Seasonal grazing rates and food processing by tropical herbivorous fishes

Seasonal variability in grazing rates and food-processing characters were assessed for three abundant fishes in a tropical rocky shore: the damselfish Stegastes fuscus , the parrotfish Sparisoma atomarium , and the surgeonfish Acanthurus bahianus . Significant differences were found in grazing rates among hour of day and seasons, and in food-processing characters among seasons for the three fishes. Grazing rates for S. atomarium and A. bahianus peaked at 1300 and 1400 hours for S. fuscus . Three main periods of different intensity in bite rates, low, intermediate and intense, were identified for all fishes. As expected, total bite rates, ingestion rates and gut fullness were highest in A. bahianus , the largest species studied, followed by S. atomarium and S. fuscus. S. atomarium with fused jaw teeth, holds the highest bite size and S. fuscus the lowest one. Gut turnover was high for S. fuscus and similar for S. atomarium and A. bahianus . Grazing rates and food-processing characters seem to vary between seasons not only due to changes in temperature, but also affected by other factors. Fishes employ different food-processing mechanisms and bear some differences in food-processing characters to achieve optimal energetic supplies from a poor nutrient food resource.     

Relationship between roving behaviour and the diet and client composition of the cleaner fish Labroides bicolor

Diet analyses and observations of cleaning behaviour of two cleaner fishes revealed that Labroides bicolor fed more on client mucus, but Labroides dimidiatus fed more on ectoparasites, and that L. bicolor interacted with fewer species (36 species) compared with L. dimidiatus (44 species). The client species which contributed most to the dissimilarity between cleaner species were the dusky farmerfish Stegastes nigricans and bicolor chromis Chromis margaritifer damselfishes, which L. dimidiatus interacted with more often than L. bicolor, and the striated Ctenochaetus striatus and brown Acanthurus nigrofuscus surgeonfishes, which L. bicolor interacted with more; L. bicolor interacted with all parrotfishes (Scaridae) more. These results confirm the importance of repeated interactions and partner choice in determining the nature of interactions in mutualisms.     

Size-selective predation by the cleaner fish Labroides dimidiatus

A comparison of the size-frequency distribution of parasitic gnathiid isopod larvae in the diet of the cleaner fish Labroides dimidiatus and on six host fish species ( Chlorurus sordidus, Ctenochaetus striatus, Hemigymnus melapterus, Scolopsis bilineatus, Siganus doliatus, Thalassoma lunare ) was made on one occasion. The comparison was repeated with Hemigymnus melapterus on three occasions and between two islands in Australia. L. dimidiatus selected larger gnathiids at all times at Lizard Island but not at Heron Island. Size-selective predation by L. dimidiatus suggests any potential effect of cleaner fish on parasites may vary according to the size of parasite. However, this effect appears to vary spatially.     

Food, feeding and growth rates of peracarid macro-decomposers in a Ria Formosa salt marsh, southern Portugal

The diet, feeding rates and growth rates of three species of isopod and three species of amphipod from a Ria Formosa salt marsh in southern Portugal are compared to test the hypotheses that the relative success of amphipods as macro-decomposers in salt marshes worldwide can be a) attributed to their utilizing a distinctly different range of potentially available food resources and b) attributed to them using similar food resources but at different rates.The first hypothesis was tested using a combination of gut contents analysis, stable isotope analysis and multiple-choice food preference tests. The results of all three analyses showed that there was a very broad overlap in the resource utilization curves for these species for the most abundant potential foods available in the upper salt marsh. The first hypothesis was therefore rejected.The second hypothesis was tested with palatability experiments in which consumption rates of each of the test animals were compared for each potential food offered alone. The amphipods ate all five of the foods significantly faster, consuming from 3-73× more food per unit mass than the isopods.Analyses of their relative growth rates from when released from the marsupium until first breeding, showed that amphipods have a faster growth rate than isopods in the field which is consistent with other traits in their rapid development-high fecundity life-history strategy. We conclude that these data support the second hypothesis and that their morphological adaptations to a shredding, high ingestion-rate rapid gut turnover digestive strategy enable them to have a more efficient resource acquisition rate than the slower growing, lower fecundity and slower ingestion-rate longer gut throughput time strategy of most isopods.     

Meals for two: foraging activity of the butterflyfish Chaetodon striatus (Perciformes) in southeast Brazil.

The banded butterflyfish (Chaetodon striatus) from the tropical and subtropical western Atlantic is a territorial, diurnal forager on benthic invertebrates. It is usually seen moving singly or in pairs, a few meters above the sea floor. We studied the foraging activity of C. striatus on rocky reefs in southeastern Brazil. This fish spent about 11 h and 30 min per day on feeding activities, and preferred colonies of non-scleratinian anthozoans over sandy and rocky substrata while foraging. The lowest feeding rates were recorded in the early morning and late afternoon, but we found no further differences between feeding rates throughout the day. We also found no differences between the feeding rates of paired and single individuals.     

Isolation and comparison of two molecular species of the BAL 31 nuclease from Alteromonas espejiana with distinct kinetic properties

The extracellular nuclease from Alteromonas espejiana sp. BAL 31 can be isolated as two distinct proteins, the "fast" (F) and "slow" (S) species, both of which have been purified to homogeneity. The F and S species of the nuclease have molecular weights, respectively, of 109 X 10(3) and 85 X 10(3), and both are single polypeptide chains with an isoelectric pH near 4.2. Both species catalyze the degradation of single-stranded and linear duplex DNAs to 5'-mononucleotides. The degradation of linear duplex DNA occurs through a terminally directed hydrolysis mechanism that results in the removal of nucleotides from both the 3' and 5' ends. Apparent Michaelis constants (Km) have been obtained for the exonuclease activities of both species and for the activity against single-stranded DNA of the S species. The Km for the hydrolysis of single-stranded DNA catalyzed by the F species has not been obtained because the reaction velocity was maximal even at the lowest substrate concentrations accessible in the photometric assay. The ratio of the turnover numbers for the exonuclease activities of the two species indicates that the F species will shorten linear duplex DNA at a rate 27 +/- 5 (S.D.) times faster than an equimolar concentration of the S species in the limit of high substrate concentration, while the corresponding ratio for the activities against single-stranded DNA (1.2 +/- 0.1) shows that the two species are similar with respect to hydrolysis of this substrate. In the limit of high substrate concentrations, the F and S species break phosphodiester bonds in single-stranded DNA at rates 1.3 +/- 0.3 and 33 +/- 2 times those for the exonucleolytic degradation of linear duplex DNA, respectively. It has not been established whether the two species are physically related.     

Are levels of digestive enzyme activity related to the natural diet in passerine birds?

Digestive capabilities, such as the rates nutrient hydrolysis and absorption, may affect energy intake and ultimately feeding behavior. In birds, a high diversity in gut biochemical capabilities seems to support the existence of a correlation between the morphology and physiology of the intestinal tract and chemical features of the natural diet. However, studies correlating the activity of digestive enzymes and the feeding habits at an evolutionary scale are scarce. We investigated the effect of dietary habits on the digestive physiological characteristics of eight species of passerine birds from Central Chile. The Order Passeriformes is a speciose group with a broad dietary spectrum that includes omnivorous, granivorous and insectivorous species. We measured the activity of three enzymes: maltase, sucrase and aminopeptidase-N. Using an autocorrelation analysis to remove the phylogenetic effect, we found that dietary habits had no effect on enzymatic activity. However, we found that granivorous and omnivorous species had higher levels of disaccharidase activities and insectivores had the lowest. The major difference in enzymatic activity found at the inter-specific level, compared to the reported lower magnitude of enzyme modulation owing to dietary acclimation, suggests that these differences to some extent have a genetic basis. However, the lack of a clear association between diet categories and gut physiology suggested us that dietary categorizations do not always reflect the chemical composition of the ingested food.     

Diet and trophic plasticity of an herbivorous blenny Scartella cristata of subtropical rocky shores

The goals of the present study were to investigate the feeding rates of Scartella cristata, accounting for different water temperature regimes, and to analyse spatial and seasonal variations in its diet. The feeding rate of S. cristata was higher in warmer waters and was not correlated with season. A typical herbivorous diel feeding pattern was observed, with a steady increase in bite rate throughout the morning until a plateau in the early afternoon, followed by an abrupt decrease until the end of the daylight period. The gut contents of S. cristata included at least 41 different items. Detritus and algae (mainly filamentous) comprised most of the bulk of S. cristata's diet. Scartella cristata also exhibited significant seasonal and spatial variability in its diet. This study highlights the importance of detritus within the epilithic algal matrix in the diet of S. cristata and pinpoints that, as in coral reefs, the detrital pathway exerts an important role in the trophodynamics of subtropical rocky shores where these fish are abundant.     

Evidence for domestication of Lens nigricans (M.Bieb.) Godron in S Europe

Evidence for domestication of Lens nigricans (M.Bieb.) Godron in S Europe. Small disjunct populations of the wild lentil Lens nigricans were found in secondary and man-made habitats throughout S Europe. Much larger populations of this species were found in primary habitats in SE Spain, S Italy and along the Adriatic coast of Yugoslavia. The majority of the L. nigricans populations were cytogenetically alike. One population differed from them by one reciprocal translocation, and another two by four chromosomal rearrangements. The L. nigricans accessions from S Europe were invariably cross-incompatible with L. nigricans of the Middle-East and with the cultivated lentil L. culinaris. The latter two were cross-compatible and their hybrids partially fertile. The existence of small L. nigricans populations in man-made habitats was interpreted as escapes from cultivation. Being cross-incompatible with L. culinaris these L. nigricans populations apparently were derived from a domesticated form of L. nigricans.     

Chronic spearfishing may indirectly affect reef health through reductions in parrotfish bite rates

The grazing behaviour of two Caribbean parrotfish, a fished species, the stoplight parrotfish Sparisoma viride and a non-fished species, the striped parrotfish Scarus iseri, were studied in the presence (fished site) and absence (marine reserve) of chronic spearfishing activity. Diurnal feeding periodicity did not differ between the sites in either species: roving individuals had significantly higher bite rates in the afternoon, while territorial individuals foraged consistently throughout the day. Mean bite rate varied between sites in both species. Abundance, biomass and bite rates of S. viride were all significantly higher within the reserve, except for roving S. viride which had a higher mean bite rate in the afternoon outside the reserve compared with within it, attributable to maximisation of feeding in the afternoon when fishing risk was lower. Scarus iseri mean abundance and bite rate were greater outside the reserve, potentially because reduction in large territorial herbivores allowed S. iseri to feed more rapidly. By reducing the grazing potential of the remaining S. viride individuals the effect of fishing is greater than would be predicted from biomass changes alone. Less grazing by S. viride would not be compensated for by the increase in grazing by S. iseri because the latter feeds on different algae. Spearfishing of key parrotfish species reduces grazing potential directly by extraction and indirectly by changing behaviour.     

Which components of diet quality affect retention time of digesta in seabirds?

1. The nature of the diet can affect the gut retention time of food consumed by an animal, and a theoretical framework has been developed to explain this in terms of optimal digestion rates. However, diets may differ in a number of different attributes, all of which may separately affect the optimal length of time that they are retained in the gut.
2. Here an attempt is made to elucidate which of these features are important in determining gut retention time of different fish species when fed to nine north Atlantic seabird species, and discuss the different potential optimization criteria for retention time in seabirds.
3. Retention times of Lesser Sandeel ( Ammodytes marinus Raitt.) were shortest, and this species was also rapidly broken down in vitro . Sprat ( Sprattus sprattus (L.)) took longer to be broken down in vitro than Whiting ( Merlangius merlangus (L.)), and also had a high energy and lipid content, which might be expected to result in slow digestion; yet retention times of the two species were similar.
4. Meal size also had an important effect on gut retention times, large meals being retained for longer in the gut than small meals, apparently because of an upper limit on the peak excretion rate.
5. Diet and meal-size related characteristics are important factors influencing prey profitability, prey selection and foraging patterns in seabirds.     

武汉东湖南部湖汊的鼓藻类

从1963年9月到1964年12月,作者在武汉东湖南部的湖汊定点采得48号藻类标本,其鼓藻类十分丰富,经鉴定共有20个属,164个种,75个变种和13个变型。其中有2个新种、7个新变种和2个新变型,12个种、25个变种和5个变型是中国的新记录;在四季中出现频率较高的优势种类有11个种和1个变种。在不同季节共6次所采得的鼓藻种类的统计结果得出,在夏季(6月、8月)的种类最多,秋季和冬季(9月、10月、12月)次之,春季(4月)最少。在东湖252个鼓藻类的分类单位中,热带、亚热带类群共有45个,其中的19个是南亚和东南亚地区特有或普遍分布的类群,13个是以广西为模式产地的类群,从而反映武汉地区鼓藻类区系具有亚热带类型的特点,并与南亚和东南亚的鼓藻类区系关系密切。     

Post-engorgement dynamics of haemagglutination activity in the midgut of phlebotomine sandflies

Abstract. Haemagglutination activity (HA) was studied in gut extracts of both sexes of adults of six sandfly species. HA was sex dependent, with the activity in males more than 50 times lower man that of unfed females. In females, high HA was demonstrable in both the thoracic and abdominal midgut but not in the hindgut. In unfed flies the activity was similar in the midgut wall and the gut contents whereas, in fed females, a high increase was seen in the midgut contents. After blood-feeding, HA was elevated, reaching peak titres 2 days later and then falling to the base level or less immediately after defaecation. The magnitude of the HA response differed according to species, ranging from 2-fold in Lutzomyia carmelinoi up to 16-fold in Phlebotomus duboscqi. Quantitative differences between sandflies in their HA response may influence their ability to support the development of Leishmania spp.     

Activity patterns and resource use by sheep and red deer grazing across a grass/heather boundary

Diet selection and activities of sheep and red deer grazing alone and together across a grass (primarily Lolium perenne/Agrostis capillaris ) and heather ( Calluna vulgaris ) boundary, between July and October, are described.
Throughout the experiment, both animal species had a much higher proportion of grass than heather in their diet. Time spent grazing on each type of vegetation was similarly greater on grass, and the bite rates of the animals were also more rapid on the grass than on the heather.
Red deer spent more time grazing per 24 hours than did sheep, with sheep grazing less during darkness hours than red deer. Total grazing time of both species did not decrease with decreasing daylength from July to October.
There were no consistent differences in the diurnal patterns of activity of sheep and red deer, with both species showing 2-3 large grazing peaks per day.
There were no consistent effects of mixing sheep and deer on their grazing behaviour and diet composition.     

Desmids from Southern Bays of the Donghu Lake,Wuhan, China

A total of 48 algae samples were collected from southern bays of the Donghu Lake from September in 1963 to December in 1964．The desmids were very plentiful,164 species,75 varieties and 13 forms belonging to 20 genera were identified．Among these,two species,seven varieties and two forms are new to science**,and 12 species,25 varieties and five forms are recorded for the first time in China．The dominant species with frequent occurrence were 11 species and one variety in four seasons． The result of counting and analysing the samples collected in different seasons (six times for each) shows that the number of the taxa of Desmids in summer (June and August)was the highest,that in autumn and winter (September,October and December) the next,and that in spring (April) is the lowest．Fourty five of 252 desmids taxa are tropical and subtropical,among which 19 are either endemic to or common in S and SE Asia． The desmid flora of Wuhan district is therefore subtropical in nature and closely related to the S and     

Food and feeding relationships of fish in the Sudd swamps (River Nile, southern Sudan)

The gut contents of 37 species of R. Nile fish are described. Classification according to diet shows four species to be mud-feeders, three to be microherbivores, two to be macroherbivores and five to be omnivores. The remaining majority (23) are categorized as carnivorous and comprise one neuston-feeder, one zooplanktivore, six bottom-feeders, seven browsers in vegetation and eight macropredators. Food webs are proposed for three major ecological zones, namely the open-water and submerged vegetation of a river-lake, the floating fringe of Eichhornia crassipes and the seasonally flooded grassland.     

Endogenous triglyceride turnover in liver and plasma of the dog

Radioactive glycerol and S(f) > 20 lipoproteins labeled with it were used to study turnover of plasma S(f) > 20 and hepatic triglyceride in anesthetized dogs. From specific activity-time curves of these lipids after an injection of labeled material, a tentative and incomplete model for the kinetics of endogenous hepatic and plasma triglyceride was defined and partially validated. Pool sizes and turnover rates of triglyceride in liver and S(f) > 20 lipoproteins of plasma were then calculated in seven dogs. Hepatic triglyceride was composed of two compartments: 60% metabolically inert and 40% metabolically active. Although communication between these hepatic compartments surely occurred during the time course of these studies, it was not sufficient to be detected by our present methods. The metabolically active compartment turned over as a single pool but with two destinations: a quite variable proportion (an average of 61%) was secreted into plasma as S(f) > 20 triglyceride, and an average of 39% was presumably hydrolyzed within the liver. The fractional turnover rate of plasma S(f) > 20 triglyceride was 2-3 times that of hepatic triglyceride. This finding, and the parallel decline of specific activities of plasma S(f) > 20 and liver triglyceride after injection of labeled glycerol, confirm the rate-determining role of hepatic triglyceride. In this respect the dog differs importantly from man. Though turnover rates of plasma S(f) > 20 triglyceride fell in the same range in men and dogs, the relationship of turnover rate to plasma concentration of this lipid differed greatly between them. The model for the dog does resemble that previously reported for man, however, in the lack of major recycling of intact plasma triglyceride between the liver and plasma. Lack of such recycling, however, does not exclude return of plasma triglyceride into a hepatic triglyceride sink. The amount of such unidirectional uptake, if any, could not be determined by these techniques.     

Spatial distribution and coexistence of monogenean gill parasites inhabiting two damselfishes from Moorea island in French Polynesia

The ectoparasite fauna of two damselfishes, Stegastes nigricans and Dascyllus aruanus, from Moorea Island in French Polynesia was investigated. Gills of these damselfishes were infected with congeneric Monopisthocotylea Monogenea belonging to the genus Haliotrema. Stegastes nigricans were found to harbour a guild of three Haliotrema species whereas only one species inhabited D. aruanus. Microhabitat distribution, inter- and intraspecific competition and interspecific associations on the gill were studied. Observations on site preference revealed no spatial segregation between the three congeneric species inhabiting the gills of S. nigricans. Juvenile and adult monogeneans of that guild occurred on the same microhabitat. The dominant species Haliotrema sp. 1 did not expand on the microhabitat when the intensity of infection increased. Interspecific association tests revealed positive and negative associations. Haliotrema sp. 4 expanded its distribution on the gills of Dascyllus aruanus when the intensity of infection increased suggesting the likelihood of intraspecific competition. Juvenile and adult monogeneans of Haliotrema sp. 4 appeared to segregate as a result of intraspecific competition. This competition may exist to enhance resource availability when the gill habitat is limited. Overlaps between niche breadth and species microhabitat were revealed for monogenean species inhabiting S. nigricans. Interspecific competition did not appear to play an important role in the distribution of S. nigricans congeneric ectoparasites. Reinforcement of reproductive barriers may have led to the avoidance of hybridization.     

Intake of Meat Proteins Substantially Increased the Relative Abundance of Genus Lactobacillus in Rat Feces

Diet has been shown to have a critical influence on gut bacteria and host health, and high levels of red meat in diet have been shown to increase colonic DNA damage and thus be harmful to gut health. However, previous studies focused more on the effects of meat than of meat proteins. In order to investigate whether intake of meat proteins affects the composition and metabolic activities of gut microbiota, feces were collected from growing rats that were fed with either meat proteins (from beef, pork or fish) or non-meat proteins (casein or soy) for 14 days. The resulting composition of gut microbiota was profiled by sequencing the V4-V5 region of the 16S ribosomal RNA genes and the short chain fatty acids (SCFAs) were analyzed using gas chromatography. The composition of gut microbiota and SCFA levels were significantly different between the five diet groups. At a recommended dose of 20% protein in the diet, meat protein-fed rats had a higher relative abundance of the beneficial genus Lactobacillus, but lower levels of SCFAs and SCFA-producing bacteria including Fusobacterium, Bacteroides and Prevotella, compared with the soy protein-fed group. Further work is needed on the regulatory pathways linking dietary protein intake to gut microbiota.     

Impacts of silica-based defences in grasses on the feeding preferences of sheep

Grasses, which dominate many terrestrial ecosystems, sustain high densities of grazing mammals, so are of great economic and ecological importance. Traditionally, grasses are thought to be adapted to tolerate grazing rather than defend against it; however, silica deposited in the leaves of grasses has recently been shown to act as a feeding deterrent to invertebrate herbivores and small mammals. This study assesses whether silica is effective as a feeding deterrent to larger mammalian herbivores. We assess the impact of manipulated silica levels in five grass species on the feeding preferences of sheep both within and between grass species.Sheep feeding behaviour was driven by between-species differences in palatability. Hence, within a single species silica addition did not cause significant changes in feeding preference. However, there were significant differences in both the feeding preferences and bite rates between grass species, and these differences were much more marked when the grasses had been exposed to high levels of silica. The impacts that silica had on preference were least pronounced in palatable species (e.g. Poa annua) compared with less-palatable species (e.g. Brachypodium pinnatum and Festuca ovina). Sheep fed for longer, took more bites and had a higher bite rate on the grass species with the lowest leaf silica concentrations, namely P. annua.Sheep were less affected by silica defences than smaller, non-ruminant herbivores, but the changes in species preference rankings caused by silica suggest it may lead to changes in sward composition. Further, in species that are already relatively low in palatability, silica-induced reductions in bite rate could potentially reduce forage intake rates, with consequences for sheep performance.