Effects of an extreme flash flood on the native fish assemblages across a Mediterranean catchment

Abstract  The effects of an extreme flash flood on the native fish assemblages across a Mediterranean catchment in Southwest Portugal were investigated. The fish community structure and habitat were surveyed at 10 sites pre- and post-flood. Overall species richness and rank abundances changed little after the flood, despite there being a consistent decline in the abundance of small cyprinids. Pre- and post-flood habitat correlates of abundance changed for at least some species, and variability in assemblage structure was associated with flood, depth and pH. These results indicate that extreme floods occurring early in the wet season may have little disruptive effects on the overall structure of native fish assemblages in Mediterranean streams, although may at least partially influence population dynamics for some species. Habitat quality and complexity are likely to play a role in mediating species responses to flooding.     

Pronuclear Embryo Yield in Canindé and Saanen Goats for DNA Microinjection

The objective of this study was to examine the effect of donor breed on pronuclear‐stage embryo yield to be used for DNA microinjection in a transgenesis goat program. Twelve Canindé and twelve Saanen goats were heat synchronized using a progestagen‐cloprostenol treatment. Forty‐eight hours before the sponge removal, superovulation was induced with a total administration of 4.4 mg/kg bodyweight NIH‐FSH‐P1, given twice daily in decreasing doses over 3 days. In addition, goats received 100 μg of GnRH and they were hand‐mated at 36 and 48 h after progestagen removal. Embryo recovery was performed by oviduct flushing at 72 h after sponge removal. Embryos were microinjected with a DNA construct and noticeable swelling of the nuclei was the criterion for successful microinjection. The total diameter, cytoplasm diameter, zona pellucida thickness and pronuclei diameter were measured for each microinjected embryo. A higher (p < 0.05) percentage of fertilized ova was observed in Canindé (89.9%) than Saanen (36.2%) goats. In addition, Canindé donors produced a higher percentage of pronuclear embryos when compared with Saanen: 72.5% vs 20.6% (p < 0.05), respectively. Successful microinjection was verified in 96.7% and 73.3% of times in Canindé and Saanen embryos, respectively (p < 0.05). Significant differences were observed for all morphometric parameters except for cytoplasm diameter. In conclusion, under our study experimental conditions, Canindé were more efficient than Saanen goats concerning the pronuclear embryo yield and manipulation. The use of Canindé goats in transgenesis programs could be increase the interest in their breeding and could be contribute to saving them from extinction.     

Cost benefit of hatchery-reared barramundi, Lates calcarifer (Bloch), in Queensland

Abstract. Recreational fishing for barramundi, Lates calcarifer (Bloch), is a major contributor to the economy of Queensland, generating an estimated $A 8 to $A 15 million per annum. The Queensland Department of Primary Industries is investigating the feasibility of enhancing barramundi populations with fish produced in fish hatcheries. Cost benefit analysis of the Department's stocking of baaamundi in Lake Tinaroo indicates that each dollar spent on the programme generates a potential $A 31 of economic benefit to the Queensland economy.     

IMAGING DIAGNOSIS—METASTATIC ADRENAL PHEOCHROMOCYTOMA IN A DOG

A 10‐year‐old Akita mix became acutely paraplegic. Upon magnetic resonance imaging, multiple, slightly T2‐hyperintense, T1‐isointense extradural masses, relative to spinal cord were found in the vertebral canal. The retroperitoneal masses had mixed T2‐signal intensity. The contrast enhancement pattern for the spinal masses was both homogenous and heterogenous. The diagnosis was metastatic pheochromocytoma. Signal intensity of the tumors in this dog was similar to reports of pheochromocytoma in human beings.     

SPECIFIC ADSORPTION OF SILICATE AND PHOSPHATE BY SOILS

The adsorption of silicate and phosphate from pure and mixed solutions by four soils known to fix phosphate strongly has been measured. The adsorption at constant pH for each acid from its pure solution follows the Langmuir isotherm. The maximum adsorption of silicate by three of the soils from the pure solution occurs at pH 9.2, and the maximum adsorption curve for phosphate by two of the soils from its pure solution has a break in its slope at pH 6.4 and 11.6. These pHs are all just below the pK values for the dissociation of hydrogen ions from the undissociated silicic acid or the acid phosphate anions. The presence of silicate in a mixed solution, which is sufficiently concentrated in both silicate and phosphate to give maximum adsorption of either if in pure solution, does not affect the amount of phosphate adsorbed until the pH is over 6.5–7.0. At this pH the maximum adsorption curve for silicate crosses that for phosphate. The presence of phosphate in the mixed solution always depresses the adsorption of silicate. The maximum amount of silicate-plus-phosphate adsorbed from this mixed solution is either a little less than or equal to the amount of silicate adsorbed from the pure silicate solution if the pH is above 7. When silicate displaces phosphate, or phosphate displaces silicate, more moles of the displacing acid are adsorbed than moles of the displaced acid released. These results for soils are similar to those of Hingston et al. for the adsorption of silicate and phosphate by goethite.     

The extraction and characterization of soil polysaccharide by whole soil methylation

A soil of the Countesswells series was repeatedly methylated by the Hakomori procedure and a chloroform-soluble product isolated after each methylation. Ninety-two per cent of the material engendered by seven methylations was released during the first four methylations. This had a methoxyl content of about 20% and contained 2% N. Later fractions had lower methoxyl and N contents. Residual carbohydrate in the soil had reducing sugar content on hydrolysis, equivalent to about 3% of the original value. The extracted material had the infrared spectrum of a methylated soil polysaccharide and, on hydrolysis by 2 m trifluoracetic acid, released methylated sugar derivatives of which 68 were characterised by GC-MS. Derivatives corresponding to (1→4) linked sugars predominated for both hexose and pentose sugars but there was also a large proportion of (1→3) linkages, (1→3) linkages predominated for the deoxyhexose sugars. There were more sugars with only one or two methylated hydroxyl groups than could be accounted for as branching points because of the relatively small numbers of end groups. Prior reduction of the soil with sodium borohydride had no measurable effect on the nature or yield of the methylated product. This indicates that amino acid sugar linkages susceptible to β-elimination reactions can have only a very small influence on the reaction. The isolated sugar derivatives accounted for 70% of the total soil sugars. The methylated material before hydrolysis had a low nominal molecular weight on diafiltration, with 68% < 10000. Some of the sugars unaccounted for were probably lost during the dialysis stage necessary to remove dimethyl sulphoxide.     

One-trial interhemispheric transfer of a learning engram

By using spreading depression to decorticate temporarily one hemisphere in rats, a learning trace was established in the opposite functional hemisphere. Spontaneous transfer of the engram from the trained hemisphere to the untrained hemisphere does not occur when both hemispheres are functional. If, however, the animal was allowed to make one reinforced response, complete transfer of the engram to the untrained hemisphere occurred.