Amphogona apsteini ( Vanhöffen, 1902 )

Schuchert, Peter & Collins, Richard, 2021, Hydromedusae observed during night dives in the Gulf Stream, Revue suisse de Zoologie 128 (2), pp. 237-356 : 332-334

Amphogona apsteini ( Vanhöffen, 1902)

Fig. 59 A-B

Pantachogon apsteini Vanhöffen, 1902: 65 , pl. 10 fig. 18, pl. 11 fig. 28.

Amphogona apsteini . ‒ Browne, 1905: 740, pl. 54 fig. 5, pl. 56 fig. 1, pl. 57 figs 10-15. ‒ Bigelow, 1909: 126, pl. 2 figs 1-2, pl. 34 figs 12-15, pl. 45 fig. 10. ‒ Mayer, 1910: 405, fig. 257. ‒ Kramp, 1959a: 188, fig. 280. ‒ Kramp, 1965: 123, figs 12-13. ‒ Kramp, 1968: 118, fig. 319. ‒ Bleeker & Van der Spoel, 1988: 241, fig. 37.

Examined material: BFLA; 1 specimen; 09-DEC- 2019; size 2 mm, juvenile; preserved in alcohol for DNA extraction; 16S sequence could not be obtained as PCR failed repeatedly. – 05-JUL-2019; 2 specimens photographed, 2 mm, not collected.

Observations: Bell diameter 2 mm, flatter than hemisphere, jelly relatively thin especially towards margin; with thin gastric peduncle reaching almost to level of velum ( Fig. 59B ); stomach small, lips inconspicuous. Eight radial canals. Gonads when fully developed ellipsoidal, pendant, close to ring canal, all of equal size or larger ones and smaller ones alternating; long axis of ellipsoidal gonads vertical ( Fig. 59A ). About 70 tentacles, all the same structure. One to two statocysts per octant.

Distribution: Circumglobal in warm waters. In the Indian Ocean from Indonesia to Moçambique ( Kramp, 1953, 1968; Bouillon, 1978a); in the Pacific Ocean from eastern Australia, to the northern Part of the China Sea and Peru ( Kramp, 1953, 1965; Bouillon, 1978c; Du et al., 2010; Oliveira et al., 2016). In the South Atlantic from Argentina to Brazil and to western Africa ( Kramp, 1955b; Nagata et al., 2014; Oliveira et al., 2016). In the North Atlantic reported from the mid Atlantic to Florida ( Bleeker & Van der Spoel, 1988; Larson et al., 1991; this study). Type locality: Indian Ocean, west coast of Sumatra.

Remarks: Kramp (1959a, 1965, 1968) states that the unequal size of the gonads, with small and larger ones alternating, is a characteristic trait of this species. However, this is found only in younger specimens, mature ones seem to have equally developed gonads ( Bigelow, 1909; Nagata et al., 2014). Kramp gives also a bell size of 4 to 6 mm. Our specimens were smaller (2 mm). The type material was 2 to 3 mm in size, although perhaps not fully mature. Also Nagata et al. (2014) give a bell size of 2 to 3 mm.

Figures

Fig. 59. Amphogona apsteini, bell size 2 mm, 09-DEC-2019. (A-B) Two separate individuals. (C) Close up of manubrium and gastric peduncle.