Meeting Abstract
California grunion (Leuresthes tenuis) spawn on the beach during spring tide events. In preparation for spawning, adult grunion fast and have empty guts. Recently, grunion have been found with conspecific eggs in their intestines after spawning, leading to a hypothesis that their eggs provide a potential food resource. However, grunion eggs are structurally resilient, withstanding up to six developmental weeks buried in beach sand, and in vitro tests have failed to destroy eggs with formalin or commercial digestive enzyme preparations. We examined egg digestibility in grunion to determine if the fish can digest their eggs. Grunion were separately fed fertilized and unfertilized eggs, and serially dissected over 10 hours. Comparisons of egg numbers, and egg visual quality, in the proximal, mid, and distal intestine showed eggs being broken down and disappearing (i.e. digested) during the experiment. The amount of force (N) needed to crush eggs taken from grunion digestive tracts was significantly lower than that needed to crush uneaten fertilized and unfertilized eggs. Analysis of aminopeptidase activity showed a characteristic increase moving distally along the intestine, which correlated with a significant decrease in protein concentration of digested eggs. Additional digestive enzyme activity assays in separate intestinal sections, as well as lipid and carbohydrate content of eggs recovered from the intestinal tracts, are underway and should further affirm egg digestibility. Overall, our study confirms that grunion are capable of digesting their eggs, and thus, this food resource may be important after spawning.
