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Evolution of sensitivity to trail-following pheromones in termites
Száková, Barbora ; Hanus, Robert (advisor) ; Sillam-Dussès, David (referee)
Eusocial insects evolved a sophisticated intraspecific communication, dominated by chemical signals, the pheromones. Termites (Isoptera) represent an excellent example in this respect, having a wide range of pheromones, such as trail-following, sex-pairing, alarm, and other pheromones. It is especially the former category of pheromones which is ubiquitous in termites and which was chemically characterized in many taxa across termite phylogeny. This allowed phylogenetic reconstruction of the chemical diversity of trail- following pheromones and calls for searching of evolutionary patterns of the sensitivity to these pheromones in various lineages across the tree of life, including the search for evolutionary scenario of the emergence of specific olfactory receptor proteins. In most species, the trail-following pheromones are represented by mono-, di- and tri-unsaturated fatty alcohols (3Z)-dodec-3-en-1-ol (DE), (3Z,6Z)-dodeca-3,6-dien-1-ol (DDE), and (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol (DTE). My overall aim in this thesis was to contribute to the understanding of the evolution of olfactory detection of C12 fatty alcohol trail-following pheromones in termites. More specifically, my question was whether evolutionarily more basal clades (Kalotermes flavicollis and Neotermes cubanus from the family...
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Methods of insect body and food marking and their utilization in bees (Anthophila)
Macháčková, Lenka ; Straka, Jakub (advisor) ; Bogusch, Petr (referee) ; Hanus, Robert (referee)
Marking methods represent often an essential part of many studies which target on insect biology. These marking techniques sometimes represent the only possible way to obtain new and important informations. In the first part of the thesis I deal with individual insect labeling, which was used for marking of solitary bees and their nests as a tool of obtaining informations about nesting bee dynamics in aggregation. Our study show that nest owner replacements are very common in all four species. However, a large percentage of the nests were abandoned by the female owners before owner change. Only a part of all the nests were trully usurped on the nesting site. The true usurpations thus represent rather minor part of observed nest owner replacement situations. The bees surprisingly often abandon their nests and found the new ones. The frequent contacts of the females on a nesting site occur as a result of common nest owner replacements. High tolerance of bees to each other together with tolerance of usurpations and low level of aggression may thus represent one of the possible ways towards communality and other types of social behaviour. In the second part of the thesis I focus on the possibilities of food marking in bees. Effectivity of sugar and pollen utilization are not yet fully understood in...
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Cell senescence with a focus on telomerase theory
Laštůvková, Viktorie ; Tlapáková, Tereza (advisor) ; Hanus, Robert (referee)
Cell senescence is an irreversible state in which the cell cycle ends. The cell remains metabolically active, but its physiological functions are limited. Cell cycle arrest is a response to the action of a number of factors, most of which affect the secondary structure of DNA in various ways and cause damage to it. Other initiators of cell entry into the senescent state are oncogenes and chemotherapeutics. One of the best studied factors, which is also in a way the "fairest", is the shortening of the telomere. Telomeres are non-coding regions of DNA at the chromosome ends that shorten slightly with each division of the cell. If the cell does not have mechanisms to compensate for this loss, the Hayflick limit is reached after a certain time. In general, senescence can be considered as a protective mechanism to prevent DNA damage pathologies. However, the presence of senescent cells in tissues is often ambivalent, accumulates with age, and can cause many degenerative diseases. The senescent phenotype includes a wide range of signs such as changes in cell size and shape, increased granularity, or altered range of expressed genes. A significant phenomenon of senescent cells is the secretion of biologically active factors contributing to physiological or pathological changes in the organism. Key words:...
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Reproductive strategy of the termite Silvestritermes minutus and its consequences for the life history and ecological succes
Křivánek, Jan ; Hanus, Robert (advisor) ; Klimeš, Petr (referee)
Mixed reproductive strategies are unique modes of reproduction, in which the organisms alternate sexual and asexual offspring production to benefit from both processes. In termites, such a strategy was first described in 2009 and dubbed Asexual Queen Succession (AQS). Reproduction in most termite species is based on a presence of one pair of long-lived reproductives, the primary king and queen, producing in a lifelong strict monogamy all other colony members using classical sexual processes. In a few rare species, the primary queen has been observed to be replaced at some stage of colony development by a harem of neotenic queens. These arise from unfertilized eggs via thelytokous parthenogenesis and reproduce with the founding king. While the workers, soldiers and winged dispersing reproductives remain to be produced sexually, new generations of parthenogenetic neotenic queens appear in the colony to supplement the harem. As long as the founding king is alive, the genetic constitution of most offspring remains identical as if the founding queen would still be alive, while the overall fecundity of the colony increases thanks to the large number of queens. At the same time, the continuous renewal of the harem by new parthenogens offers a virtually unlimited lifespan extension to the colony. In my...
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Physiological basis of extended longevity in termite kings and queens - is activation of telomerase mechanism linked with extended longevity of termites?
Pangrácová, Marie ; Hanus, Robert (advisor) ; Kodrík, Dalibor (referee)
- Extended longevity and high fecundity are two phenomena typical for reproductive castes (queens, eventually kings) of eusocial insects. In my thesis, we explore the hypothesis that the longevity of reproductives in the termite Prorhinotermes simplex is linked with the activation of the telomerase enzyme complex. Telomerase is well known for its life-extension functions, due especially to its capacity to prolong the telomeric ends of chromosomes. Therefore, we studied here the gene expression of: (1) the gene TERT coding for the catalytic subunit of the telomerase and (2) the genes of the main endocrine regulatory pathways, known to be responsible for the control of reproduction and longevity in insects. Expression dynamics of these genes were measured in sterile and reproductive castes of P. simplex during their development and sexual maturation. Based on our results obtained from the TERT expression analyses and their comparison with telomerase enzyme activities, we assume that the telomerase action in the long-lived reproductive individuals is regulated at a post-transcription level. Furthermore, we observed in reproductive castes a simultaneous upregulation of some transcription variants of vitellogenin and the genes for insulin signalling pathways. We can, therefore, conclude that in...
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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...
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Evolution of Olfaction in Mammals with Focus on Superorder Laurasiatheria
Vondráčková, Kamila ; Hulva, Pavel (advisor) ; Hanus, Robert (referee)
The evolution history of mammals is connected with the dominance of smell and olfactory communication, which are important sense and communication channels also in recent forms. Two systems are involved in detecting and processing the molecules of scent, the main and the accessory olfactory system. These systems distinguish different types of scents, odorants and pheromones, which are also detected by different types of receptors. Significant factors for comparison of the ability of smell between mammals are both the amount of olfactory genes and the size and complexity of olfactory structures. The main emphasis in this thesis is put on the sensory part of the olfactory system and hence there is effort to support characterization of particular taxa by genomic studies. The ability of smell, respectively amount and variation of olfactory gene repertoires has been formed during the evolution on different circumstances and the ecological adaptation played a great role. The amount and diversity of olfactory receptors vary a lot in mammals and range through anosmatic Cetaceans and microsmatic bats to macrosmatic carnivores. Present thesis is focused to the superorder Laurasiatheria because of its extensive ecological differentiation and diversification of smell abilities (from anosmatic to macrosmatic...
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The role of male external glands in sexual behaviour of insect
Dvořák, Tomáš ; Kotyková Varadínová, Zuzana (advisor) ; Hanus, Robert (referee)
The body of some insect's males is covered by glands, which females are interested in during or after courtship and copulation. Female can palpate this glands or feed on their secretion. My bachelor thesis describes these glands in five orders of insect, where they are known: Zygentoma, Zoraptera, Coleoptera and especially Orthoptera and Blattodea. In the introduction i describe briefly their histology, morphology and ontogeny. But the main part of the work deal with their ethological and ecological function. This glands have four main functions. They can serve to maneuver female into proper position and allow the male to clasp her genitalia. Another function is prolonging of copulation, which enable the male to transfer more sperm. Glands can also provide nutritious secret, through it the male directly affects the female fitness. The last function is simple signal of male quality, which through the production of secret demonstrates his good condition. The role of the glands is often uncertain and their functions are often overlaping.
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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...
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