Metridia longa

Metridia longa is a copepod found in the Arctic, the north Atlantic, the Pacific, and surrounding waters. The female has an average length of about 4.2 millimetres (0.17 in), and the males have an average length of about 3.5 millimetres (0.14 in).

Metridia longa
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Subphylum:
Crustacea
Class:
Maxillopoda
Subclass:
Copepoda
Order:
Calanoida
Family:
Metridinidae
Genus:
Metridia
Species:
M. longa
Binomial name
Metridia longa
(Lubbock, 1854)
Synonyms
  • Calanus longus Lubbock, 1854
  • Metridia armata Boeck, 1864

Description

M. longa females have an average length of about 4.2 millimetres (0.17 in), with an average range between about 1.6 millimetres (0.063 in) and 4.5 millimetres (0.18 in). Males are usually smaller, with an average length of around 3.5 millimetres (0.14 in), and a range between about 1.6 and 4 millimetres (0.063 and 0.157 in).[1] It is bioluminescent, emitting light when mechanically,[2] electrically, or chemically disturbed. This light is given through secretions containing luciferase from epidermal glands on the head and abdomen.[3]

Distribution

M. longa is found in the sub-Arctic, Arctic, north Atlantic, and the Pacific, along the coast of the Americas and Asia.[4] It has also been recorded in the Antarctic, in the Pacific Antarctic.[1]

Ecology

Life history and reproduction

At least in Balsfjorden, M. longa breeds from early to mid-May.[5] It uses recently ingested food to complete and release the eggs, but it likely uses stored lipids in oogenesis.[2] It has an average clutch size of about 33 eggs, not accounting for cannibalism. These eggs hatch with about 51% success after their 24 hour incubation period.[6] Stage I through V copepodites then develop during the summer.[5] Stages I through III are usually found below about 130 metres (430 ft) during the day, and generally do not migrate. In Arctic waters, it is typically found closer to the surface.[7] Also, in Balsfjorden, copepodite stages I through III were found to occur mostly in the top 50 metres (160 ft) of the fjord.[5] Copepodite stages IV through to the adult stage are migratory, moving from the deeper waters it inhabits during the day to shallower waters at night to feed. This is hypothesized to be because it could reduce the chance of predation, as predators relying on sight would find it harder to detect their prey in the dark.[7] This is further supported by the fact that it spends more time at the surface during the winter, when the nights are longer.[8] It is likely active during this winter season.[5] It also uses stored lipids to develop its gonads when it is overwintering.[2]

Feeding

M. longa is an omnivorous filter-feeder.[9] It cannibalizes its eggs, with a 2008 study finding it removed 38% of its eggs when food was abundant, until chlorophyll a concentrations reached below 50 milligrams (0.00011 lb) per 1 square metre (11 sq ft), when it started to remove an increasing amount of eggs, with a maximum of 85% of eggs removed.[6] It has been suggested that it uses omnivory during the winter to supplement its metabolic needs and its gonad development.[2]

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References
  1. Razouls C.; de Bovée F.; Kouwenberg J.; Desreumaux N. (2018). "Diversity and Geographic Distribution of Marine Planktonic Copepods". Sorbonne Université, CNRS. Retrieved 12 July 2018.
  2. Buskey, Edward J.; Stearns, Donald E. (1991). "The effects of starvation on bioluminescence potential and egg release of the copepod Metridia longa". Journal of Plankton Research. 13 (4): 885–893. doi:10.1093/plankt/13.4.885. ISSN 0142-7873.
  3. Markova, Svetlana V.; Golz, Stefan; Frank, Ludmila A.; Kalthof, Bernd; Vysotski, Eugene S. (2004). "Cloning and expression of cDNA for a luciferase from the marine copepod Metridia longa". Journal of Biological Chemistry. 279 (5): 3212–3217. doi:10.1074/jbc.M309639200. ISSN 0021-9258. PMID 14583604.
  4. "Metridia longa" at the Encyclopedia of Life
  5. Grønvik, S.; Hopkins, C.C.E. (1984). "Ecological investigations of the zooplankton community of Balsfjorden, northern Norway: Generation cycle, seasonal vertical distribution, and seasonal variations in body weight and carbon and nitrogen content of the copepod Metridia longa (Lubbock)". Journal of Experimental Marine Biology and Ecology. 80 (1): 93–107. doi:10.1016/0022-0981(84)90096-0. ISSN 0022-0981.
  6. Plourde, S; Joly, P (2008). "Comparison of in situ egg production rate in Calanus finmarchicus and Metridia longa: discriminating between methodological and species-specific effects". Marine Ecology Progress Series. 353: 165–175. doi:10.3354/meps07181. ISSN 0171-8630.
  7. Daase, Malin; Eiane, Ketil; Aksnes, Dag L.; Vogedes, Daniel (2008). "Vertical distribution of Calanus spp. and Metridia longa at four Arctic locations". Marine Biology Research. 4 (3): 193–207. doi:10.1080/17451000801907948. ISSN 1745-1000.
  8. Hays, Graeme C. (1995). "Ontogenetic and seasonal variation in the diel vertical migration of the copepods Metridia lucens and Metridia longa". Limnology and Oceanography. 40 (8): 1461–1465. CiteSeerX 10.1.1.533.6615. doi:10.4319/lo.1995.40.8.1461. ISSN 0024-3590.
  9. Connelly, Tara L.; Businski, Tara N.; Deibel, Don; Parrish, Christopher C.; Trela, Piotr; Smith, Ralph (2016). "Annual cycle of lipid content and lipid class composition in zooplankton from the Beaufort Sea shelf, Canadian Arctic". Canadian Journal of Fisheries and Aquatic Sciences. 73 (5): 747–758. doi:10.1139/cjfas-2015-0333. hdl:1807/71272. ISSN 0706-652X.
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