Long-term storage of eggs of Simulium ornatum

A method for the storage of non-diapausing eggs of Simulium ornatum Meigen has been developed. High survival rates for 5-6 months depend on the age of eggs when placed at reduced temperature. A period of precooling or conditioning is required for 28 days before storage of the eggs at 1 degree C with lowering of oxygen partial pressure. Induced quiescence does not appear to affect development from egg to adult.     

A comparison of the energetics of foraging of three species of Leptogenys (Hymenoptera, Formicidae)

Abstract. The three Leptogenys species L.nitida, L.schwabi and L.attenuata coexist in the coastal forests of South Africa and exhibit an array of foraging strategies ranging from individual foraging to group raiding. To determine whether there is a physiological basis for these strategies, the energetic cost of locomotion of individuals in these three species was determined. Carbon dioxide emission of voluntary running ants was measured using a flow-through technique, in order to determine their metabolic rate when running. The minimum cost of transport was constant over a range of temperatures (20–35°C), and similar for all three species (common value 212.96 ± 17.35 Jkg^_1m^_1). A comparison of the energy required to sustain representative foragers at 25°C indicated that it was energetically less expensive for L. nitida workers to forage than for the other two species. This may explain why L.nitida uses group raiding, while the other two species use individual foraging with limited recruitment for retrieval of large food items.     

Some cytological aspects of antagonism in synthesis of nucleic acid

Summary The effects of solutions of benzimidazole and 5-aminouracil onAllium cepa root meristems immersed in them have been studied cytologically. Benzimidazole and 5-aminouracil, analogues of purines and pyrimidines respectively, reduce the number of nuclear divisions being initiated. A marked decline in frequency of cells in mitosis occurs at the beginning of treatment with benzimidazole (300 p.p.m.) but not until 6 or more hours later with 5-aminouracil (125 p.p.m.).After treatment with 5-aminouracil, small interstitial portions of chromosomes are Feulgen-negative and become extended during anaphase into thin strands. The distal portion of these chromosomes may lag during anaphase and contribute to malformations of the surface of the sister nuclei and to micronuclei-like bodies lying along their adjacent surfaces. However, stickiness resulting in chromosome bridges was not observed. After treatments with benzimidazole, chromosomes are more contracted at metaphase and anaphase than in the control. At the concentrations used, neither component was observed to affect the spindle mechanism of the divisions in progress at the beginning of treatment nor of the divisions which escape inhibition.Reversal of these effects by the introduction of metabolites which these analogues resemble structurally, was investigated. Adenine sulphate (800 p.p.m.) acts antagonistically to benzimidazole (300 p.p.m.) by delaying the marked decline in frequency of mitoses by more than 6 hrs. By 12 hrs. the frequency of cells in mitoses was very low; thus, reversal is not permanent. Half the inhibition of growth caused by 5-aminouracil (50 p.p.m.) is reversed by thymine (50 p.p.m.) for the 24 hrs. of the test period. When 5 p.p.m. folic acid was added to this mixture, root growth exceeded that of the controls. Feulgen-negative gaps, however, are still present in chromosomes at anaphase.Estimations of Feulgen content of nuclei to determine the effect of these treatments on DNA synthesis were made by means of a microphotometer. In control roots there are two classes of nuclei at interphase according to the amount of DNA per nucleus. The amount doubles during interphase before the next division of the nuclei in the root meristem. In roots treated with 5-aminouracil this doubling is inhibited, so that interphase nuclei with the lower amount of DNA accumulate. In roots treated with benzimidazole the relative frequencies of the two classes of nuclei is unaltered; however, mitotic activity is inhibited. This compound apparently affects not only processes concerned with doubling the amount of DNA per nucleus but also processes necessary to the division itself. There was, however, no unquestionable evidence of a nucleus being reconstituted after it had started a division.Contribution from the Program in Cytology, Department of Botany University of Wisconsin, Madison, supported in part by grants to Dr.C. Leonard Huskins from the American Cancer Society, Rockefeller Foundation, and Research Committee of the Graduate School with funds supplied by the Wisconsin Alumni Research Foundation.     

Indices of condition in tropical ruminants*

Bone marrow dry weight expressed as a percentage of its fresh weight was found to be a good indication of its fat content in wildebeest, kongoni, and buffalo. The calculated regression equations were similar enough to suggest a more general formula for the larger ruminants. Bone marrow fat is mobilized after the kidney fat and hence is a better measure of condition when an animal is under more extreme stresses. Fluctuations in kidney fat reflect physiological events related to reproduction. Visual estimates of bone marrow were found to reflect true differences in fat content, and the method is useful when marrow samples cannot be collected readily. It is pointed out that estimates of condition of naturally dying wild animals must be obtained before primary and secondary causes can be identified.     

Anomalous Growth in the Stem of Ipomoea batatas (L.) Lam. Infested with Megastes Larvae

The stem of Ipomoea batatas (L.) Lam. is characterized by thepossession of a ring of bicollateral, leaftrace bundles. Lacticifersoccur in the pith, in the parenchyma between neighbouring islandsof medullary phloem, and in the cortex. The xylem groups become united by the activity of the inter-fascicularcambium. The production of a certain amount of secondary xylemtakes place before the production of secondary phloem begins.The former is produced more extensively in some areas than inothers, so that the original symmetry of the vascular cylinderis lost. The phellogen originates in the cells of the epidermis. When the stem is attacked by the larvae of Megastes grandalisGuen., which remove most of the internal tissues, anomalousgrowth takes place as a result of the activity of accessorycambia, which develop in the primary cortex, the secondary phloem,and the phelloderm. Residual parenchyma of the pith and/or xylemundergoes hyperplasia to produce a callus tissue which linesthe cavity made by the larvae.