Biometry and size distribution of Chrysaora hysoscella (Cnidaria, Scyphozoa) and Aequorea aequorea (Cnidaria, Hydrozoa) off Namibia with some notes on their parasite Hyperia medusarum

Novel data on the biometry, size distribution and parasitesof Aequorea aequorea and Chrysaora hysoscella are provided frominvestigations conducted during summer and winter in the northernBenguela ecosystem. The relationship between mass and diameterof C. hysoscella did not change on a seasonal basis, and thispossibly reflects the aseasonal nature of the food environment.The changes in the size structure of C. hysoscella across theshelf and with depth agree with postulated population maintenancestrategies in the region. Aequorea aequorea was not stronglyparasitized, butC. hysoscella was subject to occasional parasitismby Hyperia medusarum, especially in winter when C. hysoscellais thought to reproduce. Parasites were distributed in a typical,negative-binomial manner on their hosts, but load was independentof host size. As medusae increased in diameter so H. medusarumtended to move from other tissues to the gonads.     

Induction and regulation of juvenile hormone esterases during the last larval instar of the cabbage looper, Trichoplusia ni

Juvenile hormone esterase titres were monitored in gate I and gate II last instar larvae of Trichoplusia ni using JH III as substrate. Two peaks of activity were observed for both gate I and gate II larvae, although the first and second juvenile hormone esterase peaks for the gate II larvae are extended and delayed one day, respectively. Head or thoracic ligations before the prepupal stage lower or block the appearance of both esterase peaks. Juvenile hormone I and II, as well as homo and dihomo juvenoids can induce the second juvenile hormone esterase peak in both normal and ligated larvae, and increase the esterase titre during the first peak in nonligated larvae. Induction of the juvenile hormone esterases is possible in non-ligated larvae as soon as the moult to the last instar has occurred and in ligated larvae as soon as the first esterase peak has started to decline. Distinct mechanisms of regulation are present for the first and second juvenile hormone esterase peaks. Juvenile hormone does not appear to be involved in regulating its own metabolism by directly inducing the first esterase peak; however, evidence is consistent with a brief burst of juvenile hormone which occurs prior to pupation inducing the production of the second peak of juvenile hormone esterase activity.     

Seston quality controls zebra mussel (Dreissena polymorpha ) energetics in turbid rivers

Feeding processes and energetic balance of zebra mussels were both related to the quantity and quality of natural seston. Filtration rate and pseudofeces production increased while clearance rate remained constant with increasing seston concentration. Ingestion rate, assimilation efficiency, and assimilation rate all increased with increasing food quality, measured as the ratio of organic to inorganic material in the seston. Respiration rate did not change with either food quantity or quality. As a result, scope for growth declined with decreasing food quality, and fell below 0 cal mg⁻¹ h⁻¹ at an organic:inorganic ratio of 0.5. The association between feeding processes and food quality appears related to a breakdown in the ability of zebra mussels to selectively ingest high-quality organic particles when the organic content of the seston is low. Ingestion, assimilation efficiency, assimilation rate and scope for growth were all higher when seston was amended with an addition of a natural assemblage of algae. Food quality may be a better indicator of environmental conditions suitable for growth than food quantity. These results suggest that the conditions of high suspended inorganic sediment concentrations in large turbid rivers represent a difficult growth environment for the zebra mussel. Received: 12 May 1997 / Accepted: 7 July 1998     

Monitoring zinc concentrations in water using the respiratory response of bluegills (Lepomis macrochirus Rafinesque)

Summary Measuring the cough frequency of bluegills by means of a cannula inserted through the snout into the buccal cavity is a good monitoring technique for zinc (and probably other heavy metals) because the response is quick, is proportional to the toxicant concentration and occurs at sublethal concentrations.     

An analysis of polygenes affecting wing shape on chromosome 3 in Drosophila melanogaster.

Loci on the third chromosome of Drosophila melanogaster that affect an index of wing shape were mapped, using recombinant isogenic lines, with transposable elements as markers. Many genes with small subequal effects are dispersed along the whole chromosome. Their alleles act nearly additively in heterozygotes. They have small correlated effects on leg shape, but no detectable effects on halteres. Small negative net interactions occur over most of the chromosome. The data set of 519 recombinant isogenic lines can be explained reasonably well by two models. One model posits an indefinitely large number of loci with no interactions. The other model posits 11 loci with additive effects whose sum equals the total phenotypic range and with large positive and negative interactions that nearly cancel each other.     

Organophosphorus pesticide‐induced butyrylcholinesterase inhibition and potentiation of succinylcholine toxicity in mice

Succinylcholine is the most important rapid‐acting depolarizing muscle relaxant during anesthesia. Its desirable short duration of action is controlled by butyrylcholinesterase, the detoxifying enzyme. There are two reported cases of prolonged paralysis from succinylcholine in patients poisoned with the organophosphorus insecticides parathion and chlorpyrifos. The present study examines the possibility that other organophosphorus and methylcarbamate pesticides might also prolong succinylcholine action by inhibiting butyrylcholinesterase using mice treated intraperitoneally as a model and relating inhibition of blood serum hydrolysis of butyrylthiocholine to potentiated toxicity (mouse mortality). The organophosphorus plant defoliant tribufos (4 h pretreatment, 160 mg/kg) and organophosphorus plant growth regulator ethephon (1 h pretreatment, 200 mg/kg) potentiate the toxicity of succinylcholine by seven‐ and fourfold, respectively. Some other pesticides or analogs are more potent sensitizers for succinylcholine toxicity with threshold levels of 0.5, 1.0, 1.7, 8, 10, and 67 mg/kg for phenyl saligenin cyclic phosphonate, profenofos, methamidophos, tribufos, chlorpyrifos, and ethephon, respectively. Enhanced mortality from succinylcholine is generally observed when serum butyrylcholinesterase is inhibited 55–94%. Mivacurium, a related nondepolarizing muscle relaxant also detoxified by butyrylcholinesterase, is likewise potentiated by at least threefold on 4 hour pretreatment with tribufos (25 mg/kg) or profenofos (10 mg/kg). © 1998 John Wiley & Sons, Inc. J Biochem Toxicol 13: 113–118, 1999