Effects of the nemertean egg predator Carcinonemertes carcinophila (Carcinonemertidae: Monostilifera) on the reproductive output and fecundity of the Florida Atlantic blue crab Callinectes sapidus.

Abstract

The blue crab, Callinectes sapidus, is an important crab fishery in Florida, valued at approximately $14.5 M in 2023. However, female blue crabs are host to the nemertean worm Carcinonemertes carcinophila, which preys upon its eggs. Other nemerteans from this genus have been linked to the collapse of fisheries, such as the Dungeness crab fishery in the 1960s and 1970s and the red king crab fishery in the 1980s. In 2022, the newly-discovered nemertean Carcinonemertes conanobrieni was found to parasitize the egg masses of female Caribbean spiny lobsters, Panulirus argus, and has had drastic impacts on the reproductive output and fecundity of this species. We hypothesized that nemertean egg parasites might have similar impacts on blue crabs. To investigate this, we collected 52 ovigerous female blue crabs from Jacksonville and Ormond Beach, 61.5% of which were infested with C. carcinophila. Infestation status did not significantly affect fecundity or reproductive output; instead, body mass and embryo stage were the strongest predictors. Infestation was more prevalent in crabs with late-stage embryos, consistent with nemertean life cycle timing. While most hosts carried few worms, a subset showed high infestation intensity, and both infestation status and nemertean density were significant predictors of embryo loss. This is a positive sign for the Florida blue crab fishery, as it suggests that the blue crab nemertean might not be as impactful to that fishery as others.