Interspecific competition and rarity in mudsnails: feeding interactions between and within Hydrobia acuta neglecta and sympatric Hydrobia species

• 1. Using production of faecal pellets as a proxy for feeding rate, possible reciprocal effects of the widespread and abundant mudsnails Hydrobia ulvae and Hydrobia ventrosa on the rare Hydrobia acuta neglecta were investigated under the sea‐water salinity conditions in which all three species occur naturally in East Anglia, UK.
• 2. Over a density range equivalent to 1000–34 000 m^?2, H. acuta and H. ventrosa (though not H. ulvae) at some point displayed an intraspecific reduction in egestion with increase in density. For H. acuta, every 5000 extra snails above a threshold of 16 000 m^?2 reduced egestion by up to 8%; and for H. ventrosa, every 5000 extra snails above a threshold of 8000 m^?2 reduced egestion by an average 7%.
• 3. Keeping the density of one test species constant at 4000 m^?2 whilst varying that of a sympatric one from 0 up to 30 000 m^?2 indicates that H. ulvae has a marked effect on H. acuta at all densities, decreasing its egestion by 10% for every 5000 m^?2 H. ulvae also present, but that H. acuta has no such reciprocal effect on H. ulvae. H. ventrosa had no effect on egestion in H. acuta, although H. acuta did have some minor effect on H. ventrosa, on average decreasing its egestion by 3% for every 5000 m^?2 H. acuta present.
• 4. The intensity of intraspecific competition within H. acuta, therefore, exceeds that exerted on H. acuta by H. ventrosa, and likewise intraspecific effects within H. ventrosa generally outweigh any interspecific effect from H. acuta. The effect of H. ulvae on H. acuta, however, exceeds that intraspecifically within H. acuta.
• 5. These results are discussed in relation to the rarity of H. acuta neglecta.

Copyright © 2005 John Wiley & Sons, Ltd.     

Venereal colibacillosis (acute vaginitis) in turkey breeder hens

Two flocks of turkey breeders experienced an increased mortality and high culling rate in the first weeks of egg production. The majority of dead and culled hens had cheesy core in the cloaca and vagina. Postmortem examination revealed fibrinous pseudomembranes in the vagina and cloaca. The thickness of these membranes posed an obstruction to egg passage leading to internal laying and egg peritonitis. Swabs from cloaca and vagina produced numerous colonies of only E. coli. Investigations of this unusual vaginitis showed that these two flocks had a higher number of immature hens with present hymens, and insemination crews mistakenly inseminated all hens in which they were able to evert the cloaca. Breaking the hymen with an insemination pipette created a wound and developed extensive infection with E. coli bacteria.     

Enhancement of enteropathogenic Escherichia coli pathogenicity in young turkeys by concurrent turkey coronavirus infection

In a previous study, turkey coronavirus (TCV) and enteropathogenic Escherichia coli (EPEC) were shown to synergistically interact in young turkeys coinfected with these agents. In that study, inapparent or mild disease was observed in turkeys inoculated with only TCV or EPEC, whereas severe growth depression and high mortality were observed in dually inoculated turkeys. The purpose of the present study was to further evaluate the pathogenesis of combined TCV/EPEC infection in young turkeys and determine the role of these agents in the observed synergistic interaction. Experiments were conducted to determine 1) effect of EPEC dose, with and without concurrent TCV infection, and 2) effect of TCV exposure, before and after EPEC exposure, on development of clinical disease. Additionally, the effect of combined infection on TCV and EPEC shedding was determined. No clinical sign of disease and no attaching and effacing (AE) lesions characteristic of EPEC were observed in turkeys inoculated with only EPEC isolate R98/5, even when turkeys were inoculated with 10(10) colony forming units (CFU) EPEC (high dose exposure). Only mild growth depression was observed in turkeys inoculated with only TCV; however, turkeys inoculated with both TCV and 10(4) CFU EPEC (low dose exposure) developed severe disease characterized by high mortality, marked growth depression, and AE lesions. Inoculation of turkeys with TCV 7 days prior to EPEC inoculation produced more severe disease (numerically greater mortality, significantly lower survival probability [P < 0.05], increased frequency of AE lesions) than that observed in turkeys inoculated with EPEC prior to TCV or simultaneously inoculated with these agents. Coinfection of turkeys with TCV and EPEC resulted in significantly increased (P < 0.05) shedding of EPEC, but not TCV, in intestinal contents of turkeys. These findings indicate that TCV infection predisposes young turkeys to secondary EPEC infection and potentiates the expression of EPEC pathogenicity in young turkeys.     

The effect of storage temperature on the shelf‐life of eviscerated air‐chilled Turkeys

1. Eviscerated air‐chilled turkeys (weighing about 5.5 kg) were stored in groups of 10 at temperatures between 5 and — 2 °C. Slight “off” odour was detected in an average time of 7.2 d at 5 °C, 13.9 d at 2 °C, 22.6 d at 0 °G and about 38 d at ‐2 °C.

2. The microbiological condition of the carcasses was determined initially and after storage at — 2 ^oC for 28, 35 and 42 d. It was found that, whilst pseudomonads (pigmented and non‐pigmented) were present at 10⁸/cm² after 35 and 42‐d storage, yeasts were also present at 10⁷/cm² and probably accounted for the unusual fusty “off” odours.     

The relationship between brain levels of cismethrin and bioresmethrin in female rats and neurotoxic effects

The oral toxicity of 5-benzyl-3-furylmethyl-(1R, cis)-chrysanthemate (cismethrin) to female rats decreased as their environmental temperature was raised. Acute oral LD₅₀ values increased from 157 mg/kg at 4°C to 197 mg/kg at 20°C and to > 1000 mg/kg at 30°C. Cismethrin was much more toxic given intravenously when the LD₅₀ was 4.5 mg/kg. This value did not change at different environmental temperatures. Irrespective of the environmental temperature, or route of adminstration, following the respective LD₅₀'s cismethrin caused tremors in rats when brain levels of 0.5–1.0 μg/g were reached and, at death, brain concentrations were 3.9–5.1 μg/g. These results suggested that the accumulation of cismethrin by the brain could be used as a model for the nervous system as a whole. The isomeric 5-benzyl-3-furylmethyl-(1R, trans)-chrysanthemate (bioresmethrin) was about 50 times less toxic to rats than cismethrin. After an intravenous LD₅₀, tremors started when brain concentrations were 4–5 μg/g. At death, brain levels were 25–35 μg/g. Plasma esterases were about equally active in hydrolysing cismethrin and bioresmethrin, whereas liver microsomal esterases hydrolyzed bioresmethrin over 10 times more rapidly than cismethrin. It is suggested that the lower toxicity of bioresmethrin is not only due to its faster metabolism but to an intrinsically lower toxicity at the critical site of action in the nervous system.     

Oviductal Fluid Proteins Associated with the Bovine Zona Pellucida and the Effect on In Vitro Sperm–Egg Binding,Fertilization and Embryo Development

Studies have demonstrated that oviductal fluid (ODF) proteins associate with eggs of numerous species including the bovine. In this study, the association of three ODF proteins, the bovine oestrus‐associated protein, osteopontin (OPN), lipocalin‐type prostaglandin D synthase (L‐PGDS), with the bovine zona pellucida (ZP) was demonstrated by immunohistochemistry and western blot. The biological function of ODF derived egg‐associated OPN and L‐PGDS in sperm binding, fertilization and embryonic development was also explored. In vitro matured bovine oocytes were pre‐incubated with ODF collected by cannula from cows in oestrus, or ODF with antibodies to OPN, L‐PGDS and bovine serum albumin (BSA). Following incubation, oocytes were inseminated with 1 × 10⁵ frozen‐thawed spermatozoa, and they were evaluated for sperm binding, fertilization and embryonic development in vitro. Pre‐treatment of ODF with antibodies to all of proteins reduced sperm binding to the ZP and fertilization in vitro. Cleavage rates were not significantly different among incubations, but rates of embryo development were significantly decreased. We conclude that antibodies to OPN, L‐PGDS and BSA react with oocytes incubated with ODF and inhibit sperm binding, fertilization and embryonic development in vitro, suggesting a potential role of these proteins in these events.     

Noradrenergic Control of Arginine Vasopressin Release from the Ewe Hypothalamus In Vitro: Sensitivity to Oestradiol

The present study aims at ascertaining the influence of α₁‐adrenoreceptors on arginine vasopressin (AVP) release in vitro and determine whether E₂ modulates the α₁‐adrenoreceptor and AVP interaction. Ten minutes after ewe killing, sagittal midline hypothalamic slices (from the anterior preoptic area to the mediobasal hypothalamus with the median eminence, 2 mm thick, 2 per sheep) were dissected, placed in oxygenated minimum essential media‐α (MEM‐α) at 4°C and within 2 h were singly perifused at 37°C with oxygenated MEM‐α (pH 7.4; flow rate 0.15 ml/min), either with or without E₂ (24 pg/ml). After 4 h equilibration, 10 min fractions were collected for 4 h interposed with 10 min exposure at 60 min to a specific α₁‐adrenoreceptor agonist or antagonist at various doses (0.1–10 mm ). At the end of all perifusions, slices responded to KCl (100 mm ) with AVP efflux (p < 0.05). Release of AVP was enhanced (p < 0.05) by the α₁‐adrenoreceptor agonist (methoxamine 10 mm ; no E₂, n = 7 perifusion chambers: from 14.3 ± 2.7 to 20.9 ± 3.9, with E₂, n = 10: from 10.7 ± 1.2 to 18.4 ± 3.4 pg/ml) or the antagonist (thymoxamine 10 mm ; no E₂, n = 5: from 9.5 ± 3.1 to 30.4 ± 6.0, with E₂, n = 10: from 10.8 ± 0.9 to 39.1 ± 6.3 pg/ml). With the agonist, the response occurred only at 80 min (p < 0.05) both in the presence and absence of E₂. Whereas, after the antagonist, values were higher (p < 0.05) throughout the post‐treatment period (80–170 min) without E₂, but declined by 150 min in the presence of E₂. Furthermore, the response to the α₁‐adrenoreceptor antagonist was greater (p < 0.05; 90–140 min) than the agonist only in the presence of E₂. In conclusion, these results reveal direct α₁‐adrenoreceptor‐mediated control of the hypothalamic AVP neuronal system which is modulated by E₂.