Aplidium, Savigny, 1816

Lambert, Gretchen, 2019, The Ascidiacea collected during the 2017 British Columbia Hakai MarineGEO BioBlitz, Zootaxa 4657 (3), pp. 401-436 : 404-405

Aplidium sp.

Figure 2 F–H

IHAK 10 BHAK 0625 UF 2476. Fifth Beach Cove, boulders with Phyllospadix WJ Hooker, 1838 and Fucus Linnaeus, 1853 . On Metandrocarpa taylori Huntsman, 1912 .

IHAK 53 BHAK 1729 UF 2540. Choked Pass, outer sandspit 5–12 m, Scuba. On tubes of Spiochaetopterus M. Sars, 1856 .

RHAK 6 Seventh Beach, North wall, low intertidal tide pool.

This species has for many decades been considered a variant of Aplidium californicum , with 8–12 stigmatal rows and also much variation in the number of stomach ridges ( Ritter & Forsyth 1917; Van Name 1945; Abbott & Newberry 1980). Aplidium species can be very difficult to distinguish morphologically; Van Name summarized the problem in his description of A. californicum : “So wide is this apparent range [of variation] that we may question whether more than one species is not being confused, but, if so, I would be at a loss to name characters by which they might be distinguished.”

The species is distinguished by having a clear tunic with the tiny bright orange zooids usually only about 4 mm or less in length, and visible through the tunic. Unlike A. californicum , the colonies always consist of irregular lobes of various sizes, tapering to a narrow base. The zooid thorax has only eight or at most nine rows of stigmata. The longitudinal stomach folds are always undivided and vary in number between colonies from about 9–14. This com- bination of characters does not match any known Aplidium species. A full description will be presented in another publication. The current known distribution is British Columbia to southern California.

Figures

FIGURE 2. Aplousobranchia, Polyclinidae. A–D, Aplidium kottae. A, B: part of colony; C: siphons of a single zooid; D: tad- pole. E: Aplidium californicum. F–H: Aplidium sp. F, G: part of colony; H: zooid. Scale bars: A, 1.4 cm; B, 0.7 cm; C, 34 µm; D, 143 µm; E, 0.7 cm; F, 1 cm; G, 4 mm; H, 1 mm.