Shell color polymorphism in the marine gastropod Mitrella fusiformis

Gastropod mollusks are extremely important in marine ecosystems as predators and prey, especially in coral reefs. It is important to understand where and how these benthic organisms interact with their communities and with the physical aspects of their ecosystems. Our project is to study polymorphism among shallow water columbellids, a common and diverse family of marine neogastropod snail. Columbellids are small (most are less than 10 mm in length) and can be very common epibenthic carnivores in shallow marine systems. A number of nearshore species in this group are polymorphic for shell color and pattern, a factor that may correlate to their individual survival by making them more or less visible to predators and prey. Our objective is to investigate correlations between polymorphism, environment and sex in common local epibenthic marine gastropods. This study will focus on Mitrella fusiformis (Pease, 1868), one of the most common local columbellid species. Last year, we determined that there were trends for different morphs on the leeward and windward sides of Hawaii Island but our sample size was not large enough to show statistical significance. Thus, this year our project focuses on increasing sample size to better elucidate trends. In addition, further emphasis will be placed on collecting environmental data with the hopes of correlating environmental factors with certain polymorphisms. Common environmental factors to be recorded are salinity, temperature, food source and habitat. To study these organisms, we will make collections in several locations around the Island of Hawai‘i, where they are found typically in 1m depth or less. Individual adult animals will be sexed, measured, and their shell color and pattern documented photographically using a dissecting stereomicroscope with camera. Most animals will be returned alive to their original habitat after data are collected. The resulting data set will allow us to investigate correlations between shell color and pattern, and factors including sex, substrate habitat, salinity, and location. The hope is to gain more insight into how these organisms interact with their habitats in our Hawaiian waters.

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