Mario Solinas

Identification of the gland secreting oviposition-deterring pheromone in the cabbage seed weevil, Ceutorhynchus assimilis, and the mechanism of pheromone deposition.

After laying an egg into a pod of Brassica napus, the female cabbage seed weevil, Ceutorhynchus assimilis, brushes the caudal setae of the eighth abdominal tergite (VIII UT) on the host pod as she walks along it, depositing oviposition-deterring pheromone (ODP). The VIII UT is periodically extended and withdrawn, thus repeatedly rubbing against the posterior fold of the seventh urotergite (VII UT) which bears the individual outlets of glandular epidermal cells. In post-diapause, sexually mature, gravid (i.e. oviferous) females (virgin or mated) the cells of this VII UT gland were hypertrophic, showing intense secretory activity. Extracts of VII UT from these individuals elicited strong electrophysiological responses from antennal club gustatory sensilla and deterred oviposition. In pre-diapause (sexually immature) females, the cells of the VII UT gland were neither hypertrophic nor active and an extract of their VII UT elicited no significant electrophysiological or behavioural response. Extract of female rectum was a less potent oviposition deterrent than VII UT extract and elicited an electrophysiological response similar to male rectum extract. An extract of ovarian calyces and ovaries elicited no behavioural response. We conclude that ODP is secreted by the epidermal cells of the VII UT posterior fold.

Ultrastructure of a tarsal sensillum of Delia radicum L. (Diptera : Anthomyiidae) sensitive to important host-plant compounds

Abstract The ultrastructure of a pair of tarsal “C” sensilla located on the ventromedial side near the distal margin of the 5th tarsomere of the female cabbage root fly, Delia radicum (L.) (Diptera : Anthomyiidae) was investigated by electron microscopy and electrophysiological recordings. This “C” sensillum is a typical gustatory sensillum, consisting of a uniporous hair-shaft inserted in a specialized socket and innervated by 5 sensory neurons (i.e. one mechanosensitive and 4 chemosensitive). One of the chemoreceptor cells is sensitive to host-plant compounds, stimulating oviposition. Non-host-plant (carrot) leaf extracts and sucrose did not stimulate any of the receptor cells. Direct contacts between sensory cell somata were observed, and the possibility of peripheral neural interaction at the sensillum level is discussed.

Functional anatomy of female sex pheromone gland of Mayetiola destructor Say (Diptera: Cecidomyiidae)

FUNCTIONAL ANATOMY OF FEMALE SEX PHEROMONE GLAND OF MAYETIOLA DESTRUCTOR SAY (DIPTERA: CECIDOMYIIDAE) The Hessian Fly (Mayetiola destructor Say, Diptera Cecidomyiidae) sex calling of males by females, known from long ago, has been recently demonstrated of being mediated by a female produced sex pheromone that has been chemically identified lately. Following the investigation methods previously applied to study sex pheromone glands in other Cecidomyiidae species (i.e., Allocontarinia sorghicola (Coq.) Solinas and Dasineura brassicae Winn.), the female sex pheromone gland of the Hessian Fly has been identified through functional-anatomy, ultrastructural, and physiological observations here reported. The pheromone gland consists of the 8th-9th abdominal intersegmental membrane transformed epidermis. This appears quite different in virgin than mated females being in the former strongly hypertrophied and obviously atrophied in the latter. Key words (in addition to those in title): Gross anatomy, histology, insect, midge, ovipositor, physiology, ultrastructure. ANATOMIA FUNZIONALE DELLA GHIANDOLA A FEROMONI SESSUALI DI MAYETIOLA DESTRUCTOR SAY (DIPTERA: CECIDOMYIIDAE) Il richiamo sessuale dei maschi da parte delle femmine della Cecidomia distruttrice del grano (Mayetiola destructor Say, Diptera Cecidomyiidae), noto da lungo tempo, e stato recentemente dimostrato esser mediato da un feromone sessuale il cui composto principale e stato anche chimicamente identificato ultimamente. Seguendo lo stesso metodo messo a punto dagli stessi autori per lo studio delle ghiandole a feromoni di altre cecidomie (Allocontarinia sorghicola (Coq.) Solinas e Dasineura brassicae Winn.), e stata identificata la ghiandola a feromoni sessuali della Cecidomia distruttrice del grano, mediante indagini anatomo-funzionali, ultrastrutturistiche e fisiologiche qui riportate. Detta ghiandola a feromoni risulta costituita dall’epidermide trasformata della membrana intersegmentale tra 8° e 9° urite, la quale si presenta fortemente ipertrofica nelle femmine vergini sessualmente mature, mentre si riduce bruscamente di volume e si atrofizza in seguito all’accoppiamento.

Antennal sensilla of Anagrus atomus (L.) (Hymenoptera: Mymaridae) female and their possible behavioural significance

The antennae of a hymenopteran Mymaridae female, Anagrus atomus (L.), have been investigated, through light microscopy as well as through scanning for the first time, and transmission electron microscopy, principally aiming at identification of sensory structures possibly involved in reproductive behaviour. Topographic distribution of the external components (cuticular appendages) of sensilla has been illustrated through “camera lucida” semischematic diagrams of the whole antenna, and especially the club, together with scanning electron micrographs. Topographic location of the same sensilla internal (cellular) components has been shown in the antennal club through transmission electron micrographs from serial cross sections. Seven categories of sensory structures have been identified (i.e., “apical sensilla”, “grooved peg sensilla”, “sensilla trichodea Type 1”, “sensilla trichodea Type 2”, “sensory ridges”, “sunken peg sensilla”, “tactile sensilla”) and illustrated through semischematic diagrams and transmission electron micrographs from fine serial sections. On the basis of the nature of the sensilla and their location on the antennae, together with antennal use during the female reproductive behaviour, the behavioural meaning of the above mentioned sensilla has been hypothesised. INDEX DESCRIPTORS (in addition to those in the title): contact chemoreceptor, olfactory sensilla, reproductive behaviour, sensory neurones, sheath cells, ultrastructure. SENSILLI ANTENNALI DELLA FEMMINA DI anagrus atomus (L.) (HYMENOPTERA: MYMARIDAE) E RELATIVO PROBABILE SIGNIFICATO COMPORTAMENTALE Le antenne della femmina di un imenottero Mymaridae, Anagrus atomus, vengono studiate in microscopia ottica ed elettronica a scansione e, per la prima volta, a trasmissione, principalmente al fine di identificarne le strutture sensoriali presumibilmente impegnate nel comportamento riproduttivo della specie. La distribuzione topografica degli elementi esterni (appendici cuticolari) dei sensilli viene illustrata con disegni semischematici dell’antenna intera e della clava in particolare, effettuati al microscopio ottico con camera lucida, unitamente a micrografie elettroniche a scansione. La localizzazione topografica delle parti interne (componenti cellulari) degli stessi sensilli viene evidenziata nella clava mediante micrografie elettroniche a trasmissione di sezioni fini trasversali seriate. Sette categorie di sensilli vengono cosi identificate (“apical sensilla”, “grooved peg sensilla”, “sensilla trichodea Type 1”, “sensilla trichodea Type 2”, “sensory ridges”, “sunken peg sensilla”, “tactile sensilla”) ed illustrate con disegni semischematici riassuntivi e con micrografie elettroniche a trasmissione di sezioni fini seriate. Sulla base della natura dei sensilli e della loro posizione sull’antenna, unitamente al portamento delle antenne medesime durante il comportamento riproduttivo della femmina, viene ipotizzato il significato comportamentale dei sensilli in questione. Parole chiave: cellule avvolgenti, comportamento riproduttivo, neuroni sensoriali, sensilli gustativi, sensilli olfattivi, ultrastruttura.

Comparative behavioural and anatomo-pathological investigations on Musca domestica L. adults treated with a new strain of Bacillus sp. close related to B. Thuringiensis (Berliner)

Comparative behavioural bioassays and anatomo-pathological investigations have been carried out on Musca domestica adults to test insecticidal activity of a new isolate of Bacillus sp. (characterization in course) close related to B. thuringiensis (Berliner). Both behavioural bioassays and anatomo-pathological tests, parallel the results previously reported for many other insects similarly treated with different strains of the well known B. thuringiensis. Flies fed on a suspension of a Bacillus sp. new isolate sporulated culture, display progressive sluggish and shaky behaviour, decreased responsiveness to external stimuli, gradual feeding inhibition, and general paralysis, until they die (over 52% within 72 hrs, and almost all specimens within 4-5 days, after treatment). Anatomo-histological and ultrastructural investigations corroborate the results from behavioural bioassays, proving that flies treated with Bacillus sp. undergo progressive degeneration (up to rupture) of midgut and malpighian tubules’ epithelial cells, as well as of the midgut muscular sheath, as reported for other insect species treated with B. thuringiensis. Comparative tests on M. domestica adults treated with analogous suspension of B. th. var. kurstaki (HD-1) gave rather negative results. Key words: behavioural bioassays, electron microscopy, gut anatomy, insecticidal activity, midgut histology, light microscopy. RICERCHE COMPORTAMENTALI ED ANATOMO-PATOLOGICHE SU ADULTI DI MUSCA DOMESTICA L. TRATTATI CON UN NUOVO ISOLATO DI BACILLUS SP. AFFINE AL B. THURINGIENSIS (BERLINER). Biosaggi comportamentali e indagini anatomo-patologiche sono state parallelamente condotte su adulti di Musca domestica L. per provare l’attivita insetticida di un nuovo isolato di Bacillus sp. (attualmente in via di caratterizzazione), affine al rinomato Bacillus thuringiensis (Berliner). Sia le prove comportamentali che quelle anatomo-istologiche ed ultrastrutturistiche hanno dato risultati simili a quelli riportati in letteratura per vari altri insetti trattati analogamente con diverse varieta di B. thuringiensis. Mosche alimentate con una sospensione della coltura sporulata di Bacillus sp. vanno incontro progressivamente a intorpidimento generale e tremore, ridotta sensibilita a stimoli esterni, graduale rifiuto del cibo e paralisi generale, fino alla morte (oltre 52% delle mosche muoiono entro 72 ore, e quasi tutte in 4-5 giorni dalla prima somministrazione della sospensione batterica). Le osservazioni anatomo-istologiche ed ultrastrutturistiche corroborano i risultati dei biosaggi comportamentali, evidenziando nelle mosche trattate col nuovo isolato di Bacillus sp. una progressiva degenerazione delle cellule epiteliali del mesentero e dei tubi malpighiani, come pure della tunica muscolare del mesentero, come e stato visto per altri insetti trattati con B. thuringiensis (Berliner). Prove di confronto con adulti di M. domestica analogamente trattati con una sospensione di B. th var. kurstaki (HD-1) hanno dato risultati sostanzialmente negativi. Parole chiave: anatomia intestinale, attivita insetticida, biosaggi comportamentali, istologia