Antennal sensilla of Metasyrphus venablesi (Cn.) and Eupeodes volucris 0.S. (Diptera: Syrphidae) were studied by scanning and transmission electron microscopy. Males and females both had four types of sensilla. Three of these, two multiporous perforated (MPP) sensilla (one round-tipped and one pointed), and a grooved peg, multiporous sen-sillum, were also confirmed by SEM on the following species: Syrphus torvus (♂, ♀) Scaeva pyrastri (♂, ♀), Dasysyrphus amalopsis (♀), Xantho- grarnma flavipes (♀), Brachyopa perplexa (♂), Pipiza sp. (♀), Xylota sp. (♂). The fourth MPP sensillum had thicker walls and fewer pores. All four types were located among dense non-innervated setae on the antennal bulb and appeared to be olfactory. EAG study of the antennae of female M. venablesi and E. volucris showed that both species responded to: common green plant volatiles, trans- and cis-2-hexen-1-ol, trans- and cis-3-hexen-1-ol, cis-3-hexenylacetate, and hexanol; other volatile plant substances, methylsal-icylate and amylacetate; crushed carnation petals and crushed aphids. There was no response to honeydew or some of its components (e.g. tryptophan, indolealdehyde or indoleacetaldehyde) nor was there a response to water vapour. A gustatory sensillum on the ovipositor of these two species was studied by scanning and transmission electron microscopy and by neuro-physiological methods. One mechanosensitive and four chemosensitive neurons innervate each hair. The chemosensitive neurons are exposed to the exterior by a terminal pore, and respond to honeydew, tryptophan, indoleacetaldehyde, alanine, sucrose, and water. Labellar hairs are also sensitive to sucrose. Olfactometer study of M. venablesi and E. volucris showed that olfactory stimulation by flowers would induce searching by both sexes. A mixture of tryptophan and indoleacetaldehyde induced mated females to search for and locate the stimulus. Other components of the oviposition stimulus - crushed plant, un infested plant, and aphids did not induce searching. Physiological condition of the insect affected response to aphid-infested plants. Mated females, previously exposed to the stimulus, were more responsive than mated, inexperienced females or unmated, previously exposed females. Unmated, inexperienced females were least responsive. Mated and previously exposed males were more responsive than unmated, inexperienced males. Elements of the oviposition stimulus were presented on green glass rods to mated females. The attractive elements included fresh dead aphids, honeydew, crushed bean, tryptophan and indoleacetaldehyde, and clusters of black spots similar in size to aphids. Males were attracted only to honeydew and crushed bean. Both sexes responded to potential food sources, such as honeydew, but only females responded to aphids and attractants that characterized oviposition sites. A stimulus-response sequence is proposed for these aphidophagous syrphids that involves dual and/or multiple stimulus combinations. / Land and Food Systems, Faculty of / Graduate

No description available.

Thesis (M. Ed.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 103-118).

No description available.

Diving muskrats (Ondatra zibethica) invoke a series of cardiovascular and respiratory adjustments in response to stimulation of the nares with water. This dive response is characterized by apnoea, a decrease in cardiac output and an increase in peripheral resistance. The result is that blood flow is maintained to those organs most susceptible to oxygen deprivation, the heart and the brain. The initiation of the dive response in mammals is primarily the result of nasal stimulation with water. In addition, the baroreceptors acting via the baroreflex have been suggested to be involved in either the initiation or the maintenance of this response. The chemoreceptors, acting via the chemoreflex, have also been implicated in the maintenance of the dive response, although the importance of this contribution is controversial. The purpose of this thesis was to examine the role of the baroreceptors and chemoreceptors in the diving response of the muskrat. Changes in input from these receptors recorded from the cut carotid sinus nerve and their modulation by the carotid sinus efferent activity during nasal stimulation may have important implications for the role of the baroreceptors and chemoreceptors in the diving response. In the initial part of the dive, baroreceptor activity decreased, while chemoreceptor activity did not change. Subsequently, baroreceptor and chemoreceptor activity increased, exceeding pre-dive levels. This increase was not due to a change in receptor threshold or sensitivity induced by the nasal stimulation, but was a reflection of the increase in the usual stimulus modality of both receptor groups. The efferent activity recorded from the central end of the cut carotid sinus nerve was of two types, both of which responded to nasal stimulation. This change in the efferent discharge has the potential to modify afferent activity. Nasal stimulation caused one type of efferent activity (type A) to stop. The second type of efferent activity (type B) responded with an initial increase in discharge, returning to pre-dive levels after 6.6 seconds. Based-on the similar characteristics of these efferents to those of previous work it is postulated that the actions of the efferents would be to inhibit the baroreceptors and chemoreceptors during the initiation of the nasal stimulation, but to be less effective as the dive progressed. It is concluded that there is no contribution from the baroreceptors to the initiation of the diving bradycardia, although the lack of baroreceptor activity may contribute to the increase in peripheral resistance. Later in the dive, both heart rate and arterial blood pressure increase, despite a concomitant elevation in baroreceptor activity. The baroreceptors therefore have no role in the maintenance of the diving response. The initial inhibition of the chemoreceptors may be important to permit the full expression of the dive response, including a decrease in central respiratory output. Later in the dive the chemoreceptors may contribute to the maintenance and termination of the diving response. / Science, Faculty of / Zoology, Department of / Graduate

Univ., Diss.--Göteborg, 2006. / Enth. außerdem 5 Zeitschriftenaufsätze.

Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references (leaves 194-236). Also available via World Wide Web.

Thesis (Ph. D.)--Georgia State University, 2007. / Title from file title page. Chun Jiang, committee chair; Delon Barfuss, Deborah Baro, Teryl Frey, committee members. Electronic text (226 p. : ill. (some col.)) : digital, PDF file. Description based on contents viewed Nov. 1, 2007. Includes bibliographical references (p. 210-226).

Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references (224-249 leaves). Also available via World Wide Web.

No description available.