Temperature effects on Calanus helgolandicus (Copepoda: Calanoida) development time and egg production

Abstract

Effects of temperature on aspects of the life cycle and physiology$backslash$nof the copepod Calanus helgolan-$backslash$n$backslash$ndicus (C. helgolandicus) were investigated in the laboratory. Development$backslash$ntimes (DTs) were deter-$backslash$n$backslash$nmined for organisms reared individually at 9, 12 and 158C under saturated$backslash$nfood conditions.$backslash$n$backslash$nWhile animals were successfully reared from egg to adulthood at 12$backslash$nand 158C, at 98C, all the$backslash$n$backslash$nindividuals had died prior to entering NV The cohorts were fed with$backslash$na monoculture of$backslash$n$backslash$n.$backslash$n$backslash$nProrocentrum micans as food saturating conditions. The cohorts were$backslash$nfed with monocultures of$backslash$n$backslash$nProrocentrum micans which should represent saturated food concentrations$backslash$nwith a dinoflagellate diet$backslash$n$backslash$nused in many other experimental studies. However, the monoculture$backslash$nnature of the diet and/or the$backslash$n$backslash$nlaboratory containment conditions may have caused the mortality rates$backslash$nencountered. Impacts of short-$backslash$n$backslash$nterm temperature change on egg production (EP) and hatching success$backslash$nwere also investigated over the$backslash$n$backslash$ncourse of 1 year on individuals collected from station L4 (Western$backslash$nEnglish Channel) and incubated$backslash$n$backslash$nin the laboratory. DTs increased as temperature decreased, with longer$backslash$nDTs at comparable temperature$backslash$n$backslash$nwith those in Thompson’s study [(1982) Growth and development of Pseudocalanus$backslash$nelongatus and$backslash$n$backslash$nCalanus sp. in the laboratory. J. Mar. Biol. Ass. UK, 62, 359–372.]$backslash$nEvidence is presented to$backslash$n$backslash$nsuggest that in this other study a mix of Calanus finmarchicus and$backslash$nC. helgolandicus may have been$backslash$n$backslash$nused. Equiproportional development was observed for the nauplii, but$backslash$nno pattern was defined for the$backslash$n$backslash$ncopepodites. At low temperatures, mortality rates in the incubations$backslash$nwere higher, but adult condition$backslash$n$backslash$nfactor was higher, the longer DTs allowed greater body mass to be$backslash$naccumulated. EP rate was$backslash$n$backslash$ncorrelated with temperature at station L4, but the short-term incubation$backslash$ntemperature did not have a$backslash$n$backslash$nsignificant influence on EP when measured over a short timescale (24$backslash$nh). Egg hatching success also$backslash$n$backslash$ndid not differ between incubations with small temperature differences.

Publication
Journal of Plankton Research
Date