Synthesis and turnover rates of four rat liver mitochondrial RNA species

The synthesis and turnover rates of the two 12 S and 16 S mt rRNAs and of the mt mRNAs for subunits I and III of cytochrome oxidase have been determined by measuring the kinetics of incorporation of [3H]uridine in the mtRNA of rat hepatocytes. All the RNA species examined have approximately the same turnover (t1/2 approximately 100 min) and therefore the rate of synthesis, which is about 10-times higher for the rRNAs, seems to be the factor responsible for the different mt rRNA and mRNA steady-state levels.     

The effect of captivity and diet on KLH isoform ratios in Megathura crenulata

Aquaculture of the giant keyhole limpet, Megathura crenulata, may provide a reliable long-term supply of keyhole limpet hemocyanin (KLH) for many promising biomedical applications. However, previous studies have reported a complete loss of the KLH1 isoform under certain cultivation conditions. We examined whether captivity per se and diet caused a significant change in the isoform profile of M. crenulata. Although there was a trend toward a decreasing percentage of KLH1 in some animals, in general isoform profiles were not significantly affected by captivity or dietary limitations. Further, the percentage of KLH1 significantly increased for limpets with previously low levels of KLH1 when fed a supplemental mixed diet. Our results indicate that normal isoform profiles can be maintained in limpets held in captivity even when fed insufficient diets, and that these conditions do not cause a complete loss of either KLH isoform. Notably, the enhancement of abnormally low levels of KLH1 suggests that variability in isoform profiles could potentially be minimized through diet. While there is a need for further research on the factors responsible for the variability of KLH, overall, these results support the premise that culture of M. crenulata may provide a sustainable source of this biomedically important product.     

The influence of rainfall on diet and reproduction in four African rodent species

Arvicanthis nitoticus was found, during two seasons of the study, to begin breeding some two to three months after the start of the rains; at this time weed seeds first appeared in the stomach contents. Breeding continued during the rains and into the early part of the dry season while weed seeds and cereals formed the major part of the diet. Breeding declined during the early part of the dry season, and fat was laid down while weed seeds and cereals were still present but less abundant in the diet. Later in the dry season, breeding ceased and the diet was switched dramatically, first to the leaves and stems of dicotyledonous plants then almost exclusively to grass, and fat deposits were rapidly utilized. Arvicanthis living in an area where cereals were artifically supplied bred almost continuously. Mastomys natalensis also bred when seeds and cereals were most plentiful, but, by ranging widely over open ground, often managed to continue to find these foods, and insects, during the dry season. Supplied cereals failed to produce a reproductive response in Mastomys –instead, unprecedented fat deposits developed. Unseasonal reproduction in this species was, however, observed in an unseasonal wheat crop. Rhabdomys pumilio bred when cereals were plentiful but was also found breeding when its diet was mainly clover–a crop that is noted for its high crude protein content. The herbivorous Otomys angoniensis bred throughout the year and was unaffected by supplied cereals. It seems clear that the food supply of grani-vorous species is dependent on rainfall, and that prolongation of the normal rainy season may generate excess food and cover, resulting in and extended breeding season and unusually large numbers of these rodents.     

The effect of water stress on photosynthetic carbon metabolism in four species grown under field conditions

Abstract. The effect of gradually-developing water-stress has been studied in Lupinus albus L., Helianthus annuus L., Vitis vinifera cv. Rosaki and Eucalyptus globulus Labill. Water was withheld and diurnal rhythms were investigated 4–8d later, when the predawn water deficit was more negative than in watered plants, and the stomata closed almost completely early during the photoperiod. The contribution of ‘stomatal’ and ‘non-stomatal’ components to the decrease of photosynthetic rate was investigated by (1) comparing the changes of the rate of photosynthesis in air with the changes of stomatal conductance and (2) measuring photosynthetic capacity in saturating irradiance and 15% CO₂. Three species (lupin, eucalyptus and sunflower) showed larger changes of stomatal conductance than photosynthesis in air, and showed little or no decrease of photosynthetic capacity in saturating CO₂. Photosynthesis in air also recovered fully overnight after watering the plants in the evening. In grapevines, stomatal conductance and photosynthesis in air changed in parallel, there was a marked decrease of photosynthetic capacity, and photosynthesis and stomatal conductance did not recover overnight after watering water-stressed plants. Relative water content remained above 90% in grapevine. We conclude that non-stomatal components do not play a significant role in lupins, sunflower or eucalyptus, but could in grapevine. The effect of water-stress on partitioning of photosynthate was investigated by measuring the amounts of sucrose and starch in leaves during a diurnal rhythm, and by measuring the partitioning of ¹⁴C-carbon dioxide between sucrose and starch. In all four species, starch was depleted in water-stressed leaves but sucrose was maintained at amounts similar to, or higher than, those in watered plants. Partitioning into sucrose was increased in lupins and eucalyptus, and remained unchanged in grapevine and sunflower. It is concluded that water-stressed leaves in all four species maintain high levels of soluble sugars in their leaves, despite having lower rates of field photosynthesis, decreased rates of export, and low amounts of starch in their leaves.     

Sunning behaviour in ibis (Threskiornithidae) - Observations on four species and conclusions for captivity care

In this article, we describe and compare the sunning behaviour of four ibis species, which represent four different genera (Threskiornis, Plegadis, Geronticus and, for the first time, Eudocimus). Sunning is a genetically fixed form of comfort behaviour. Sunning behaviour can be divided in an initiation and ascending. When sunning, each species has its specific body and wing posture. For each species, we show the typical sunning behaviour and variations of it, also the factors which initiate and influence it.While the other ibis species have similar postures, the genus Eudocimus seems to represent a separated taxon. Sunning behaviour only occured with full sunshine (>11000 Lux) and when temperatures reached a species-specific minimum. Never sunning and drying were combined in any ibis species.Sunning behaviour does not seem to be vital, but it has a strong “wellness” aspect. It can be seen as a hint for good care, as sunning behaviour is shown under optimal conditions. In addition, it is a very attractive behaviour for visitors.     

Differences in penetration routes and establishment rates of four entomopathogenic nematode species into four white grub species

We compared the penetration of the entomopathogenic nematodes Steinernema scarabaei (AMK001 strain), S. glaseri (NC1 strain), Heterorhabditis zealandica (X1 strain), and H. bacteriophora (GPS11 strain) into third-instars of the scarabs Popillia japonica, Anomala orientalis, Cyclocephala borealis, and Rhizotrogus majalis. When larvae were exposed to nematodes for 6-72 h larval mortality and nematode establishment rate and occasionally speed of kill often showed the same pattern within nematode-white grub combinations. But no two nematodes or white grub species had the same pattern for these observations for all white grub or nematode species, respectively. Mortality, establishment, and speed of kill followed a similar pattern for H. zealandica, S. glaseri, and S. scarabaei, but there was no clear relationship for H. bacteriophora. Significant nematode establishment was only observed after at least 48 h exposure in most nematode-white grub combinations. Faster establishment was observed only for H. zealandica in A. orientalis and R. majalis (after 24 h) and for S. scarabaei in P. japonica and R. majalis (after 12 h). Nematode establishment after 72 h in the different scarab species was generally low for S. glaseri (<1.5%) and H. bacteriophora (<3%), higher for H. zealandica (2-5%), and the highest for S. scarabaei (1-14%). However, in another experiment establishment was generally higher after 96h exposure. Nematode penetration sites were determined by comparing nematode establishment in larvae with mouth, anus, mouth+anus, or none sealed with glue. The trends for each nematode species were very similar in the different white grub species. H. zealandica and H. bacteriophora showed excellent cuticular penetration ability but may also penetrate through mouth and/or anus. S. glaseri also penetrated through the cuticle but lower establishment in larvae with mouth or mouth+anus sealed suggested that the mouth is an important penetration site. S. scarabaei showed a preference for the mouth as a penetration site, but it showed some cuticular penetration ability and may also use the anus as a penetration site. The methodology used cannot exclude that cuticular penetration also included penetration through the spiracles. To fully understand the effect of nematode and white grub species on nematode virulence, future studies will have to compare host immune response to the penetrating IJs and the role of the symbiotic bacteria in these interactions.     

The effect of genome and sex on recombination rates in Pennisetum species

The effects of homoeology and sex on recombination frequency were studied in crosses between cultivated pearl millet, Pennisetum glaucum, and two wild subspecies, P. violaceum and P. mollissimum. For the two wild x cultivated crosses, reciprocal three-way crosses were made between the F₁ hybrid and an inbred line (Tift 23DB₁). The three-way cross populations were mapped to produce a female map of each wide cross (where the F₁ was the female) and a male map (where the F₁ was the male). Total genetic map lengths of the two inter-subspecies crosses were broadly similar and around 85 % of a comparable intervarietal map. In the P. glaucumxP. mollissimum crosses, the map was further shortened by a large (40 cM) inversion in linkage group 1. Comparison of the recovered recombinants from male and female meiocytes showed an overall trend for the genetic maps to be longer in the male (10%) in both inter-subspecific crosses; however, analysis of individual linkage intervals showed no significant differences. Gametophytic selection was prevalent, and sometimes extreme, for example 121 in favour of wild alleles in the P. glaucumxP. mollissimum male recombinant population. One of the loci which determines panicle type in cultivated pearl millet and wild relatives, H, was mapped 9 cM from Xpsm812 on linkage group 7 in the P. violaceum cross.     

The effect of starvation on energy turnover and protein metabolism in Ophiocephalus punctatus bloch

1. At 20°C, fish starved for various durations took less food than unstarved fish. At 28°C, 20-day starved fish alone consumed more food.
2. The maximum feeding was during the second ten days at 28°C but in the first ten days at 20°C.
3. Absorption efficiency was unaffected by temperature and starvation.
4. Absorption rate reflected feeding rate.
5. At 28°C the conversion efficiency was high for the ten-day starved fish but at 20°C the 30-day starved fish showe high conversion efficiency.
6. Conversion rate is governed not only by feeding rate but also by conversion efficiency.
7. At 28°C the 20-day starved fish alone compensated for loss of energy, total and protein nitrogen. At 20°C the loss was compensated for by all fish.

     

Effects of UV radiation and water limitation on the volatile terpene emission rates,photosynthesis rates,and stomatal conductance in four Mediterranean species

This study examined the effects of the combination of UV radiation and water limitation on the leaf photosynthesis, stomatal conductance, and terpene emissions of four Mediterranean species. 1-year-old seedlings of these Mediterranean species [Daphne gnidium L., Pistacia lentiscus L., Ilex aquifolium L. and Laurus nobilis L.] were grown under one of three UV treatments (without UV, with UVA, or with UVA + UVB) and two watering regimes (high and low water supply). In general, UV treatments did not affect significantly leaf photosynthesis or stomatal conductance, although UVA and UVB radiation in September led to a reduction in leaf stomatal conductance in D. gnidium. Leaf photosynthesis rates did not differ significantly between the two watering treatments, even though, in three of the species, leaf stomatal conductance was significantly higher among the well-watered plants. The effects of UV on terpene emissions were species-specific; D. gnidium had the highest terpene emission rates when grown under UVA + UVB radiation, which was also true for L. nobilis in September. Overall, UV treatments did not have a significant effect on total terpene emission rates in I. aquifolium, but UVB and UVA in July and September, respectively, reduced emission rates in P. lentiscus. A limited water supply reduced the terpene emission rates in D. gnidium, increased emissions in L. nobilis, and did not affect the emission rates in the other two species.     

Total body water and adaptive water turnover rate in four chromosomal species of subterranean mole rats of the Spalax ehrenbergi superspecies in Israel

Total body water (TBW) and water turnover rate (WTR) were measured in 24 subterranean mole rats comprising four populations, each belonging to a different chromosomal species of the Spalax ehrenbergi superspecies in Israel. The four species range in different climates: humid-cool (2n = 52); semiarid-cool (2n = 54); humid-warm (2n = 58) and arid-warm (2n = 60). TBW, as a percentage of body weight, measured by tritiated water (HTO), was 72.4%±4–7 in 2n = 52, significantly ( P < 005) higher than the similar estimates 61.7%± 7.2, and 59.4%± 5–3, for 2n = 60 and 58, respectively. A comparison of HTO space, as a percentage of TBW, closely approximated TBW, ranging from 97% to 108%. WTR was high, 218.1 and 230.9 ml/kg^0-75/day in the mesic populations of 2n = 58 and 52, respectively. By contrast, WTR estimates were significantly lower , ( P < 0.001), 150.2 and 148.9 ml/kg^0-75/day in the xeric populations of 2n = 54 and 60, respectively. The biological half-life time, T_1/2, was similar and faster, 32.7 and 27.9 hours in the mesic populations of 2n = 52 and 58, as compared with slower, 47.9 and 40.8 hours in the xeric populations of 2n = 54 and 60, respectively. Urine osmolarity in the most xeric northern Negev steppic population of 2n = 60 (737 ± 45 mmol/kg) was significantly ( P < 0.001) higher than in the other species.
We conclude that adaptive radiation in the Spalax ehrenbergi superspecies involves speciation in semiarid (2n = 54) and arid (2n = 60) climates by physiological adaptations of kidney water conservation, along with multiple morphological, physiological and behavioural syndromes of climatic adaptations to increasing aridity (Nevo, 1986).     

Effect of diet on dental development in four species of catarrhine primates

In this study, dental development is described in two pairs of closely related catarrhine primate species that differ in their degree of folivory: 1) Hylobates lar and Symphalangus syndactylus, and 2) Papio hamadryas hamadryas and Semnopithecus entellus. Growth increments in histological thin sections are used to reconstruct the chronology of dental development to determine how dental development is accelerated in the more folivorous species of each pair. Although anterior tooth formation appears to be unrelated to diet, both S. syndactylus and S. entellus initiate the slowest-forming molar earlier than the related less-folivorous species, which supports the hypothesis that dental acceleration is related to food processing. S. syndactylus initiates M2 crown formation at an earlier age than H. lar, and S. entellus initiates and completes M3 at an earlier age than P. h. hamadryas. Similar stages of M3 eruption occur earlier in the more folivorous species; however, the sex of the individual may also play a role in creating such differences. Although the age at M3 emergence is close to that reported for the end of body mass growth in lar gibbons, hamadryas baboons, and Hanuman langurs, M3 emergence may not be coupled to body mass growth in siamangs.     

Feeding rates and absorption efficiencies of four species of sea urchins (genus Echinometra) fed a prepared diet

Four closely related species of sea urchins belonging to the genus Echinometra, Echinometra sp. A (Ea), E. mathaei (Em), E. sp. C (Ec), and E. oblonga (Eo), occur sympatrically but in different microhabitats on Okinawan coral reefs. Feeding rates and absorption efficiencies of the four species were investigated in the laboratory by feeding sea urchins ad libitum a diet prepared from turf algae and agar over a 7-day period. Feeding rates differed significantly among the four species of Echinometra (Ea > Em approximately = Ec > Eo). Absorption efficiencies of protein and lipid did not differ significantly among the four species. Carbohydrate, a major nutrient component in the diet, was absorbed by the four species at significantly different efficiencies (Eo > Ec approximately = Em > Ea), which resulted in similar interspecific differences in absorption efficiencies of dry matter, total organic matter, and energy. The amount of nutrients absorbed from the diet was directly related to the feeding rate, indicating that the increase in absorption efficiency was not sufficient to completely compensate for low feeding rate. The interspecific difference in physiological performance in relation to feeding and absorption is consistent with taxonomic differentiation among the four species.     

The effect of exercise and captivity on energy partitioning, reproductive maturation and fertilization success in adult sockeye salmon

Releasing a population of adult Fraser River sockeye salmon Oncorhynchus nerka from an energetically more expensive non‐feeding natural migration (1089 km, natal groups) and allowing them to sexually mature in either a moderate flow (captive exercise group) or a no flow (captive non‐exercise group) environment resulted in significant differences in body energy densities (MJ kg⁻¹) among groups (ranked: initial natural migrator > non‐exercise > exercise > natal arrivals). Similarly, per cent body lipids were significantly lower in exercise females compared with non‐exercise females, experimentally confirming the central role lipid catabolism has in powering swimming. Although restricting exercise did result in greater body energy reserves at spawning, this did not result in a reallocation of energy to reproduction, as fecundity, egg size and gonad composition were unchanged among the groups. Furthermore, non‐exercise females had delayed maturity, lower egg deposition rates, and were more likely to die prior to egg ovulation than exercise females and natal spawners. Eggs from captive exercise adult females were more likely to survive to the eyed stage than eggs from captive non‐exercise females, but both captive groups had significantly lower egg fertilization success than natal spawners suggesting that confinement stress played a role in some of results presented. There were no significant differences in plasma levels of glucose, lactate, cortisol and reproductive hormones among the groups, but correlations among acute and chronic indicators of stress were significant among individuals. These results indicate that exercise during the late stages of maturation, as might occur normally, may be required for optimizing reproductive maturation and maximizing reproductive success.     

Feeding strategies and diet composition of four Antarctic cnidarian species

The diet of four species of Antarctic cnidarians, two hydroids and two anthozoans, was investigated. One hydroid, Tubularia ralphii, and one anthozoan, Anthomastus bathyproctus, seem to basically consume zooplankton whereas the other hydroid species, Oswaldella antarctica, has a diet mainly based on the fine fraction of seston. The last cnidarian investigated, the stoloniferan alcyonacean, Clavularia cf. frankliniana, feeds mainly on resuspended material. The wide range of diets of these Antarctic cnidarians indicates opportunistic behaviour by feeding on different sources and taking advantage of the available food sources. Data related to low C/N ratios in the sediment and high NO₂ concentrations in areas with dense communities of benthic suspension feeders, along with data on capture rates, lead us to hypothesize that these organisms play an important role in the recycling processes of organic matter in Antarctic benthic ecosystems.