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At least 19 recordsLinked to original sources
PubMed1981

Feeding by Actinophrys sol (Protista, Heliozoa): 1 light microscopy.

The feeding behavior of the heliozoon Actinophrys sol was investigated using the ciliate Colpidium colpoda as food. The ciliate is caught by adhesion to the arms of the heliozoon. Within 20 min the prey is enclosed by a funnel-shaped pseudopodium which progresses over the prey by the action of its differentiated leading edge. Independent Actinophrys cells may fuse together during prey capture and the early stages of prey digestion. After prey ingestion, the ciliate is lysed and the contents of the food vacuole coagulate. Much of the fluid is removed from the food vacuole and, within 4 h of feeding, the food vacuole has condensed around its coagulated contents. As food vacuole condensation occurs, the peripheral region of the heliozoon cell becomes vacuolated. The appearance of the cell and of the food vacuole remain the same for about 12 h, after which time the undigested residues in the food vacuoles are egested, fused masses of cells separate as uninucleate cells and nuclear division may occur. During feeding, the extrusomes are greatly depleted. These bodies are implicated in the processes of food capture and in the production of food vacuole membrane.

Animals↗
PubMed2004

Carnivorous pitcher plant uses free radicals in the digestion of prey.

A study of the involvement of free oxygen radicals in trapping and digestion of insects by carnivorous plants was the main goal of the present investigation. We showed that the generation of oxygen free radicals by pitcher fluid of Nepenthes is the first step of the digestion process, as seen by EPR spin trapping assay and gel-electrophoresis. The EPR spectrum of N. gracilis fluid in the presence of DMPO spin trap showed the superposition of the hydroxyl radical spin adduct signal and of the ascorbyl radical signal. Catalase addition decreased the generation of hydroxyl radicals showing that hydroxyl radicals are generated from hydrogen peroxide, which can be derived from superoxide radicals. Gel-electrophoresis data showed that myosin, an abundant protein component of insects, can be rapidly broken down by free radicals and protease inhibitors do not inhibit this process. Addition of myoglobin to the pitcher plant fluid decreased the concentration of detectable radicals. Based on these observations, we conclude that oxygen free radicals produced by the pitcher plant aid in the digestion of the insect prey.

Animals↗
PubMed2007

Density-dependent outcomes in a digestive mutualism between carnivorous Roridula plants and their associated hemipterans.

Recent studies have shown that mutualisms often have variable outcomes in space and time. In particular, the outcomes may be dependent on the density of the partners with unimodal or saturating outcomes providing stability to the mutualism. We examine density-dependent outcomes of an obligate, species-specific mutualism between a South African carnivorous plant (Roridula dentata) and a hemipteran (Pameridea) that facilitates prey digestion, but also sucks plant sap. Plants occur in sandy, leached, nitrogen-poor soils and have no digestive enzymes to digest prey. Instead they rely on obligately dependent hemipterans to supply nitrogen by digesting prey for them and defecating on their leaves. We documented the densities of Pameridea on Roridula in the field. In the greenhouse, we manipulated the hemipteran densities on Roridula and measured the mean relative growth rates of plants with differing hemipteran densities. Plants exhibited a unimodal response to the density of their mutualist partners. Those with no hemipterans had negative growth rates, suggesting that hemipterans are important in facilitating nitrogen absorption. Plants with intermediate hemipteran densities had positive growth rates but growth rates were negative under very high hemipteran densities. Our research provides support for variable and unimodal outcomes in mutualism. Unimodal outcomes may be particularly important in obligate mutualisms and this is one of the few studied outside of pollinating seed parasite mutualisms. In this system, extrinsic factors such as other predators may affect the mutualism by altering the numbers of hemipterans.

Animals↗
PubMed1985

Digestion of prey in foraminifera is not anomalous: a correlation of light microscopic, cytochemical, and HVEM technics to study phagotrophy in two allogromiids.

Correlative light, high-voltage electron and conventional electron microscopic methods were used to investigate digestion in two allogromiid foraminiferans, Allogromia sp., strain NF, and A. laticollaris Arnold. Microscopic observations showed that bacterial prey are phagocytosed by reticulopodia and are transported to the allogromiid cell body within blister-like phagosomes. Larger prey (algae, diatoms) are transported along the reticulopodial surface and are either stored extrathalamously or phagocytosed at the oral opening (peduncle). Studies of allogromiids optimally fixed and labeled with an extracellular-space label (colloidal thorium) showed that phagocytosed prey are completely enclosed by a plasma membrane envelope; this finding was corroborated by a serial-section three-dimensional reconstruction of the oral zone of one allogromiid. Cytochemical staining for acid phosphatase showed that lysosomes are absent from reticulopods but abundant in the cell body, particularly in the oral zone cytoplasm. We conclude that digestion in allogromiid foraminiferans is accomplished by a vacuole-based digestive apparatus and not by extracellular digestion within a lacunary system, as has been suggested in earlier studies.

Acid Phosphatase↗
PubMed2024

Comparative transcriptomics of Venus flytrap (Dionaea muscipula) across stages of prey capture and digestion.

The Venus flytrap, Dionaea muscipula, is perhaps the world's best-known botanical carnivore. The act of prey capture and digestion along with its rapidly closing, charismatic traps make this species a compelling model for studying the evolution and fundamental biology of carnivorous plants. There is a growing body of research on the genome, transcriptome, and digestome of Dionaea muscipula, but surprisingly limited information on changes in trap transcript abundance over time since feeding. Here we present the results of a comparative transcriptomics project exploring the transcriptomic changes across seven timepoints in a 72-hour time series of prey digestion and three timepoints directly comparing triggered traps with and without prey items. We document a dynamic response to prey capture including changes in abundance of transcripts with Gene Ontology (GO) annotations related to digestion and nutrient uptake. Comparisons of traps with and without prey documented 174 significantly differentially expressed genes at 1 hour after triggering and 151 genes with significantly different abundances at 24 hours. Approximately 50% of annotated protein-coding genes in Venus flytrap genome exhibit change (10041 of 21135) in transcript abundance following prey capture. Whereas peak abundance for most of these genes was observed within 3 hours, an expression cluster of 3009 genes exhibited continuously increasing abundance over the 72-hour sampling period, and transcript for these genes with GO annotation terms including both catabolism and nutrient transport may continue to accumulate beyond 72 hours.

Droseraceae↗
PubMed2001

Plasma-membrane H+-ATPases are expressed in pitchers of the carnivorous plant Nepenthes alata Blanco.

Nepenthes is a unique genus of carnivorous plants that can capture insects in trapping organs called pitchers and digest them in pitcher fluid. The pitcher fluid includes digestive enzymes and is strongly acidic. We found that the fluid pH decreased when prey accumulates in the pitcher fluid of Nepenthes alata. The pH decrease may be important for prey digestion and the absorption of prey-derived nutrients. To identify the proton pump involved in the acidification of pitcher fluid, plant proton-pump homologs were cloned and their expressions were examined. In the lower part of pitchers with natural prey, expression of one putative plasma-membrane (PM) H+-ATPase gene, NaPHA3, was considerably higher than that of the putative vacuolar H+-ATPase (subunit A) gene, NaVHA1, or the putative vacuolar H+-pyrophosphatase gene, NaV-HP1. Expression of one PM H+-ATPase gene, Na-PHA1, was detected in the head cells of digestive glands in the lower part of pitchers, where proton extrusion may occur. Involvement of the PM H+-ATPase in the acidification of pitcher fluid was also supported by experiments with proton-pump modulators; vanadate inhibited proton extrusion from the inner surface of pitchers, whereas bafilomycin A1 did not, and fusicoccin induced proton extrusion. These results strongly suggest that the PM H+-ATPase is responsible for acidification of the pitcher fluid of Nepenthes.

Amino Acid Sequence↗
PubMed2002

Ophidian envenomation strategies and the role of purines.

Snake envenomation employs three well integrated strategies: prey immobilization via hypotension, prey immobilization via paralysis, and prey digestion. Purines (adenosine, guanosine and inosine) evidently play a central role in the envenomation strategies of most advanced snakes. Purines constitute the perfect multifunctional toxins, participating simultaneously in all three envenomation strategies. Because they are endogenous regulatory compounds in all vertebrates, it is impossible for any prey organism to develop resistance to them. Purine generation from endogenous precursors in the prey explains the presence of many hitherto unexplained enzyme activities in snake venoms: 5'-nucleotidase, endonucleases (including ribonuclease), phosphodiesterase, ATPase, ADPase, phosphomonoesterase, and NADase. Phospholipases A(2), cytotoxins, myotoxins, and heparinase also participate in purine liberation, in addition to their better known functions. Adenosine contributes to prey immobilization by activation of neuronal adenosine A(1) receptors, suppressing acetylcholine release from motor neurons and excitatory neurotransmitters from central sites. It also exacerbates venom-induced hypotension by activating A(2) receptors in the vasculature. Adenosine and inosine both activate mast cell A(3) receptors, liberating vasoactive substances and increasing vascular permeability. Guanosine probably contributes to hypotension, by augmenting vascular endothelial cGMP levels via an unknown mechanism. Novel functions are suggested for toxins that act upon blood coagulation factors, including nitric oxide production, using the prey's carboxypeptidases. Leucine aminopeptidase may link venom hemorrhagic metalloproteases and endogenous chymotrypsin-like proteases with venom L-amino acid oxidase (LAO), accelerating the latter. The primary function of LAO is probably to promote prey hypotension by activating soluble guanylate cyclase in the presence of superoxide dismutase. LAO's apoptotic activity, too slow to be relevant to prey capture, is undoubtedly secondary and probably serves principally a digestive function. It is concluded that the principal function of L-type Ca(2+) channel antagonists and muscarinic toxins, in Dendroaspis venoms, and acetylcholinesterase in other elapid venoms, is to promote hypotension. Venom dipeptidyl peptidase IV-like enzymes probably also contribute to hypotension by destroying vasoconstrictive peptides such as Peptide YY, neuropeptide Y and substance P. Purines apparently bind to other toxins which then serve as molecular chaperones to deposit the bound purines at specific subsets of purine receptors. The assignment of pharmacological activities such as transient neurotransmitter suppression, histamine release and antinociception, to a variety of proteinaceous toxins, is probably erroneous. Such effects are probably due instead to purines bound to these toxins, and/or to free venom purines.

Animals↗
PubMed1996

Diet and snake venom evolution.

Venom composition within snake species can show considerable geographical variation, an important consideration because bites by conspecific populations may differ in symptomatology and require different treatments. The underlying causes of this phenomenon have never been explained. Here we present evidence that the variation in the venom of the pitviper Calloselasma rhodostoma (Serpentes: Viperidae) is closely associated with its diet. We also evaluated other possible causes of geographic variation in venom using partial Mantel tests and independent contrasts, but rejected both contemporary gene flow (estimated from geographical proximity) and the phylogenetic relationships (assessed by analysis of mitochondrial DNA) among populations as important influences upon venom evolution. As the primary function of viperid venom is to immobilize and digest prey and prey animals vary in their susceptibility to venom, we suggest that geographical variation in venom composition reflects natural selection for feeding on local prey.

Animals↗
PubMed2004

Enzymic and structural characterization of nepenthesin, a unique member of a novel subfamily of aspartic proteinases.

Carnivorous plants are known to secrete acid proteinases to digest prey, mainly insects, for nitrogen uptake. In the present study, we have purified, for the first time, to homogeneity two acid proteinases (nepenthesins I and II) from the pitcher fluid of Nepenthes distillatoria (a pitcher-plant known locally as badura) and investigated their enzymic and structural characteristics. Both enzymes were optimally active at pH approx. 2.6 towards acid-denatured haemoglobin; the specificity of nepenthesin I towards oxidized insulin B chain appears to be similar, but slightly wider than those of other APs (aspartic proteinases). Among the enzymic properties, however, the most notable is their unusual stability: both enzymes were remarkably stable at or below 50 degrees C, especially nepenthesin I was extremely stable over a wide range of pH from 3 to 10 for over 30 days. This suggests an evolutionary adaptation of the enzymes to their specific habitat. We have also cloned the cDNAs and deduced the complete amino acid sequences of the precursors of nepenthesins I and II (437 and 438 residues respectively) from the pitcher tissue of N. gracilis. Although the corresponding mature enzymes (each 359 residues) are homologous with ordinary pepsin-type APs, both enzymes had a high content of cysteine residues (12 residues/molecule), which are assumed to form six unique disulphide bonds as suggested by computer modelling and are supposed to contribute towards the remarkable stability of nepenthesins. Moreover, the amino acid sequence identity of nepenthesins with ordinary APs, including plant vacuolar APs, is remarkably low (approx. 20%), and phylogenetic comparison shows that nepenthesins are distantly related to them to form a novel subfamily of APs with a high content of cysteine residues and a characteristic insertion, named 'the nepenthesin-type AP-specific insertion', that includes a large number of novel, orthologous plant APs emerging in the gene/protein databases.

Amino Acid Sequence↗
PubMed2006

Early trafficking events of Mycobacterium ulcerans within Naucoris cimicoides.

The severe skin-destructive disease caused by Mycobacterium ulcerans, named Buruli ulcer, is the third most important mycobacterial disease in humans after tuberculosis and leprosy. Recently we demonstrated that M. ulcerans could colonize the salivary glands of the water bug, Naucoris cimicoides. In this study, we report that M. ulcerans may be delivered from the digested prey aspirate to the coelomic cavity via a unique headspace, the head capsule (HC). During the infected meal, we observed that M. ulcerans clusters adhered to the stylets that were retracted in the HC at the end of the meal. M. ulcerans was able to translocate from the HC to the coelomic cavity where it is phagocytosed by the plasmatocytes. These cells are subverted as shuttle cells and deliver M. ulcerans to the salivary glands. At this early stage of its parasitic life style, two other important features of M. ulcerans can be documented: first, mycolactone is not required for translocation of M. ulcerans into the HC, in contrast to the next step, colonization of the salivary glands; second, M. ulcerans clusters bind a member of the serpin protein family present in the salivary gland homogenate.

Animals↗
PubMed1992

Polypeptide cytolytic toxins from sea anemones (Actiniaria).

Biochemical and biological properties of 30 cytolytic polypeptide toxins isolated from 18 species of sea anemones (Actiniaria) are presented and classified into three groups according to their molecular mass, isoelectric points and the molecular mechanism of action. Phospholipase A2-like toxins (30 kDa) from Aiptasia pallida are dissimilar to acidic metridiolysin (80 kDa) from Metridium senile and the group of about 27 predominantly basic toxins, having a molecular mass of 16-20 or 10 kDa, inhibited by sphingomyelin. They are lethal for both invertebrates and vertebrates, cardiotoxic, cytolytic and cytotoxic. Pharmacological activities, cytotoxic and cytolytic properties are mediated, at least in part, by forming pores in lipid membranes. Channels, 1-2 nm in diameter, formed in planar lipid membranes are cation selective and rectified. The mechanisms and some characteristics of ion channel formation by the toxins in the cells as well as in artificial lipid membranes are summarized and discussed in view of the structure-function studies of the toxins. Putative biological roles of toxins, based on their channel-forming activity, in the capture and killing of prey, digestion, repelling of predators and intraspecific spatial competition are suggested.

Amino Acid Sequence↗
PubMed2001

Structural flexibility of the intestine of Burmese python in response to feeding.

The small intestine of Burmese pythons, Python molurus bivittatus, undergoes a remarkable size increase shortly after feeding. We studied the dynamics, reversibility and repeatability of organ size changes using noninvasive imaging techniques. We employed light and electron microscopy, flow cytometry and immunohistology to study the cytological mechanisms that drive the size changes of the small intestine. Within 2 days of feeding, the size of the small intestine increased to up to three times the fasting value. The size changes were fully reversible and could be elicited repeatedly by feeding. These enormous size changes were possible because the mucosal epithelium of the small intestine is a transitional epithelium that allows for considerable size changes without cell proliferation. Histological evidence suggested that a fluid pressure-pump system (lymphatic, blood pressure) was the driving force that inflated the intestinal villi. The rates of cell proliferation were not elevated immediately after feeding but peaked 1 week later when small intestine size was already declining. In contrast to the current paradigm, we suggest that the small intestine is not part of the previously proposed 'pay-before-pumping' model. Instead, the size of the python's small intestine may be upregulated without major metabolic investment. It can occur even if the individual is energetically exhausted. An evolutionary perspective of the transitional epithelium mechanism suggests superior functionality compared with the pay-before-pumping model because it allows for long periods of fasting and depletion of energy reserves, while still enabling the snake to digest prey and absorb nutrients.

Animals↗
PubMed2005

Nepenthesin, a unique member of a novel subfamily of aspartic proteinases: enzymatic and structural characteristics.

Carnivorous plants are known to secrete acid proteinases to digest prey, mainly insects, for nitrogen uptake. In our recent study, we have purified, for the first time, to homogeneity two acid proteinases, nepenthesin I (Nep I) and nepenthesin II (Nep II) from the pitcher fluid of Nepenthes distillatoria and investigated their enzymatic and structural characteristics. Both enzymes were optimally active at pH approx. 2.6 toward acid-denatured hemoglobin; the specificity of Nep I toward oxidized insulin B chain appears to be similar, but slightly wider than those of other aspartic proteinases (APs). At or below 50 degrees C both enzymes were remarkably stable; especially Nep I was extremely stable over a wide range of pH from 3 to 10 for over 30 days. This suggests an evolutionary adaptation of the enzymes to their specific habitat. We have also cloned the cDNAs and deduced the complete amino acid sequences of the precursors of Nep I and Nep II from the pitcher tissue of Nepenthes gracilis. Although the corresponding mature enzymes are homologous with ordinary pepsin-type APs, both enzymes had a high content of cysteine residues (12 residues per molecule), which are assumed to form six unique disulfide bonds as suggested by computer modeling and are thought to contribute toward the remarkable stability of Neps. Moreover, the amino acid sequence identity of Neps with ordinary APs, including plant vacuolar APs, are remarkably low (approx. 20%), and phylogenetic comparison shows that Neps are distantly related to them to form a novel subfamily of APs with a high content of cysteine residues and a characteristic insertion, named 'the Nep-type AP (NAP)-specific insertion', including a large number of novel, orthologous plant APs emerging in the gene/protein databases.

Amino Acid Sequence↗
PubMed1993

In vitro digestibility of different prey species of minke whales (Balaenoptera acutorostrata).

Information on diet composition, daily energy expenditure, energy storage and the utilization of energy in the prey are important factors when evaluating the food consumption of minke whales (Balaenoptera acutorostrata) during their summer stay in northern waters. The purpose of the present study was in this context to obtain information on the digestible energy (DE) of different prey selected by minke whales. An in vitro three-stage digestion technique, simulating the different compartments of the digestive system, has been developed. The initial step simulated the anaerobic microbial fermentation of substrate in the forestomach. The next stage included the addition of pepsin (EC 3.4.23.1)-HCl, simulating ventricle enzymic decomposition, and finally, in the third step, fresh extract from duodenal contents was used to simulate enzymic intestinal degradation of the remaining components of the food. The inoculum was normally obtained from animals which had recently eaten the prey to be tested. In such tests we obtained a dry matter disappearance (DMD) and a DE for herring (Clupea harengus) of 80.4 (SD 5.0)% (n 18) and 92.1 (SD 3.7)% (n 16) respectively, and a DMD of krill (Thysanoessa sp.) of 83.4 (SD 4.9)% (n 6). The DMD of krill was reduced to 73.8 (SD 7.3)% (n 8) while the DE was 70.6 (SD 10.4)% (n 7) when inoculum from whales which had recently eaten cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) was used. These results indicate a high digestibility of the most common species of prey in these animals, and also that the whales have little difficulty in changing from one prey species to another.

Animals↗
PubMed2001

Secondary predation: quantification of food chain errors in an aphid-spider-carabid system using monoclonal antibodies.

"Secondary predation" occurs when one predator feeds on a second predator, which has in turn eaten a target prey. Detection of prey remains within predators using monoclonal antibodies cannot distinguish between primary and secondary predation, potentially leading to quantitative and qualitative food chain errors. We report the first fully replicated experiments to measure secondary predation effects, using an aphid-spider-carabid system. Aphids, Sitobion avenae, were fed to spiders, Lepthyphantes tenuis, which were allowed to digest their prey for a range of time intervals. The spiders were then fed to carabids, Poecilus (=Pterostichus) cupreus, which were again allowed to digest their prey for set periods. The anti-aphid monoclonal antibody used to identify S. avenae remains in P. cupreus was one that detected an epitope that increased in availability over the first few hours of digestion, amplifying the signal, extending detection periods and thus increasing the chances of detecting secondary predation. Despite this, and the fact that spiders are known to digest their prey more slowly than many other predators, detection of secondary predation was only possible if the carabids were killed immediately after consuming at least two spiders which were, in turn, eaten immediately after consuming aphids. As this scenario is unlikely to occur frequently in the field it was concluded that secondary predation is unlikely to be a serious source of error during field studies.

Animals↗
PubMed2006

Morphology and preliminary enzyme characterization of the salivary glands from the predatory bug Podisus nigrispinus (Heteroptera: Pentatomidae).

Podisus nigrispinus (Dallas) is a common predator in agricultural and natural systems in Neotropical America. Its feeding strategy involves extra-oral digestion and to better understand this process its salivary glands were extracted and subjected to morphological and preliminary enzyme characterization. The salivary glands of P. nigrispinus are formed by a pair of main and accessory gland complexes. The main salivary glands are further divided into an anterior and a posterior lobe. The compartmentalization of the salivary gland complex is likely to be important for the production, activation and release of the digestive enzymes used in the extra-oral digestion of prey items. Proteases and lipase, important digestive enzymes involved in zoophagy, were detected in the salivary glands of P. nigrispinus. The prevailing trypsin-like protease activity was characterized by using the serine-protease substrate N-alpha-benzoyl-L-Arg-p-nitroanilidine (L-BApNA) and the trypsin inhibitors tosyl-L-lysine chloromethyl ketone (TLCK) and benzamidine. The KM value obtained for trypsin-like activity was 1.57 mm and the different peaks of optimum pH and temperature activity suggest the presence of multiple forms of this enzyme in P. nigrispinus. Detection of amylase activity in the salivary glands of this predator suggests its ability to digest starch and obtain nutrients from plants, which may have adaptative value under prey scarcity.

Amylases↗