Amino acid infusions increase renal blood flow (RBF) and glomerular filtration rate (GFR) and stimulate tubular reabsorption in adults. To characterize the effects of amino acids on fetal renal haemodynamics, tubular sodium reabsorption, acid-base homeostasis and plasma renin levels, 11 chronically catheterized fetal sheep aged 121 +/- 1 days (term similar to 150 days) were infused i.v. for 4 h with alanine, glycine, proline and serine (0.1, 0.1, 0.06 and 0.06 mmol min(-1), respectively) in 0.15 M saline at 0.165 ml min(-1). Eight control fetuses were given saline. During amino acid infusion, plasma amino acid levels increased up to 20-fold (P < 0.005). GFR increased by 50 +/- 8 % (P < 0.001); there was only a small transient increase in RBF. Proximal fractional sodium reabsorption fell from 74.6 +/- 2.9 to 55.5 +/- 5.4 % (P < 0.005). Distal sodium delivery increased, but a smaller percentage of this distal sodium load was reabsorbed (P < 0.005). Thus fractional sodium reabsorption fell from 95.5 +/- 0.9 to 81.4 +/- 2.0 % (P < 0.005). There was a large diuresis, natriuresis, kaliuresis and increase in osmolar excretion (P < 0.005). Plasma sodium and chloride concentrations fell (P < 0.005). Plasma osmolality did not change. Plasma renin levels fell (P < 0.05), cortisol levels increased (P < 0.05), and there was a compensated metabolic acidosis. Thus the fetal sheep kidney demonstrated a remarkable functional capacity to respond to amino acid infusion. The increase in filtration fraction and the lack of an increase in RBF suggest that efferent arteriolar vasoconstriction occurred, a very different response from the renal vasodilatation seen in adult animals.

MANY animals restrict their foraging activities to certain times of the day or night, but the Saharan silver ant Cataglyphis bombycina is exceptional in that all foragers leave their underground nest in an explosive outburst confined to a few minutes per day during the hottest midday period. The foraging activity of this 'thermophilic' ant is compressed into a small thermal window by predatory pressure on the one hand and heat stress on the other.

Colonies ofOcymyrmex foreli contained 16–1586 adults of which 4–20% were ergatoid queens the remainder being sterile workers. Each colony contained one inseminated ergatoid queen only and colonies were monogynous. Workers and virgin queens were similar in size and appearance but had distinctive ovaries; queens had significantly more ovarioles than workers, with mated queens having more ovarioles than virgins.

1.1.Cueta trivirgata larvae construct pits in the dry Kuiseb River bed in the Namib Desert.2.2.An art, Ocymyrmex robustior comprises 65.4% of the biomass of prey consumed by the ant-lions.3.3.O. robustior is active between surface temperatures of 27–68°C.4.4.Ant-lions tolerate high body temperatures (LD50 = 53.4°C).5.5.By exploiting the pit microclimate and by digging below the surface during extreme thermal loads, ant-lions can capture prey at surface temperatures of 13–63°C.6.6.These behavioural and physiological adaptations enable ant-lions to maximize the duration of vigilance and hence prey capture success.

Annual cycles of breeding activity were found in 10 species of rock‐frequenting cichlid fishes endemic to Lake Malawi. Nine species of closely‐related Mbuna bred throughout the year but all showed peaks of reproductive activity at times when food was most abundant. Most had a bimodal pattern of reproduction with a major peak in August to October, when plankton blooms were common, and another in February to March, when epilithic algae were plentiful. The smallest Mbuna species studied, Melanochromis joanjohnsonae, had a unimodal pattern, with high levels of reproductive activity extending for six to seven months of the year. Cyrtocara taeniolata, the only non‐Mbuna studied, had a highly synchronized unimodal pattern of reproduction. This species produced the smallest eggs, had the highest relative fecundity and was the only species that employed parental care of free‐swimming young.

Ocymyrmex barbiger is a diurnal scavenger of arthropods in which the number of successful foraging excursions per colony per day increases with daily vapour pressure deficit. It appears that the ants make use of prey items which succumb to thermal and desiccation stress. Running speed is a function of surface temperature but progressively less time is spent searching for prey beyond a critical surface temperature with the result that the optimal search temperature for individual foragers is about 52°C. Maximal foraging activity of colonies occurs at surface temperatures corresponding to this optimal search temperature.

Three sympatric sibling species of Petrotilapia , with similar dietary and macrohabitat requirements, occur near Monkey Bay, Lake Malawi. Males and females of all three species fed selectively on the rocky shores. Males utilized less than 6% of the space they defended as a breeding territory for feeding and although interspecific overlap of territories was considerable, only 2.5% of the feeding space used by territorial males was shared. Males primarily utilized rich food patches which occurred within the territories of highly aggressive Pseudotropheus species, whereas females tended to feed in undefended areas. Although Petrotilapia species are not highly aggressive fishes, there was a well-defined social dominance hierarchy amongst them and it is suggested that feeding-site utilization is dependent on social rank. Inter-and intraspecific differences in feeding-site utilization probably facilitate species coexistence and thus contribute to the maintenance of the high species diversity which is a characteristic of the ichthyofauna of Lake Malawi.

Most aquarium fishes exported from Lake Malawi are cichlids of 10 rock-frequenting genera collectively referred to by their Chitonga name, Mbuna. These fishes provide a classical example of intralacustrine allopatric speciation. The distribution of 196 species is given with notes on habitat preferenda, depth distribution and behaviour. Considerable emphasis is placed on coloration and markings for identification and it is argued that they are important for mate recognition. Brief notes are given on some of the other rocky shore fishes particularly in the genus Cyrtocara. The value of the aquarium fish resource resides principally in its species richness. Most Mbuna species are geographically restricted and stenotopic. The majority occur in the upper 20 m. Mbuna are trophic specialists, but have the ability to feed opportunistically on a variety of food resources. Resource partitioning is effected by different trophic groups. Evidence suggests that species within a particular trophic group which feed upon apparently identical food material, collect it from different microhabitats.

Two species of Labeotropheus are currently recognized, but an earlier study of aquarium specimens caused doubt to be cast upon their specific distinctness. This doubt was removed by a field and laboratory study which showed that L. fuelleborni differed from L. trewavasae morphologically, in coloration, in geographic distribution, preferred habitat and ability to penetrate depth. The two species practise assortative mating. Labeotropheus fuelleborni feeds predominantly from upper surfaces of rocks while L. trewavasae favours under surfaces. Although both species are specialized to crop epilithic algae they also feed secondarily on other food resources (e.g. plankton, insects) when these are available. Gene flow between many populations of rock-frequenting cichlids is restricted by their sedentary nature and apparent inability to cross open water between rocky areas. Consequently, numerous geographic races, incipient species and species are found in the lake. This suggests that intralacustrine allopatric speciation may account for much of the species diversity of cichlids of rocky zones. It is recommended that biologists working on cichlids from Lake Malawi should ascertain the precise location at which their specimens were caught and avoid using aquarium reared fish.

The endemic Lake Malawi cichlid, Petrotilapia tridentiger Trewavas, was found to be a complex of sibling species. The various sympatric species show considerable homogeneity in body form and dentition but are separable on the basis of differences in adult coloration, size at maturity, depth distribution, size and degree of overlap of territories, aggression and courtship. Colour is considered to be important for specific mate recognition in this genus. Examination of wild populations is a valuable, perhaps essential, adjunct to classical taxonomy when dealing with the systematics of sibling species in Lake Malawi.

The number of species of cichlid found to host foreign offspring in mixed broods in Lake Malawi is much greater than originally supposed. It is suggested that all species which show well developed parental behaviour may have foreign fry mix with their broods on occasion. A variety of species of fry were found in mixed broods. These come from two categories of fish: those which apparently do not guard their free swimming fry; and those which have a well entrenched phase of protective care. Although substrate spawners may encourage other fry to join their broods it is argued that foreign young are unwelcome guests of mouthbrooders.Die aantal spesies van die Cichlidae in die Malawi-meer wat vreemde kleintjies in gemengde skole beskerm is baie meer as wat aanvanklik veronderstel is. Daar word voorgestel dat alle spesies met goed ontwikkelde ouersorg by tye vreemde kleintjies tussen hul eie sal hg. Hierdie vreemde kleintjies is afkomstig van twee kategoriS van visse: die wat nie hul vryswemmende nageslag klein vissies oppas nie; en die wat 'n goed gevestigde tydperk van beskerming het. Alhoewel visse wat op die bodem kuitskiet ander klein vissies kan aanmoedig om by hulle kleintjies aan te sluit is dit twyfelagtig of vreemde kleintjies welkom sou wees by mondbroeiers.

Measurements were made of te forces necessary to detach various South African Patella spp. These ranged from 5.18 to 1.95 kg/cm2, with significant differences between the species. P. cochlear Born. had the highest value, followed in sequence by P. argenvillei Kr., longicosta Lam., P. granularis L., P. granatina L., and P. oculus Born. Adhesion is the only mechanism capable of providing forces of this magnitude.