Digestion in the hippopotamus

The hippopotamus (Hippopotamus amphibius Linn.) has an enlarged stomach, divided into: (a) two anterior diverticula; (b) a large median chamber, and (c) a posterior chamber, secreting gastric juice. Fermentative digestion occurs in (a) and (b). The anatomy and function of the stomach are discussed. Two experiments were performed to compare digestive efficiency with that of ruminants. Exp. 1. In a total collection experiment, chopped grass wasfedtoahippopotamusand five ruminants. Overall digestibility was lower in the hippopotamus, but this may have been due to keeping the animal out of water. Exp. 2. A hippopotamus and two sheep were fed chopped elephant grass (Pennisetum purpureum), digestibility being measured by total collection (in the sheep) and the chromogen ratio method. Dry matter digestibility was similar in all three animals, while digestibility of crude protein was higher in the hippopotamus.     

Thermoregulation in Tunas

Because tunas possess countercurrent vascular pathways servingthe trunk musculature, metabolic heat is retained, and muscletemperatures can considerably exceed that of the surroundingwater (+1° to +21°C). And because tunas have this excess,it is reasonable to suppose they have some means of controllingits magnitude. Tunas must contend with two exigencies whichcan perturb body temperature: changes in water temperature and,in contrast to non-thermoconserving fish, changes in activity.Both can be met by adaptive change in excess muscle temperature.If this could be accomplished in the absence of changes in environmentaltemperature or activity level, this would constitute physiologicalthermoregulation. If excess muscle temperature cannot be alteredsufficiently to acceptable levels, more favorable environmentaltemperatures must be sought or activity levels changed. We wouldconsider this behavioral thermoregulation. High sustained swimspeeds, characteristic of the continuously swimming tunas, requirespecial consideration. Heat production is proportional to approximatelythe cube of swim speed. In order to maintain a slight temperatureexcess at basal swim speeds (1–2 lengths/sec), and yetnot overheat during sustained high speed swimming (>4 lengths/sec),mechanisms are required to conserve heat under the former conditionsand to dissipate it effectively under the latter. In this report,we review published observations other investigators have interpretedas physiological thermoregulation in tunas, describe recentfindings in our laboratory, and suggest some possible thermoregulatorymechanisms.     

Habitat utilization by hippopotamus in the Mara River*

The results are presented of a 2-month study of the Mara River hippopotamus population in the Serengeti National Park and the Maasai Mara Game Reserve. A method for correcting aerial counts of hippos in turbid rivers and based on herd behaviour characteristics is described. There were an estimated 1927 hippos at an average density of 16-1/km in the area censused. The population became more dispersed and the mean group size decreased from thirty to fifteen after a rise in water level. The value of comparisons between populations in various terms of expression of density, and mean group sizes, are discussed. The amount of day living space, defined as areas preferred or utilizable by hippo during the day, and productivity of the food plants are seen to be very important factors in hippo habitat utilization, and as constraints on population increase. Hippo use of the habitat and the effects of hippo on the vegetation at various distances from the river were quantified, and a cycle of vegetational changes suggested which may be associated with the effects of hippo grazing and fire in other parts of Africa. Groups were found to consist of nearly equal numbers of males and females. There was no evidence of territorial behaviour either on land or in the water. A number of observations on social interactions and defaecating behaviour are described and indicate that olfactory communication is very important in interactions between hippos. Hippo society is unstable due to climatic influences, but a dominance hierarchy including males and females exists in the groups. Males appear less firmly attached to groups than females, but a male is normally the dominant animal in a group.     

Thermoregulation in the comfort temperature zone

Under constant adequate temperature conditions (comfortable for a man) the retention of temperature homeostasis was shown to require a continuous functioning of the physiological thermoregulation system to prevent short-term and whole day deviations of the temperature from the physiological level. Under adequate temperature conditions the thermoregulation system was shown to attain its highest sensitivity and accuracy. It is possible that this occurs owing to physiological control over the total body heat content being included into the process of thermoregulation. The data are given on the existence and "structure" of the physiological mechanisms of such a control.     

Skeletal pathology and congenital variations in the Maltese Pleistocene hippopotamus

A first time report is submitted concerning pathological and other changes presented by the post-cranial bones of some 160 specimens of the Pleistocene hippopotamus ( H. pentlandi and H. melitensis ) from Ghar Dalam Cave, near St George's Bay, Birzebbuga, Malta, and now preserved in the Museum overlying the Cave. This material manifests such obvious lesions ab vertebral and metapodial osteo-arthritis. metapodial and phalangeal exostosis, phalangcal cavitation and fracture, ossification of the atlantal ('of the atlas') transverse ligament, as well as such congenital variations as atlantal occipitalization and'fusion'of the second and third cervical vertebrae. Osteo-arthritis is notably prevalent in the thoracic vertebrae, wherein its effects are peculiarly destructive.     

Thermoregulation im Hornissennest

Zusammenfassung Im Nest von Vespa crabro wird im Bereich der Puppen von den weiblichen Imagines (Arbeiterinnen und Königinnen) eine sehr konstante Temperatur von 30,0° C aufrecht erhalten. Zwischen Larvenzellen sind die Tagesschwankungen größer, die Durchschnittstemperatur um 0,4° C niedriger. Die Larven werden von den Imagines nicht gewärmt.In Nestern ohne Imagines läßt sich eine autonome Temperaturregulation durch die Larven nachweisen. Die thermoregulatorischen Bewegungen der Larven werden beschrieben und von den als Hungersignale zu wertenden Bettelbewegungen abgegrenzt.Weibliche Imagines wärmen ältere, pigmentierte Puppen auch außerhalb des Nestes. Dieses Verhalten wird vermutlich durch ein Pheromon ausgelöst. Es werden die Unterschiede in der Thermoregulation gegenüber den Honigbienen und V. orientalis diskutiert.

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Thermoregulation in the nests of hornets

Summary In the nest of Vespa crabro, a very constant temperature of 30° C is maintained by female adults (workers and queens) in the vicinity of pupae. Daily temperature variation between larval cells on the other hand is larger and the average temperature about 0,4° C lower. Larvae are not warmed by the adults.Larvae in nests without adults exhibit an autonomous temperature regulation. In this paper the thermoregulatory movements of larvae are described and distinguished from those normally described as hunger signals and begging movements.Female adults warm older pigmented pupa, even when outside the nest. This behavior is probably stimulated by a pheromone.Differences in thermoregulation are discussed and are contrasted with those of the honey bee and V. orientalis.

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Der Stiftung Volkswagenwerk sind wir für die Förderung dieser Arbeit zu Dank verpflichtet.     

Thermoregulation in the life cycle of nematodes

An unanswered question in the biology of many parasites is the mechanism by which environmental (or external) and intrinsic signals are integrated to determine the switch from one developmental stage to the next. This is particularly pertinent for nematode parasites, many of which have a free-living stage in the environment prior to infection of the mammalian host, or for parasites such as filarial nematodes, which utilise an insect vector for transmission. The environmental changes experienced by a parasite upon infection of a mammalian host are extremely complex and poorly understood. However, the ability of a parasite to sense its new environment must be intrinsically linked to its developmental programme, as progression of the life cycle is dependent upon the infection event. In this review, the relationship between temperature and development in filarial nematodes and in the free-living species Caenorhabditis elegans is summarised, with a focus on the role of heat shock factor and heat shock protein 90 in the nematode life cycle.     

Energetics and Thermoregulation in Chiroptera

This review deals with analysis of current experimental data obtained predominantly by foreign authors on energetics and thermoregulation in many species of the Chiroptera order in connection with their circadian and seasonal hypometabolism due to the habitation temperature conditions, type of nutrition, reproduction, and flying activity.     

Thermoregulation in Antarctic fulmarine petrels

We measured resting metabolic rates at air temperatures between ca. −5 and 30 °C in snow petrels (Pagodroma nivea), cape petrels (Daption capense), Antarctic petrels (Thalassoica antarctica), and Antarctic fulmars (Fulmarus glacialoides). We measured seven age classes for each species: adults, and nestlings that were 3, 8, 15, 28, 35, and 42 days old. Basal metabolic rate (BMR) and thermal conductance (C) of adults averaged, respectively, 140% and 100% of values predicted allometrically for nonpasserine birds. Minimum metabolic rates of unfasted nestlings aged 15–42 days averaged, respectively, 97% and 98% of predicted adult BMR in Antarctic petrels and snow petrels, versus 119% and 126% of predicted in Antarctic fulmars and cape petrels. Nestlings of the southerly breeding snow petrel and Antarctic petrel were relatively well insulated compared with nestlings of other high-latitude seabirds. Adult lower critical temperature (T_lc) was inversely related to body mass and averaged 9 °C lower than predicted allometrically. As nestlings grew, their T_lc decreased with increasing body mass from ca. 14 to 22 °C (depending upon species) at 3 days of age, to −4 to 8 °C when nestlings attained peak mass. Nestling T_lc subsequently increased as body mass decreased during pre-fledging weight recession. Nestling T_lc was close to mean air temperature from the end of brooding until fledging in the three surface nesting species. Accepted: 12 July 2000