Distaplia occidentalis Bancroft, 1899

Lambert, Gretchen, 2019, The Ascidiacea collected during the 2017 British Columbia Hakai MarineGEO BioBlitz, Zootaxa 4657 (3), pp. 401-436 : 411

Distaplia occidentalis Bancroft, 1899 Type A: Mushroom-shaped colonies

Figure 6A

IHAK 12 BHAK 0613 UF 2470. Rocky intertidal across small bay from Hakai dock. One very small colony under rock.

IHAK 18 BHAK 0644, 0645 UF 2494, 2495. Several, purple; under lab dock.

IHAK 31 Triquet Island Macro site, Scuba, 8 m. On Scyra acutifrons .

IHAK 31 BHAK 1699 on red alga O puntiella californica (Farlow) Kylin, 192 5.

IHAK 39 NE Rattenbury Island , Scuba, 12 m. Several small, purple .

IHAK 42 BHAK 1717 UF 2530. Starfish Rocky Reef Site, Scuba, 18 m. Different color morph purple–lavender; mushroom shaped but stalk very short .

IHAK 60 Rattenbury Pinnacle, Scuba, 17–20 m depth .

XHAK 4 Spider Island ARMS 9 m. One small colony on cross piece.

ZHAK 35 Fifth Beach, Sasquatch Commode tidepool.

Distaplia occidentalis was collected in two growth forms. In mushroom shaped colonies, there are multiple capitate heads of various sizes in each colony. Colonies typically have a wide, short funnel-shaped stalk which is sometimes not initially visible until the colonies are carefully removed from the substrate. The heads are usually purple or lavender, sometimes tan, with the underside and stalk uncolored but opaque. The zooids are in two parts, thorax and abdomen, and confined to the capitate head. Thorax with four rows of elongate stigmata each crossed by a parastigmatic vessel; usually 12–16 stigmata per row on each side. In each zooid the oral siphon is six-lobed; the large atrial opening is covered by a wide, shield-like atrial languet, shallowly trifid if fully relaxed, with muscle bands running the length of the languet as well as longitudinal muscle bands extending from the thorax to the abdomen. Thoracic muscles dorso-ventral, doubled at dorsal end. Zooids are arranged in roughly circular systems. The stomach always has many shallow irregular longitudinal folds, usually broken up. A complete description of the zooids and colonies is given by Ritter & Forsyth (1917), much of it quoted in Van Name (1945).

Distribution: Alaska to southern California ( Ritter & Forsyth 1917; Van Name 1945; Abbott & Newberry 1980; O’Clair & O’Clair 1998; Lamb & Hanby 2005).

Figures

FIGURE 6. Aplousobranchia, Holozoidae, various color morphs of Distaplia occidentalis. A: small mushroom-shaped colony. B–D: flat colonies. E: flat encrusting colony with protruding capitate heads. F: brood sac removed from tunic. Arrow indicates location of attachment to zooid. G: tadpole. Scale bars: A, 1 cm; B, 1 cm; C, 1.25 mm; D, 1.7 cm; E, 1 cm; F, 0.85 mm; G, 0.4 mm. D and E photos by G. Paulay.