PREZANT. ANTIPREDATION MECHANISM OF PHYLLODOCE MUCOSA 







30 pm 



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Figure l. — Upper: An oblique-frontal section of the dorsal 

 parapoidial cirrus of the polychaete Phyllodoce mucosa. This 

 specimen was irritated prior to fixation resulting in the loss of 

 the mucoid secretion produced by mature cirral mucocytes. The 

 vacuolated regions mark the remnants of the mature muco- 

 cytes. The large cirral nerve is also evident. Zenker's fixative, 

 "Azan" stain, m = immature mucocyte; n = neural extension; 

 N = cirral nerve; V = vacuolated mucocyte. Lower: The dorsal 

 parapodial cirrus of a relaxed specimen of P. mucosa in trans- 

 verse section, fixed without excessive mucus loss. The cirral 

 mucocvtes show a beta-metachromatic reaction with toluidine 

 blue HoUande's fixative, toluidine blue stain. M = meta- 

 chromatic mucocyte. 



abundant heterochromatin material. Many im- 

 mature secretory inclusions are present near the 

 epithelial surface as well as subepithelially. The 

 immature secretory droplets occur in a loose for- 

 mation and are surrounded by a dense array of 

 smooth endoplasmic reticulum. The larger, less 

 electron dense, mature secretory droplets occur in 

 tighter, membrane bound accumulations. Figure 

 2 shows a portion of a vacuolated mucous cell 

 bounding a central nucleus. Both the mature and 

 vacuolated secretory cells have numerous, small 

 mitochondria associated with them. 



The smaller, ventral cirrus is histologically and 

 cytologically similar to the dorsal cirrus, and is 

 equipped with oblong mucocytes in both mature 

 and immature stages. Also present is a large cirral 

 nerve and thin longitudinal muscle bands. 

 Melanic pigmentation is not obvious in sections of 

 the ventral cirri. 



DISCUSSION AND CONCLUSIONS 



Many factors influence successful predation. 

 Griffiths (1975) believed that prey abundance and 

 prey size are two of the prime variables affecting 

 predation success but that situations do occur in 

 which predators react to prey characteristics other 

 than body size. These characteristics include phys- 

 ical avoidance by potential prey (Fagade and 

 Olaniyan 1973) which may be chemically 

 mediated by a secretion released by the predator 

 (Mackieetal. 1968: Doering 1976; Mayo and Mac- 

 kie 1976), physical deterrents of the potential prey 

 species such as spines (Hoogland et al. 1956; 

 Bakus 1966), or innate defen.se mechanisms of the 

 potential prey such as toxicity or unpalatability 

 (Thompson 1960; Bakus 1966, 1968; Gibson 1972; 

 Rahemtulla and Lovtrup 1974). An epidermal, 

 mucoid secretion is responsible for the protection 

 of at least some phyllodocid polychaetes from ac- 

 tive predation by some small or juvenile fish. Since 

 phyllodocids are relatively small benthic worms, 

 it is unlikely that many large fish would expend 

 the energy needed to use them as a primary food 

 source; thus only smaller fish would potentially 

 make any notable impact on the phyllodocid popu- 

 lations. 



Russell (1966) tested the palatability of tissues 

 from 48 species of marine organisms with two 

 marine iPelatus quaclrllincntus and Torquigener 

 hamiltoni) and two freshwater {Gambusia affinis 

 and Carassius atiratus) species of fish ranging 

 from 25 to 90 mm. This involved choice experi- 

 ments with the fish simultaneously offered a 

 known palatable organism and a test organism of 

 unknown palatability. The results revealed many 

 unpalatable species which were rejected by the 

 fish. The majority of these tests involved only 

 three or fewer trials and there is little note con- 

 cerning specific reaction of fish to potential prey 

 items. Among the palatable items found by Rus- 

 sell was Phyllodoce malgremi. Phyllodocids, as all 

 other test organisms, were cut to acceptable sizes 

 based on preliminary trials which noted size limits 

 of prey for each fish. Phyllodoce malgremi might 

 indeed be consumed by these particular fish but 

 the limited number oftrials( two per fish) and lack 

 of corresponding worm size data plus the previous 

 treatment of the worms (i.e., sectioned into frag- 

 ments) may have led to misleading data concern- 

 ing palatability. 



Few reports list phyllodocids as a major portion 

 of a fish's diet; however, Wigley ( 1956) did list four 



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