FISHERY BULLETIN: VOL. 71. NO. : 



1949a; Gohar and Latif, 1961; Mohsin, 1962; 

 Weatherley, 1963). The protrusible jaws of 

 the cunner have sharp caninelike teeth which 

 are adapted to catching, picking, and scraping 

 animal foods. The strong muscles (hypobranchial 

 and branchiomeric muscles) associated with the 

 mouth can keep the jaws closed tightly, and 

 quick movements of the body could help in 

 detaching sessile organisms from the rocks. 

 The molariform pharyngeal teeth of the cunner 

 serve as a mill to grind up the hard shells of 

 the ingested foods. The probability that well- 

 developed pharyngeal teeth have taken over 

 the mechanical function of the stomach among 

 the stomachless fishes had been suggested 

 previously by Harrington (1942, 1957), Suyehiro 

 (1942), Al-Hussaini (1947b), and Gohar and 

 Latif (1961). 



Ingested foods passed rapidly through the 

 buccal cavity and pharynx in the cunner as 

 in most bony fishes. In the present study, the 

 movement of mussels through the intestine 

 of cunners fed in the laboratory, required 10 to 

 14 hr. Intact and alive mussels were found 

 in all parts of the gut of freshly killed speci- 

 mens both in the field and aquarium. Some of 

 these mussels (less than 16 mm shell length) 

 still were able to resettle. Field observations 

 indicated that the largest individual mussels 

 (over 100 mm shell length) were scattered on 

 the surface of bare rocks 5 to 10 m below the 

 tidal zone. However, the major population of 

 the mussels formed patches or clusters in 

 the intertidal zone. Perhaps cunner play a 

 role in the vertical distribution of mussels. 



No specific area of food storage was found 

 in the cunner; the gut of fish which had been 

 fed all they desired was completely packed with 

 food, and it appeared that the entire intestine 

 can serve as a storage organ while digestion 

 is being completed. The intestinal bulb of 

 stomachless fishes may substitute as a storage 

 organ (Babkin and Bowie, 1928; Barrington, 

 1942; Al-Hussaini, 1947a; Khanna, 1961; 

 Mohsin, 1962; Bullock, 1967). 



Alkaline conditions (pH 7.0-8.5) prevailed 

 throughout the gut in all specimens of cunners 

 examined. In starved controls, there was little 

 variation in pH value observed among regions 



of the intestine. However, in feeding fishes, 

 the pH varied in a random fashion from 

 region to region and showed no significant 

 gradient. Phosphatase tests show a positive 

 reaction for alkaline phosphatase, but negative 

 for acid phosphatase. Intercellular digestion 

 per se in the cunner is exclusively alkaline. 

 Among other stomachless fishes, alkaline diges- 

 tion was observed throughout the gut by Babkin 

 and Bowie (1928), Ishida (1936), Barrington 

 (1942, 1957), Al-Hussaini (1947a), Gohar and 

 Latif (1959, 1961), and Bullock (1967). 



Szarski (1956) discussed the advantages of 

 alkaline digestion in stomachless freshwater 

 fishes. He referred to the high biological value 

 in retention of essential ions, which could also 

 apply to the present species. Cunners feed 

 mainly on shelled animals and the incidence 

 of tooth damage is high. As is evident from 

 having developing teeth along the edge of the 

 old ones on the premaxillary, dentary, and 

 pharyngeal bones. The apparent continuous 

 regeneration and growth of teeth needs large 

 amounts of calcium. The calcium supply can- 

 not be obtained from the calcium carbonate 

 of the animal shells due to the alkaline condi- 

 tion in the gut. Presumably, the calcium source 

 is from the calcium pool of the viscera of the 

 ingested animals. 



ACKNOWLEDGMENTS 



I thank my thesis committee members, H. D. 

 Ahlberg, B. B. Collette, C. A. Meszoely, and 

 N. W. Riser of the Biology Department of 

 Northeastern University. My deepest apprecia- 

 tion goes to N. W. Riser, Marine Science 

 Institute, Northeastern University, for his 

 encouragement and advice from the very be- 

 ginning to the completion of this research 

 and to B. B. Collette, Systematics Laboratory, 

 National Marine Fisheries Service, NOAA, 

 for his critical comments and helj). In addi- 

 tion, I acknowledge heli)ful comments on 

 the contents and organization of this paper by 

 R. H. Gibbs, Jr., Division of Fishes, U. S. 

 National Museum, and J. A. Musick and 

 J. D. McEachran, Virginia Institute of Marine 

 Science. 



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