Temperature regulation by the inflorescence of philodendron.

The inflorescence of Philodendron selloum temporarily maintains a core temperature of 38 degrees to 46 degrees C, despite air temperatures ranging from 4 degrees to 39 degrees C, by means of a variable metabolic rate. The heat is produced primarily by small, sterile male flowers that are capable of consuming oxygen at rates approaching those of flying hummingbirds and sphinx moths.

The photoreceptors of the West Indian manatee.

Using light and electron microscopy we found that the manatee retina has both rodlike and conelike photoreceptors in accord with its diurnal behavior pattern. Outer segment disks in both cell types appear to be enclosed along most of their length within the plasma membrane. The synaptic terminals are simple, with small, superficial postsynaptic contacts. The cones have long inner segments, short, conical outer segments and terminals with numerous synaptic ribons and deeply embedded postsynaptic elements. There are two cone subclasses that may subserve color vision. Morphometry shows that there are more ganglion cells of small size ventrally, and that the thickness of the nerve fiber layer there is reduced, suggesting the presence of a specialized visual area in the retina. However, there were no pronounced differences in cone cell density in any of the regions examined.

Cardiomyopathy in stranded pygmy and dwarf sperm whales.

Necropsy and histologic examinations were performed in 23 pygmy sperm whales (Kogia breviceps) and 6 dwarf sperm whales (Kogia simus) that had been stranded singly or in cow-calf pairs along the southeastern coastline of the United States. At necropsy, the gross findings in the adult whales included pale, flabby right ventricles. Microscopically, lesions in the hearts of the whales were characterized by moderate to extensive myocellular degeneration, atrophy, and fibrosis. Similar changes were not seen in 5 of 6 sexually immature whales or in the whale calves. Hepatic changes were consistent with heart failure. The cause of the myocardial lesions was not determined. The systemic effects of failing myocardium probably were a major reason for the stranding of the adult whales.

Structure of northern elephant seal population breeding on San Nicholas Island, California, in 1971.

The structure of the population of northern elephant seals, Mirounga angustirostris, on San Nicolas Island, California, was studied during the 1970 and 1971 breeding season. At the population peak on 31 January 1971, there were 77 males, 306 females, 315 pups, and 6 yearlings on shore. The breeding population was subdivided into 15 groups, containing from 3 to 75 breeding animals. Fourteen of the groups were considered territories defended by individual males, and one group, the largest, was controlled by three males in a social hierarchy. The relatively small size of the San Nicolas population and the large amount of available beach space allowed the existence of numerous small breeding groups. Female elephant seals, although gregarious, apparently prefer to be in small groups when conditions permit it. It is likely that the same males that were territorial would have formed the nucleus of a social hierarchy if space had been limited enough to cause all of the females in the population to congregate in one large group.

Volatile fatty acid concentrations in the digestive tract of the West Indian manatee, Trichechus manatus.

1. Digesta samples were collected from five West Indian manatees, Trichechus manatus, for volatile fatty acid (VFA) analysis. 2. Mean total VFA concentrations were low in the stomach and duodenum (18.6 and 12.3 mM/l, respectively). Mean VFA concentrations were considerably higher in the cecum and colon (220.6 and 307.3 mM/l, respectively). 3. The relative proportions of the individual VFA's shifted from predominantly acetic acid in the foregut to a mixture of acetic, butyric and propionic acids in the hindgut. 4. The VFA concentrations in the manatee are similar to those in the dugong, Dugong dugon, and the green sea turtle, Chelonia mydas. 5. The mean total VFA concentrations indicate that the cecum and colon of the manatee are sites of microbial cellulose fermentation. The contribution of VFAs to the manatees' total energy requirements could not be calculated, but it is probably considerable.

The adrenal gland of stranded whales (Kogia breviceps and Mesoplodon europaeus): morphology, hormonal contents, and biosynthesis of corticosteroids.

Histochemical assays, hormonal quantitation, and steroid biosynthetic studies were carried out with adrenal glands obtained from four stranded whales of two different species (Kogia breviceps and Mesoplodon europaeus), and selected comparisons were made with the results of similar studies of adrenals from terrestrial mammals (man, beef, rat). Histochemical chemical assays of the whale glands for succinic dehydrogenase activity (SDA) showed an intense SDA-positive reaction in the peripheral cortex, and an SDA-negative central medulla, a pattern similar to that found in terrestrial mammals; the whale adrenals, however, demonstrated a markedly pseudolobulated appearance because of a festooned corticomedullary junction. On radioimmunoassay of preformed cortical steroid hormones, corticosterone (B) exceeded cortisol (F) levels by a factor of 3 in the whale adrenals and aldosterone (Aldo) concentrations were 20-100 times lower than in the terrestrial mammals studied. HPLC determinations of preformed medullary catecholamines showed that, contrary to the findings in the terrestrial mammals studied, norepinephrine predominated over epinephrine and the levels of dopamine were much higher in the whale adrenals. In vitro, surviving sections of whale adrenals elaborated B from endogenous substrates, but not F or Aldo. Incubations of subcellular fractions of the whale adrenals with 14C-labeled precursors resulted in the isolation of several steroid intermediates (pregnenolone, progesterone, deoxycorticosterone) as well as the glucocorticoid end-product B, but again without evidence of the formation of either F or Aldo. In keeping with studies in terrestrial mammals, the enzymatic reactions involved in the conversion of [14C]cholesterol to B occurred under aerobic conditions, required the presence of an exogenous NADPH-generating system, and had identical subcellular localization in the whale adrenals. The process of steroid biosynthesis thus appears generally similar in aquatic and terrestrial mammals. It is possible that some of the unusual findings in the whale adrenals studies here may be related to the profound stress of stranding experienced by these marine mammals.