Poster Presentation 2024 Australian Marine Sciences Association Annual Meeting combined with NZMSS

Investigating the distinct reproductive strategies of two new species of hadal amphipod (Lyssianassoidea:Uristidae) using micro computed tomography (#631)

Jenny A Wainwright 1 , Johanna NJ Weston 2 , Todd Bond 1 , Alan Jamieson 1
  1. University of Western Australia, Perth, WESTERN AUSTRALIA, Australia
  2. Woods Hole Oceanographic Institute, Boston

Reproductive strategies across hadal (6000 - ~11,000m) organisms are poorly described due to the inability to maintain live animals and observe complete life cycles Amphipods are among the dominant members of the hadal zone. As a function of the preferential use of the baited traps, little is known about their reproduction. Females carry fertilized eggs in external brood pouches until the fully formed juveniles emerge. Brooding females are rarely collected at baited traps as they likely no longer feed to prevent egg expulsion when the mid-gut expands. This study described two new hadal species belonging to the family Uristidae Hurley, 1963 using integrative taxonomy. One Species (1) from the Santa Cruz and San Cristobal trenches (Southwest Pacific Ocean) and Species (2) from the South Sandwich Trench (Southern Ocean). Computed tomography of the brood pouch was applied to investigate the reproductive strategies adopted by these species. Species 1 is characterised by a brood pouch of around 30 small embryos, whereas the brood of Species 2 is characterised by a much smaller clutch of around 5 large embryos. The adaptations to their reproductive strategies are discussed here in line with the oxygen-temperature hypothesis.