Patterns comportamentali delle operaie di Bombus terrestris (Hymenoptera, Apidae) in colonie artificiali

Università degli Studi di Sassari, Dipartimento di Protezione delle Piante, Sezione di Entomologia Agraria

Behavioural patterns of Bombus terrestris L. (Hymenoptera Apidae) workers in captive colonies

In bumblebee societies with great plasticity in division of labour and no age-based polyethism, the existenceof a social hierarchy among workers has been recognized during all periods of colony development. This study,performed on three caged “mature” colonies of Bombus terrestris, aimed to identify and compare the behaviouralpatterns of the workers obtained by means of focal animal sampling performed during 25 hours on three randomlyselected workers for each colony. Results showed that the workers devoted most of the time to non-task behaviours,about 30% to task activities and little time to social interactions (5%) and aggressive acts (5%). From thecomparisons among colonies, differences in the stage of colony development were detected and it emerged that, atthe moment of the recordings, no colony had actually reached the initiation of the competition phase, although oneof them was probably the closest to this point

Patterns comportamentali delle “regine” e delle “operaie” di Bombus terrestris (Hymenoptera, Apidae) in colonie sperimentali

La specie Bombus terrestris (Hymenoptera, Apidae) comprende insetti ad azione pronuba costituenti piccole società matriarcali, annuali. Queste, pur essendo strutturate in modo relativamente semplice, vengono riconosciute come primitivamente eusociali. Infatti sono caratterizzate da comportamenti semplici, scarsa comunicazione su base chimica, una inibizione riproduttiva della “regina” sulle “operaie” (determinata tramite comportamenti aggressivi e feromoni reali) decrescente nel corso dello sviluppo coloniale ed una suddivisione del lavoro poco marcata. Con questa ricerca ci si proponeva di studiare, utilizzando un sistema di videoregistrazioni ed un apposito programma per l’analisi dei dati osservati (“The Observer”; Vers. 3.0, Noldus 1995), le durate e le frequenze dei comportamenti esibiti dalla “regina” e dalle “operaie” di colonie sperimentali di B. terrestris. Sono state dunque eseguite registrazioni della durata di 5’, ripetute a distanza di 60’, per un totale di 25 replicazioni nell’arco della giornata, su tre differenti colonie. Per le regine le registrazioni sono state ripetute a distanza di 15 giorni. Sono stati selezionati 19 comportamenti tra i membri delle colonie e questi sono stati riuniti in quattro categorie comportamentali (attività “comuni”, comportamenti di “interazione tra individui”, attività “lavorative” e comportamenti aggressivi). Alcuni sono risultati simili a quanto riportato da Dietz (1982) nelle colonie di Apis mellifera e debbono pertanto essere considerati caratteristici di una società di Imenotteri. Tra questi troviamo resting, feeding, walking, self-grooming, out (l’operaia si allontana dall’area di covata), antennation, inspecting, cleaning cells, brood care e under (l’operaia si trova sotto gli strati della covata).Tra i patterns esibiti alcuni presentavano durate e frequenze simili, dimostrandosi biologicamente importanti per la specie B. terrestris (ad esempio feed), mentre altri venivano effettuati con durate e/o frequenze variabili .Inoltre abbiamo potuto constatare che, nonostante la fase avanzata di sviluppo della colonia, le regine mantengono un discreto livello di attività, sebbene questa sia concentrata sulla cura delle larve piuttosto che sulla manutenzione e l’ampliamento del nido (mansioni queste che sono affidata alle operaie)

A morphological and ultrastructural study of Telosentis exiguus (Acanthocephala, Palaeacanthocephala)

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Immediate and delayed effects of in vitro ischemia on glutamate efflux from guinea-pig cerebral cortex slices

Immediate and delayed effects of glucose deprivation, oxygen deprivation (hypoxia) and both oxygen and glucose deprivation (in vitro ischemia) on glutamate efflux from guinea pig cerebral cortex slices were studied. Immediate effects were evaluated by measuring changes of glutamate efflux during the metabolic insults. Delayed effects were evaluated by measuring the response of the tissue to a 50 mM KCI pulse applied 60 min after the metabolic insults. Deprivation of glucose in the medium did not induce either immediate or delayed effects, while hypoxic condition produced an immediate slight stimulation of glutamate efflux without any delayed effect. Conversely, in vitro ischemia produced both immediate and delayed effects on glutamate efflux. During in vitro ischemia glutamate efflux dramatically increased in a calcium-independent and tetrodotoxin-sensitive manner; this effect was potentiated by a low sodium containing medium. The blockade of the sodium/potassium ATPase exchanger by ouabain caused a glutamate outflow similar to that induced by in vitro ischemia. On the whole, these data demonstrate the central role played by the sodium electrochemical gradient and by the membrane glutamate uptake system in the glutamate overflow induced by in vitro ischemia. Moreover, in slices previously exposed to both oxygen and glucose deprivation the effect of KCI on glutamate efflux was potentiated. This in vitro ischemia-induced delayed potentiation of neurotransmitter efflux, until now unreported in the literature, was found to be selectively restricted to glutamatergic structures and to be mainly due to an enhancement of the exocytotic component of glutamate release

Immediate and delayed effects of in vitro ischemia on glutamate efflux from guinea-pig cerebral cortex slices

Immediate and delayed effects of glucose deprivation, oxygen deprivation (hypoxia) and both oxygen and glucose deprivation (in vitro ischemia) on glutamate efflux from guinea pig cerebral cortex slices were studied. Immediate effects were evaluated by measuring changes of glutamate efflux during the metabolic insults. Delayed effects were evaluated by measuring the response of the tissue to a 50 mM KCI pulse applied 60 min after the metabolic insults. Deprivation of glucose in the medium did not induce either immediate or delayed effects, while hypoxic condition produced an immediate slight stimulation of glutamate efflux without any delayed effect. Conversely, in vitro ischemia produced both immediate and delayed effects on glutamate efflux. During in vitro ischemia glutamate efflux dramatically increased in a calcium-independent and tetrodotoxin-sensitive manner; this effect was potentiated by a low sodium containing medium. The blockade of the sodium/potassium ATPase exchanger by ouabain caused a glutamate outflow similar to that induced by in vitro ischemia. On the whole, these data demonstrate the central role played by the sodium electrochemical gradient and by the membrane glutamate uptake system in the glutamate overflow induced by in vitro ischemia. Moreover, in slices previously exposed to both oxygen and glucose deprivation the effect of KCI on glutamate efflux was potentiated. This in vitro ischemia-induced delayed potentiation of neurotransmitter efflux, until now unreported in the literature, was found to be selectively restricted to glutamatergic structures and to be mainly due to an enhancement of the exocytotic component of glutamate release

In vitro evidence for increased facilitation of striatal acetylcholine release via pre- and postsynaptic NMDA receptors in hemiparkinsonian rats

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