Very clear body, with a slight red or yellow tint
Head triangular above A1, rostral filaments invisible from dorsal view. Apical spine on the right P5 in males is curved.
Widely distributed cosmopolitan species. Reproduction not assumed in polar waters
Oceanic bathypelagic species; in its northern range may occur near the surface
Female: Head shape triangular above the antennulae, head not fused with first segment. Rostrum consists of 2 filaments, usually invisible from dorsal view. A1 significantly longer than the body. Each segment of the abdomen, including the genital segment, carries 2 spines on its dorsal side. P5 three-segmented. The second segment of P5 carries 1 lateral chaeta, the third – 1 lateral and 2 apical chaetae. Abdomen 3 segmented due to fusion of anal segment with the furca. Caudal rami slightly asymmetrical and carry 2 aggregations of hairs at the anal region.
Male: Very similar body shape as in female. The left exopodite of P5 consists of one short segment, which carries several chaetae; the distal segment of the right P5 with a large curved spine.
Female: 2,82-6,10 mm
Male: 2,70-4,50 mm
Rhincalaus nasutus is a copepod in the family Rhincalanidae.
R. 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]
The female of R. nasutus ranges anywhere from about 2.8 to 6.1 millimetres (0.11 to 0.24 in) in length, and the male is generally between about 2.7 and 4.5 millimetres (0.11 and 0.18 in).[2]
R. nasutus is found in waters across the globe,[2] primarily in the open ocean[3] and continental shelf and slope waters.[4]
R. 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 200 metres (660 ft) 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 200 metres (660 ft) in depth, and especially below 500 metres (1,600 ft).[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]
Rhincalaus nasutus is a copepod in the family Rhincalanidae.
