Impact of formalin preservation on Pleurobrachia bachei (Ctenophora)

Abstract

Here, we report on the impact of formalin preservation on the physical dimensions of the tentaculate ctenophore Pleurobrachia bachei A. Agassiz collected in the North East Pacific Ocean. Contrary to previously published papers [Oorthuyzen, W., Sadée, C., 1982. Voorkomen en groei van Pleurobrachia pileus en Aurelia aurita in de westelijke Wadddenzee en hun mogelijke rol als predator van platvislarven. Netherlands Institute of Sea Research, Texel; Yip, 1982. A note on the effect of preserving ctenophores in formaldehyde–seawater. Ir. Nat. J. 20 416–419] where a standard 20% shrinkage was applied to whole populations, we found that shrinkage rates are not constant and vary widely with the size of the specimen. A size reduction of 5–80% was observed in individuals ranging from 23 to 5 mm in boreal diameter when alive. The relationship between dry weight (DW) and length is also affected by the preservation process. Previously published biomass data and physiological rates based on preserved samples should therefore be re-examined when population was largely dominated by small size individuals.