Calanus pacificus

{{Speciesbox | taxon = Calanus pacificus | authority = Brodsky, 1948 }}

'''''Calanus pacificus''''' is a species of copepod found in the Pacific Ocean. The female has an average length of about {{convert|3.1|mm|in}}, and the male has a value of about {{convert|2.9|mm|in}}.

==Description== The female is about {{convert|3.1|mm|in}} in length, and typically ranges from {{convert|2.2|to|5.3|mm|in}} in length. The male has an average length of about {{convert|2.9|mm|in}}, and ranges in length from about {{convert|2.4|to|4.4|mm|in}}.<ref name="copepoddiversity"/> The male has enlarged aesthetes (found on the antennules), which are likely used for chemoreception.<ref name="GriffithsFrost1976"/>

==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.<ref name="copepoddiversity">{{cite web|author1=Razouls C.|author2=de Bovée F.|author3=Kouwenberg J.|author4=Desreumaux N.|url=https://copepodes.obs-banyuls.fr/en/fichesp.php?sp=508|title=Diversity and Geographic Distribution of Marine Planktonic Copepods|year=2018|access-date=5 July 2018|publisher=Sorbonne Université, CNRS}}</ref>

==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.<ref name="GriffithsFrost1976">{{cite journal|last1=Griffiths|first1=Arthur M.|last2=Frost|first2=Bruce W.|title=Chemical communication in the marine planktonic copepods ''Calanus pacificus'' and ''Pseudocalanus'' sp.|journal=Crustaceana|volume=30|issue=1|year=1976|pages=1–8|issn=0011-216X|doi=10.1163/156854076X00323|s2cid=85287105 |url=https://pdfs.semanticscholar.org/fb6a/316934f2aabf8a16534f0d71763ef2cf9308.pdf|archive-url=https://web.archive.org/web/20200227204511/https://pdfs.semanticscholar.org/fb6a/316934f2aabf8a16534f0d71763ef2cf9308.pdf|url-status=dead|archive-date=2020-02-27}}</ref> ''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.<ref name="Runge1985">{{cite journal|last1=Runge|first1=Jeffrey A.|title=Relationship of egg production of ''Calanus pacificus'' to seasonal changes in phytoplankton availability in Puget Sound, Washington|journal=Limnology and Oceanography|volume=30|issue=2|year=1985|pages=382–396|issn=0024-3590|doi=10.4319/lo.1985.30.2.0382|doi-access=free}}</ref> In addition, it has three generations per year,<ref name="SainmontAndersen2014">{{cite journal|last1=Sainmont|first1=Julie|last2=Andersen|first2=Ken H.|last3=Varpe|first3=Øystein|last4=Visser|first4=André W.|title=Capital versus income breeding in a seasonal environment|journal=The American Naturalist|volume=184|issue=4|year=2014|pages=466–476|issn=0003-0147|doi=10.1086/677926|pmid=25226182}}</ref> with generations being about 10 to 25 days.<ref name="HuntleySykes1986"/> 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.<ref name="HuntleyBrooks1982">{{cite journal|last1=Huntley|first1=M.|last2=Brooks|first2=E. R.|title=Effects of age and food availability on diel vertical migration of ''Calanus pacificus''|journal=Marine Biology|volume=71|issue=1|year=1982|pages=23–31|issn=0025-3162|doi=10.1007/BF00396989}}</ref> The depth of migration is influenced by predation; when there are more predators, the intensity of diel vertical migration increases.<ref name="BollensFrost1989">{{cite journal|last1=Bollens|first1=Stephen M.|last2=Frost|first2=Bruce W.|title=Zooplanktivorous fish and variable diel vertical migration in the marine planktonic copepod ''Calanus pacificus''|journal=Limnology and Oceanography|volume=34|issue=6|year=1989|pages=1072–1083|issn=0024-3590|doi=10.4319/lo.1989.34.6.1072|s2cid=84472360 |doi-access=free}}</ref>

===Feeding=== ''C. pacificus'' is a particle feeder,<ref name="HuntleyBarthel1983">{{cite journal|last1=Huntley|first1=M. E.|last2=Barthel|first2=K.-G.|last3=Star|first3=J. L.|title=Particle rejection by ''Calanus pacificus'': discrimination between similarly sized particles|journal=Marine Biology|volume=74|issue=2|year=1983|pages=151–160|issn=0025-3162|doi=10.1007/BF00413918}}</ref> feeding on plankton, copepod nauplii,<ref name="Landry1981"/> and marine snow.<ref name="DillingWilson1998">{{cite journal|last1=Dilling|first1=L.|author-link1=Lisa Dilling|last2=Wilson|first2=J.|last3=Steinberg|first3=D.|last4=Alldredge|first4=A.|title=Feeding by the euphausiid ''Euphausia pacifica'' and the copepod ''Calanus pacificus'' on marine snow|journal=Marine Ecology Progress Series|volume=170|year=1998|pages=189–201|issn=0171-8630|doi=10.3354/meps170189|url=https://www.int-res.com/articles/meps/170/m170p189.pdf|doi-access=free}}</ref> It generally feeds on the food of greatest abundance<ref name="Landry1981">{{cite journal|last1=Landry|first1=M. R.|title=Switching between herbivory and carnivory by the planktonic marine copepod ''Calanus pacificus''|journal=Marine Biology|volume=65|issue=1|year=1981|pages=77–82|issn=0025-3162|doi=10.1007/BF00397070}}</ref> and size. However, it also rejects low quality food, likely through chemical means, in addition to rejecting inert particles.<ref name="HuntleySykes1986"/> Examples of low quality food include ''Ptychodiscus brevis'', which produces neurotoxins,<ref name="SykesHuntley1987">{{cite journal|last1=Sykes|first1=P. F.|last2=Huntley|first2=M. E.|title=Acute physiological reactions of ''Calanus pacificus'' to selected dinoflagellates: direct observations|journal=Marine Biology|volume=94|issue=1|year=1987|pages=19–24|issn=0025-3162|doi=10.1007/BF00392895}}</ref> 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.<ref name="HuntleySykes1986">{{cite journal|last1=Huntley|first1=M. E.|last2=Sykes|first2=P.|last3=Rohan|first3=S.|last4=Marin|first4=V.|title=Chemically-mediated rejection of dinoflagellate prey by the copepods ''Calanus pacificus'' and ''Paracalanus parvus'': mechanism, occurrence and significance|journal=Marine Ecology Progress Series|year=1986|volume=28|pages=105–120|doi=10.3354/meps028105|doi-access=free}}</ref> ''C. pacificus'' can take advantage of marine snow as food, with aggregations of various compositions being responsible for between about {{convert|.3|and|1.5|μg}} 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 {{convert|.3|to|1.8|μg}} marine snow copepod−1 hr−1. Another important food source, diatoms, are able to be ingested at a rate of about {{convert|1.1|μg}} copepod−1 hr−1.<ref name="DillingWilson1998"/>

==References== {{Reflist}}

Category:Calanoida Category:Crustaceans described in 1948