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608   Sucker Family-Catostomidae 
be distinguished from suckers by their hardened spinelike rays at the 
front of the dorsal and anal fins. In suckers, the pharyngeal teeth are 
numerous, often comblike, and in a single row on each arch; in min- 
nows, there are fewer than nine teeth per arch, and these may be ar- 
ranged in one to three rows. 
  In suckers, barbels are absent. The scales are cycloid. The mouth, 
usually on the lower portion of the head, is suckerlike; it is protrusible
in many species. The lips are fleshy, with many folds or papillae, or both.
Parts of the first four vertebrae are highly modified into a device known
as the Weberian apparatus-a characteristic shared with minnows and 
many other freshwater fishes. The flesh of most sucker species is filled
with numerous Y-shaped (intermuscular) bones. 
  The pharyngeal teeth in the suckers are diagnostic in a number of spe-
cies. Most have thin, comblike teeth; a few have strong, flat-topped, and
molarlike teeth. Branson (1962) discusses in detail the structure and func-
tion of the pharyngeal teeth. The sucker's food is ground and swallowed 
by means of elaborate spindloid muscles, which move the pharyngeal 
arches against a massive dorsal pad. 
  The pharyngeal pad in many suckers is swollen and thickened ven- 
trally, and it almost fills in the pharyngeal and mouth cavities, leaving
only a narrow slit between the gill arches and the pad. In Carpiodes and
Ictiobus only small animal and plant foods are ingestible. Their pharyn-
geal teeth are small and weak, and the arches accordingly may be paper 
thin and extremely fragile. Large food organisms with hard parts cannot 
easily be accommodated by such a system. 
                                             muscle and fascia 
                                             branchial arch V 
    cartilage                                (pharyngeal arch covered with
membrane) 
    pharyngeal pad                           gill rakers 
                                             symphysis 
                opening into gut 
Cross section just anterior to the arches bearing the pharyngeal teeth in
the smallmouth buffalo 
   Suckers play an important role in the early stages of the food chain.
 They feed largely on aquatic insects and their larvae, and on small mol-
 lusks, algae, and minute crustaceans. They are effective vacuum clean- 
 ers, taking their food from the bottom muds, rocks, plants, and logs, 
 and from the water itself. They are able to find their food by touch and
 taste as well as by sight. Such versatility may be responsible for their
 large numbers. In many Wisconsin waters, the total weight of the suck- 
 ers surpasses the total weight of all the other fishes combined. Their 
 value as a forage fish is well known, and suckers have been stocked in 
 some waters as a food source for large sport fish.