Quantification of Mnemiopsis leidyi (Ctenophora, Lobata) from formalin-preserved plankton samples

Abstract

Lobate ctenophores were thought to be impossible to quantify using standard plankton collection and preservation techniques. I show that the tentacle bulbs of the lobate species Mnemiopsis leidyi provide a direct measure of numbers and sizes of the ctenophores in formalin-preserved plankton samples. The tentacle bulbs persist intact after preservation in 5 % formaldehyde solution for at least 9 mo. Bulb lengths of Live and preserved specimens were closely correlated with ctenophore wet weights. This method is more accurate and convenient than measures of abundance previously used for M. leidyi, and it may be applicable to other species of ctenophores.