1918

Kott, Patricia, 2005, Novel Australian Polyzoinae (Styelidae, Tunicata), Journal of Natural History 39 (32), pp. 2997-3011 : 3004-3006

Stolonica styeliformis Van Name, 1918

( Figure 2 ) Stolonica styeliformis Van Name 1918, p 107 ; Tokioka 1967, p 165; Millar 1975, p 278.? Amphicarpa duploplicata: Kott 1972, p 50 .

Distribution

New record: Northern Territory (Gulf of Carpentaria, 16 ° 37.30 9 S, 140 ° 10.871 9 E, trawled sample no. 372, coll. CSIRO, QM G308759). Previously recorded: Northern Territory (Gulf of Carpentaria, Kott 1972); Philippines ( Van Name 1918; Tokioka 1967; Millar 1975).

Description

Zooids are small, sandy, rounded, spherical to oval or triangular in outline, to 1.0 cm maximum dimension. Each is connected to a network of basal stolons by a short stalk, the test is thin, translucent and flaccid, and sand is embedded in the surface, entirely covering the zooids and their stalks. Some brown pigment is in the test at the anterior end of the body. Apertures are close together on the upper surface. The body wall adheres closely to the internal layer of test and is separated from it only with difficulty. Two branchial folds are on each side of the body and sometimes an incipient third fold, consisting of crowded vessels that spread out posteriorly, is in the ventral part of the branchial sac. A branchial formula is E1(4)2(10)4(6)3DL1(8)3(5)1(4)E. Four stigmata are in a mesh in the centre of one side of the branchial sac. An S-shaped vertical slit is on the dorsal tubercle. The gut is thick and forms a relatively short loop across the posterior end of the body with the rectum turning anteriorly almost at right angles to it. The relatively short stomach with about 16 gastric folds occupies the middle third of the proximal limb of the gut loop. The anus is bilabiate. The distal end of the stomach is connected with the distal limb of the gut loop by a short ligament. Rows of endocarps are on the body wall on each side. Neither gastric caecum nor gonads were detected in the newly recorded specimens, which appear to have been frozen.

Remarks

The majority of the specimens doubtfully assigned to Amphicarpa duploplicata: Kott, 1972 from the Gulf of Carpentaria appeared to have been dried out and only the external test is present. The internal organs were determined from only one specimen from a different location. Only two branchial folds were reported and it is probable that a third incipient fold, as in the present specimens, could have been overlooked .

The type specimens from the Philippines, like those reported by Millar (1975) and Tokioka (1967), are similar to the Northern Territory specimens, being sandy, upright zooids attached to basal stolons by short vertical stalks and with the body wall closely adherent to the test. The dorsal tubercle has a vertical slit. The branchial sac has similar numbers of internal longitudinal vessels and stigmata per mesh and Millar (1975) did find a specimen with incipient second and most ventral (fourth) folds. The gut is thick forming a short loop with the rectum turned anteriorly. The anal border is smooth as in the present specimens. A small gastric caecum was detected only in the specimens Millar (1975) examined. Gonads, consisting of small ovarian sacs in a row along each side of the mid-ventral line and groups of single pear-shaped male follicles scattered on the body wall, are present in the Philippine specimens.

Both Van Name (1918) and Tokioka (1967) report especially large, robust colonies with four brown longitudinal bands in the test radiating from the branchial siphons. These are not reported by the other authors and although brown pigment is in the test around the anterior end of the body, bands of pigment were not detected in the present zooids.

Figures

Figure 2. Stolonica styeliformis (QM G308759). (A) External view of zooids; (B) internal pallial body wall on right. Scale bars: 2 mm (A); 1.0 mm (B).