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Abralia trigonura Berry 1913

Kotaro Tsuchiya and Richard E. Young
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Containing group: Abralia

Introduction

A. trigonura belongs to the Heterabralia subgenus. It is characterized by having two or three hooks on the manus, the left arm hectocotylized, and complex eye photophores. This species resembles A. andamanica but  the latter is separable by its robust tail and dark body color.

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Figure. Photograph of a live A. trigonura in a shipboard aquarium, Hawaiian waters. Photograph by R. Young.

Characteristics

  1. Tentacle clubs
    1. Two or three hooks on ventral side.
    2. Two rows of large suckers on dorsal side of manus.
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    Click on an image to view larger version & data in a new window

    Figure. Oral view of a tentacular club of A. trigonura, Hawaiian waters. Drawing from  Burgess (1991, p. 115, Fig. 1J).

  2. Hectocotylus
    1. Left ventral arm of male hectocotylized.
    2. Hectocotylus with two different sized off-set flaps.
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    Click on an image to view larger version & data in a new window

    Figure. Oral view of the hectocotylus of A. trigonura, Hawaiian waters. Drawing from  Burgess (1991, p. 115, Fig. 1I).

  3. Suckers
    1. Suckers dentate all aroung.
    2. Click on an image to view larger version & data in a new window
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      Figure. Sucker rings of A. trigonura showing dentition. X - Inner sucker ring shelf showing indentation. Drawings from Burgess (1991, p. 115, Fig. 1D, E).

  4. Head
    1. Eye Photophores: Five, complex organs: two large terminal opaque organs and three intermediate silvery organs.
    2. Beaks: Descriptions can be found here: Lower beak; upper beak.

  5. 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. Ocular photophores of A. trigonura. Left - Ventral view. Drawing from Tsuchiya (2000). Right - Postero-ventral view. Photograph by R. Young of a fresh squid with overlying skin removed.

  6. Integumental Photophores
    1. Ventral mantle and head with scattered arrangement of integumental organs.

  7. Mantle apex ("tail")
    1. Broad and extends well beyond conus of gladius.

  8. Reproductive structures
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    Click on an image to view larger version & data in a new window

    Figure. Dorsal view of the receptacle for spermatangia in female A. trigonura. Anterior is left. Left side - Note the nuchal cartilage and collar on either side. Middle - Deep pit that holds the spermatangia. Right - Mantle and gladius folded posteriorly showinng the receptacle located where the mantle and visceral sac fuse. Drawing from Burgess (1991, p. 115, Fig. 1K)

Comments

A. trigonura is similar to A. andamanica, A. siedleckyi, A. heminuchalis, and A. veranyi in its complex ocular photophores and left ventral arm hectocotylization.

Life history

Age and reproduction

Female longevity is up to 6 months, and sexual maturity is reached at 3.5 months. Male longevity is the same as female, and sexual maturity is reached at 2.5 months. The smallest mature female is 31mm DML, and 80% of females are mature at 35mm DML. Males sexually mature between 23-27mm DML. This species seems to be a multiple spawner, and females spawn eggs every few days. Female batch fecundity was roughly 290-430 eggs (Young and Mangold, 1994).

Eggs

Spawned eggs are slightly ovoidal, 0.9 mm x 0.79 mm, usually with a slightly greenish tint, clear, and with a sticky colorless jelly coating (Young and Harman, 1985).

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Figure. Left - "Egg" (actually early embryo) of A. trigonura taken from a plankton tow off Hawaii. The egg is surrounded by a gelationus oviducal secretion with debris attached. Right - Newly hatched paralarva of A. trigonura. Photographs by R. Young.

 Paralarvae

The distinctive chromatophore patterns, especially that of the ventral mantle, can be followed from hatching to the largest paralarva illustrated (5.0 mm ML) where each ventral mantle chromatophore is accompanied by a photophore. That is, the initial chromatophore pattern is duplicated with photophores as the paralarva grows.

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Figure. Ventral and dorsal views of A. trigonura paralarvae. 1.0 mm ML - At hatching. 1.3 mm ML - Seven days after hatching, yolk exhausted. Others - Trawl captured. Drawings from Young and Harman (1985).

Distribution

Vertical Distribution

In the Hawaiian waters, this species was considered to be an important component of the mesopelagic boundary community (Reid et al., 1991), and vertically migrates from upper mesopelagic depths during the day to the upper 50 m at night (Young, 1978). It generally stays during the daytime >5m above the ocean floor (Young, 1995). Young stages occur primarily outside the mesopelagic boundary zone. Adults inhabit the outer mesopelagic boundary zone during daytime, and migrate to the inner mesopelagic boundary zone during night (Young, 1995).

Geographical Distribution

This species is broadly distributed in tropical West to Central North Pacific (Hidaka and Kubodera, 2000).

References

Hidaka, K. and T. Kubodera. 2000. Squids of the genus Abralia (Cephalopoda: Enoploteuthidae) from the western tropical Pacific with a description of Abralia omiae, a new species. Bull. Mar. Sci. 66: 417-443.

Tsuchiya, K. 2000. Illustrated book of the Enoploteuthidae. In: Okutani T., ed. True face of Watasenia scintillans. Tokai University Press, Tokyo, p 196269. (in Japanese)

Young, R.E. 1995. Aspects of the natural history of pelagic cephalopods of the Hawaiian mesopelagic-boundary region. Pacific Science, 49:143-155.

Young, R.E. and Harman, R.F. 1985. Early life history stages of enoploteuthin squids (Cephalopoda: Teuthoidea: Enoploteuthidae) from Hawaiian waters. Vie Milieu, 35:181-201.

Young, R.E. and Mangold, K.M. 1994. Growth and reproduction in the mesopelagic boundary squid Abralia trigonura. Marine Biology, 119: 413-421.

Title Illustrations
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Scientific Name Abralia trigonura
Location Hawaiian waters
Reference Burgess, L.A. 1992. Squids of the genus Abralia (Cephalopoda) from the central equatorial Pacific with a description of Abralia heminuchalis, new species. Bulletin of Marine Science, 49(1-2):113-136.
Acknowledgements Drawing from Burgess (1992, p. 115, Fig. 1A) printed with the Permission of the Bulletin of Marine Science.
Sex Female
View Ventral
Size 41 mm ML
Collection USNM 813116
Copyright © 1992 Bulletin of Marine Science
About This Page
Figures from Burgess (1991) are printed with the Permission of the Bulletin of Marine Science.


Tokyo University of Fisheries, Tokyo, Japan


University of Hawaii, Honolulu, HI, USA

Page: Tree of Life Abralia trigonura Berry 1913. Authored by Kotaro Tsuchiya and Richard E. Young. 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:

Tsuchiya, Kotaro and Richard E. Young. 2013. Abralia trigonura Berry 1913. Version 03 November 2013 (under construction). http://tolweb.org/Abralia_trigonura/19657/2013.11.03 in The Tree of Life Web Project, http://tolweb.org/

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