Overview

Brief Summary

Introduction

Diagnosis

A Gonatus ...

  • without two large, deep chromatophores on the ventral surface of the head.
  • with 4-5 hooks (largest most distal) and 1 sucker proximal to large central hook on club.
  • with about 50 on median portion of tentacular stalk.

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Comprehensive Description

Characteristics

  1. Arms
    1. 46-57 suckers in proximal half of each arm IV.

  2. Tentacles
    1. Clubs 20-36% of GL (25% in holotype).
    2. Club dactylus with 7-8 irregular sucker series at base becoming 4 series about half way out dactylus.
    3. Club ventral-marginal zone with 4 series of suckers in central region; medial suckers ca. one-half diameter of suckers in two marginal series. Largest suckers slightly smaller than largest arm suckers.

      Figure. Oral view of the proximal hooks and suckers of the medial zone and suckers of the ventral-marginal zone of the club of G. steenstrupi, fresh. Round structures are air bubbles. Photograph by M. Vecchione with transmitted light taken aboard the R/V G. O. SARS during the MARECO cruise to the central North Atlantic.

    4. Club dorsal-marginal zone with suckers in 4 irregular series.
    5. Club medial zone with large central hook; medium distal hook and proximal series with usually 4 small hooks and a sucker. Hooks decrease in size proximally. Sometimes the sucker replaced by 5th hook. Sometimes 6 hooks and rarely only 3 hooks present.
    6. Total number of suckers (excluding terminal pad, medial zone) on tentacular club: 190-225.
    7. Median region of tentacular stalk between marginal series with about 75-165 suckers.


    8. Figure. Oral views of the tentacle and club of G. steenstrupi, 94 mm GL, holotype. Top - Tentacle. Bottom - Enlargement of the tentacular club. Drawings from Kristensen (1981).


      Figure. Oral view of a tentacular club of a late juvenile G. steenstrupi, alive. The proximal suckers are just beginning to transform into hooks. Photograph by David Shale.

  3. Head
    1. Radula
      1. Lateral teeth of radula profiled by a ridge.
      2. Figure. Radula of G. steenstrupi, 57 mm ML. Drawing from Kristensen (1981).

    2. Funnel
      1. Ventral pads of funnel organ about two thirds length of each ramus of dorsal pads
      2. Figure. View of the funnel organ of G. steenstrupi, holotype, 94 mm GL. Drawing from Kristensen (1981).

  4. Pigmentation
    1. Two unusually large chromatophores absent from the ventral surface of the head.

Comments

The above description, except for the photograph, is from Kristensen (1981). More details of the description can be found here.

All of the above features are useful in separating G. steenstrupi from G. fabricii. However, the lack of head chromatophores and the presence of usually 4 hooks proximal to the large central hook of the club are the easiest to identify.

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Distribution

Range Description

This species is known from the boreal and temperate waters of the North Atlantic, ranging from Newfoundland and Greenland to the west coast of Scotland, Rockall Trough and Portugal (Roper et al. 2010, Vecchione and Young 2007).
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Type locality: "east of Rock All, Northeast Atlantic". This is presumably Rockall trough so the locality would be in the vicinity of 57°N, 12°W

Figure. Distribution of Gonatus spp. in the North Atlantic. Blue - G. steenstrupi. Red - G. fabricii. General map with dots and triangles from Kristensen (1981). Red and blue lines based mostly on paralarvae, from Falcon, et al. (2000).

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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This is an oceanic species which is an important part of the diet of toothed whales (Roper et al. 2010). Gonatids are medium sized oceanic squid that occur over a wide depth range from near the surface to more than 1,000 m in depth (Kubodera et al. 2006). Generally their planktonic paralarvae young are most abundant between 200-300 m in depth and highest abundances appear to occur over the continental slopes in summer (Okutani and Clarke 1992). Gonatus species attain a maximum mantle length of 400 mm (Kubodera et al. 2006).

Systems
  • Marine
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epi-mesopelagic
  • UNESCO-IOC Register of Marine Organisms
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Source: World Register of Marine Species

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Depth range based on 14 specimens in 1 taxon.
Water temperature and chemistry ranges based on 12 samples.

Environmental ranges
  Depth range (m): 992 - 3458.5
  Temperature range (°C): 2.878 - 4.365
  Nitrate (umol/L): 16.616 - 18.394
  Salinity (PPS): 34.904 - 34.982
  Oxygen (ml/l): 5.915 - 6.416
  Phosphate (umol/l): 1.092 - 1.169
  Silicate (umol/l): 10.743 - 15.395

Graphical representation

Depth range (m): 992 - 3458.5

Temperature range (°C): 2.878 - 4.365

Nitrate (umol/L): 16.616 - 18.394

Salinity (PPS): 34.904 - 34.982

Oxygen (ml/l): 5.915 - 6.416

Phosphate (umol/l): 1.092 - 1.169

Silicate (umol/l): 10.743 - 15.395
 
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 G. steenstrupi are most easily separated from the partially sympatric species, G. fabricii by the absence of two large photophores on the ventral surface of the head that distinguish the adults as well. The number of suckers on arms I-IV is useful at sizes greater than 13 mm ML as is the form of the funnel organ in all but smallest paralarvae. The paralarval stage appears to end at about 20 mm ML which corresponds with hook development and movement into deeper water (Falcon, et al., 2000).


Figure. Left - Ventral views of growth stages of G. steenstrupi showing the absence of head chromatophores and the form of the funnel organ. Drawings from Falcon, et al. (2000). Right - Juvenile G. seenstrupi, live, showing pigment pattern. Photograph by David Shale

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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2014

Assessor/s
Barratt, I. & Allcock, L.

Reviewer/s
Young, R., Vecchione, M. & Böhm, M.

Contributor/s
Duncan, C. & Carrete-Vega, G.

Justification
Gonatus steenstrupi is an oceanic species which has been assessed as Least Concern, as it has a wide geographic distribution, making it less susceptible to human impact. However, further research is recommended in order to determine the precise distribution, population dynamics, life history and ecology, and potential threat processes affecting this species.
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Population

Population
There is no population information available for this species.

Population Trend
Unknown
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Threats

Major Threats
The threats to this species are not known.
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Source: IUCN

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Management

Conservation Actions

Conservation Actions
There are no species-specific conservation measures in place for this species. Further research is recommended in order to determine the precise distribution, population dynamics, life history and ecology, and potential threat processes affecting this species.
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