Pyura dalbyi, Rius, Marc & Teske, Peter R., 2011

Rius, Marc & Teske, Peter R., 2011, A revision of the Pyura stolonifera species complex (Tunicata, Ascidiacea), with a description of a new species from Australia, Zootaxa 2754, pp. 27-40 : 33-35

Pyura dalbyi n. sp.

Figs. 5–8

Material examined. Specimens were found subtidally under a jetty in Albany harbour, Western Australia ( Table 1). Holotype: SAM-A25988, Paratype: SAM-A25989.

Description. Individuals are squat with an extended base ( Fig. 5 A). Their maximum dorsal length ranges from 35 to 95 mm, their height (measured from the base to the top of the siphonal area) from 35 to 60 mm, and their width (measured in contracted individuals) from 25 to 50 mm. The tunic is smooth (no pointed papillae on the tunic) ( Figs. 5 A, B, C), with few epibionts, and not as thick and tough as that of the African representatives of the P. s t o l o n i f e r a species complex. The individuals examined were attached to one another, forming a dense aggregate. Siphonal spines are long and pointed, and their bases are slightly expanded ( Figs. 6 A, B). The inner half of the siphonal lining is iridescent when observed under a dissecting microscope ( Fig. 6 C).

The animal has a fleshy body wall that is light orange in colour. The body size ranges in maximum length from 30 to 85 mm and in width from 20 to 45 mm. There are circular muscular bands around the siphons and the anterior longitudinal bands are present across the body wall and do not cross over each other.

There are 17 to 32 ramified oral tentacles of different sizes (alternating between large and small, with more tentacles in larger individuals than in smaller ones) ( Figs. 6 D, E), and the ramification complexity is of the third order branches. There are no atrial tentacles at the entrance of the exhalant siphon.

The branchial stigmata are straight ( Fig. 7 A) and between nine and 11 are present per mesh (i.e. between longitudinal vessels in the space between folds). There are six complete branchial folds ( Fig. 7 B), with around 20 vessels per fold. The branchial formula of two individuals is: R.E. 5 (14) 4 (19) 3 (20) 3 (22) 3 (22) 3 (22) 6 D.L. 7 (22) 4 (25) 3 (25) 3 (22) 3 (20) 3 (16) 8 E.L., and R.E. 11 (20) 3 (25) 4 (26) 4 (27) 4 (30) 4 (37) 7 D.L. 9 (29) 3 (31) 3 (30) 3 (28) 4 (22) 4 (19) 10 E.L. The large sponge-like dorsal tubercle is not arranged as a double spiral cone as in P. praeputialis and P. s to l on if er a, but instead is largely spherical with two distinct bulges ( Figs. 7 C, D). We found a less complex and convoluted dorsal tubercle in smaller individuals than in larger ones ( Figs. 7 C, D). The dorsal lamina, which is always present, is short and contains small languets ( Figs. 7 E, F).

The gonads are attached to the body wall and form two rows of lobes on the right side of the body ( Figs. 8 A, C). The left gonad is inside the gut loop and also forms two rows of lobes ( Figs. 8 B, C). The gonoduct on the right side of the body is short (extending 3 mm away from the first gonadic block) and is located just below the gonad, whereas the one on the left side of the body is long (opening approximately 10 mm away from the first gonadic block), and it crosses below the gut and opens next to the anus ( Fig. 8 D). The gut forms a sharply curved loop on the left side of the body, followed by a secondary loop that is not as sharply curved ( Figs. 8 B, C). The hepatic gland is large and branched ( Figs. 8 B, C) and contains 3 or 4 hepatic lobes. Endocarps are absent both around and on top of the gonads and the gut. The anal border has 6 to 10 irregular, rounded lobes ( Figs. 8 D, E).

Distribution. This species has been found in several localities in Victoria, on the southeast coast of Australia ( Dalby 1997a). It has also been found in Albany, Western Australia (this study). Unlike its South African and Australasian sister taxa, whose distributions extend from the subtidal to the lower intertidal, P. dalbyi has been found almost exclusively subtidally ( Dalby 1997a).

Etymology. The species is named Pyura dalbyi after Dr. J. E. Dalby Jr. who reported distributional, morphometric and ecological differences between this species and P. praeputialis .

Remarks. The yellow and sand-free tunic easily differentiates specimens of P. d a l b y i from the other species of the P. s t o l o n i f e r a species complex. Internally, the shape of the dorsal tubercle is one of the most conspicuous characteristics, as it is quite irregular when compared to the cone-like dorsal tubercle found in P. praeputialis and P. stolonifera . This is especially evident in smaller individuals of P. dalbyi . While the sponge-like shape of the dorsal tubercle in P. herdmani can be quite similar to that of P. d a l b y i, it lacks the two distinct bulges of the latter. The double row of gonadic blocks on the left side of the body inside the gut is a unique character of this species. All African species and P. praeputialis have just one row of gonadic blocks surrounded by the gut. The long siphonal spines of P. dalbyi are also unique, because in the other species the spines are shorter or less pointy. Pyura dalbyi lacks endocarps on top of the gonads and gut, which is uncommon in this group. None of the descriptions of Pyura species included in the extensive monograph of Australian ascidians by Kott (1985) corresponds to P. d al b yi. The presence of a picture of a large aggregate of P. dalbyi identified as P. stolonifera (see Plate VIIIa, page 420) indicates that both species were included under the same name.

Figures

FIGURE 5. Pyura dalbyi n. sp. A. Lateral view of a preserved specimen; B. Top view of another preserved specimen; C. Aggregated and separated live specimens photographed immediately upon collection. Scale bars: A. 10 mm; B. 10 mm.

FIGURE 6. Pyura dalbyi n. sp. A. Siphonal spines as seen from the outer surface; B. Detail of the shape of the siphonal spines; C. Siphonal spines showing the entire siphonal lining, from the external surface (top) to near the base of the siphon (bottom), where it is iridescent. D. and E. Siphonal tentacles of two different specimens. Scale bars: A. 500 µm; B. 100 µm; C. 500 µm; D. 2 mm; E. 1 mm.

FIGURE 7. Pyura dalbyi n. sp. A. Branchial sac between folds, showing straight stigmata; B. Branchial sac with six marked branchial folds; C. and D. Dorsal tubercle in a small and large individual, respectively; E. and F. Dorsal lamina with languets in a small and a large individual, respectively; Abbreviations: DL—dorsal lamina, DT—dorsal tubercle, AA—atrial (excurrent) aperture. Scale bars: A. 500 µm; B. 5 mm; C. 1 mm; D. 2 mm; E. 2 mm; F. 2 mm.

FIGURE 8. Pyura dalbyi n. sp. A. Two rows of lobed gonadic sacs without endocarps on the right of the body; B. Gut forming a sharply curved first loop enclosing the two rows of gonadic sacs on the left side of the body; C. Internal structure detailing the position of the gonoducts, hepatic gland, dorsal tubercle, gonad on the right side of the body and the gut and gonad on the left side; D. Rectal opening (view from the top) showing the irregular, rounded lobes. The gonoduct openings of the left gonad can be observed next to the rectal opening; E. Rectal opening (view from the side). Abbreviations: LG—left gonad, HG—hepatic gland, GO—gonoduct opening, AB—anal border. Scale bars: A. 5 mm; B. 10 mm; C. 10 mm; D. 2 mm; E. 2 mm.