Comparative Embryogeny and Early Development of Threadfin and Gizzard Shad

Abstract The embryogeny of threadfin shad (Dorosoma petenense) and gizzard shad (D. cepedianum) is closely similar. No major difference was observed during cleavage or organogenesis, but at all temperatures gizzard shad hatched sooner than threadfin shad and were less completely developed at hatching. In both species the anterior gut and mouth were incompletely developed at hatching. Threadfin shad larvae had scattered melanophores and pigmented eyes at hatching but gizzard shad larvae were devoid of pigment for about 1 day. The developmental period of threadfin shad was about twice that for gizzard shad at temperatures between 18 and 24°C.