Evaluation of a remotely operated vehicle (ROV) as a tool for studying the distribution and abundance of zooplankton

Conventional methods for measuring zooplankton distributionsare too laborious and time consuming to permit sufficient temporaland spatial resolution in many instances. An ability to makemore efficient and precise measurements would be useful. Weevaluated the potential for using the video system of a commerciallyavailable remotely operated vehicle (ROV) to measure the distributionand abundance of zooplankton by calibrating ROV counts withcounts based on a conventional sampling procedure (a Schindlertrap), and by using an ROV to measure the density of zooplanktonin a small lake. As configured here, this particular ROV wassuitable for measuring the density of the cladocerans Daphniaand Holopedium. It was also suitable for assessing the distribution,but not absolute densities, of Chaoborus and Leptodora. Imagequality was inadequate for quantitative estimates of copepod(Diaptomus minutus) abundance, and prevented us from studyingbehavioral responses of copepods to the vehicle. We concludethat the ROV has at least three useful features: it can be usedto locate patches of those species that are imaged effectively;a large number of samples (videotapes) can be collected almostsynoptically with high spatial resolution; the ROV enables insitu observation of zooplankton. The ROV also has three importantlimitations: the small image volume makes it difficult to studyrare organisms; inadequate image resolution precludes studiesof relatively small organisms (e.g. the calanoid copepod D.minutus);zooplankton respond to the presence of the ROV.     

The transposable element mariner can excise in non-drosophilid insects

Plasmid-based excision assays performed in embryos of two non-drosophilid species using the mariner transposable element from Drosophila mauritiana resulted in empty excision sites identical to those observed after the excision of mariner from D. mauritiana chromosomes. In the presence of the autonomous mariner element Mos1, excision products were recovered from D. melanogaster, D. mauritiana and the blowfly Lucilia cuprina. When a hsp82 heat shock promoter-Mos1 construct was used to supply mariner transposase, excision products were also recovered from the Queensland fruitfly Bactrocera tryoni. Analysis of DNA sequences at empty excision sites led us to hypothesise that the mariner excision/repair process involves the formation of a heteroduplex at the excision breakpoint. The success of these assays suggests that they will provide a valuable tool for assessing the ability of mariner and mariner-like elements to function in non-drosophilid insects and for investigating the basic mechanisms of mariner excision and repair.     

Mammalian-heart adenylate deaminase: Cross-species immunoanalysis of tissue distribution with a cardiac-directed antibody

A sheep antiserum against purified rabbit-heart adenylate deaminase (EC 3.5.4.6) (AMPD) was developed and validated as an immunologic probe to assess the cross-species tissue distribution of the mammalian cardiac AMPD isoform. The antiserum and the antibodies purified therefrom recognized both native and denatured rabbit-heart AMPD in immunoprecipitation and immunoblot experiments, respectively, and antibody binding did not affect native enzyme activity. The immunoprecipitation experiments further demonstrated a high antiserum titer. Immunoblot analysis of either crude rabbit-heart extracts or purified rabbit-heart AMPD revealed a major immunoreactive band with the molecular mass (81 kDa) of the soluble rabbit-heart AMPD subunit. AMPD in heart extracts from mammalian species other than rabbit (including human) was equally immunoreactive with this antiserum by quantitative immunoblot criteria. Although generally held to be in the same isoform class as heart AMPD, erythrocyte AMPD was not immunoreactive either within or across species. Nor was AMPD from most other tissues [e.g., white (gastrocnemius) muscle, lung, kidney] immunoreactive with the cardiac-directed antibody. Limited immunoreactivity was evidenced by mammalian liver, red (soleus) muscle, and brain extracts across species, indicating the presence of a minor cardiac(-like) AMPD isoform in these tissues. The results of this study characterize the tissue distribution of the cardiac AMPD isoform using a molecular approach with the first polyclonal antibodies prepared against homogeneous cardiac AMPD. This immunologic probe should prove useful at the tissue level for AMPD immunohistochemistry.     

Seasonal changes in the day and night activity of adult perch, Perca fluviatilis L.

Perca fluviatilis L. were caught by gill nets every 3 h over a 24 h period monthly from February 1975 until January 1976. The numbers caught increased with rise in temperature (correlation coefficient r = 0.86 P < 0.001). During the winter months perch migrated into deeper water although some fish were still caught in shallow water (1–6 m). Perch were active at very low light intensities. However changes in visual surface irradiance (400–700 nm) and water clarity caused inverse changes in activity. Only June did not conform to this pattern and it was presumed that spawning behaviour was of primary importance. It is suggested that increase in eutrophication with its effect on water clarity enables fish to become more active during the day in the summer months. They are thus able to utilise food sources to a maximum at an optimum period for feeding and growth.     

Steroid sulphatase levels in XX males,including observations on two affected cousins

Summary Quantitative assays of steroid sulphatase in XX males have shown that some individuals have two functional loci, and others only one. Two affected cousins, who cannot share the same X-chromosome, nevertheless have male levels of steroid sulphatase, suggesting functional abnormality of the X chromosome.The hypothesis is advanced that these and other unusual features of X-chromosome function in some XX males, could be explained if such cases were due to an autosomal mutation, exercising its effect by causing abnormal inactivation of a subterminal area of Xp which normally escapes the inactivation process.     

Transmembrane ferricyanide reduction in tobacco callus cells

Transmembrane ferricyanide reduction in whole cells of normal and of transformed tobacco (Nicotiana tabacum) callus tissue was compared. It was found that low concentrations of indoleacetic acid (IAA, 0.1 μM), gibberellic acid (GA, 0.3 μM), and benzyl adenine (BA, 0.03 μM) stimulate external ferricyanide reduction in normal tobacco callus cells, but inhibit this reaction up to 67% in transformed cells when hormones are applied to cells 10 min prior to assay. Higher concentrations of these growth regulators (1 μM or greater) inhibit transmembrane ferricyanide reduction in both types of cells, with the exception of IAA, giving an initial stimulation of the rate (12%), followed by 24% inhibition after 2 min. The observed external ferricyanide reduction by whole tobacco callus cells may be explained on the basis of a transplasmalemma redox system, which may be associated with the iron metabolism of these cells.     

Aerial web-weaving spiders: Linking molecular and organismal processes in evolution

Aerial web-weaving spiders display a wide variety of foraging behaviors that can be tied to the evolution of one family of proteins, the silks. In some cases, the physical structure and mechanical properties of silks alone determine the ecology of spiders: the habitats in which they forage, the prey they capture and their subsequent reproductive success. Future studies that integrate research on the physical structure of silks, the molecular genetics of silk synthesis and the foraging ecology of spiders in primitive and derived phylogenetic groups could reveal how molecular and organismal processes interact in evolution.