Krohnitta pacifica (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

Krohnitta pacifica (Aida, 1897)

Krohnitta pacifica : Tokioka, 1965: 352-353 p.; Alvariño 1967: 15-17 p., fig. 7A-E; Michel 1984: 29 p., fig. 40; Kim 1987: 35-36 p., plate 13; Park et al. 1990: 73 p., fig. 51.

Material examined.

Northern East China Sea (32°29.420'N, 127°29.654' E), 20-100 m depth, oblique towing with MOCNESS, Aug 2020 (one specimen) .

Description.

Slender and transparent body. Small head. Grasping spines abruptly curved. One row of stout teeth arranged in fan shape. One pair of lateral fins partially rayed, forward and equidistant from caudal septum. Lateral fins positioned at anterior end, at level of caudal septum with rayed lateral fins. Caudal fin damaged. Collarette and intestinal diverticula absent. No seminal vesicle visible.

Distribution.

This species is found in the epipelagic zone (0-200 m depth) of the northern Indian Ocean ( Pierrot-Bults and Nair 1991), the Gulf of Mexico ( Pierce 1951) and the Japanese coast (Tosa Bay, Sagami and Suruga) ( Nagasawa and Marumo 1972; Ohnishi et al. 2014) and, in this study, it was found in the epipelagic zone (20-100 m depth) of the northern East China Sea (Fig. 1 : station nECS03).

Ecology.

An inhabitant of the surface layer of the warm oceanic waters ( Tokioka 1940). Mature specimen was reported to be 6-8 mm in length ( Alvariño 1967). The temperature range in the sampling stations of this study was 18.49-28.84 °C and salinity range was 30.71-34.59 psu.

Remarks.

Only immature individuals could be collected in this study. The specimens of K. pacifica we observed had one pair of fins and the structure of the fin was rayed, except for the base part close to the body. These were distinct characteristics of K. pacifica that differentiated it from K. subtilis . Since seminal vesicles were not observed in all observed Korean specimens, they were classified as immature stage ( Alvariño 1967).

Figures

Figure 1. Sampling stations in Korean waters. Empty circles, sampling stations; filled circles, the stations where the chaetognaths were secured.