Feasible mechanisms for algal digestion in the king angelfish

To determine the ability of the king angelfish Holacanthus passer to digest algae, three algal species were immersed in acidic conditions similar to that found in the stomach of fish. Only one of them was not susceptible to acidic lysis; two were affected after 40 and 60 min at pH 2·0. King angelfish have an expanded region of the intestine called here the hindgut chamber (HC) containing populations of micro-organisms. Some of these micro-organisms have the capacity to grow in cellulose, agar, and alginic acid; the main components of algal cell walls. Micro-organisms grew in carboxymethylcellulose cultures under aerobic and micro-aerobic conditions. The HC is highly vascularized, which could increase absorptive efficiency of material digested in it.     

Digestion in the cattle-tick Boophilus microplus: light microscope study of the gut cells in nymphs and females

The gut caeca of B. microplus were studied by light microscopy using paraffin and methacrylate embedded material. It has been shown that during feeding of nymphs and adults, the midgut consists of five cell types, stem cell, digest cell, secretory cells (s₁) and (s₂) and basophilic cell. The stem cell differentiates into any of the other cell types. The digest cell matures through a series of stages and has up to three generations during feeding on the host. The final generation has two distinct cell types, the first type is thought to be capable of both phagocytosis and pinocytosis. Cells of the second type are predominant at the end of feeding, and may be specialized to ingest and digest haemoglobin. The final stage of the digest series is the spent digest cell which discharges its content into the gut lumen or is excreted whole. The basophilic cell has structures which suggest that one of its functions is to transport digested materials, water and ions across the gut. Secretory cell (s₁) secretes a glycoprotein which may be a haemolysin and secretory cell (s₂) secretes the gut “colloid” mass, an acid mucopolysaccharide, which may function as an anticoagulant. Intracellular digestion leads to the breakdown of host blood and storage of lipid and glycogen in the digest cells.     

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.     

Distribution,properties, and functions of midgut carboxypeptidases and dipeptidases from Musca domestica larvae

Dipeptidase and carboxypeptidase A activities were determined in cells and luminal contents of the fore-, mid-, and hind-midgut of Musca domestica larvae. Dipeptidase activity was found mainly in hind-midgut cells, whereas carboxy-peptidase activity was recovered in major amounts in both cells and in luminal contents of hind-midguts. The subcellular distribution of dipeptidase and part of the carboxypeptidase A activities is similar to that of a plasma membrane enzyme marker (aminopeptidase), suggesting that these activities are bound to the microvillar membranes. Soluble carboxypeptidase A seems to occur both bound to secretory vesicles and trapped in the cell glycocalyx. Based on density-gradient ultracentrifugation and thermal inactivation, there seems to be only one molecular species of each of the following enzymes (soluble in water or solubilized in Triton X-100): membrane-bound dipeptidase (pH optimum 8.0; Km 3.7 mM GlyLeu, M_r 111,000), soluble carboxypeptidase (pH optimum 8.0; Km 1.22 mM N-carbobenzoxy-glycyl-L-phenylalanine (ZGlyPhe), M_r45,000) and membrane-bound carboxypeptidase (pH optimum 7.5, Km 2.3 mM ZGlyPhe, M_r58,000). The results suggest that protein digestion is accomplished sequentially by luminal trypsin and luminal carboxypeptidase, by membrane-bound carboxypeptidase and aminopeptidase, and finally by membrane-bound dipeptidase.     

Approximate digestibility of fibre for a graminivorous caterpillar

Final instar Persectania ewingii (Westwood) (Lepidoptera: Noctuidae) were fed seedling Triticum aestivum L. for 2 days to determine the approximate digestibility of the cell wall and cell content fractions. Cell wall content was estimated using a micro-analytical neutral detergent fibre technique. Approximate digestibilites of neutral detergent fibre, neutral detergent solubles and dry matter were calculated for individuals and pooled samples. P. ewingii larvae digested a small but significant proportion of the fibre ingested (13–21%), higher than that previously reported for herbivorous insects. The micro-analytical and previously used macro-analytical techniques produced similar estimates of digestibility although both techniques have inherent shortcomings, the latter requiring the pooling of samplex and the former limiting the number of replicates during chemical analysis. Differences in the amount of larval frass collected during the feeding trial (corrected for consumption) explained much of the variation in digestibility values, while there were no effects of larval mass, overall consumption and total frass produced on digestibility estimates. These results confirm that plant cell contents are the major source of nutrients to larval Lepidoptera although there is some chemical disruption of the plant cell wall.     

Changes in intracellular pH and inorganic phosphate concentration during and after muscle contraction as studied by time-resolved 31P-NMR. Alkalinization by contraction

The morula and the mesenchyme blastula nuclei contained approx. 30 nuclear proteins which were preferentially released by limited digestion with DNase I, but no proteins were released from sperm nuclei. While most of the proteins released by DNase I digestion were common to the two embryonic stages, 2 and 6 proteins were specific or enriched in morulae and mesenchyme blastulae, respectively.     

On the evolution of arterial vascular patterns of tetrapods

The factors that explain the diverse arrangement of the major arteries of tetrapods are not known. Here, I aim to illuminate some of the underpinnings of these patterns. I review the variation in the sauropsid left, right, and dorsal aortae regarding the origin of the gastrointestinal blood vessels and the relative diameters of left and right aortae where they join together to form the dorsal aorta. I focus on these features because the quality of blood that flows through these aortae can vary depending on the state of cardiac shunting and the size of the vessel can provide insight into the quantity of blood borne by the vessels. I then place the information in a phyletic, historical, and ecological context. The plesiomorphic pattern is for the gastrointestinal vessels to arise as segmental arteries from the dorsal aorta, which is formed from the confluence of left and right aortae with similar diameters. The pattern is well conserved with only two major variations. First, in several clades of reptiles (testudines, crocodilians, lizards of the genera Varanus and Hydrosaurus) a substantial portion of the gastrointestinal arteries arises from the left aorta, leaving the diameter of the left aorta smaller than the right at their confluence. I hypothesize that this vascular arrangement facilitates growth by allowing more alkaline blood to flow to the somatic (body wall) and appendicular circulations, which may promote bone deposition and inhibit resorption, whereas hypercapnic, acidic blood flows to the digestive viscera, which may provide CO₂ as a substrate for the synthesis of gastric acid, bicarbonate, fatty acids, glutamine, purine rings, as well as glucose from lactate. Second, in some snakes and lizards with snake‐like body forms, such as Amphisbaenidae, the diameters of left and right aortae are asymmetrical at their confluence with the left aorta exceeding the right, but in members of the amphibian order Gymnophiona the right generally exceeds the left. This condition is associated with asymmetrical development of the lungs. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Digestive activity and stomach temperature in farmed bluefin tuna Thunnus thynnus measured by acoustic tag

Eight farmed Atlantic bluefin tuna Thunnus thynnus were tagged with temperature and depth transmitters inserted in chub mackerels Scomber colias to characterize their digestive activity, feeding physiology and behaviour in captivity. Results obtained in the experiment can be used to optimize daily T. thynnus feeding strategy in farms, reducing the early regurgitation of food and thus the environmental effects of inappropriate feeding practices.