Polymastia pacifica Lambe 1893

Polymastia pacifica Lambe, 1893b

Fig. 9 A–G

Non Polymastia pacifica Koltun, 1966, a junior synonym.

Material examined. Holotype: CMN 1900-2885, near Comox, Strait of Georgia, BC, (approx. 49º 42′N, 124º 50′W), 73 m depth, Jun. 24, 1885, coll. G. M. Dawson.

Other material: KML 1026, KML sta. 19/76, Princess Royal Reach, Jervis Inlet, BC, (50º 01.0′N, 123º 56.5′W) 30, 70 m depth, Mar. 15, 1976, coll. W.C. Austin; KML 1027, sta. 25/76, entrance to Prince of Wales Reach, Jervis Inlet, BC, (49º 47.6′N, 123º 56.8′W), Mar. 16, 1976; coll. W.C. Austin; KML 1028, KML sta. 27/76, Cullodon Point, Jervis Inlet, BC, (49º 47.5′N, 124º 04.6′W), no depth, Mar. 17, 1976, coll. W.C. Austin; KML 1029, KML sta. 137/76, S. of Swale Rock, Barkley Sd., BC, (48º 55.0′N, 125º 13.1′W), 45, 52 m, depth, Aug. 3, 1976, coll. W.C. Austin; KML 1337, NM 291, Croker I., Indian Arm, BC, (49° 25.76′N, 121° 51.89′W), 15 m depth, Sept. 20, 2012, coll. N. McDaniel; KML 1339, NM 292, Croker I., Indian Arm, BC, (49° 25.76′N, 121° 51.89′W), 15 m depth, Sept. 20, 2012, coll. N. McDaniel; KML 1340, NM 293, Croker I., Indian Arm, BC, (49° 25.76′N, 121° 51.89′W), 15 m depth, Sept. 20, 2012, coll. N. McDaniel.

Field images, KML 1030, Pulalli Point, South Fingers Wall, Dabob Bay, Hood Canal, Washington, (47º 44.0′N, 122º 51.2′W), 20–30 m depth, Apr. 4, 2009, coll. & photo Janna Nichols, Greg Jensen; KML 1337, NM 291, Croker I., Indian Arm, BC, (49° 25.76′N, 121° 51.89′W), 15 m depth, Sept. 20, 2012, photo N. McDaniel.

Description. Macroscopic features. (Fig. 9 A). Sponge forming encrustations 7–30 mm long by 7–12 mm wide by 2–10 mm thick. Fistulae largely cylindrical but some slightly flattened, 2–7 (occasionally to 15) mm high and 1.5–2 mm in diameter. Number of fistulae from 1 per smallest sponge to 18 in largest sponge observed. Oscula at the summit of some fistulae, 0.5–1 mm diameter; other fistulae appearing blind. Surface hispid from projecting spicules; surfaces of fistulae basally microhispid and apically smooth. Consistency firm and only slightly compressible. Live colour: fistulae beige to white, basal part brown due to entrapped silt.

Microscopic features, (Fig. 9 B, 9C). Ectosome composed of cortical layer 0.5 mm thick, nearly cartilaginous. Palisade of tylostyles of all sizes embedded in cortex, apices outward; short tylostyles concentrated in ectosome. Long thin subtylostyles II with apices projecting outward up to 1 mm from main sponge body, originating in choanosome. Fistulae supported by tracts of short tylostyles. Tracts forming distinct canals in fistulae, terminating in osculum at apex. Tylostyles apically arranged more or less in parallel with long axis of fistulae with majority of apices pointing up. Tylostyles penetrating surface of fistulae basally up to 300 µm and main body up to 700 µm. Choanosome with long styles to subtylostyles I in radiating tracts 100–200 µm thick with intermediate and small tylostyles in random distribution throughout. Disposition of long, thin, surface-echinating subtylostyles at right angle to surface. No apparent basal specialization of choanosomal skeleton.

Spicules. Spicule complement including very long, thin styles to subtylostyles I echinating the main sponge body (Fig. 9 D), long, thin subtylostyles II (Fig. 9 E–F), long thin tylostyles I (Fig. 9 G) and shorter fusiform, occasionally bent, tylostyles II (Fig. 9 I,) with well developed heads; both tylostyles occasionally polytylote. Tylostyles II occasionally with subterminal heads (Fig. 9 J). Spicule measurements from five specimens are listed in Table 7.

Remarks. Lambe (1893a) described four spicule types, viz. two types of subtylostyles (739– 1205 x 13–19 Μm, forming radial multispicular tracts, and 1000–3000 Μm, echinating the main body surface), and two types of tylostyles (191–630 x 19 Μm in the inner cortex, and 108 x 6 Μm, forming a palisade in the ectosome and scattered in the choanosome). The smaller tylostyles II that we measured fit Lambe’s ectosomal tylostyles and are located in this position in our specimens. The long subtylostyles (to 2500 Μm in our specimens) echinate the body and are not found in the fistulae.

Polymastia pacifica is here distinguished from P. pachymastia based on its distribution (ranging from shallow [15 m] to deep [at least 100 m] for P. pacifica vs. mostly shallow to intertidal for P. pachymastia) and spicule compliment (pachymastia: 2 styles to subtylostyles, 3 tylostyles; pacifica: 2 subtylostyles, 2 tylostyles). Polymastia pacifica has invariably small (0.5–3 mm basal diameter) fistulae, whereas P. pachymastia has many large (1–2 cm basal diameter) fistulae. Very small individuals of Polymastia pacifica typically have only one or two fistulae. The fistulae of P. pachymastia are conical (L/W <2.2) while in P. pacifica they are cylindrical (L/W>3). Polymastia pacifica fistulae are similar to small P. toporoki but, unlike P. toporoki, fistulae do not grow close together in larger specimens; P. pacifica has four types of spicules (two tylostyles and two subtylostyles to styles), whereas P. toporoki has only two types of tylostyles.

Polymastia pacifica reported for the Aleutians (Stone et al. 2011) is bright orange in life and several cm thick which is uncharacteristic of any specimens we have examined which are white with the main body usually discoloured brown from sediment and a main body a few mm thick.

Conclusions. There are no other Polymastia species recorded from the north Pacific which have small, cylindrical fistulae. We conclude that Polymastia pacifica is a distinct species. The synonymy of Polymastia pacifica Koltun 1966 not Lambe 1893b needs to be addressed.

Bathymetric range. From 15 to at least 180 m depth.

Geographic distribution. Southern British Columbia in Jervis Inlet, Indian Arm, Barkley Sd., Comox and in Hood Canal (Washington). Records from southern California (Green & Bakus 1994) are based on the supposition that presence of small tylostyles in the cortex palisade excludes P. pachymastia, and their material probably represents P. pacifica. Records from the Aleutian Islands, Alaska may not be this species (see previous comment).

Ecology. This species occurred on dead hexactinosan sponges in Jervis Inlet in areas where currents are weak. It also occurred on rocks at Pulali Point, Hood Canal, which has only weak currents and in similar conditions in Indian Arm and Sechelt Inlet, BC.