A guide to the embryonic development of the shovelnose sturgeon (Scaphirhynchus platorynchus), reared at a constant temperature

Abstract

Summary Described is the sequence and timing of embryologic development of shovelnose sturgeon, (Scaphirhynchus platorynchus) reared at a constant temperature 20 ± 0.5°C. Artificially spawned, fertilized eggs were held in a recirculating system. Embryos were sampled hourly during the first 48 h of development and every 3 h thereafter. Embryos were viewed and imaged at 35× magnification. The first cleavage furrow appeared 2 h post-fertilization; early (synchronous) cleavage was completed after 7 h. Blastulation concluded at 16 h when the dorsal blastopore lip formed. The slitlike blastopore appeared at 29 h, signifying the completion of gastrulation. At 33 h, the rudiments of the excretory system emerged, followed by closing of the neural tube at 36 h and formation of the s-shaped heart at 60 h. The body continued to elongate with mass hatch occurring at 102 h. After hatch, larvae swam into the water column and drifted in the flow for approximately 2 days after which the larvae became positively rheotaxic. After expulsion of the pigment plug, the larvae began exogenous feeding and other structures continued to develop. Metamorphosis was completed after 26 days of development. Because the shovelnose sturgeon possesses developmental patterns similar to those of other sturgeon, we can use this species as a model for the closely related pallid and Alabama sturgeon.