14C-Metabolism in cultured cotyledon explants of radiata pine

Excised cotyledons of radiata pine ( Pinus radiata D. Don), cultured under shootforming (plus cytokinin) and elongating (minus cytokinin) conditions, were incubated in ¹⁴C-glucose, ¹⁴C-acetate or ¹⁴C-bicarbonate at different stages of growth and differentiation. ¹⁴CO₂ was produced when the cotyledons were fed ¹⁴C-glucose and ¹⁴C-acetate (no measurement was made for ¹⁴C-bicarbonate feeding). Label from these precursors was incorporated into ethanol-soluble and -insoluble fractions. The largest percentage of radioactivity was associated with the ethanol-soluble portion, which was further fractionated into lipids, amino acids, organic acids and sugars. The amount of label and the pattern of labelling associated with each of the above classes of metabolites varied with time in culture and morphogenetic behaviour of the cotyledons. In general, there was a tendency towards a high rate of incorporation of label in elongating cotyledons during the period of rapid elongation. On the other hand, a high rate of incorporation of label in shoot-forming cotyledons coincided with the period of meristematic tissue formation. The data obtained support the hypothesis that organized development in vitro involves a shift in metabolism, which precedes and is coincident with the initiation of the process.     

Feeding ecology of the earliest vertebrates

Based on protochordates and extant fish, the earliest Palaeozoic vertebrates were microphagous suspension-feeding animals that pumped food-carrying water very slowly and thus required highly concentrated suspensions. Such conditions exist in benthic (not open water) aquatic environments. Feeding modes which on the basis of extant fish are closely related to benthic microphagous suspension feeding include deposit feeding, epilithic algal scraping, and macrophagous suspension feeding; early jawless vertebrates are predicted to have included all these feeding types. The gnathostome condition is predicted to have followed an initial switch from feeding on suspensions to taking tiny individual food particles (microphagous suspension-feeding → microphagous particulate-feeding → macrophagous particulate-feeding).     

Aphytophagy in butterflies: its relationship to myrmecophily

The regular or obligate aphytophagy of certain lycaenid butterflies (Lepidoptera) is discussed within the framework of the most recent general classification of the family. A summary survey of all Lycaenidae known to be aphytophagous is presented, together with a brief account of cannibalism and other opportunistic aphytophagy exhibited by normally phytophagous butterflies. The range of food sources (plants, animals, excretions and regurgitations) exploited by lycaenids is reviewed with emphasis falling on the ecology of myrmecophilous early stages and the significance of their ant-related adaptations. Adult feeding and oviposition behaviour reveal further associations with ants. Specificity of lycaenid/ant relationships and the possible biological effects of aphytophagy on the Lycaenidae are discussed. Finally, speculations concerning the evolution of aphytophagy by these butterflies are critically presented.     

Chronobiological aspects of the host-parasite relationships between Biomphalaria glabrata and Schistosoma mansoni: cercarial production and infectivity, and growth kinetics of the host

In the Biomphalaria glabrata-Schistosoma mansoni association, variations in cercarial production, in cercarial infectivity, and in the growth of infected snails are rhythmic. These chronobiological aspects are correlated with the dynamics of the intramolluscan larval stages of the parasite during the course of the infection. Rhythmic variations in the growth kinetics of infected snails are interpreted in terms of host-parasite metabolic exchanges.     

Heydenius dominicus n. sp. (Nematoda: Mermithidae), a Fossil Parasite from the Dominican Republic

Heydenius dominicus n. sp. is described as a new species of fossil mermithid nematode from Dominican Republic amber. The species is represented by two specimens of parasitic juveniles that left their insect host and became embedded in the resin. The nematodes are associated with an adult male limoniid (Diptera: Limoniidae) and an adult female mosquito (Diptera: Culicidae). The parasites are thought to have emerged from the mosquito host. This is the first report of a fossil mermithid from a Neotropical area.     

Histopathology of Okra and Ridgeseed Spurge Infected with Meloidodera charis

Histological observations of okra Abelomoschus esculentus ''Clemson Spineless'' and ridgeseed spurge Euphorbia glyptosperma (a common weed) infected with Meloidodera charis Hopper, indicated that the juvenile nematode penetrated the roots intercellularly. Within 5 days after plant emergence the nematode positioned its body in the cortical tissue parallel to the vascular system. By 10 days after plant emergence the juvenile had extended its head into the vascular system and initiated giant cell formation, generally in protophloem tissue. Giant cells were one celled and usually multi-nucleate. Eggs were observed in the female body 30 days after plants emerged and juveniles were found within the female body by 40 days. Nematode development progressed equally in the root system of either host plant. Generally, throughout the nematode''s life cycle its entire body remained inside the cortical tissue of okra. In ridgeseed spurge, however, the posterior portion of the female erupted through the host epidermis as early as 15 days after plant emergence; only the head and neck remained embedded in the host. The nematode caused extensive tissue disruption in the cortical and vascular system of both plant species. Corn, Zea mays, was another host of the nematode.     

长江口白鲟幼鱼的形态、生长及其食性的初步研究

1985年6—10月于长江口共获得白鲟当年的1龄幼鱼标本49尾(体长80—530毫米),进行了有关形态、生长以及食性的观察研究。①幼鱼形态与成鱼基本相似,其体长与体长,眼径以及体长／吻须长呈明显的正相关;③6月21日至10月12日间的幼鱼长度生长方程为Lg=79．9723e^0.0213t(式中Lg为体长,毫米;t为天数),其相对增长率以8月为最快;④长江口白鲟幼鱼摄食频度为100％,平均胃饱满指数为198．46,它们是肉食性鱼类,以底栖小型虾类和鱼类为主食,食物共有8类16个可鉴别种类;④考虑到这种珍稀鱼类的种群与资源衰退现状,建议在长江河口区制定必要韵保护措施。     

Behavioural response of spider mites (Tetranychus urticae) to induced resistance of cotton plants

ABSTRACT.

• 1 Spider mites (Tetranychus urticae Koch) given a choice between a cotton plant previously damaged by mites and an undamaged control preferentially moved to the control plant.
• 2 This host-choice behaviour was seen in adult female mites but not in immatures.
• 3 Adult females were not found to be significantly more fecund on control plants than on previously damaged plants, but the duration of this choice experiment precluded full assessment of effects on fecundity.
• 4 Mites responded very quickly, choosing previously undamaged plants without contacting or feeding on the test plants. This suggests that an olfactory response to a chemical substance(s) is involved.

     

Attachment may be a basis for specialization in oak aphids

ABSTRACT.

• 1 The potential role of tarsal attachment in host selection was studied in the specialist aphids Tuberculoides annulatus Hartig and Myzocallis schreiberi Hille Ris Lambers and Stroyan.
• 2 M.schreiberi could walk freely on its host, Quercus ilex and on Q.robur, whereas T.annulatus could walk freely on its host, Q.robur but had difficulty on Q. ilex.
• 3 Attachment to the rough-textured leaves of Q.robur was achieved by means of the pretarsal claws, and to the smooth upper surface of individual trichomes on the lower surface of Q.ilex using flexible pretarsal empodia.
• 4 Both behavioural and allometric differences can account for the inability of T.annulatus to grip onto Q.ilex.
• 5 The role of attachment by phytophagous insects in host plant resistance and selection is discussed.