Effect of starvation on the biochemical compositions and respiration rates of ctenophores Mnemiopsis leidyi and Beroe ovata in the Black Sea

Abstract

The proximate biochemical composition and metabolic rates of ctenophores Mnemiopsis leidyi and Beroe ovata from the Black Sea were examined with respect to starvation conditions. Although organic matter content in B. ovata was two times higher than that of M. leidyi (2.51 ±0.53 and 1.14 ±0.17 mg g-1 of wet weight, respectively), these species did not significantly differ in their biochemical composition. In both species protein formed about 80% of the total organic matter, lipids amounted to about 10%. Carbohydrate and amino acids measured separately made up less than 6.5% of the total organic matter. Under experimental starvation (18 days at 16—18°C for B. ovata and 8 days at 12.4°C for M. leidyi), wet weights of both ctenophore species were reduced by 9.4% and 9.3% d-1, respectively. The rate of organic matter decrease was nearly two times lower than that of wet weight being on average 5.9% d-1 in M. leidyi and 5.5% d-1 in B. ovata. There was no trend in percentage of the four major biochemical categories with starvation time. The glycogen content in polysaccharides reached maximum values in freshly collected ctenophores (76.0 ±7.9% in B. ovata, and 86.6% in M. leidyi), but it was reduced substantially (34.4 ±2.7% in B. ovata and 18.3—28.8% in M. leidyi) with starvation. Monosaccharide content, expressed as a percentage of total carbohydrate, decreased from 39.9% to 13.5% in B. ovata, and from 45.8% to 14.3—23.2% in M. leidyi. The relationship between respiration rate (R) and wet weight (W) of individuals during the starvation can be expressed by power function R = R1 Wk (r2=0.85—0.94; P>0.001) for both ctenophore species. On average, k values were 0.95 and 0.83 in B. ovata and in M. leidyi, respectively. By the end of the starvation, metabolic rate per unit wet weight decreased by 33% in B. ovata and 46% in M. leidyi. Organic matter utilization was almost totally explained by respiration of ctenophores in the experiments and exceeded metabolic requirements of studied species by 11% and 15%, correspondingly. As compared with Mnemiopsis, Beroe has better tolerance to starvation which explains to some extent the success of the species survival during prolonged periods of food shortage in the Black Sea conditions.

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“…Spawning organism with medium length about 53 mm (35-70 mm) loses with reproductive products approximately 14.9% of energy from body mass (Anninsky et al, 2005). Ctenophores with body mass 15.4 g loses from 6 to 8% of organic matter per day, from different data, at temperature conditions of 19-21°С (Shiganova et al, 2001;Vostokov et al, 2001).…”

“…Additionally, carbohydrate metabolism apparently influences on ctenophore bioluminescent parameters changes, especially the glycogen contains, which rises in great mature individuals, comparing with juvenile (Anninsky et al, 2005).…”

Variability of the bioluminescence characteristics of the Black Sea ctenophores-aliens in connection with different conditions of nutrition

“…The glycogen content in polysaccharides, reaching maximum in the justcaught organisms (76.0-in B. ovata and 86.6% in M. leidyi) reduced substantially under starvation: to 34.4% -in B. ovata and 18.3% in M. leidyi. Monosaccharide content under starvation of ctenophores decreases from 39.9% to 13.5% in B. ovata and from 45.8% to 14.3% in M. leidyi [22]. Fed ctenophores as M. leidyi, as B. ovata, with ample being fed have maximal concentrations of organic matter; therefore, in the time of light-emission they give the most intensive flash.…”

“…For example, the oxygen consumption intensity in starving individuals decrease considerably during two days [22], due to the energetic parameters of their bioluminescence (amplitude, in particular) decrease too.…”

Invasive ctenophore Mnemiopsis leidyi in Norway

“…Egg production in M. leidyi is sensitive to food availability (Reeve et al, 1989) and the species tolerates starvation relatively poorly (Anninsky et al, 2005;Costello et al, 2012). Relatively high prey abundances are, thus, a prerequisite for population expansion (Costello et al, 2012).…”