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Abraliopsis gilchristi (Robson 1924)

Richard E. Young and Kotaro Tsuchiya
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Containing group: Abraliopsis (Micrabralia)

Introduction

A. gilchristi is one of the most easily recognized species of Abraliopsis. Males reach at least 39 mm ML and, presumably, females reach a bit larger size. It occupies temperate waters of the southern hemisphere.

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Figure. Ventral view of Abraliopsis gilchristi.Drawing from Voss (1967, Pl. Ia).

Brief diagnosis:

A species of Abraliopsis with ...

Characteristics

  1. Tentacle clubs
    1. Largest hooks of ventral series on manus about 3X height of dorsal counterparts.
    2. Carpal flap and aboral keel, large.
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      Click on an image to view larger version & data in a new window

      Figure. Oral view of the tentacular club of A. gilchristi, South African waters.Drawing from Voss (1967, Pl. IIa).

  2. Arms
    1. Arms I-IV with 17 - 28 hooks; only arms I-III with distal suckers.
    2. Arms IV relatively short; ALI IV = 40-65.
    3. Females: Trabeculate protective membranes virtually absent from dorsal margins of arms I-III and absent from both margins of arms IV; trabeculate protective membranes well developed in ventral margins of arms I-III. Tubercules absent from trabeculae and arms.
  3. Hectocotylus and male sexual dimorphism
    1. Hectocotylus with long ventral flap and shorter, offset dorsal flap; Modified portion with armature. 
    2. Hectocotylus hooks about equal size on both margins proximally; in mid-arm hooks of ventral margin abruptly smaller to end of arm.
    3. Spatulate trabeculae on the protective membrane of left arm IV; proximally, hooks are larger than their ventral counterparts.
    4. Arms I: dorsal border with small lappets; ventral border with large membrane bearing long, broad trabeculae; tubercules present on arm base.
    5. Arms II: dorsal margin with short trabeculae bearing tubercules but membrane nearly absent; ventral margin with enlarged membrane and long, flat trabeculae, both trabeculae and membrane with tubercules.
    6. Arms III: dorsal margin with lappets only; ventral margin with narrow trabeculae and deep membrane but without papillae.
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window

      Figure. Dorso-oral views of arms I and II of A. gilchristi, Male, 32 mm ML. Photographs by R. Young.

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      Click on an image to view larger version & data in a new window

      Figure. Left - Oral view of some arms of A. gilchristi, including the hectocotylized right arm IV. Drawing from Voss (1967, Pl. IIIa-d). Right - Two slightly different oral views of the same modified end of the hectocotylus showing the long, ventral flap and the short dorsal flap.

  4. Photophores
    1. Ocular photophores: 5 photophores with end members about 2X larger than middle member.
    2. Integumental photophores: Ventral-most head with 4 series of photophores. Mantle with scattered photophores.
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      Click on an image to view larger version & data in a new window

      Figure. Ventral views of the integumental photophores of A. gilchristi, female, 32 mm ML, South Atlantic. Left - Photograph of the preserved squid. Right - Outline drawing with all integumental photophores represented by colored dots.  Red dots - Complex photophores. Blue dots - Non-complex photophores. Images by R. Young.

      Detailed information on the integumental photophores can be found here.

  5. Measurements and counts
    Sex
    Male
    Male
    Female
    Mantle length 
    34
    37.5
    38
    Head width index
    29.4
    32.3
    -
    Fin length index
    82.4
    82.7
    81.6
    Fin width index
    91.2
    89.6
    81.6
    Arm Length index:
    I
    61.8 53.3
    43.4
    II
    50
    53.3
    50
    III
    60.3
    53.3
    52.6
    IV
    76.5
    74.6
    76.3
    No. arm hooks:
    I
    17
    17
    17
    II
    17
    19
    20
    III
    21
    20
    19
    IV
    23
    28
    23+
    Club length index (R/L)
     -  - 26.3
    Table data taken from Voss (1967).

Comments.

Most of the above description is from Voss (1967).

Note that the arm features of the male are very similar to those of the subgenus Pfefferiteuthis. Also note that the scattered arrangement of red photophores on the mantle and some areas of the head are very similar to arrangements in members of the subgenus Abraliopsis.

See Abraliopsis (Micrabralia) page for comparisons among all species of the subgenus.

Life history

Abundance

Alexeyev (1994) reported the highest abundance and frequency of this species between 40° - 45° S in central southern Pacific.

Maturation

In the central South Pacific, the squids caught in April of 1987 were all immature. In July, stage I of maturity was already absent, while individuals at III and IV stages made up 86% of females and 87% of males. In September, the majority of squids were mature or spent (Alexeyev, 1994).

Feeding habitat

This species feeds on crustaceans, mainly copepods, and to a lesser extent on euphausiids and hyperiids (Alexeyev, 1994).

Distribution

Geographical Distribution

A. gilchristi is distributed in circum-southern temperate waters between 20° - 45° S, but is not known from the southern coast of Australia (Riddell, 1985; Alexeyev, 1994). This species is abundant at the southern border of the Subantarctic frontal zone in the central South Pacific (Alexeyev, 1994) Alexeyev classified this as "peripheral notalian species"

References

Alexeyev, D.O. 1994. New data on the distribution and biology of squids from the southern Pacific. Ruthenica, 4:151-166.

Riddell, D.J. 1985. The Enoploteuthidae (Cephalopoda: Oegopsida) of the New Zealand region. Fisheries Reserch Bulletin (NZ), 27:1-52.

Voss, G.L. 1967. Some bathypelagic cephalopods from South African waters. Annals of the South African Museum, 50(5):61-88

Title Illustrations
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Click on an image to view larger version & data in a new window
Scientific Name Abraliopsis gilchristi
Specimen Condition Preserved
Identified By R. E. Young
Sex Female
View Ventral
Size 32 mm ML
Collection USNM 884908
Image Use creative commons This media file is licensed under the Creative Commons Attribution License - Version 3.0.
Copyright ©
About This Page


University of Hawaii, Honolulu, HI, USA


Tokyo University of Fisheries, Tokyo, Japan

Correspondence regarding this page should be directed to Richard E. Young at

Page: Tree of Life Abraliopsis gilchristi (Robson 1924). Authored by Richard E. Young and Kotaro Tsuchiya. The TEXT of this page is licensed under the Creative Commons Attribution-NonCommercial License - Version 3.0. Note that images and other media featured on this page are each governed by their own license, and they may or may not be available for reuse. Click on an image or a media link to access the media data window, which provides the relevant licensing information. For the general terms and conditions of ToL material reuse and redistribution, please see the Tree of Life Copyright Policies.

Citing this page:

Young, Richard E. and Kotaro Tsuchiya. 2013. Abraliopsis gilchristi (Robson 1924). Version 03 November 2013 (under construction). http://tolweb.org/Abraliopsis_gilchristi/19687/2013.11.03 in The Tree of Life Web Project, http://tolweb.org/

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