Flavonoid glycosides from Randonia africana Coss. (Resedaceae)

The present study is the first phytochemical report of plants belonging to the genus Randonia. We have isolated nine flavonol-glycosides from Randonia africana distributed into two monoglycosides, six diglycosides and one trioside.     

Evaluation of mean skin temperature formulas by infrared thermography

 To study the reliabiliity of formulas for calculating mean skin temperature (T _sk), values were computed by 18 different techniques and were compared with the mean of 10,841 skin temperatures measured by infrared thermography. One hundred whole-body infrared thermograms were scanned in ten resting males while changing the air temperature from 40° C to 4° C. Local, regional average and mean skin temperatures were obtained using an image processing system. The agreement frequency, defined as the percentage of the calculated T _sk values which agreed with the corresponding infrared thermographic T _sk within ±0.2° C, ranged for with the various formulas from 7% to 80%. In many sites, the local skin temperature did not coincide with the regional average skin temperature. When the local skin temperatures which showed the highest percentage similarity to the regional average skin temperature within ±0.4° C were applied to the formula, the agreement frequency was markedly improved for all formulas. However, the agreement frequency was not affected by changing the weighting factors from specific constants to individually measured values of regional surface area. By applying the physiologically reliable accuracy range of ±0.2° C in the moderate and ±0.4° C in the cool condition, agreement frequencies of at least 95% were observed in formulas involving seven or more skin temperature measurement sites, including the hand and foot. We conclude that calculation of a reliable mean skin temperature must involve more than seven skin temperature measurement sites regardless of ambient temperature. Optimal sites for skin temperature measurement are proposed for various formulas. Received: 2 December 1996 / Accepted: 25 June 1997     

Where sociality and relatedness diverge: the genetic basis for hierarchical social organization in African elephants

Hierarchical properties characterize elephant fission–fusion social organization whereby stable groups of individuals coalesce into higher order groups or split in a predictable manner. This hierarchical complexity is rare among animals and, as such, an examination of the factors driving its emergence offers unique insight into the evolution of social behaviour. Investigation of the genetic basis for such social affiliation demonstrates that while the majority of core social groups (second-tier affiliates) are significantly related, this is not exclusively the case. As such, direct benefits received through membership of these groups appear to be salient to their formation and maintenance. Further analysis revealed that the majority of groups in the two higher social echelons (third and fourth tiers) are typically not significantly related. The majority of third-tier members are matrilocal, carrying the same mtDNA control region haplotype, while matrilocality among fourth-tier groups was slightly less than expected at random. Comparison of results to those from a less disturbed population suggests that human depredation, leading to social disruption, altered the genetic underpinning of social relations in the study population. These results suggest that inclusive fitness benefits may crystallize elephant hierarchical social structuring along genetic lines when populations are undisturbed. However, indirect benefits are not critical to the formation and maintenance of second-, third- or fourth-tier level bonds, indicating the importance of direct benefits in the emergence of complex, hierarchical social relations among elephants. Future directions and conservation implications are discussed.     

Monitoring changes in skin temperature associated with exercise in horses on a water treadmill by use of infrared thermography

Infrared thermography (IRT) was used to assess surface temperature change as an indirect measure of muscle activity and exercise associated changes in blood flow in the working hind limb muscles of horses (n=7) undergoing water treadmill exercise. Three treatments were investigated including the treadmill ran dry (TD), water at the height of the proximal interphalangeal joint (PIP) and water at the height of the carpus (CP). Maximum skin surface temperature was recorded from the region of the semitendinosus muscle during exercise at each water height. There was a significant difference in surface hind limb temperature between exercise on the water treadmill ran dry and with water at the height of the PIP and CP (P<0.0001) with hotter temperatures recorded during the TD treatment. There was a greater increase in surface temperature of the hind limbs from pre exercise to maximum temperature during the PIP and CP treatments when compared to the TD treatment, however, this was not significant (P=0.58). There was no significant difference in surface hind limb temperature found between exercise in water at the height of the PIP and water at the height of the CP. The findings from this study suggest that IRT is able to non-invasively detect muscle activity and associated changes in blood flow whilst horses are exercised on a water treadmill. IRT could potentially be used as an alternative method to assess muscle activity and temperature change in an aquatic environment where existing methods present methodological challenges.     

Comparison between the coat temperature of the eland and dairy cattle by infrared thermography

Little is known about the thermoregulatory response of the eland, a tropical animal often raised in temperate climate. We compared the surface temperature (T_s) of the eland with that of similarly sized Holstein–Friesian dairy cattle at three different ambient temperatures (T_a) to get better evidence about thermal response. The T_s of all body areas (neck, dewlap, trunk, body forepart, barrel, body hind part, forelimb and rear limb) did not differ at T_a 29.2 °C, but at T_a 12.5 °C all the areas of the eland (except the neck) had lower mean T_s than those areas in cattle. At T_a 0.4 °C, only the eland dewlap had a lower T_s and the eland neck had a higher T_s than that in cattle.     

Leadership in elephants: the adaptive value of age

The value of age is well recognized in human societies, where older individuals often emerge as leaders in tasks requiring specialized knowledge, but what part do such individuals play in other social species? Despite growing interest in how effective leadership might be achieved in animal social systems, the specific role that older leaders may play in decision-making has rarely been experimentally investigated. Here, we use a novel playback paradigm to demonstrate that in African elephants (Loxodonta africana), age affects the ability of matriarchs to make ecologically relevant decisions in a domain critical to survival—the assessment of predatory threat. While groups consistently adjust their defensive behaviour to the greater threat of three roaring lions versus one, families with younger matriarchs typically under-react to roars from male lions despite the severe danger they represent. Sensitivity to this key threat increases with matriarch age and is greatest for the oldest matriarchs, who are likely to have accumulated the most experience. Our study provides the first empirical evidence that individuals within a social group may derive significant benefits from the influence of an older leader because of their enhanced ability to make crucial decisions about predatory threat, generating important insights into selection for longevity in cognitively advanced social mammals.     

Effects of silt loading on the feeding and mortality of the mysid Mesopodopsis africana in the St. Lucia Estuary, South Africa

Mesopodopsis africana is an abundant zooplankton species in the currently drought stricken St. Lucia Estuary. The estuary is freshwater-starved, partly because its connection with the large Mfolozi catchment has been discontinued. This is due to the extremely high silt load carried by its waters. A series of in vitro experiments were conducted in May, July, August and December 2006, in order to determine the effect of silt loading on the feeding rate and mortality of M. africana. Mysids were subjected to different sediment concentrations in controlled experiments for a 12-hour period. The turbidity regimes were generated by adding pre-weighed silt concentrations, ranging from 0.03 g/L to 13 g/L, to natural estuarine water. Results in all cases showed a major effect of high silt levels upon food availability, as water chlorophyll losses increased with increased silt concentration. Hindrance in the food collecting abilities appears to have a compounding influence as on two occasions, May and August, ingestion rates decreased with an increase in silt concentration. However, in July, mysid ingestion and clearance rates were higher under increased suspended silt concentrations. In such cases, mysids may be clearing more water under conditions of low food concentration, or alternatively, they may switch to feeding on metazoan prey. In the December experiment, there was no relationship between ingestion rate and silt concentration, possibly because food supplies were sufficient to sustain constant ingestion rates or because mysids increased their clearance rates in the more turbid treatments to compensate for any negative effects of silt. Mysid health also declined, with the mean percentage of survivors decreasing consistently with an increase in silt concentration. Results indicate that the overall effect of increased silt load is negative, and subsequently, increased silt loading in the St. Lucia estuary is expected to have detrimental effects on communities of mysids within the estuary.     

The sexually active states of free-ranging male African elephants (Loxodonta africana): defining musth and non-musth using endocrinology, physical signals, and behavior

Musth in male African elephants, Loxodonta africana, is associated with increased aggressive behavior, continuous discharge of urine, copious secretions from the swollen temporal glands, and elevated androgen levels. During musth, bulls actively seek out and are preferred by estrous females although sexual activity is not restricted to the musth condition. The present study combines recently established methods of fecal hormone analysis with long-term observations on male-female associations as well as the presence and intensity of physical signals to provide a more detailed picture about the physical, physiological, and behavioral characteristics of different states of sexual activity in free-ranging African elephants. Based on quantitative shifts in individual bull association patterns, the presence of different physical signals, and significant differences in androgen levels, a total of three potential sub-categories for sexually active bulls could be established. The results demonstrate that elevations in androgen levels are only observed in sexually active animals showing temporal gland secretion and/or urine dribbling, but are not related to the age of the individual. Further, none of the sexually active states showed elevated glucocorticoid output indicating that musth does not represent an HPA-mediated stress condition. On the basis of these results, we suggest that the term "musth" should be exclusively used for the competitive state in sexually active male elephants and that the presence of urine dribbling should be the physical signal used for defining this state.     

Temperature and salinity tolerance of Mesopodopsis africana O. Tattersall in the freshwater-deprived St. Lucia Estuary, South Africa

Mesopodopsis africana is a key species in the St. Lucia Estuary, Africa's largest estuarine lake. This system is currently undergoing an unprecedented crisis due to freshwater deprivation. A reversed salinity gradient has persisted with hypersaline conditions (> 300) occurring in the upper regions of the estuarine lake. In the context of climate change, rising temperatures will not only push the thermal tolerance limits of estuarine organisms, but increased evaporation from this lake's large surface area will lead to further salinity increases. The present study aims to determine the temperature and salinity tolerance of M. africana, both through in situ studies and the use of laboratory experiments. Results indicate that M. africana is a broad euryhaline species. Mysids were recorded at salinity levels ranging from 2.55 to 64.5 in situ. While experiments revealed a narrower salinity tolerance, acclimation resulted in a significant increase in the tolerance range of this species. It is probable, however, that slower acclimation times may increase survival rates even further, particularly in the higher salinity treatments. M. africana was especially tolerant of the lower salinity levels. In the 20 °C acclimation experiment, LS₅₀ at 1 and 2.5 was only reached after 8 and > 168 h, respectively. Survival at 10 and 40 °C was negligible at all salinity levels. This concurs with field results which documented mysids at temperatures ranging from 16.2 to 30.9 °C. Salinity and temperature increases associated with global climate change may, therefore, have significant implications for these mysid populations, with cascading effects on the higher trophic levels which they support.     

Control and amount of heat dissipation through thermal windows in harbor seals (Phoca vitulina)

Pinnipeds have to cope with the thermoregulatory demands of their amphibious lifestyle. As they are effectively insulated against heat loss in water by their blubber, they have to bypass the blubber for heat dissipation while staying ashore. In previous studies thermal windows on the body of captive phocid seals have been described as areas of heat dissipation in air. In this study we used infrared thermography (IRT) to examine thermal windows in seals hauling out as well as in training situations, where the first refers to a voluntary and the latter to an induced stay on shore. Furthermore we provide an IRT-based estimate of heat loss through thermal windows in pinnipeds. Hauling out seals developed thermal windows within a few minutes irrespective of environmental conditions. By contrast, seals staying on shore on a trainer's command did not develop thermal windows at all. The calculation of heat loss through thermal windows resulted in considerable values in air, but above all in water, which is energetically disadvantageous as it takes up to four minutes to close thermal windows in water.     

Beneath the surface: Profiling blubber depth in pinnipeds with infrared imaging

Infrared thermography (IRT) was assessed as a non-invasive tool to evaluate body condition in juvenile female harbor seals (Phoca vitulina), (n=6) and adult female Steller sea lions (Eumetopias jubatus), (n=2). Surface temperature determined by IRT and blubber depth assessed with portable imaging ultrasound were monitored concurrently at eight body sites over the course of a year in long-term captive individuals under controlled conditions. Site-specific differences in surface temperature were noted between winter and summer in both species. Overall, surface temperature was slightly higher and more variable in harbor seals (9.8±0.6 °C) than Steller sea lions (9.1±0.5 °C). Limited site-specific relationships were found between surface temperature and blubber thickness, however, insulation level alone explained a very small portion of the variance. Therefore, while validated IRT data collection can potentially provide valuable information on the health, condition and metabolic state of an animal, it cannot provide a generalized proxy for blubber depth.     

In situ feeding rates and grazing impact of Mesopodopsis africana O. Tattersall in the St Lucia Estuary, South Africa

Mesopodopsis africana is an important mysid in southern African coastal zooplankton and a key species in the St Lucia estuarine lake, which is currently undergoing severe desiccation owing to freshwater deprivation. M. africana populations through much of the system are consequently under severe environmental stress. This study investigates the grazing dynamics of this mysid species, in relation to autotrophic food availability and other environmental constraints in two contrasting areas of the St Lucia Estuary, Charters Creek, heavily affected by the desiccation process and the Mouth, virtually under unchanged conditions. Gut evacuation experiments were conducted once each during the day and the night. Evacuation rates were consistently higher during the night, ranging from 0.27 to 0.33 h^-1 at Charters Creek and from 1.13 to 1.24 h^-1 at the Mouth. Ingestion rates were, therefore, higher at the Mouth resulting in population grazing impacts of 2.5% of the total microalgal biomass, while the grazing impact at Charters Creek was only 0.5%. The spatial variation in ingestion rates could be attributed to seasonal differences in gut evacuation rates, differences in the mean size of mysids used, or the physicochemical conditions present at the two stations. It is suggested that mysid populations at Charters Creek are predominantly driven by bottom-up forces, initiated by the harsh environmental conditions. Despite the lower ingestion rates exhibited at Charters Creek, results indicate that these mysids are capable of meeting all their energetic requirements from a microalgal diet alone, although they may also utilise a heterotrophic diet.     

The ethnobotany and pharmacognosy of Olea europaea subsp. africana (Oleaceae)

The ethnobotanical uses of wild olive, O. europaea subsp. africana (sometimes referred to as subsp. cuspidata) in southern Africa and in other parts of Africa are reviewed. Chromatographic analyses of secoiridoids (oleuropein and other oleuropeosides) in 25 wild olive leaf samples from 10 localities in South Africa showed substantial amounts of oleuropein (up to 110 mg/g dry weight) and not trace amounts as reported in the literature. Oleuropein is the main active compound in olive leaf, with demonstrated anti-oxidant, anti-microbial, hypolipidemic and hypotensive activities. A comparison with nine cultivated olive leaf samples (subsp. europaea) from six cultivars and two localities showed that commercial olive leaf can be distinguished by the presence of verbascoside, which is absent in wild olive. Extraction methods and solvent systems (TLC and HPLC) were compared, using pure oleuropein (isolated from wild olive leaf and identified by NMR) as an authentic reference sample. The unique peltate scales on the leaves are useful to identify olive leaf raw material (but are the same in both subspecies). The main conclusion is that wild olive leaf is chemically closely similar to cultivated olive leaf and therefore suitable as an alternative source of raw material for olive leaf extract.