Production of live young with cryopreserved sperm from the endangered livebearing fish Redtail Splitfin (Xenotoca eiseni, Rutter, 1896)

Abstract

Previous studies of sperm cryopreservation of livebearing fish have been limited to two genera within the family Poeciliidae. The goal of the present study was to investigate the feasibility to produce live young of livebearing goodeids (family Goodeidae) with cryopreserved sperm, using aquarium-trade populations of the endangered species Redtail Splitfin (Xenotoca eiseni, Rutter, 1896). Reproductive condition of females was evaluated by histological categorization of ovarian development. A total of 117 females were inseminated with cryopreserved sperm, 81 were inseminated with fresh sperm, 27 were mixed with males for natural breeding, and 30 were maintained without males or insemination. Histological images of 34 mature females indicated 68% of ovaries had primary- or secondary-growth oocytes, and 32% had ovulated eggs. Ovarian development had no significant relationship (P = 0.508) with body wet weight, but had a relationship (P < 0.001) with ovary weight and gonadosomatic index. Sperm cells were observed within ovaries that were fixed at 12 h after insemination with fresh sperm. A total of 29 live young were produced from two females inseminated with thawed sperm (8% post-thaw motility with HBSS300 as extender, 20 min incubation in 15% DMSO, cooling rate at 10 °C/min, and thawing at 40 °C for 7 s), 12 were produced from two females with fresh sperm (1%-20% motility), 41 were produced from five naturally spawned females, and no live young were produced from the female-only group. This study provides a foundation for establishment of germplasm repositories for endangered goodeids to assist conservation programs.

Opportunities and Limitations for Reproductive Science in Species Conservation

“…This strategy has led many to call for the expansion of ex situ conservation plans for threatened fish species, including the use of cryopreserved spermatozoa and GRBs (114,116), and some progress has been made. One interesting example concerns the successful breeding from cryopreserved spermatozoa of redtail splitfin (Xenotoca eiseni, Rutter, 1896), a small (length 6-7 cm) freshwater member of the live-bearing Goodeidae family from Mexico (117). Both sperm storage and oocyte fertilization in this species take place within the ovarian follicle (118).…”

“…Consequently, embryonic development also takes place in the follicle, with the embryos receiving some nutritional support from placenta-like structures. Of note, although Liu et al (117) were investigating the use of such small fishes in biomedical research, the IUCN (111) has classified this species, along with 12 others, as critically endangered (3 are already extinct in the wild). The successful development of sperm cryopreservation and insemination shows the conservation feasibility of storing cryopreserved spermatozoa in GRBs for future use.…”