Digestive Enzyme Activity during Larval Development of Black Snook,Centropomus nigrescens

Black snook, Centropomus nigrescens, have been identified as a promising candidate for aquaculture although, like many of the Centropomid species, high mortality associated with early larval stages presents a significant bottleneck to their commercialization. The digestive capacity of black snook larvae throughout the first 37 d after hatch (d.a.h.) was evaluated by quantifying digestive enzyme activities using biochemical techniques. Results showed that black snook larvae have alkaline proteases at hatching, which are known to be important during the first days of feeding for digestion. Toward the end of the study, acid proteases concentration increased (37 d.a.h.). Enzymes for lipid digestion, pancreatic lipase and bile salt‐activated lipase, were already present in the larvae before exogenous feeding commenced, and their activity increased with age and growth (length). Intracellular digestion, measured as the activity of leucine‐alanine peptidase, was high early on (5 d.a.h.) and decreased as development progressed (next 32 d). In contrast, alkaline phosphatase activity was lowest at first feeding and subsequently increased with age. Overall patterns in enzyme activity suggest the possibility of live feed weaning before 32 d.a.h. if artificial diets can be properly balanced.     

Parasitoid Wasps as Flower Visitors in the Canadian High Arctic

Summary Collections and observations were made in 1963 and 1967 on insects visiting flowers at Hazen Camp and Gilman Camp on Ellesmere Jsland, N. W. T. Canada. The results giving the species of parasitoid Hymenoptera, the flowers visited, and their activity, are shown in this paper (Table 1).18 species with 50 specimens of 13 genera are listed. Most of them could be found feeding in the nectar of flowers and carrying pollen.The attractiveness of white blooms to parasitoid wasps, observed in different regions, also holds in the High Arctic, whereStellaria longipes visitors account for 35 in 7 genera out of a total of 41 in 13 genera.

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Zusammenfassung Parasitische Schlupfwespen als Blütenbesucher im kanadischen hohen Norden Im Sommer 1963 und 1967 wurden im Hazen Camp und Gilmann Camp auf der hochnordischen Ellesmere-Insel Beobachtungen und Sammlungen bezüglich Blüten besuchender Insekten durchgeführt. In der vorliegenden Arbeit sind in Tabelle 1 die gefundenen parasitischen Hymenopteren zusammengestellt.18 Arten mit 50 Individuen aus 13 Gattungen wurden gefunden, und zwar aus den Familien Chalcididae (3 Arten), Eulophidae (1), Pteromalidae (1), Braconidae (3), Ichneumonidae (9) und undeterm. (1). Am häufigsten war mit 22 Individuen die IchneumonideStenomacrus spec. anStellara-, Saxifraga- undDryas- Blüten vertreten. Es scheint, daß alle Ichneumoniden-Arten Nektar als Betriebsstoff für ihren Flug aufnehmen. Aber auch je eine Chalcididen-, Eulophiden- und Pteromaliden-Art wurden als Nektarfresser festgestellt.Von jeder beobachteten und anschließend gefangenen Schlupfwespe wird die Tätigkeit an der Pflanze skizziert. Am Körper der meisten Arten fanden sich Pollenkörper. Die in der Literatur aus anderen Gebieten der Erde berichtete besondere Attraktivität weißer Blüten auf parasitische Hymenopteren. wurde auch im Hohen Norden beobachtet: an den weißen Blüten vonStellaria longipes wurden 35 von 41 einzeln registrierten Individuen aus 7 Gattungen angetroffen.

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Contribution No. 920,Plant Research Institute of Agriculture, Canada Department, Ottawa, Canada.     

Sun-tracking solar furnaces in high arctic flowers: significance for pollination and insects

Heliotropic flowers (Dryas integrifolia, Papaver radicatum) act, in sunshine, as solar reflectors, their corollas focusing heat on the sporophylls. Considerable intrafloral temperatures are generated. Winds above 3.8 meters per second and cloud abolish the effect. Insects that bask in the flowers also gain heat. The phenomena areimportant in maximizing the small heat budget.     

Identification of a blue photoluminescent composite material from a combinatorial library

A quaternary combinatorial masking strategy was used in conjunction with photolithography to generate compositionally diverse thin-film phosphor libraries containing 1024 different compositions on substrates 2.5 centimeters square. A parallel imaging system and scanning spectrophotometer were used to identify and characterize compositions in the library with interesting luminescent behavior. Optimal compositions were identified with the use of gradient libraries, in which the stoichiometry of a material was varied continuously. This process led to the identification of an efficient blue photoluminescent composite material, Gd3Ga5O12/SiO2. Experimental evidence suggests that luminescence in this material may arise from interfacial effects between SiO2 and Gd3Ga5O12.     

Lunar Fe and Ti abundances: comparison of lunar prospector and clementine data

The Lunar Prospector neutron spectrometer data correlate well with iron and titanium abundances obtained through analysis of Clementine spectral reflectance data. With the iron and titanium dependence removed, the neutron spectrometer data also reveal regions with enhanced amounts of gadolinium and samarium, incompatible rare earth elements that are enriched in the final phases of magma crystallization. These regions are found mainly around the ramparts of the Imbrium impact basin but not around the other basins, including the much larger and deeper South Pole-Aitken basin. This result confirms the compositional uniqueness of the surface and interior of the Imbrium region.     

Two Analytical Methods for the Measurement of 2,4-D in Oranges: an ELISA Screening Procedure and a GC-MS Confirmatory Procedure

Two analytical methods are presented for the determination of 2,4-D in oranges. The screening procedure uses a commercial ELISA kit, designed for the determination of 2,4-D in water. Good semi-quantitative screening data were obtained provided that the standard solutions used to construct the calibration curve were prepared in blank orange extract. The limited quantification range of the kit was due to the narrow linear range and differences in response to 2,4-D when present as the free acid and as various esters. A GC-MS confirmatory technique involved extraction of 2,4-D from oranges by homogenisation with methanol, filtration and esterification/transesterification with boron trifluoride-methanol. Recoveries for three spiking levels (0·2, 1·0 and 2·0 mg kg^-1) for 2,4-D and 2,4-D isopropyl ester were within the range 75–120%. In a small survey of retail oranges, 10 samples were screened using the ELISA kit and four were found to have >0·2 mg 2,4-D kg^-1. All four residues were confirmed by GC-MS. The ELISA procedure involves approximately half the staff effort of the GC-MS procedure. © 1997 SCI.     

Disinfection of almaco jack (Seriola rivoliana Valenciennes) eggs: Evaluation of three chemicals

Almaco jack (Seriola rivoliana Valenciennes) is an excellent candidate for aquaculture due to its fast growth rate and high market value. While S. rivoliana have adapted well to captivity, survival at early life stages can be improved to increase profitability during production. A wide range of variables cause larval mortalities but high bacterial loads in rearing tanks are often correlated with these losses. The aim of this study was to investigate the effect of egg disinfection on bacterial load and hatch rate of S. rivoliana. Disinfectants tested included formalin (F100 and F200; 100 and 200 mg/L, respectively, for 60 min), hydrogen peroxide (HPO; 300 mg/L for 10 min) and peracetic acid/hydrogen peroxide (PAA/HPO; 15.7 mg/L/39.6 mg/L for 1 min). Concentrations and contact times were determined based on current use in marine aquaculture and preliminary trials. Eggs treated with HPO and F100 had significantly higher hatch rates than the untreated control group. All treatments significantly decreased total Vibrio counts compared to untreated eggs; however, total bacterial counts were only decreased following treatments with PAA/HPO and F200. To prevent egg mortality due to bacterial overgrowth, consideration should be given to the use of surface disinfection using HPO or F100. Future studies should investigate the use of peracetic‐based products at lower doses.     

Report on the 43rd Annual Meeting of the DPG-Working Group Nematology

Journal of Plant Diseases and Protection -     

Fatty acid utilization during the early larval stages of Florida pompano (Trachinotus carolinus) and Common snook (Centropomus undecimalis)

The pattern of conservation and loss of fatty acids from the yolk sac during the endogenous feeding period and subsequent starvation was studied in pompano and snook larvae. Fundamental information on the early fatty acid dynamic and mobilization of pompano and snook larvae was collected. In both species, fatty acids were utilized as an energy source after hatching. Mono‐unsaturated fatty acids were catabolized, while saturated and poly‐unsaturated fatty acids were conserved. High levels of arachidonic acid (ARA) in pompano and snook eggs, as well as selective retention in the unfed larvae suggest a high dietary requirement for this fatty acid during the early stages of larval development. The effect of an ARA supplementation was therefore investigated in snook larvae at the rotifer feeding stage. The fatty acid profile of the larvae was successfully influenced to match that of wild eggs; however, no significant improvement in growth or survival was observed. Future research should be carried out over a longer period of time and include factors related to stress resistance.