Meeting Abstract

29.4  Friday, Jan. 4  Endosymbiosis in an Anchialine Crustacean PAKES, M. J. *; MEJíA-ORTIZ, L. M. ; WEISS, A.; CALDWELL, R. L.; University of California, Berkeley; University of Quintana Roo, Cozumel; University of California Berkeley; University of California, Berkeley pakes@berkeley.edu

Sulfidic marine habitats, such as the benthic intertidal and hydrothermal vents, are widespread. Fauna in these ecosystems have developed many physiological and morphological adaptations to cope with the depleted oxygen and toxic sulfide levels typical of such habitats. In addition, many invertebrates, such as mollusks, have evolved epi- and endosymbioses with chemosynthetic bacteria for host nutritional benefit. Surpisingly, only epibiotic chemosymbionts have been described in members of the Crustacea. Here, we present the first findings of chemosynthetic endosymbiosis in the Crustacea, as exhibited in Typhlatya pearsi (Atyidae; Malacostraca), a shrimp endemic to anchialine caves. In these karst systems, marine layer flows beneath one or more layers of less saline water and water exchange with nearby oceans is severely restricted, creating stable physico-chemical gradients often characterized by anoxia and high sulfide levels. Transmission Electron Microscopy (TEM) of cave shrimp have revealed numerous and likely symbiotic gram-negative bacteria found in specialized bacteriocytes. In addition, Scanning Electron Micrographs (SEM) suggest that Remipedia (Speleonectes tulumensis), a class of Crustacea endemic to anchialine systems, as well as T. pearsi are also colonized by epibiotic bacteria. TEM analyses of both taxa have also reveal morphological adaptations typical of hosts containing sulfide oxiding symbionts, such as clustered mitochondria in epithelial cells surrounding sulfide oxidizing bodies. Stable isotope analyses further support chemosymbiotic food sources in these crustaceans. These data suggest that a greater phylogenetic diversity of hosts and more ecosystem types support intracellular chemosynthetic mutualisms than we previously thought.