Scolanthus scamiti Daly & Ljubenkov, 2008, sp. nov.

Scolanthus scamiti sp. nov.

Figs. 1, 10; Table 3

Diagnosis. With 14–16 tentacles and large nemathybomes scattered on column; nemathybomes more numerous proximally than distally. Nemathybome nematocysts shorter than 55 μm. Length of whole animal in contraction typically exceeds 15 mm, diameter 1.5–2.5 mm.

Material examined. Holotype: CAS 175229, San Diego, California, Bight 0 3 Sta. 4276, 33°58.917’N 118°27.36’W, 3­Sep­1998, 3 m. Paratypes: CAS 175230, collected with holotype (4 specimens); CAS 175231, San Diego, California, 32°47.157’N 117°15.0’W, 25­Jul­2003, 2.8 m (4 specimens); CAS 175232, San Diego South Bay, California, August 1994, intertidal.

External anatomy. Tentacles filiform to blunt, 14–16, inner tentacles slightly shorter than outer tentacles; in specimens with fewer than 16 tentacles, inner cycle incomplete. Adoral base of each tentacle marked with two red ovals. Column elongate but stout, wider proximally than distally (Fig. 10 A). Capitulum translucent, bearing irregular red and opaque white spots; white spots scattered proximally, converge into lines distally. Scapus with small, scattered nemathybomes not readily visible to unaided eye. Periderm thin, typically light brown to orange; larger grained particles may overlay periderm. Aboral end rounded but not bulbous, with periderm, nemathybomes, and rugae (Figs. 10 A, D).

Internal anatomy and histology. Parietal and retractor muscles strong (Figs. 10 B, C). Retractor muscle with large pennon (Fig. 10 B). Branches of retractor muscle variable in height and degree of ramification: shorter and taller branches interspersed, closely spaced, those farther from body wall typically simple, shorter. Parietal muscle ovoid to trianguloid; central lamella thicker than lateral branches (Fig. 10 C). Branches of parietal muscle ramify close to central lamella rather than at tips. No examined specimens contained gametes.

Nemathybomes large, sunken into mesoglea, protruding into epidermis (Fig. 10 E), scattered such that multiple, irregularly arranged nemathybomes lie between macrocnemes (Fig. 10 E).

Cnidom. Spirocysts, basitrichs, microbasic p ­mastigophores (Figure 11 F– O; see Table 3 for size and distribution).

Etymology. Named for the Southern California Association of Marine Invertebrate Taxonomists (SCAMIT), a professional organization dedicated to the description and identification of the marine fauna of California.

Distribution and habitat. Known from shallow bays in Southern California Bight, in silty sand with coarse shell and gravel (JL, pers. obs.). Co­occurs with E. californica.

Similar species. In general appearance and the length of nematocysts in the nemathybome, S. scamiti most closely resembles S. armatus (Carlgren, 1931) (see England 1987). The two differ in aspects of the cnidom: the nemathybome basitrichs are thinner in S. scamiti than in S. armatus (3.5–5.8 μm: England 1987), and the tentacle basitrichs are shorter in S. scamiti than in S. armatus (42.5–87.3 μm: England 1987), and S. scamiti has microbasic p ­mastigophores in the actinopharynx.

Remarks. Based on the morphology of fired capsules (Figs. 10 L–N, P), the nematocysts of the nemathybomes are basitrichs, rather than pterotrichs or microbasic t ­mastigophores (see England 1987). The tubule appears to be of uniform diameter, and has long spines proximally. Apical flaps are visible on some discharged capsules (Fig. 10 M). All nematocysts of the nemathybome are of a single size class and have similar morphology (Fig. 10 P).