Size-dependent change in body shape and its possible ecological role in the Patagonian squid (Doryteuthis gahi) in the Southwest Atlantic

Jessica B Jones (Corresponding Author), Graham J Pierce, Fran Saborido-Rey , Paul Brickle, Frithjof C Kuepper, Zhanna N. Shcherbich, Alexander I. Arkhipkin

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Cephalopods are a versatile group with several mechanisms in place to ensure the success of future generations. The Patagonian long-finned squid (Doryteuthis gahi) populations on the southern Patagonian shelf are believed to be genetically homogenous, but the mechanisms connecting them geographically and temporally are unresolved. Individual growth is highly variable within cephalopod populations and is likely to affect individual patterns of migration and, thus, population connectivity as a whole. Therefore, this study aimed to make inferences about population structure by analysing the size at which individuals were mature and aimed to describe the intrapopulation growth (allometric) trajectories of body shape, using landmark-based geometric morphometric techniques to describe phenotypes. Samples were collected from June 1999 to November 2017 around 52°S and 58°W. Smoothing curves from binomial generalised additive models (GAMs) suggested two size modes of maturity in females and one or multiple modes in males dependent on year and season. There was a gradual elongation of the mantle and an increase in the relative fin size throughout ontogeny. Shape scores from geometric morphometric shape coordinates revealed a continuous non-linear allometric trajectory with a significantly different slope angle for males exceeding 20.1 cm dorsal mantle length (DML). At the extreme of this continuum, the largest ‘super-bull’ form had a substantially more elongated body shape, a heavier fin and a larger fin area compared to the rest of the population, a body shape associated with enhanced swimming performance which may help to maintain population connectivity. The prevalence of these rare super-bulls in the fishery varied widely between years, suggestive of phenotypic plasticity. This study provides evidence that the D. gahi population on the southern Patagonian shelf has a complex population structure with high intraspecific variation.
Original languageEnglish
Article number54
JournalMarine Biology
Volume166
Early online date23 Mar 2019
DOIs
Publication statusPublished - May 2019

Fingerprint

animal morphology
body shape
squid
cephalopod
population structure
connectivity
trajectory
mantle
fins
slope angle
intraspecific variation
phenotypic plasticity
Cephalopoda
ontogeny
smoothing
trajectories
phenotype
bulls
fishery
fisheries

Keywords

  • BEAK SHAPE
  • CEPHALOPODA LOLIGINIDAE
  • FALKLAND ISLANDS
  • GEOMETRIC MORPHOMETRICS
  • LIFE-HISTORY
  • LOLIGO-VULGARIS-REYNAUDII
  • MATING SYSTEM
  • ONTOGENIC MIGRATIONS
  • POPULATION-STRUCTURE
  • REPRODUCTIVE STRATEGIES

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Ecology

Cite this

Size-dependent change in body shape and its possible ecological role in the Patagonian squid (Doryteuthis gahi) in the Southwest Atlantic. / Jones, Jessica B (Corresponding Author); Pierce, Graham J; Saborido-Rey , Fran ; Brickle, Paul; Kuepper, Frithjof C; Shcherbich, Zhanna N.; Arkhipkin, Alexander I.

In: Marine Biology, Vol. 166, 54, 05.2019.

Research output: Contribution to journalArticle

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abstract = "Cephalopods are a versatile group with several mechanisms in place to ensure the success of future generations. The Patagonian long-finned squid (Doryteuthis gahi) populations on the southern Patagonian shelf are believed to be genetically homogenous, but the mechanisms connecting them geographically and temporally are unresolved. Individual growth is highly variable within cephalopod populations and is likely to affect individual patterns of migration and, thus, population connectivity as a whole. Therefore, this study aimed to make inferences about population structure by analysing the size at which individuals were mature and aimed to describe the intrapopulation growth (allometric) trajectories of body shape, using landmark-based geometric morphometric techniques to describe phenotypes. Samples were collected from June 1999 to November 2017 around 52°S and 58°W. Smoothing curves from binomial generalised additive models (GAMs) suggested two size modes of maturity in females and one or multiple modes in males dependent on year and season. There was a gradual elongation of the mantle and an increase in the relative fin size throughout ontogeny. Shape scores from geometric morphometric shape coordinates revealed a continuous non-linear allometric trajectory with a significantly different slope angle for males exceeding 20.1 cm dorsal mantle length (DML). At the extreme of this continuum, the largest ‘super-bull’ form had a substantially more elongated body shape, a heavier fin and a larger fin area compared to the rest of the population, a body shape associated with enhanced swimming performance which may help to maintain population connectivity. The prevalence of these rare super-bulls in the fishery varied widely between years, suggestive of phenotypic plasticity. This study provides evidence that the D. gahi population on the southern Patagonian shelf has a complex population structure with high intraspecific variation.",
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KW - ONTOGENIC MIGRATIONS

KW - POPULATION-STRUCTURE

KW - REPRODUCTIVE STRATEGIES

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