Aidanosagitta neglecta (Aida, 1897)

Choo, Seohwi, Jeong, Man-Ki & Soh, Ho Young, 2022, Taxonomic reassessment of chaetognaths (Chaetognatha, Sagittoidea, Aphragmophora) from Korean waters, ZooKeys 1106, pp. 165-211 : 165

Aidanosagitta neglecta (Aida, 1897)

Sagitta neglecta : Aida, 1897: 16-17 p., fig. 7; Fowler 1906: 15-17 p., fig. 8; Michael 1919: 258 p., table 13, fig. 9; Burfield and Harvey 1926: 99 p, fig. 27; Thomson 1947: 17-18 p.; Tokioka 1959: 373-375 p., table 12, figs 103, 104; Sund 1961: 110 p., table 1; Alvariño 1967: 74 p., table 12, figs 46, 47; Srinivasan 1979: 26-27 p., fig. 14; Nair et al. 2008: 210 p., table 2.

Material examined.

Korea Strait (34°41.577'N, 127°50.460'E), 0-20 m depth, oblique towing with conical net, Feb 2021 (one specimen) .

Description.

Rigid and opaque body. Narrow collarette and extending to half distance from neck to ventral ganglion. Intestinal diverticula present. Grasping spine gently curved. Two rows of stout teeth arranged in comb shape. Two pairs of lateral fins completely rayed, anterior fins beginning at end of ventral ganglion. Seminal vesicles oval-shaped with opening at anterolateral edge, position of seminal vesicles well separated from caudal fin, but touching posterior fins.

Distribution.

This species is found in the epipelagic zone (0-200 m depth) of the Pacific and Indian Oceans ( Pierrot-Bults and Nair 1991) and the coastal waters of the Philippines, India and Hong Kong ( George 1952; Tse et al. 2007; Noblezada and Campos 2008; Lie et al. 2012).

Ecology.

A mature specimen has been reported to be 8 mm is size ( Alvariño 1967). This species shows a diurnal vertical migration in the summer off the Hong Kong coast ( Lie et al. 2012). The temperature range in the sampling stations of this study was 16.40-16.41 °C and the salinity was 34.58 psu.

Remarks.

Only one immature individual was collected in this study. Aidanosagitta neglecta is similar to A. regularis in morphological characteristics including collarette. However, the former had much larger seminal vesicles, thus they can be easily distinguished from each other. Aidanosagitta neglecta collected from Korean waters was smaller than the previously reported adult specimens, but seminal vesicles were obviously swollen in an oval shape. Despite the presence of swollen seminal vesicles, the Korean specimen was considered as immature because its size was smaller than the known record of the adult ( Alvariño 1967).