MORPHOLOGICAL DEFORMATION IN PRESERVED SPECIMENS OF THE DEEP-SEA OCTOPUS GRANELEDONE

Abstract

Although morphology of firm-bodied shallow-water octopuses resists preservation-linked deformation, preservation and handling of deep-sea specimens of Graneledone are hypothesized to deform specimens by accelerating fluid loss from mantle and arm tissues. Principal components analysis finds that seven of 39 North Pacific specimens of the genus are exceptionally narrow; the remaining specimens show considerable morphological variation, independent of time in preservation. Five exceptionally narrow specimens, including some paratypes of G. pacifica, were collected and preserved by the same trawling study; a single unrecorded factor in their common preservation history may have caused their deformation. The high morphological variation among the remaining specimens, seemingly unique among octopodids, may reflect factors as subtle as how the specimen was stored in the jar. Two types of change with time in preservation are documented. The mantle wall of formalin-fixed specimens thins unpredictably after storage for 30 months in 70% ethanol, consistent with deformation in preservation. Skin tubercles on the dorsal mantle, important taxonomic characters, become more prominent during the first decade in preservation. To maximize the information specimens with fluid-rich tissues convey and to identify the sources of deformation, the full preservation history and measurements made prior to dissection should be permanently recorded.