Coryne pusilla Gaertner 1774

Coryne pusilla Gaertner, 1774

Fig. 3, 4 b

Coryne pusilla Gaertner, 1774: 40, pl. 4, figs. 8a, A.

Type locality. UK: England, coast of Cornwall, with question (Allman 1872: 266).

Material examined. NS: Petit Passage, south of East Ferry, on mussels (Mytilus edulis) in Laminaria zone, 14.x.1970, without gonophores, coll. K.W. Petersen, SNM HYD- 000455.— NS: Petit Passage, south of East Ferry, on mussels (Mytilus edulis), intertidal, 14.x.1970, without gonophores, coll. K.W. Petersen, SNM HYD- 000457.— NS: Petit Passage, south of East Ferry, on mussels (Mytilus edulis), extreme low tide, 14.x.1970, without gonophores, coll. K.W. Petersen, SNM HYD- 000459.

Description. Hydroid colonies tending to grow in dense, straggly clumps, with some stolonal parts but mostly having erect stems, reaching about 1 cm high, arising from a creeping, branched and anastomosing stolonal system sometimes occurring as a dense network of overgrown tubes; stolonal tubes quite thick, perisarc wrinkled. Hydrocaulus monosiphonic, sparingly and irregularly branched, not forming an elongate main stem, often bent or twisted, relatively thick but of varied diameter, branches and pedicels similar in form. Perisarc quite thick basally, thinning out somewhat distally, golden- to straw-coloured, terminating at hydranth base, wrinkled to somewhat annulated throughout, although annulations mostly quite shallow and seldom regular. Hydranths clavate, about 0.7- 1.3 mm long, 0.3–0.4 mm wide; hypostome large, dome-shaped. Tentacles all capitate, solid, about 18-23 in number, occurring over all but extreme basal part of hydranth, scattered except for a whorl of 4-6 around hypostome, with proximalmost ones the shortest; acrosphere nearly round except for slightly flattened proximal side, heavily armed throughout with nematocysts. Proximal filiform tentacles absent.

Gonophores not seen.

Cnidome (Fig. 3)

Hydranths—

small stenoteles (n = 10): 13.0–14.0 µm long × 8.2–8.9 µm wide (undischarged)

large stenoteles (n = 10): 23.4–24.8 µm long × 15.2–16.9 µm wide (undischarged)

Remarks. The identity of the hydroid described as Coryne pusilla by Gaertner (1774) is somewhat uncertain. Allman (1872: 266) noted that Gaertner’s illustration of it was rudimentary, and that his account does not accord fully with any known species. He nevertheless concluded that the hydroid later known as C. pusilla was likely identical with that of Gaertner, whose species is thought to have been collected from the coast of Cornwall, UK. According to Allman, that hydroid agrees with the original description as well as any, and it is also locally abundant and widely distributed around the British Isles. The contemporary concept of the species (e.g., Schuchert 2001b; 2012), type species of Coryne Gaertner, 1774 by monotypy, coincides with that of Allman.

Coryne pusilla was regarded by Allman (1872) as a species of the intertidal zone, commonly found on fucoid algae and often in association with Clava multicornis (Forsskål, 1775). It was found near low water in the Fundy region by K.W. Petersen on blue mussels in Petit Passage, NS (SNM HYD-000455, SNM HYD-000457, SNM HYD-000459), and those specimens are described here. That location is influenced by unusually strong tidal water currents (see Remarks below on Corydendrium dispar Kramp, 1935).

Molecular studies by Schuchert (2010) have confirmed the hypothesis of Broch (1916) and others that Coryne vermicularis Hincks, 1866 is conspecific with C. pusilla. The species of Hincks had been reported from waters of northern Canada (Port Burwell, Ungava Bay) by Fraser (1931). Other records of C. pusilla from northern Canada, by Calder (1972), were thought by Schuchert (2001b) to have been based on the cold-water species C. hincksii Bonnevie, 1898. That species has much less annulated perisarc, however, and the identity of the hydroids described by both Fraser and Calder from subarctic Canada remains uncertain. Reports of C. pusilla in waters of Atlantic Canada include those of Whiteaves (1873, 1875), Vervoort (1972a), and Brunel et al. (1998) from the Gulf of St. Lawrence and the Strait of Belle Isle. In the northeastern North Atlantic, it is known from Norway and Iceland to Brittany, France (Schuchert 2001b, 2012).

When fertile, C. pusilla can be distinguished from C. hincksii in having gonophores that arise in the upper axils of the tentacles rather than being independent of them (Schuchert 2001a, b). Moreover, gonophores of C. pusilla lack a circular canal. In terms of nematocyst sizes, the stenoteles of C. hincksii (16–18 x 11 –12 um and 28–29 x 18 –20 um), as measured by Schuchert (2001b), are considerably larger than those of C. pusilla observed here.

Another boreal species in the North Atlantic that is similar to C. pusilla, and one that also extends into the lower intertidal zone, is C. eximia Allman, 1859a. It differs in having much smoother perisarc and a free medusa stage rather than fixed sporosacs. Its nematocysts, comprising stenoteles measuring 12–14 x 8.5–10 um and 10– 10.5 x 6–7 um (Schuchert 2001b), are also much smaller than those of C. pusilla from the Bay of Fundy.

Coryne pusilla has been reported from many localities worldwide, but evidence now exists that a species complex exists under that name. Using partial 16S sequences, Schuchert (2005b) demonstrated that populations assigned to the species from Japan, Korea, and the Mediterranean Sea were widely dispersed phylogenetically from that of the northeastern North Atlantic. Of these populations, only the latter is likely to be identical with the species of Gaertner (1774), and the distribution of C. pusilla is certain to be much more restricted than records imply.

Recorded distribution. Bay of Fundy: recorded for the first time.

Eastern North America: Frozen Strait, Nunavut (Calder 1970), to Gulf of St. Lawrence and St. Lawrence River, mid-estuary (Brunel et al. 1998), southwards to the Bay of Fundy (this study).

Worldwide: widely reported, from the North Atlantic, North Pacific, Indian Ocean, and New Zealand (Schuchert 2001a). As noted above, however, a species complex likely exists under the name Coryne pusilla (Schuchert 2005b: 198, 2010: 513).