Response in Nematocyst Uptake by the Nudibranch Flabellina verrucosa to the Presence of Various Predators in the Southern Gulf of Maine

Abstract

Aeolid nudibranchs maintain nematocysts sequestered from their cnidarian prey for protection against predators. Selection for nematocyst incorporation is a function of diet and prey choice, but ratios vary among nudibranchs feeding on a given diet, indicating that other factors may be involved. It is proposed that the presence of predators influences nematocyst incorporation. Nematocyst uptake in the nudibranch Flabellina verrucosa collected from the southern Gulf of Maine was examined in response to various potential predators, including Crossaster papposus, Tautogolabrus adspersus, and Carcinus maenas. Nudibranchs in individual flow-through containers feeding on a diet of the hydroids Tubularia spp. and Obelia geniculata were subjected to tanks containing a predator, then their nematocyst distribution was examined. Although most of the changes over the experimental period were attributable to diet, F. verrucosa responded to both T. adspersus and C. papposus by significantly increasing microbasic mastigophore incorporation. No differential uptake was seen with C. maenas. Response was evident in the nudibranchs both for predators present in the collection area and for those with which they had no previous exposure, indicating that F. verrucosa modulates nematocyst incorporation in response to the presence of predators as well as to diet. A coevolution of nudibranchs and potential predators may govern changes in nematocyst uptake.

Acquisition and use of nematocysts by cnidarian predators

“…A later study by Frick (2005) confirmed that the kleptocnidae complement in several species of the genus Flabellina is highly dependent upon the nudibranchs’ prey species, although the proportion of kleptocnida types in the nudibranch may vary from the proportions of nematocyst types in the prey. These results suggest that the nudibranchs respond to the presence of a potential predator either by altering their feeding, which changes their kleptocnidae complement, or by retaining particular nematocysts from their prey (Frick, 2003). Both situations support a defensive role of the kleptocnidae.…”

“…The most convincing evidence supporting a defensive function of nudibranch kleptocnidae emerged from recent research by Kinsey Frick (2003, 2005). Many aeolid nudibranchs retain only a subset of the available nematocyst types from their cnidarian prey (reviewed in Greenwood, 1988), although at least some species may incorporate nematocysts randomly (Martin, 2003).…”

“…Kepner (1943) and Edmunds (1966) suggested that aeolid nudibranchs might retain those nematocysts most effective in deterring predators. To test this idea, Frick investigated how the presence of predators affected the nematocyst complements of the nudibranch Flabellina verrucosa (Frick, 2003). Frick catalogued the kleptocnidae complement in the cnidosacs of individuals of F. verrucosa , and then offered the nudibranchs two types of hydroid prey ( Obelia geniculata and Tubularia spp.).…”

“…Nudibranchs housed in the presence of C. papposus and T. adspersus had a significantly different nematocyst complement than control nudibranchs maintained without the potential predator. In particular, the storage of microbasic mastigophores (a penetrant nematocyst) was favored in both cases (Frick, 2003). A later study by Frick (2005) confirmed that the kleptocnidae complement in several species of the genus Flabellina is highly dependent upon the nudibranchs’ prey species, although the proportion of kleptocnida types in the nudibranch may vary from the proportions of nematocyst types in the prey.…”

Predation on pelagic coelenterates: a review

“…One example is that the predation of the nudibranch Coryphella verrucosa (M. Sars, 1829) is the main factor regulating the populations of the polyps, and hence the release of ephyrae, of Aurelia in the fjords of western Sweden (Hernroth & Grondahl, 1985). There is an extensive literature on the specificity and dynamics of benthic predation and on the incorporation and utilization by the nudibranchs of the cnidae of the prey as protection (Todd, 1981;Harris, 1987;Frick, 2003). Both of those subjects and the production of benthic cysts as scyphozoan protection are outside the scope of the present review.…”