Stolonica Lacaze-Duthiers and Délage, 1892

KOTT, PATRICIA, 2003, New syntheses and new species in the Australian Ascidiacea, Journal of Natural History 37 (13), pp. 1611-1653 : 1642-1643

Genus Stolonica Lacaze-Duthiers and Délage, 1892 (Polyzoinae, Styelidae ) Stolonica aluta Kott, 1985

(figure 10A–C)

Stolonica aluta Kott, 1985: 233 .

Distribution. A newly recorded specimen (WAM 107.93) is from the type locality

(off Cliff Head, Dongara, Western Australia).

Description. The specimen is an upright egg-shaped zooid with sessile apertures (the branchial terminal and atrial antero-dorsal), narrowing posteriorly to a short thick basal keel-like hollow, sandy process into which the body wall projects. A spherical outgrowth, separated from the ventral part of the test by a narrow constriction, does not appear to be an incipient bud. The test is tough, smooth, white and opaque in preservative with some sand embedded in it. The body wall adheres closely to the test and has a thin outer coat of crowded transverse muscles and some inner longitudinal bands. Small endocarps are scattered on the internal pallial body wall. About 20 branchial tentacles of even length are regularly spaced. The small dorsal tubercle in a shallow peritubercular area has a reversed C-shaped slit. The branchial sac has four low, rounded folds per side, with crowded internal longitudinal vessels arranged as follows: E7(9)6(8)5(12)5(7)3DL5. The rounded gut loop lies transversely across the posterior part of the body with the rectum extending anteriorly almost at right angles to it. Half of the proximal limb of the gut loop is a cone-shaped stomach, expanding distally, divided into 20 folds, those in the gut loop projecting away from the stomach as a slight spur from which the suture line, along the outside of the spur, continues in a conspicuous gastric caecum curved into the pole of the gut loop. A narrow connective is between the outer curve of the caecum and the inner margin of the distal limb of the gut loop. Twelve hermaphrodite gonads consisting of a short sac-like ovary with four or five eggs over a single testis follicle are in an arc near the mid-ventral line (parallel to the endostyle) on the right side of the body.

Remarks. Although generally the same shape as the type material, the present specimen has a smooth rather than irregularly wrinkled surface, four rather than three branchial folds; and hermaphrodite gonads in a row on the right side only. In the type material, an arc of male follicles is present on each side of the body with ovarian sacs mixed with them on the right. However, the gut loop in the present specimen is identical with that in the type zooids and numbers of internal vessels per side are similar (about 60), even though there is an additional fold in the newly recorded specimen. The difference noted in the gonads, namely the absence of any gonads on the left and the close association of male and female gonads in hermaphrodite ones, probably relates to the variability and ephemeral nature of the gonads already observed in this subfamily (see Kott, 1990b).