Phosphoglycerate kinase pseudogenes in the tammar wallaby and other macropodid marsupials

Phosphoglycerate kinase (EC 2.7.2.3; PGK) exists in two forms in marsupials. PGK1 is an X-linked house-keeping enzyme, and PGK2 is a mainly testis-specific enzyme under autosomal control. We have used PGK1 probes derived from two closely related species of macropodid marsupials (kangaroos and wallabies) to demonstrate the existence of a large family of pseudogenes in the tammar wallaby (Macropus eugenii). Over 30 fragments are detectable after Taq digestion. We estimate that there are 25–30 copies per genome. Most are autosomally inherited and are apparently not closely linked. Only two restriction fragments that appeared to be sex linked could be detected. Varying degrees of hybridization of fragments to the probes suggest different levels of homology, and hence different ages of origin. The existence of two PGK1 homologous restriction fragments from the X and a large number from the autosomes was also demonstrated by somatic cell hybridization for two other macropodid species, the wallaroo (M. robustus) and the red kangaroo (M. rufus). These results are compared with those from human and mouse, and it is suggested that the propensity of PGK1 to form pseudogenes is an ancient (130 MYR BP) characteristic of mammals. The high level of polymorphism detected in the tammar makes these PGK1 probes potentially useful for measuring genetic variability in this species and other macropodids.     

Water relations of five tropical tree species on Barro Colorado Island,Panama

Summary Diurnal curves of xylem pressure potential (P) and leaf conductance (C) were measured for five tree species of the lowland tropical forest on Barro Colorado Island, Panama. Measurements were taken just before and just after the beginning of the rainy season. The species studied were: Cordia alliodora, Faramea occidentalis, Heisteria concinna, Macquira costaricana, and Trichilia cipo.For all species, predawn (base P) and daytime values of P increased markedly after the beginning of the rainy season. Diurnal patterns of C were quite diverse. C. alliodora showed a decline in C during the day whereas F. occidentaus, H. concinna, and M. costaricana showed little change. Conductance of the last three species was lower before the first rains. T. cipo exhibited more complicated behavior for P and C. Before the rainy season, low values of base P and midday P were observed (-26 bars and-39 bars, respectively). Conductance was also low. After the first rains, base P increased to-4 bars. At this time, midday P and C appeared to respond to vapor pressure deficit (VPD), being less on a day with high VPD than on a day with low VPD.     

Energy expenditure and protein turnover in three species of wallabies (Marsupialia: Macropodidae)

Summary Relationships between basal and fed metabolic rates and whole-body protein turnover rates were examined in three species of wallabies, the red-necked pademelon (Thylogale thetis), parma wallaby (Macropus parma) and tammar wallaby (M. eugenii).There were no significant differences among wallaby species in basal metabolic rate (BMR) which was 30% below eutherian mammals. However, the fed metabolic rate of the tammar was lower than that of the other two species (P<0.05), as was the protein turnover rate (P<0.01) which is consistent with its lower voluntary feed intake and with its lower maintenance nitrogen requirement.Protein turnover rates in the wallabies were 23–47% lower than in eutherian mammals. Similarly, protein synthesis made a lower contribution to fed metabolic rates in the wallabies (7–8%) than in eutherians (17–25%).Thus, compared with several eutherian species, macropodid marsupials have low rates of both energy and protein metabolism, but within the macropodids there is not necessarily a close link between basal metabolic rate and whole-body protein turnover.Abbreviations BMR basal metabolic rate - DEE daily energy expenditure - EE energy expenditure - LSD least significant difference - RQ respiratory quotient     

Sex,reproductive cycle and variations in the fecundity of the family schilbeidae (Osteichthyes : Siluriformes) in Lake Kainji,Nigeria.

The sex, reproductive cycle and variations in the fecundity of the family Schilbeidae (Osteichthyes : Siluriformes) in Lake Kainji, were investigated. Sexual differences in size and morphology were found to exist in all species. Sex ratio varied with species and season. There were more females than males in the population. Size at maturity varied from species to species with the males attaining maturity at a slightly lower length than the females. Breeding condition was attained mainly during the rains in Eutropius niloticus, Schilbe mystus and Siluranodon auritus and in the dry and rainy seasons in Physailia pellucida. Spawning occurred once during the breeding season in E. niloticus and S. mystus; and more than once during the prolonged breeding season in P. pellucida. Condition factors did not show any correlation with maturation of gonads. Fecundity was found to vary from species to species.     

Histology,ultrastructure, and seasonal variations in the bulbourethral gland of the African straw-colored fruit bat Eidolon helvum

We studied the morphological characteristics and seasonal changes of the bulbourethral gland of Eidolon helvum in a typical African tropical environment. Forty-eight bulbourethral glands were examined using gross anatomical, histological, histochemical, and ultrastructural techniques during the early rainy, late rainy, and peak dry seasons. The pear-shaped bilateral bulbourethral glands were located extra-abdominally in the inguinal region. Trabeculae from the capsule divided the parenchyma into numerous lobules of tubuloalveolar glandular acini. The mucosa was covered by a simple columnar epithelium consisting up of principal secretory cells, columnar dense cells and basal cells, which were progressively pronounced during the dry season. The principal cells contained eosinophilic granules, which were PAS positive while the dense cells did not show affinity for the stains. The mean gross weights, acini diameters, and epithelial heights were greater during the rainy season than the dry season. Ultrastructural evaluation showed that the cytoplasm of the principal cells contained well-developed Golgi complexes, rough endoplasmic reticulum, mitochondria, and secretory vesicles of varying electron densities and sizes. The secretory vesicles were numerous during the early rainy season, decreased during the late rainy season and were scanty during the peak dry season. The simple columnar epithelium observed during the rainy season was replaced by an undefined stratified epithelium during the dry season, and this was associated with cellular degenerations and regenerations. In conclusion, E. helvum has a typical mammalian bulbourethral gland, with a unique cell type, the dense cell whose functions are not well-understood. The gland exhibits cyclical seasonal variation in structure and secretory activity; being active during the early rainy season (breeding season), and showing the lowest activity during the dry season (non-breeding season). Glandular epithelial cell renewal occurs during the dry season in preparation for the next breeding season.     

Disturbance and Seasonal Dynamics of Mycorrhizae in a Tropical Deciduous Forest in Mexico1

Mycorrhizal fungi were sampled in a deciduous tropical forest on the Pacific coast of Mexico during different seasons and in natural treefall gaps and pastures. All 12 plant species sampled in the forest were arbuscular mycorrhizal. The percent root infection and spore production were closely related to the phenology of the plants. Most tree species and all herbaceous species had the highest infection in the summer rainy season, but two species, Opuntia excelsa and Jacquinia pungens, had highest infection in the dry season. Unusually high rainfall during the dry season was associated with increased infection but not increased spore production. Spore density was low for all species at all sample times, except at the beginning of the July 1993 rainy season in, when we observed up to 28 spores/g soil. The percent cover of shrubs or herbs did not increase in gaps after two years, and we observed no colonizing seedlings. No plant species with cover higher than 2.7 percent occurred exclusively in gaps or forest. The percent mycorrhizal infection did not differ significantly between gaps and forest. Spore counts were as high in the gaps as in the forest in two of the three gaps but lower in the third gap. The lack of significant response of plants in these gaps after two years differed from the rapid response in tropical rainforests. It is likely related to the small size of the gaps and to light infiltration to the forest floor. Pastures were dominated by two species of exotic grasses and one species of mycorrhizal fungus, whereas forests had 15 fungal species. The slow regrowth of vegetation in gaps was not limited by mycorrhizal fungi, since they were still abundant after the treefalls, but recovery in pastures could be affected by low fungal diversity and dominance of grasses.     

Root and microbial biomass dynamics under the canopy of the desert shrub Zygophyllum dumosum

Summary A study was done to evaluate the influence of soil moisture and rainfall on root and microbial biomass production under the canopy of the desert shrub Zygophyllum dumosum. During the study period the root biomass production increased following the early rains but subsequently declined, remaining fairly constant thoroughout the season. In contrast microbial biomass and soil organic matter increased during the rainy season and declined with the onset of the dry summer period. Based on our results we suggest that the moisture event and not the amount and the organic matter content regulate root and microbial biomass production at the 0 to 10 cm soil layer.Contribution of the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. paper no. 2617-E, 1989 series     

Differing impact of a major biogeographic barrier on genetic structure in two large kangaroos from the monsoon tropics of Northern Australia

Tropical savannas cover 20–30% of the world's land surface and exhibit high levels of regional endemism, but the evolutionary histories of their biota remain poorly studied. The most extensive and unmodified tropical savannas occur in Northern Australia, and recent studies suggest this region supports high levels of previously undetected genetic diversity. To examine the importance of barriers to gene flow and the environmental history of Northern Australia in influencing patterns of diversity, we investigated the phylogeography of two closely related, large, vagile macropodid marsupials, the antilopine wallaroo (Macropus antilopinus; n = 78), and the common wallaroo (Macropus robustus; n = 21). Both species are widespread across the tropical savannas of Australia except across the Carpentarian Barrier (CB) where there is a break in the distribution of M. antilopinus. We determined sequence variation in the hypervariable Domain I of the mitochondrial DNA control region and genotyped individuals at 12 polymorphic microsatellite loci to assess the historical and contemporary influence of the CB on these species. Surprisingly, we detected only limited differentiation between the disjunct Northern Territory and Queensland M. antilopinus populations. In contrast, the continuously distributed M. robustus was highly divergent across the CB. Although unexpected, these contrasting responses appear related to minor differences in species biology. Our results suggest that vicariance may not explain well the phylogeographic patterns in Australia's dynamic monsoonal environments. This is because Quaternary environmental changes in this region have been complex, and diverse individual species’ biologies have resulted in less predictable and idiosyncratic responses.     

Carbon isotope analysis shows introduced bovines have broader dietary range than the largest native herbivores in an Australian tropical savanna

Australian savannas lack native megaherbivores (>500 kg body mass), but since the commencement of European colonisation in the 19th century bovine livestock, such as cattle (Bos sp.) and water buffalo (Bubalus bubalis), have established large feral populations that continue to geographically expand. The largest extant native herbivores are marsupials in the family Macropodidae (henceforth 'macropods': common wallaroo, Osphranter robustus [c. 40 kg]; antilopine wallaroo, O. antilopinus [c. 35 kg] and agile wallaby, Notamacropus agilis [c. 20 kg]). These species occur at low densities, with evidence that some species are in decline, the cause of which remains uncertain. We tested the hypothesis that bovines and macropods compete for nutritious forage in the North Kimberley, Western Australia by using carbon isotope analysis of feral cattle and native macropod dung (as a proxy for the relative contribution of C₄ grass to their diet) and nutrient analysis of standing herbaceous biomass. Grass consumption varied between macropod species and was highest in larger wallaroo species and lowest in the smaller agile wallaby reflecting its broader diet. Grass consumption by wallaroos was maximal on fertile sites. The relative abundance of grass in the diet of cattle was lowest in the middle of the dry season with an interaction between fire and substrate fertility where grass consumption was highest on fertile sites, particularly those recently burnt. Grass consumption by cattle and wallaroos was negatively correlated with fibre content of live biomass, which was lowest on fertile and burnt sites. Introduced bovines shift their diets to non‐grasses as quality of herbaceous biomass declines with increasing fibre content, and by contrast, the largest macropod herbivores do not have this dietary flexibility. We conclude a plausible mechanism for the success of bovines and the decline of large macropods in Australian savannas is competition for nutritious grass that is abundant immediately after fire.     

Chromosome evolution in kangaroos (Marsupialia: Macropodidae): cross species chromosome painting between the tammar wallaby and rock wallaby spp. with the 2n = 22 ancestral macropodid karyotype.

Marsupial mammals show extraordinary karyotype stability, with 2n = 14 considered ancestral. However, macropodid marsupials (kangaroos and wallabies) exhibit a considerable variety of karyotypes, with a hypothesised ancestral karyotype of 2n = 22. Speciation and karyotypic diversity in rock wallabies (Petrogale) is exceptional. We used cross species chromosome painting to examine the chromosome evolution between the tammar wallaby (2n = 16) and three 2n = 22 rock wallaby species groups with the putative ancestral karyotype. Hybridization of chromosome paints prepared from flow sorted chromosomes of the tammar wallaby to Petrogale spp., showed that this ancestral karyotype is largely conserved among 2n = 22 rock wallaby species, and confirmed the identity of ancestral chromosomes which fused to produce the bi-armed chromosomes of the 2n = 16 tammar wallaby. These results illustrate the fission-fusion process of karyotype evolution characteristic of the kangaroo group.     

Recruitment and survival of native annual Trifolium species in the highlands of Ethiopia

Germination and survival of indigenous annual Trifolium species were studied. Seedlings naturally emerging in the field and from sown seeds in pots were regularly counted and uprooted, and survival was studied by monitoring colour‐coded seedlings. Differences in recruitment of Trifolium species were strongly related to the rainfall pattern. In the fallow (crop) lands, no seedling survived the dry season between the short and main rainy periods during the year, while in the natural pasture, 8% of the seedlings survived into the main growing (rainy) season. Occasional rains occurring in the dry period (between the two rainy periods) also induced successions of germination and seedlings death, and therefore depleted the soft seed reserve in the soil by the beginning of the main growing season. As temperature fluctuations were minimal during the main rainy season, the rate of seed softening was low, affecting new germinations. This had a significant impact on the quality of the natural pastures on which livestock in the highlands are dependent.     

Induction of rehydration and bud break by irrigation or rain in decidous trees of a tropical dry forest in Costa Rica

Summary Clusters of 2–4 bare, deciduous hardwood trees and woody vines in a dry upland forest in Costa Rica were surrounded by scaffolding and rehydration was induced during the dry season by irrigation of 9–50 m² plots with 200 mm water. The resulting changes in water status preceding bud break were monitored. Following irrigation, stem water potentials increased from < –4 MPa to about –1.5 MPa within 24 h and to > –0.3 MPa within 48 h. Rehydration of stem tissues by lateral transport, measured as an increase in electric conductivity, continued for 4–8 days. Terminal flower buds in Tabebuia ochracea began to expand 48 h after irrigation and trees were in full bloom 4 days later. In all experimental species, lateral vegetative buds began to expand 5–7 days after irrigation and leaves were fully expanded 2 weeks later. After the first rains of the rainy season (100 mm in 48 hr) all trees in the dry forest rehydrated and leaves emerged in synchrony slightly faster than after irrigation. In response to rain or irrigation drought-stressed tropical hardwood trees thus rehydrated at rates similar to those of desert succulents and their development resumed much faster than that of deciduous cold-temperate trees in spring.     

Shared DNA sequences between the X and Y chromosomes in the tammar wallaby – evidence for independent additions to eutherian and marsupial sex chromosomes

Marsupial sex chromosomes are smaller than their eutherian counterparts and are thought to reflect an ancestral mammalian X and Y. The gene content of this original X is represented largely by the long arm of the human X chromosome. Genes on the short arm of the human X are autosomal in marsupials and monotremes, and represent a recent addition to the eutherian X and Y. The marsupial X and Y apparently lack a pseudoautosomal region and show only end-to-end pairing at meiosis. However, the sex chromosomes of macropodid marsupials (kangaroos and wallabies) are larger than the sex chromosomes of other groups, and a nucleolus organizer is present on the X and occasionally the Y. Chromosome painting using DNA from sorted and microdissected wallaby X and Y chromosomes reveals homologous sequences on the tammar X and Y chromosomes, concentrated on the long arm of the Y chromosome and short arm of the X. Ribosomal DNA sequences were detected by fluorescence in situ hybridization on the wallaby Xp but not the Y. Since no chiasmata have been observed in marsupial sex chromosomes, it is unlikely that these shared sequences act as a pseudoautosomal region within which crossing over may occur, but they may be required for end-to-end associations. The shared region of wallaby X and Y chromosomes bears no homology with the recently added region of the eutherian sex chromosomes, so we conclude that independent additions occurred to both sex chromosomes in a eutherian and macropodid ancestor, as predicted by the addition-attrition hypothesis of sex chromosome evolution. Received: 18 October 1996 / Accepted: 21 February 1997     

Distribution and abundance of large herbivores in a northern Australian tropical savanna: A multi‐scale approach

Australian mammals have exhibited exceptionally high rates of decline since European settlement 230 years ago with much focus on small mammals in northern tropical savannas. In these systems, little scientific attention has been given to the suite of grazing macropods, family Macropodidae, (common wallaroo (Osphranter robustus), antilopine wallaroo (O. antilopinus) and agile wallaby (Notamacropus agilis)). These species may be impacted by feral herbivores and contemporary fire regimes, two threats linked to small mammal declines. A multi‐scale approach using aerial surveys, road surveys and camera trapping was utilised to determine the effects of feral cattle and fire on the distribution and abundance of large macropods in the North Kimberley bioregion. Feral cattle density and biomass exceeded that of macropods regardless of survey technique. Density estimates for cattle were up to 125 times higher (0.3–10.0 km^?2) than estimates for macropods (0.08–0.49 km^?2). Cattle biomass, based on the aerial survey estimates (corrected for perception bias), were 15 and 95 times higher than macropods for infertile (279 vs. 19 kg km^?2) and fertile savannas (518 vs. 5 kg km^?2), respectively. Proximity to the nearest pastoral station was a significant predictor of the aerial sightings of feral cattle (P ≤ 0.05). Abundance and foraging activity of cattle were positively associated (P ≤ 0.05) with recently burnt areas. In contrast, camera trapping showed agile wallaby and wallaroo occurrence and foraging were associated with longer unburnt areas (P ≤ 0.05). Agile wallaby and wallaroo were negatively associated with cattle (P ≤ 0.05) and showed substantial diurnal and seasonal separation consistent with an antagonistic interspecific interaction. Results also suggest that the agile wallaby is the primary prey of the dingo, not wallaroo. Collectively, this study suggests that recent landscape changes such as altered fire regimes and introduced herbivores have negatively impacted large grazing macropod species.     

Highly mobile insectivorous swifts perform multiple intra‐tropical migrations to exploit an asynchronous African phenology

With timely allocated movement phases, mobile organisms can match their space‐use with the seasonality of the environment and thereby optimise their resource utilisation over time. Long‐distance avian migrants are known to move with the seasonal dynamics on an annual basis, but how individuals respond to seasonality within their tropical non‐breeding range has been less studied. Here we analyse the movement pattern of a highly mobile aerial insectivorous bird, the pallid swift Apus pallidus, and its association with the local habitat phenology during the non‐breeding period, using individual‐based light‐level geolocation. We extracted timing and location of 21 birds’ residence periods, as well as characteristics of the intervening movements, such as distance and speed. We used time series of precipitation and vegetation data for each residence area to extract the timing of the local end of the rainy season and the onset of the dry season. The pallid swifts repeatedly upgraded their habitat by undertaking 2–5 intra‐tropical migrations correlated with the withdrawal of the rains and the onset of the local dry season. The birds arrived to the sites on average 12 days after rains ended and departed about two weeks after the onset of dry season suggesting that the birds closely tracked a spatiotemporal window presumably timed with optimal foraging conditions. Our results provide insights in the ways Palaearctic–African migrants respond to the asynchronous phenology within their sub‐Saharan non‐breeding range. We confirmed that pallid swifts actively respond to deteriorating conditions by repeated upgrades in habitat quality, which likely have substantial consequences for an individual's access to an essential, spatiotemporally ephemeral food resource. However, the pallid swifts did not surf an apparent resource wave per se as would be expected in a highly mobile species, indicating that also other factors, such as spatial patchiness of resources, may influence the movement decision.     

Comparative red blood cell metabolism in three wallaby species, Macropus eugenii, Macropus parma and Thylogale thetis (Macropodidae: Marsupialia)

Aspects of red blood cell metabolism were compared among three species of small macropodid marsupials from different habitats. Packed cell volume (PCV), erythrocyte reduced glutathione (GSH) concentration and GSH regeneration rates were similar in all three species. The Parma wallaby had very low red cell potassium levels compared to the other species studied. The Tammar wallaby had higher rates of glucose consumption and lactate production in vitro at both pH 7.4 and 8.2 than did the Parma and significantly lower adenosine triphosphate (ATP) levels than the other species. These findings are consistent with preliminary reports published previously. The differences noted cannot be directly related to differences in the habitats of the species.     

THE ROLE OF MUCILAGE IN THE GERMINATION OF CUIPO,CAVANILLESIA PLATANIFOLIA (H. & B.) H. B. K. (BOMBACACEAE), A TROPICAL TREE

The mucilage in the fruits of cuipo, Cavanillesia platanifolia, is an adaptation to the unpredictable rainfall at the beginning of the rainy season in the tropical moist forests of central Panama. It allows cuipo to germinate rapidly following rains in the early rainy season, before other potential competitors. Mucilage comprises ~27% of the mass of the large (~3.5 g) wind-dispersed fruits of cuipo. Water uptake capacity of cuipo fruits (7 g water/g fruit in 10 min) was greater than that of the diaspores of five wind-dispersed species sympatric with cuipo. Diaspores of these five species lost all their absorbed water within 2 days but cuipo retained it for 2 wk. Experiments using two mucilage treatments (seeds within fruit and seeds alone) and three watering treatments (daily, weekly, and biweekly) indicated that 1) neither mucilage nor watering treatments altered percent germination; 2) the presence of mucilage-rich fruits lessened the effects of drought on seedling development and decreased the degree of wilting; and 3) both treatments interacted in their effects on percent and cause of mortality.     

Aspects of reproductive biology of Labeo horie Heckel (Pisces: Cyprinidae) in Lake Chamo, Ethiopia

Labeo horie Heckel is increasingly becoming commercially important in Lake Chamo but its reproductive biology in the lake is not well enough to guide its management. Sex ratio, breeding season, length at first maturity and fecundity of L. horie were studied from 1197 fish samples collected between August 1998 and October 1999 in Lake Chamo, Ethiopia. The sex ratio was significantly different (χ ² = 12.12, P < 0.001). The peak‐breeding period was during the rainy months of March to May, during which time more than 90% of both sexes had ripe gonads. The size at maturity ( L _m50 ) of males was 52 cm while the L _m50 of females was 62 cm. The smallest ripe male in the catch was 46.7 cm and weighed 890 g while the smallest ripe female caught was 49.5 cm and weighed 1145 g. The weight of ripe ovaries ranged from 54.3 g to 991.8 g and contained between 68,400 and 1,320,400 eggs. Relative fecundity ranged between 60 and 290 eggs per g of body weight. The relationships between fecundity and total length and between fecundity and total weight were curvilinear, while the relationship between fecundity and ovary weight was linear. L. horie conformed to the general pattern of reproduction in a tropical environment where peak‐breeding activity occurred during the rainy season. In order to protect the spawning population, fishing pressure should be minimized during breeding time at the shallower littoral regions.     

Relationships within theRugopharynx delta species complex (Nematoda: Strongyloidea) from Australian marsupials inferred from allozyme electrophoretic data

Relationships between the strongyloid nematodesRugopharynx delta, R. zeta, R. omega, R. longibursaris, R. mawsonae andR. sigma, all from macropodid marsupials, were investigated using allozyme data. The phylogenetic trees derived from the electrophoretic data set were congruent with those of the hosts and were consistent with the hypothesis that the species complex originated in pademelons of the genusThylogale and diversified in rock-wallabies (Petrogale spp.) and scrub wallabies of the subgenusNotamacropus. Host switching is evident only between closely related macropodid taxa.     

Population biology and breeding cycle of the burrowing shrimp Callichirus seilacheri (Decapoda,Callianassidae) from the eastern tropical Pacific

Year-round continuous reproduction in tropical regions is an established paradigm in marine ecology. In this study, we tested this paradigm using the ghost shrimp Callichirus seilacheri from the tropical eastern Pacific as a model species. We also examined size-frequency distribution, sex ratio, and recruitment cycle to contribute to the biological knowledge of this species. To this end, a total of 456 individuals of C. seilacheri were collected during 12 months of sampling. Population structure was symmetrical for both sexes, and the overall sex ratio did not differ from evenness. Males outnumbered females in smaller size classes, though, revealing a potential sex-dependent mortality in small individuals. The breeding pattern followed the well-marked seasonal regime of the region, with ovigerous females registered during the rainy season. While natural variation in the seawater temperature had no influence on reproduction of this species, changes in water salinity possibly triggered the appearance of egg-bearing females in the population. Recruitment occurred throughout the year but was more intense during the dry season, following the appearance of ovigerous females. The adaptability of the life cycle of C. seilacheri to the seasonal climate provides further evidence that reproduction in tropical species is not always continuous.