Overview

Distribution

A circumpolar cold-water species. It inhabits the Central Polar Basin, where it was found right up to the Polar region and peripheral Arctic seas. In the Atlantic Ocean it moves with cold waters along the coasts of America up the Gulf of St. Lawrence and coasts of Newfoundland; in the eastern part of the ocean it is not found south of Iceland and Nordkapp. In the Pacific Ocean it is numerous in the much colder water regions of the Bering and Okhotsk seas, occupied by the "arctic" plankton complex. In the cold season of the year it is found in small numbers on the oceanic side of the North Kuril Islands and in the eastern coastal regions of Kamchatka. [Lichtenstein, 1822]
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Source: Pelagic Invertebrates LifeDesk

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Gulf of St. Lawrence (unspecified region), Southern Gaspe waters (Baie des Chaleurs, Gaspe Bay to American, Orphan and Bradelle banks; eastern boundary: Eastern Bradelle Valley), Downstream part of Middle St. Lawrence Estuary, Lower St. Lawrence Estuary, Middle North Shore (from Sept- Iles to Cape Whittle, including the Mingan Islands), Lower North Shore, Lower Laurentian Channel (bathyal zone)(=Esquiman Channel), and the Western slope of Newfoundland, including the southern part of the Strait of Belle Isle but excluding the upper 50m in the area southwest of Newfoundland
  • North-West Atlantic Ocean species (NWARMS)
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Source: World Register of Marine Species

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Physical Description

Size

This is a much larger species of the genus. Sexually matures specimens are generally up to 30 mm in length but females sometimes up to 60 mm. [Lichtenstein, 1822]
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Diagnostic Description

The somites of the pereon and pleon are without dorsal denticles. The head is spherical and the lower frontal angle round. Antennae I and II in females are approximately equal in length; the flagellum of antennae I is conical and the thin distal part not curved. In young males antennae I are almost the same in structure as in females and their flagellum unsetgmented. Antennae II in females and young are somewhat longer than antennae I, their flagellum thin and unsegmented, and the total length somewhat greater than the length of the head. The mandibles have a narrow denticulate cutting edge (the left mandible has an accessory plate) and a strong dentate process; the 1st segment of the palp is 2/3 the length of the 2nd and barely shorter than the slightly curved 3rd segment. Maxillae I have a strong spine on the distal margin of the outer lobe and the inner margin of the palp is denticulate almost throughout its length. The outer lobe of maxillae II is narrower than the inner and apically bears two strong spines. The outer lobes of the maxillipeds are somewhat broader than in other species of the genus, the inner margin is finely denticulate but the outer convex margin bears one or several long setae; much shorter setae are present also on the surface of the lobe; the basal segment bears a row of setae along the anterior margin. Pereopods I are strong; the conical 6th segment is somewhat shorter than the distally broadened 5th segment, and both segments bear numerous setae on the anterior and posterior margins and on the surface; the claw is strong, slightly curved, and very finely denticulate in the distal part of the inner margin. The distal process of the 5th segment of pereopods II extends to the distal end of the 6th segment, both its margins bear short and strong setae, and the process terminates in a short and strong apical spine; the conical 6th segment bears long setae on the anterior margin. The 2nd segment of pereopods III is broad and tapers in the proximal part; the 4th segment is short and trapezoid; the 5th segment is broadly oval, its maximum width 2/3 its length; the narrow 6th segment is slightly curved, and equal to or somewhat longer than the 5th; the claw is strong and bears a fascicle of short setae in the proximal part of the posterior margin. Pereopods IV are longer but the 5th segment relatively narrower. Pereopods V are significantly longer than all the other legs; the broad 2nd segment has a straight posterior margin while its anterior margin is concave in the proximal part; the 3rd and 4th segments are very short; the strong 5th segment is broad in the proximal part, gradually tapers distally, and is sometimes club-shaped, the narrow 6th segment is straight, and equal in length to the 3rd, 4th, and 5th or the 4th and 5th segments together; the anterior margin of the 5th and 6th segments bears a row of sparse strong setae in the proximal part of the anterior margin. Pereopods VI and VII are almost identical in length and structure; the 2nd segment is broad and linear or its margins are concave in the middle part; the 4th segment is almost half as wide as long; the 5th segment is linear and equal to or slightly shorter than the much narrower 6th segment; the claws have a fascicle of setae on the anterior margin. The uropods are long and narrow; the endopodites of uropods I and II are equal to the basipodites while the exopodites are shorter. The rami of uropods III are broad and shorter than the basipodite; the inner distal angle of the basipodite is acute and stretched. The margins of the rami have fine denticulation which is poorly noticeable. The oblong-triangular telson has an acute apex. [Lichtenstein, 1822]
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Look Alikes

Lichtenstein, 1822: 32 (Gammarus); Goës, 1866: 533 (Themisto); Bovallius, 1889: 221 (Euthemisto); Sars, 1893: 13; Stephensen, 1923: 24 (Themisto); Schellenberg, 1927: 627: Vinogradov, 1956: 211 (Euthemisto); Barnard; 1959: 123; Bowman, 1960: 382.
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Ecology

Habitat

upper and glacial epipelagic regions of the Gulf and estuary
  • North-West Atlantic Ocean species (NWARMS)
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Depth range based on 602 specimens in 1 taxon.
Water temperature and chemistry ranges based on 409 samples.

Environmental ranges
  Depth range (m): 0 - 1090
  Temperature range (°C): -1.707 - 4.204
  Nitrate (umol/L): 0.007 - 24.312
  Salinity (PPS): 20.825 - 34.921
  Oxygen (ml/l): 5.945 - 9.319
  Phosphate (umol/l): 0.240 - 2.241
  Silicate (umol/l): 2.027 - 54.130

Graphical representation

Depth range (m): 0 - 1090

Temperature range (°C): -1.707 - 4.204

Nitrate (umol/L): 0.007 - 24.312

Salinity (PPS): 20.825 - 34.921

Oxygen (ml/l): 5.945 - 9.319

Phosphate (umol/l): 0.240 - 2.241

Silicate (umol/l): 2.027 - 54.130
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Dispersal

The crustaceans mainly concentrate in the upper 100 m layer but individuals are found in deeper waters also, up to 500 or even up to 1,000 m. [Lichtenstein, 1822]
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Themisto libellula

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 8
Specimens with Barcodes: 68
Species With Barcodes: 1
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Source: Barcode of Life Data Systems (BOLD)

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Barcode data: Themisto libellula

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 8 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

CTTTATTTTTTTTTAGGTCTTTGAAGAGGTTTAGTAGGTACGTCTATA---AGTACTATTATTCGTATAGAATTAAGAACTAAAGGTTCTTTATTAGGAGAT---GATCAGATTTATAATGTTATAGTGACAGGGCACGCTTTTATTATAATTTTTTTTATAGTTATACCTATTATAATTGGGGGGTTTGGTAATTGACTTGTTCCTTTAATG---TTAGGGAGTGTAGATATAGCTTTTCCTCGTATAAATAACATAAGGTTTTGATTATTAGTTCCTTCTTTTATACTATTAGCTTTAAGTAGAATAGTGGAGAGAGGCGTAGGGGCTGGTTGGACTTTATACCCTCCTCTATCTTCTTCTATAGGCCACAGAGGTTCTGCTGTTGATGTT---GCTATTTTTTCTTTACATTTAGCAGGTGTTTCTTCTATTTTAGGAGCTATTAATTTTATAACTACTATTTTAAATATACGAAGAAGAGGGTTTAAAATATTTTATATAAGTCTATTTGTTTGAGCTGTTTTTATCACAGCTATTTTGTTACTATTATCGTTACCTGTATTAGCAGGG---GGGATTACTATACTTTTATTAGATCGGAATTTAAACACTTCTTTTTTTAACCCTATGGGAGGAGGGGATCCTGTTTTATACCAACATTTGTTTTGATTTTTTGGTCACCCC
-- end --

Download FASTA File
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