Pione gibraltarensis Austin, Ott, Reiswig, Romagosa & G, 2014, n. sp.

Pione gibraltarensis n. sp. Fig. 5 A–H Etymology. The specific epithet is derived from the type locality, Gibraltar I. (Barkley Sound, BC) where KML 1018 was found. Material examined. Holotype: KML 1018, KML sta.149/76, Gibraltar I., Barkley Sd., BC, (48º 54.77′N, 125º 15.35′W), high tide pool 3 m above low tide level, Aug. 9, 1976, coll. W.C. Austin. Paratype: KML 1019, KML sta. 37/79, head of Pendrell Sd., BC, (50º 17.9′N, 124º 43.0′W), mid intertidal, May 2, 1979, coll. W.C. Austin. Description. Macroscopic features. KML 1018 excavating shell of living mussel (Mytilus californianus Conrad, 1837), in alpha form; papillae not contracted; oscular papilla a low truncated cone about 800 Μm in basal diameter; the orifice diameter and the wall height each about 1/3 of the basal diameter; ostia bearing papilla an elevated dome, the height almost equal to the basal diameter which ranged from 0.3–0.7 mm. Around the periphery of the dome 16–20 cellular strands reinforced by tylostyles extend from the base to the top of the dome. Oscular pores range in size from 0.8–1 mm diam; spaced at approximately 6 mm intervals; ostial pores 0.3–0.6 mm diam., spaced at approximately 1 mm intervals. Pores enter erosion pits directly, without canals, erosion pits initially oval about 0.8 x 1.6 mm by 3 mm deep; as increase in size interconnect to form channels; inter chamber pores typically 0.2 mm, some to 0.5 mm diam.; few openings into the interior of the mussel; these 0.2–0.6 mm diam. Colour in life greenish yellow. KML 1019 excavating empty Japanese oyster shells (Crassostrea gigas Thunberg, 1793), in alpha form. Papillae retracted; ostial pores 0.2–0.6 mm diam., oscular pores 0.8–1.2 mm diam., both types on inside and outside surface of oyster. These open directly into excavation chambers; these initially oval about 2.8 x 4 mm diam. but coalesce to become channels; interchamber pores 0.4–0.6 mm diam. Colour in life unknown. Microscopic features. Spicules. Spicule types include tylostyles, acanthoxea, and two classes of spirasters. Tylostyles form a fence around the papillae with the points extending beyond the tissue; about 2/3 with well rounded tyle (Fig. 5 A) but some, about 1/3, with tyle just back from the end giving a mucronate or subtylote appearance (Fig. 5 B, C); a few with the tyle well back from the head which is stylote (Fig. 5 D). Acanthoxeas abundant in the endosome; straight or bent and often with an annular swelling at the midpoint of the spicule (Fig. 5 E). The widest spicule is not necessarily the longest. Width measured midway along the acanthoxeas but adjacent to any central swelling. Spines moderately visible in spirasters, but some thin spirasters appear smooth under a light microscope. Spirasters strongly helical with the number of bends typically 5 or 6 (Fig. 5 F, G) but occasionally down to 1 or 2 and in one case with 7; no absolutely straight spirasters seen; a few spirasters appeared stretched out so that some of the turns were quite shallow; ends of spirasters rounded, not truncated. Spirasters of two types: type 1 (Fig. 5 F) thicker and spiny; type 2 (Fig. 5 G) thinner and smooth. In addition in one SEM preparation there was a third category with incipient spines (Fig. 5 H on left). Counts were made to assess the relative abundance of the spicule types. Under the light microscope of 200 spirasters counted 20 or 10% appeared smooth. Under SEM of 427 spirasters counted 10 (2%) smooth and 8 (2%) with incipient spines. Smooth spirasters the same length as spiny spirasters but typically thinner. KML 1018 KML 1019 Remarks. We assigned our specimens to the genus Pione Gray, 1867 based on the presence of acanthose oxeas coupled with tylostyles and microrhabdose spirasters (Rützler 2002). The taxonomic status of various species of Pione has been subject to differing interpretations on degree of conspecificity, (e.g., Topsent 1900, Rützler & Stone 1986, Rosell & Uriz 1997, 2002). Table 2 lists the described species of Pione with characterization of spicule size, form and surface. Two features that set our material (KML 1018, 1019) apart from other species of Pione are the maximum length of the spirasters (29 µm, 37 µm) and the maximum number of turns (6 & 7). Only three species have spirasters at least 20 um in length and with maxima of 5–6 turns. One of these, P. spirilla Old, 1941, differs from our specimens in having acanthoxea about 70% longer than in our specimens (170 µm vs. 93 & 110 µm). The other two have been identified as P. vastifica by Hartman (1958) and Old (1941). They differ from our material in the shorter lengths of their spirasters. However, they also differ from P. vastifica sensu strictu which has spirasters with 0–4 turns and up to 12 µm long (see p. 181, Fig. 12 in Rützler 2002) These taxa and P. margaritifera johannae (Topsent, 1932) are the only Pione spp. described as having smooth spirasters as in our material. In the BC specimens smooth spirasters occur in small numbers, are thinner than the axial cylinder of the spined spirasters, and some have incipient spines (Fig. 5 H on left) and likely would be seen as “smooth” under a light microscope. These features taken together do not preclude that the smooth spirasters may be growth stages. Conclusions. KML 1018 and KML 1019 do not exactly fit the descriptions for any species of Pione. However, the size and turns of the spirasters are only marginally greater than described by Old (1941) for material he identified as P. vastifica. This material should be re-evaluated. We cannot exclude the possibility that the spiraster greater length and number of turns are ecophenotypic responses to the high silica content of the water in BC as discussed under C. lobata. However, until demonstrated otherwise, we will assume that these differences are genetic and are sufficient to warrant errecting a new species. We propose the name P. gibraltarensis n. sp. Bathymetric range. High to mid intertidal. Geographic distribution. Barkley Sound and Pendrell Sound (BC, Canada). The Japanese oyster, Crassostrea gigas (Thunberg, 1793) has been repeatedly imported into Pendrell Sound as a source for seed oysters for commercial oyster farms in BC. P. gibraltarensis may well be an introduced species.

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