Amphicorina ezoensis, Yoshihara, Taiki, Hiruta, Shimpei F., Katoh, Toru & Kajihara, Hiroshi, 2012

Yoshihara, Taiki, Hiruta, Shimpei F., Katoh, Toru & Kajihara, Hiroshi, 2012, Three species of Amphicorina (Annelida, Sabellida, Sabellidae) from Japan, with descriptions of two new species, ZooKeys 187, pp. 45-62 : 49-50

Amphicorina ezoensis sp. n. Figs 34

Material examined.

Holotype: ZIHU 4255, fixed in 10% seawater formalin, preserved in 70% ethanol, among algae, 42°33'N, 139°50'E, Setana, Hokkaido, Japan, 10 May 2010. Paratypes: ZIHU 4254, mounted on SEM stub, same data as for holotype; ZIHU 4270, fixed in 10% seawater formalin, preserved in 70% ethanol, same data as for holotype.

Description.

Eight thoracic and 12 abdominal chaetigers (Fig. 3A). Total length 3.1 mm, crown length 0.6 mm, maximum body width 0.3 mm. Three pairs of radioles, with lateral flanges; proximal 1/2 of radioles connected by palmate membrane. Each radiole with two longitudinal internal cellular supporting axes; each pinnule with one internal cellular supporting axis. Ventral-most radiole with two appendages on each side (Fig. 4A); these appendages (arranged dorsally and ventrally) being almost 1/2 radiole length, and only dorsal one having one internal cellular supporting axis. Distal end of ventral lobe on anterior peristomial ring bifurcate, extending slightly beyond collar margin (Figs 3C, 4A). Posterior peristomial ring collar crenulate (Figs 3A, 3B, 3C, 4A, 4B), with dorsal gap (Fig. 4B). Ciliated patch absent on posterior peristomail ring (Figs 3C, 4A). Glandular ridge on second chaetiger present.

Superior thoracic notochaetae elongate, narrowly hooded, 4-5 per fascicle (Fig. 3D). Inferior thoracic notochaetae bayonet type, four per fascicle; no elongate, narrowly hooded chaetae (Fig. 3D). Thoracic acicular uncini 4-5 per torus; each uncinus having four rows of teeth above main fang (Figs 3E, 4C). Abdominal uncini quadrangular, with eight rows of teeth above large basal tooth (Figs 3F, 4D), 2-9 uncini per fascicle; number of uncini decreasing posteriorly, with eight uncini on first and second abdominal chaetigers, nine on third. Abdominal neurochaetae 2-4 per fascicle, needle-like capillaries in form (Fig. 3G). Pygidium rounded. Peristomial and pygidial eyes and statocysts not visible in preserved specimens. Oocytes found in fourth and fifth thoracic chaetigers.

Etymology.

The specific epithet is an adjective derived from Ezo, the old place name for Hokkaido, in combination with the Latin suffix -ensis.

Remarks.

Amphicorina ezoensis is similar to Amphicorina anneae (Rouse, 1994), Amphicorina eimeri (Langerhans, 1880), and Amphicorina persinosa (Ben-Eliahu, 1975) in having a crenulate collar, three pairs of radioles, and more than eight abdominal chaetigers. Amphicorina ezoensis differs from Amphicorina persinosa in the shape of the collar. In Amphicorina ezoensis , the anterior edge of the collar is perpendicular to the anterior-posterior body axis, and the collar completely covers the anterior peristomium so that the latter is not visible laterally, while in Amphicorina persinosa the collar is oblique in lateral view so that the anterior peristomium is visible, although the angle of the collar is often determined by how the specimen was fixed. Amphicorina ezoensis further differs from Amphicorina anneae and Amphicorina persinosa in the number of ventral radiolar appendage(s). Amphicorina ezoensis has two pairs of appendages, while Amphicorina anneae and Amphicorina persinosa have one pair. The number of ventral radiolar appendage(s) was not mentioned in the original description of Amphicorina eimeri (Langerhans, 1880), but Banse (1957: 72) noted "ventral wenigstens ein Filament" (ventrally at least one filament); Giangrande et al. (1999: 197, Table 1) indicated the species has one pair of appendages, while Rouse (1990: Table 1) lists “1?”. Amphicorina ezoensis also differs from Amphicorina eimeri in that the former possesses elongate, narrowly hooded thoracic chaetae, while the latter has broadly hooded thoracic chaetae ( Rouse 1990, Giangrande et al. 1999). Amphicorina ezoensis also differs from Amphicorina eimeri in the number of the abdominal chaetigers (12 vs. 10).

We were unable to obtain DNA sequence data for this species due to the paucity of material.