Rhincalanus nasutus explained

Rhincalanus nasutus is a copepod in the family Rhincalanidae.

Taxonomy and phylogeny

Rhincalanus nasutus is a species complex, composed of at least two cryptic species: one species consisting of, at the very least, individuals off of Peru, in the Sulu Sea, and in the California Current, in addition to another species composed of specimens from the Kuroshio Current, the southwest Pacific, and the northern Atlantic. In its genus, it is sister to R. gigas.^[1]

Description

The female of R. nasutus ranges anywhere from about 2.8mm6.1mm in length, and the male is generally between about 2.7mm4.5mm.

Distribution

Rhincalanus nasutus is found in waters across the globe,^[2] primarily in the open ocean^[3] and continental shelf and slope waters.^[4]

Ecology

Life cycle and reproduction

Rhincalanus nasutus is seasonal in terms of the timing of reproduction. Off of the waters of southern California, it generally reproduces from February to April, and it also can reproduce in late summer, as late as June. This reproduction is likely to be limited by food, as evidenced by this copepod failing to breed in the absence of food.^[5] Copepodite stages I through IV are usually found in the surface waters (from sea level to 200m (700feet) in depth). The abundance of individuals in the surface, however, varies seasonally: they are most abundant during the spring, and are not present during summer and autumn. Stage V copepodites and adults are generally distributed below 200m (700feet) in depth, and especially below 500m (1,600feet).^[6] In seasonal waters, such as the Gulf of Aqaba, stage V copepodites go into diapause to moult into females. During this time, they also rapidly accumulate wax esters, possibly for future reproduction.^[3]

Notes and References

1. Goetze. E.. Cryptic speciation on the high seas; global phylogenetics of the copepod family Eucalanidae. Proceedings of the Royal Society B: Biological Sciences. 270. 1531. 2003. 2321–2331. 0962-8452. 10.1098/rspb.2003.2505. 1691510. 14667347.
2. Web site: Razouls C.. de Bovée F.. Kouwenberg J.. Desreumaux N.. Diversity and Geographic Distribution of Marine Planktonic Copepods. 2018. 30 July 2018. Sorbonne Université, CNRS.
3. Schnack-Schiel. S. B.. Niehoff. B.. Hagen. W.. Böttger-Schnack. R.. Cornils. A.. Dowidar. M. M.. Pasternak. A.. Stambler. N.. Stübing. D.. Richter. C.. Population dynamics and life strategies of Rhincalanus nasutus (Copepoda) at the onset of the spring bloom in the Gulf of Aqaba (Red Sea). Journal of Plankton Research. 30. 6. 2008. 655–672. 0142-7873. 10.1093/plankt/fbn029. free.
4. Castro. L.R.. Bernal. P.A.. Troncoso. V.A.. Coastal intrusion of copepods: mechanisms and consequences on the population biology of Rhincalanus nasutus. Journal of Plankton Research. 15. 5. 1993. 501–515. 0142-7873. 10.1093/plankt/15.5.501.
5. 34. Mullin. Michael M.. Reproduction by the oceanic copepod Rhincalanus nasutus off southern California, compared to that of Calanus pacificus. CalCOFI Reports. 1993. 98–103.
6. Shimode. Shinji. Takahashi. Kazutaka. Shimizu. Yugo. Nonomura. Takumi. Tsuda. Atsushi. Distribution and life history of two planktonic copepods, Rhincalanus nasutus and Rhincalanus rostrifrons, in the northwestern Pacific Ocean. Deep Sea Research Part I: Oceanographic Research Papers. 65. 2012. 133–145. 0967-0637. 10.1016/j.dsr.2012.03.008.