Calanus pacificus

Calanus pacificus is a species of copepod found in the Pacific Ocean. The female has an average length of about 3.1 millimetres (0.12 in), and the male has a value of about 2.9 millimetres (0.11 in).

Calanus pacificus
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Subphylum:
Crustacea
Class:
Maxillopoda
Subclass:
Copepoda
Order:
Calanoida
Family:
Calanidae
Genus:
Calanus
Species:
C. pacificus
Binomial name
Calanus pacificus
Brodsky, 1948

Description

The female is about 3.1 millimetres (0.12 in) in length, and typically ranges from 2.2 to 5.3 millimetres (0.087 to 0.209 in) in length. The male has an average length of about 2.9 millimetres (0.11 in), and ranges in length from about 2.4 to 4.4 millimetres (0.094 to 0.173 in).[1] The male has enlarged aesthetes (found on the antennules), which are likely used for chemoreception.[2]

Distribution

This copepod is found in the Pacific, from Alaska to Central America in coastal North America, and from Russia to southeast Asia in Asia.[1]

Ecology

Life cycle and reproduction

When the male senses a potential mate (likely through pheromones), it swims irregularly, alternating zig-zags with looping and figure eights. This is likely to find the potential mate or as a precopulatory behaviour.[2] C. pacificus This copepod typically lays a clutch of 24 to 54 eggs. The egg production rate increases with an increase in food, indicating that C. pacificus is an income breeder, relying on food stores gained concurrently with reproduction to breed.[3] In addition, it has three generations per year,[4] with generations being about 10 to 25 days.[5] This copepod does not migrate until it is a nauplius stage III, when it moves closer to the surface. This behaviour continues until it is a nauplius stage V. Then, until maturity, the depth during the day gets progressively deeper.[6] The depth of migration is influenced by predation; when there are more predators, the intensity of diel vertical migration increases.[7]

Feeding

C. pacificus is a particle feeder,[8] feeding on plankton, copepod nauplii,[9] and marine snow.[10] It generally feeds on the food of greatest abundance[9] and size. However, it also rejects low quality food, likely through chemical means, in addition to rejecting inert particles.[5] Examples of low quality food include Ptychodiscus brevis, which produces neurotoxins,[11] and Protoceratium reticulatum, which causes regurgitation or an elevated heart rate. Additionally, the presence of the latter decreases the intake of a preferred food, Gyrodiniurn resplendens. This allows P. reticulatum to decrease the concentration of C. pacificus when the former is in bloom.[5] C. pacificus can take advantage of marine snow as food, with aggregations of various compositions being responsible for between about .3 and 1.5 micrograms (4.6×10−6 and 2.31×10−5 gr) dry weight of fecal pellets copepod−1 hr−1 (per copepod per hour), at a maximum feeding rate. Assuming a 70% assimilation efficiency, this species can ingest from .3 to 1.8 micrograms (4.6×10−6 to 2.78×10−5 gr) marine snow copepod−1 hr−1. Another important food source, diatoms, are able to be ingested at a rate of about 1.1 micrograms (1.7×10−5 gr) copepod−1 hr−1.[10]

References
  1. Razouls C.; de Bovée F.; Kouwenberg J.; Desreumaux N. (2018). "Diversity and Geographic Distribution of Marine Planktonic Copepods". Sorbonne Université, CNRS. Retrieved 5 July 2018.
  2. Griffiths, Arthur M.; Frost, Bruce W. (1976). "Chemical communication in the marine planktonic copepods Calanus pacificus and Pseudocalanus sp". Crustaceana. 30 (1): 1–8. doi:10.1163/156854076X00323. ISSN 0011-216X.
  3. Runge, Jeffrey A. (1985). "Relationship of egg production of Calanus pacificus to seasonal changes in phytoplankton availability in Puget Sound, Washington". Limnology and Oceanography. 30 (2): 382–396. doi:10.4319/lo.1985.30.2.0382. ISSN 0024-3590.
  4. Sainmont, Julie; Andersen, Ken H.; Varpe, Øystein; Visser, André W. (2014). "Capital versus income breeding in a seasonal environment". The American Naturalist. 184 (4): 466–476. doi:10.1086/677926. ISSN 0003-0147. PMID 25226182.
  5. Huntley, M. E.; Sykes, P.; Rohan, S.; Marin, V. (1986). "Chemically-mediated rejection of dinoflagellate prey by the copepods Calanus pacificus and Paracalanus parvus: mechanism, occurrence and significance". Marine Ecology Progress Series. 28: 105–120. doi:10.3354/meps028105.
  6. Huntley, M.; Brooks, E. R. (1982). "Effects of age and food availability on diel vertical migration of Calanus pacificus". Marine Biology. 71 (1): 23–31. doi:10.1007/BF00396989. ISSN 0025-3162.
  7. Bollens, Stephen M.; Frost, Bruce W. (1989). "Zooplanktivorous fish and variable diel vertical migration in the marine planktonic copepod Calanus pacificus" (PDF). Limnology and Oceanography. 34 (6): 1072–1083. doi:10.4319/lo.1989.34.6.1072. ISSN 0024-3590.
  8. Huntley, M. E.; Barthel, K.-G.; Star, J. L. (1983). "Particle rejection by Calanus pacificus: discrimination between similarly sized particles". Marine Biology. 74 (2): 151–160. doi:10.1007/BF00413918. ISSN 0025-3162.
  9. Landry, M. R. (1981). "Switching between herbivory and carnivory by the planktonic marine copepod Calanus pacificus". Marine Biology. 65 (1): 77–82. doi:10.1007/BF00397070. ISSN 0025-3162.
  10. Dilling, L.; Wilson, J.; Steinberg, D.; Alldredge, A. (1998). "Feeding by the euphausiid Euphausia pacifica and the copepod Calanus pacificus on marine snow" (PDF). Marine Ecology Progress Series. 170: 189–201. doi:10.3354/meps170189. ISSN 0171-8630.
  11. Sykes, P. F.; Huntley, M. E. (1987). "Acute physiological reactions of Calanus pacificus to selected dinoflagellates: direct observations". Marine Biology. 94 (1): 19–24. doi:10.1007/BF00392895. ISSN 0025-3162.
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