Behavioral and Physiological Responses of an Amphibious, Euryhaline Mangrove Fish to Acute Salinity Exposure

Amphibious fishes moving over land between aquatic habitats likely encounter abrupt changes in a number of environmental conditions, including salinity. This study characterized the 1) spatial heterogeneity in salinity in the mangrove forest habitat of the self-fertilizing, amphibious mangrove rivulus (Kryptolebias marmoratus), 2) metabolic cost and behavioral response to acute exposure to novel salinity, and 3) repeatability of individual responses to acute changes in salinity. In mangrove habitats on Long Caye, Belize, salinity varied widely over short distances from 20.9–41.7‰ over a 90 cm distance. In the lab, fish were exposed to an acute change in salinity of Δ10, 20, or 30‰. Oxygen consumption significantly decreased in response to a 10‰ decrease in salinity and increased when salinity was elevated by 30‰. Activity levels significantly increased with an increase in salinity (Δ20 and 30‰). Individuals showed repeatable differences in both oxygen consumption rates and activity levels. Together, our data show that K. marmoratus is highly responsive to abrupt increases in salinity. Thus, movements made by K. marmoratus between temporary pools in the mangrove forest will acutely alter behavior and possibly metabolism, with many potential ecological consequences.