Dermal Ossification Research Articles

Osteoderms in Anurans

Dermal ossifications-- osteoderms- are more common in anurans than has been gen- erally acknowledged. In the hylid Phyllomedusa bicolor osteoderms are located in the dermis, cover the dorsal surface of the head and body, and are scattered on the lateral and ventral surfaces and the limbs. Each osteoderm consists of a vascularized bony basal plate (0.1 mm thick) from which bony lamellar spines protrude into the epidermis. The dorsal body osteoderms are approximately 3 mm2 in area. Similar osteoderms are present in Phyllomedusa vaillanti and Gastrotheca weilandii. In the pelobatid Megophrys nasuta osteoderms are present in the dorsal body skin and although comparable to the osteoderms of Phyllomedusa in size and shape they are histologically very dif- ferent. Megophrys osteoderms are avascular and composed of calcified collagen bundles in an orderly three-dimensional arrangement. The leptodactylid Hylactophryne augusti also has small bony osteoderms in the skin of the dorsum. They differ from the hylid osteoderms and resemble Megophrys osteoderms in being avascular and having a matrix composed of horizontal and vertical bundles of collagen. Larger dermal bony dorsal plates are present in Lepidobatrachus and Ceratophrys (Leptodactyl- idae) and in Brachycephalus (Brachycephalidae). Anuran osteoderms are structurally different from, and not homologous with, caecilian dermal scales. Given the histological differences among the various anuran osteoderms and the taxonomic diversity (Hylidae, Pelobatidae, Leptodactylidae, and Brachycephalidae), osteoderms appear to have been independently evolved a number of times within the Anura. It is suggested that the term dermal scale be restricted to the bony scale of fishes and caecilians, and osteoderms be used to denote the dermal scutes of anurans and reptiles. Textbooks on vertebrate anatomy clearly state that amphibians, with the

DYNAMICS OF CALCIUM METABOLISM IN NEWBORNS (NB)

The dynamics of calcium (Ca) metabolism in NB are poorly defined although disorders are often encountered. We studied Ca dynamics in NB to improve our understanding of calcium physiology and provide a rational basis for therapy. An injection of radioactive Ca-47 was given to two NB monkeys and Ca-45 administered with each feeding; specific activities were determined in plasma, feces, and urine. Risks of radioisotopes led us to the analogous use of stable Ca-46 and Ca-48 in two low birth weight infants; these were measured by mass spectrometry. Analysis by computer modeling gave the following results in mg/kg/hr. The observed similarities between NB monkeys and humans in their calcium metabolism suggests this laboratory animal is an appropriate model. The exchangeable calcium turnover rate in NB is 14 times the adult rate, and bone calcium dynamics are likewise accelerated. Endogenous fecal Ca loss is also markedly increased in NB despite similarities to the adult in % absorption and urinary excretion. These studies demonstrate the value, safety, and potential of stable isotopes in defining Ca metabolism and disclosing related abnormalities in human infants. We are currently analyzing similar data from infants with short-gut syndrome and isolated dermal ossification.

The Cranial and Appendicular Osteology of Aplodinotus grunniens Rafinesque

Because of the interest in osteology and since the skeleton of the freshwater drum has never been studied, the following deals with the bones of the skull and their relationships in the drum. The skull of Aplodinotus grunniens Rafinesque has been compared with that of the carp (Cyprinus carpio Linnaeus) since the latter is used for class study in a number of laboratories. Another paper will follow in the future which will deal with the cranial nerves and the remainder of the skeleton. The skull of Aplodinotus presents some unusual features, the most notable of which is the deep pitting of the roofing bones, the suborbital bones and the lower jaw for the sensory canals of the lateral line system. A second feature is the presence of two dermal ossifications called scale bones 1 and 2 respectively. The first scale bone aids in holding the posttemporal bone to the epiotic. The second scale bone fits between the posttemporal and the pterotic, filling the space between them so well as to seem as one continuous bone. This may well show how it is possible for a scale to become a dermal element. Between the parietal, epiotic, opisthotic and pterotic bones a large elongate foramen is present. Inside the foramen lies the otolith enclosed in a cartilaginous capsule. The texture of the bones themselves are an interesting feature. Part of them are coarse spongy bone and the rest, shiny, smooth and nearly transparent; some of the bones having both qualities. This latter feature (shininess and smoothness) of the opercular was used by Rafinesque as a diagnostic character. I wish to thank Dr. C. W. Hibbard for the use of specimens in the Museum of Vertebrate Paleontology and Dr. H. H. Lane for securing additional specimens and offering many helpful criticisms and suggestions. The drawings were made by Mr. Walter Yost of the University Museum. DETAILED DESCRIPTION OF BONES Supraoccipital: (Figs. 13, 14) anteriorly it is bounded by the frontals. Laterally it is bounded by the parietal and epiotic. The posterior half of the bone has a ventral wing. -This wing is bounded by the exoccipital. Ventrally the wing comes in contact with the upturned processes of the exoccipitals and rests between them. The median crest does not project very far posteriorly. Exocciptal: (Figs. 11, 14) is bounded dorsally by the epiotic, laterally by the opisthotic, anteriorly by the pterotic and alisphenoid, ventrally by the basioccipital and mesially by the descending wing of the supraoccipital. Both exoccipitals have resting places for the neural arches of the first cervical vertebra. Between these two resting surfaces for the neural arches and the upturned processes is the foramen magnum. Both exoccipitals hold the

Notes and News

Notes and News

Unusual Dermal Ossifications

Unusual Dermal Ossifications

Unusual Dermal Ossifications

Unusual Dermal Ossifications