C HAO: DIGESTIVE SYSTEM OF CUNNER 



intestinal epithelium of the cunner in cells 

 which are in direct contact with the food. An 

 extremely strong alkaline phosphatase reaction 

 was found in the intestinal bulb and anterior 

 half of the rectum in the cunner. This reaction 

 seems to be restricted to the free border of 

 the epithelial layer of the intestine and rectum. 

 Evidence of active rectal digestion also has 

 been reported by Babkin and Bowie (1928), 

 Ishida (1936), Al-Hussaini (1949b), Bullock 

 (1967), and Western (1971) in other stomach- 

 less fishes. 



The close association of the pancreas and 

 bile duct in cunner observed in this study 

 agrees with the observations of Gohar and 

 Latif (1959) for another labrid, Jiilis aygitla. 

 Vacuoles (which stained intensively with fast 

 green or with aniline blue) were observed in 

 the supranuclear zone of the columnar epi- 

 thelium of the gallbladder (Figure 17). No 

 reference to this situation was found in the 

 literature, and no data were acquired in this 

 study to determine the function of these 

 vacuoles. 



Feeding Habits 



Gunners are most active in daytime both 

 in aquaria and in the field. Their activity de- 

 creased sharply dui'ing the night, the fish lying 

 against objects on the bottom or hiding in 

 crevices. Torpid behavior was observed during 

 the day when the water temperature in the 

 aquarium fell below 4°C. Bigelow and Shroeder 

 (1953) and Green and Farwell (1971) also 

 noticed that cunners become torpid during 

 winter. 



Gunner reach their greatest inshore abun- 

 dance in summer (July- August). They were 

 absent from the summer habitat from early 

 November to late April. Observations made by 

 SGUBA diving indicate that the offshore move- 

 ments began as the water temperature dropped 

 below 11°G (September 1971). A slight migra- 

 tion of cunner during the winter was postulated 

 by Johansen (1925) and also re])orted by Bigelow 

 and Schroeder (1953) and Green and Farwell 

 (1971). Local fishermen reported the species 

 to be present in deeper (more isothermal) 

 waters in the winter. Juveniles tended to move 



into shallow water in early spring as reported 

 by Johansen (1925). Some juveniles were col- 

 lected during this season in brackish water at 

 the Jackson Laboratory of the University of 

 New Hampshire on Great Bay, N.H. This is in 

 accordance with the statements of Johansen 

 (1925) but is contrary to those of Bigelow and 

 Schroeder (1953). 



Gunners fed on both sessile {Mytilus edulis 

 and Modiolus modiolus) and moving animals 

 (Fu lululus heteroclitus, Gamniarus oceanicus, 

 Neplitys bucera, Nereis vire)is, and Cembra- 

 tulus lacteus) in the laboratory and also acted 

 as scavengers. Gut content analyses (Table 1) 

 indicate that cunner are carnivorous rather 

 than omnivorous in contrast to statements by 

 Johansen (1925) and Bigelow and Schroeder 

 (1953). There was no evidence that cunner 

 actively consume algae in the aquarium even 

 when starved. Algae found in the gut of cunner 

 are always small and undigested and are fre- 

 quently associated with digested epiphytic ani- 

 mals (bryozoans, hydrozoans, and larval mol- 

 luscs). A change of prey was noted between 

 juvenile and adult cunner (Table 1). Juveniles 

 feed mainly on motile crustaceans in the water 

 column, adults on sessile or sedentary animals. 

 A few large, offshore specimens showed a further 

 change in feeding habits. 



In this study almost every adult specimen 

 had mussel shells in the gut. Mussels Mytilus 

 edulis and Modiolus modiolus cover the rock 

 faces in the feeding habitat from which the 

 cunner were taken. Most of the mussels eaten 

 by cunner were less than 2 years old. Many 

 other labrids are also mollusk feeders (Suye- 

 hiro, 1942; Al-Hussaini 1947b; Gohar and 

 Latif, 1959). Randall (1967) recorded the food 

 habits of 11 species of western Atlantic wrasses 

 — all of which, except for the plankton feeding 

 Clepticus parmi — tended to feed on hard- 

 shelled invertebrates such as mollusks, crusta- 

 ceans, and echinoderms. No algae were men- 

 tioned by these authors except that 5 out of 

 50 specimens of HalicIioe)-cs poeciloptcrus had 

 seaweeds (Ulva, etc.) present (Suyehiro, 1942). 



Feeding habits of cunner are related to their 

 jaws, teeth, pharyngeal mill, and also the 

 length of the intestine as reported for other 

 stomachless fishes (Suvehiro. 1942; Al-Hussaini, 



583 



