PREZANT: ANTIPREDATION MECHANISM OF PHYLLODOCE MUCOSA 



While only one size class of Gasterostetis 

 aculeatus was used, there was no trend between 

 size of the worm and ingestion by the fish ( Table 2 ). 

 The largest as well as some of the smaller worms 

 were not consumed. Sessions Gala, 2b, and 3a all 

 resulted in ultimate ingestion of P. mucosa but 

 involved 34-53 prior ingestive attempts. Of the 

 seven sessions observed with G. aculeatus, these 

 three sessions showed the highest number of at- 

 tempted ingestions prior to consumption. In ses- 

 sion Ga2a, there was a renewed expression of the 

 antipredation mechanism at the start of set B (Ta- 

 ble 2). Thus, sets A and B start with 21 and 20 

 attempts, respectively, followed by a decrease in 

 the number of attempts in set A and consumption 

 in trial 2 of set B. 



In most of the sessions between G. aculeatus and 

 P. mucosa, lack of ingestive attempts seemed to 

 correspond with the presence of investigative re- 

 sponses (Tables 2, 3). These investigations in- 

 volved a close approach to the worm as it sank 

 through the water column, and in some cases a 

 recoil from the worm without evidence of direct 

 contact. In cases where the worm was consumed, 

 the fish exhibited a coughing response which 

 lasted several seconds. Gasterosteus aculeatus 

 readily consumed S. fragilis (Table 4). 



A correlation between the size of the Atlantic 

 silverside, Menidia menidia, and its ability to con- 

 sume P. mucosa is suggested (Table 2). Smaller 

 fish showed little interest in the worms following 

 initial experiences in set A. while the larger fish 

 often consumed the worm very early in the first 

 set. During set A. fish <50 mm initiated several 

 attacks on the phyllodocids. and the worm was 

 easily taken into the buccal cavity before rejec- 

 tion. A rejected worm was often so densely covered 

 with mucus that it would cling to the lower lip of 

 the fish by a mucus thread for several seconds. 

 Menidia menidia also exhibited coughing reac- 

 tions following attempted and succegsful inges- 

 tions. Larger silversides were quick to respond to 

 potential food items released into the aquarium 

 and swiftly sucked them in. In set Mm5f, a 64 mm 

 fish was fed a 23 mm worm. On the first attempt at 

 ingestion by the fish, the worm was quickly taken, 

 whereupon the fish reacted with a coughing re- 

 sponse lasting 45 s. The fish also exhibited a vio- 

 lent lateral head shaking during this time. Fol- 

 lowing this, the worm was totally ejected but the 

 fish continued reacting as described for several 

 seconds. This was the only case where an entire 

 worm was injured prior to ejection. The worm. 



though alive, lost several parapodia and cirri and 

 appeared sluggish. This same worm was again 

 placed in the aquarium with the fish and was 

 again set upon, producing a coughing response 

 lasting 30 s but was not rejected. This fish did 

 postfeed on A. marina and M. menidia showed no 

 hesitation in consuming S. fragilis. 



Only a single size class of sheepshead minnow, 

 Cyprinodon variegatus, was available. This 

 species was exposed to P. mucosa ranging in size 

 from 12 to 24 mm and showed a consistent rejec- 

 tion of each size class (Table 2i. In no case was a 

 coughing reaction noted. Cyprinodon variegatus 

 appeared able to distinguish between P. mucosa 

 and A. marina from short distances (up to 15 cm). 

 The fish showed almost no investigatory behavior 

 after initial ingestive attempts in a given trial but 

 did quickly swim over to feed on A. marina in 

 every case of exposure. Scoloplos fragilis was 

 eaten on the first attempt in each control test with 

 C. variegatus (Table 4). 



The windowpane flounder. Lophopsetta 

 maculata, was the largest fish used in this study. 

 This species rejected the phyllodocids without fail, 

 showing 1 1-31 attempts at ingestion (Table 2) and 

 also exhibited coughing responses following in- 

 gestive attempts. The two sessions with L. 

 maculata, making the greatest number of at- 

 tempts to ingest (Lmlb and 2d) (Table 2), also 

 registered the greatest degree of inquisitiveness 

 (Table 3). There was no relation between size of 

 fish and size of worm in these interactions. As 

 Table 4 shows, there was some hesitation by the 

 larger L. maculata in the control series when of- 

 fered S. fragilis. In all of these control tests but one 

 (Lm2z was terminated), the fish eventually ate the 

 worm, but in Lm2y the fish made 21 attempts and 

 ran into the second trial of set A prior to ingestion. 

 Less than 1 h later, this same fish actively and 

 quickly fed on 12 mm Scolecolepides viridis and 31 

 mm Ner-eis virens. 



Juvenile weakfish, Cynoscion regalis, also re- 

 fused to eat P. mucosa (Table 2). There may be a 

 relationship between the number of attempts to 

 ingest and the size of the worm in these cases 

 (Table 2i. In Crlc and 2e, the worms used were 

 among the three largest (26 and 22 mm, respec- 

 tively), and in both cases the fish showed a violent 

 headshaking respon.se to void its buccal chamber. 

 It thereafter became "nervous" and would not feed 

 on A. marina. In Crla a 24 mm worm was used, 

 and in the entire session only six attempts at in- 

 gestion were made. All the remaining P. mucosa 



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