The functional significance of skeletal allometry in Megaladapis in comparison to living prosimians

Slow vertical climbing and clinging are the dominant positional behaviors of the most convincing reconstruction of the primary spatial niche of Megaladapis, a giant extinct prosimian from Madagascar. The vertical support model of Cartmill ('74) predicts that clawless mammals should exhibit relatively elongated forelimbs in expanded size ranges. The allometric corollaries of this model are tested on closely related interspecific samples of Megaladapis and selected extant prosimians. Megaladapis and indriids (vertical leapers and clingers) conform to the structural predictions of the model, and are clearly distinguished from the more pronograde lemurids and cheirogaleids. Extreme hindlimb reduction (negative allometry) is coupled with moderate forelimb elongation (positive allometry) in Megaladapis. These body proportions effectively optimize pedal friction during vertical climbing and minimize the moment of body weight pulling the animal away from the trunk. Positive forelimb allometry occurs in the indriids, while isometry obtains for the hindlimb. The adaptive significance of these morphological strategies are discussed, as are possible selective mechanisms which effect the extreme hindlimb reduction in Megaladapis. Body weight estimates are also presented for Megaladapis edwardsi and Megaladapis grandidieri (50–100 kg and 40–75 kg, respectively).     

Nutritional ecology of dimorphic herbivores: digestion and passage rates in Nubian ibex

We compared forage digestion and passage rates among three groups of Nubian ibex (Capra ibex nubiana) — mature males, non-lactating females, and lactating females — to test hypotheses relating intraspecific digestive ability to body mass and reproduction costs. We hypothesized that large males (60 kg) would exhibit longer forage retention times and more complete digestion of fermentable cell walls than adult females (23 kg). We tested these predictions by measuring digestion and retention of a grass hay and an alfalfa hay, forages that exhibited contrasting rates and extents of cell wall digestion. Consistent with predictions, males retained both forages longer than non-lactating females. However, by substantially increasing gut fill, lactating females increased both intake and retention time with respect to non-lactating females. Contrary to predictions, all three groups digested the grass (66% digestible) and alfalfa hay (63%) equally well. Alfalfa cell wall was less digestible than that of grass hay (60% vs 69% digestible), and retention time of alfalfa was consistently, but not statistically significantly, shorter. Fiber digestion was not correlated with retention time, emphasizing the ability of behavioral processes to modify digestion rate. We postulate that females achieved their greater digestion rate by masticating forages much more thoroughly than males.     

The ontogeny of sexual dimorphism in the facial skeleton of the African apes

This paper aims to test the contribution of ontogenetic scaling to sexual dimorphism of the facial skeleton in the African apes. Specifically, it addresses whether males and females of each species share a common postnatal ontogenetic shape trajectory for the facial skeleton. Where trajectories are found to differ, it is tested whether male and female trajectories: 1) diverge early, or 2) diverge later after sharing a common trajectory earlier in the postnatal period. Where ontogenetic shape trajectories are found to be shared, it is also tested whether males and females are ontogenetically scaled. This study uses geometric morphometric analyses of 28 landmarks from the facial skeletons of 137 G. g. gorilla (62 adults; 75 juveniles), 95 P. paniscus (34 adults; 61 juveniles), and 115 P. t. troglodytes (58 adults; 57 juveniles). On average, males and females share a common ontogenetic shape trajectory until around the eruption of the second permanent molars. In addition, for the same period, males and females in each species share a common ontogenetic scaling trajectory. After this period, males and females diverge both from each other and from the common juvenile ontogenetic shape and scaling trajectories within each species. Thus, the male and female facial skeleton shows ontogenetic scaling until around the point of the eruption of the second molar (i.e., around puberty and the development of secondary sexual characteristics), but subsequent sexual dimorphism occurs via divergent trajectories and not via ontogenetic scaling.     

昆明滇蛙的取食策略

目前国内研究两栖类食性选择或偏好多未考虑蛙胃内不同食物的丰盈程度与栖境不同食物资源是否存在相关性.在分析了采自昆明白龙寺和昆明石林西街口的494只滇蛙(Rana pleuraden)的食性的同时,分析了采自对应栖境中的食物资源组成.结果表明,滇蛙的食物成份与食物资源相具有稳定性,主要类群均为直翅目、同翅目、半翅目、鞘翅目、双翅目、鳞翅目、膜翅目和蛛形纲等8类.但又存在变异性,不同产地、不同年份和不同月份之间的蛙标本胃内的食物成分各类群的比例均不相同.主要食物成份与食物资源相的差异显著性分析、相关性分析和选择性分析等方面的结果均支持或证明:滇蛙对食物具有选择性或取食偏好.栖境的食物资源相与蛙胃内的食物成分不存在相关性(白龙寺:r=0.077,P=0.575;西街口:r=-0.086,P=0.500).直翅目(Ei＜-0.35)和同翅目(Ei＜-0.37)昆虫是滇蛙取食时回避的食物,而对鞘翅目、鳞翅目、膜翅目和蛛形纲等4个类群(Ei＞0.45)具有明显偏好.     

The dissociation of the fluid and particle phase in the forestomach as a physiological characteristic of large grazing ruminants: an evaluation of available, comparable ruminant passage data

Whether differences in digestive physiology exist between different ruminant feeding types has been an ongoing debate. In this regard, potential differences in ingesta retention have been understood to be of particular importance. We analyzed a data pool in which only mean retention time (MRT) data for the ruminoreticulum (RR) were collated that were obtained using comparable techniques with either chromium or cobalt EDTA as a fluid marker and/or with chromium-mordanted fiber of less than 2 mm in size as a particle marker. Data were compared using one averaged value per species. In general, the paucity of species in such a collection is striking and does not allow—in contrast to earlier statements—any final conclusions regarding the influence of body weight (BW) or feeding type on ruminant MRTs. In particular, there was no significant correlation between MRT_particlesRR or MRT_fluidRR and BW, neither in the interspecific nor in the intraspecific comparisons, and no difference between the feeding types. The trend that indicates longer MRT_particlesRR in grazers is based on too few species to be conclusive. Small browsers seemed to have shorter MRT_fluidRR than similar-sized grazers. In contrast, there was a trend for large grazers to have shorter MRT_fluidRR than large browsers. In direct pair-wise comparisons between cattle and the browsers giraffe, moose, and okapi, the latter difference was significant. Cattle also had the highest relative RR fluid outflow rates among the species investigated. This is in accord with the observation that grazers have larger omasa, a major function of which is water-reabsorption distal to the RR. Grazers seem to have longer MRT_particlesRR per unit MRT_fluidRR, and cattle are particular outliers in this respect. It is hypothesized that potentially shorter MRT_fluidRR in large grazers and higher relative outflow rates are linked to a higher saliva production and a lesser viscosity of both saliva and RR fluids. A constant supply of a fluid phase of low viscosity is proposed to be the prerogative for the physical mechanisms of flotation and sedimentation that result in the stratification of RR contents and its selective particle retention typical for large grazing species.     

刀鲚幼鱼消化系统的组织形态学结构

采用光镜和扫描电镜观察长江刀鲚(Coilia nasus)幼鱼消化系统组织形态学结构。结果显示,刀鲚体长,口裂大,含有犬齿状的颌齿和尖锥状的腭齿,具有5对鳃弓,鳃耙长度明显大于鳃丝且表面附着不规则绒毛状细齿;胃呈"Y"型,胃与肠连接处具有16～21个指状环形幽门盲囊;肠为直肠,较短,比肠长为0.241±0.080;肝分为两叶,胰为独立的器官。刀鲚口咽腔为复层鳞状上皮,含有腺体、大量椭圆形黏液细胞、少量杯状细胞及味蕾;胃黏膜都为典型的单层柱状上皮,含有较多由上皮凹陷形成的胃小凹和胃腺;幽门盲囊具有20～25个丰富的褶皱,占满大部分幽门盲囊腔,黏膜层具有微绒毛;中肠黏膜上皮最发达,形成的褶皱细长且连接成网状,单层柱状上皮与复层扁平上皮交替分布。观察结果表明,刀鲚消化系统具有典型肉食性鱼类特征。     

The molecular mechanisms and factors affecting the feeding habits of silkworm (Lepidoptera: Bombyxidae)

Food is critical to the survival and development of insects. Bombyx mori (Lepidoptera: Bombycidae), a Lepidoptera model insect with economic significance, is a well-known oligophagous insect that mainly feeds on mulberry leaves. The feeding characteristics of this particular species provide an excellent model for studying the food selection of insect host plants. In recent years, there has been an increasing number of studies on the factors affecting the feeding of silkworms, especially with the development of molecular technology. Many mysteries have been gradually solved. This paper summarizes and discusses the factors that affect the feeding of silkworms, with a focus on the molecular mechanisms of silkworm feeding. It is hoped that this work will be helpful for further research on artificial diets for silkworms and disease control in lepidopteran insects.     

Allometry and heterochrony in the African apes

In this work allometry and heterochrony are integrated in an analysis of ontogenic and interspecific morphological patterns in the African apes. The relationship between the interspecific differences in adult morphology and the differences in underlying patterns of growth allometries, body weight growth rates, and developmental chronologies is investigated. Results indicate that rate hypermorphosis, or the extension of ancestral allometries into new size/shape ranges with no increase in the duration of ontogeny, underlies many of the interspecific differences in form among the African apes. In addition, the need for further clarification of the processes of heterochrony is stressed by distinguishing between rate and timing differences. These distinctions and processes are illustrated and discussed using the morphological data on the African apes.     

The influence of sex and body size on food habits of a giant tropical snake, Python reticulatus

1. In many animal species, dietary habits shift with body size, and differ between the sexes. However, the intraspecific range of body sizes is usually low, making it difficult to quantify size-associated trophic shifts, or to determine the degree to which sex differences in diet are due to body-size differences. Large snakes are ideal for such a study, because they provide a vast range of body sizes within a single population.
2. More than 1000 Reticulated Pythons ( Python reticulatus ) from southern Sumatra were examined, with specimens from 1·5 to > 6 m in snout–vent length, and from 1 to 75 kg in mass. Females attained much larger body sizes than did conspecific males (maxima of 20 vs 75 kg, 5 vs 7 m), but had similar head lengths at the same body lengths.
3. Prey sizes, feeding frequencies and numbers of stomach parasites (ascarid nematodes) increased with body size in both sexes, and dietary composition changed ontogenetically. Small snakes fed mostly on rats, but shifted to larger mammalian taxa (e.g. pangolins, porcupines, monkeys, wild pigs, mouse deer) at 3–4-m body length.
4. Adult males and females showed strong ecological divergence. For some traits, this divergence was entirely caused by the strong allometry (combined with sexual size dimorphism), but in other cases (e.g. feeding frequency, dietary composition), the sexes followed different allometric trajectories. For example, females shifted from rats to larger mammals at a smaller body size than did conspecific males, and feeding frequencies increased more rapidly with body size in females than in males. These allometric divergences enhanced the degree of sex difference in trophic ecology induced by sexual size dimorphism.     

Distribution of enamel on the incisors of Old World monkeys

Longitudinal ground sections of 29 Old World monkey central lower incisors were studied histologically and metrically. Labiolingual incisor width tended to scale isometrically with body weight but with important deviations in relative incisor size, which appeared to be correlated with diet in accord with work by Hylander. Lower incisors of the predominantly folivorous colobine monkeys had a substantial layer of enamel on both lingual and labial aspects and consequently had blunt incisal edges. These teeth in both cercopithecins and papionins, which are omnivorous or frugivorous, had little or no enamel on the lingual aspect, resulting in sharp incisal edges. It is suggested that colobine incisors are used mainly in gripping and tearing leaves, whereas cercopithecine incisors are better adapted to cutting and scraping. Crown height showed a positive allometric relationship with overall incisor height, so that the tall incisors of papionins, especially Papio and Mandrillus, were more hypsodont than the shorter incisors of colobines and cercopithecins. This appears to be related to differences in the rates of incisor wear between the groups.     

The relative roles of phylogeny, body size and feeding style on the activity time of temperate ruminants: a reanalysis

In 1998, A. Mysterud analysed the relationships between a behavioural parameter (activity time, AT) and body mass and feeding style for 18 temperate ruminants. He found a negative allometric relationship between body mass and AT, and also found a significant effect of feeding style on AT after controlling for body mass. We reanalysed this data set taking into account the effect of phylogeny, and found that while body mass and AT were negatively related, feeding style did not have any effect on AT. We discuss the strong effect that phylogeny has on morphophysiological and behavioural features of ruminants that differ in feeding style, and the lack of evidence to support a feeding style effect. Received: 16 November 1998 / Accepted: 20 April 1999     

Digestive constraints on an aquatic carnivore: effects of feeding frequency and prey composition on harbor seals

We hypothesized that increased feeding frequency in captive harbor seals would increase nutrient loads and thus reduce retention time and the digestive efficiency of natural prey. We measured daily feed intake and excretion during 6 feeding trials and fed herring (49% lipid), pollock (22% lipid) or an equal mix of each diet over 24 months. Animals were accustomed to feeding at either high or low frequency. Body mass and intake did not vary with season. Although mean retention times were similar between diets and feeding frequencies, solute and particulate digesta markers separated at high feeding frequency. Consistent dry matter digestibility resulted in greater gut fill from pollock than from herring. Digestible energy intakes from pollock were approximately 25% greater than from either herring or the mixed diet. Lipid digestibility of herring declined from 90% to 50% when lipid intake exceeded 60 g kg^–0.75 day^–1. Our hypothesis of a trade-off between intake and digestion was not supported for protein but was supported for lipid. Results of this study imply that a flexible digestive system for harbor seals can compensate for ingesting prey of lower energy density by increasing gut fill and enhancing protein and lipid assimilation, to sustain digestible energy intake.Abbreviations DM dry matter - DEI digestible energy intake - DIT diet-induced thermogenesis - FF feeding frequency - MRT mean retention time Communicated by: G. Heldmaier     

Food habits of the Arabian skink,Scincus hemprichii Wiegmann, 1837, (Sauria: Scincidae), in the Southwest Saudi Arabia

Food and feeding habits of the Arabian skink, Scincus hemprichii were investigated in Jazan province, southwest of Saudi Arabia. S. hemprichii individuals fed during eleven months of the year. The mass of food in the stomachs indicated that a high degree of foraging success occurred during the warm spring while the lowest was during winter with January as an exception to feeding by the lizard. Analysis of the contents of 60 stomachs revealed that the diet of S. hemprichii in the study area consisted of arthropods, with two species of beetles of the family Dermestidae (Dermestis vulpinus and Dermestis maculates) and three type of dipteran larvae, accounting for 76% of the total volume of the food items. Specimens collected during January had empty stomachs.     

Investigations on the stratification of forestomach contents in ruminants: an ultrasonographic approach

The degree of stratification in the reticulorumen contents is considered a major explanatory factor for other morphological and physiological differences between ruminant feeding types. However, information on reticulorumen (RR) contents is usually gathered from dead animals or indirect such as passage kinetics. We hypothesized that, although the contents of the gastrointestinal tract can usually not be evaluated by ultrasonography, the three typical layers of stratified RR contents (gas dome, fibre mat, fluid) can be demonstrated by this technique. In three domestic cows, the gas dome in the cows’ rumens could be demonstrated sonographically by reverberation lines running in parallel to the line demarcating the rumen mucosa, as is typical for the sonographic image of large, gas-filled spaces. More ventrally, the area behind the rumen mucosa showed typical pattern indicating gaseous inclusions, corresponding to the fibre mat inside the rumen. Further ventrally, in two of the animals, the area behind the demarcation line appeared dark without reverberation lines, as is typical for large fluid-filled spaces. When the technique was applied to a captive, habituated, browse-fed moose, no gas dome could be demonstrated, supporting the hypothesis that the reticulorumen contents of browsers are less stratified. The results of this study indicate that sonography represents a useful tool for the demonstration of RR contents stratification in live animals.     

Changes in the digestive gland of the loliginid squid Sepioteuthis lessoniana (Lesson 1830) associated with feeding

Changes associated with feeding in the histological and cytological structure of the digestive gland of the loliginid squid Sepioteuthis lessoniana were examined, along with the nature of both the intracellular and extracellular enzymes produced by the gland. The timing of the release of the extracellular enzymes during the digestive cycle was also determined using a quantitative experimental program. Like that of all coleoid cephalopods, the digestive gland was characterised by one type of cell with several functional stages. As is the case for other loliginid squids, however, the digestive cells did not contain the large enzyme-carrying boules that characterise the digestive glands of most cephalopods. Instead, smaller secretory granules were found in the digestive cells and these may be the enzyme carriers. The prominent rough endoplasmic reticulum, large mitochondria and active Golgi complexes present in the digestive cells are characteristic of cephalopods and indicate a high metabolic activity. Like that of other cephalopods, endocytotic absorption of nutrients and intracellular digestion occurs in the digestive gland of this squid. From quantitative and qualitative examinations of structural changes in the digestive gland of S. lessoniana after feeding, a schedule of its function during the course of digestion was proposed. This indicated that digestion was very rapid, being completed in as little as 4 h in S. lessoniana. Extracellular digestive enzymes were only released after the first hour following feeding, which implies that they are stored in the stomach between meals to increase digestive efficiency.     

非洲雏鸵鸟消化管的组织学观察

为了给非洲鸵鸟(Struthio camelus)雏鸟的饲养管理、生理机能研究和疾病防治提供可靠的形态学依据,采用石蜡切片技术,对6羽50日龄非洲鸵鸟雏鸟消化管的组织学结构进行了观察。结果显示,其消化管具有一般的4层结构。食管有粗大的皱襞,肌层发达,有发达的食管腺;无嗉囊;腺胃的腺体由位于固有膜的单管状腺和位于黏膜下层发达的复管状腺组成;肌胃的黏膜肌层较明显,由内纵肌和外环肌组成;小肠绒毛较长,有分支现象,未见中央乳糜管结构;十二指肠的固有膜中有发达的腺体和集合淋巴小结,黏膜下层内无十二指肠腺;从十二指肠到回肠,肠绒毛的汇合及分支现象更加明显,固有膜内集合淋巴小结的数量逐渐减少,并且空肠的绒毛弯曲呈“S”型;具有一对发达的盲肠;结肠异常发达,黏膜上皮为复层柱状上皮,其间夹有杯状细胞,有黏膜皱襞,绒毛短且发达。非洲鸵鸟雏鸟消化管的特点可能与其食性有关,这决定了非洲鸵鸟具有较强的消化吸收能力。     

Ontogenetic changes in the diet of the sandbar shark, <Emphasis Type="Italic">Carcharhinus plumbeus</Emphasis>, in lower Chesapeake Bay and Virginia (USA) coastal waters

This study describes the diet of the sandbar shark, Carcharhinus plumbeus, highlighting differences in diet within various regions of the Virginia (USA) nursery area, as well as ontogenetic changes in diet. Stomach samples were obtained in 2001 and 2002 from 232 sharks caught by gillnets or longlines. Historical data from the Virginia Institute of Marine Science (VIMS) Shark Ecology Program were also analyzed. Ontogenetic changes in diet were evident, with crustacean prey decreasing in frequency with increasing shark size, and elasmobranch prey importance increasing with increasing shark size. Whereas previous research in Chincoteague Bay, VA showed the blue crab, Callinectes sapidus, was the dominant crustacean in sandbar shark diet, the mantis shrimp, Squilla empusa, dominated the crustacean portion of the diet in this study. Differences in diet of sharks were observed among locations within the study area. Small juveniles (≤80 cm precaudal length) in the lower Chesapeake Bay ate more fishes, whereas Eastern Shore juveniles ate more crustaceans. Crustacean prey items varied among locations along the Eastern Shore, with more portunid crabs consumed in waters near Wachapreague and more mantis shrimp consumed near Sand Shoal Inlet. Our study showed that Carcharhinus plumbeus is a generalist predator and is thus unlikely to strongly impact the population of any particular prey species, and in turn is not likely to be strongly affected by fluctuations in abundance of a single prey species.     

Influence of drying on the survival of anaerobic fungi in rumen digesta and faeces of cattle

Abstract Tolerance of anaerobic fungi in the faeces and rumen digesta of cattle to drying in air at approx. 20°C or 39°C was investigated. Anaerobic fungi were able to survive in dried faeces, but no significant survival was observed in digesta collected from five different regions of the rumen. Anaerobic fungi in faeces also survived when samples were dried in the presence of rumen digesta. When dried in the presence of sterile faeces, however, anaerobic fungi in rumen digesta failed to survive the drying process. The most plausible explanation for these results is that, during passage from the rumen to the rectum, anaerobic fungi undergo a transition to a dormant form resistant to air-drying.     

The potential of Commelina benghalensis as a forage for ruminants

To evaluate the potential of Commelina benghalensis as a forage for ruminants, effects of plant maturity on chemical composition, rumen degradability as well as its increased dietary inclusion level on intake, digestibility and N balance in sheep fed Sorghum almum were investigated with forage obtained from the wild, re-established and harvested at 6, 10 and 14 weeks of growth. Composite herbage samples were analyzed for dry matter (DM), chemical components, total extractable phenolics (TEP) and amino acid content. In sacco rumen degradability measurements used six individually confined wethers (8 ± 0.5 months of age; 21 ± 2.6 kg live-weight (LW)) fitted with rumen cannulae and fed a ration of 3:1 fresh S. almum and Medicago sativa hay (about 1:2 on a DM basis). In sacco bags containing 5 g each of dry herbage were inserted into the rumen and withdrawn sequentially after 0, 12, 24, 36 and 48 h. Metabolizable energy (ME) was estimated from 24 h in vitro gas production. In the digestibility study, 12 wethers fitted with rumen canula were housed in metabolic crates and allotted to four treatment diets (i. e., D0, D10, D20 and D30) constituted from fresh S. almum and pre-wilted C. benghalensis in a randomized complete block design. The control diet (D0) was 3 kg fresh S. almum (≈535.5 g DM/wether/d about 30 g/kg LW), whereas D10, D20 and D30 were D0 +300, 600 or 900 g of wilted C. benghalensis (≈34, 68 or about 102 g DM/wether/d), respectively. The study lasted for 21 d. Dry matter, fibre and TEP content increased (P<0.001) with maturity of the forage, whereas those of CP and EE decreased (P<0.0001) over the same period. Amino acids (AA) also declined with maturity (P<0.05). Rumen degradability of DM and OM were unaffected, but DM intake increased linearly (P<0.0001) at a decreasing rate (Q: P<0.05) and DM digestibility (DMD) and N intake increased linearly (P<0.01 and P<0.0001, respectively) as level of C. benghalensis in the diet increased. Results indicate that advancing maturity affected chemical composition, but not rumen degradability, of C. benghalensis and also demonstrated that inclusion of C. benghalensis in S. almum diet improved intake, digestibility and N intake, suggesting its potential use as a feed supplement.