Pyura chilensis Molina, 1782

Turon, Xavier, Cañete, Juan I., Sellanes, Javier, Rocha, Rosana M. & López-Legentil, Susanna, 2016, Ascidian fauna (Tunicata, Ascidiacea) of subantarctic and temperate regions of Chile, Zootaxa 4093 (2), pp. 151-180 : 174-175

Pyura chilensis Molina, 1782

Figs 8 A; 14A,B

References and synonymy: Pyura chilensis Van Name (1945) p. 333.

Localities: 2N, 3N, 6N, 7N

The individuals have in general an ovoid shape, up to 5 cm in diameter. They form often aggregated clumps. The tunic is tough, its surface has wrinkles, protuberances and papillae. The colour is generally orange, but diverse tones of brown are also encountered, to almost black. The siphons are relatively close together, quadrangular and red-coloured. The internal tunic of the siphons has pointed spinules.

The mantle has a strong musculature and is of a vivid orange turning red in the siphonal area. The oral siphon has over 18 branched tentacles (with second and third order ramifications). The aperture of the neural gland is in the shape of an “U” with the horns rolled inwards, but it becomes extremely convoluted in large individuals. From the pre-pharyngeal area to the entrance of the oesophagus (which is relatively short as the siphons are close) a series of dorsal languets extends. The atrial siphon has a large bi-lobed velum. The branchial sac has 6 folds on each side, the ventral-most being the less developed. Except for these, there are 19 to 25 longitudinal vessels in each fold and 3–6 between folds. Up to 9 stigmata can be found in a single mesh in the central part of the branchial sac. In large individuals the posterior end of the longitudinal vessels on the folds protrudes freely near the oesophagus entrance (particularly those of the more ventral folds).

The digestive system forms an open primary loop and a slight secondary loop. There is a voluminous hepatic gland branching off from a common stem united to the stomach. Endocarps are present on the descending part of the intestine and the rectum, and they connect with the branches of the hepatic gland, thus the hepatic diverticula form a “bridge” over the primary loop. There is a well-developed gonad at each side. The left one enclosed in the primary loop. The right one strongly bent in the posterior part, reaching forward until the aperture of the atrial siphon. Each gonad is composed of alternating lobes at both sides of a central axis. The female portion occupies the proximal and basal part of these lobes and the male part lies distally. Endocarps appear over the gonad lobes. The ends of the two gonads and the anus lie close together posterior to the atrial siphon. Sometimes the distal parts of the two gonads coalesce and form a mass of tissue, to which the distal part of the rectum can also be fused. There are usually several apertures at the distal end of each gonad, and it is difficult to tell which corresponds to male or female ducts. One or several of the apertures point towards the atrial siphon, while the distal parts of other gonad ducts are bent 180º and point opposite it.

Remarks. surprisingly few descriptions exist for this species, which is very abundant on natural and artificial substrates in the Coquimbo area. The species is found in the low intertidal along the Chilean and Peruvian coast, and it sustains an important fishery in Chile (Davis 1995). Haye & Muñoz-Herrera (2013) highlighted the genetic diversity of this species in populations spanning 1800 Km of Chilean coastline, and the two sequences obtained here belong one each to their haplogroups 1 and 2.

Figures

FIGURE 8. Asterocarpa humilis. A, some specimens on Pyura chilensis (orange papillae belong to P. chilensis tunic); B, close up of the siphons (a colony of Diplosoma listerianum grows on the tunic); C, dissected individual; D, close up of the digestive loop, branchial sac removed; E, gonads of the right-hand side, branchial sac removed. The specimens in C – E have been stained. Scale bars: A, 2 cm, B, 1 cm, C, 1 cm, D, E, 1 cm.