Tomáš Ditrich | University of South Bohemia (original) (raw)

Papers by Tomáš Ditrich

Research paper thumbnail of Dispersal and Migration Patterns of Freshwater Semiaquatic Bugs

Insects

Semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha) are mostly wing-polymorphic species with f... more Semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha) are mostly wing-polymorphic species with flight dispersal as an important life history trait, but the specific flight ability and dispersal pattern remain unexplored in most species. This report presents the results of a long-term survey based on the individual marking of more than 23,000 specimens of eight water striders (Gerridae) and a water cricket Velia caprai (Veliidae). Three distinct lentic habitats were sampled (solitary fishponds, systems of nearby fishponds and systems of small, often temporary pools) and one lotic habitat—a small forest stream. Recaptures revealed that three gerrid species tend to stay at the breeding site, but can differ in dispersal via the water surface. Reproductive flightless females disperse most actively via the water surface, possibly bypassing the trade-off between dispersal and reproduction. One species has a sex-dependent dispersal pattern, with females being rather philopatric, whereas ma...

Research paper thumbnail of In memoriam of Professor Miroslav Papáček (1953–2019): biography, memories, bibliography and list of described taxa

Acta Entomologica Musei Nationalis Pragae

Professor Miroslav Papáček (1953–2019) was an eminent specialist in morphology, taxonomy, systema... more Professor Miroslav Papáček (1953–2019) was an eminent specialist in morphology, taxonomy, systematics, biology and ecology of aquatic and semiaquatic bugs (Hemiptera: Heteroptera: Nepomorpha, Gerromorpha). All his career was connected with the Department of Biology, Faculty of Education, University of South Bohemia in České Budějovice, Czech Republic. Here we provide his short biography, personal memories of his colleague, bibliography currently comprising 125 papers in zoology and 57 in didactics of biology, and an annotated list of the taxa he described, which includes one subfamily (Helotrephidae: Trephotomasinae), three genera, two subgenera and 41 species of Helotrephidae and Aphelocheiridae.

Research paper thumbnail of Climatic Variation of Supercooling Point in the Linden Bug Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)

Insects

Cold tolerance is often one of the key components of insect fitness, but the association between ... more Cold tolerance is often one of the key components of insect fitness, but the association between climatic conditions and supercooling capacity is poorly understood. We tested 16 lines originating from geographically different populations of the linden bug Pyrrhocoris apterus for their cold tolerance, determined as the supercooling point (SCP). The supercooling point was generally well explained by the climatic conditions of the population’s origin, as the best predictor—winter minimum temperature—explained 85% of the average SCP variation between populations. The supercooling capacity of P. apterus is strongly correlated with climatic conditions, which support the usage of SCP as an appropriate metric of cold tolerance in this species.

Research paper thumbnail of Efektivita badatelsky orientovaného vyučování na primárním stupni základních škol v přírodovědném vzdělávání v České republice s využitím prostředí školních zahrad

Scientia in educatione

Článek je zaměřen na průzkum účinnosti vyučovacích metod s prvky badatelsky orientovaného vyučová... more Článek je zaměřen na průzkum účinnosti vyučovacích metod s prvky badatelsky orientovaného vyučování (BOV) ve vazbě na prostředí školních zahrad na primárním stupni základních škol v České republice. Data byla získávána na základě metody experimentu typu spárovaných skupin. V rámci výzkumu opakovaně participovalo v experimentální skupině 73–75 žáků a ve skupině kontrolní 70–72 žáků ze čtvrté třídy. Získané výsledky poukazují na fakt, že badatelsky orientované vyučování má statisticky prokazatelný vliv na osvojování nových znalostí a na vzrůstající oblíbenost výuky přírodovědy u žáků na primárním stupni základních škol. Z dílčích výsledků je patrné, že pro větší efektivitu badatelsky orientovaných metod výuky musí dojít k jejich opakovanému zařazování do vyučování. V opačném případě se žákům BOV jeví jako složitě uchopitelné a příliš abstraktní.

Research paper thumbnail of The latitudinal uniformity of the unique life history of Velia caprai (Heteroptera: Veliidae) and notes to the pre-overwintering period of selected water striders (Heteroptera: Gerridae)

Entomologica Fennica

Temperate water striders (Gerridae) overwinter as adults and die after spring reproduction. Europ... more Temperate water striders (Gerridae) overwinter as adults and die after spring reproduction. European water cricket Velia caprai (Veliidae) overwinters concurrently in egg and adult stage in Central Europe. This rare overwintering strategy goes with longevity ofthis species. Adults can survive two winters in Central Europe, unlike other semiaquatic bugs. Scandinavian populations of V. caprai and water striders Gerris lacustris and G. lateralis were examined at the beginning and end of September to determine their life histories. Both gerrids start to overwinter during September, females prior to males and macropterous individuals prior to brachypterous. All females of G. lacustris and G. lateralis enter reproductive diapause before winter. V. caprai overwinters in both adult and egg stage in Norway, and can probably survive two winters. Central European and Scandinavian populations of V. caprai share the same unusual way of overwintering and probably also the whole life history.

Research paper thumbnail of Supercooling point is an individually fixed metric of cold tolerance in Pyrrhocoris apterus

Journal of Thermal Biology

Research paper thumbnail of Efficiency of subaquatic light traps

Research paper thumbnail of Relative male and female contributions to the supercooling point of their offspring inMicrovelia reticulata(Heteroptera: Veliidae)

Entomological Science, 2016

Cold hardiness is a key life history trait in temperate and polar ectothermic species, as it affe... more Cold hardiness is a key life history trait in temperate and polar ectothermic species, as it affects survival during overwintering, but its evolution is poorly understood. While many studies of cold hardiness in insects have shown differences between species, populations or developmental stages, data on the relative contribution of individual genotypes to cold hardiness are scarce and mainly limited to drosophilid fly species. We used a sib-analysis (paternal half-sib/full-sib breeding design) to estimate the relative contributions of parental generation to the supercooling point (SCP) of the offspring of a heteropteran non-model insect species, Microvelia reticulata (Heteroptera: Gerromorpha: Veliidae). We found that parent identity affected significantly SCP values of their offspring. Magnitudes of estimated sire and dam variance components were similar but the distributions of individual contributions to SCP differed between sires and dams, which points to sex-specific genetic or parental effects on SCP in this species. The animal model failed to find a realistic estimate of heritability (h 2) of SCP, suggesting that the underlying genetics of SCP in M. reticulata can not be characterized by purely additive effects.

Research paper thumbnail of Differences in prey capture in semiaquatic bugs (Heteroptera: Gerromorpha)

Entomological Science, 2016

Feeding behavior has been investigated several times in different semiaquatic bugs (Heteroptera: ... more Feeding behavior has been investigated several times in different semiaquatic bugs (Heteroptera: Gerromorpha), but has never been directly compared between species from lentic and lotic habitats and different families. Time required to capture prey was investigated in five gerromorphan species: Aquarius paludum, Gerris lacustris, G. odontogaster (Gerridae), Velia caprai and V. gridellii (Veliidae). This experiment used live and dead prey and intact and artificially blinded bugs. The presence of vibrational stimuli (live prey) significantly decreased latency to capture prey in all species except G. odontogaster. This species was the only one where visual stimuli affected the response significantly (only with dead prey). Latency to capture in Velia spp. was significantly shorter than that in the three gerrid species. Capture efficiency differed significantly between Gerris and Velia spp.; both Velia species carried out unsuccessful attack attempts less frequently than did the Gerris species. Prey capture was quicker in treatments with live prey and/or intact bugs. No difference in capture efficiency was found between sexes. Aquarius and Gerris species from predominantly lentic habitats needed more time to capture prey than did Velia species, which live mostly in streams. This difference in feeding behavior can probably allow coexistence of gerrids and veliids at sites where their occurrence overlaps.

Research paper thumbnail of Note to the effect of environmental conditions on the occurrence of benthic water bug Aphelocheirus aestivalis (Heteroptera: Aphelocheiridae)

Communications and Abstracts …

The aim of this study was to find out what abiotic environmental variables are related to the occ... more The aim of this study was to find out what abiotic environmental variables are related to the occurrence of benthic water bug Aphelocheirus aestivalis. Samples and abiotic environmental data sets obtained by extensive monitoring of Labe, Vltava and Danube river basis were sorted and analysed by Redundancy analysis (RDA). Results of RDA did not offer transparent response on our question. The reason is probably too rough scaling of environmental variables used commonly by hydrobiologist for monitoring of benthos in running waters. More detailed design of fieldwork is probably necessary for a better solution of question mentioned above.

Research paper thumbnail of Distribution of Gerris asper and G. lateralis (Hemiptera: Heteroptera: Gerridae) in the Czech Republic

All the available published and unpublished distributional records of two endangered pond skaters... more All the available published and unpublished distributional records of two endangered pond skaters, Gerris asper (Fieber, 1860) and Gerris lateralis Schummel, 1832 (Hemiptera: Heteroptera: Gerridae) in the Czech Republic are summarized and mapped. Gerris asper was originally described from Bohemia by Fieber (1860) without any exact locality and we have been unable to confirm its occurrence with any subsequently collected specimen. The distribution of G. asper in the Czech Republic thus seems to be limited to southern and central Moravia, with a single new record from northern Moravia, where it was found syntopically with G. lateralis. Gerris lateralis is widespread in Bohemia and a new species for Moravia, where it was collected on two sites in the north of the territory (the Czech Silesia). General distribution, biology and ecology of both species are reviewed and summarized.

Research paper thumbnail of Analyses of Developmental Rate Isomorphy in Ectotherms: Introducing the Dirichlet Regression

Temperature drives development in insects and other ectotherms because their metabolic rate and g... more Temperature drives development in insects and other ectotherms because their metabolic rate and growth depends directly on thermal conditions. However, relative durations of successive ontogenetic stages often remain nearly constant across a substantial range of temperatures. This pattern, termed 'developmental rate isomorphy' (DRI) in insects, appears to be widespread and reported departures from DRI are generally very small. We show that these conclusions may be due to the caveats hidden in the statistical methods currently used to study DRI. Because the DRI concept is inherently based on proportional data, we propose that Dirichlet regression applied to individual-level data is an appropriate statistical method to critically assess DRI. As a case study we analyze data on five aquatic and four terrestrial insect species. We find that results obtained by Dirichlet regression are consistent with DRI violation in at least eight of the studied species, although standard analysis detects significant departure from DRI in only four of them. Moreover, the departures from DRI detected by Dirichlet regression are consistently much larger than previously reported. The proposed framework can also be used to infer whether observed departures from DRI reflect life history adaptations to size-or stage-dependent effects of varying temperature. Our results indicate that the concept of DRI in insects and other ectotherms should be critically re-evaluated and put in a wider context, including the concept of 'equiproportional development' developed for copepods.

Research paper thumbnail of Differences in prey capture in semiaquatic bugs (Heteroptera: Gerromorpha

Feeding behavior has been investigated several times in different semiaquatic bugs (Heteroptera: ... more Feeding behavior has been investigated several times in different semiaquatic bugs (Heteroptera: Gerromorpha), but has never been directly compared between species from lentic and lotic habitats and different families. Time required to capture prey was investigated in five gerromorphan species: Aquarius paludum, Gerris lacustris, G. odontogaster (Gerridae), Velia caprai and V. gridellii (Veliidae). This experiment used live and dead prey and intact and artificially blinded bugs. The presence of vibrational stimuli (live prey) significantly decreased latency to capture prey in all species except G. odontogaster. This species was the only one where visual stimuli affected the response significantly (only with dead prey). Latency to capture in Velia spp. was significantly shorter than that in the three gerrid species. Capture efficiency differed significantly between Gerris and Velia spp.; both Velia species carried out unsuccessful attack attempts less frequently than did the Gerris species. Prey capture was quicker in treatments with live prey and/or intact bugs. No difference in capture efficiency was found between sexes. Aquarius and Gerris species from predominantly lentic habitats needed more time to capture prey than did Velia species, which live mostly in streams. This difference in feeding behavior can probably allow coexistence of gerrids and veliids at sites where their occurrence overlaps.

Research paper thumbnail of Relative male and female contributions to the supercooling point of their offspring in Microvelia reticulata (Heteroptera: Veliidae

Cold hardiness is a key life history trait in temperate and polar ectothermic species, as it affe... more Cold hardiness is a key life history trait in temperate and polar ectothermic species, as it affects survival during overwintering, but its evolution is poorly understood. While many studies of cold hardiness in insects have shown differences between species, populations or developmental stages, data on the relative contribution of individual genotypes to cold hardiness are scarce and mainly limited to drosophilid fly species. We used a sib-analysis (paternal half-sib/full-sib breeding design) to estimate the relative contributions of parental generation to the supercooling point (SCP) of the offspring of a heteropteran non-model insect species, Microvelia reticulata (Heteroptera: Gerromorpha: Veliidae). We found that parent identity affected significantly SCP values of their offspring. Magnitudes of estimated sire and dam variance components were similar but the distributions of individual contributions to SCP differed between sires and dams, which points to sex-specific genetic or parental effects on SCP in this species. The animal model failed to find a realistic estimate of heritability (h 2) of SCP, suggesting that the underlying genetics of SCP in M. reticulata can not be characterized by purely additive effects.

Research paper thumbnail of Effect of population density on the development of Mesovelia furcata (Mesoveliidae), Microvelia reticulata and Velia caprai (Veliidae) (Heteroptera: Gerromorpha)

Population density during nymphal development affects body size, developmental rate and wing poly... more Population density during nymphal development affects body size, developmental rate and wing polymorphism in semiaquatic bugs. Nymphs from crowded habitats grow faster and thus gain an advantage in the later stadia. Rapid development results in smaller body size in several gerrids. Macropterous adults develop more frequently at high population densities in most species, which enables the bugs to leave crowded habitats. Three European widespread species Mesovelia furcata Mulsant & Rey, 1852 (Mesoveliidae), Microvelia reticulata Burmeister, 1835 and Velia caprai Tamanini, 1947 (Veliidae) were reared individually and simultaneously either at a low or high population density. Duration of postembryonic development, wing morph, body size and length of distal oocyte in females were recorded. High population density accelerates development in Mesovelia furcata and Microvelia reticulata. However, there was no trade-off between developmental rate and body size. Accelerated development without a decrease in body size was probably because maturation was delayed. Individually reared nymphs developed faster than nymphs from communal cohorts. No long-winged Microvelia reticulata specimen developed in any treatment. However, more macropterous individuals developed in high-density treatments in Mesovelia furcata (significant) and Velia caprai (not significant). All the nymphs of the species that were reared individually developed into apterous adults. The results suggest that population density strongly influences the life history of semiaquatic bugs. However, the only commonly shared response seems to be an increase in developmental rate when reared at high population densities. Other traits such as wing dimorphism, body size and rate of oogenesis differ at the species level.

Research paper thumbnail of Comparative analysis of overwintering physiology in nine species of semi-aquatic bugs (Heteroptera: Gerromorpha)

Physiological Entomology, 2011

In semi-aquatic bugs (Heteroptera: Gerromorpha), the strategies of overwintering in a cryothermic... more In semi-aquatic bugs (Heteroptera: Gerromorpha), the strategies of overwintering in a cryothermic state (i.e. at body temperatures below the equilibrium freezing point) remain largely unexplored. The present study provides an analysis of the ecophysiological aspects of overwintering in nine gerromorphan species. All nine species avoid ice formation by means of a more or less extensive supercooling of their body fluids. There is a tight correlation between the supercooling point (SCP) and the lower lethal temperature. Different species use different physiological adjustments to increase the likelihood of survival in a supercooled state. These include stabilization of the supercooled state by active antifreeze factors that cause thermal hysteresis between equilibrium melting and freezing points, the accumulation of low-molecular weight sugars and polyols with putative cryoprotective functions, or by having a relatively high body fluid osmolality, combined with a low level of hydration. The majority of species under study overwinter only as adults, whereas Velia caprai Tamanini can overwinter either as an adult or in the egg stage. The supercooling capacity of V. caprai adults is insufficient to prevent the risk of lethal freezing. The adults therefore survive only opportunistically in suitable microhabitats, and/or during mild winters. The survival of V. caprai in winter is assured by extensive supercooling and having overwintering eggs that are highly cold tolerant.

Research paper thumbnail of Effective strategy of the overwintering of semiaquatic bugs: overwintering of Velia caprai (Heteroptera: Gerromorpha: Veliidae)

Journal of Natural History, 2009

Overwintering of Velia caprai was studied during the winter months 2006–2007 in the area of South... more Overwintering of Velia caprai was studied during the winter months 2006–2007 in the area of South Bohemia (Czech Republic) by (1) field phenological observations and samples, (2) study of artificially established experimental cohorts in an unheated glasshouse, and (3) auxiliary experiments in a laboratory. Velia caprai has a unique way of overwintering within the gerromorphan bugs that is rare among

Research paper thumbnail of Analyses of Developmental Rate Isomorphy in Ectotherms: Introducing the Dirichlet Regression

PLOS ONE, 2015

Temperature drives development in insects and other ectotherms because their metabolic rate and g... more Temperature drives development in insects and other ectotherms because their metabolic rate and growth depends directly on thermal conditions. However, relative durations of successive ontogenetic stages often remain nearly constant across a substantial range of temperatures. This pattern, termed 'developmental rate isomorphy' (DRI) in insects, appears to be widespread and reported departures from DRI are generally very small. We show that these conclusions may be due to the caveats hidden in the statistical methods currently used to study DRI. Because the DRI concept is inherently based on proportional data, we propose that Dirichlet regression applied to individual-level data is an appropriate statistical method to critically assess DRI. As a case study we analyze data on five aquatic and four terrestrial insect species. We find that results obtained by Dirichlet regression are consistent with DRI violation in at least eight of the studied species, although standard analysis detects significant departure from DRI in only four of them. Moreover, the departures from DRI detected by Dirichlet regression are consistently much larger than previously reported. The proposed framework can also be used to infer whether observed departures from DRI reflect life history adaptations to size-or stage-dependent effects of varying temperature. Our results indicate that the concept of DRI in insects and other ectotherms should be critically re-evaluated and put in a wider context, including the concept of 'equiproportional development' developed for copepods.

Research paper thumbnail of Dispersal and Migration Patterns of Freshwater Semiaquatic Bugs

Insects

Semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha) are mostly wing-polymorphic species with f... more Semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha) are mostly wing-polymorphic species with flight dispersal as an important life history trait, but the specific flight ability and dispersal pattern remain unexplored in most species. This report presents the results of a long-term survey based on the individual marking of more than 23,000 specimens of eight water striders (Gerridae) and a water cricket Velia caprai (Veliidae). Three distinct lentic habitats were sampled (solitary fishponds, systems of nearby fishponds and systems of small, often temporary pools) and one lotic habitat—a small forest stream. Recaptures revealed that three gerrid species tend to stay at the breeding site, but can differ in dispersal via the water surface. Reproductive flightless females disperse most actively via the water surface, possibly bypassing the trade-off between dispersal and reproduction. One species has a sex-dependent dispersal pattern, with females being rather philopatric, whereas ma...

Research paper thumbnail of In memoriam of Professor Miroslav Papáček (1953–2019): biography, memories, bibliography and list of described taxa

Acta Entomologica Musei Nationalis Pragae

Professor Miroslav Papáček (1953–2019) was an eminent specialist in morphology, taxonomy, systema... more Professor Miroslav Papáček (1953–2019) was an eminent specialist in morphology, taxonomy, systematics, biology and ecology of aquatic and semiaquatic bugs (Hemiptera: Heteroptera: Nepomorpha, Gerromorpha). All his career was connected with the Department of Biology, Faculty of Education, University of South Bohemia in České Budějovice, Czech Republic. Here we provide his short biography, personal memories of his colleague, bibliography currently comprising 125 papers in zoology and 57 in didactics of biology, and an annotated list of the taxa he described, which includes one subfamily (Helotrephidae: Trephotomasinae), three genera, two subgenera and 41 species of Helotrephidae and Aphelocheiridae.

Research paper thumbnail of Climatic Variation of Supercooling Point in the Linden Bug Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)

Insects

Cold tolerance is often one of the key components of insect fitness, but the association between ... more Cold tolerance is often one of the key components of insect fitness, but the association between climatic conditions and supercooling capacity is poorly understood. We tested 16 lines originating from geographically different populations of the linden bug Pyrrhocoris apterus for their cold tolerance, determined as the supercooling point (SCP). The supercooling point was generally well explained by the climatic conditions of the population’s origin, as the best predictor—winter minimum temperature—explained 85% of the average SCP variation between populations. The supercooling capacity of P. apterus is strongly correlated with climatic conditions, which support the usage of SCP as an appropriate metric of cold tolerance in this species.

Research paper thumbnail of Efektivita badatelsky orientovaného vyučování na primárním stupni základních škol v přírodovědném vzdělávání v České republice s využitím prostředí školních zahrad

Scientia in educatione

Článek je zaměřen na průzkum účinnosti vyučovacích metod s prvky badatelsky orientovaného vyučová... more Článek je zaměřen na průzkum účinnosti vyučovacích metod s prvky badatelsky orientovaného vyučování (BOV) ve vazbě na prostředí školních zahrad na primárním stupni základních škol v České republice. Data byla získávána na základě metody experimentu typu spárovaných skupin. V rámci výzkumu opakovaně participovalo v experimentální skupině 73–75 žáků a ve skupině kontrolní 70–72 žáků ze čtvrté třídy. Získané výsledky poukazují na fakt, že badatelsky orientované vyučování má statisticky prokazatelný vliv na osvojování nových znalostí a na vzrůstající oblíbenost výuky přírodovědy u žáků na primárním stupni základních škol. Z dílčích výsledků je patrné, že pro větší efektivitu badatelsky orientovaných metod výuky musí dojít k jejich opakovanému zařazování do vyučování. V opačném případě se žákům BOV jeví jako složitě uchopitelné a příliš abstraktní.

Research paper thumbnail of The latitudinal uniformity of the unique life history of Velia caprai (Heteroptera: Veliidae) and notes to the pre-overwintering period of selected water striders (Heteroptera: Gerridae)

Entomologica Fennica

Temperate water striders (Gerridae) overwinter as adults and die after spring reproduction. Europ... more Temperate water striders (Gerridae) overwinter as adults and die after spring reproduction. European water cricket Velia caprai (Veliidae) overwinters concurrently in egg and adult stage in Central Europe. This rare overwintering strategy goes with longevity ofthis species. Adults can survive two winters in Central Europe, unlike other semiaquatic bugs. Scandinavian populations of V. caprai and water striders Gerris lacustris and G. lateralis were examined at the beginning and end of September to determine their life histories. Both gerrids start to overwinter during September, females prior to males and macropterous individuals prior to brachypterous. All females of G. lacustris and G. lateralis enter reproductive diapause before winter. V. caprai overwinters in both adult and egg stage in Norway, and can probably survive two winters. Central European and Scandinavian populations of V. caprai share the same unusual way of overwintering and probably also the whole life history.

Research paper thumbnail of Supercooling point is an individually fixed metric of cold tolerance in Pyrrhocoris apterus

Journal of Thermal Biology

Research paper thumbnail of Efficiency of subaquatic light traps

Research paper thumbnail of Relative male and female contributions to the supercooling point of their offspring inMicrovelia reticulata(Heteroptera: Veliidae)

Entomological Science, 2016

Cold hardiness is a key life history trait in temperate and polar ectothermic species, as it affe... more Cold hardiness is a key life history trait in temperate and polar ectothermic species, as it affects survival during overwintering, but its evolution is poorly understood. While many studies of cold hardiness in insects have shown differences between species, populations or developmental stages, data on the relative contribution of individual genotypes to cold hardiness are scarce and mainly limited to drosophilid fly species. We used a sib-analysis (paternal half-sib/full-sib breeding design) to estimate the relative contributions of parental generation to the supercooling point (SCP) of the offspring of a heteropteran non-model insect species, Microvelia reticulata (Heteroptera: Gerromorpha: Veliidae). We found that parent identity affected significantly SCP values of their offspring. Magnitudes of estimated sire and dam variance components were similar but the distributions of individual contributions to SCP differed between sires and dams, which points to sex-specific genetic or parental effects on SCP in this species. The animal model failed to find a realistic estimate of heritability (h 2) of SCP, suggesting that the underlying genetics of SCP in M. reticulata can not be characterized by purely additive effects.

Research paper thumbnail of Differences in prey capture in semiaquatic bugs (Heteroptera: Gerromorpha)

Entomological Science, 2016

Feeding behavior has been investigated several times in different semiaquatic bugs (Heteroptera: ... more Feeding behavior has been investigated several times in different semiaquatic bugs (Heteroptera: Gerromorpha), but has never been directly compared between species from lentic and lotic habitats and different families. Time required to capture prey was investigated in five gerromorphan species: Aquarius paludum, Gerris lacustris, G. odontogaster (Gerridae), Velia caprai and V. gridellii (Veliidae). This experiment used live and dead prey and intact and artificially blinded bugs. The presence of vibrational stimuli (live prey) significantly decreased latency to capture prey in all species except G. odontogaster. This species was the only one where visual stimuli affected the response significantly (only with dead prey). Latency to capture in Velia spp. was significantly shorter than that in the three gerrid species. Capture efficiency differed significantly between Gerris and Velia spp.; both Velia species carried out unsuccessful attack attempts less frequently than did the Gerris species. Prey capture was quicker in treatments with live prey and/or intact bugs. No difference in capture efficiency was found between sexes. Aquarius and Gerris species from predominantly lentic habitats needed more time to capture prey than did Velia species, which live mostly in streams. This difference in feeding behavior can probably allow coexistence of gerrids and veliids at sites where their occurrence overlaps.

Research paper thumbnail of Note to the effect of environmental conditions on the occurrence of benthic water bug Aphelocheirus aestivalis (Heteroptera: Aphelocheiridae)

Communications and Abstracts …

The aim of this study was to find out what abiotic environmental variables are related to the occ... more The aim of this study was to find out what abiotic environmental variables are related to the occurrence of benthic water bug Aphelocheirus aestivalis. Samples and abiotic environmental data sets obtained by extensive monitoring of Labe, Vltava and Danube river basis were sorted and analysed by Redundancy analysis (RDA). Results of RDA did not offer transparent response on our question. The reason is probably too rough scaling of environmental variables used commonly by hydrobiologist for monitoring of benthos in running waters. More detailed design of fieldwork is probably necessary for a better solution of question mentioned above.

Research paper thumbnail of Distribution of Gerris asper and G. lateralis (Hemiptera: Heteroptera: Gerridae) in the Czech Republic

All the available published and unpublished distributional records of two endangered pond skaters... more All the available published and unpublished distributional records of two endangered pond skaters, Gerris asper (Fieber, 1860) and Gerris lateralis Schummel, 1832 (Hemiptera: Heteroptera: Gerridae) in the Czech Republic are summarized and mapped. Gerris asper was originally described from Bohemia by Fieber (1860) without any exact locality and we have been unable to confirm its occurrence with any subsequently collected specimen. The distribution of G. asper in the Czech Republic thus seems to be limited to southern and central Moravia, with a single new record from northern Moravia, where it was found syntopically with G. lateralis. Gerris lateralis is widespread in Bohemia and a new species for Moravia, where it was collected on two sites in the north of the territory (the Czech Silesia). General distribution, biology and ecology of both species are reviewed and summarized.

Research paper thumbnail of Analyses of Developmental Rate Isomorphy in Ectotherms: Introducing the Dirichlet Regression

Temperature drives development in insects and other ectotherms because their metabolic rate and g... more Temperature drives development in insects and other ectotherms because their metabolic rate and growth depends directly on thermal conditions. However, relative durations of successive ontogenetic stages often remain nearly constant across a substantial range of temperatures. This pattern, termed 'developmental rate isomorphy' (DRI) in insects, appears to be widespread and reported departures from DRI are generally very small. We show that these conclusions may be due to the caveats hidden in the statistical methods currently used to study DRI. Because the DRI concept is inherently based on proportional data, we propose that Dirichlet regression applied to individual-level data is an appropriate statistical method to critically assess DRI. As a case study we analyze data on five aquatic and four terrestrial insect species. We find that results obtained by Dirichlet regression are consistent with DRI violation in at least eight of the studied species, although standard analysis detects significant departure from DRI in only four of them. Moreover, the departures from DRI detected by Dirichlet regression are consistently much larger than previously reported. The proposed framework can also be used to infer whether observed departures from DRI reflect life history adaptations to size-or stage-dependent effects of varying temperature. Our results indicate that the concept of DRI in insects and other ectotherms should be critically re-evaluated and put in a wider context, including the concept of 'equiproportional development' developed for copepods.

Research paper thumbnail of Differences in prey capture in semiaquatic bugs (Heteroptera: Gerromorpha

Feeding behavior has been investigated several times in different semiaquatic bugs (Heteroptera: ... more Feeding behavior has been investigated several times in different semiaquatic bugs (Heteroptera: Gerromorpha), but has never been directly compared between species from lentic and lotic habitats and different families. Time required to capture prey was investigated in five gerromorphan species: Aquarius paludum, Gerris lacustris, G. odontogaster (Gerridae), Velia caprai and V. gridellii (Veliidae). This experiment used live and dead prey and intact and artificially blinded bugs. The presence of vibrational stimuli (live prey) significantly decreased latency to capture prey in all species except G. odontogaster. This species was the only one where visual stimuli affected the response significantly (only with dead prey). Latency to capture in Velia spp. was significantly shorter than that in the three gerrid species. Capture efficiency differed significantly between Gerris and Velia spp.; both Velia species carried out unsuccessful attack attempts less frequently than did the Gerris species. Prey capture was quicker in treatments with live prey and/or intact bugs. No difference in capture efficiency was found between sexes. Aquarius and Gerris species from predominantly lentic habitats needed more time to capture prey than did Velia species, which live mostly in streams. This difference in feeding behavior can probably allow coexistence of gerrids and veliids at sites where their occurrence overlaps.

Research paper thumbnail of Relative male and female contributions to the supercooling point of their offspring in Microvelia reticulata (Heteroptera: Veliidae

Cold hardiness is a key life history trait in temperate and polar ectothermic species, as it affe... more Cold hardiness is a key life history trait in temperate and polar ectothermic species, as it affects survival during overwintering, but its evolution is poorly understood. While many studies of cold hardiness in insects have shown differences between species, populations or developmental stages, data on the relative contribution of individual genotypes to cold hardiness are scarce and mainly limited to drosophilid fly species. We used a sib-analysis (paternal half-sib/full-sib breeding design) to estimate the relative contributions of parental generation to the supercooling point (SCP) of the offspring of a heteropteran non-model insect species, Microvelia reticulata (Heteroptera: Gerromorpha: Veliidae). We found that parent identity affected significantly SCP values of their offspring. Magnitudes of estimated sire and dam variance components were similar but the distributions of individual contributions to SCP differed between sires and dams, which points to sex-specific genetic or parental effects on SCP in this species. The animal model failed to find a realistic estimate of heritability (h 2) of SCP, suggesting that the underlying genetics of SCP in M. reticulata can not be characterized by purely additive effects.

Research paper thumbnail of Effect of population density on the development of Mesovelia furcata (Mesoveliidae), Microvelia reticulata and Velia caprai (Veliidae) (Heteroptera: Gerromorpha)

Population density during nymphal development affects body size, developmental rate and wing poly... more Population density during nymphal development affects body size, developmental rate and wing polymorphism in semiaquatic bugs. Nymphs from crowded habitats grow faster and thus gain an advantage in the later stadia. Rapid development results in smaller body size in several gerrids. Macropterous adults develop more frequently at high population densities in most species, which enables the bugs to leave crowded habitats. Three European widespread species Mesovelia furcata Mulsant & Rey, 1852 (Mesoveliidae), Microvelia reticulata Burmeister, 1835 and Velia caprai Tamanini, 1947 (Veliidae) were reared individually and simultaneously either at a low or high population density. Duration of postembryonic development, wing morph, body size and length of distal oocyte in females were recorded. High population density accelerates development in Mesovelia furcata and Microvelia reticulata. However, there was no trade-off between developmental rate and body size. Accelerated development without a decrease in body size was probably because maturation was delayed. Individually reared nymphs developed faster than nymphs from communal cohorts. No long-winged Microvelia reticulata specimen developed in any treatment. However, more macropterous individuals developed in high-density treatments in Mesovelia furcata (significant) and Velia caprai (not significant). All the nymphs of the species that were reared individually developed into apterous adults. The results suggest that population density strongly influences the life history of semiaquatic bugs. However, the only commonly shared response seems to be an increase in developmental rate when reared at high population densities. Other traits such as wing dimorphism, body size and rate of oogenesis differ at the species level.

Research paper thumbnail of Comparative analysis of overwintering physiology in nine species of semi-aquatic bugs (Heteroptera: Gerromorpha)

Physiological Entomology, 2011

In semi-aquatic bugs (Heteroptera: Gerromorpha), the strategies of overwintering in a cryothermic... more In semi-aquatic bugs (Heteroptera: Gerromorpha), the strategies of overwintering in a cryothermic state (i.e. at body temperatures below the equilibrium freezing point) remain largely unexplored. The present study provides an analysis of the ecophysiological aspects of overwintering in nine gerromorphan species. All nine species avoid ice formation by means of a more or less extensive supercooling of their body fluids. There is a tight correlation between the supercooling point (SCP) and the lower lethal temperature. Different species use different physiological adjustments to increase the likelihood of survival in a supercooled state. These include stabilization of the supercooled state by active antifreeze factors that cause thermal hysteresis between equilibrium melting and freezing points, the accumulation of low-molecular weight sugars and polyols with putative cryoprotective functions, or by having a relatively high body fluid osmolality, combined with a low level of hydration. The majority of species under study overwinter only as adults, whereas Velia caprai Tamanini can overwinter either as an adult or in the egg stage. The supercooling capacity of V. caprai adults is insufficient to prevent the risk of lethal freezing. The adults therefore survive only opportunistically in suitable microhabitats, and/or during mild winters. The survival of V. caprai in winter is assured by extensive supercooling and having overwintering eggs that are highly cold tolerant.

Research paper thumbnail of Effective strategy of the overwintering of semiaquatic bugs: overwintering of Velia caprai (Heteroptera: Gerromorpha: Veliidae)

Journal of Natural History, 2009

Overwintering of Velia caprai was studied during the winter months 2006–2007 in the area of South... more Overwintering of Velia caprai was studied during the winter months 2006–2007 in the area of South Bohemia (Czech Republic) by (1) field phenological observations and samples, (2) study of artificially established experimental cohorts in an unheated glasshouse, and (3) auxiliary experiments in a laboratory. Velia caprai has a unique way of overwintering within the gerromorphan bugs that is rare among

Research paper thumbnail of Analyses of Developmental Rate Isomorphy in Ectotherms: Introducing the Dirichlet Regression

PLOS ONE, 2015

Temperature drives development in insects and other ectotherms because their metabolic rate and g... more Temperature drives development in insects and other ectotherms because their metabolic rate and growth depends directly on thermal conditions. However, relative durations of successive ontogenetic stages often remain nearly constant across a substantial range of temperatures. This pattern, termed 'developmental rate isomorphy' (DRI) in insects, appears to be widespread and reported departures from DRI are generally very small. We show that these conclusions may be due to the caveats hidden in the statistical methods currently used to study DRI. Because the DRI concept is inherently based on proportional data, we propose that Dirichlet regression applied to individual-level data is an appropriate statistical method to critically assess DRI. As a case study we analyze data on five aquatic and four terrestrial insect species. We find that results obtained by Dirichlet regression are consistent with DRI violation in at least eight of the studied species, although standard analysis detects significant departure from DRI in only four of them. Moreover, the departures from DRI detected by Dirichlet regression are consistently much larger than previously reported. The proposed framework can also be used to infer whether observed departures from DRI reflect life history adaptations to size-or stage-dependent effects of varying temperature. Our results indicate that the concept of DRI in insects and other ectotherms should be critically re-evaluated and put in a wider context, including the concept of 'equiproportional development' developed for copepods.