Overview

Brief Summary

Introduction

Ancistrocheirus lesueurii is of moderate size (25 cm ML) and occupies tropical and subtropical waters of the world's oceans at mesopelagic depths. Adults may be associated with the ocean floor over the slope (Nesis, 1982/7). They bear hooks on the arms and tentacles and have large sagittate fins. Photophores have a distinctive arrangement and appearance. Those on the ventral surface of the head and mantle occur in two very different size catagories.

Brief diagnosis:

A member of the enoploteuthid families ...

  • with numerous, small integumental photophores, including photophores on the tentacles but without photophores on the eyeballs or viscera.

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Comprehensive Description

Distristribution

This species is found throughout the tropical and subtropical oceans of the world (Young et al., 1998).

Insufficient material has been available for critical species-level comparisons of specimens from different regions.

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Nomenclature

Orbigny (1834-48) described Enoploteuthis lesueurii in 1842 from the Indian Ocean, and Gray (1849) designated it the type species of his genus Ancistrocheirus. In 1851, Verany described Loligo alessandrinii from off Messina, Mediterranean; it was first placed in Calliteuthis Verrill, 1880 by Appellof (1890), then Pfeffer in 1900 reassigned it to his new genus Thelidioteuthis. Subsequently both genera and their species were synonomyzed (Nesis, 1978). The Enoploteuthidae, Pyroteuthidae and Ancistrocheiridae generally, have been considered subfamilies of the Enoploteuthidae. Clarke (1988) raised each subfamily to familial status and Young and Harman (1998) provided cladistic support for this arrangement.

A list of all nominal genera and species in the Ancistrocheiridae can be found here. The list includes the current status and type species of all genera, and the current status, type repository and type locality of all species and all pertinent references.

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Characteristics

  1. Head, arms, and tentacles
    1. Nuchal folds present.
    2. Hooks present on all arms.
    3. Tentacular clubs with hooks in two series on manus; suckers absent from manus; dactylus reduced.

      Figure. Left - Oral-lateral view of the tentacular club of A. lesueurii. Right - Enlarged view of the dactylus and terminal pad of the same club. Photographs by R. Young.

    4. Tentacles not modified near base; stalk "ligament" and vein leave tentacle at base and in a membrane.

  2. Beaks
    1. Descriptions can be found here: Lower beak; upper beak.

  3. Mantle, fins and gladius
    1. Fins slightly subterminal.
    2. Tail fleshy, large; vesicles absent.
    3. Gladius with long pointed rostrum.

  4. Photophores
    1. Photophores on head and mantle in two distinct size classes.
    2. Photophores on head, funnel, arms, tentacular stalk, mantle and fins.
    3. Mature males with large, lidded, elongate photophores on aboral tips of arms IV; mature females with apparent photophores on tips of dorsal six arms.
    4. No photophores on eyeballs or viscera.

  5. Viscera
    1. Nidamental glands present.
    2. Oviducal glands normal.
    3. Oviducts equally developed.

Comments

More details of the description of A. lesueurii can be found here.

The number of large photophores on the mantle apparently increases through growth. A large mature female (180 mm Ml) from Hawaii had 24 of these organs.

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Distribution

Western Atlantic: New England to the West Indies
  • North-West Atlantic Ocean species (NWARMS)
Creative Commons Attribution 3.0 (CC BY 3.0)

© WoRMS for SMEBD

Source: World Register of Marine Species

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Ecology

Habitat

Depth range based on 20 specimens in 1 taxon.
Water temperature and chemistry ranges based on 19 samples.

Environmental ranges
  Depth range (m): 50 - 2100
  Temperature range (°C): 3.466 - 26.773
  Nitrate (umol/L): 1.114 - 31.440
  Salinity (PPS): 34.336 - 36.130
  Oxygen (ml/l): 1.983 - 6.036
  Phosphate (umol/l): 0.360 - 2.059
  Silicate (umol/l): 1.897 - 30.560

Graphical representation

Depth range (m): 50 - 2100

Temperature range (°C): 3.466 - 26.773

Nitrate (umol/L): 1.114 - 31.440

Salinity (PPS): 34.336 - 36.130

Oxygen (ml/l): 1.983 - 6.036

Phosphate (umol/l): 0.360 - 2.059

Silicate (umol/l): 1.897 - 30.560
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Life History and Behavior

Life Cycle

Life History

Paralarvae of A. lesueurii differ from those of other members of the enoploteuthid families by:

  • Relatively small, broadly spaced eyes.
  • Separation of the eyes from the arm bases.
  • Gelatinous head tissues.
  • Posterior position and kidney-bean shape of the digestive gland.

Figure. Paralarvae of A. lesueurii from Hawaiian waters. Far left (thumbnail) - Shows the relative size of the two stages. Left - 2.8 mm ML. Right - 6.2 mm ML; note that the ventral view shows 3 pairs of photophores on the mantle and 1 pair on the head. Each scale bar is 1 mm. Drawings by R. Young.

The tentacular clubs of advanced paralarvae are distinctive in having the suckers of the lateral series larger than suckers of the medial series.

Figure. Paralarval club of A. lesueurii, ML not stated, from Naef, 1921/23.

The early paralarvae can be confused with Octopoteuthis paralarvae by the large suckers on the clubs but are easily distinguished by the more numerous club suckers and more muscular tentacles in the former as well as the lack of a disc-shaped digestive gland characteristic of the latter genus.

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Wikipedia

Ancistrocheirus lesueurii

Ancistrocheirus lesueurii, the sharpear enope squid, is the only species in the genus Ancistrocheirus and family Ancistrocheiridae. With a mantle length of 25 cm, this moderately sized squid may be found throughout the tropical and subtropical oceans. They tend to be found at mesopelagic depths (200-1000 m down).

Although only one species is recognized, some have suggested more than one species may exist due to differences in the paralarval morphology. Paralarva is the first free-living stage for cephalopods.

Characteristics[edit]

The buccal crown of the sharpear enope squid is heavily pigmented. The squid has no vesicles. There are hooks on all its arms. The suckers are absent from its manus and the squid's dactylus is reduced.

Photophores[edit]

Photophores occur throughout its body. Large photophores are present on its head, funnel, base of arms, and tentacular stalk. Other photophores are present on the ventral surface of its mantle (usually 22), with numerous very small photophores on its head, funnel, base of arms II and tentacular stalk. Mature males have large photophores on tips of arms IV opposite the mouth. Mature females have photophores on tips of their dorsal six arms. The number of large photopores on the squid's mantle increases as it matures.

References[edit]

  1. ^ Allcock, L. & Barratt, I. (2014). "Ancistrocheirus lesueurii". IUCN Red List of Threatened Species. Version 2014.1. International Union for Conservation of Nature. Retrieved 30 June 2014. 
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Source: Wikipedia

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