SUMMARY 29 



SUMMARY 



i. An adult female Ceratiid fish, 43-0 cm. standard length, was removed from the stomach of 

 a Sperm whale shot in the Antarctic Ocean in December 1947. 



2. It is identified as the rare bathypelagic angler fish, Cer alias holbolli Kroyer, 1844, by detailed 

 comparison of the external features, fishing lure, caruncles and viscera, with Kroyer's account and with 

 a specimen preserved in the Natural History Museum. 



3. Adult specimens of this fish have previously only been recorded from the coast banks of northern 

 seas. This adult is the first from oceanic water. 



4. An observation on the adjustability of the fishing lure, made when the Antarctic specimen was 

 recovered, confirms Bertelsen's conclusions from anatomical structure (1943). The musculature of the 

 lure in Ceratias is compared with that in another Ceratioid genus, Gigantactis. 



5. The viscera of Ceratias and Gigantactis are compared. In general they are similar, but Ceratias 

 possesses two pyloric caeca; these are altogether lacking in Gigantactis. Neither genus possesses 

 a swim-bladder. 



6. The ovaries of the Antarctic specimen were regressed and contained very young eggs, suggesting 

 a much restricted breeding season which may have been a major stimulus in the evolution of attached 

 males for these solitary, sluggish fishes. 



7. A study of allometric growth in Ceratias holbolli provides further evidence for Bertelsen's claim 

 that the species of Mancalias are juveniles of Ceratias. The dimensions of thirteen specimens, repre- 

 senting ' species ' of Mancalias and Ceratias are found to conform to the simple allometry equation 

 y = bx a . The allometry of the various parts is described and its significance discussed. 



8. In particular, the growth of eyes and nostrils is strongly negatively allometric. During ontogeny 

 the tubular mostrils of the young fish suffer reduction to vestigial tags in the adult ; and the conjunctiva 

 of the eye is borne across the eyeball, which becomes subcutaneous, so that the adult is functionally 

 blind. 



9. In the young fish the caruncles are the only organs which clearly show positive allometry, but at 

 about 12 cm. standard length caruncle growth becomes enantiometric and thereafter the caruncles 

 dwindle in absolute size. The onset of this enantiometry is believed to betray a crisis in development, 

 which is probably sexual maturity. The caruncles may be recognition marks for the males. 



10. The systematics of Ceratias are discussed and revised, principally on the evidence of allometric 

 growth. Bertelsen's southern species C. tentaculatus is considered invalid and the genus reduced to the 

 single species C. holbolli Kroyer, 1844. 



11. Parenthetically, it is emphasized that routine examination of Sperm whale stomachs could 

 increase our scanty knowledge of the nektonic macrofauna. Some bathypelagic squids and fishes may 

 be more common and grow larger than is at present supposed. 



12. C. holbolli is of world-wide distribution, extending from equatorial to polar seas. Its known 

 bathymetric distribution ranges from 1000 to 120 m. from the surface. This upper limit is only 

 attained in high latitudes where the fish extends into the mesopelagic zone. 



13. Tropical submergence can account for these aspects of horizontal and vertical distribution- 

 Light intensity is considered to be more important than temperature as a factor limiting the ventrical 

 range of C. holbolli at any one latitude. 



14. Evidence is offered against the theory that C. holbolli and certain other fishes (notably Paralepis 

 spp.), taken off the Greenland and Iceland coasts, have been forced towards the surface by the cold 

 polar current. A tentative hypothesis is advanced regarding the distribution of C. holbolli in relation to 

 the ocean currents, especially of the southern hemisphere. 



