In situ feeding behavior of the copepod Temora longicornis: effects of seasonal changes in chlorophyll size fractions and female size

Abstract

We estimated in situ ingestion rates of females of the calanoid copepod Temora longicornis in Long Island Sound, New York, USA, at roughly weekly intervals, between February and August from 1985 to 1987 using the gut fluorescence technique. Variability in gut pigment content (GPC) and ~ngestion rates (IR) was examined in relation to changes in the concentration of total chlorophyll and of chlorophyll in the > 20 vm size fractions, and changes in body size. Correlations of GPC and IR with chlorophyll concentration were highest for the > 20 Km size fraction and lowest for total chlorophyll. Saturation of GPC and IR was apparent only when phytoplankton > 10 pm or > 20 pm was considered as available food. These results lend support to the notion that the degree to which herbivorous coastal copepods are food-limited may be strongly dependent on the structure of the phytoplankton assemblage Prosome length of female T long~corn~s decreased by almost a factor of 2, and dry weight by a factor of 4, from February to August Correlations between weight-specific GPC, welght-specific IR and chlorophyll concentration in all size fractions were poorer than in the cases of GPC and IR on a per mdlvidual basis However, a multivariate regression analysis indicated that most of the vanance in GPC and IR was explained by the different size fractions of chlorophyll, not body weight. Therefore, the use of weight-specific indices may not always be justified even when variation in body size is pronounced. We suggest that multivanate analysis or other statistical techniques b e employed, instead of weightspecific indices, when body size may be a confounding vanable.

Seasonal variations in body length and fecundity of 2 copepod species: Thermocyclops crassus (Fischer, 1853) and Eudiaptomus drieschi (Poppe & Mrázek, 1895)

“…It was emphasized that total chlorophyll-a does not appear to be a good estimator of food availability, because most copepods feed inefficiently on particles of smaller than 5 µm (Berggreen et al, 1988;Dam and Peterson, 1991).…”

Body size and its variability in the copepodAcartia margalefi(Calanoida) from Lake Acquatina (SE Italy)

“…Temperature, salinity, pollution, and water density showed correlations with size (Conoverj 1956;Deevey, I960;McLaren, 1965;Moraitou-Apostolopoulou & Verriopoulos, 1979;Moraitou-Apostolopoulou et al, 1986). Among biotic factors, food quality and availability, and predator pressure were correlated with the adult body size (Deevey, I960;El Maghraby, 1964;Evans, 1981;Carter et al, 1983;Warren et ai, 1986;Klein-Breteler & Gonzalez, 1988;Dam & Peterson, 1991). Temperature and food conditions are probably the most important factors affecting calanoid body size.…”

Adaptation strategies of copepods (superfamily Centropagoidea) in the White Sea (66°N)

“…The same parameters also may have a strong eVect on copepod body length, DW and organic C content, and such a phenomenon is well known for species with several generations through the productive season, e.g. Centropages, Temora and Acartia (Weisse 1983;Dam and Peterson 1991;Cataletto and Fonda Umani 1994;Gaudy et al 1996;. The general trend is for a larger Wnal body size at colder temperatures.…”

“…The general trend is for a larger Wnal body size at colder temperatures. As an example, Dam and Peterson (1991) observed a negative eVect of increasing temperature on body size for Temora longicornis female PL, but they discuss this as primarily due to decreasing food availability aVected by temperature changes. Therefore, lack of food had a particular greater impact in PL changes.…”

“…The weight and length parameters of this species in the White Sea are in accordance with the data from other areas. Observed female length is 977 § 67 m and DW is 4.72 § 0.48 g and Wt to values of 700-1,200 m length and of 10-40 g DW for T. longicornis from the Long Island Sound (USA) for a temperature Weld between 0 and +22°C (Dam and Peterson 1991). The protein content for Temora varied between 52.4 and 57.6% of DW as observed by Evjemo et al (2003) and 31-54% for a Temora-dominated zooplankton community (Helland et al 2003).…”