Abstract
Infection of fish eggs by oomycete watermolds has been documented among numerous fish species occupying diverse aquatic habitats. In fact, watermolds are considered to be ubiquitous in freshwater systems and it seems that all species of fish eggs are susceptible to infection. Oomycete infection can result in the loss of large numbers of viable eggs because it can quickly spread from one infected egg to many others. To date, the majority of studies have been conducted using salmonid eggs under artificial rearing conditions, and there has been virtually no research on reproductive ecology or parental care behavior in fish as it relates to watermold infection. Additionally, few studies have utilized microscopy to elucidate the causes or pathways of infection. My research project had two major objectives. First, I looked at two aspects of convict cichlid (Archocentrus nigrofasciatus) behavior, fanning and egg cleaning, in an attempt to quantify the individual and collective effectiveness of each behavior in preventing the spread of infection within a clutch of eggs. Effectiveness was evaluated by comparing egg mortality under different care regimes. Second, I used microscopy and histology techniques to look at and pictorially document modes of egg infection and spatial patterns of egg mortality. My evaluations of parental care effects on watermold infection did not yield any statistically significant differences between treatments, possibly due to unforeseen design flaws and inadequately controlled variables. I discuss these flaws and offer suggestions for additional research that will provide a reference for future studies on this important topic. Additionally, egg samples were evaluated using a variety of histologic and microscopic techniques, including scanning electron microscopy, mortal staining, and paraffin sectioning in an attempt to elucidate the oomycete’s modes of infection and spread. I present the results of this study as a photographic atlas, which may lead to a better understanding of this phenomenon and suggest alternative methods for control. Although the results of my study do not provide definitive approaches toward controlling oomycete infection, they do contribute to the limited body of information on the incidence of watermold infection in fish eggs.