Pyura haustor ( Stimpson, 1864 )

Sanamyan, K. E. & Sanamyan, N. P., 2006, Deep-water ascidians (Tunicata: Ascidiacea) from the northern and western Pacific, Journal of Natural History 40 (5 - 6), pp. 307-344 : 338-342

publication ID	https://doi.org/ 10.1080/00222930600628416
persistent identifier	https://treatment.plazi.org/id/1925951F-FFC9-E86C-708E-FC5FFECE99B8
treatment provided by	Carolina
scientific name	Pyura haustor ( Stimpson, 1864 )
status

Treatment

Pyura haustor ( Stimpson, 1864)

( Figures 16B View Figure 16 , 17 View Figure 17 )

Cynthia haustor Stimpson 1864, p 159 .

Pyura haustor: Van Name 1945, p 338 (synonymy). Sanamyan 1996, p 200; Lambert and Sanamyan, 2001, p 1777.

Material examined

St. 6098, 200 m, three specimens.

Description

Most of the small (less than 1 cm long) specimens are attached by the wide ventral surface to the larger specimens of Halocynthia igaboja and are often completely hidden by the test spines of that species. The siphons on the preserved specimens are short, sometimes almost sessile, but sometimes protruding suggesting that these variations in length may be affected by contraction and that they may be longer in living specimens. The test is hard, but lacks the ridges characteristic of larger specimens. The test around and inside the siphons is covered by relatively sparse, long narrow spines, 0.07–0.12 mm in length. Internally the specimens agree with the previous accounts. The gonads, immature in examined specimens, are long, consisting of numerous, sometimes more than 30, small, widely spaced polycarp sacs. Liver diverticula are in several separated bunches, they do not form one compact mass as was erroneously figured by Sanamyan (1996). Endocarps are not present.

Remarks

According to Van Name (1945) the endocarps in this species are poorly developed or may be absent. Larger specimens collected in the same region ( Sanamyan 1996) have endocarps on the free edges of the polycarps and a few small endocarps are on the gut loop. These specimens have larger (0.12–0.18 mm long) siphonal spines of similar shape. All these differences are obviously connected with the size of the specimens. The species is distributed from Alaska to California. The range extends to the eastern Aleutian Islands, where it appears to be common at depths of 75– 200 m. It was not recorded further to the west.

Asajirus indicus ( Oka, 1913)

( Figures 18 View Figure 18 , 19 View Figure 19 )

Hexacrobylus indicus Oka 1913, p 6 .

Asajirus indicus: Kott 1989, p 521 ; 1992, p 648 (synonymy); Sanamyan and Sanamyan 1999, p 1873.

Hexadactylus indicus: Monniot and Monniot 1990, p 271 . Material examined

St. 7206, 7880– 7420 m, one specimen; St. 6135, 2880– 2930 m, two specimens.

Description

The description is based on the specimen from the Philippine Trench (St. 7206). The specimen is 20 mm high (the body with the test removed is 15 mm), densely covered by thin short hairs which are longer posteriorly. In the intact specimen the oral lobes are clearly divided into two groups: two dorsal lobes, with free edges directed down and four ventral, with free edges directed up; this is not so evident on the body wall after the test is removed. Both siphons are long, covered by crowded circular and longitudinal muscles; the atrial siphon is slightly shorter than the oral (measured from the ganglion to the edge of the siphons). Longitudinal ventral muscles grouped into about seven thick crowded bands, sometimes intercrossing and branched, and terminating on one line in the middle of the body, below the posterior edge of the renal sac. The ganglion has two anterior pairs of nerves and a thick posterior nerve dividing into two. The pharynx is connected with the lateral pockets of the atrial cavity through the two pharyngeal chambers. The anterior chamber is thick walled and opens to the atrial cavity through a small slit-like stigmatum; the thin-walled posterior chamber opens through a large horseshoe-shaped opening. The large pyloric vesicle is connected with the middle of the stomach through a relatively thick duct, and another duct arises from the opposite side, divides into two and forms a net of anastomosing vessels over the intestine. Long and slightly curved ovaries containing only a few small oocytes open close together at the base of the atrial siphon, dorsal to the anus. The round, compact male gonad consists of numerous short follicles and has a short sperm duct that opens to the lateral horn of the atrial cavity opposite the two stigmata described above.

The two specimens from the Aleutian Islands (St. 6135, Figure 18B View Figure 18 ) are smaller, about 12 mm in height. They have a shorter atrial siphon, and six anterior nerves.

Remarks

The specimen from the Philippine Trench agrees closely with the existing accounts, especially with the description and figures made by Monniot and Monniot (1990). Kott (1989, 1992) described two ventral longitudinal muscle bands, one on each side of the midventral line, and in her figure ( Kott 1989, Figure 1 View Figure 1 ) these bands are much longer than in the present specimen, reaching the posterior end of the body, but in another specimen ( Kott 1992) they are described as short.

In the shape of the testis and the six anterior nerves the specimens from the Aleutian Islands resemble A. seeligeri ( Monniot and Monniot, 1990) , and the short atrial siphon is similar to that in A. millari ( Monniot and Monniot, 1990) . According to Monniot and Monniot (1990), A. seeligeri differs from A. indicus in shorter oral lobes, six oral nerves, a different shape of the gut, and a different position of the female papillae. In the figures, however, the shape of the gut is quite similar, and there seem to be more differences in the shape of the gut between the two figured specimens of A. indicus than between A. indicus and A. seeligeri (compare Monniot and Monniot 1990, Figure 21A and Figure 16A, D View Figure 16 ). We agree with Kott (1989, 1992), who synonymized A. seeligeri and A. millari , and also A. arcticus (Hartmeyer, 1923) , A. eunuchus (Monniot and Monniot, 1976) , A. antarcticus ( Monniot and Monniot, 1990) and A. longitestis ( Monniot and Monniot, 1990) with A. indicus . Many features used by these authors to distinguish these species, such as the shape of the dorsal oral lobes (in A. millari ), slight differences in the position of female papillae in relation to the intestine and the anus ( A. seeligeri , A. millari ), the shape of the intestine, the distance between the ventral longitudinal muscles (in A. eunuchus ), the number of the anterior nerves, etc., cannot justify specific separation. The differences in the shape of the ventral longitudinal muscles (grouped into bundles, regularly spaced, short or long) also seem to be related to their contraction and growth rather than species differences. For example, these muscles seem to be similar in A. antarcticus and A. arcticus (compare Monniot and Monniot 1990, Figure 9G View Figure 9 and Figure 11B View Figure 11 ) although described as grouped in the former and spaced in the latter. It is evident that in the larger specimens, and in contraction, ventral muscles of A. arcticus may look exactly as in A. antarcticus .

We support Kott (1989) in assigning Hexacrobylidae to the class Ascidiacea.

The present record in the Philippine Trench is the deepest record for the family Hexacrobylidae . The record near the Aleutian Island is the first record of the family in the north Pacific.