To develop a molecular probe for whole-body fat stores in largemouth bass Micropterus salmoides. An antibody will be developed against the hormone leptin, which will allow estimate of total body fat from a drop of blood.
To test the hypothesis that leptin levels and whole-body lipid stores are correlated in M. salmoides. Effects of age, sex, body weight, environmental temperature, nutritional status and circadian cycle on leptin concentrations will be measured.

A non-destructive chemical assay will be developed to estimate total body fat in largemouth bass. Whole body fat stores are positively correlated with overwinter survival in this species, however current methods to measure fat stores destroy the fish. In humans, whole-body fat store are correlated with a circulating hormone called leptin. The P.I. proposes to develop an antibody against the hormone leptin from fish. This antibody will be the basis of determining the fat content of a living largemouth bass from only a small blood sample. Fish leptin titer will then be tested in response to age, sex, nutritional status, and response to temperature.

The largemouth bass (Micropterus salmoides) fishery is one of the most popular recreational fisheries in Ohio, with over 185000 fish landed and over 40 public tournaments annually. Efforts to enhance this fishery through stocking of juveniles by Ohio Division of Wildlife Hatcheries has all but ceased, due to severe juvenile overwintering mortality. Overwintering mortality in M. salmoides (as high as 87%) seems to be a function of both fish size and lipid stores. In examining the role of lipid stores in overwintering mortality, researchers must destroy the fish to assay whole-body lipid organic extraction, visual inspection, or bomb calorimetry. Therefore potentially crucial data (such as repeated measurements on an individual through the overwintering period) are unavailable with current techniques. I propose that an antibody against largemouth bass leptin, a hormone indicative of whole-body fat stores in mammals, would provide a non-destructive measure of fat stores. Using this probe, researchers could measure whole-body lipid literally from a drop of blood, and thus track individual lipid stores across seasons.

Commercial antibodies against mouse leptin will be tested against fish tissues. Immunoreactive proteins will be isolated (by gel permeation, ion-exchange, two-dimensional electrophoresis, and peptide sequencing) to determine amino acid sequence of fish leptin. This sequence will be used to generate molecular probes, which will be used to screen fish cDNA libraries. cDNA libraries will also be screened with the anti-mouse-leptin antibody.

The existence of leptin in fish and lizards has been established (see publications). The effects of murine (mouse) leptin on fish metabolism has been studied (fat metabolism is specifically up-regulated). A positive correlation between leptin titer in the brain and whole-body fat stores has been documented. Research profiled on The Learning Channel (October, 1998) on a program entitled "Amazing Science".