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

Abstract

Lobate ctenophores were thought to be impos- sible to quantify using standard plankton collection and pre- servation 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 pre- servation in 5 % formaldehyde solution for at least 9 mo. Bulb lengths of Live and preserved specimens were closely corre- lated with ctenophore wet weights. This method is more accurate and convenient than measures of abundance previ- ously used for M. leidyi, and it may be applicable to other species of ctenophores.