Evidence of pre-zygotic barriers in attempts to cross-breed Penaeus (Litopenaeus) vannamei (Boone) and P.(Litopenaeus) stylirostris (Stimpson) by means of artificial insemination

The feasibility of cross-breeding of Pacific white shrimp, P. (Litopenaeus) vannamei (PV) and blue shrimp, P. (Litopenaeus) stylirostris (PS), by means of artificial insemination, was evaluated. Intra-specific (pure species) crosses were used as control treatments: 1) ♂PV × ♀PV and 2) ♂PS × ♀PS. Reciprocal, inter-specific (hybrid) crosses 3) ♂PV × ♀PS and 4) ♂PS × ♀PV, were performed employing a variety of artificial insemination techniques. Twelve intra-specific inseminations of white shrimp (♂PV × ♀PV) were performed. All inseminated females spawned eggs, ranging from 70,111 to 139,940 eggs per spawn. Five out of the 12 spawns produced nauplii (14,241 nauplii per spawn), with a mean hatch rate of 11.7%. For intra-specific blue shrimp crosses (♂PS × ♀PS), 13 out of 14 inseminated females spawned eggs ranging from 112,349 to 282,141 eggs per spawn, and obtaining three fertile spawns with a mean hatch rate of 12.8% and 24,588 nauplii per spawn. For the inter-specific crosses, a total of 49 hybridization attempts were made, 27 for the cross ♂PV × ♀PS and 22 for the reciprocal cross ♂PS × ♀PV. In spite of trying artificial insemination in various ways, none of the hybridization attempts was successful; indicating that cross-breeding of white and blue shrimp is not possible by means of traditional artificial insemination techniques.