Overview

Comprehensive Description

Biology

Notes:

Populations from different regions of the area of distribution exhibit small morphological differences. Individuals from the Polar Basin, Bering Sea, and the Pacific Ocean coast of Canada (typical Hyperia medusarum) are much larger, with much longer setae on pereopods I and II. Populations from the southern part of the area of distribution (for example, coastal areas between San Diego and Vancouver and off Japan) are smaller and exhibit morphological differences which led Bovallius (1889) to describe them as a separate species, H. hystrix. Stephensen (1924) studied the syntypes of Bovallius and treated H. hystrix as a synonym of H. medusarum. Bowman (1973) analyzed vast material and found specimens incorporating characters of both forms, which compelled him to support the opinion of Stephensen. Living in notal waters, H. gaudichaudi M.-Edw. is morphologically identical to the northern H. medusarum F. hystrix and recognition of its specific separate identity can only be based on its scattered area of distribution.
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Source: Pelagic Invertebrates LifeDesk

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Distribution

A bipolar species. Cold-water and moderately cold-water regions for both Hemispheres. It is more oceanic than H. galba and is absent in the Baltic Sea. In the Atlantic Ocean it is not found farther south than the North Sea, but in the Pacific Ocean along the American coast is common up to 30° N. In the Southern hemisphere it is found in the southern coastal areas of Africa. Australia and South America (to 8° S 80° 32' W on the Pacific coast). There are doubtful references about its occurrence in the Ross Sea. [Muller, 1776]
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Source: Pelagic Invertebrates LifeDesk

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Arctic to Gulf of Maine
  • North-West Atlantic Ocean species (NWARMS)
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Source: World Register of Marine Species

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Physical Description

Size

Length of sexually mature specimens in the Arctic seas up to 20 mm, in Antarctic waters exceeds 20 mm, and in the remaining part of the species' area of distribution ranges from 9-15 mm. [Muller, 1776]
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Source: Pelagic Invertebrates LifeDesk

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Diagnostic Description

The head is equal in length to the first two somites of the pereon. The interantennal lobe is developed to a variable extent. The flagellum of antennae I in females is uncinate, but in antennae II very thin. The length ratio of the segments of the palp of the mandibles is 10:17:21 and the distally tapering 3rd segment is almost straight. The 6th segment of pereopods I and II bears many strong setae on the lateral surface; this ornamentation is especially well developed in large specimens. In F. medusarum the setae extend to the apical end of the claw while in H. hystrix they are relatively shorter and the claw is longer. The posterior margin of the 6th and 7th segments is denticulate; this denticulation, however, is not readily discernible in F. medusarum because masked by the setae and unevenness of the posterior margin. The distal part of the 4th and 5th segments of pereopods III-IV bears a row of long and short spines, the long spines extending to half the width of the segment; in males these spines are fewer and may even be totally absent on the 4th segment; the 6th segment is finely denticulate, the anterior margin generally not armed, but sometimes bears a few spinules. Pereopods V-VII are approximately equal in length in females but in males pereopods V are somewhat longer than the identical pereopods VI and VII. The lower posterior angles of the epimerons are produced into denticles, especially well developed in epimeron III. [Muller, 1776]
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Source: Pelagic Invertebrates LifeDesk

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Look Alikes

Muller, 1776: 196 (Cancer); Bovallius, 1889: 147; Stephensen, 1923: 15; Bowman, 1973: 6. --latreillei Milne-Edwards, 1830: 388; Bovallius, 1889: 164. --gaudichaudi Milne-Edwards, 1840: 77; Bate, 1862: 289 (Lestrigonus); Stebbing, 1888: 1394; Bovallius, 1889: 175; Dick, 1970: 55; Bowman, 1973: 13. --hystrix Bovallius, 1889: 159. --spinigera (non Bovallius, 1889); Barnard, 1930: 412; Thorsteinson, 1941: 87.
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Source: Pelagic Invertebrates LifeDesk

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Ecology

Habitat

pelagic and parasitic (host-eg. Cyanea)
  • North-West Atlantic Ocean species (NWARMS)
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Source: World Register of Marine Species

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Depth range based on 374 specimens in 2 taxa.
Water temperature and chemistry ranges based on 346 samples.

Environmental ranges
  Depth range (m): 0 - 1679
  Temperature range (°C): -1.287 - 11.982
  Nitrate (umol/L): 1.825 - 34.538
  Salinity (PPS): 26.075 - 35.370
  Oxygen (ml/l): 2.018 - 8.895
  Phosphate (umol/l): 0.440 - 2.747
  Silicate (umol/l): 2.376 - 61.795

Graphical representation

Depth range (m): 0 - 1679

Temperature range (°C): -1.287 - 11.982

Nitrate (umol/L): 1.825 - 34.538

Salinity (PPS): 26.075 - 35.370

Oxygen (ml/l): 2.018 - 8.895

Phosphate (umol/l): 0.440 - 2.747

Silicate (umol/l): 2.376 - 61.795
 
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