Polycarpa mytiligera Savigny, 1816

Monniot, Françoise, 2010, Some new data on tropical western Pacific Ascidians, Zootaxa 2561 (1), pp. 1-29 : 22-23

Polycarpa mytiligera Savigny, 1816

( Figure 20C , 23 )

Cynthia mytiligera Savigny, 1816: 98 pl. VIII-2.

Polycarpa mytiligera: Monniot C. 1973: 55 Fig. 3A. Monniot F. & Monniot C. 1999: 29 Fig. 17 , pl. 3F. Monniot C.et al: 2001: 95

Material. Coll. Coral Reef research Foundation, Palau, Southwest Isl. , Helen Reef (Hotsarihi), 02°48.88’N – 131°46.75’E, 10m, 22/IX/2008, 0CDN 9871-0 ( MNHN S1 POL. B 554 )

The single specimen 5.5cm long is covered with epibionts. The lining of the siphons was white with a thin orange line at the rim ( Fig. 20C ). In formalin the body wall is brown with dark round cells and clear vesicles. There is a large oral velum. About 20 tentacles are intercalated with smaller ones. A thick dorsal tubercle with multiple openings is located in a wide V of the peripharyngeal band. The dorsal lamina is low and long. The branchial sac ( Fig. 23B ) has 4 low folds on each side. The formula at mid-length on the right side is:

E-4- 11 -6- 15 -6- 16 -5- 15 -4 DL

There are a few parastigmatic vessels. The digestive loop occupies a small part of the left body side ( Fig. 23A ); it is only linked to the body wall by bridles. The secondary loop is wide, ending in a smooth-edged anus. A wide pyloric canal crosses the primary intestinal loop. Three foliated endocarps occupy the gut loop. Very numerous gonads are included into the body wall ( Fig. 23A ), they are only indicated on the surface by the gonoducts. Each round polycarp is composed of a central ovary lying on two lines of testis vesicles. There are no endocarps on the body wall. The atrial siphon has a large velum and filiform tentacles at the base in a trapeze shape area.

Remarks. The taxonomic status of several Polycarpa species is not satisfactory, and a reminder of previous positions is given here. The type specimen of P. mytiligera could not be found but numerous samples from Eilat are described by Monniot C. (1973): they have numerous gonads and either a plain or dented anus. The anatomy of the species described here under the name P. mytiligera is also very similar to Polycarpa pigmentata (Herdman, 1906) which only differs in having a lobed edge of the anus instead of plain, and fewer polycarps. Kott (1985) for P. pigmentata from Australia noted a lobed anus but did not enumerate the number of gonads. Monniot C. (1987) assigned to P. pigmentata New Caledonian specimens with a smooth edged anus and few gonads and in the same paper named P. mytiligera ? ascidians which probably belong to more than one species, and differ by many more gonads and fewer branchial vessels. Monniot F. & Monniot C. (1999) placed in P. mytiligera specimens from Tanzania and Mozambique, having numerous gonads and a scalloped anus, taking into account the gonad number. Monniot C. et al (2001) described as P. mytiligera specimens from South Africa with a “slightly dented” anus and about 100 polycarps. Monniot F. & Monniot C. (1996) named New Guinea specimens: P. pigmentata havin g a lobed anus and only 10 gonads on each side.

In conclusion the different number of gonads remains the single argument to separate both species.

Figures

FIGURE 17. Eudistoma vulgare: digestive loop, scale bar: 0.5mm.

FIGURE 20. A: Amphicarpa duploplicata. B: Polycarpa argentata. C: Polycarpa mytiligera. D: Microcosmus exasperatus.

FIGURE 23. Polycarpa mytiligera: A: body, B: branchial sac, sacle bar=1cm.