Population ecology of the giant forest hog,Hylochoerus meinertzhageni in Chebera Churchura National Park,Ethiopia

Population, feeding habit, distribution and activity patterns of the giant forest hog (Hylochoerus meinertzhageni) were studied in Chebera Churchura National Park (CCNP), Ethiopia, using line transect sample counts. Population estimate of the hogs was 845 individuals. Among the counted individuals, 42.4% were males and 57.6% were females. Among them, 32.8% were adults, 26.9% were subadults, and 40.3% were piglets. Large sounders of up to 20 individuals were seen during the wet season. They were seen in all habitat types in CCNP with higher abundance in the riverine vegetation. Availability of food, green vegetation cover and water were factors governing distribution of forest hogs in the study area. Grass was the major food item of the hogs (90%), mainly of Panicum sp., Acalypha psilostachya, Cissapelos rigidifolia, Psilotrichum gnaphalobryum and Abutilon ceclii. Feeding was the major activity for which 49.7% of the active daytime was used. Resting (lying down, standing and wallowing) was the next major activity, for which they spent 38.8% of the daytime, followed by other activities (11.5%). Morning and late afternoon activity peaks were more intensive during the dry season. This female‐biased giant forest hog population is expected to sustain in CCNP.     

Western Diet Triggers NLRP3-Dependent Innate Immune Reprogramming

1. Download high-res image (146KB)
2. Download full-size image

     

Adrenalectomy does not affect the nocturnal peak of fos expression within hypothalamic pro-opiomelanocortin neurons

Circulating glucocorticoid (GC) levels are thought to modulate the basal activity of pro-opiomelanocortin (POMC) neurons within the mediobasal hypothalamus (MBH) of the male rat. In a recent study we demonstrated that Fos-immunoreactivity (Fos-IR) was spontaneously induced throughout the dark phase of the light/dark cycle within a large population of these MBH neurons. Here, we have investigated the effect of adrenalectomy on the nocturnal expression of Fos protein within POMC neurons. To this aim, groups of intact (IN), adrenalectomized (ADX) and sham-operated (sham) rats were killed 7 days after surgery (or no surgery) at times when Fos-IR is known to show either nadir (at light offset) or peak (6 h after light offset) values within MBH POMC neurons. Brains were processed for Fos- and/or POMC-immunohistochemistry. The results showed that, at both times studied, 7-day adrenalectomy did not affect the number of POMC/Fos double-stained neurons within the MBH. The rostro-caudal pattern of distribution of such labeled neurons throughout the MBH of ADX rats was also similar to that of IN or sham rats. The present data demonstrate that the nocturnal induction of Fos within MBH POMC neurons is not controlled via the nychtemeral rhythm of secretion of the adrenal gland. Furthermore, this study shows that basal levels of circulating GC do not alter the nocturnal peak of Fos synthesis within POMC neurons.     

Pattern of shift rota modulates oral temperature circadian rhythm and sleep-wakefulness profiles in shift workers

Twenty four shift workers (8 from a steel industry and 16 from a Government hospital) participated in the study. The subjects were instructed to self-measure oral temperature, 4 6 times a day for about three weeks. Sleep quantity and quality for each subject were analysed with the help of an appropriate inventory. The data were analysed by cosinor and power spectrum methods. The frequency of circadian rhythm detection was in the order of 48% in senior nurses, 29% in steel plant workers and 14% in junior nurses. These were also complemented by the results of power spectrum analysis. Present results suggest that rhythms of subjective fatigue and subjective drowsiness are governed neither by oral temperature oscillator nor by the sleep/wake cycle oscillator. The results show that shift rotation pattern chiefly modulates the circadian time structure of shift workers. It is also suggested that the phenomenon of circadian rhythm desynchronization in oral temperature appears to be independent of per day total sleep length.     

Mexican diabroticite beetles: I. Laboratory test on host breadth of Acalymma and Diabrotica spp.

Choice tests were conducted to determine relative degree of specialization of feeding behavior of 11 Mexican diabroticite species in the genera Acalymma and Diabrotica (Chrysomelidae: Luperini). Adult beetles were offered a choice between cotyledons of a non-bitter (not containing cucurbitacin) cucurbit (C. pepo L. var. Crookneck), corn (Zea mays L.), and beans (Phaseolus vulgaris L.). In a second assay a bitter (containing cucurbitacin) cucurbit (C. pepo L. var. Ambassador) was added to the array of plants offered. Neonates of two species of Acalymma and one species of Diabrotica were offered a choice between roots of a non-bitter and a bitter cucurbit, and between a bitter cucurbit and corn.Adult insects showed distinct preferences in the first assay. All Acalymma spp. tested accepted only the non-bitter cucurbit as host, whereas Diabrotica spp. preferred either the cucurbit or the noncucurbit hosts. When the bitter cucurbit was offered together with the other three hosts, all species changed their host choice and significantly preferred the bitter cucurbit. Neonates of all three species tested significantly preferred the bitter cucurbit roots over the non-bitter roots, and the corn roots over the bitter cucurbit.The observation that all Mexican diabroticite species tested left suitable hosts when bitter cucurbits were offered in a choice situation supported the hypothesis that the association between diabroticites and Cucurbitaceae is mediated by plant chemical compounds. For both, the Acalymma spp., which were found to be cucurbit specialists, as well as for the polyphagous Diabrotica spp., cucurbitacin B acted as a strong feeding arrestant which implies that the chemical mediation of this interaction might be an evolutionary conservative trait within the tribe.     

Voracity and feeding preferences of two aphidophagous coccinellids on Aphis citricola and Tetranychus urticae

Voracity and feeding preferences of adult Coccinella septempunctata L. and Harmonia axyridis Pallas (Coleoptera: Coccinellidae, tribe Coccinellini) were evaluated in the laboratory on a common prey, the spirea aphid, Aphis citricola van der Goot (Homoptera: Aphididae), and on the twospotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae), a prey previously unrecorded for these two predators. The experiments were carried out in the laboratory on apple saplings (Malus domestica Borkhausen). Adult males and females of H. axyridis consumed significantly more mites than adults of C. septempunctata. For H. axyridis, males consumed 41.3 spider mites in 24 h and females 48.4, whereas for C. septempunctata males consumed 14.1 prey and females 15.2. The consumption of spirea aphids by the males was similar for the two species. Consumption by the females was significantly greater for H. axyridis (46.5) than for C. septempunctata (22.2). The two coccinellids showed a significant preference for A. citricola in the presence of T. urticae. This preference was more pronounced for C. septempunctata. The total number of prey consumed and the percentage of exploited biomass decreased significantly for C. septempunctata and stayed relatively constant for H. axyridis as the number of mites increased in the prey ratio. Our results suggest that T. urticae is only an alternative prey for both predators, and that H. axyridis should be more efficient than C. septempunctata in a prey assemblage with aphids and mites.     

Adult feeding and lifetime reproductive success in the parasitoid Aphytis melinus

The diet of adult females of the parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) includes host insects and sugar-rich foods such as nectar and honeydew. We compared the contributions of host feeding to longevity and fecundity in A. melinus females in the presence and in the absence of honey meals. First, we assessed the longevity of females that were not allowed to oviposit. While the longevity of females fed honey was significantly increased by host feeding (median ages were 30.5 days for host-fed females and 17 days for females not allowed to host feed), the lifespan of parasitoids not fed honey did not exceed 3 days for any individual and there was no effect of host feeding on longevity in this group. In the second set of experiments, we assessed the fecundity and longevity of females allowed to oviposit. We conducted two experiments, one in which honey was continuously available, and one in which honey was not available. In both experiments, daily observations were made of females that were either allowed to host feed or manually prevented from host feeding. In the presence of honey, host feeding significantly increased both fecundity and longevity, and in the absence of honey, parasitoids died within 2 days and host feeding had no significant effect on either fecundity or longevity. The lifetime fecundity of females fed honey but not hosts exceeded the initial egg complement by 60% on average. Approximately one host per day was used for host feeding whether honey was supplied or not, and each host-feeding meal contributed approximately 3.9 eggs to the lifetime fecundity of honey-fed females. In the last experiment, we compared the rate of egg resorption over a 36-h period in A. melinus females that were deprived of hosts and either fed honey or starved. While no egg resorption was detected in honey-fed females over this time period, starved females resorbed approximately 9 eggs. Thus, the availability of a sugar-rich food interacts strongly with host feeding in influencing longevity and fecundity and has a strong direct effect on egg resorption.     

Melon resistance to the aphid Aphis gossypii: behavioural analysis and chemical correlations with nitrogenous compounds

In the melon, the Vat (monogenic, dominant) resistance gene governs both an antixenotic reaction to the melon aphid Aphis gossypii Glover (Homoptera, Aphididae) and a resistance to non-persistent virus transmission, restricted to this vector species. We investigated the behavioural features and tissue localisation of the antixenosis resistance by the electrical penetration graph technique (EPG, DC system). We also compared the chemical composition in amino compounds and proteins of the phloem sap collected from two isogenic lines of melon (Cucumis melo L.), carrying the Vat gene or not. All behavioural and chemical data indicated that this resistance is constitutive. EPG analysis clearly showed that access to phloem, although delayed by alterations in pathway activities, was not impaired in terms of frequency of access or initiation of feeding. The most striking feature was, however, a very reduced duration of ingestion from phloem of resistant plants, making this compartment one of the tissues where the effects of the Vat gene are unambiguously expressed. This was confirmed by clear differential activity of phloem extracts in artificial no-choice bioassays. Chemical analyses have shown that phloem saps from the two isogenic lines were extremely similar in profiles of ninhydrin positive compounds, and contained a low total amount of free amino acids (less than 10 mM). Out of more than 40 distinguishable peaks in the chromatograms (protein and non-protein amino acids, as well as small peptides), only five differentiated the two genotypes. Two of them were increased in the resistant genotype: glutamic acid and a major unknown peak, probably a non-protein amino acid (different from pyrazolyl-alanine, a Cucumis-specific amino acid). The three others were depressed in resistant plants, and included the sulphur amino acid cystine and a peptide peak partly composed of the cysteine-containing peptide glutathione (reduced form). Sap collection also showed that phloem exudation rates, as well as total protein and glutathione levels, were depressed in phloem sap from resistant plants. Such data are all indicative of a modified phloem-sealing physiology, linked to sulfhydryl oxidation processes, in plants carrying the Vat gene. The originality of the mechanism of Vat resistance to aphids is discussed.     

Young whale sharks, Rhincodon typus, feeding on a copepod bloom near La Paz, Mexico

Seven small (3.2 to 5.2 m total length) whale sharks were observed suction feeding on patches of surface plankton in the Bay of La Paz within 1 km of shore and 2 km N of the phosphate dock at San Juan de la Costa, on 1–2 November 1993. The sharks were photographed and videotaped from the boat and by snorkelers in the water. When actively feeding the shark turned its head from side to side, part of the head was lifted out of the water, and the mouth opened and closed 7 to 28 times per minute (x=17, N=13). These suction gulps were synchronized with the opening and closing of the gill slits. This feeding behavior occurred only in the patchy areas of densely cloudy water, a layer 10 to 30 cm thick at the surface containing an immense concentration of copepods, 95% of which were identified as Acartia clausi. Remoras accompanying the whale sharks also fed on the plankton bloom. This revised version was published online in July 2006 with corrections to the Cover Date.     

Size-selective predation by the cleaner fish Labroides dimidiatus

A comparison of the size-frequency distribution of parasitic gnathiid isopod larvae in the diet of the cleaner fish Labroides dimidiatus and on six host fish species ( Chlorurus sordidus, Ctenochaetus striatus, Hemigymnus melapterus, Scolopsis bilineatus, Siganus doliatus, Thalassoma lunare ) was made on one occasion. The comparison was repeated with Hemigymnus melapterus on three occasions and between two islands in Australia. L. dimidiatus selected larger gnathiids at all times at Lizard Island but not at Heron Island. Size-selective predation by L. dimidiatus suggests any potential effect of cleaner fish on parasites may vary according to the size of parasite. However, this effect appears to vary spatially.