P2.45 Thursday, Jan. 5 Terrestrial development in embryonic mangrove rivulus (Kryptolebias marmoratus) WELLS, M.W.*; TURKO, A.J.; WRIGHT, P.A.; University of Guelph, ON; University of Guelph, ON; University of Guelph, ON firstname.lastname@example.org
The mangrove rivulus, Kryptolebias marmoratus, inhabits small pools of water in highly variable mangrove swamps. Adult rivulus will leave the water when aquatic conditions become unfavorable (e.g. hypoxia, H2S) and can remain in the moist leaf litter for days to weeks. In the laboratory, adults are known to voluntarily deposit embryos terrestrially without obvious consequences for development and hatching, however wild rivulus embryos have never been observed. We hypothesized that wild mangrove rivulus emerse and release their embryos terrestrially as a strategy for avoiding the challenging aquatic conditions of the mangrove swamps. As such, the biology of amphibious reproduction was investigated in adults and embryos. We tested the effects of air exposure on adult reproductive output and embryonic development, along with the various environmental hatching triggers commonly associated with terrestrial development. Adult rivulus, which were air exposed for 96 hours, were found to have a higher reproductive output compared to aquatic controls. The metabolic rate of embryos reared in air was 2-fold higher relative to aquatic controls. These findings suggest potential fitness advantages to terrestrial development and can also act as a strategy for avoiding the harsh environmental conditions of mangrove swamps. In terms of hatching triggers, freshwater elicited no hatching response, while hypoxia (aquatic and terrestrial) triggered hatching in >90% of embryos. This suggests that rivulus are able to detect oxygen levels in both water and on land, which could provide an effective way of avoiding mortality from oxygen depravation and ensuring safe return to the water. Overall, the results support the hypothesis that rivulus may exploit terrestrial niches in the wild.