Apomatus geniculata ( Moore & Bush, 1904 )

Bastida-Zavala, J. Rolando, 2008, Serpulids (Annelida: Polychaeta) from the Eastern Pacific, including a brief mention of Hawaiian serpulids, Zootaxa 1722, pp. 1-61 : 12

Apomatus geniculata ( Moore & Bush, 1904)

( Figures 2A–H)

Protula geniculata Moore & Bush, 1904:168–169 , pl. 11, figs. 17–18; pl. 12, fig. 38. Type locality: Suruga Bay , Japan. Apomatus timsii Pixell, 1912: 787–788 , pl. 87, figs. 4a–f. Type locality: Departure Bay , Canada .

Apomatus geniculata .— Hartman, 1969: 745–746, figs. 1–4, southern California, USA.

Material examined. Five specimens: California ( USA), LACM-AHF N1912 (no more data, as A. timsii ) ; LACM-AHF N8815 (approx. 33ºN, 118º30’W, off San Clemente Island , collected in haul 1552, coarse sand, 91.5 m, without date) ; LACM-AHF s.n. (33º24’30”N, 118º21’33”W, 0.5 km from Long Point Light , Santa Catalina Island, sta. 2128, biological dredge, sand, shells, 77–123 m, June 25, 1952) ; LACM-AHF s.n. (approx. 34º54’N, 120º40’W, Santa Maria , on rocks, 770 m, no more data, as A. timsii ) ; LACM-AHF s.n. (33º22’35”N, 118º20’30”W, of Willow Cove , Santa Catalina Island, Velero, sta. 999, sand, brachiopods, 68– 81 m, 1939, as A. timsii ) .

Diagnosis. Tube white, smooth, lacks longitudinal ridges, peristomes or alveoli. Body pinkish. Branchial crown white, with 12–39 radioles on each lobe. Operculum on an unmodified radiole, membranous and translucent, with oval or spherical shape, sometimes collapsed ( Figs 2A–B). Thoracic membrane extends to last thoracic chaetiger. Collar and thoracic chaetigers with hooded (limbate) chaetae, sometimes eroded ( Figs 2C– E), and ” Apomatus ” chaetae in chaetigers 4–7 ( Figs 2F–G). Abdominal chaetae geniculate. Glandular region covering the last abdominal segments dorsally ( Fig. 2H).

Habitat. Depth: 68–770 m. Shelf, slope and canyon depths. On Lacqueus shells (brachiopods).

Distribution. North Pacific. Japan, Canada to California ( USA) ( Moore & Bush 1904; Pixell 1912; Hartman 1969).

Taxonomic remarks. Apomatus geniculata was described from Suruga Bay, Japan, as a nonoperculate Protula geniculata Moore and Bush, 1904 ; Moore (1908) expanded his description with one operculate specimen from the Halibut Bank, Strait of Georgia, Canada, thus, transferring Protula geniculata to Apomatus . Later, Pixell (1912) described A. timsii from Departure Bay, Strait of Georgia. Both species were recognized by Hartman (1969: 744), differing only by the shape of the abdominal chaetae, in A. geniculate are “abruptly bent, marginally smooth” and in A. timsii are “curved, marginally dentate”. Hartman (1969) recorded both species from California waters; however, the specimens (n=6) labelled as A. geniculata and A. timsii in LACM-AHF showed a gradual change in the shape of abdominal chaetae, with anterior chaetae clearly geniculate and becoming almost straight chaetae in posterior chaetigers. Further, the abdominal chaetae of all specimens have small teeth marginally (visible with 400x magnification) in contrast to the smooth edge present on these chaetae in A. geniculata by Hartman (1969: 745). Treadwell (1937) recorded a specimen of A. similis Marion and Bobretzky (1875) , from Arena Bank, Gulf of California, which exhibits two differences with A. geniculata : base of branchial crown short, concealed by collar, while in A. similis it is longer than the collar; and the number of radioles, 18 in A. geniculata and closer to 60 in A. similis . Both differences could be due to the age and size; Shepherd (1972) recorded A. geniculata from Bahia Falsa, La Paz, Baja California Sur, associated with oyster culture; however, it is probably a different species, as they occur in tropical and shallow waters while the specimens from California live in cold and deeper (68–770 m) waters.