

I 



Viviparous Fishes - in - General 



DAVID G. STEAD, F. L. S. 



Naturalist to Board of Fisheries, N. S. W. 



The reproduction of fishes in general 

 may be carried out in one of two ways : 



1. By the production of living- young. 



2. By means of eggs. 



Those species which produce living 

 young (and which are, consequently, 

 called viviparous), are in the minority, 

 and are principally confined to the Elas- 

 mobranchs (sharks, rays, etc.) At the 

 same time there are many viviparous 



Lebistes reticulatus 



Teleosteans or "bony-fishes." Some of 

 these produce young which are fully de- 

 veled and practically exact counterparts 

 of the parent fish. This condition of 

 things reaches its greatest development, 

 perhaps in the Bmbiotocidae, a family of 

 fishes inhabiting the waters of California 

 and Japan. They are small or moderate- 

 sized fishes, chiefly marine, though one 

 species has been taken from fresh waters. 

 At birth the young are relatively large 

 and similar in form to the adult fish. 

 Most of the species of these Embiotocids 



are to be found in the vicinity of the surf 

 on sea beaches, from which habit they are 

 often known as "surf-fishes." 



Another family of teleosteans that 

 must be mentioned as containing many 

 viviparous species is that of the Poeci- 

 liidae, known in America as "killifishes." 

 The species of this family are usually of 

 small size, inhabit fresh waters and prin- 

 cipally abound in America. Some are 

 egg-producing, or oviparous, while others, 

 as pointed out, are viviparous. In the 

 oviparous species the males and females 

 are very nearly alike, both in point of 

 size and in color, but in many of the vivi- 

 parous forms there is a great difference 

 between the sexes. This shows itself 

 particularly in the form of the body 

 which, in the male, is only about half the 

 length of that of the female, and in which 

 also the anal fin is placed far forward. 

 It will be of interest here to note that 

 these viviparous killifishes include 

 amongst their number those highly re- 

 markable forms known as the "four-eyed 

 fishes" (Anableps), which inhabit Cen- 

 tral America. In these the integuments 

 of each eye are divided into an upper and 

 lower portion by a dark-colored trans- 

 verse band, the pupil becoming incom- 

 pletely divided into separate lobes. These 

 "four-eyed" fishes swim at the surface 

 of the water, with the upper half of the 

 eye (which projects above the upper sur- 

 face of the head) out of the water, this 

 enabling them to clearly distinguish ob- 

 jects, both above and below the water, 

 at the same time. 



Other families of teleostean fishes 



