Pyura stolonifera ( Heller, 1878 )

Kott, Patricia, 2006, Observations on non-didemnid ascidians from Australian waters (1), Journal of Natural History 40 (3 - 4), pp. 169-234 : 223-224

Pyura stolonifera ( Heller, 1878)

Cynthia stolonifera Heller 1878, p 10 .

Pyura stolonifera: Kott 1985 and synonymy; Monniot et al. 2001, p 113.

Pyura praeputialis: Castilla et al. 2002, p 1579 .

Distribution

Previously recorded (see Kott 1985): Western Australia (Shark Bay, Albany); South Australia (Gulf St Vincent); Tasmania (Spring Bay, Eaglehawk Neck, Kingstons, Bruny I., Roches Beach); Victoria (Ninety Mile Beach, Port Phillip Bay, Western Port, Wilson’s Promontory); New South Wales (Port Jackson, Arrawarra, Hastings Point); Queensland (Currumbin, Moreton Bay, Point Cartwright, Alexander Heads, Fraser I.); Chile; Peru; Ecuador; Africa (Port Nolloth, Cape Town to Algoa Bay, Luderitz Bay, Dakar, Morocco, Namibia). New record: South Australia (Smokey Bay—western Eyre Peninsula, 2–3 m, SAM E2887).

Description

Populations of this species on rocky shores on each of the continents are crowded, forming thick mats extending from low tide into deeper waters. Individuals adhere closely to one another and become tall, almost cylindrical pillars to about 20 cm high, although the body of the individual is in the top of the pillar, and its basal part (up to two-thirds of the total height) is solid gelatinous test with a hard, leathery surface, either adhering to neighbouring individuals or with weed epibionts.

In specimens on sandy substrata the basal pillar is not present, although crowded rootlike processes penetrate into the substrata. These substantial organisms are readily distinguished by the two adjacent four-lobed apertures on the upper surface surrounded by a high rounded marginal rim of test, the loss of a dorsal lamina, the double coil of the slit on the dorsal tubercle, the fringed lobes around the apertures and long, overlapping pointed siphonal spines.

Remarks

There has long been debate regarding the status of the African, Australian, and western South American proposed synonyms of this species. Monniot et al. (2001) state categorically (without any evidence) that the Chilean populations were introduced from Australia and are conspecific, while the South African ones are a different species. Most recently Castilla et al. (2002, 2004a, b) also propose that P. praeputialis Heller, 1878 has been recently introduced to South America from Australia; while the African populations are a different species. These authors also maintain that the populations recently introduced from Australia are confined to Antofagasta ( Chile). However, the Chilean populations appear to be more widespread: those from Antofagasta being apparently conspecific with specimens collected in Peru (Zorritos) in 1866–67 by F. H. Bradley. These specimens (in the Yale Peabody Museum registration number YPM 2934) became the types for Pyura bradleyi Van Name, 1931 . These specimens, collected 140 years ago, can hardly be said to be recent introductions. Further, Van Name (1945) also reported specimens from Ecuador. The wide geographic range of this species in South America does not support an hypothesis of recently introduced or alien species. In fact, it appears to be a long-established and probably indigenous component of the ascidian fauna of the Pacific coast of the South American continent. It does not support Monniot’s statement (fide Melville 1979) that Pyura chilensis was the only large ascidian in Chilean coastal waters in the late 18th century. Pyura bradleyi (< P. stolonifera ) was undoubtedly also present.

Attempts to establish that the South African and the Australian populations are separate species (Monniot et al. 2001) fail to take into account the great diversity in variations found in this species in both locations.

At this stage, there is no evidence that these populations of P. stolonifera on all three continents are not relics of a Gondwana component of the marine fauna on these three continents, although (as Kott 1985 suggested) it seems unlikely that there is any contemporary gene flow between them.

Pyura lignosa Michaelsen, 1908 from the western coast of Panama has apertures at opposite ends of the upper surface, distinctive gonads and a well-developed dorsal lamina with distinct languets. None of these characters are present in P. stolonifera and there appear not to be grounds for the suggestion (Monniot et al. 2001) that the species is closely related to the present one.