Seasonal and gestational variation in the somatic and reproductive condition of females was determined for two east-central Florida populations of the livebearing fish Poecilia latipinna. Females were sampled monthly between January 1985 and January 1986 at Badge Station (BDGST) and Titusville Ditch (TDTCH) study sites. In addition, collections were made at approximately 8 day intervals in April and August. Somatic condition was determined by calculating index values for dry weight (somatic tissue minus water), lipid, and protein from overall regression equations relating these components to female body size. Significant seasonal variation in somatic condition existed within the two study sites. During the winter months, dry weight and the amount of lipid and protein comprising the soma tended to be high. In March and/or April, concurrent with increasing reproductive activity, these values markedly decreased and reached minimum levels in May. Declines in reproduction occurred in June or July as female somatic condition was increasing. These declines were largely expressed as lower percentages of adult females gravid. At both sites, somatic condition continued to increase after the mid-summer minimum and a second reproductive peak occurred in the fall. The relationship between subsequent reproductive declines in the winter and the prevailing somatic condition of females was uncl~ar. Measures of female somatic condition and reproductive activity also differed between the two sites. In January through March, dry weight and lipid index values were higher at TDTCH relative to BDGST. This may explain the earlier onset of reproduction, greater percentage of adult females gravid, and higher size-adjusted fecundity at TDTCH. When the somatic condition of females at both sites deteriorated in May, lipid and protein values at TDTCH were significantly higher. This may be partially responsible for the continued higher size-adjusted fecundity observed there. Following the reproductive slump (June-July), the percentage of adult females gravid was higher through September at BDGST when compared to TDTCH. Reproduction terminated at BDGST during October. Females continued to reproduce into December at TDTCH despite the fact that their somatic condition was significantly lower than BDGST females. Analyses of variation in dry weight, lipid, and protein index values for females at different points in the gestation cycle in April and August produced few clear-cut conclusions. The data suggested that some portion of the soma may be sacrificed during vitellogenesis. In some comparisons, female somatic condition exhibited variation after vitellogenesis was completed. The significance of declines in female energy reserves during gestation was obscured by a lack of knowledge concerning the allocation of energy between the competing processes of maintenance, growth, and reproduction.


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Snelson, Franklin F.


Master of Science (M.S.)


College of Arts and Sciences


Biological Sciences




74 p.




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Arts and Sciences -- Dissertations, Academic; Dissertations, Academic -- Arts and Sciences

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