Implant recognition and gender expression following ampoule-androgenic gland implantation in Litopenaeus vannamei females (Penaeidae)

Abstract

Indirect evidence indicates that penaeids may have a W/Z sex heritability mechanism with the androgenic gland (AG) mediating masculine differentiation. The present study evaluated the immune response against grafts and the expression of primary and secondary male sexual characters in Litopenaeus vannamei females implanted with terminal ampoules and associated AGs. Experiments included grafting females at PL34–48. Grafting at PL37 generated few cases of melanization exhibiting dark coloration covering parts or the whole implant while most implants showed white coloration, without any trace of melanization. Histology of melanized implants showed necrotic tissue, encapsulated by black depositions. These melanized capsules were externally surrounded by normal haemocytes and flat haemocytes in the middle. An experiment evaluating possible absorption of the grafts based on recovery, gross coloration, size of implants, and histology showed that Complete terminal ampoule-AG implants, Control-vas deferens implants and Abdominal muscle implants, recovered at day 7 and 15, exhibited gradual and statistically significant decrease in size, which was more evident for muscle implants. Grafts with normal appearance from this experiment remained viable during 7 and 15days post-implantation; these tissues showed a normal cellular structure with neither signs of melanization nor haemocyte infiltration. Appendices masculinae did not develop in any implanted females or controls. Concerning petasma development, two females implanted with AG showed a male phenotype in their first endopodites, characterized by a straight shape at the distal region, a middle protuberance and absence of setae along the middle curved edge of the structure. Regenerated and intact endopodites of Control-proximal terminal ampoule females showed the typical female phenotype with a slender shape with a curved distal edge, without a middle protuberance, and with setae along the middle curved edge of endopodites. Implanted females showed no evidence of masculinization or abnormal development of oocytes. In the light of the present study the effects of AG transplantation on sex in penaeids should be further evaluated in younger PL stages. Statement of relevanceThis contribution presents new information on sex reversal technology on Litopenaeus vannamei based on androgenic gland implants. The findings are novel for the family Penaeidae concerning the immunological response to tissue grafting and the plasticity for sex reversal in this world aquaculture species.