Habitat Preference of the Daggerblade Grass Shrimp Palaemonetes pugio and Whether Field Preference is Correlated with the Trematode Parasite Microphallus turgidus

Abstract

Daggerblade grass shrimp Palaemonetes pugio reside in brackish estuarine systems and are thus exposed to the parasitic trematode Microphallus turgidus. The purpose of this study was to determine if the infection of P. pugio by M. turgidus was different across months and between two sites near Savannah, GA, and to determine habitat preference of infected P. pugio between the invasive red alga Gracilaria vermiculophylla and substrate-free open space in the laboratory. Trematode density was significantly higher in October-December 2016 and February 2017 (11.0-13.3) at one site and was significantly higher December 2016-January 2017 (10.1-10.3) and August-October 2017 (10.8-12.6) at the other site. In the laboratory, 76% of shrimp preferred tank edge locations whereas only 20% preferred G. vermiculophylla. Only 4% consistently selected the substrate-free open space. A wide range of factors such as food availability, presence of predators, interspecies competition, and abiotic conditions perhaps influence changes in parasite density and habitat preference.