Hydromedusae observed during night dives in the Gulf Stream Author Schuchert, Peter Muséum d’histoire naturelle, C. P. 6434, CH- 1211 Genève 6, Switzerland peter.schuchert@ville-ge.ch Author Collins, Richard 880 NE 33 rd Street, Boca Raton, Florida, USA rc6684@icloud.com text Revue suisse de Zoologie 2021 2021-10-21 128 2 237 356 journal article 10.35929/RSZ.0049 172fa5c5-c0c4-4bd7-b710-d608237b8458 0035-418 5639938 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. Fig. 58. Aglaura hemistoma . (A-B) Sample BFLA3808, bell size 2 mm, oblique views from oral side. The statocysts can be seen in B as tiny, bright spots along the ball margin. (C) Animal photographed 20-AUG-2018, bell size 3 mm. (D) BFLA4214, bell size 2 mm, lateral view. Fig. 59. Amphogona apsteini , bell size 2 mm, 09-DEC-2019. (A-B) Two separate individuals. (C) Close up of manubrium and gastric peduncle. 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 .