Duration of pseudo-stalked barnacles ( Xenobalanus globicipitis ) on a New Zealand Pelagic ecotype orca ( Orcinus orca ), with comments on cookie cutter shark bite marks ( Isistius sp.); can they be used as biological tags?

摘要

This is the first published report of a New Zealand Pelagic ecotype orca (Orcinus orca Linnaeus, 1758, killer whale, Mammalia Cetacea) as a host for the pseudo-stalked barnacle (Xenobalanus globicipitis Steenstrup, 1852, Crustacea Coronulidae). The barnacles were documented on an adult female and she hosted 79, 3.5 times higher than any other orca worldwide. They were distributed on her dorsal fin (n=3), pectoral fins (n=36) and tail flukes (n=40), with a higher density on her right appendages (n=48) compared to her left (n=28). We also document, for the first time, the longevity of X. globicipitis hosted on an orca, with a minimum duration of 36 days. We provide a global overview of the distribution of X. globicipitis on orca, based on historic and recent publications. In previous reviews (spanning 111 years of records) X. globicipitis were documented in ten regions, while we add ten more regions, in just 13 years. This leads us to speculate as to the causes of this rapid increase, which may be linked to observer bias, improved research tools, a change in the distribution of either O. orca or X. globicipitis, with distribution of the latter perhaps influenced by oceanic conditions such as marine heatwaves and acidification triggered by climate change. As such, we discuss if either pseudo-stalked barnacles (or bite marks from cookie cutter sharks, Isistius sp., Chondrichthyes Squaliformes) can be used as biological tags or markers for orca ecotypes. We recommend separate management plans for orca ecotypes.