Evolutionary significance of foregut fermentation in the hoatzin (Opisthocomus hoazin; Aves: Opisthocomidae)

The hoatzin (Opisthocomus hoazin) is the only folivorous bird known to possess extensive fermentation in the crop by mixed bacterial populations. In this work, the digestive tract of the hoatzin was studied morphometrically and microbiologically, and its significance in the evolution of herbivory in vertebrates is discussed. The crop of the hoatzin is already formed in newly hatched chicks, and acquires microbial populations of bacteria and protozoa within the first 2 weeks of life, presumably by inoculation during feeding by adults. Numbers of bacteria and protozoa resemble numbers from the rumen of Ruminantia. The presence of foregut fermentation in this bird demonstrates that this strategy is not an exclusive feature of mammals. Herbivorous mammals developed foregut structures without homologues among other mammals, while the crop of the hoatzin, being homologous to that in other birds, is analogous to the mammalian foregut fermentation chambers. Thus, evolution of foregut fermentation in mammals and birds might be a case of evolutionary convergence.Abbreviations BM body mass - GC gas-liquid-chromatography - SCFA short-chain fatty acid - SE standard error of mean     

The social organization and behaviour of the Hoatzin Opisthocomus hoazin in central Venezuela

The social organization and behaviour of the Hoatzin Opisthocomus hoazin , a cooperatively-breeding folivorous bird, was studied in the central plains (llanos) of Venezuela. In this area Hoatzins nested in communal social units of two to eight individuals. Units were usually composed of a breeding pair and up to six helpers at the nest. Helpers, usually offspring retained from the previous years' nesting, aided in all breeding activities of their social unit except egg production. On the study site, Hoatzin units defended extremely small, all-purpose territories along watercourses during the rainy (breeding) season, but migrated up to 2 km to areas with permanent water during the dry season. Nesting extended from early May to October. Nest and egg measurements and growth rates of young are provided. Nesting success was low (27%), primarily due to predation by Cebus olivaceus and several other species. Annual survival of adults and young was high. Young did not breed during their first year; 90% of yearlings remained on their natal territories as helpers. Females appear to be the dispersing sex. The results are discussed in relation to previous work on the Hoatzin. The demography of the study population fits the criteria for several recent theories regarding the evolution of cooperative breeding in birds.     

Sound the stressor: how Hoatzins (Opisthocomus hoazin) react to ecotourist conversation

Exposure to ecotourists often disrupts animal behavior, which is known to contribute to heightened mortality rates. In the Amazon, the emblematic, communal nesting Hoatzin (Opisthocomus hoazin) is frequently pursued by tourists eager for close views. Such encounters may cause heightened stress levels, and egg or nestling predation due to decreased parental attendance to nests and nestlings. The effect of reducing conversational tourist noise near wildlife is poorly understood, but represents one potential mechanism of mitigating the impacts of ecotourists on wildlife. In this study, we approached Hoatzins by canoe, playing recorded tourist conversations at different volumes. Both the distances from which we observed Hoatzins becoming agitated (e.g., clucking, defecation, etc.) and flush (e.g., flight or climbing away) were positively correlated with volume. Within 10 weeks Hoatzins began to habituate to silent approaches. Tourist conversations, however, continued to elicit the same heightened disturbance responses throughout data collection. Therefore, to have the best chance of seeing Hoatzins at a short distance and minimizing potentially negative disturbances, ecotourists should cease all conversation. Although not tested, silence is probably the best strategy when looking for many wildlife species.     

Bacterial community in the crop of the hoatzin, a neotropical folivorous flying bird

The hoatzin is unique among known avian species because of the fermentative function of its enlarged crop. A small-bodied flying foregut fermenter is a paradox, and this bird provides an interesting model to examine how diet selection and the gut microbiota contribute to maximizing digestive efficiency. Therefore, we characterized the bacterial population in the crop of six adult hoatzins captured from the wild. A total of 1,235 16S rRNA gene sequences were grouped into 580 phylotypes (67% of the pooled species richness sampled, based on Good's coverage estimator, with C(ACE) and Chao1 estimates of 1,709 and 1,795 species-level [99% identity] operational taxonomic units, respectively). Members of 9 of the approximately 75 known phyla in Bacteria were identified in this gut habitat; the Firmicutes were dominant (67% of sequences, belonging to the classes Clostridia, Mollicutes, and Bacilli), followed by the Bacteroidetes (30%, mostly in the order Bacteroidales), Proteobacteria (1.8%), and Lentisphaerae, Verrucomicrobia, TM7, Spirochaetes, Actinobacteria, and Aminanaerobia (all <0.1%). The novelty in this ecosystem is great; 94% of the phylotypes were unclassified at the "species" level and thus likely include novel cellulolytic lineages.     

Adaptations of the hoatzin (Opisthocomus hoazin) to leaf-eating. Morphological characteristics and functional features of its bill and hyoid apparatus

The hoatzin remains one of the most enigmatic birds. A morphofunctional analysis of its bill and hyoid apparatus throws new light on its feeding adaptation as well as on its systematic relationships. Bony and muscular skull, rhamphotheca, palate, and hyoid apparatus were described in details. Though keeping into the general organisation pattern found among Neognathae (except Galliformes), bill and hyoid apparatus of the hoatzin displays a series of species-specific features, some unique among birds. This species appears particularly well adapted to tear of leaves and process them inside the bill before ingestion. Because of very important anatomical and thence functional differences in bill and hyoid structure, any close relationship between the hoatzin and Galliformes cannot be envisioned. Such a hypothesis would implicate a counter-selective evolutionary reversion.     

Digestive efficiency of a generalist avian feeder,the Cape White-eye (Zosterops pallidus)

Digestive processes determine whether the particular diet of a bird is utilized efficiently and whether energetic demands are met. Assimilation efficiency is often used as an index of whether a diet is digested optimally. Studies on the digestive processing of generalist feeders are scarce. Cape White-eyes (Zosterops pallidus) have a diverse diet of fruit, nectar and insects. The nutrient contents of these three diets vary considerably and require quite different digestive processing. This study compared the digestive efficiencies of Cape White-eyes on these three diets by measuring transit times and assimilation efficiency. Cape White-eyes lost body mass significantly when fed fruit, while they maintained and gained body mass on nectar and mealworm diets, respectively. Assimilation efficiency varied significantly between the three diet types (nectar>mealworms>apples). When given a choice of diets, Cape White-eyes selected the diet, which was most efficiently digested and yielded the greatest energetic reward. Diet preference trials further showed that Cape White-eyes regulated daily energy intake. Assimilation efficiency depends on the accessibility of nutritional contents of a diet. Cape White-eyes did not maximize assimilation efficiency. Instead, they adjusted transit time to maximize the rate of energy gain per gram of food in order to maintain energy balance.     

Digestive efficiency in two small, wild ruminants: the dik-dik and suni antelopes

A comparative study, using six dik-dik and eight suni antelope, was undertaken to identify similarities and differences that may exist in the digestive process of these two small, East African ruminant browsers. The suni antelope was the more select feeder, preferring the native, Grewia sinilis leaves over that of lucerne hay. Daily forage consumption rate, per unity body weight, was greater in the dik-dik (40.4 g/kg) than for the suni (30.6 g/kg), while daily fluid intake was considerably less (i.e. dik-dik, 68 ml/kg versus suni, 106 ml/kg body weight). Rumen fermentation studies suggested that the suni antelope attained the more rapid rumen and caecal fermentation activities, when compared to the dik-dik antelope. The difference in ruminal and caecal digestive process of the two antelope is suggested to be partly the result of the dik-dik's arid-adaptation strategies of less fluid intake and a more diverse (less selective) browse consumption, relative to the suni antelope.     

Predicting folivorous primate abundance: validation of a nutritional model

Understanding the determinants of animal abundance has become more vital as ecologists are increasingly asked to apply their knowledge to the construction of informed management plans. However, there are few general models are available to explain variation in abundance. Some notable exceptions are studies of folivorous primates, in which the protein-to-fiber ratio of foods has been shown to predict biomass. Here we examine the generality of Milton's [American Naturalist 114:363-378, 1979] protein/fiber model by providing a detailed analysis of diet selection in black-and-white colobus monkeys (Colobus guereza), and applying the model to populations shown to be stable; an assumption not previously examined. Based on observations of two groups of black-and-white colobus in Kibale National Park, Uganda, and one group in a forest fragment, we documented that the animals selected young leaves that had more protein, were more digestible, and had a higher protein-to-fiber ratio than mature leaves. The mature leaves did not differ from young leaves with respect to secondary compounds or mineral content (with the exceptions of copper and zinc). All of the colobus groups selected foods with a high protein-to-fiber ratios. However, one group also selected more digestible foods, and in another group, foraging efforts were positively related to zinc and negatively related to potassium. Previous studies that examined Milton's protein/fiber model did not demonstrate that the study populations were stable. If some populations were not at carrying capacity, then the correlations drawn between food availability and/or quality and folivore biomass may have been spurious. To address this issue, we censused a series of forest fragments in 1995 and again in 2000. We found that the populations in these fragments had declined from 165 in 1995 to 119 animals in 2000. However, based on evidence of population stability and lack of forest disturbance, we concluded that five of the original populations were stable. The biomass of these populations was related to the protein-to-fiber ratio of the fragment's trees. Combining our data with published data, we demonstrate that the protein-to-fiber ratios of mature leaves available to these folivorous primates accounted for 87% of the variance in their biomass.     

Habitat alteration,hunting and the conservation of folivorous primates in African forests

Abstract The colobus monkeys and gorillas of African forests share a strong tendency to depend on foliage during lean seasons. In many areas, both kinds of primate are threatened by habitat destruction. But while the total removal of natural habitat is clearly a major threat to the survival of many African forest primates, an analysis of survey data suggests that human predation tends to have a greater negative impact on primate populations than does selective logging or low-intensity bush-fallow agriculture. In the absence of hunting, the population density of colobus monkeys correlates with the protein: fibre ratio of mature tree foliage in their habitat, and the density of gorillas appears to be correlated with the abundance of terrestrial herbaceous vegetation. Because moderately disturbed forest can be relatively rich in high-quality lean-season folivore foods, such forest sometimes supports a higher density of folivorous primates than forest that has not been recently disturbed but that has been subject to hunting. Conservation plans for African forests should place more emphasis on the control of hunting and less on rural development, and long-range plans should also allow for the strong possibility of political instability.     

高效降解纤维素低温真菌的筛选、鉴定及发酵优化

【背景】纤维素的生物转化已经成为能源、环境和化工领域的研究热点,但可降解纤维素的低温真菌鲜有报道。【目的】从西藏高海拔的植物根际土壤中筛选具有高效降解纤维素能力的低温真菌,优化其产酶条件,为其工业化应用奠定基础。【方法】利用稀释平板涂布法、刚果红定性及酶活定量分析进行低温降解菌的筛选;根据菌株形态学特征及ITSrDNA序列分析对其进行鉴定;利用单因素实验和响应面优化法优化其产酶条件。【结果】分离筛选到一株高效产纤维素酶的低温真菌NLS-2;鉴定菌株NLS-2为青霉菌属;在低温15°C下,其产纤维素酶的最佳培养条件为稻草粉2.5%,酵母粉0.5%,KH2PO40.5%,发酵时间7d,pH6.5,摇床转速170r/min。【结论】青霉菌NLS-2可在低温条件下生长并具有较强的纤维素酶生产能力,具有良好的应用前景。     

Effects of clonal variation of the host plant,interspecific competition,and climate on the population size of a folivorous thrips

Summary The effects of clonal variation, interspecific competition, and climate upon the population size of Apterothrips secticornis was assessed by a series of observations and experimental manipulations. Three clones of the host plant, Erigeron glaucus, consistently supported different numbers of thrips during monthly censuses. When rosettes of the three clones were transplanted to a common garden, relative numbers of thrips on the clones remained the same as those observed where the clones grew in situ. The presence or absence of other hervivores had no effect on thrips numbers in the common garden. Plume moth caterpillars and thrips were observed to co-occur less often than expected in the field but this was caused by differences in habitat selection by these two species rather than being the result of interspecific competition. Populations of thrips were affected by climate, but analyses suggest that the host clone was a more important factor.     

Schultz's unruly rule: dental developmental sequences and schedules in small-bodied, folivorous lemurs

Schultz's rule (as reconstructed by Smith) states that there is a relationship between the pattern (or relative order) of eruption of molar versus secondary (replacement) teeth and the overall pace (or absolute timing) of growth and maturation. Species with 'fast' life histories (rapid dental development, rapid growth, early sexual maturation, short life spans) are said to exhibit relatively early eruption of the molars and late eruption of the secondary replacement teeth (premolars, canines, incisors), whereas species with 'slow' life histories are said to exhibit relatively late eruption of the molars and early eruption of the secondary dentition. In a recent review, B.H. Smith noted that primates with tooth combs might violate this rule because tooth combs tend to erupt early, regardless of the pace of life history. We show that exceptions to Schultz's rule among lemurs are not limited to the relative timing of eruption of the tooth comb. Rather, among lemurs, some species with extremely accelerated dental development exhibit a pattern of eruption of molars and of secondary teeth in direct opposition to the expectations of Schultz's rule. We focus particularly on the pattern (order) and pace (absolute timing) of dental development and eruption in Avahi and Lepilemur - two relatively small, nocturnal folivores with rapid dental development. These taxa differ markedly in their eruption sequences (the premolars erupt after M2 and M3 in Lepilemur but not Avahi ). We offer an explanation for the failure of Schultz's rule to predict these differences. Schultz's rule presumes that eruption timing is dependent on the size of the jaw and that, therefore, molar crown formation and eruption will be delayed in species with slow-growing jaws. We show that a variety of processes (including developmental imbrication) allows the crowns of permanent teeth to form and to erupt into jaws that might appear to be too small to accommodate them.     

Unexpectedly low UV-sensitivity in a bird,the budgerigar

Photoreceptor adaptation ensures appropriate visual responses during changing light conditions and contributes to colour constancy. We used behavioural tests to compare UV-sensitivity of budgerigars after adaptation to UV-rich and UV-poor backgrounds. In the latter case, we found lower UV-sensitivity than expected, which could be the result of photon-shot noise corrupting cone signal robustness or nonlinear background adaptation. We suggest that nonlinear adaptation may be necessary for allowing cones to discriminate UV-rich signals, such as bird plumage colours, against UV-poor natural backgrounds.     

Hybridization between two insectivorous bird species and the effect on prey-handling efficiency

Gene flow between closely related species is not always impeded by hybrid inviability or sterility but may be limited by behavioural or ecological factors. European common redstarts, Phoenicurus phoenicurus, and black redstarts, P. ochruros, are insectivorous passerine bird species which regularly interbreed in the wild and produce viable and fertile progeny. Yet, the isolation barriers, which prevent extensive gene flow between these distinct species, are unknown. I studied prey-handling time and efficiency in both species and the F₁-hybrids in captivity. All birds changed prey-handling mode from a single pick to more complex behaviour with increasing prey length and their handling time was a positive function of prey length. Common redstarts tended to handle their prey quicker than black redstarts. Hybrids appeared to be intermediate. However, individual differences were significant, but group membership was not. Handling efficiency decreased with increasing prey length and was determined by individual and family effects. Hybrid females handled their prey as efficient as hybrid males. Small differences in beak morphology could not explain individual differences in prey-handling behaviour. The results of this study suggest that prey-handling in F₁-hybrids is not a postzygotic barrier which prevent gene flow between common and black redstarts in the wild.     

Digestive amylase of a primitive animal,the scorpion: Purification and biochemical characterization

Scorpion, one of the most ancient invertebrates was chosen, as a model of a primitive animal, to purify and characterize an amylase located in the hepatopancreas. The scorpion digestive amylase (SDA) was purified. Pure SDA was obtained after heat treatment followed by ammonium sulfate fractionation and three steps of chromatography. The pure amylase is not glycosylated and has a molecular mass of 59,101 Da determined by MALDI-TOF MS analysis. The maximal amylase activity was measured at pH 7.0 and 50 °C, in the presence of Ca²⁺ and using potato starch as substrate. The enzyme was able to hydrolyze also, glycogen and amylose. The 23 NH₂-terminal amino acid SDA residues were sequenced. The sequence obtained is similar to those of mammalian and avian pancreatic amylases. Nevertheless, polyclonal antibodies directed against SDA failed to recognize classical digestive amylases like the porcine pancreatic one.     

Paternity in the Australian brush-turkey, Alectura lathami, a megapode bird with uniparental male care

Male Australian brush-turkeys, Alectura lathami, provide allparental care by building and tending large incubation mounds.Females visit and lay eggs in the mounds of several males sequentially,but they provide no parental care after laying. Because malesand females meet only briefly at mounds to copulate and lay,males have no obvious means of ensuring paternity. I used DNAfingerprinting techniques to determine paternity for 65 brush-turkeychicks. Eighteen chicks (27.7%) did not match the mound-tendingmale. Some of these paternity exclusions were evidently causedby females switching rapidly from one mound to another, butthe majority (23.1% of eggs) appeared to result from femalescopulating with males other than the one in whose mound theywere currently laying. However, the frequency of these copulations(43%) was much lower than the estimated frequency with whichthey fertilized eggs, perhaps because their timing during theovulatory cycle differed relative to most other copulations.The percentage of eggs excluded in paternity analyses rangedfrom 20.0% to 43.8% for individual males but did not appearto affect male parental care. Several factors favor male parentalcare regardless of paternity. Males can accommodate eggs fromseveral females in one mound, which increases the opportunitiesfor additional matings without increasing the cost of parentalcare. In addition, paternity appears to be unpredictable andhard to assess, and a facultative reduction in care would bedifficult without abandoning a mound entirely.