Havenhand Jon N.

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Havenhand
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Jon N.
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  • Article
    Evidence for biased use of sperm sources in wild female giant cuttlefish (Sepia apama)
    (Royal Society, 2005-05-22) Naud, Marie-Jose ; Shaw, Paul W. ; Hanlon, Roger T. ; Havenhand, Jon N.
    In species where females store sperm from their mates prior to fertilization, sperm competition is particularly probable. Female Sepia apama are polyandrous and have access to sperm from packages (spermatangia) deposited by males onto their buccal area during mating and to sperm stored in internal sperm-storage organs (receptacles) located below the beak. Here, we describe the structure of the sperm stores in the female's buccal area, use microsatellite DNA analyses to determine the genetic diversity of stored sperm and combine these data with offspring genotypes to determine the storage location of paternal sperm. The number of male genotypes represented in the sperm receptacles was significantly lower than that found among the spermatangia. Estimation of the volumes of sperm contained in the receptacles and the spermatangia were statistically comparable; however, paternal sperm were more likely to have come from spermatangia than from the sperm receptacles. These results confirm a genetic polyandrous mating system in this species and suggest that fertilization pattern with respect to the sperm stores used is not random.
  • Article
    Climate change and the threat of novel marine predators in Antarctica
    (John Wiley & Sons, 2017-11-30) Smith, Kathryn E. ; Aronson, Richard B. ; Steffel, Brittan V. ; Amsler, Margaret O. ; Thatje, Sven ; Singh, Hanumant ; Anderson, Jeff ; Brothers, Cecilia ; Brown, Alastair ; Ellis, Daniel S. ; Havenhand, Jon N. ; James, William R. ; Moksnes, Per-Olav ; Randolph, Allison W. ; Sayre-McCord, Thomas ; McClintock, James B.
    Historically low temperatures have severely limited skeleton-breaking predation on the Antarctic shelf, facilitating the evolution of a benthic fauna poorly defended against durophagy. Now, rapid warming of the Southern Ocean is restructuring Antarctic marine ecosystems as conditions become favorable for range expansions. Populations of the lithodid crab Paralomis birsteini currently inhabit some areas of the continental slope off Antarctica. They could potentially expand along the slope and upward to the outer continental shelf, where temperatures are no longer prohibitively low. We identified two sites inhabited by different densities of lithodids in the slope environment along the western Antarctic Peninsula. Analysis of the gut contents of P. birsteini trapped on the slope revealed them to be opportunistic invertivores. The abundances of three commonly eaten, eurybathic taxa—ophiuroids, echinoids, and gastropods—were negatively associated with P. birsteini off Marguerite Bay, where lithodid densities averaged 4280 ind/km2 at depths of 1100–1499 m (range 3440–5010 ind/km2), but not off Anvers Island, where lithodid densities were lower, averaging 2060 ind/km2 at these depths (range 660–3270 ind/km2). Higher abundances of lithodids appear to exert a negative effect on invertebrate distribution on the slope. Lateral or vertical range expansions of P. birsteini at sufficient densities could substantially reduce populations of their benthic prey off Antarctica, potentially exacerbating the direct impacts of rising temperatures on the distribution and diversity of the contemporary shelf benthos.