Styela truncata Ritter, 1901

Lambert, Gretchen, 2019, The Ascidiacea collected during the 2017 British Columbia Hakai MarineGEO BioBlitz, Zootaxa 4657 (3), pp. 401-436 : 423-424

Styela truncata Ritter, 1901

Figure 11F

IHAK 31 BHAK 1695, 1696 UF 2519, 2520. Triquet Island Macro site, Scuba, 8 m. Very small; on Pugettia richii . With D. listerianum .

IHAK 37 BHAK 1706 UF 2523. Crazy Town surge channel, Scuba, 5 m. Covered with P. annectens ; small but with many brooded uncleaved embryos; on kelp holdfast, wave–exposed .

IHAK 44 BHAK 1716 UF 2529. Rattenbury Pinnacle, Scuba, 21 m. No larvae .

ZHAK 35 BHAK 3254 UF 2572. Sasquatch Commode tidepool. Small, 7 mm long, but with large brood of embryos.

This small species may be difficult to distinguish from S. gibbsii without dissection, though the body is almost always somewhat twisted as in Fig. 11F and never attains a length of over 3–4 cm. Often (though not always) the anterior end is more slender, with the posterior half more bulbous. There are several anatomical differences from S. gibbsii . There is always only one longitudinal vessel between each of the four pharyngeal folds (vs. four to six for S. gibbsii ). There are two elongate gonads per side as in S. gibbsii , but in S. truncata the anterior tips of the ovaries curve posteriorly ( Abbott & Newberry 1980), resulting in internal oocyte release and fertilization. It is a brooder and brooded embryos can almost always be found in the atrial cavity during the summer breeding season. A detailed morphological description is given by Ritter (1901), Van Name (1945) and Lambert & Sanamyan (2001). Distribution: Alaska to southern California ( Ritter 1901; Huntsman 1912b; Van Name 1945; Lambert & Sanamyan 2001).

Figures

FIGURE 11. Styelidae. A: Cnemidocarpa finmarkiensis about 2 cm in width; B: Metandrocarpa dura; C: M. taylori; D: Styela gibbsii 1.7 cm in length; E: S. montereyensis, longest one 8 cm; F: S. truncata 2 cm in length. Scale bars: B, 1 mm; C, 2.5 mm. A and F photos by G. Paulay.