Effects of fixation and long-term preservation on finned octopods (Cephalopoda: Cirrata)

Abstract

Among mollusks, the octopods stand out due to the almost entire absence of a stabilizing shell, potentially rendering these organisms susceptible to deformation caused by fixation and preservation. Such artifacts have previously been shown to occur especially in specimens of the deep-sea taxon Cirrata, the finned octopods. As an adaptation to their extreme habitat, many cirrates are composed of (semi-)gelatinous tissues, which are particularly prone to distortion, shrinkage, and deformation following fixation and preservation. Using one or more species from each of the eight currently recognized cirrate genera, the present study provides pre- and post-fixation color imagery of entire specimens as well as measurements of taxonomically relevant characters. These novel data illustrate the sometimes drastic effects that short- and long-term chemical treatment entails for this cephalopod taxon. Both structural and color changes may occur when finned octopods are fixed and preserved using routine protocols. However, shrinkage does not occur uniformly in all taxonomically relevant structures. The consequences of such a treatment for species descriptions and identification are discussed and existing anaesthetization, fixation and preservation protocols are summarized.