Along an expanding range: Parasitism and reproduction in the non-native green porcelain crab (Petrolisthes armatus) from Florida to North Carolina

Abstract

Climate-driven biological invasions and range expansions of marine and estuarine species are increasing in rate and frequency globally with rising ocean and sea surface temperatures. Species historically found at lower latitudes have migrated poleward to exploit increasingly favorable conditions in temperate regions. This trend is important to investigate as these organisms potentially disrupt recipient environments by altering ecosystem dynamics through novel species interactions (i.e. competition, predation, and parasitism). Along the western Atlantic, the northward movement of subtropical and tropical western Atlantic species up the southeast U.S. coast has been termed the “Caribbean creep”. One representative species of this phenomenon is the green porcelain crab (Petrolisthes armatus), an intertidal and subtidal filter-feeder inhabiting oyster reefs, mangroves, and rocky substrates. My research examined how parasitism by the marine bopyrid Aporobopyrus curtatus and reproductive maturity in P. armatus varied along a latitudinal gradient from the cryptogenic range in the Indian River Lagoon, Florida, to the leading edge of the non-native range in Beaufort, North Carolina. This work represents the first range-wide study of A. curtatus infections in P. armatus in the United States. In 2024 and 2025, a total of 2,164 porcelain crabs were collected via passive samplers and by hand from sites in Florida (n = 5), Georgia (n = 1), South Carolina (n = 1), and North Carolina (n = 3). Upon analyzing patterns of bopyrid infection across the study range, generalized linear mixed models revealed that both individual infection probability and population-level infection prevalence decreased with increasing latitude. These findings are consistent with expectations of the enemy release hypothesis, which suggests that non-native species experience reduced pressure from parasites, pathogens, predators, and competition as they move into novel environments. Upon examining reproductive life history traits in Petrolisthes armatus, modeling showed that probability of ovigery varied with the interaction between body size and latitude, indicating that females at higher latitudes reached reproductive maturity at smaller body sizes. As tropical and subtropical species move into colder temperate environments, they are subjected to physiological stress that may impact their growth, development, and reproductive patterns. Together, these findings improve our understanding of how parasitism and reproductive traits vary across the range of Petrolisthes armatus in the southeast U.S., providing greater insight into the ecological processes that influence the establishment and success of these crabs and other invasive and range-expanding species.