Molgula pacifica (Huntsman, 1912)

Lambert, Gretchen, 2019, The Ascidiacea collected during the 2017 British Columbia Hakai MarineGEO BioBlitz, Zootaxa 4657 (3), pp. 401-436 : 425

Molgula pacifica (Huntsman, 1912)

Figure 12E, F

IHAK 64 BHAK 3248, UF 2566. Gold Stream sediment sample. One specimen, 8 mm in diameter.

This very small oval species is sometimes found, as in the current survey, as an interstitial member of gravel beds, though most specimens have been found on exposed low intertidal or subtidal rocks in regions of exposed coast, as at the type locality for the species ( Huntsman 1912a, b; Young et al. 1988). The tan tunic is covered by hairs that attach it to the substrate or surrounding gravel or sand grains. Because of its small size and tendency to be overgrown by epibionts it is very cryptic and may be more common than the few reported occurrences would suggest. The siphons are close together on the dorsal surface and are orange or bright red. The siphons may be fairly long when fully extended, with the four-lobed atrial siphon much longer than the oral siphon which may have either five or six lobes (six in Fig. 12E ) ( Huntsman 1912b; Young et al.1988). When the animal is disturbed both siphons strongly contract. The secondary intestinal loop is closely pressed against the primary loop, with the left side gonad positioned in the open area anterior to the secondary intestinal curve ( Fig. 12E ). The large oval ovotestis on each side is white because of the testes overlying the ovary. The oocytes are spawned in a sticky mass that attaches to the adult or very close by, fertilization is external, and the embryos develop directly into non-swimming juveniles, resulting in clumps of individuals ( Young et al. 1988). A detailed morphological description is given by Huntsman (1912b), summarized by Van Name (1945). Distribution: Alaska to British Columbia ( Huntsman 1912b; Van Name 1945; Young et al. 1988; Lamb & Hanby 2005).

Figures

FIGURE 12.A–D: Pyuridae; E, F: Molgulidae.A: Halocynthia aurantium 10 cm in length; B: Halocynthia igaboja; C: Boltenia villosa; D: Pyura haustor; E: Molgula pacifica whole animal left side, tunic removed; F: M. pacifica close-up of siphons. Scale bars: B, 5 mm; C, 5 mm; D, 5 mm; E, 1.6 mm.