The Stability to Temperature of Lysosomes in Homogenates of Tetrahymena pyriformis

SYNOPSIS. The effect of temperature on the stability of lysosomes in homogenates of T. pyriformis at pH 8.1 was studied thruout the temperature range 0–35 C and compared with the stability of lysosomes in homogenates of rat liver and kidney. The lysosomes from T. pyriformis are unstable on exposure for 30 min to temperatures greater than 10–15 C; this instability does not appear to depend on strain, culture medium, growth temperature or the presence or absence of agents which affect the stability of lysosomal membranes.     

Host plant toxins and unpalatability of Neacoryphus bicrucis (Hemiptera: Lygaeidae)

Abstract. 1. Host plant choice of the seed bug, Neacoryphus bicrucis Say (Hemiritera, Lygaeidae), was evaluated in four different Georgia habitats. N. bicrucis utilized only species of Senecio as host plants at a granite outcrop and at old fields on the coastal plain, in the piedmont, and in the Blue Ridge Mountains.
2. In laboratory tests N. bicrucis is distasteful to the green anole lizard, Anolis carolinensis Voight. Only six of ninety field-collected bugs were eaten in palatability trials while eighty-four of the remaining ninety attacked bugs were rejected by lizards without apparent harm. However, the bugs were palatable to Fowler's toads, Bufo woodhousei fowleri Hinckley, which ate all thirty-six bugs offered to them.
3. N. bicrucis selectively sequesters pyrrolizidine alkaloids from Senecio spp. These may cause the insects' distastefulness to green anoles. In palatability trials, lizards ate all twenty insects reared on sunflower seeds, Helianthus annus, but rejected all twenty reared on Senecio smallii.     

Effect of Photoperiodic Induction on the Transpiration Rate and Stomatal Behaviour of Debudded Xanthium Plants

In controlled-environment studies with debudded Xanthium plants,appreciable changes in stomatal activity and attendant ratesof transpiration were found to be associated with photoperiodicinduction. Leaves of plants kept on a 10-h inductive photoperiodafter removal of the apical and axillary buds grew at ratescomparable to those of similarly debudded plants kept on a 10-h-interruptednon-inductive photoperiod (consisting of an 8-h photoperiodand a 2-h interruption of the dark period). There was a large effect of leaf age on stomatal behaviour:the minimum stomatal resistance of leaves of non-induced plantsdecreased from about 5 s cm^–1 when the leaf was 25 percent of its final size to 1.6 s cm^–1 when almost fullyexpanded. Thereafter, it slowly increased with time. Superimposedon this age response was a marked effect of photoperiodic induction.The stomata on induced leaves opened more widely than thoseon non-induced leaves, the response being greatest with theleaves which were youngest at the time induction commenced.However, this ‘opening’ tendency was maintainedfor only a few weeks; thereafter, the stomata failed to openas widely. This later ‘closing’ tendency of stomataon leaves of induced plants progressed rapidly and in a basipetalsequence and presaged a necrotic form of leaf senescence whichdeveloped in the same sequence. The closing tendency on leavesof non-induced plants progressed slowly in an acropetal direction;leaves senesced in the same sequence with the familiar yellowingsymptoms. It is suggested that flower induction sets in train a sequenceof events which influence stomatal movement (and other processes)and inevitably leads to the death of the induced axis. Transpiration rates calculated from measurements of the physicalenvironments and stomatal resistances agreed well with thosemeasured.     

Ovipositor internal microsculpture in the Braconidae (Insecta, Hymenoptera)

Variation in the microsculpture of the ovipositor egg canal, the morphology of the tip of the upper valve, the structure of the valvillus and the apex of the lower valve seals, as revealed by scanning electron microscopy is described for members of 52 genera representing 30 subfamilies of Braconidae. The possible phylogenetic implications of this variation are discussed. Characters supporting monophyly of the cyclostome clade, and of the non-cyclostome subfamilies Agathidinae, Pselaphaninae and Sigalphinae are reported. Functional and phylogenetic implications are discussed and possible convergent evolution of some features associated with endoparasitism are considered in the light of recent molecular systematics findings. © 1998 The Norwegian Academy of Science and Letters     

Three new genera of Braconini from Australasia and Malaysia (Insecta, Hymenoptera, Braconidae)

Ancilibracon gen.n. (type species: Ancilinracon townesi sp.n.). Ancilibracon bakeri sp.n., Gelasinibracon gen.n. (type species: Gelasinibracon sedlaceki sp.n.), Gelasinibracon simplicicaudatus sp.n., Esengoides gen.n. (type species: Esengoides crentdatus sp.n.) and Esengoides fulvus sp.n. are each described and illustrated. Ancilibracon towensi is from Malaysia. A. bakeri is from Borneo, both Gelasinibracon species are from Guinéa, E. crenulatus is from the solomon Islands and E. fulvus is from Australia. These three new genera belong to the Plesiobrscon Cameron group of the Braconina. Their relationship are discussed.     

Paternal Behavior in Rodents

The literature on paternal behavior in rodents includes reportsof many species; however, paternal behavior appears more prevalentamong muroid and hystricomorph rodents than in the sciurids.Many reports of paternal behavior are based on small numbersof animals observed under special conditions. Where systematicstudies have been conducted, the most salient feature of rodentpaternal behavior is its lability. The occurrence varies withobserver constraints, genotype, experience, social conditionsduring observation, and stimulus characteristics. This intraspecificvariability renders application of the comparative method inunderstanding evolution difficult but may provide a key in theremarkable adaptation of rodents to diverse habitats. Althoughspecies differences exist the evolution of rodent paternal behaviorappears to entail changes in the thresholds and conditions forthe occurrence of a relatively few basic motor patterns of paternalcare.