Aidanosagitta regularis (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

publication ID	https://dx.doi.org/10.3897/zookeys.1106.80184
publication LSID	lsid:zoobank.org:pub:EFA7EF37-2B83-458D-931D-9A53DB311472
persistent identifier	https://treatment.plazi.org/id/ACA7B54C-85E1-55CD-AA86-38C29B02F1F8
treatment provided by	ZooKeys by Pensoft
scientific name	Aidanosagitta regularis (Aida, 1897)
status

Treatment

Figs 6A View Figure 6 , 7A View Figure 7 , 10A View Figure 10 , 20A-E View Figure 20

Sagitta regularis : Aida, 1897: 17-18 p., fig. 8; Doncaster 1902: 211 p., fig. 7; Burfield and Harvey 1926: 100 p., figs 31-32; Thomson 1947: 18-19 p.; Alvariño 1967: 72-75 p., fig. 48A-D; Srinivasan 1979: 31-32 p., fig. 17A-F; Nair et al. 2008: 110 p., table 2.

Material examined.

Korea Strait (33°33.600'N, 127°34.002'E), 0-96 m depth, oblique towing with conical net, Feb 2020, NIBRIV0000895302 (one specimen) GoogleMaps ; northern East China Sea (32°33.000'N, 126°30.000'E), 0-100 m depth, oblique towing with conical net, Feb 2020, NIBRIV0000895301 (one specimen) GoogleMaps ; northern East China Sea (32°30.000'N, 127°5.100'E), 0-120 m depth, oblique towing with conical net, Feb 2020 (one specimen) GoogleMaps .

Description.

Total body length ranged within 6.1 and 6.7 mm. Tail 30.5-31.7% of body length. Hooks 6. Anterior teeth 3-4 and posterior teeth 5-6, respectively. Rigid and opaque body (Fig. 20 View Figure 20 ). Head small, triangular shaped (Fig. 20B View Figure 20 ). Round eyes with “B” -shaped eye pigments (Fig. 20B View Figure 20 ). Collarette expanding to seminal vesicles (Fig. 20A View Figure 20 ). Corona ciliata beginning from neck to anterior of ventral ganglion (Fig. 10A View Figure 10 ). Anterior fins 12.3% of body length. Anterior fins beginning at posterior of ventral ganglion. Starting points of anterior fins 37.3% and ending points of anterior fins 50.9% of body length, respectively (Fig. 20D View Figure 20 ). Posterior fins 22.0% of body length and 1.8 times longer than anterior fins. Starting points of posterior fins 62.9% and ending points of posterior fins 84.7% of body length, respectively. Posterior fins not connected to anterior fins, beginning in front of caudal septum and both anterior fins and posterior fins completely rayed (Fig. 20D, E View Figure 20 ). Caudal fin fully rayed and roughly round or triangle-shaped (Fig. 20C View Figure 20 ). Intestinal diverticula present (Figs 7A View Figure 7 , 20B View Figure 20 ). Seminal vesicles longitudinally elongated along body (Fig. 20C View Figure 20 ). Eggs reaching posterior of ventral ganglion.

Distribution.

This species is found in the epipelagic (0-200 m depth) and mesopelagic zones (200-500 m depth) of Pacific and Indian Oceans ( Pierrot-Bults and Nair 1991) and the epipelagic zone (0-100 m depth) of the Tosa Bay in Japan ( Ohnishi et al. 2014). In this study, it was found in the epipelagic zone (0-120 m depth) of the Korea Strait and northern East China Sea (Fig. 1 View Figure 1 , stations KS06, nECS01 and nECS02).

Ecology.

This species is considered a warm-water Indo-Pacific indicator species because many individuals appear in high-temperature and high-salinity water and the distribution range is limited to the areas affected by warm currents ( Park 1970).

Remarks.

Amongst the Korean specimens, the collarette was differently inflated, thick and covered the body surface. However, the position and shape of the corona ciliata and fins were consistent with the original description ( Aida 1897). Aidanosagitta regularis is similar to A. bedfordii ; however, these two species can be distinguished by the morphological difference in the eye pigments (elongated vs. roundish). We observed two specimens for CBE staining pattern: dorsomedian line, 28 dots; dorsolateral line, 34 dots; lateral line, 44 dots; receptors on the lateral fin, 3 dots; anterolateral receptors on the caudal fin, 2 dots; posterior receptors on the caudal fin, not observed due to damage.