The osteocranium of the catostomid fish, catostomus macrocheilus. A study in adaptation and natural relationship

Abstract

Although suckers are among the commonest of the fresh-water fishes of North America, surprisingly little study has been devoted to their osteology and its remarkable adaptation for suctorial feeding. The most complete description is given by Sagemehl in his 1891 investigations on the cranium of cyprinoid fishes. Since that time, Edwards ('26) has discussed the protractile apparatus of the mouth of catostomid fishes, and Gregory ('33) in his classic work on fish skulls has a short section on catostomids based in part on Edwards' work. Eaton ('35) has comments on the family in a discussion of the evolution of the upper jaw mechanism of fishes. In his study on the bones of the ethmoid region of the fish skull, Starks ('26) has included the catostomids, as has Adams ('40) and Krumholz ('43) in comparative studies of otoliths and Weberian ossicles respectively. Nelson ('48; '49) studied the Weberian apparatus and the opercular series of catostomids specifically. There are also remarks by Ramaswami ('55a; '55b) comparing the sucker skull to some of the cyprinoid fishes he was investigating. No complete study has, however, been made of the skull of suckers.The sucker skull is not only an interesting study in adaptation, but is also of interest in the information it may reveal on the origin and relationship of the eventognathous fishes. MATERIALS AND METHODSThis investigation utilized articulated and disarticulated skulls of mature Catostomus macrocheilus and C. catostomus. The genus may be considered a basic type of catostomid. The descriptions and illustrations are based on C. macrocheilus. There are only a few minor differences between the two species and it is hoped to note these in a future study comparing the osteology of catostomids as a group.Some comparisons were made with skeletal material of Carpiodes carpio, a sucker perhaps more highly modified than Catostomus, and with the squawfish (Ptychocheilus oregonense), a large predaceous member of the closely related cyprinid f amily.2 X-rays of adult suckers were taken and proved of value in orienting the natural position of some of the larger bones. A few alizarin transparencies of juveniles were also made, but the principal reliance for the investigation was on the cleaned skeletons of adults.Fresh and formalin preserved specimens were used to study the jaw musculature.Histological sections of the lips, pharyngeal pad, and cephalic lateral line were stained with hematoxylin-eosin and by Heidenhain's Mallow-azan method. The last gave by far the best differentiation.Unless otherwise specified, the nomenclature for the skull bones is that recently used and up-dated by Harrington ('55). Although his description is for Notropis, a cyprinid, the homology of the bones is not difficult to render. Harrington's work and the series by Ramaswami ('52-55) were frequently referred to. The abbreviations used throughout in the illustrations are also those used by Harrington except where new ones had to be added. These abbreviations should be standardized.The homology and ter...

Heterochronic Variation in the Developmental Timing of Cranial Ossifications in Poeciliid Fishes (Cyprinodontiformes)

“…This is not surprising, considering the complexity of the inductive and morphogenetic interactions that control the development of complex structures such as the vertebrate head (Grobstein, 1967;Hall, 1987). Conservative ossification sequences are also to be expected on functional grounds; the bones first formed are those that serve early functional demands and that are subjected to the greatest muscular stresses (Weisel, 1960;Shaeffer, 1961). For example, among the initial bones to ossify in poeciliids are the maxillae, dentaries, opercles, and cleithra, all of which are associated with jaw movement and respiration (Gosline, 1971).…”

A new Eocene catostomid (Teleostei: Cypriniformes) from northeastern China and early divergence of Catostomidae

“…An anterior cranial fontanelle is observed in †Amyzon [41] and Ictiobus bubalus, Carpiodes carpio (belonging to the Ictiobinae), Cycleptus elongatus, Myxocyprinus asiaticus (referred to the Cycleptinae), whereas it is lacking in the rest of species. Our own observations and the information from the literature suggest the absence of an anterior cranial fontanelle in all catostomines [1,16,19,42,43] , whereas the frontopariental fontenelle is present in all known catostomids except Cycleptus. The fontanelle is present in most species of †Amyzon, but its presence or absence in Vasnetsovia is not clear.…”

Development of the pharyngeal arch skeleton in Catostomus commersonii (Teleostei: Cypriniformes)

“…39B). Weisel (1960) termed this ossification a ''supplementary basihyal''. Catostomids and homalopterids are described by Nelson (1969) as possessing a ''single large ossification also fitting between the ventral hypohyals''.…”

“…Although the early ossification of the skull (Weisel, 1967) and the adult osteocranium (Weisel, 1960) have been described for Catostomus macrocheilus (Cypriniformes: Catostomidae), and the early development of the chondrocranium and splanchnocranium was described as part of a general developmental study for C. commersonii (McElman and Balon, 1980), pharyngeal arch development has not been described in comprehensive detail for a catostomid. We focused on the median elements of the arches in particular because of their phylogenetic variation in number and position in Cypriniformes.…”