Pterosagitta draco (Krohn, 1853)

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

Pterosagitta draco (Krohn, 1853)

Figs 3B , 4B , 10B and 12A-D

Spadella draco : Grassi, 1883: 15 p.; Beraneck 1895: 154 p.; Aida 1897: 20 p., fig. 12; Doncaster 1902: 214-215 p.

Pterosagitta draco : Michael, 1919: 264-265 p., table 18; Thomson 1947: 22-23 p.; Tokioka 1965: 351-352 p.; Alvariño 1967: 21-22 p., fig. 11A-D; Srinivasan 1979: 34-35 p., fig. 19A-E; Michel 1984: 29 p., fig. 5; Kim 1987: 33-34 p., plate 12; Park et al. 1990: 71-73 p., fig. 50.

Material examined.

Northern East China Sea (32°30.000'N, 127°5.100'E), 0-120 m depth, oblique towing with conical net, Feb 2020, NIBRIV0000895299 (one specimen) .

Description.

Total body length ranged between 6.5 and 9.1 mm and tail 38.4-40.1% of body length. Hooks 8. Anterior teeth 10 and posterior teeth 12. Rigid and translucent body (Fig. 12 ). Wide and angular head (Fig. 12 ). Wide collarette extending over entire body and reaching anterior of seminal vesicles (Fig. 12A . C). Rectangular eyes with “T” shaped eye pigments (Fig. 12B ). Intestinal diverticula absent (Fig. 3B ). Lateral fins 20.7% of body length. Starting point of lateral fins 65.2% and ending points of lateral fins 86.3% of body length, respectively. One pair of lateral fins triangular-shaped and completely rayed, with forward ends at level of caudal septum (Fig. 12A, D ). Seminal vesicles posteriorly elongated with anterior knob touching lateral fins (Fig. 12C-D ). Eggs reaching middle of body. Corona ciliata anteriorly opened with horseshoe shape beginning in neck region and ending just behind eyes (Figs 10B , 12A ).

Distribution.

This species is located in the epipelagic (0-200 m depth) and mesopelagic zones (200-500 m depth) of the Pacific, Indian and Atlantic Oceans ( Pierrot-Bults and Nair 1991), the epipelagic zone (0-200 m depth) of the Caribbean Sea (Michel,1984), the coastal waters surrounding India ( George 1952) and 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 northern East China Sea (Fig. 1 : station nECS02).

Ecology.

This species is widely distributed in warm water masses and appears all year round in Korean waters, except in the Yellow Sea ( Kim 1987). The temperature range of the Caribbean Sea was reported as 22-29 °C, and salinity range was 33-38 psu ( Michel 1984). At the sampling stations of this study, the temperature ranged between 15.83-28.80 °C and salinity ranged between 31.38-34.60 psu.

Remarks.

The largest specimen collected in this study was 9.1 mm in length, which was at stage 4 maturity. It was smaller than the specimen from New Zealand (16 mm) reported by Lutschinger (1993). It had characteristics consistent with the Pterosagitta draco reported from the Pacific ( Alvariño 1967; Michel 1984), such as the presence of two rows of teeth, one pair of lateral fins, a corona ciliata located between the back of the eye and the neck and a broad collarette extending from the head to seminal vesicles. We observed one specimen for CBE staining pattern: dorsomedian line, 8 dots; dorsolateral line, 25 dots; lateral line, 10 dots; receptors on the lateral fin, 2 dots; anterolateral receptors on the caudal fin, 3 dots; posterior receptors on the caudal fin, 6 dots.

Figures

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

Figure 3. Appearance of body A transparent and flaccid body (Flaccisagitta enflata) B translucent body (Pterosagitta draco) C opaque and rigid body (Aidanosagitta crassa).

Figure 4. Three families inhabiting Korean waters A Ferosagitta robusta (Sagittidae) B Pterosagitta draco; C Krohnitta subtilis (Krohnittidae). Abbreviations: AF = anterior fin; CC = corona ciliata; COL = collarette; CF = caudal fin; E = eye; GS = grasping spine; LF = lateral fin; PF = posterior fin; SV = seminal vesicle; VG = ventral ganglion.

Figure 10. Position and shape of corona ciliata A Aidanosagitta regularis B Pterosagitta draco C Serratosagitta pacifica D Flaccisagitta enflata.

Figure 12. A Pterosagitta draco (dorsal view) B head C tail D lateral fin. Abbreviations: CC = corona ciliata; COL = collarette; E = eye; LF = lateral fin; PT = posterior teeth; SV = seminal vesicle.