Gonadectomy and growth ofTaenia crassiceps (Cestoda) cysticerci in mice

Summary Gonadectomy of SWR of both sexes significantly reduced the number of cysticerci ofTaenia crassiceps, 60 days post infection. There was a significant decrease in the total number of larvae and the number of nonbudding individuals, corresponding with increased number of budding larvae. This indicates that the asexual multiplication of cysticerci in populations from gonadectomized mice was inhibited.     

Cannibalism inAnopheles pharoensis Theo.

Summary A single 4th instar larva ofAnopheles pharoensis could consume within 24 h an average number of 5.3–11.6 larvae of the 1st instar. The number consumed differed according to crowdedness and the presence of other mature larvae. Dissection of the midgut of these larvae revealed the presence of various undigested parts of young larvae.Acknowledgments. This work was carried out in the Institute of Genetics, Mainz University, Federal Republic of Germany, through a fellowship to the author by the Alexander von Humbolt Foundation, Bonn, FRG, to whom the author is thankful for their support.     

Environmental temperature and the growth ofTaenia crassiceps cysticerci in mice

Summary Mice kept at low (5±1 °C) and high (35±1 °C) temperature harboured significantly lessTaenia crassiceps cysticerci than controls kept at 21±1 °C. This effect was more pronounced in heat-stressed than in cold-stressed animals and more in males than in females.     

Spermatogenesis is extraordinarily accelerated in metamorphosis-arrested larvae of a salamander,Hynobius retardatus

Laboratory experiments were conducted to induce neoteny inHynobius retardatus, which had been reported to propagate in larval forms like axolotl. A large number of newly hatched larvae were reared in an aqueous solution of thiourea (TU) and sodium perchlorate (SPC) in order to arrest the metamorphosis. Gonadal development in the metamophosis-arrested larvae was compared with that in normally metamorphosing and metamorphosed controls. Metamorphosis-arrested male larvae produced morphologically mature spermatozoa approximately 4 months after hatching, when the gonads in the controls began to differentiate into testes, or to show the premeiotic proliferation of germ cells. Possible endocrine controls of these phenomena are discussed.     

Cryopreservation of parasites

In this review, advances in cryopreservation of helminth parasites are reported. Our own studies demonstrate that metacestodes of Echinococcus multilocularis can be maintained in a viable state for at least 1-2 years by appropriate deep-freezing and storage in liquid nitrogen. Infective larvae of the nematode Toxocara canis cryopreserved for 1 week in liquid nitrogen were maintained after thawing in vitro in a chemically defined medium for 35 weeks. Although motility of previously deep-frozen larvae was reduced they produced secretory/excretory antigens of similar immunodiagnostic quality as those from unfrozen larvae. Whereas infective larvae of several species of trichostrongy-lids can be easily cryopreserved, the infective larvae of the cattle lungworm, Dictyocaulus viviparus, and muscle larvae of Trichinella spiralis are more sensitive to damage by subzero temperatures. Therefore, survival rates after cryopreservation are low, but improvement of the cooling schedules appears to be feasible. It is concluded that cryopreservation of certain stages of helminth and protozoan parasites is a useful technique for long-term storage of defined isolates, which can contribute considerably to reducing the number of experimental animals usually required for serial passages.     

Cryopreservation of parasites

Summary In this review, advances in cryopreservation of helminth parasites are reported. Our own studies demonstrate that metacestodes ofEchinococcus multilocularis can be maintained in a viable state for at least 1–2 years by appropriate deep-freezing and storage in liquid nitrogen. Infective larvae of the nematodeToxocara canis cryopreserved for 1 week in liquid nitrogen were maintained after thawing in vitro in a chemically defined medium for 35 weeks. Although motility of previously deep-frozen larvae was reduced they produced secretory/excretory antigens of similar immunodiagnostic quality as those from unfrozen larvae. Whereas infective larvae of several species of trichostrongylids can be easily cryopreserved, the infective larvae of the cattle lungworm,Dictyocaulus viviparus, and muscle larvae ofTrichinella spiralis are more sensitive to damage by subzero temperatures. Therefore, survival rates after cryopreservation are low, but improvement of the cooling schedules appears to be feasible. It is concluded that cryopreservation of certain stages of helminth and protozoan parasites is a useful technique for long-term storage of defined isolates, which can contribute considerably to reducing the number of experimental animals usually required for serial passages.     

Variation in chromosome number in the sheep headflyHydrotaea irritans (Fallen) (Diptera: Muscidae)

Summary Variation in the number of chromosomes was found in sheep headflies, ranging from 12 to 15 chromosomes. Of these, five pairs were common among all individuals. Among 9 larvae no males were identified.     

The prey consumption and prey preference of the larvae of the mosquitoCulex (Lutzia) raptor on the larvae ofCulex quinquefasciatus

The maximum consumption of the larvae of the pest and vector mosquitoCulex quinquefasciatus by the predatory mosquitoCulex (Lutzia) raptor was studied at various instars of both the predator and the prey. The prey preferences of the predator when given lavae of different instars were also investigated. The IVth instar of the predator consumed the maximum number of Ist instar and the maximum biomass of IVth instar larvae of the prey. Instars I and II of the predator preferred the Ist of the prey; instars III and IV of the predator preferred instars II and III of the prey respectively.The predator consumed an average of 157.1 larvae during its whole larval period, when each instar of the predator was given its preferred instar of the prey.     

Crystal cell pattern modification in a melanotic tumor strain ofDrosophila melanogaster

Summary 3rd instar larvae of the melanotic tumortu-pb strain ofDrosophila melanogaster hold a lower number of free-circulating crystal cells in their hemolymph than the wild type ones. This pattern could result from an abnormal retention of mature crystal cells in the hematopoietic organs, as the strong hemocyte melanization inside the lymph glands of heat-treatedtu-pb larvae seems to demonstrate. Melanotic tumor formation and modification of the crystal cell pattern may be related.     

Effects of a juvenile hormone mimetic,fenoxycarb, on post-embryonic development of the European corn borer,Ostrinia nubilalis Hbn.

Summary The effect of a juvenile hormone mimetic, fenoxycarb, Ro 13-5223, was tested on the larval instars of the European corn borer,Ostrinia nubilalis, by dipping or topical application. When larvae were treated in instars 2, 3 or 4, the duration of the fifth instar was modified. More permanent and fewer supernumerary larvae were obtained when treatment occurred in the early instars. This non-neurotoxic compound exhibited a strong dose-dependent juvenile hormone type of activity when it was applied to last instar larvae. Fenoxycarb prevented the onset of pupation and produced supernumerary larvae and intermediates. Permanent larvae were obtained if fenoxycarb was applied on day 0 or day 1 of the last instar. The use of such a JH mimetic in the understanding of endocrine control of diapause is discussed.     

Differential lethality following treatment with ionizing radiations of various energies in Drosophila

Male and female gametes of Drosophila were treated with various doses of ionizing radiations: X-rays at different energy, and gamma-rays from 2 sources given singly and in 2 temporal sequences. The induced lethality was assessed in successive developmental stages by scoring the number of eggs, larvae and adults. The results clearly show that the effects of various radiations appear in terms of difference among developmental stages and/or between treated sexes/genotypes. It is suggested that the various energies affect different gene functions which are not completely independent, as supported by the non-additive effects of the two temporal sequences.     

DNA synthesis in the nuclei of differentiating muscle fibers of the silkworm,Bombyx mori L.

Summary Incorporation of³H-thymidine (³HTdr) into the nuclei of myofibril-containing myofibers of larvae of the silkworm,Bombyx mori, was shown by means of light microscope (LM) and electron-microscope (EM) autoradiography. The number of DNA-synthesizing myonuclei attains 42% 12–18 h after each molt. Thus in the developing silkworm DNA replication and myofibrillogenesis are coexisting and not mutually exclusive processes as is the rule in vertebrate somatic myogenesis.     

The influence of juvenile hormone on the feeding behaviour of last instar larvae of the codling moth,Laspeyresia pomonella (Lep., Tortricidae), reared under different photoperiods

Summary Duration of the feeding stage and corresponding weight increase during the last larval instar of the codling moth,Laspeyresia pomonella, are controlled by JH. Larvae reared under short day conditions have a relatively high titer of JH during the last larval instar and enter diapause as mature larvae. They feed longer and become heavier than larvae reared under long day conditions, which have no JH during the last larval instar and pupate when mature. By application of the JH mimetic Altosid^® during the first 2 or 3 days of the last larval instar, the duration of feeding activity of larvae reared under respectively long and short day conditions was prolongated and the larvae became significantly heavier. The feeding behaviour could only be influenced by the juvenoid as long as the feeding activity of the larvae had not yet ceased.     

Biotransformation of polyprenols by the larvae of Pieris rapae crucivora

The biotransformation of cleomeprenols-1-3H by the larvae of Pieris rapae crucivora Boisduval has been investigated. It was found that cleomeprenols fed to the larvae are transformed into long chain fatty acid esters that are excreted in the feces.     

Detection of toxic metabolites in the hemolymph ofBeauveria bassiana infectedSpodoptera exigua larvae

Highly active metabolites have been detected in the hemolymph of the lepidopteranSpodoptera exigua infected with the mycopathogen,Beauveria bassiana. A combination of phenyl sepharose and CM ion exchange chromatography was utilized to extract the active metabolites from infected hemolymph samples. The active in vivo metabolites, having a molecular mass greater than 10 KDa, were thermolabile and were inactivated by proteinase K. These metabolites were characterized by their ability to disrupt metamorphosis, killing treated larvae at the wandering or pupal stage. Additionally, injection ofS. exigua larvae with active samples caused a reduction in the number of filopodial-producing hemocytes. The biological activities and biochemical properties suggest that novel compounds are produced duringB. bassiana mycosis.     

Homoplastische Transplantationen embryonaler Zellen in differenzierte Gewebe

Summary The intermediate mesoderm (8th–12th somite) of early tailbuds ofTriturus alpestris was transplanted into the lateral body wall of 12 mm larvae. The differentiation of opisthonephros tubules, primordial gonad and a new coelom was observed in 21 mm larvae 23 days after implantation.     

Invertase activity in the midgut ofSarcophaga ruficornis andMusca domestica (diptera: Insecta)

Summary The pH for the optimum activity of the midgut invertase was 5.5 in the adults ofS. ruficornis, 6.0 in its larvae and adults ofM. domestica and 6.5 in the larvae of the latter fly. The optimum temperature was 50°C. Enzyme activity was retarded by the addition of glucose and fructose.     

Analysis of the relationship between age of larvae at mutagen treatment and frequency and size of spots in the wing somatic mutation and recombination test inDrosophila melanogaster

The relationship between the induction of mutant clones and the time of mutagen treatment was studied in the somatic mutation and recombination test (SMART) in wing cells ofDrosophila melanogaster. Larvae trans-heterozygous for the recessive marker mutations multiple wing hairs (mwh) and flare (flr) were produced. Batches of these larvae were then treated with mutagen at different ages spanning all three larval instars. Methyl methanesulfonate was fed acutely for 2 h by immersing the larvae in a solution of the mutagen mixed with powdered cellulose. Wings of the surviving adult flies were mounted and scored for the presence of spots. The frequency and size of single and twin spots were recorded separately. Twin spots are produced exclusively by mitotic recombination, whereas single spots can results from various types of mutational and exchange events. There exists a clear correlation between time of induction and frequency as well as size of the single spots. In young larvae only few but very large spots are induced, whereas in older larvae the frequencies are considerably increased but the sizes are smaller. The twin spots show a different relationship. Practically no twin spots are found in very young and in very old larvae. The results demonstrate that in the wing spot test the optimal age of the larvae for mutagen treatment is 72 h.     

Zuchtmethode und semisynthetische Nährmedien für Apfelwickler

Summary A method for the individual rearing of the codling mothLaspeyresia pomonella is described. The method allows the collection of exactly dated eggs and the rearing of a large number of larvae in a small space. By using the second medium described, it is possible to watch all developmental stages at any time without disturbing them. The average larval survival rate is 70–80%.     

Inhibitory effect of bacterial ubiquinones on the settling of barnacle,Balanus amphitrite

In an attempt to clarify the influence of marine bacteria on the settling of fouling invertebrate larvae, we screened for inhibitors, produced by marine bacteria, of settling by cyprids of the barnacle,Balamus amphitrite. We found that the culture broth ofAlteromonas sp. strain number KK10304, which was associated with the marine sponge,Halichondria okadai, effectively inhibited settling of the cyprids. Bioassay-guided isolation indicated ubiquinone-8 (1) as an effective inhibitor of cyprid settling. As ubiquinones are widely distributed in bacteria, several related compounds were also tested.