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Maternal Care in Spiders
Foxová, Doris ; Opatová, Věra (advisor) ; Raška, Jan (referee)
Maternal care is any behaviour of the mother which directly benefits its offspring usually at the cost of future reproduction of the female. Many types of maternal care are known among spiders, but a comprehensive review of all different types of maternal care across spider diversity is still largely missing. With the summarisation of research concerning maternal care and thanks to the implementation of genomic data and subsequent advances in spider systematics and evolutionary research, different types of maternal care are interpreted in an evolutionary context and mapped on the up to date phylogenetic tree. Guarding behaviour is common across spider families. On the contrary, various forms of feeding are rare. Some phenomena (matriphagy and regurgitation) evolved repeatedly in distantly related spider families.
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Does phylogenetic proximity positively correlates with the likelihood of an evolutionary origin of mimicry?
Kováčová, Katarína ; Kleisner, Karel (advisor) ; Raška, Jan (referee)
Mimicry represents a diverse group of similarities, which belongs to the phenomena of evolutionary biology. Even though mimicry is often interpreted as a convincing exam- ple of natural selection, it is necessary to consider the morphological and organizational processes that are responsible for the formation of organisms. In our work, we tested the hypothesis that mimicry occurs more frequently among insect genus that are phylogenet- ically closer than those that are phylogenetically more distant. To elaborate the work, we used 112 genus from the Insecta and Arachnida classes. The hypothesis was tested glob- ally, continentally and at the order level. Our hypothesis has not been refuted in Central and South America, Asia and Australia. At the order level, it was not contradicted in the order of Lepidoptera. We hypothesize that the explanation can be deduced from radical phenotypic changes that would ultimately disadvantage the given organism. 1
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Predators and antipredator defence of Auchenorrhyncha (Hemiptera)
Zeman, Šimon ; Raška, Jan (advisor) ; Michalko, Radek (referee)
Auchenorrhyncha are one of the species-richest groups of hemimetabolous insects. They feed mostly on plant sap and play an important role in food webs of various ecosystems; for humans, they are important mainly as pests of several crops. Because of their occurrence in many habitats, they are often preyed upon by number of predators, including both vertebrates and invertebrates. However, Auchenorrhyncha implement various anti-predator defences to avoid it. This thesis summarizes available information about predation of Auchenorrhyncha and shortly deals with hunting behaviour of selected predators. In the second part, anti-predatory strategies and their occurrence in different Auchenorrhyncha groups are summarized. Furthermore, potential predators affected by those defences are discussed.
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Spiders as senders and receivers of antipredatory warning signals
Raška, Jan ; Exnerová, Alice (advisor) ; Korenko, Stanislav (referee) ; Krištín, Anton (referee)
The introductory part of this thesis sums up the state of knowledge on aposematism and mimicry, the effect of aposematic and mimetic signals on spider predators, and cases when spiders do not receive but send such signals. Attachments of the thesis include four original manuscripts. In the first study, we presented jumping spiders (Evarcha arcuata, Salticidae) with different colour forms (red-and-black, yellow-and-black, white-and-black) of the firebug (Pyrrhocoris apterus, Pyrrhocoridae). Our goal was to compare reactions of the spiders to various intensity of aposematic signalization, expecting red-and-black coloration to have the strongest effect. Aversive learning of all colour forms was equally effective, but generalization of the learned avoidance to other colour forms was more effective after switch from less (white-and-black, yellow-and-black) to more (red-and-black) conspicuously coloured prey. When tested the next day, avoidance of the white-and-black prey got mostly forgotten. In the second study, we assessed little studied sensitivity of spiders to smells of unpalatable prey. After jumping spiders learned to avoid firebugs, most of them avoided the firebug smell, showing their sensitivity not only to optical, but also to chemical part of signalization of the unpalatable prey. In the...
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Mimicry in hoverflies
Daňková, Klára ; Hadrava, Jiří (advisor) ; Raška, Jan (referee)
Batesian mimicry, the imitation of harmful species manifested by harmless ones, could bring a lower risk of predation to the mimetic species. Therefore, it occurs in many different taxa. Hoverflies (Diptera: Syrphidae) could stand for one of the most various mimics. This worldwide-distributed family is known for taking shape of many Aculeata species using plenty of different adaptation connected with colouration, morphology and even behaviour. The aim of this work is to review the diversity of mimicry in Syrphidae, highlight the main selection pressures and to put forward a potential field of future research. Hoverflies are being studied for the last two hundred years. However, just several study approaches are dominating the field. In order to open a new chapter of their research, I bring a wider synthesis of knowledge related to the ecological and evolutionary context of this phenomenon.
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Spiders as senders and receivers of antipredatory warning signals
Raška, Jan
The introductory part of this thesis sums up the state of knowledge on aposematism and mimicry, the effect of aposematic and mimetic signals on spider predators, and cases when spiders do not receive but send such signals. Attachments of the thesis include four original manuscripts. In the first study, we presented jumping spiders (Evarcha arcuata, Salticidae) with different colour forms (red-and-black, yellow-and-black, white-and-black) of the firebug (Pyrrhocoris apterus, Pyrrhocoridae). Our goal was to compare reactions of the spiders to various intensity of aposematic signalization, expecting red-and-black coloration to have the strongest effect. Aversive learning of all colour forms was equally effective, but generalization of the learned avoidance to other colour forms was more effective after switch from less (white-and-black, yellow-and-black) to more (red-and-black) conspicuously coloured prey. When tested the next day, avoidance of the white-and-black prey got mostly forgotten. In the second study, we assessed little studied sensitivity of spiders to smells of unpalatable prey. After jumping spiders learned to avoid firebugs, most of them avoided the firebug smell, showing their sensitivity not only to optical, but also to chemical part of signalization of the unpalatable prey. In the...
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Spiders as senders and receivers of antipredatory warning signals
Raška, Jan
The introductory part of this thesis sums up the state of knowledge on aposematism and mimicry, the effect of aposematic and mimetic signals on spider predators, and cases when spiders do not receive but send such signals. Attachments of the thesis include four original manuscripts. In the first study, we presented jumping spiders (Evarcha arcuata, Salticidae) with different colour forms (red-and-black, yellow-and-black, white-and-black) of the firebug (Pyrrhocoris apterus, Pyrrhocoridae). Our goal was to compare reactions of the spiders to various intensity of aposematic signalization, expecting red-and-black coloration to have the strongest effect. Aversive learning of all colour forms was equally effective, but generalization of the learned avoidance to other colour forms was more effective after switch from less (white-and-black, yellow-and-black) to more (red-and-black) conspicuously coloured prey. When tested the next day, avoidance of the white-and-black prey got mostly forgotten. In the second study, we assessed little studied sensitivity of spiders to smells of unpalatable prey. After jumping spiders learned to avoid firebugs, most of them avoided the firebug smell, showing their sensitivity not only to optical, but also to chemical part of signalization of the unpalatable prey. In the...
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Spiders as senders and receivers of antipredatory warning signals
Raška, Jan ; Exnerová, Alice (advisor) ; Korenko, Stanislav (referee) ; Krištín, Anton (referee)
The introductory part of this thesis sums up the state of knowledge on aposematism and mimicry, the effect of aposematic and mimetic signals on spider predators, and cases when spiders do not receive but send such signals. Attachments of the thesis include four original manuscripts. In the first study, we presented jumping spiders (Evarcha arcuata, Salticidae) with different colour forms (red-and-black, yellow-and-black, white-and-black) of the firebug (Pyrrhocoris apterus, Pyrrhocoridae). Our goal was to compare reactions of the spiders to various intensity of aposematic signalization, expecting red-and-black coloration to have the strongest effect. Aversive learning of all colour forms was equally effective, but generalization of the learned avoidance to other colour forms was more effective after switch from less (white-and-black, yellow-and-black) to more (red-and-black) conspicuously coloured prey. When tested the next day, avoidance of the white-and-black prey got mostly forgotten. In the second study, we assessed little studied sensitivity of spiders to smells of unpalatable prey. After jumping spiders learned to avoid firebugs, most of them avoided the firebug smell, showing their sensitivity not only to optical, but also to chemical part of signalization of the unpalatable prey. In the...
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Verification and numerical simulation of advanced composite inlet in compliance of airworthiness impact requirements
Doubrava, Radek ; Oberthor, Martin ; Raška, Jan ; Bělský, Petr ; Doubrava, Karel ; Dvořák, Milan
Bird or hail stone strikes are an important phenomenon which must be considered during aircraft design. Most of major bird or hail strike incidents result from engine ingestion. As engines are the sole thrust providing mechanisms of an aircraft, it is critical to investigate and mitigate the effects of bird or hail strikes on engine inlets and systems to the greatest extent possible. The article presents application of test verified numerical simulation for design and full-scale test verification of advanced composite air inlet for new generation of jet trainer aircraft from point of view of high speed impact resistance. The physical bird and hail impact tests were performed at the Czech Aerospace Research Centre (VZLÚ) according to airworthiness requirements. The measurement during impact test were performed by high-speed camera, Fiber Bragg Grating (FGB) sensors and strain gauges in cooperation with Czech Technical University (CTU) in Prague. The results from full-scale bird and hail strike tests were compared with numerical simulation.
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Mimicry in hoverflies
Daňková, Klára ; Hadrava, Jiří (advisor) ; Raška, Jan (referee)
Batesian mimicry, the imitation of harmful species manifested by harmless ones, could bring a lower risk of predation to the mimetic species. Therefore, it occurs in many different taxa. Hoverflies (Diptera: Syrphidae) could stand for one of the most various mimics. This worldwide-distributed family is known for taking shape of many Aculeata species using plenty of different adaptation connected with colouration, morphology and even behaviour. The aim of this work is to review the diversity of mimicry in Syrphidae, highlight the main selection pressures and to put forward a potential field of future research. Hoverflies are being studied for the last two hundred years. However, just several study approaches are dominating the field. In order to open a new chapter of their research, I bring a wider synthesis of knowledge related to the ecological and evolutionary context of this phenomenon.
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