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Population structure of Abyssorchomene abyssorum () (Amphipoda: Lysianassoidea), a scavenging amphipod from the Mid-Atlantic Ridge in the vicinity of the Charlie-Gibbs Fracture Zone

Population structure of Abyssorchomene abyssorum () (Amphipoda: Lysianassoidea), a scavenging amphipod from the Mid-Atlantic Ridge in the vicinity of the Charlie-Gibbs Fracture Zone
Population structure of Abyssorchomene abyssorum () (Amphipoda: Lysianassoidea), a scavenging amphipod from the Mid-Atlantic Ridge in the vicinity of the Charlie-Gibbs Fracture Zone
This study focussed on the common and ubiquitous scavenging amphipod Abyssorchomene abyssorum collected from a section of the Mid-Atlantic Ridge with one pair of sampling areas at 49°N and the other at 54°N, north and south of the Charlie Gibbs Fracture Zone (CGFZ) and east and west of the ridge, at a water depth of 2500 m. Baited-trap samples of necrophagous amphipods were collected during three research expeditions on the RRS James Cook in 2007, 2009, and 2010, allowing for direct comparisons to be made amongst populations of A. abyssorum at the four sample areas. Random subsamples of 200 individuals from nine trap samples were sexed, dissected, and measured.

Males, females, and juveniles were found in all samples but no ovigerous females were identified. The finding of sexually mature mid-sized females, variability of oocyte size with body size, and presence of mature females with ‘empty’ ovaries, suggest that A. abyssorum is capable of having multiple broods in a lifetime. This reproductive strategy is beneficial to a scavenging organism living under a variable and unpredictable nutrient regime, allowing for a rapid reproductive response to advantageous conditions. Females north and south of the CGFZ fall into distinct cohorts with different distributional parameters. The total body lengths of female cohorts south of the CGFZ were consistently larger than those in the north. This is likely due to increased nutrient availability at the southern sampling areas.

Males were significantly smaller than females and possessed longer, more articulate antennae. Longer antennae are thought to facilitate mate-searching by males. Estimates of the maximum brood size ranged from 36–78 offspring with actual brood size expected to be at the lower end of this scale. This places the estimated brood size of A. abyssorum in a similar range to that of other scavenging amphipods of comparable size. The juvenile:non-juvenile ratio differed north and south of the CGFZ with significantly more juveniles in the north. Possible reasons for this difference are discussed.
Amphipoda, Mid-Atlantic Ridge, Population ecology, Scavengers, Bathyal
0967-0645
360-369
Duffy, Grant A.
e040b78b-5516-46b3-899a-4a275d91f134
Horton, Tammy
c4b41665-f0bc-4f0f-a7af-b2b9afc02e34
Sheader, Martin
4d124355-7755-4eaa-97de-8512b4e8a0fa
Thurston, Michael H.
f23a596e-f311-4ca9-87d5-c1c56730eb19
Duffy, Grant A.
e040b78b-5516-46b3-899a-4a275d91f134
Horton, Tammy
c4b41665-f0bc-4f0f-a7af-b2b9afc02e34
Sheader, Martin
4d124355-7755-4eaa-97de-8512b4e8a0fa
Thurston, Michael H.
f23a596e-f311-4ca9-87d5-c1c56730eb19

Duffy, Grant A., Horton, Tammy, Sheader, Martin and Thurston, Michael H. (2013) Population structure of Abyssorchomene abyssorum () (Amphipoda: Lysianassoidea), a scavenging amphipod from the Mid-Atlantic Ridge in the vicinity of the Charlie-Gibbs Fracture Zone. Deep Sea Research Part II: Topical Studies in Oceanography, 98, 360-369. (doi:10.1016/j.dsr2.2013.02.004).

Record type: Article

Abstract

This study focussed on the common and ubiquitous scavenging amphipod Abyssorchomene abyssorum collected from a section of the Mid-Atlantic Ridge with one pair of sampling areas at 49°N and the other at 54°N, north and south of the Charlie Gibbs Fracture Zone (CGFZ) and east and west of the ridge, at a water depth of 2500 m. Baited-trap samples of necrophagous amphipods were collected during three research expeditions on the RRS James Cook in 2007, 2009, and 2010, allowing for direct comparisons to be made amongst populations of A. abyssorum at the four sample areas. Random subsamples of 200 individuals from nine trap samples were sexed, dissected, and measured.

Males, females, and juveniles were found in all samples but no ovigerous females were identified. The finding of sexually mature mid-sized females, variability of oocyte size with body size, and presence of mature females with ‘empty’ ovaries, suggest that A. abyssorum is capable of having multiple broods in a lifetime. This reproductive strategy is beneficial to a scavenging organism living under a variable and unpredictable nutrient regime, allowing for a rapid reproductive response to advantageous conditions. Females north and south of the CGFZ fall into distinct cohorts with different distributional parameters. The total body lengths of female cohorts south of the CGFZ were consistently larger than those in the north. This is likely due to increased nutrient availability at the southern sampling areas.

Males were significantly smaller than females and possessed longer, more articulate antennae. Longer antennae are thought to facilitate mate-searching by males. Estimates of the maximum brood size ranged from 36–78 offspring with actual brood size expected to be at the lower end of this scale. This places the estimated brood size of A. abyssorum in a similar range to that of other scavenging amphipods of comparable size. The juvenile:non-juvenile ratio differed north and south of the CGFZ with significantly more juveniles in the north. Possible reasons for this difference are discussed.

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More information

Published date: 15 December 2013
Keywords: Amphipoda, Mid-Atlantic Ridge, Population ecology, Scavengers, Bathyal
Organisations: Ocean and Earth Science, Marine Biogeochemistry

Identifiers

Local EPrints ID: 360974
URI: http://eprints.soton.ac.uk/id/eprint/360974
ISSN: 0967-0645
PURE UUID: 758a6b3c-3072-481d-899b-1a1869e9e0be

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Date deposited: 08 Jan 2014 13:37
Last modified: 08 Jan 2022 09:12

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Contributors

Author: Grant A. Duffy
Author: Tammy Horton
Author: Martin Sheader
Author: Michael H. Thurston

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