Length-weight regressions of the microcrustacean species from a tropical floodplain

Abstract

Aim: This study presents length-weight regressions adjusted for the most representative microcrustacean species and young stages of copepods from tropical lakes, together with a comparison of these results with estimates from the literature for tropical and temperate regions; Methods: Samples were taken from six isolated lakes, in summer and winter, using a motorized pump and plankton net. The dry weight of each size class (for cladocerans) or developmental stage (for copepods) was measured using an electronic microbalance; Results: Adjusted regressions were significant. We observed a trend of under-estimating the weights of smaller species and overestimating those of larger species, when using regressions obtained from temperate regions; Conclusion: We must be cautious about using pooled regressions from the literature, preferring models of similar species, or weighing the organisms and building new models.Keywords: dry weight, cladocerans, copepods, biomass, secondary productivity.Resumo: Objetivo: Este estudo apresenta as regressões peso-comprimento elaboradas para as espécies mais representativas de microcrustáceos e formas jovens de copépodes em lagos tropicais, bem como a comparação desses resultados com as estimativas da literatura para as regiões tropical e temperada; Métodos: As amostragens foram realizadas em seis lagoas isoladas, no verão e no inverno, usando moto-bomba e rede de plâncton. O peso seco de cada classe de tamanho (para cladóceros) e estágio de desenvolvimento (copépodes) foi medido em microbalança eletrônica; Resultados: As regressões ajustadas foram significativas. Observamos uma tendência em subestimar o peso das espécies de menor porte e superestimar as espécies de maior porte, quando se utiliza regressões pesocomprimento obtidas para a região de clima temperado; Conclusão: Devemos ter cautela no uso de regressões peso-comprimento existentes na literatura, preferindo modelos para as mesmas espécies, ou pesar os organismos e construir os próprios modelos.Palavras-chave: peso seco, cladóceros, copépodes, biomassa, produtividade secundária.

Diversity measures in macroinvertebrate and zooplankton communities related to the trophic status of subtropical reservoirs: Contradictory or complementary responses?

“…Individuals were identified to the lowest possible taxonomic level (Ruttner-Kolisko, 1974Koste, 1978;Reid, 1985;Elmoor-Loureiro, 1997) and were counted in Sedgewick-Rafter chambers (1 mL capacity) until the coefficient of variation of the most abundant species was less than 5%. For the estimation of microcrustacean biomass (copepods and cladocerans), 30 individuals of the most abundant species were randomly counted and measured, and the estimate was calculated using regressions that related dry weight and body length (Bottrell et al, 1976;Azevedo et al, 2012). For rotifers, the biomass was estimated from biovolume by comparing the body shape with approximate geometric shapes (Ruttner-Kolisko, 1977;PintoCoelho, 2004).…”

Tropical cyclone effects enhance limnetic plankton trophic‐level relationships in a subtropical oligotrophic freshwater ecosystem

“…A CCD imaging system was then used to measure the length and width of Rotifera, the length of Cladocera, and the prosomal and urosomal length of Copepoda. To obtain taxon-specific dry weight, we converted the length and width of rotifer species to wet weight and then dry weight (Andersen & Hessen, 1991;Ejsmont-Karabin, 1998;Pace & Orcutt, 1981;Pauli, 1989;Ruttner-Kolisko, 1977), while the lengths of Cladocera and Copepoda were converted to dry weight (Andersen & Hessen, 1991;Bottrell, 1976;de Azevedo et al, 2012;Dumont et al, 1975;Michaloudi, 2005). The dry weights of individual taxa were converted to organic carbon of 0.48, and the ZB was finally counted after accumulating biomass from all taxa (Andersen & Hessen, 1991).…”

Predation by an omnivorous fish and food availability alter zooplankton functional diversity: a microcosm approach

“…For rotifers and cladocerans, measurements were taken according to the shape of the body, and measured between the upper head and the end of the carapace, without the helmet or spines, when present (Ruttner-Kolisko 1977, Hardy 1989. For copepods, body length measurements were taken between the head and the last abdominal segment, except for the spines of the caudal branch (Azevedo et al 2012). The trait of escape response to a predator was classified as low, medium, high and maximum.…”