Acanthogorgia gracillima typica

Biology. On this particular specimen, there were at least two scale worms wrapped around the base of polyps in two separate areas within the colony.

Description. Colony (Figures 8, 9 A) richly branched, not entirely in one plane, forming bushy fan or tree no more than 10 cm at widest point. Colony appeared fragile and delicate, but actually a tough, spiky bush / fan, branches reminiscent of those in a bottlebrush (Figure 9 B); not greatly flexible. Colony height (dictated by main, central, generally straight stem), base to tip, 15 - 16 cm; 7.0 cm broad; holdfast remnant present. If any regularity to branching pattern, slightly dichotomous to pinnate, usually in one plane; all lateral branches, of differing lengths, project at nearly right angles, extending / curving quickly upward, even those with more lateral placement. Branch diameter averages 2.0 - 3.0 mm. Polyps distributed over entire surface (not so much on lower portion of main stem, just above base), nearly in rings around branches, closely placed but not crowded (Figure 10); sometimes two with bases contiguous, generally separated by 1.0 mm, perhaps more; terminal twigs rounded, almost clavate in appearance; numerous polyps at apex, completely covered with straight and curved spindle-shaped sclerites. Polyps not retractile; very conspicuous, decidedly slender, columnar in shape, height between ~ 4.0 - 7.0 mm (most average 5.0 - 6.0 mm tall); diameter generally 1.0 mm for most of polyp length, narrowing slightly, then increasing to ~ 1.5 mm wide at the crown. Easily recognized by crown of sharp spines encircling top of polyp. Coenenchyme very thin and translucent, with axis color showing through. Color of freshly collected specimen bright lemon yellow (M Love, pers. comm.; Figure 8); on being placed in alcohol quickly turned, generally, light olive-green towards base, becoming slightly darker grey-green at uppermost branch tips. (While species in family are described as having a predominantly black, purely horny axis, color of axis showing through extremely thin coenenchyme appeared to account for overall olive-green color. Having now sat in 70 % ETOH for some time, the colony has turned more yellowish brown.) Sclerites (Figures 11, 12 A, B) mainly spindle-shaped; straight or curved, showing arrangement of eight double rows, forming longitudinally-placed chevrons (obliquely angled double-rows) characteristic of genus. A very few oddly branched; some, more a tripod shape. Sclerites appear mostly tuberculate, with distinct boomerang bend (Figure 12 A), easily removed from surface of colony. The longest sclerites, with distinct bend roughly a third of the way along their length, range from 1.0 - 2.0 mm in length (average 1.6 mm L x 0.17 mm W); one third of surface of sclerite bears tubercles, while other two-thirds is generally smooth; this smooth section, thin, rounded, somewhat beveled, is the distal, prominent spike that projects from the thorny basal portion embedded in the mesoglea of the body wall, in nearly longitudinal direction; lower, embedded portion, ~ 0.5 mm long, appears to cross over into the neighboring angled rows, these basal portions not much different one from another. These sclerites form the crown of thorns seen around top of polyp. Two very long spines project upwards to form the points of the crown at distal end of each of the eight double-rows. Smooth portion of these sclerites sit with approximately 1.0 mm of their length free of polyp. Numerous, slightly smaller, flatter sclerites have bend more centrally located, their entire surface covered with tubercles (average 1.0 mm L x ~ 0.08 mm W). These primarily cover outside surface of polyp (Figure 11), illustrating chevron pattern (eight longitudinal double rows) in placement. Sclerites of coenenchyme similar to those seen on polyps' surface (~ 0.8 mm long), perhaps slightly thicker in width and slightly more fully covered with tubercles; tentacular sclerites smaller still, bent, flattened (up to ~ 0.18 mm long), completely covered with tubercles; more prominent, dense, on dorsal side of tentacles. If present, a few smaller (0.1 mm long) radiate or cross-shaped sclerites may be seen. In the coenenchyme covering the base, exclusively, are 0.25 mm long, bent, strongly spined spindles. All sclerites completely colorless, reminiscent of thin, bent shards of glass.

Distribution. For genus in general, " species ... inhabit moderate to considerable depths; various species of Acanthogorgia occur in all seas, some thriving in very cold waters " (Bayer, penciled personal annotations in Kuekenthal 1924). Examinations of the literature revealed numerous species in the Indo-Pacific region. Recent MBARI on-line postings indicated this genus is found in northern California waters, often at great depth. Milton Love (description based on specimen he collected) indicated (pers. comm.) that the color of this gorgonian is very vibrant, thus easily seen; it is quite abundant in certain areas, such as the Footprint, a feature outside the Anacapa / Santa Cruz Island Passage. Thus, for this species, range seems to extend around the Pacific Ocean from Japan (Kuekenthal's specimen) to eastern Pacific waters of California; further study will be required to determine whether, and how far, it extends north and south of California.

Etymology. For designation gracillima, the Latin gracili- means slender; this may reference the conspicuous, very slender polyps and very slender points in the crown of this species. Kuekenthal (1909) gave no explanation for the derivation of the species name.

Material examined. 1 lot (see Appendix 1: List of material examined).