Supernumerary median fin-rays in teleostean fishes

Supernumerary fin-rays in the dorsal and anal fins are those that articulate directly with the head of the first proximal radial; they lie in front of the ray serially associated with the first radial. The argument presented here is that just as the number of fin-rays per dorsal and anal radial has decreased in actinopterygian history, so the number of dorsal and anal supernumeraries has decreased in teleosts. It is proposed that D > 3 and A > 3 (more than three dorsal and anal supernumeraries) is the condition primitive for teleosts, and that D2 and A3 are primitive for acanthomorphs.     

Movable head armature in higher teleostean fishes

Synopsis A general pattern of movable head armature, composed of serrations on the borders of the lacrimal and preopercle and of a spine on the opercle, evolved among early acanthopterygians and is retained among many basal percoid families. In the more specialized higher teleostean groups this pattern is modified in various ways. Scorpaeniform fishes develop a suborbital stay with which the lacrimal is rigidly united. Elsewhere lacrimal serrations are generally absent, but in some bottom-resting forms preopercular or opercular armature becomes highly specialized. An association between head armature, fin spines, and changes in locomotion in the development of the acanthopterygian state of teleostean evolution is suggested.     

Jaw structures and movements in higher teleostean fishes

All of the diverse jaw structures in higher teleosts appear to be modifications of a single basal type and are treated as such. Only some of the principal variants are discussed. Though the two jaws act as a coordinated unit during feeding, their movements are different. The upper and lower jaws are discussed separately. In the upper jaw the principal concern is with the various types of premaxillary protrusion and with the secondary development in some groups of a rocking premaxilla. For the lower jaw most of the account is devoted to the repeated differentiation of movements in its anterior and posterior sections. The paper concludes with comments on the jaw apparatus as a functional unit and its evolution in higher teleosts.     

Functional morphology of the caudal skeleton in teleostean fishes

The basic function of the caudal skeleton in teleostean fishes is to support the caudal fin, but its parts contribute to this function in somewhat different ways. The main axis for this support is the upturned terminal end of the vertebral column, which ends at the base of the uppermost principal rays. The uroneural struts just ahead of this axis provide support for it. The parts of the caudal skeleton behind and below this upturned axis, the hypurals and parhypural, not only support the caudal rays but also provide a means for differential movements between the upper and lower parts of the fin base. This basic caudal skeleton varies with the position of the fish in the sequence of teleosten evolution, the way in which the fish uses its caudal fin, and to some extent with the shape of the fin.     

Polyembryony in teleostean fishes: double monstrosities and triplets

The scientific literature pertaining to both naturally occurring and experimentally induced polyembryony in teleosts is surveyed for fish culturists and fisheries naturalists. The survey, covering more than 100 references, provides a chronological historical introduction (17-20th centuries) and a discussion of the causes underlying axial duplication in bony fishes.     

Phosphoglucose isomerase isozymes in teleostean fishes from the Arabian Gulf

Two phosphoglucose isomerases (PGI) with different electrophoretic mobilities have been found in all groups of teleostean fishes studied, with the exception of the Clupeomorpha. PGI proved to be a good taxonomic criterion to differentiate members of the Nemipteridae, Sciaenidae, Platycephalidae and Stromateidae from the other teleost families.     

Two patterns of differentiation in the jaw musculature of teleostean fishes

In its most generalized configuration among modern teleosts the M. adductor mandibulae comprises a single, almost continuous mass of musculature extending from the cheek to the inner surface of the mandible. In more advanced teleosts this muscle is usually divided into sections. Two basically different pathways of differentiation in the cheek part of the adductor mandibulae are dealt with here. One is that in the ostariophysine fishes. The other is represented in at least the great majority of acanthopterygians. Only certain of the differentiated sections are homologous in these two large groups of fishes.     

Nomenclature of cartilaginous elements in the caudal skeleton of teleostean fishes

Nomenclature and abbreviations are proposed for the cartilaginous elements of the caudal skeleton of teleostean fishes. These were developed on the basis of examination of 510 species within 198 families of 31 orders and the determination of the positional relationship between these structures and the bony elements. A review of the most important relative literature is also provided.     

Variations in structure of the lateral-line canal on scales of teleostean fishes

Summary Scanning electron microscopy of lateral-line scales of teleostean fishes demonstrates a wide range of structural variation of the lateral-line canal from a simple direct or slightly oblique perforation to an extended canal with or without simple to highly complex cantilevered extensions acting as covers over the anterior canal opening. Possible important implications of these morphological variations in structure of the lateral-line canal in taxonomy, in scale growth and development, and in lateral line mechanoreception are indicated.     

On the micro-circulatory system of the gills of certain freshwater teleostean fishes

The micro-circulatory system of the lamellae is in the form of a network of more or less parallel blood channels. A row of pillar cells separates two contiguous blood channels. All the pillar cells are situated in the same plane between the upper and lower basement membranes to which they remain fixed in position by means of columns. Histochemical investigations show that the basement membrane as well as the columns are collagenous in nature. Though both basement membranes and the columns are PAS positive (magenta colour), reticulin is not present as they do not respond to silver techniques. The development of new blood channels in the micro-circulatory system of Channa striatus has been studied. They arise as buds from the wall of the pre-existing vessels. There is some evidence to show the possible transformation of the smooth muscle cells of the tunica media of blood vessels into the pillar cells of the micro-circulatory system. Various aspects of the physiology of the micro-circulatory system of the gills have been discussed.     

Microvascular organization of the pseudobranch and carotid labyrinth of two species of air-breathing teleostean fishes

The microvasculature of the pseudobranch in Anabas testudineus and the carotid labyrinth of Heteropneustes fossilis have been studied using scanning electronmicroscopy of Mercox-injected casts. Results confirm differences in origin and basic capillary structure. It is concluded that the pseudobranch is a glandular structure related to functioning of the eye whereas the carotid labyrinth of fishes is concerned with the regulation of fluid pressure and oxygen supply to the brain.