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The use of gynogensesis and androgenesis to determine genetic sex of sea lamprey

Jacques Rinchard², Mary-Ann Garcia Abiado², Kyle Ware²,

Andrzej Ciereszko³, Tobie Wolfe², Konrad Dabrowski²

 

 

²School of Natural Resources, The Ohio State University

2021 Coffey Road, Columbus, OH 43210, USA

 

³Department of Molecular Andrology, Polish Academy of Sciences

10-957 Olsztyn, Poland

Abstract

The objective of this study was to understand the sex determination system (genetic sex) of sea lamprey using progenies from gynogenesis and androgenesis experiments. Both gynogenetic and androgenetic sea lamprey were produced.

For gynogenesis experiments, UV-irradiated sperm was used to activate sea lamprey eggs and heat or pressure shocks were applied to inhibit the second meiotic division and consequently induce diploidy in the embryos. The UV-irradiation was performed for 1 minute at 1,719 J/m2. Heat shock of 35 ± 1oC for 2 min and pressure shock of 9,000 psi for 4 min were applied at different times after egg activation (8, 12, 20, and 24 min or 8, 16, and 24 min for heat shock or pressure shock, respectively). Regardless of the induction time of the heat shock, survivals at pre-hatching stage were similar. In contrast, pressure shock applied 8 min after activation appears to increase survival rate of pre-hatched embryos in comparison to 16 and 24 min after activation. All deformed, gynogenetic embryos were haploid and died prior to burying themselves in the sand. Therefore, we concluded that all progenies produced using both methods were diploid gynogenetic.

For the androgenesis experiments, UV-irradiated eggs (1,719 J/m2 for 1 min) were fertilized with non treated sperm and heat shocks were applied to restore diploidy of the eggs. Several attempts have been made to optimize the parameters used. Heat shock of 35 ± 1oC was applied 110, 140, 170, 200, and 230 min after activation for 2 min. Low yields of androgens were obtained and all animals died within a week after hatching.

Gynogenetic sea lampreys were then reared in rectangular troughs with the bottom covered by a thick layer of beach sand and fed active yeast. After 24 months of rearing (August 2003 to July 2005), we have 191 gynogen (average length: 4.7 ± 0.6, n = 60) and 197 control (average length: 5.1 ± 0.8, n = 71) sea lamprey ammocoetes. Gonads were observed in several individuals sampled in December 2004 and July 2005, but they were still undifferentiated containing only primordial germ cell. Therefore, sex ratio in both control and gynogen groups will be confirmed at a later date. Experiments performed in the present study may lead to the first ever completion of life cycle of sea lamprey in captivity, including parasitic stage, that would open even more opportunities for biologists and fisheries scientists and managers alike to better understand sea lamprey biology.