Serratosagitta pacifica (Tokioka, 1940)

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/A8ABB4FE-C60B-57B2-A94D-C4E8BD18CAE4
treatment provided by	ZooKeys by Pensoft
scientific name	Serratosagitta pacifica (Tokioka, 1940)
status

Treatment

Figs 6F View Figure 6 , 8C View Figure 8 , 10C View Figure 10 , 13A-E View Figure 13

Sagitta serratodentata pacifica : Tokioka, 1959: 72-80 p., fig. 10, table 10; Park et al. 1990: 52-54 p. figs 31, 32.

Sagitta pacifica : Alvariño, 1961: 71 p., fig. A, B, table 2; Alvariño 1967: 36-39 p., fig. 22A-D; Pierrot-Bults 1974: 221-222 p., fig. 6; Francisco 1977: 226-229 p., plate 1; Srinivasan 1979: 27-29 p., fig. 15A-G; Kim 1987: 18-20 p., plate 3.

Serratosagitta pacifica : Tokioka, 1965: 345-346 p.; Lutschinger 1993: 30-31 p., fig. 15 A-B.

Material examined.

Korea Strait (33°24.504'N, 127°54.600'E), 0-50 m depth, oblique towing with MOCNESS, May 2019, NIBRIV0000895311 (two specimens) GoogleMaps ; Korea Strait (33°33.600'N, 127°34.002'E), 0-96 m depth, oblique towing with conical net, Feb 2020 (one specimen); northern East GoogleMaps China Sea (32°33.000'N, 126°30.000 E), 0-100 m depth, oblique towing with conical net, Feb 2020, NIBRIV0000895310 (three specimens); northern East GoogleMaps China Sea (32°00.000'N, 127°4.098'E), 0-120 m depth, oblique towing with conical net, Feb 2020, two specimens GoogleMaps .

Description.

Total body length ranged within 11.8 and 13.7 mm. Tail 23.4-24.9% of body length. Hooks 6-7. Anterior 10-13 and posterior teeth 16-25. Rigid and opaque body (Fig. 13A View Figure 13 ). Small head (Fig. 13A, B View Figure 13 ). Grasping spines serrated on edge (Fig. 8C View Figure 8 ). Collarette absent (Fig. 10C View Figure 10 , 13A View Figure 13 ). Rectangular eyes with “T” shaped eye pigments (Fig. 13B View Figure 13 ). Intestinal diverticula absent (Fig. 10C View Figure 10 ). Anterior fins spanned 21.9% of body length. Anterior fins completely rayed beginning between ventral ganglion and caudal septum. Starting point of anterior fins 34.6% and ending points of anterior fins 55.1% of body length, respectively (Fig. 13A, D View Figure 13 ). Posterior fins 26.2% of body length and 1.2 times longer than anterior fins. Starting points of posterior fins 63.7% and ending points of posterior fins 89.7% of body length, respectively. Posterior fins well-separated from anterior fins (Fig. 13A, E View Figure 13 ). Caudal fin triangular shaped (Fig. 13A, C View Figure 13 ). Seminal vesicles touched or closed to lateral fins and well-separated from tail fin (Fig. 13C View Figure 13 ) with elongated knob facing obliquely forward and teeth-like appendages forming 5-10 distal protrusions. Eggs reached anterior of anterior fins. Collarette beginning in front of eyes and extended over neck (Fig. 10C View Figure 10 , 13A View Figure 13 ).

Distribution.

This species is found in the epipelagic (0-200 m depth) and mesopelagic zones (200-500 m depth) of the Pacific and Indian Oceans ( Alvariño 1967; Pierrot-Bults and Nair 1991), the epipelagic zone of Red Sea, Californian waters ( Pierrot-Bults 1976) and the Tosa Bay in Japan ( Ohnishi et al. 2014). In this study, it was distributed in the epipelagic zone (0-50 m depth) of the Korea Strait and northern East China Sea (Fig. 1 View Figure 1 : stations KS06, KS07, nECS01 and nECS04).

Ecology.

This species mainly inhabits Indo-pacific warm-water masses ( Bieri 1959). In the Pacific Ocean, it is a known indicator species of the Kuroshio Water Mass ( Kim 1987). In this study, the temperature range of sampling locations was 16.37-20.57 °C and salinity ranged between 34.48-34.61 psu.

Remarks.

The seminal vesicles are used as an important morphological feature to identify the genus Serratosagitta . S. serratodentata has thick collarette tissue in front of the seminal vesicles and two projections at the anterior-lateral corner. The seminal vesicles touch the end of posterior fins ( Alvariño 1961). The seminal vesicles of S. pseudoserratodentata have one projection at the front corner, with small teeth at the anterior end. The seminal vesicles are well-separated from the posterior fins and caudal fin ( Alvariño 1961). In the S. pacifica (nine specimens), the number of protrusions vary between 5 and 10. The inner serrated row of the grasping spine and the "teeth cells" forming protrusions at the anterior margin of the seminal vesicles were consistent with previous records ( Alvariño 1967; Pierrot-Bults 1976). We observed three specimens for CBE staining pattern: dorsomedian line 43 dots; dorsolateral line, 54-69 dots; lateral line, 24 dots; receptors on the lateral fin, 10 dots; anterolateral receptors on the caudal fin, 2 dots; posterior receptors on the caudal fin, 3-4 dots. The dorsomedian dots are patterned as small spots that cross the centre of the body and larger symmetrical spots on dorsolateral line dots.