Metridia pacifica

Metridia pacifica Brodsky, 1950

Languages: English

Overview

Description

Body clear with a whitish tint

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Description

Diagnostic Description

The greatest height of the head (from side view) is almost the same as the tip of the head, so that it forms practically a straight angle. P5 three-segmented, the chaetae of the distal segment of P5 of the same length.
The caudal rami in males are longer than the anal segment; the left P5 contains 2 inner spines.

According to Mazzocchi & al. (1995) the systematic literature is contradictory and insufficient to clearly distinguish between M. pacifica and M. lucens.

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Morphology

Female:
The back is strongly arched from side view, the greatest height of the head (from side view) is almost the same as the tip of the head, so that it forms practically a straight angle. The posterior corners of the last thoracic segment with small sharp points, which are visible both from dorsal and side view. Abdomen almost 2 times shorter than the cephalothorax. The genital segment is approximately the same length as the next 2 segments combined. The anal segment is somewhat shorter than the caudal rami. P5 three-segmented, the distal segment carries 3 cheatae of practically equal length. This segment and also the 2nd segment each carries a long spine on its outer edge.

Male:
The distal segment of the right P5 is larger than the left and does not narrow distally. The left P5 with 2 large spines on the inner edge. The right leg is 4-segmented.

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Size

Female: 2,40-3,45 mm
Male: 1,65-2,60 mm

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Ecology and Distribution

Distribution

North Pacific and sub-Arctic Seas. In the north goes as far as the southern Chukchi. For Kosobokova & Hopcroft (2010) this species is an Pacific expatriate in Arctic waters.

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Habitat

Oceanic, epi- to bathypelagic species.

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References

Brodsky, K. A. (1950).  Calanoida of the Far Eastern Seas and Polar Basin of the USSR. Opred. Fauna SSSR. 441. Leningrad: Publishing House of the USSR Academy of Sciences.
C., R., de F. B., J. K., & N. D. (2011).  Diversity and Geographic Distribution of Marine Planktonic Copepods.
Kosobokova, K. N., & Hopcroft R. R. (2010).  Diversity and vertical distribution of mesozooplankton in the Arctic's Canada Basin. Deep Sea Research Part II. 57, Abstract
Mazzocchi, M. G., Zagami G., Ianora A., L. G., & J. H. (1995).  Copepods.. (IanoraA., L. G., Ed.).Atlas of Marine Zooplankton Straits of Magellan.. 279.