Zonosagitta bedoti ( Beraneck , 1895)

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

Zonosagitta bedoti ( Beraneck, 1895)

Figs 7D , 21A-E

Sagitta bedoti f. minor : Tokioka, 1959: 89-90 p., table 18.

Sagitta bedoti : Béraneck, 1895: 147-152 p.; Fowler 1906: 6-8 p., figs 1-8; Michael 1919: 255-257 p., figs 6, 20, 24, 30; Burfield and Harvey 1926: 94-95p., figs 1-2; Thomson 1947: 18 p.; Kitou 1966: 239 p., table 1; Alvariño 1967: 53-55 p., fig. 32A-D; Francisco 1977: 229-231 p., plate 2; Srinivasan 1979: 6-7 p., fig. 2A-G.

Material examined.

Korea Strait (33°0.000'N, 125°18.000'E), 0-75 m depth, oblique towing with conical net, Feb 2020, NIBRIV0000895300 (one specimen); northern East China Sea (31°30.000'N, 126°28.998'E), 0-82 m depth, oblique towing with conical net, Feb 2020 (one specimen) .

Description.

Total body length ranged from 16-17 mm. Tail 3.71% of body length. Hooks 7. Anterior teeth 27-28 and posterior teeth 30-35, respectively. Opaque and rigid body (Fig. 21 ). Head wider than body (Figs 7D , 21A ). Short and dense teeth. Intestinal diverticula absent (Figs 7D , 21B ). “D” -shaped eyes with star-shaped eye pigments (Fig. 21B ). Corona ciliata beginning behind eyes and elongated over neck (Fig. 21B ). Anterior fins 26.5% of body length. Anterior fins beginning at middle of ventral ganglion, anterior of anterior fins narrow with rayless zone and posterior of anterior fins partially rayed. Anterior fins 1.3 times longer than posterior fins. Starting points of anterior fins 34.3% and ending points of anterior fins 60.0% of body length, respectively (Fig. 21A, D ). Posterior fins 19.8% of body length. Starting points of posterior fins 63.7% and ending points of posterior fins 89.7% of body length, respectively. Posterior fins connected with anterior fins (Fig. 21A ). Caudal fin triangular-shaped and completely rayed (Fig. 21C ). Seminal vesicles spherical in shape with lateral rupture in mature specimen (Fig. 21C ).

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 Tosa Bay in Japan ( Ohnishi et al. 2014). In this study, it was found in the epipelagic zone (0-100 m depth) of the Korea Strait and northern East China Sea (Fig. 1 : stations KS09 and nECS06).

Ecology.

Zonosagitta bedoti is used as an indicator species in the front area where warm and cold water meet ( Park 1970). The temperature range in the sampling location in this study was between 14.62 and 15.01 °C and the salinity range was 33.67-33.81 psu.

Remarks.

Zonosagitta bedoti and Z. nagae are similar in morphology at the immature stage. However, because adult Z. nagae are relatively larger, immature Z. nagae may be misidentified as Z. bedoti . Adults of both species can be distinguished from each other by the shape of seminal vesicles and eye pigments. Zonosagitta nagae has an “E” -shaped eye pigment, while Z. bedoti has a star-shaped eye pigment. The spot pattern on the body surface found through CBE staining is as follows: irregular spot pattern which continued from the head to the ventral ganglion and six spots along the outside of the body were symmetrical around the tail.

Figures

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

Figure 7. Intestinal diverticular (shown by white arrow) A Aidanosagitta regularis (present) B Ferosagitta robusta (present) C Zonosagitta nagae (absent) D Zonosagitta bedoti (absent).

Figure 21. A Zonosagitta bedoti (dorsal view) B head C tail D anterior fin E posterior fin. Abbreviations: AF = anterior fin; E = eye; PF = posterior fin; SV = seminal vesicle.