Muscular Stomach Research Articles

Determination of trichothecenes A (T-2 toxin, HT-2 toxin, and diacetoxyscirpenol) in the tissues of broilers using liquid chromatography coupled to tandem mass spectrometry

A stable and sensitive method has been developed for use in food and livestock product safety for the detection of mycotoxins. This newly developed method allows for the determination of T-2 toxin, HT-2 toxin and diacetoxyscirpenol (DAS) in heart, liver, spleen, lung, kidney, Glandular stomach, muscular stomach, small intestine, muscle, bone and brain samples from broilers using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The samples were initially extracted with ethyl acetate before being filtered through a 0.22μm nylon syringe filter and subjected to chromatographic separation on a reversed-phase C18 (50×2.1mm, 3μm) column. A mobile phase composed of 0.1% acetic acid and 10mM ammonium acetate in methanol and water was used in an assay of the levels of T-2 toxin, HT-2 toxin and DAS. For the analysis of the target compounds, the mass spectrometer was operated under positive electrospray ionization conditions in the selected reaction monitoring mode. The limit of detection was in the range of 0.02-0.05ng/g, whereas the limit of quantification was in the range of 0.08-0.15ng/g. The extraction recoveries of spiked samples from the high, intermediate and low levels ranged from 58.5% to 110.5%, and the relative standard deviation (RSD (%)) values were less than 17.0%. The results of inter- and intra-day precision (RSD (%)) were within 14.7%. The results revealed that the present method could be successfully applied to the analysis of T-2 toxin, HT-2 toxin and DAS in the real samples.

Digestive system anatomy of the Acipenser persicus: New features

Sturgeon is one of the most important species of the Caspian Sea aquatics. Unfortunately, this species faces the threat of extinction today. This makes specific studies on any type of sturgeons more important than before. Studies like histological studies, radiology, and sonography, all require a complete understanding of the anatomy of this fish. Since pilot studies showed some misconceptions in description of the sturgeon digestive system, this study was conducted to evaluate more precise anatomical structure of the digestive system of Acipenser persicus as the most important sturgeon species of Iran. A total of 40 adult Acipenser persicus were used in this experiment. They were autopsied primary to the study. All parts of the digestive system from buccal cavity toward rectum and anal orifice were evaluated. The anatomical structure and relations of the different parts of the digestive system including oral cavity, pharynx, esophagus, glandular stomach, muscular stomach, pyloric process, small intestine, spiral intestine, rectum, liver and pancreas were described. The digestive tube is relatively short. The stomach has two parts. The first part, or the proventricle, is U-shaped. The second part or gizzard has thick muscles and is almost surrounded with liver lobes. Pyloric caecum is located on the left side bottom of the gizzard as a sponge like structure. The intestines are made of 3 parts: the small intestine, the spiral colon, and the rectum. The small intestine has two flexures that separate it to three parts named the descending, ascending, and the end part, respectively. The spiral colon is the longest part of the digestive tube. This part has mucosal spiral septum on the inner surface. The rectum is short and located in the middle of the abdominal cavity. However, in the present study the opening was shown to be located in the muscular stomach and the intestine junction, just close to the gall bladder duct opening.

Identification and expression profiling analysis of goose melanoma differentiation associated gene 5 (MDA5) gene

Melanoma differentiation associated gene 5 (MDA5) is an important cytoplasmic receptor that recognizes long molecules of viral double-stranded RNA and single-stranded RNA with 5' triphosphate and mediates type I interferon secretion. In this study, the full-length MDA5 gene in the goose was identified and characterized. The cDNA of goose MDA5 was 3,306 bp in length with an open reading frame of 3,018 bp, which encoded a polypeptide of 1,005 amino acids. The deduced amino acid sequence contained 6 main structure domains including 2 caspase activation and recruitment domains, one DExD/H-box helicase domain, one type III restriction enzyme domain, one helicase conserved C-terminal domain, and one RIG-I C-terminal domain. Quantitative real-time PCR analysis indicated that goose MDA5 mRNA was constitutively expressed in all sampled tissues. It was highly expressed in the jejunum, trachea, ileum, colon, and kidney, and lowly expressed in the muscular stomach, glandular stomach, and muscle. A significant increase in the transcription of MDA5 was detected in the brain, spleen, and lungs of geese after infection with H5N1 highly pathogenic avian influenza virus compared with uninfected tissues. These findings indicated that goose MDA5 was an important receptor, involved in the antiviral innate immune defense to H5N1 highly pathogenic avian influenza virus in geese.

Effects of different levels of protein-to-energy ratios on nutrient digestibility and digestive enzyme activity in Leiothrix luteal

Effects of different levels of protein-to-energy ratios (PER) on nutrient utilization, digestive organs index and digestive enzymes activities in Leiothrix luteal were investigated in this research. It was found that different PER feedstuff had no significant effects on the utilization of dry matter (DM), calcium (Ca) and total phosphorus (TP). With the improvement of the PER, average daily feed intake ( ADFI ) gradually increased, the apparent utilization rate of energy and fat gradually improved, while the apparent utilization rate of crude protein increased at first and then decreased. Development of digestive organs of L. luteal was affected by the level of dietary PER, with the increase in PER, the digestive organ indices of muscular stomach, duodenum, jejunoileum and rectum exhibited a downward trend, the main influencing factors were the level of metabolizable energy in diets. With the intestinal tract moving backward, the relative activity of proteases gradually reduced, manifesting as pancreas > duodenum > jejunoileum. The relative activity of carbohydrate digestion enzymes gradually increased as the intestinal tract moved backward. With the improvement of PER, the relative activity of lipase gradually decreased in pancreas, duodenum, and jejunoileum. L. luteal possessed a strong ability to digest crude fiber and total phosphorus; the reason might be closely related to the types and quantities of intestinal flora, which was affected by the feeding habits of this bird. By comprehensively considering the nutrient utilization, digestive organ indices and digestive enzymes activities, the formula of PER II was more appropriate for nutritional needs of L. luteal in captivity. Keywords : Leiothrix luteal , protein-to-energy ratios, nutrients, digestion and utilization, enzyme activities African Journal of Biotechnology Vol. 12(15), pp. 1902-1908

Parasitic helminthes — probable cause of death of birds

Abstract Parasitic helminths were the probable cause of death of 41 passeriform birds (29 adults and 12 juveniles in their first year of life) caught in the net during the spring and autumn ringing (1986–2010). The birds (1 Chaffinch Fringilla coelebs, 1 House Martin Delichon urbica, 2 Blue Tit Cyanistes caeruleus, 9 Great Tit Parus major, 3 Willow Tit Poecile palustris, 1 Great Reed Acrocephalus arundinaceus, 1 Chiffchaff Phylloscopus collybita, 3 Blackcap Sylvia atricapilla, 2 Dunnock Prunella modularis, 1 Magpie Pica pica, 5 Robin Erithacus rubecula, 9 Common Blackbird Turdus merula and 3 Song Thrush T. philomelos) were caught in the environs of Přerov (Czech Republic). The helminths: trematodes, tapeworms, nematodes and hook worms, were located in the intestine, glandular and muscular stomach, cloaca, rectum, gall bladder, liver, pulmonary cavity, air sac, nasal and orbital cavity and subcutaneous tissue of the hosts. The intensity of invasion with different species of parasites was up to 734 per host. Some parasites Brachydistomum ventricosum, Mosesia sittae, Aprocta cylindrica, Diplotriaena tridens were acquired at the wintering grounds. All the helmniths were heteroxenous, with development cycle involving intermediate hosts (invertebrates) which are part of the birds’ diet.

Gross and histological studies of digestive tract of broilers during postnatal growth and development

We studied anatomy and histology of different segments of the digestive tract in postnatal growing broiler chickens with regard to their location, shape, size and weight. A group of four chickens, each at day 1 (D1), days 14 (D14) and days 28 (D28), total 12, were killed, their digestive tracts were dissected and described and shape, size and weight of different segments were recorded. Samples from different segments were prepared and stained with haematoxylin and eosin staining technique to study the histology under light microscope. The average lengths (cm) and weights (gm) of esophagus, proventriculus (glandular stomach), gizzard (muscular stomach), small intestine and large intestine were significantly higher (P<0.01) in chickens at D28 than that at D14 and at D1. The histological layers of digestive tract were lamina epithelia, lamina propria, lamina muscularis, submucosa, tunica muscularis and serosa with the exception in esophagus where outer adventitia was found. The esophageal glands were significantly more in numbers at D1 (in cross section, 12 in number per focus under 100x) than at D14 (6 in number per focus under 100x) and at D28 (2 in number per focus under 100x). The proventriculus consisted of macroscopic papillae with numerous microscopic folds with lamina propria comprised of simple glands, which converged into a common cavity near the surface. In gizzard, the cuticle, in the form of wavy lines ran parallel to the surface. The villi of small intestine and large intestine were lined by simple columnar epithelium. The apical parts of villi of the duodenum were slightly pointed and the basal parts of the villi were thicker than jejunum and ileum, whereas, the villi of the jejunum and ileum became shorter and broader than duodenum and most of the villi had blunt apical part and the basal parts were wider. The numbers of goblet cells were numerous in number in ileum than duodenum and jejunum. Plicae ran along the inner surface of the distal two thirds of the cacea. However, in the colorectum, the villi appeared as numerous long flat leaf-shaped structures which filled a large proportion of the lumen. The average lengths and widths of villi of small and large intestine were significantly higher (P<0.01) in chickens at D28 than that at D14 and at D1. The number of goblet cells in lamina epithelium and intestinal glands of the lamina propria were numerous in number at D28 than the chickens at D14 and at D1. DOI: http://dx.doi.org/10.3329/jbau.v10i1.12096 J. Bangladesh Agril. Univ. 10(1): 69–77, 2012

Identification and characterization of genes related to the development of breast muscles in Pekin duck

Pekin Duck is world-famous for its fast growth, but its breast muscle development is later and breast muscle content is lower compared with other muscular ducks. Therefore, it is very important to discover the genetic mechanism between breast muscle development and relative gene expression in Pekin duck. In current study, the genes which have relationships with breast muscle development were identified by suppression subtractive hybridization. A total of 403 positive clones were sequenced and 257 unigenes were obtained. The expression of 23 genes were analyzed in the breast muscle of 2-, 4-, 6-, 8- week old Pekin ducks. The results showed that unknown clone A233, C83 and C99 showed descending tendency as age increased; KBTBD10, HSPA8, MYL1, ZFP622, MARCH4, Nexilin, FABP4 and MUSTN1 had high expression levels at 6 weeks old; WAC, NT5C3, HSP90AA1, MRPL33, KLF6, TSNAX, CDC42EP3, HSPA4, TRAK1, NR2F2, HAUS1 and IGF1 had high expression levels at 8 weeks and showed ascending tendency as age increased. Expression of these 23 genes were also analyzed in breast muscle, leg muscle, heart, kidney, liver, muscular stomach and sebum cutaneum in 4-8-week old Pekin duck and results showed that most of these genes had high expression in breast muscle, leg muscle and heart.

A history of mental health problems may predict maternal distress in women postpartum

Aimto elucidate the effects of prior mental disorders on newly delivered women's mental health and to compare the outcome of different instruments to screen for maternal distress and depression after childbirth. The sample of 232 Stockholm women responded to a questionnaire on background data and three questionnaires, Beck Depression Inventory (BDI), Edinburgh Postnatal Depression Scale (EPDS) and Postpartum Depression Symptoms Rating Scale (PPDS) at 4–6 weeks and 10–12 weeks after childbirth. Resultsshow that maternal distress was experienced by 20% of the women as assessed by the BDI and the EPDS at 4–6 weeks postpartum, and by 13–16% of the women at 10–12 weeks after childbirth. A regression analysis showed that a history of mental health problems influenced maternal self-assessment at both points-in-time. The following background data showed a small but significant impact on maternal self-assessment; younger age, lower educational level, and a short-term partner relationship. The most important emotional responses were sadness, guilt and self-blame across all three instruments at both points in time. Loss of pleasure, self-accusations, irritability, anger, worry and somatic symptoms such as muscular tension, headaches and stomach cramps also occurred. Conclusionwomen with prior mental health problems are more vulnerable for maternal distress and midwives at the antenatal health clinics should encourage pregnant women to express emotional issues during their transition to motherhood in order to offer appropriate professional support and care.

Evolution of Trefoil Factor(s): Genetic and Spatio-Temporal Expression of Trefoil Factor 2 in the Chicken (Gallus Gallus Domesticus)

Trefoil factors are essential healing initiators participating in mucosal reconstitution and tissue morphogenesis, especially on the surfaces of the gastrointestinal tract. This family has been cloned and characterized predominantly from mammals and amphibians. Avian species ingest stone and grit to help digest food, which may expose their gut to severe physical conditions. To further the understanding of the function of the TFF gene family across species, we undertook this research to clone, sequence, and characterize the spatio-temporal expression patterns of chicken TFF2 (ChTFF2) cDNA. Bioinformatics analysis of the promoter region and deduced amino acid sequence demonstrated that ChTFF2 contained unique characteristics; specifically the chicken promoter has multiple start sites and the protein contains a series of Lys-Lys-Val repeats. Unlike mammals, where TFF2 is detected primarily in the stomach, and occasionally in the proximal duodenum, chicken TFF2 transcripts are found throughout the gastrointestinal tract, with major expression sites in the glandular and muscular stomach as well as evident expression in the colon, small intestine, cecal tonsil and crop. Temporal analysis of intestinal ChTFF2 transcripts by quantitative RT-PCR showed high levels in embryos and a trend of constant expression during embryonic and post-hatch development, with a reduction occurring around hatch. Phylogenetic analysis highlighted the conservation of TFF proteins and functional divergence of trefoil domains, which suggest a transitional role in the bird during evolution.

Effect of parasites on the of digestive system in Iraqi bulbul Pycnonotus lecuotis mesoptamiae

This study included collecting of 150 specimens of the Iraqi Bird Bulbule Pycnonotus lecuotis mesoptamiae (Pycnotidae , Passeriformes), from the 1st of November 2004 to 30th of October 2005 in the city of Baghdad and its suburbs, in concern of identifying the internal parasite of the digestive tract of these birds and studying the diseases resulted from the infection. The study showed that the bird Bulbule is Parasitized by Four types of Cestodes ,two of them are recorded in this kind of bird in Iraq for the first time ,Paradicranotinae anormalis and Haploparaxis sp. , and the other two are Raillietina tetragona and Allohymenolepsis sp. ,and by two types of Pin Worm(Trematode) that are identified for the first time in the Bird Bulbul , Mosesia Chordilesia and Plagiorchis sp. , Gross study showed that the oral cavity ,pharynx and esophagus had no pathological changes in all infected birds .The muscular stomach looked pale ,nearly brown and corroded ,while the mucosa had rottenness and decay in its grooves .The intestinal walls of the infected birds showed spherical ,small size, solid and rough knots and haemorrhgic bruises. some infected birds developed pale and large in size liver . Histological study showed no pathological changes in the oral cavity, pharynx and esophagus of the infected birds. Chronic inflammations and rottenness has been detected in the glandular stomach and the musculae stomach.The villi of the small intestine of the infected birds appeared to have abnormal shapes, cracked and with lost details compared to the control, beside the hypertrophy of the enteric glandular layer. The caecae and the large intestine were healthy for all the examined birds. The study showed also the presence of common lesions in the same organ and other organs of the digestive tract of the same birds, chronic intestinal inflammation, villi atrophy and hypertrophy accompanied the muscular stomach, the liver and pancreatic inflammation for the same bird with the rate of (10.66%).

Effect of parasites on the of digestive system in Iraqi bulbul Pycnonotus lecuotis mesoptamiae

This study included collecting of 150 specimens of the Iraqi Bird Bulbule Pycnonotus lecuotis mesoptamiae (Pycnotidae , Passeriformes), from the 1st of November 2004 to 30th of October 2005 in the city of Baghdad and its suburbs, in concern of identifying the internal parasite of the digestive tract of these birds and studying the diseases resulted from the infection. The study showed that the bird Bulbule is Parasitized by Four types of Cestodes ,two of them are recorded in this kind of bird in Iraq for the first time ,Paradicranotinae anormalis and Haploparaxis sp. , and the other two are Raillietina tetragona and Allohymenolepsis sp. ,and by two types of Pin Worm(Trematode) that are identified for the first time in the Bird Bulbul , Mosesia Chordilesia and Plagiorchis sp. , Gross study showed that the oral cavity ,pharynx and esophagus had no pathological changes in all infected birds .The muscular stomach looked pale ,nearly brown and corroded ,while the mucosa had rottenness and decay in its grooves .The intestinal walls of the infected birds showed spherical ,small size, solid and rough knots and haemorrhgic bruises. some infected birds developed pale and large in size liver . Histological study showed no pathological changes in the oral cavity, pharynx and esophagus of the infected birds. Chronic inflammations and rottenness has been detected in the glandular stomach and the musculae stomach.The villi of the small intestine of the infected birds appeared to have abnormal shapes, cracked and with lost details compared to the control, beside the hypertrophy of the enteric glandular layer. The caecae and the large intestine were healthy for all the examined birds. The study showed also the presence of common lesions in the same organ and other organs of the digestive tract of the same birds, chronic intestinal inflammation, villi atrophy and hypertrophy accompanied the muscular stomach, the liver and pancreatic inflammation for the same bird with the rate of (10.66%).

Identification and characterization of a novel antibacterial peptide, avian β-defensin 2 from ducks

In this study, a novel avian beta-defensin (AvBD) was isolated from duck pancreas. The complete nucleotide sequence of the gene contained an 195 bp open reading frame encoding 64 amino acids. Homology, characterization and comparison of the gene with AvBD from other avian species confirmed that it was duck AvBD2. The mRNA expression of the gene was analyzed in 17 tissues from 21-day-old ducks. AvBD2 was highly expressed in the trachea, crop, heart, bone marrow, and pancreas; moderately expressed in the muscular stomach, small intestine, kidney, spleen, thymus, and bursa of Fabricius; and weakly expressed in skin. We produced and purified recombinant AvBD2 by expressing the gene in Escherichia coli. As expected, the recombinant peptide exhibited strong bactericidal properties against Bacillus cereus, Staphylococcus aureus, and Pasteurella multocida, and weak bactericidal properties against E. coli and Salmonella choleraesuis. In addition, the recombinant protein retained antimicrobial activity against S. aureus under different temperatures (range, -20 degrees C to 100 degrees C) and pH values (range, 3 to 12).

Histopathological evaluation in experimental envenomation of dogs with Crotalus durissus terrificus venom

The present work evaluated histopathological aspects in experimental envenomation of dogs with Crotalus durissus terrificus venom. Twenty-eight mixed breed adult dogs were divided into three groups of seven animals each: Group I - only venom; Group II - venom + 50ml antiophidic serum + fluid therapy; Group III - venom + 50ml antiophidic serum + fluid therapy + urine alkalization. Lyophilized venom of Crotalus durissus terrificus was reconstituted in saline solution and inoculated subcutaneously at the dose of 1mg/kg body weight. Three animals of each group were subjected to euthanasia, and their muscular tissue, brain, spleen, kidneys, heart, lungs, stomach, small and large intestines, and popliteal lymph node fragments were collected for histopathological evaluation. There was myonecrosis in the inoculated limb, renal tubular degeneration, lymphoid hyperplasia of spleen, and unspecific reactive hepatitis. These results show the antigenicity and action of the venom on the immune system.

Expression patterns of the chicken peroxisome proliferator-activated receptors (PPARs) during the development of the digestive organs

Peroxisome proliferator-activated receptors (PPARs) play very important roles in various biological phenomena such as regulation of lipid metabolism, homeostasis, cell differentiation and proliferation, in a variety of organs and tissues. However, their functions in the development of the digestive organs have not been studied yet, although it has been supposed that they are involved in the tumor development and regression of digestive organs. To provide fundamental data to analyze functions of PPARs in the developing digestive organs in the chicken embryos, we performed thorough analysis of expression of PPARα, β (δ) and γ in the esophagus, proventriculus (glandular stomach), gizzard (muscular stomach), small and large intestines from early developmental stages to post hatch stages. The results showed that each PPAR is expressed in spatio-temporally regulated manner. In general, PPARβ is widely expressed among digestive organs whereas PPARα and γ showed restricted expression. In the intestine, all PPARs are expressed after hatch, indicating that they play important roles in the physiology of the adult intestine.

Morphology of glandular stomach (Ventriculus glandularis) and muscular stomach (Ventriculus muscularis) of the partrigde Rhynchotus rufescens

Twenty adult partridges Rhynchotus rufescens were used for morphologic and histological study. The materials destined to the morphologic study were collected and the lengths of the glandular stomach and of the muscular stomach were measured. For the histological study, fragments of the glandular stomach (gastric proventriculus, Ventriculus glandularis) and of the muscular stomach (gastric ventriculus, Ventriculus muscularis) were stained routinely with periodic acid-Schiff (PAS) and Masson’s trichrome stain. Glandular stomach is prolonged, with a fusiform format toward craniocaudalis and for the left. It presents a mean length of 3.20cm in the females and 3.65cm in the males. Gastric proventriculus is composed by several lobes and glands. The mucosa is formed by a simple cubic epithelium, which is much folded. Muscular stomach has the format of a biconvex lens, with 4.30cm and 4.35cm of mean length for the females and male, respectively. The mucosa is formed by folds lined by columnar cells and the mucus that forms the cuticula. There are crypts in the base of the folds. Closely, there is a lamina propria and a thick smooth muscle layer, which is placed according to the format of the organ. A dense portion of connective tissue constitutes the serosa, mixed by some smooth muscle cells.

Curculionids in the diet of the white-quilled korhaan: more than just food?

Analyses of 326 white-quilled korhaan (Eupodotis afraoides) stomach contents collected in the Free State and Northern Cape over a period of 20 years (1984-2004) showed this species to be a mixed feeder concentrating mainly on insects. Based on dry mass prey items of the Isoptera and Coleoptera form the bulk of the diet. According to frequency of occurrence coleopterans, more specifically members of the family Curculionidae, are utilised most often. Indications are that the curculionids, owing to their size and relative hardness of the exoskeleton, fulfil an accessory function with regard to the physical breakdown of coarse food items in the muscular stomach.

Traditional phytotherapy of the Albanians of Lepushe, Northern Albanian Alps

An ethnobotanical and ethnopharmacognostic survey has been carried out in one of the most isolated mountainous area in Europe: the village of Lepushe and its surrounding territory, in the Northern Albanian Alps. Approximately 70 botanical taxa and 160 preparations, mainly derived from plants, but also derived from animal products or minerals, have been recorded. The archaic belief of the signature still plays a very important role in the present ethnomedicine of the Albanians of Lepushe. As a consequence, aerial parts of Chelidonium majus are used to treat jaundice; leaves of the fern Phyllitis scolopendrium are thought to be able to treat every respiratory and lung affection; the bulbs of Lilium martagon are used to treat liver diseases; jasper is rubbed into milk and given to sheep to drink and, the membrane of a hen's muscular stomach is used to treat human kidney stones. A current common ethnomedical use of P. scolopendrium and L. martagon is recorded for the first time in Europe.

Expression of Fgf10 and Fgf receptors during development of the embryonic chicken stomach

Fibroblast growth factor 10 (FGF10) is involved in numerous different aspects of embryonic development and especially in active epithelial–mesenchymal interactions during morphogenesis of many organs as a mesenchymal regulator by activating its receptors (FGFR1b and FGFR2b) expressed in the epithelial tissue. FGFR2b is also activated by FGF7 although FGF7 does not bind to FGFR1b. To provide basic data to analyze function of FGFs in the developing gut, here we cloned Fgf7 and studied expression patterns of Fgf7, Fgf10 and Fgfr1–4 during the development of chicken stomach (glandular stomach; proventriculus and muscular stomach; gizzard). Fgf10 is expressed both in the proventricular and gizzard mesenchyme while Fgf7 is expressed only in gizzard mesenchyme. Fgfr1–4 are expressed both in the epithelium and mesenchyme with a different spatial expression patterns. Furthermore, RT-PCR analysis reveals that Fgfr1b and Fgfr2b are expressed only in epithelia of both organs.

Adaptations of the aardvark for survival in the Karoo: a review

Aardvarks are found in a wide range of habitats in sub-Saharan Africa, from semi-arid zones in the Nama Karoo to high rainfall areas of tropical rainforests. They are not, therefore, specifically adapted to living in dry or wet conditions; rather, being committed nocturnal and fossorial, myrmecophages, they have evolved anatomical, physiological and behavioural adaptations that allow them to feed on ants and termites. These adaptations allow aardvarks to inhabit many areas as long as sufficient prey is available. Feeding adaptations include specialised snout anatomy and a very keen sense of smell to find prey underground; a strong body structure and digging apparatus to dig into subterranean nests or termitaries; a long vermiform tongue and large salivary glands to extract prey from inside their nests; and a muscular stomach to grind up the food. The low rainfall of the Nama Karoo does not present a problem for aardvarks because they meet all their water requirements through their diet, while the strong seasonal temperature variations that could place considerable stresses on aardvarks are avoided by the judicious use of burrows. Nocturnal activity patterns allow aardvarks to conduct digging activities under relatively cool conditions, thus avoiding hyperthermia due to body heat production during hot conditions, while the diurnal activity patterns of most prey species means that they are inactive when aardvarks are foraging and can, therefore, be acquired more efficiently.

Shifts in the diets of slimy sculpin (Cottus cognatus) and lake whitefish (Coregonus clupeaformis) in Lake Ontario following the collapse of the burrowing amphipod Diporeia

In Lake Ontario, the diets of slimy sculpin Cottus cognatus and lake whitefish Coregonus clupeaformis shifted from a diet dominated by the burrowing amphipod, Diporeia, and to a lesser extent, Mysis, to a more diverse diet, after Diporeia collapsed, to one dominated by Mysis and prey that were formerly less important or uncommon such as Chironomidae, Oligochaeta, and Ostracoda. Additionally, lake whitefish still preyed on native mollusks like Sphaeriidae and Gastropoda, but also preyed on exotic mollusks, Dreissena spp., which are swallowed intact and subsequently crushed in its muscular stomach. Whether Diporeia was abundant (1992) or scarce (1999), selection indices for Diporeia by slimy sculpins was positive, suggesting that Diporeia was a preferred prey. Unlike lake whitefish, slimy sculpins avoided Dreissena; therefore, energy diverted to Dreissena production was a real loss for slimy sculpins. The shifts in the diet of these benthic fishes corresponded with drastic changes in the benthic community between 1992 and 1999. The collapse of Diporeia, formerly the most abundant macroinvertebrate in the benthic community, along with sharp declines in the abundance of Oligochaeta and Sphaeriidae, coincided with the establishment and rapid expansion of Dreissena bugensis, the quagga mussel, and to a lesser degree Dreissena polymorpha, the zebra mussel. It appears that the Diporeia population first collapsed at depths >70 m in southeastern Lake Ontario by autumn 1992, at shallower depths in the eastern Lake Ontario by 1995, and along the entire south shore line at depths <100 m, and perhaps in some areas >100 m by 1999. In response to the disappearance of Diporeia, populations of two native benthivores, slimy sculpin and lake whitefish, collapsed in eastern Lake Ontario, perhaps due in part to starvation, because Diporeia was their principal prey. Presently, alternative food resources do not appear sufficient to sustain these two benthivores at their former levels of abundance. We do not expect slimy sculpin and lake whitefish to recover unless Diporeia returns to earlier levels of abundance.