AN ANTIPREDATION MECHANISM OF THE POLYCHAETE 

 PHYLLODOCE MUCOSA WITH NOTES ON SIMILAR MECHANISMS IN 



OTHER POTENTIAL PREY' 



Robert S- Prezant^ 



ABSTRACT 



The polychaete Phvllodove mucosa exhibits an antipredation response via the extrusion of a repulsive 

 mucoid secretion. The mucus, secreted by largeglandular regions of the dorsal and ventral parapodial 

 cirri, prevents immediate ingestion of the worm by several species of small or juvenile fish. A 

 sipunculid, Phascoleopsis gouldr. a nemertean. Ltneus ruber; and a large flatworm. Stylochus zebra. 

 are also distasteful to some potential predators. Antipredation responses found in some organisms may 

 play an important role in regulating benthic community dynamics by mediating the feeding habits of 

 certain predators during at least some stage of their development. 



Feeding habits of many species offish have been 

 well established, but few studies have extended 

 analyses beyond stomach contents. Results of such 

 research frequently lead to labeling food found in 

 the stomach as "preferred" (Onyia 1973; Smith 

 and Daiber 1977). Reports of selective feeding be- 

 havior based mainly on stomach contents reveal 

 the major types of food eat«n by a fish but do not 

 add substantially to our understanding of the in- 

 teractions between predator and prey. 



Ivlev (1961), discussing selective feeding by 

 fishes, included the role of "constitutional de- 

 fenses" of potential prey species as a mechanism 

 which may contribute to predatory selectivity. 

 Selectivity in food thus entails not only "prefer- 

 ence" but avoidance of specific potential food items 

 (Berg 19791. Bakus ( 1966) considered the possible 

 role of antipredatory responses by some tropical 

 reef inhabitants. He noted that several members 

 of a reef community that are not readily able to 

 retreat into the security of a coral crevice or not 

 naturally protected by skeletal armor are either 

 poisonous, venomous, or distasteful to predators. 

 Acidic secretions from epidermal glands of some 

 opisthobranch gastropods (Graham 19.57; 

 Thompson 1960, 1969) and some nemerteans 

 (Gibson 1972) function as predatory deterrents. In 

 view of the fact thatpredation isa well established 

 cause of quantitative changes in a population of 

 prey species, the ability of some members of a 



'University of Delaware, College of Marine Studies Contribu- 

 tion No. 130' 



^University of Delaware. College of Marine Studies, Lewes, 

 DE 19958. 



M.inu.-icript aiiepti-d April 1979 



FISHERY BULLETIN: VOL. 77. NO. 3, 1980. 



community to thwart extensive predatory crop- 

 ping by using inherent protective devices may also 

 affect community structure. 



An accurate picture of community dynamics 

 demands a closer examination of direct interac- 

 tions between potential prey and predatory 

 species. A start in this direction has been made on 

 a limited number offish. Hynes( 1950), Tugendhat 

 ( 1960), and Beukema ( 1968) examined some of the 

 behavioral feeding patterns of the threespine 

 stickleback, Gasterosteus aculeatus. They found 

 that selective feeding of the stickleback is 

 influenced by degree of satiation and palatability 

 of food. This may have implications extending into 

 the natural environment with regard to seasonal, 

 predatory, or man-induced changes in community 

 structure. In food-limited situations "selectivity" 

 may decrease. The presence of a predatory deter- 

 rent in an organism may thus be functionally 

 operative only in a nonstressed community with 

 nonstarved predators. 



Polychaetes often dominate marine benthic 

 communities (Sanders et al. 1965) and many bot- 

 tom feeding fish eat substantial quantities of these 

 worms (Qasim 1957; Nikolsky 1963; Kislalioglu 

 and Gibson 1977). Obscurance of taxonomic 

 characters due to digestion often prevents iden- 

 tification of prey to species, so food items tend to be 

 listed in terms of higher taxonomic levels (Hynes 

 1950; Kneib and Stiven 1978). This is especially 

 true for soft bodied prey organisms and means that 

 accurate feeding records are often nonspecific and 

 possibly biased relative to the researcher's 

 taxonomic expertise. 



605 



