236 Shark and Company 



The shark is begotten in an embrace of the male and the female. 

 The male grasps the female and their bodies entwine. In this union their 

 young are conceived. Their union is an act fairly rare in the sea, where 

 many fishes accomplish reproduction without even touching. 



Aristotle saw sharks embrace, and wrote with amazing insight about 

 their breeding and the prenatal development of their young. Not until 

 the nineteenth century, however, was the copulation of sharks redis- 

 covered by Louis Agassiz, an American marine biologist. 



In more recent times, the breeding of sharks has been frequently 

 seen and recorded. E. W. Gudger of the American Museum of Natural 

 History gave a vivid account of the copulation of Nurse sharks 

 {Ginglymotsoma cirratum): 



Nurse sharks come into very shallow water to mate, and pairs, so engaged, 

 are often seen. External signs of the breeding season may be shown by the 

 tattered hinder edges of the pectoral fins of the females. This is due to the fact 

 that the male, prior to copulation, grasps the posterior edge of one or the other 

 of these fins in his mouth. Due to his smallness and the inferiority of his dental 

 armature, the female not infrequently breaks away, tearing and scarring the 

 edges of her fin in the escape. 



Once, however, that a secure hold is attained, she is flipped over on her back 

 and the male then inserts his claspers in the lateral pockets of her cloaca, and 

 the seminal fluid is transferred. 



The breeding habits of sharks dramatically set them apart from the 

 vast majority of Teleost fishes. Most fish reproduce differently: eggs and 

 sperm are shed in the water, and there, with the dispassion of pollen 

 borne on the winds, fertilization takes place. 



Fertilization among Selachians is invariably by intercourse. The 

 males perform intercourse with claspers (mixoptery gia) , appendages of 

 the pelvic fins, which are supported by cartilage. Each male has two clasp- 

 ers, located between the two pelvic fins. Ordinarily, the claspers trail 

 close to the fins and are often mistaken for part of the fins themselves. 

 When copulation is to begin, however, the fins are erected at right angles 

 to the body. Observation of such courtship is very rare, and much of the 

 sex life of the Selachians is cloaked from man's eyes by the sea. 



The shark's use of two claspers is not yet fully understood. The most 

 modern theory is that only one clasper is used at a time. There is specula- 

 tion, though, that both claspers are thrust into the female at the same 

 time. The clasper is grooved, and along this groove passes the seminal 

 fluid. The female has two body openings (which, in maiden sharks, are 

 sealed by hymen-like membranes, another fact discovered by Aristotle). 

 Whether singly or simultaneously, both orifices of the female appear to 

 be used during mating. In some species, this may last for about 20 

 minutes. 



Male and female sharks of the same species seem to be specially 



