Meeting Abstract

33.7  Sunday, Jan. 5 09:30  Clearly camouflaged: muscle architecture in transparent shrimp BAGGE, L.E.*; KIER, W.M.; JOHNSEN, S.; Duke University; University of North Carolina at Chapel Hill; Duke University leb47@duke.edu

Transparency is a common camouflage strategy for small, thin, or gelatinous animals inhabiting pelagic environments, but is rare among larger species with more complex body plans, especially those inhabiting benthic environments. Nevertheless, many shrimp species in the genus Periclimenes are extraordinarily transparent despite having a relatively large (>10 mm) body size and a benthic, commensal existence with anemones; they are clear enough to read a newspaper through their abdomen. Absence of pigment is insufficient for transparency as their tissues also must not scatter light. Because anemone shrimp are not extremely small or flat, and their tissues cannot be made of one component with one refractive index, we investigated whether other morphological and ultrastructural modifications for transparency were present. We examined the muscle tissue in three transparent species of Periclimenes (P. rathbunae, P. yucatanicus, and P. pedersoni), and in more opaque shrimp species (Thor amboinensis and Lysmata wurdemanni), which share the same ecology and microhabitat. All specimens were collected from anemones near Carrie Bow Cay, Belize. The shrimp were fixed in 2.5% glutaraldehyde, and tissue blocks were dissected from the posterior abdomen and embedded in glycol methacrylate to minimize distortion. Cross-sections of 3-7 μm thickness were cut with a glass knife and stained with Picrosirius Fast Green stain, which allowed for visualization of the arrangement of the muscle fibers. Examination of these sections showed that, at least at light level, the musculature in transparent shrimp is not grossly atypical; therefore, their transparency is likely to be a result of more subtle differences in ultrastructure, which we are investigating with transmission electron microscopy.