Ammonia excretion increased and urea excretion decreased in urine of a new world nectarivorous bat with decreased nitrogen intake

We determined the effect of water and nitrogen intake on nitrogenous waste composition in the nectarivorous Pallas's long-tongued bat Glossophaga soricina (Phyllostomidae) to test the hypothesis that bats reduce excretion of urea nitrogen and increase the excretion of ammonia nitrogen as nitrogen intake decreases and water intake decreases. Because changes in urine nitrogen composition are expected only in animals whose natural diets are low in nitrogen and high in water content, we also measured maintenance nitrogen requirements (MNR). We hypothesized that, similar to other plant-eating vertebrates, nectarivorous bats have low MNR. Our nitrogen excretion hypothesis was partly proved correct. There was an increase in the proportion of N excreted as ammonia and a decrease in the proportion excreted as urea in low-nitrogen diets. The proportion of N excreted as ammonia and urea was independent of water intake. Most individuals were ureotelic (n = 28), and only a few were ureo-ammonotelic (n = 3) or ammonotelic (n = 2). According to our nitrogen requirement hypothesis, apparent MNR (60 mg kg(-0.75) d(-1)) and truly digestible MNR (54 mg N kg(-0.75) d(-1)) were low. A decrease in urea excretion in low-nitrogen diets may result from urea recycling from liver to the gut functioning as a nitrogen salvage system in nectarivorous bats. This mechanism probably contributes to the low MNR found in Pallas's long-tongued bats.     

Choice and constraint in a Papua New Guinean food quest

Historical factors and lineage affiliation are interpreted as constraining choice of sweet potato or sago as a major source of starch by Etolo family groups. The annual scheduling regime encouraged an association between the primary mode of starch production and the primary technique for obtaining game mammals. An emphasis upon sweet potato was linked to trapping and an emphasis upon sago was linked to hunting. For larger family groups whose membership was older, the preceding constraints were relaxed. By manipulating residential affiliation or the composition of economic units, people could offset constraints of history, lineage affiliation, and family size. Within the framework of those constraints there was much flexibility in the food-getting choices people made. At the level of household communities, trapping and hunting behavior were not obviously patterned around concerns of available prey or energetic efficiency.     

Will travel for food: spatial discounting in two new world monkeys

Nonhuman animals steeply discount the future, showing a preference for small, immediate over large, delayed rewards. Currently unclear is whether discounting functions depend on context. Here, we examine the effects of spatial context on discounting in cotton-top tamarins (Saguinus oedipus) and common marmosets (Callithrix jacchus), species known to differ in temporal discounting. We presented subjects with a choice between small, nearby rewards and large, distant rewards. Tamarins traveled farther for the large reward than marmosets, attending to the ratio of reward differences rather than their absolute values. This species difference contrasts with performance on a temporal task in which marmosets waited longer than tamarins for the large reward. These comparative data indicate that context influences choice behavior, with the strongest effect seen in marmosets who discounted more steeply over space than over time. These findings parallel details of each species' feeding ecology. Tamarins range over large distances and feed primarily on insects, which requires using quick, impulsive action. Marmosets range over shorter distances than tamarins and feed primarily on tree exudates, a clumped resource that requires patience to wait for sap to exude. These results show that discounting functions are context specific, shaped by a history of ecological pressures.     

Small world patterns in food webs

The analysis of some species-rich, well-defined food webs shows that they display the so-called small world behavior shared by a number of disparate complex systems. The three systems analysed (Ythan estuary web, Silwood web and the Little Rock lake web) have different levels of taxonomic resolution, but all of them involve high clustering and short path lengths (near two degrees of separation) between species. Additionally, the distribution of connections P(k) which is skewed in all the webs analysed shows long tails indicative of power-law scaling. These features suggest that communities might be self-organized in a non-random fashion that might have important consequences in their resistance to perturbations (such as species removal). The consequences for ecological theory are outlined.     

Neutral amino acids in the brain: changes in response to food ingestion

Abstract— The brain levels of each of the aromatic and branched-chain amino acids change 2 h after fasting rats begin to consume either a carbohydrate-fat diet or a similar diet containing 18% or 40% protein. Carbohydrate-fat ingestion elevates the concentrations of each of the aromatic amino acids in brain, while substantially depressing those of the branched-chain amino acids. The inclusion of protein in this diet suppresses the increases in brain aromatic amino acids and attenuates the decreases in the branched-chain amino acids. The changes in the brain level of each neutral amino acid following the ingestion of any of these diets correlate extremely well with the effects of the diet on the serum neutral amino acid pattern, specifically on the serum concentration ratio of each neutral amino acid to the sum of the other neutral amino acids. The diet-induced changes in the brain level of each of the amino acids also correlate surprisingly well with the calculated rate of brain influx for each amino acid.     

Gastric inhibitory polypeptide as an endogenous factor promoting new bone formation after food ingestion

Calcium plays a fundamental role as second messenger in intracellular signaling and bone serves as the body's calcium reserve to tightly maintain blood calcium levels. Calcium in ingested meal is the main supply and inadequate calcium intake causes osteoporosis and bone fracture. Here, we describe a novel mechanism of how ingested calcium is deposited on bone. Meal ingestion elicits secretion of the gut hormone gastric inhibitory polypeptide (GIP) from endocrine K cells in the duodenum. Bone histomorphometrical analyses revealed that bone formation parameters in the mice lacking GIP receptor (GIPR(-/-)) were significantly lower than those of wild-type (GIPR(+/+)) mice, and that the number of osteoclasts, especially multinuclear osteoclasts, was significantly increased in GIPR(-/-) mice, indicating that GIPR(-/-) mice have high-turnover osteoporosis. In vitro examination showed the percentage of osteoblastic cells undergoing apoptosis to be significantly decreased in the presence of GIP. Because GIPR(-/-) mice exhibited an increased plasma calcium concentration after meal ingestion, GIP directly links calcium contained in meal to calcium deposition on bone.     

Animal locomotion: a new spin on bat flight

Biologists and engineers have long struggled to understand the hovering flight of insects, birds, and bats. The enormous diversity of these groups would suggest they fly using a variety of mechanisms, but a new study shows that hovering bats use the same aerodynamic mechanisms as do moths and other insects.     

Contrasting genetic structure in two co-distributed species of old world fruit bat

The fulvous fruit bat (Rousettus leschenaulti) and the greater short-nosed fruit bat (Cynopterus sphinx) are two abundant and widely co-distributed Old World fruit bats in Southeast and East Asia. The former species forms large colonies in caves while the latter roots in small groups in trees. To test whether these differences in social organization and roosting ecology are associated with contrasting patterns of gene flow, we used mtDNA and nuclear loci to characterize population genetic subdivision and phylogeographic histories in both species sampled from China, Vietnam and India. Our analyses from R. leschenaulti using both types of marker revealed little evidence of genetic structure across the study region. On the other hand, C. sphinx showed significant genetic mtDNA differentiation between the samples from India compared with China and Vietnam, as well as greater structuring of microsatellite genotypes within China. Demographic analyses indicated signatures of past rapid population expansion in both taxa, with more recent demographic growth in C. sphinx. Therefore, the relative genetic homogeneity in R. leschenaulti is unlikely to reflect past events. Instead we suggest that the absence of substructure in R. leschenaulti is a consequence of higher levels of gene flow among colonies, and that greater vagility in this species is an adaptation associated with cave roosting.     

Physiological responses to food deprivation in the house sparrow, a species not adapted to prolonged fasting

Many wild birds fast during reproduction, molting, migration, or because of limited food availability. Species that are adapted to fasting sequentially oxidize endogenous fuels in three discrete phases. We hypothesized that species not adapted to long fasts have truncated, but otherwise similar, phases of fasting, sequential changes in fuel oxidization, and similar changes in blood metabolites to fasting-adapted species. We tested salient predictions in house sparrows (Passer domesticus biblicus), a subspecies that is unable to tolerate more than ～32 h of fasting. Our main hypothesis was that fasting sparrows sequentially oxidize substrates in the order carbohydrates, lipids, and protein. We dosed 24 house sparrows with [(13)C]glucose, palmitic acid, or glycine and measured (13)CO(2) in their breath while they fasted for 24 h. To ascertain whether blood metabolite levels reflect fasting-induced changes in metabolic fuels, we also measured glucose, triacylglycerides, and β-hydroxybutyrate in the birds' blood. The results of both breath (13)CO(2) and plasma metabolite analyses did not support our hypothesis; i.e., that sparrows have the same metabolic responses characteristic of fasting-adapted species, but on a shorter time scale. Contrary to our main prediction, we found that recently assimilated (13)C-tracers were oxidized continuously in different patterns with no definite peaks corresponding to the three phases of fasting and also that changes in plasma metabolite levels accurately tracked the changes found by breath analysis. Notably, the rate of recently assimilated [(13)C]glycine oxidization was significantly higher (P < 0.001) than that of the other metabolic tracers at all postdosing intervals. We conclude that the inability of house sparrows to fast for longer than 32 h is likely related to their inability to accrue large lipid stores, separately oxidize different fuels, and/or spare protein during fasting.     

广东省蝙蝠三新记录

我们于 1 999年 1 0月、2 0 0 0年 4～ 1 0月 ,分别在广州市郊和粤北地区采到标本 1 8种 32 5号 ,其中大耳菊头蝠 (Ｒｈｉｎｏｌｏｐｈｕｓｍａｃｒｏｔｉｓ)、普氏蹄蝠 (Ｈｉｐｐｏｓｉｄｅｒｏｓｐｒａｔｔｉ)和小伏翼 (Ｐｉｐｉｓｔｒｕｌｌｕｓｍｉｍｕｓ) 3种为广东省第一次发现 ,应为广东省新记录[1] (至此 ,广东省翼手目应有 2 8种 )。1　大耳菊头蝠ＲｈｉｎｏｌｏｐｈｕｓｍａｃｒｏｔｉｓＢｌｙｔｈ(封面照片 )　 1 999年 1 0月 2日和 2 0 0 0年 8月 5日采于龙门县平陵镇地藏旁洞内 ,海拔 1 50ｍ ,捕获 2♂ 1♀ ,采集号为广 991 33…     

Defining the abundance body-size constraint space: data from a real food web

Using density and body-size data for a well-documented food web, the Ythan estuary, Aberdeenshire, we show that the shape of the constraint space is broadly similar to that proposed by Brown, and the slope (regression coefficient) of the plot of the central tendency is not significantly different from global or community data sets. However, the steepness of the plot is very sensitive to the degree of taxonomic resolution of species entities, particularly those of small body-size, although the overall shape of the constraint space does not change. When more fully resolved, the regression slope differs markedly from those of most freshwater and terrestrial studies. In addition, the upper bound of the constraint space is, contrary to theoretical expectations, insensitive to gross changes in the system's productivity. The dramatic increase in productivity that has led to an increase in abundance of invertebrates in the Ythan does not visibly affect the upper bound of the constraint space. Our results show that the traditional approach to comparing systems by the regression slopes of central trends is probably meaningless unless data sets are resolved to a similar degree of taxonomic resolution, and that detecting productivity effects on the location of the upper bound will be difficult.     

Salinity as a constraint affecting food and habitat choice of mussel-feeding diving ducks

Observations of freshwater drinking in Eiders feeding primarily on mussels led us to hypothesize that the highly saline sea water enclosed in mussels could cause salt-related dehydration problems in the ducks, since they consume entire mussels. The proportion of sea water increases with increasing mussel size. Smaller duck species are more sensitive to the higher salt content of larger mussels than are larger ducks; however, salt stress may be avoided by feeding in habitats with lower salinity, by feeding on less salty food items, by utilizing smaller mussels, by drinking fresh water, or by employing low energy foraging techniques. A possible evolutionary strategy for solving the salt problem might be to increase body mass, enabling ducks to utilize larger mussels without passing an upper salt consumption limit. At the same time, foraging on larger mussels is more economical. Although large size facilitates the utilization of brackish and marine environments, it may be selected against in ducks breeding in fresh water, where fish competition may reduce optimal food item size. In conclusion, salinity is an important habitat barrier in both breeding and overwintering diving ducks, but there are various ways of crossing this barrier. To understand better how ducks utilize their habitats, however, it is necessary to measure habitat salinity levels and the size of both ducks and their preferred and less-preferred food types.     

Cereal genomics: ushering in a brave new world

Plant Molecular Biology -     

Cardiovascular autonomic response to food ingestion in patients with gastritis: a comparison between Helicobacter pylori-positive and -negative patients

BACKGROUND: Feeding evokes a cardiovascular response associated to an increased sympathetic drive. The role of the parasympathetic component in this regard is less clear. Improvement of postprandial vasovagal complaints after Helicobacter pylori eradication in three cases led us to assess autonomic response to feeding in H. pylori-positive patients in search for an exacerbated parasympathetic response. MATERIAL AND METHODS: Patients with mild or moderate chronic histologic gastritis were studied. Subjects with the same diagnosis but testing negative for H. pylori were used as controls. Noninvasive cardiovascular tests were applied before and after feeding. RESULTS: On sympathetic tests, standing postprandial blood pressure was lower than preprandially in 5/12 H. pylori-positive patients and in 0/9 controls, p = .045. Resting postprandial BP on handgrip test was significantly lower than preprandially only in H. pylori-positive patients (71 +/- 8 versus 76 +/- 6 mmHg, p = .0068). Regarding parasympathetic tests, the 4-s unloaded exercise revealed greater initial heart rate response to unloaded cycling after feeding than preprandially again only in H. pylori-positive patients (1.40 +/- 0.20 versus 1.33 +/- 0.17, p = .0195). On tests influenced by both branches of the autonomic system, a difference was seen in the chronotropic response to handgrip. Postprandial heart rate on effort of H. pylori-positive patients was not higher than preprandially in contrast to controls [intervals between 2 consecutive R waves on electrocardiogram (R-R intervals) of 666 +/- 39 versus 685 +/- 62 ms, p = .0195], suggesting blunted sympathetic activation in the former. CONCLUSION: Supporting the observations that motivate the study, our findings indicate blunted sympathetic reactivity and exacerbated vagal response to feeding in H. pylori-positive patients.     

Old world versus new world: life-history alterations in a successful invader introduced across Europe

We examined differences in pumpkinseed (Lepomis gibbosus) life-history traits between native North American and introduced European populations, and tested three life-history predictions related to the effect of temperature, growth, waterbody size, and the presence/absence of predators on native and non-native populations. Pumpkinseed populations exhibit more ‘opportunistic’ traits (earlier maturity, smaller size at maturity, and higher reproductive allocation) in their introduced European range than those in their native range. Predictions of life-history traits were improved when indicators of juvenile growth rate (mean length at age 2), waterbody size (surface area), and thermal regime (air temperature degree-days above 10 °C) were incorporated into models along with continental location, but European pumpkinseed populations exhibit more opportunistic life-history traits than North American populations even when these factors are accounted for. Native pumpkinseed in waterbodies containing piscivores mature later and at a larger size, and have lower gonadosomatic indices than those in waterbodies lacking piscivores, whereas there is no significant difference in the same three life-history traits between European waterbodies containing or lacking piscivores. Because congeneric competitors of the pumpkinseed are absent from Europe, the apparent absence of a predator life-history effect there could also be due to the absence of the major sunfish competitors. In either case, the evolution and maintenance of more opportunistic traits in European pumpkinseed can likely be attributed to enemy release, and this may explain the successful establishment and spread of pumpkinseed in many parts of Europe.     

Evasive behaviour of a frog in response to bat predation

Chorusing frogs (Physalaemus pustulosus) visually detect hunting bats (Trachops cirrhosus) and models of T. cirrhosus on all but the darkest nights. Detection is apparently communicated rapidly, since all frogs in the area can quit calling withing less than a second of a T. cirrhosus arrival at the pond. Physalaemus pustulosus choruses remain silent longer following trials when a T. cirrhosus model is passed overhead than following normal shutdowns or those caused by a model of a small insectivorous bat. They often do not reduce calling in response to the normal activities of small bats.