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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Mar. Sci. | doi: 10.3389/fmars.2019.00709

Phenotypic plasticity or a reproductive dead end? Primnoa pacifica (Cnidaria: Alcyonacea) in the Southeastern Alaska region.

  • 1University of Gothenburg, Sweden
  • 2University of Maine, United States
  • 3Alaska Fisheries Science Center (NOAA), United States
  • 4Oregon Institute of Marine Biology, University of Oregon, United States
  • 5University of Alaska Fairbanks, United States
  • 6United States Geological Survey (USGS), United States

Red tree corals (Primnoa pacifica) are abundant in the eastern Gulf of Alaska, from the glacial fjords of Southeast Alaska where they emerge to as shallow as 6 m, to the continental shelf edge and seamounts where they are more commonly found at depths greater than 150 m. This keystone species forms large thickets, creating habitat for many associated species, including economically valuable fishes and crabs, and so are important benthic suspension feeders in this region. Though the reproductive periodicity over 1.5 year period was reported in 2014 from a shallow fjord (Tracy Arm), this study examined reproductive ecologies from 8 sites – two within Glacier Bay National Park and Preserve, three on the continental shelf edge, one within Endicott Arm (Holkham Bay) and two time points from the Tracy Arm (Holkham Bay) study. Male reproductive traits were similar at all sites but there were distinct differences in oogenesis. Though fecundity mostly showed no significant difference between sites, there was a trend of increasing number of eggs with depth. Indeed, the average oocyte sizes from Tracy Arm (the shallowest site) was 105 m, whereas from Shutter Ridge (one of the deepest sites) the average size was 309 m. Moreover, the maximum oocyte size at Tracy Arm was 802 m, whereas it was 2120 m at Dixon Entrance, an almost 3-fold difference, and one not usually observed within a single species. We propose two theories to explain the observed differences, a) this species shows great phenotypic plasticity in reproductive ecology, adjusting to different environmental variables based on energetic need and potentially demonstrating micro-evolution; or b) the fjord sites are at a reproductive dead end, with the stress of shallow water conditions effectively preventing gametogenesis reaching full potential and likely limiting successful reproductive events from occurring, at least on a regular basis.

Keywords: poecilogeny, octocoral reproduction, oocyte sizes, Deep-sea corals, deep-water emerged, , glacial fjords, Primnoidae

Received: 13 Jun 2019; Accepted: 04 Nov 2019.

Copyright: © 2019 Waller, Stone, Rice, Johnstone, Rossin, Hartill, Feehan and Morrison. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Rhian G. Waller, University of Gothenburg, Gothenburg, Sweden, rhian.waller@maine.edu