National Repository of Grey Literature 15 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Biology of the soldier caste in the termite genus Prorhinoterme (Isoptera: Rhinotermitidae)
Hanus, Robert ; Štys, Pavel (advisor) ; Žďárek, Jan (referee) ; Korb, Judith (referee)
Ontogeny of soldiers in Prorhinotermes simplex The soldiers were found to develop from larvae of the second up to the eighth instar, via a short (13-17 days) presoldier stage. The early soldier instars were found exclusively in incipient colonies while the mature colony contained late instar soldiers only. The first soldiers occur early in the incipient colonies; as soon as one year a er the establishment of these colonies a high proportion of soldiers was observed, which is comparable to that in mature colonies. The abrupt change in the external anatomy occurs in two steps. During the larva-presoldier moult, the head increases in length but only slightly in width. During the presoldier-soldier moult, both the length and width of the head increase markedly and the typical cordate shape is attained; the relative size of the pronotum increases considerably. The long falcate mandibles develop mainly during the larva-presoldier moult. One antennal segment is added during these two moults. With increasing instar age of soldiers a relative increase of the pronotum and the head size in its posterior region was observed. No functional differences in external anatomy were found among the six soldier instars. The composition of the frontal gland secretion is similar in the six soldier instars, an...
Study of evolution of insect pheromone biosynthetic fatty acyl desaturases
Buček, Aleš ; Pichová, Iva (advisor) ; Žďárek, Jan (referee) ; Doležel, David (referee)
Insects account for more than one million of described species with an ecological and economic impact disproportional to their minute body size. Among the factors which have contributed to their evolutionary success, insect secondary metabolites such as defensive compounds and chemical signals are regarded to play a major role. This thesis aims at uncovering the molecular mechanisms underlying evolution of ubiquitous insect secondary metabolites - sex pheromones (SPs), i.e. chemical signals mediating mate finding and mating between individuals of the same species. The thesis focuses on a class of oxidoreductase enzymes, membrane fatty acid desaturases (mFADs), which introduce double bonds into hydrocarbon chains of fatty acyls and thus produce precursors of unsaturated fatty acid- derived SPs. mFADs are involved in SP biosynthesis in e.g. moths (Lepidoptera), flies (Diptera), cockroaches and termites (Blattodea), wasps and bees (Hymenoptera) - some of the most species-rich insect orders. Since SPs are principal to species reproductive isolation, uncovering the molecular basis of insect SP biosynthesis holds promises to contribute to answering fundamental questions concerning the insect ecology and evolution. The insect mFADs with diverse enzymatic specificities also represent a naturally available...
New case of mixed reproductive strategy and its adaptive significance in the neotropical termite Silvestritermes minutus (Termitidae: Syntermitinae)
Křivánek, Jan ; Hanus, Robert (advisor) ; Žďárek, Jan (referee)
Thanks to the progress in genetic methods in population ecology, many critical discoveries were recently made in the field of reproductive strategies of social insect. Among them is the description of mixed reproductive strategies, combining advantages of sexual reproduction with thelytokous parthenogenesis. The queens of such species produce sterile castes through classical sexual process from fertilized eggs, while future queens develop asexually from unfertilized eggs. This original breeding system was first described in several genera of ants, but it was found very recently, that it is not restricted to social Hymenoptera, since it has been identified also in the phylogenetically remote eusocial clade of termites. Switching between the sexual process and thelytokous parthenogenesis, now known as Asexual Queen Succession (AQS), which enables a continuity of genetically almost identical queen generations after the death of the founding primary queen, was first reported only in one genus of lower termites, i.e. Reticulitermes. Recently, our research group participated at the identification of AQS in four other species from two subfamilies in higher termites. One of these species is Silvestritermes minutus. This species is locally abundant in French Guiana and lives in small, well shaped nests on...
Hormonal regulation of behavioral manipulation in insects caused by parasites
Janů, Hana ; Jůzová, Kateřina (advisor) ; Žďárek, Jan (referee)
Number of scientific publications describing how parasites alter their host's behaviour providing them successful reproduction or transmission to other hosts has significantly increased during the last few decades. In recent years, more and more researchers are not only describing changes in the host organisms, but also trying to figure out mechanisms beyond these parasitic manipulations. Parasites can manipulate the host through neural and endocrine system using neuromodulators, immunomodulators, neurotransmitters and hormones. Either increase or decrease of hormone levels may cause changes of the infected hosts development, metabolism, reproduction and behaviour. Hosts, whose behaviour is altered via hormonal pathways are mostly developmentally arrested and their feeding and locomotion is terminated. Observed behavioral changes like hole digging or termination of participation in group work in insects demonstrably increase parazite's fitness. This thesis is a summary of behavioral manipulations of insects caused by changes in hormone levels.
Nesting behaviour and population genetics of solitary bees (Hymenoptera: Anthophila)
Černá, Kateřina ; Straka, Jakub (advisor) ; Žďárek, Jan (referee) ; Paxton, Robert J. (referee)
My thesis is focused on nesting behaviour and population genetics of solitary bees. These two topics, although seemingly unrelated, bring much new information and thus contribute to the better understanding of solitary bee biology that is still insufficiently known. Although the solitary behaviour represents the necessary original state for the evolution of higher sociality or obligate cleptoparasitism, its role is largely unappreciated. Furthermore, intraspecific cleptoparasitism, which is an alternative and facultative nesting strategy in bees, is a probable antecedent state of obligate cleptoparasitism. Although the obligate cleptoparasitism is a very common strategy in solitary bees, the information about the frequency and the occurrence of intraspecific cleptoparasitism in solitary bees is rare. We studied the nesting behaviour of solitary bees to detect different behavioural patterns that could serve as preadaptations to sociality or cleptoparasitic behaviour and we also focused on the detection and description of intraspecific cleptoparasitism in solitary bees. We chose four model solitary species for these studies - Andrena vaga (Andrenidae), Anthophora plumipes (Apidae), Colletes cunnicularius (Colletidae) and Osmia rufa (Megachilidae). We described the behaviour of Andrena vaga at the...
Study on dynamics of spinning apparatus of some wolf spiders (Araneae: Lycosidae) during their life cycle
Dolejš, Petr ; Smrž, Jaroslav (advisor) ; Žďárek, Jan (referee) ; Hajer, Jaromír (referee)
Current knowledge of the spinning apparatus comes namely from studies on orb web spiders and their relatives, whereas that of wolf spiders were more or less neglected. Therefore, developmental changes of the spinning apparatus of four wolf spiders were studied throughout their life cycles. Each of these lycosids possesses stenochronous life cycle with similar number of instars (7-10) but of different length (1-3 years). There is only one period of reproduction in spring/summer in all four species. Sperms are being formed just after the final moult; diplotene in some species is peculiar. The courtship behaviour reflects the microhabitat occupied by the concrete spider species; the copulations are species specific. Ontogeny of the spinning apparatus of developing spiderlings was observed: The spinning apparatus initiate its function in the first instar. Secondary ampullate, all piriform and all but four aciniform glands are tartipore-accommodated; they do not moult in situ. The tartipores, vestigial structures corresponding to spigots of the previous instar, appear on the spinning field starting with the second instar. Tartipore-accommodated glands play roles also during proecdysis and their evolution corresponds with the way how do the spiders secure themselves when moulting. Hence, the not yet...
Ecology and courtship behaviour of the wolf spider genus Alopecosa (Araneae: Lycosidae)
Just, Pavel ; Dolejš, Petr (advisor) ; Žďárek, Jan (referee)
In my bachelor thesis, Czech members of the wolf spider genus Alopecosa are discussed. Literature review summarizes our knowledge in ecology of wolf spiders, their life histories, phenology and habitat preference. I concentrated on reproduction of wolf spiders of the genus Alopecosa, especially on their courtship behavior. Recently, spider courtship is studied with focus on multimodal signalling. The review also contains remarks about spiders life cycles, copulation and parental care. Research of courtship of the genus Alopecosa is sligthly neglected, especially when we consider achievements gained by study of the American wolf spiders of the genus Schizocosa. It is necessary to know the taxonomy of the genus Alopecosa, thus some taxonomical remarks about current systematics and phylogeny of family Lycosidae are outlined
Mimetic complex of Central European red-and-black bugs (Heteroptera)
Hotová Svádová, Kateřina ; Exnerová, Alice (advisor) ; Žďárek, Jan (referee) ; Krištín, Anton (referee)
Aposematic animals signal to the predators their unprofitability (e.g. unpalatability, toxicity) Predators have either innate bias against warning signals or they have to learn to avoid aposematic prey. Aposematic species with similar warning signals profit from their resemblance and form mimetic complexes. Theoretically, there are five types of mimetic relations between species within the mimetic complex: Batesian, quasi-Batesian, quasi- Müllerian, Müllerian and super-Müllerian. Classification of mimetic relations depends on the level of mutual resemblance, and presence, type and efficiency of defensive mechanisms. Central European red-and-black true bugs (Heteroptera) were used as a model of mimetic complex in my Ph.D. thesis. We used six species of passerine birds. The species differ in body size, preferred food and reactions toward aposematic red-and-black prey and non- aposematic brown-painted prey. Although the diet of some passerine birds may include true bugs, there is evidence that birds mostly avoid aposematic species. In the first paper included in the thesis, we found that mimetic complexes may be predator dependent. There are differences in the extent of Batesian-Müllerian mimetic complexes and in the relations among the species involved. In the second paper, we analysed reactions of...
Delayed effects of a dipteran oostatic hormone on reproduction in the Tsetse fly
Žďárek, Jan ; Hlaváček, Jan ; Takáč, P.
Long-time delivery of the oostatic pentapeptide H-Tyr-Asp-Pro-Ala-Pro-OH decreased a fertility in the long-lived tse-tse fly G. Morsitans.

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