scholarly journals Effects of Environmental Stressors on the Early Development of Intertidal and Subtidal Gastropod Embryos

2021 ◽  
Author(s):  
◽  
Jeannine Fischer
Keyword(s):  
Embryonic Development ◽  
Early Development ◽  
Multiple Stressors ◽  
Environmental Stressors ◽  
Embryonic Mortality ◽  
Egg Mass ◽  
Egg Masses ◽  
Larval Stages ◽  
Carry Over ◽  
Species Specific

<p>Salinity, temperature and ultraviolet-B (UV-B) radiation are common environmental stressors in coastal habitats. These stressors are likely to increase in intensity due to the effects of climate change and can have important impacts on population and community dynamics for early development in gastropods that deposit egg masses on rocky shores. The aim of this study was to identify the effects of single and multiple stressors on the development of intertidal and shallow subtidal gastropods with encapsulated embryos. In manipulative experiments I exposed egg masses of the gastropod species Siphonaria australis, Ercolania felina, Pleurobranchaea maculata, Aplysia juliana and Doris wellingtonensis to realistic levels of either salinity, temperature or UV-B radiation, or to a combination of stressors, for different lengths of time. Embryos were then subjected to the most stressful levels of each stressor at either early or late stages of development and at different days of embryonic development. Further, egg masses were exposed to sublethal salinity, temperature and UV-B radiation stress simultaneously, simulating tide pool conditions on a warm sunny summer day. Larvae hatching from stressed and unstressed egg masses were subsequently periodically subjected to increased temperature and UV-B radiation and examined over 10 days to detect possible carry-over effects of exposure to stress in the egg mass. The results revealed that for individual stressors, low salinity (20‰), high temperature (25°C) and high UV-B (1.7 W m ⁻ ² s ⁻ ¹, i.e. a level similar to a sunny NZ summer day) all caused the highest embryonic mortality. The response to stressors was species-specific but overall the intertidal species had lower embryonic mortality than the subtidal species. Generally, chronic exposure had higher impacts on the development of embryos than periodic exposure and early embryonic development stages were most vulnerable to stress. UV-B radiation had particularly damaging effects on embryonic and larval stages for the intertidal pulmonate limpet Siphonaria australis. Further, multiple stressors had synergistic effects and caused high embryonic mortality in the egg mass as well as impacting on the vulnerability of larvae to stressors. This study revealed that stress experienced during embryonic stages can result in sub-lethal damage that increases vulnerability to temperature and decreases vulnerability to UV-B radiation experienced in the larval stage. In total, my results suggest that (1) the effects of different environmental stressors on early development of intertidal and subtidal gastropods are complex and depend on the intensity, duration and time of stress, and are generally species-specific; (2) multiple stressors can act synergistically to affect early development and (3) sublethal exposure to stress in the egg mass can have negative carry-over effects on later larval stages.</p>

scholarly journals Effects of Environmental Stressors on the Early Development of Intertidal and Subtidal Gastropod Embryos

2021 ◽  
Author(s):  
◽  
Jeannine Fischer
Keyword(s):  
Embryonic Development ◽  
Early Development ◽  
Multiple Stressors ◽  
Environmental Stressors ◽  
Embryonic Mortality ◽  
Egg Mass ◽  
Egg Masses ◽  
Larval Stages ◽  
Carry Over ◽  
Species Specific

<p>Salinity, temperature and ultraviolet-B (UV-B) radiation are common environmental stressors in coastal habitats. These stressors are likely to increase in intensity due to the effects of climate change and can have important impacts on population and community dynamics for early development in gastropods that deposit egg masses on rocky shores. The aim of this study was to identify the effects of single and multiple stressors on the development of intertidal and shallow subtidal gastropods with encapsulated embryos. In manipulative experiments I exposed egg masses of the gastropod species Siphonaria australis, Ercolania felina, Pleurobranchaea maculata, Aplysia juliana and Doris wellingtonensis to realistic levels of either salinity, temperature or UV-B radiation, or to a combination of stressors, for different lengths of time. Embryos were then subjected to the most stressful levels of each stressor at either early or late stages of development and at different days of embryonic development. Further, egg masses were exposed to sublethal salinity, temperature and UV-B radiation stress simultaneously, simulating tide pool conditions on a warm sunny summer day. Larvae hatching from stressed and unstressed egg masses were subsequently periodically subjected to increased temperature and UV-B radiation and examined over 10 days to detect possible carry-over effects of exposure to stress in the egg mass. The results revealed that for individual stressors, low salinity (20‰), high temperature (25°C) and high UV-B (1.7 W m ⁻ ² s ⁻ ¹, i.e. a level similar to a sunny NZ summer day) all caused the highest embryonic mortality. The response to stressors was species-specific but overall the intertidal species had lower embryonic mortality than the subtidal species. Generally, chronic exposure had higher impacts on the development of embryos than periodic exposure and early embryonic development stages were most vulnerable to stress. UV-B radiation had particularly damaging effects on embryonic and larval stages for the intertidal pulmonate limpet Siphonaria australis. Further, multiple stressors had synergistic effects and caused high embryonic mortality in the egg mass as well as impacting on the vulnerability of larvae to stressors. This study revealed that stress experienced during embryonic stages can result in sub-lethal damage that increases vulnerability to temperature and decreases vulnerability to UV-B radiation experienced in the larval stage. In total, my results suggest that (1) the effects of different environmental stressors on early development of intertidal and subtidal gastropods are complex and depend on the intensity, duration and time of stress, and are generally species-specific; (2) multiple stressors can act synergistically to affect early development and (3) sublethal exposure to stress in the egg mass can have negative carry-over effects on later larval stages.</p>

scholarly journals A Limpet’s Legacy: Carry-Over Effects across Life Stages and Generations Caused by Global Change Stressors

2021 ◽  
Author(s):  
◽  
Gustav Kessel
Keyword(s):  
Global Change ◽  
Marine Invertebrates ◽  
Multiple Stressors ◽  
Egg Mass ◽  
Life Stages ◽  
Developmental Stress ◽  
Egg Masses ◽  
Context Dependent ◽  
Carry Over

<p>Global change is increasingly impacting coastal marine systems. Organisms inhabiting the intertidal zone may be especially vulnerable to additional anthropogenic influences, which augment the naturally stressful, highly variable conditions to which they are already subjected and may lead to the manifestation of artificially severe carry-over effects (COEs). In marine invertebrates with complex life histories, COEs can occur between life stages, when the conditions experienced by one stage influence the characteristics or performance of the next, as well as trans-generationally, in which case the environment experienced by a parental generation affects offspring. Most of the existing literature surrounding COEs focuses only on those between life stages or generations, seldom both simultaneously, and do so with the implementation of only a single stressor. In nature however, organisms may be affected by both forms of COE, since the presence of one does not preclude the other, and are invariably subjected to multiple co-occurring stressors that can interact in complex ways. Consequently, how trans-generational COEs might impact the propagation of stress through offspring life stages remains unclear, and how these processes operate in a global change context is little understood. It was here aimed to elucidate the role of COEs under ongoing global change by addressing these common literature imitations and taking the novel approach of examining how the effects of multiple, global change-associated stressors carry-over from a parental generation through their offspring’s life stages in order to provide a more realistic representation of the conditions under which COEs manifest in the field.  This was done using Siphonaria australis, an intertidal pulmonate limpet that deposits benthic egg masses, from which hatch planktonic veliger larvae. Adult S. australis were subjected to one of four treatments for 4h/day over four weeks to induce trans-generational COEs: a no-stress control, a pollution treatment with added copper (5.0μg/L), a “climate change” treatment with elevated temperature (25°C) and UVR (1.7W/m2), and a full global change treatment incorporating all three stressors. At the end of this period, the egg masses laid under each of these adult treatments were subjected to further experimentation for two weeks by being redistributed among the same four treatments again, so as to produce 16 unique treatment histories of adult-to-egg mass stress. Of these, 11 provided successfully hatching larvae, which were reared and observed for COEs between life stages (from egg to larva) under ambient conditions (ie. no added stressors) for 27 days.  In adult S. australis survivor size, the size of egg masses laid and the size of individual eggs varied in complex ways over time and across treatments, while the number of survivors was unaffected by stress. Egg masses were unaffected in terms of hatching time but displayed strong responses to parental and developmental stress exposure through hatching success, and the percentage of viable eggs per egg mass, with the latter clearly declining according to adult treatment severity and both showing trans-generational COEs. Larval characteristics were extremely varied across treatment histories and highly context-dependent as hatching size, size reached by 27 days, growth rate, and size at death all showed evidence of COEs between generations and life stages, as well as interaction between both types of COE, with the number of survivors again being the only unaffected response variable. Overall, trans-generational COEs were slightly more common than those between life stages.  These results show that both forms of COE, each triggered by exposure to multiple stressors in progenitors and developmental stages, interact to form highly context-dependent legacies of mostly impaired performance in S. australis larvae. This implies that COEs may become more prominent with worsening stressors in the future and suggests that the role of COEs in the persistence of marine invertebrates under ongoing global change may so far have been underestimated by the existing literature.</p>

scholarly journals Effects of Ultraviolet Radiation (UVR) and Other Environmental Stressors on the Development of Intertital Mollusc Embryos

2021 ◽  
Author(s):  
◽  
Janine Mary Russell
Keyword(s):  
New Zealand ◽  
Ozone Depletion ◽  
Environmental Stressors ◽  
Embryonic Mortality ◽  
Egg Mass ◽  
The Sun ◽  
Full Spectrum ◽  
Egg Masses ◽  
Manipulative Experiments ◽  
Mollusc Species

<p>Ozone depletion is a humaninduced global phenomenon that allows increased ultraviolet radiation (UVR) to the Earth's surface. Although UVR is known to be harmful, relatively little is known about how increased UVR impacts natural ecosystems. Ecosystems in New Zealand are particularly at risk, because ozone depletion is much greater here, with levels of biologically harmful UVR up to two times greater than in northern latitudes. In the intertidal environment, potentially negative abiotic stressors are associated with low tide; and organisms inhabiting this environment are particularly vulnerable to UVR. Furthermore, embryos and larvae deposited in this habitat are especially susceptible to these stressors. The aim of this study is to identify the effect of UVR and other environmental stressors on the development of mollusc embryos in New Zealand. Surveys of microhabitats in which egg mass deposition occurs, and what effect this site of deposition has on the survivorship of embryos, revealed that encapsulated embryos of the two common pulmonate limpets Benhamina obliquata and Siphonaria australis are highly vulnerable to the environmental stressors associated with different microhabitats. In particular, egg masses deposited in the sun for both species suffered high mortality. Although, B. obliquata is more susceptible to UVR damage than is S. australis, B. obliquata predominantly deposits egg masses in dry shaded microhabitats while S. australis deposits the majority of its offspring in sunny tidal pools, which surprisingly equated to highest embryonic mortality. Results of manipulative experiments reflected those found in the surveys: egg masses exposed to full spectrum light incurred the greatest embryonic mortality; additionally environmental stressors (e.g. tidal pool conditions and desiccation) synergistically enhanced this mortality. UVR in North America is significantly lower compared to New Zealand; this allowed a unique opportunity to use identical methods to examine the responses of ecologically similar, related species (bubble shell snails in the genus Haminoea), from two regions where UVR naturally differs. Results from surveys and manipulative experiments revealed that the New Zealand species Haminoea zelandiae suffered high embryonic mortality under full spectrum light and this mortality was enhanced by periods of desiccation. The North American species Haminoea vesicula also suffered significant mortality during periods of desiccation, but there were no signs of UVR damage. These results appear to be driven by speciesspecific vulnerability to these stressors and not to ambient UVR intensity in the regions at the time of study. Relative concentrations of the chemical sunscreen compounds, mycosporinelike amino acids (MAAs), varied depending on several factors, but the biggest differences were among species. Analyses revealed that B. obliquata had the highest concentration of MAAs despite suffering high embryonic mortality when exposed to direct sunlight. MAA concentrations in S. australis were intermediate, with H. zelandiae having the lowest concentrations of all three species. MAA concentration for B. obliquata was dependent on stage of development and initial sun exposure at egg mass deposition site, suggesting interactions between MAAs, environmental conditions and embryonic development that need to be further explored. MAA concentrations were higher in S.australis egg masses deposited in spring compared to those deposited in early autumn, which may be driven by a shift in diet or nutrient levels. MAA concentrations did not appear to be correlated with ambient levels of UVR or embryonic survival in S.australis. However, MAA concentrations were related to UV irradiance in both Haminoea species with higher MAA concentrations observed in egg masses initially deposited in the sun compared to those found in the shade. Combined these results suggest: (1) increased UVR due to ozone depletion together with increases in temperatures due to climate change are likely to have strong impacts on the early life stages of these species, unless behavioural and physiological adaptations occur; (2) New Zealand species may be at particularly high risk from UVR damage compared to those from the Northern hemisphere; (3) the role of MAAs as photo-protection in these mollusc species is likely to be species specific, with a variety of abiotic and biotic factors influencing their uptake and sequestration. These experiments in part demonstrate how New Zealand's mollusc species are responding to humaninduced changes in UVR levels.</p>

scholarly journals Effects of Ultraviolet Radiation (UVR) and Other Environmental Stressors on the Development of Intertital Mollusc Embryos

2021 ◽  
Author(s):  
◽  
Janine Mary Russell
Keyword(s):  
New Zealand ◽  
Ozone Depletion ◽  
Environmental Stressors ◽  
Embryonic Mortality ◽  
Egg Mass ◽  
The Sun ◽  
Full Spectrum ◽  
Egg Masses ◽  
Manipulative Experiments ◽  
Mollusc Species

<p>Ozone depletion is a humaninduced global phenomenon that allows increased ultraviolet radiation (UVR) to the Earth's surface. Although UVR is known to be harmful, relatively little is known about how increased UVR impacts natural ecosystems. Ecosystems in New Zealand are particularly at risk, because ozone depletion is much greater here, with levels of biologically harmful UVR up to two times greater than in northern latitudes. In the intertidal environment, potentially negative abiotic stressors are associated with low tide; and organisms inhabiting this environment are particularly vulnerable to UVR. Furthermore, embryos and larvae deposited in this habitat are especially susceptible to these stressors. The aim of this study is to identify the effect of UVR and other environmental stressors on the development of mollusc embryos in New Zealand. Surveys of microhabitats in which egg mass deposition occurs, and what effect this site of deposition has on the survivorship of embryos, revealed that encapsulated embryos of the two common pulmonate limpets Benhamina obliquata and Siphonaria australis are highly vulnerable to the environmental stressors associated with different microhabitats. In particular, egg masses deposited in the sun for both species suffered high mortality. Although, B. obliquata is more susceptible to UVR damage than is S. australis, B. obliquata predominantly deposits egg masses in dry shaded microhabitats while S. australis deposits the majority of its offspring in sunny tidal pools, which surprisingly equated to highest embryonic mortality. Results of manipulative experiments reflected those found in the surveys: egg masses exposed to full spectrum light incurred the greatest embryonic mortality; additionally environmental stressors (e.g. tidal pool conditions and desiccation) synergistically enhanced this mortality. UVR in North America is significantly lower compared to New Zealand; this allowed a unique opportunity to use identical methods to examine the responses of ecologically similar, related species (bubble shell snails in the genus Haminoea), from two regions where UVR naturally differs. Results from surveys and manipulative experiments revealed that the New Zealand species Haminoea zelandiae suffered high embryonic mortality under full spectrum light and this mortality was enhanced by periods of desiccation. The North American species Haminoea vesicula also suffered significant mortality during periods of desiccation, but there were no signs of UVR damage. These results appear to be driven by speciesspecific vulnerability to these stressors and not to ambient UVR intensity in the regions at the time of study. Relative concentrations of the chemical sunscreen compounds, mycosporinelike amino acids (MAAs), varied depending on several factors, but the biggest differences were among species. Analyses revealed that B. obliquata had the highest concentration of MAAs despite suffering high embryonic mortality when exposed to direct sunlight. MAA concentrations in S. australis were intermediate, with H. zelandiae having the lowest concentrations of all three species. MAA concentration for B. obliquata was dependent on stage of development and initial sun exposure at egg mass deposition site, suggesting interactions between MAAs, environmental conditions and embryonic development that need to be further explored. MAA concentrations were higher in S.australis egg masses deposited in spring compared to those deposited in early autumn, which may be driven by a shift in diet or nutrient levels. MAA concentrations did not appear to be correlated with ambient levels of UVR or embryonic survival in S.australis. However, MAA concentrations were related to UV irradiance in both Haminoea species with higher MAA concentrations observed in egg masses initially deposited in the sun compared to those found in the shade. Combined these results suggest: (1) increased UVR due to ozone depletion together with increases in temperatures due to climate change are likely to have strong impacts on the early life stages of these species, unless behavioural and physiological adaptations occur; (2) New Zealand species may be at particularly high risk from UVR damage compared to those from the Northern hemisphere; (3) the role of MAAs as photo-protection in these mollusc species is likely to be species specific, with a variety of abiotic and biotic factors influencing their uptake and sequestration. These experiments in part demonstrate how New Zealand's mollusc species are responding to humaninduced changes in UVR levels.</p>

scholarly journals A Limpet’s Legacy: Carry-Over Effects across Life Stages and Generations Caused by Global Change Stressors

2021 ◽  
Author(s):  
◽  
Gustav Kessel
Keyword(s):  
Global Change ◽  
Marine Invertebrates ◽  
Multiple Stressors ◽  
Egg Mass ◽  
Life Stages ◽  
Developmental Stress ◽  
Egg Masses ◽  
Context Dependent ◽  
Carry Over

<p>Global change is increasingly impacting coastal marine systems. Organisms inhabiting the intertidal zone may be especially vulnerable to additional anthropogenic influences, which augment the naturally stressful, highly variable conditions to which they are already subjected and may lead to the manifestation of artificially severe carry-over effects (COEs). In marine invertebrates with complex life histories, COEs can occur between life stages, when the conditions experienced by one stage influence the characteristics or performance of the next, as well as trans-generationally, in which case the environment experienced by a parental generation affects offspring. Most of the existing literature surrounding COEs focuses only on those between life stages or generations, seldom both simultaneously, and do so with the implementation of only a single stressor. In nature however, organisms may be affected by both forms of COE, since the presence of one does not preclude the other, and are invariably subjected to multiple co-occurring stressors that can interact in complex ways. Consequently, how trans-generational COEs might impact the propagation of stress through offspring life stages remains unclear, and how these processes operate in a global change context is little understood. It was here aimed to elucidate the role of COEs under ongoing global change by addressing these common literature imitations and taking the novel approach of examining how the effects of multiple, global change-associated stressors carry-over from a parental generation through their offspring’s life stages in order to provide a more realistic representation of the conditions under which COEs manifest in the field.  This was done using Siphonaria australis, an intertidal pulmonate limpet that deposits benthic egg masses, from which hatch planktonic veliger larvae. Adult S. australis were subjected to one of four treatments for 4h/day over four weeks to induce trans-generational COEs: a no-stress control, a pollution treatment with added copper (5.0μg/L), a “climate change” treatment with elevated temperature (25°C) and UVR (1.7W/m2), and a full global change treatment incorporating all three stressors. At the end of this period, the egg masses laid under each of these adult treatments were subjected to further experimentation for two weeks by being redistributed among the same four treatments again, so as to produce 16 unique treatment histories of adult-to-egg mass stress. Of these, 11 provided successfully hatching larvae, which were reared and observed for COEs between life stages (from egg to larva) under ambient conditions (ie. no added stressors) for 27 days.  In adult S. australis survivor size, the size of egg masses laid and the size of individual eggs varied in complex ways over time and across treatments, while the number of survivors was unaffected by stress. Egg masses were unaffected in terms of hatching time but displayed strong responses to parental and developmental stress exposure through hatching success, and the percentage of viable eggs per egg mass, with the latter clearly declining according to adult treatment severity and both showing trans-generational COEs. Larval characteristics were extremely varied across treatment histories and highly context-dependent as hatching size, size reached by 27 days, growth rate, and size at death all showed evidence of COEs between generations and life stages, as well as interaction between both types of COE, with the number of survivors again being the only unaffected response variable. Overall, trans-generational COEs were slightly more common than those between life stages.  These results show that both forms of COE, each triggered by exposure to multiple stressors in progenitors and developmental stages, interact to form highly context-dependent legacies of mostly impaired performance in S. australis larvae. This implies that COEs may become more prominent with worsening stressors in the future and suggests that the role of COEs in the persistence of marine invertebrates under ongoing global change may so far have been underestimated by the existing literature.</p>

scholarly journals Early development of the Peruvian rock seabass Paralabrax humeralis (Teleostei: Serranidae): morphological description of the embryonic and yolk-sac larval stages

2021 ◽  
Vol 49 (3) ◽  
pp. 520-525
Author(s):  
Masatoshi Futagawa ◽  
Jessica Pizarro ◽  
German Bueno ◽  
Juan Pablo Díaz
Keyword(s):  
Embryonic Development ◽  
Water Temperature ◽  
Early Development ◽  
Yolk Sac ◽  
Morphological Description ◽  
Cleavage Stage ◽  
Pigmentation Pattern ◽  
Caudal Region ◽  
Larval Stages ◽  
In Captivity

Describe the embryonic development of Paralabrax humeralis (Peruvian rock seabass) and the present morphology of its eggs and yolk-sac larvae using the eggs spawned by P. humeralis broodstock in captivity. The spawning occurred naturally and spontaneously in early November 2018. The egg is pelagic and round, with a diameter of 0.98 ± 0.02 mm, an oil globule, and a diameter of 0.2 ± 0.02 mm. Embryonic development started with meroblastic cleavage, reaching the first cleavage stage at 0.4 h post-fertilization (HPF), and reached 64 cells at 2.2 HPF. Blastula period, 128 cells to 30% epiboly, end at 11.3 HPF. Gastrula period, 50% epiboly to 90% epiboly, end at 19.6 HPF. In the organogenesis period, forming Kupffer’s vesicle appeared at 22.5 HPF, the separation of the caudal fin from the yolk at 30.3 HPF, and the hatching of the first larvae at 47.9 HPF. Water temperature was kept at 17.2 ± 0.2°C. The yolk-sac larvae measured 2.22 ± 0.1 mm with a pigmentation pattern of pinpoint melanophores, all along with the embryo and xanthophores in the cephalic region, trunk, and caudal region, as well as in the oil globule. The larva takes feeds from three days post-hatch-out.

Embryonic development of southern calamary (Sepioteuthis australis) within the constraints of an aggregated egg mass

2003 ◽  
Vol 54 (3) ◽  
pp. 217 ◽  
Author(s):  
M. A. Steer ◽  
N. A. Moltschaniwskyj ◽  
A. R. Jordan
Keyword(s):  
Embryonic Development ◽  
Egg Mass ◽  
Congeneric Species ◽  
Developmental Difference ◽  
Developmental Duration ◽  
Egg Masses ◽  
Developmental Rates ◽  
Interspecific Comparisons ◽  
Loligo Pealei ◽  
Developmental Scheme

A post-cleavage embryological scheme was established for southern calamary Sepioteuthis australis. Using this developmental scheme, intra- and interspecific comparisons were made. Sepioteuthis australis development most closely resembled that of its tropical congeneric species, S. lessoniana, with only a few subtle heterochronies. The greatest developmental difference was observed when comparisons were made with Loligo pealei. These differences were attributed to developmental duration and respective egg sizes. Within S. australis, variation in developmental rates among embryos was associated with the size of the egg mass, with less variation evident in smaller egg masses. Embryos located on the periphery of the egg mass and at the distal or unattached end of an individual egg strand developed significantly faster than those located deep within the egg mass. On average, embryos in small egg masses, consisting of five individual egg strands, developed significantly faster than those in dense aggregations (>100 strands).

Oviposition behaviour, egg-masses and hatching response of the eggs of five Nearctic species of Simulium (Diptera: Simuliidae)

1979 ◽  
Vol 69 (3) ◽  
pp. 405-425 ◽  
Author(s):  
Jane E Imhof ◽  
Stephenm M Smith
Keyword(s):  
Embryonic Development ◽  
Oviposition Behaviour ◽  
Egg Mass ◽  
Hatch Rate ◽  
Egg Masses ◽  
Complete Development

AbstractThe oviposition behaviour of Simulium decorum Wlk., S. vittatum Zett., S. verecundum Stone & Jamnback and S. vernum Macq. is described, with emphasis on the approach by the females to the egglaying sites, the substrates selected and the behaviour of the flies while laying. The eggs and egg-masses of these four species and S. longistylatum Shewell are described; the eggs can be distinguished on the basis of size, and a key is provided to aid their identification. Eggs of S. vittatum completed embryonic development and hatched more quickly than those of S. verecundum of the same age at both 15 and 24°C. The hatch rate of the eggs of both species exceeded 90% when the eggs were present in single-layered masses. The position of an egg Within a multi-layered mass had an important effect on its ability to complete development; significantly lower proportions of eggs of both S. verecundum and S. vittatum in the lowermost layers of large egg-masses hatched, compared with the hatch of those in the top layer. The location of an egg within an egg-mass must be considered a major factor of mortality in the egg stage. The eggs of neither S. verecundum nor S. vittatum were resistant to drying; mortality due to desiccation was related to both the duration of the drying period and the stage of embryonic development when they were subjected to drying.

Embryonic and postembryonic development in the Tasman freshwater crayfishes Astacopsis gouldi, Asatcopisis franklinni and Parastacoides tasmanicus tasmanicus (Decapoda : Parastacidae)

1992 ◽  
Vol 43 (4) ◽  
pp. 861 ◽  
Author(s):  
P Hamr
Keyword(s):  
Embryonic Development ◽  
Developmental Stage ◽  
Early Development ◽  
Postembryonic Development ◽  
General Development ◽  
Larval Stages ◽  
New Information ◽  
Stage 1

The embryonic and postembryonic development of the endemic Tasmanian freshwater crayfishes of the genera Astacopsis and Parastacoides was studied and described in detail. The embryonic development was similar in the two genera and corresponded to that described for other Parastacidae and Astacidae, but a prominent change in the colour of the yolk that parallels embryonic development was also noted. The general development sequence of young from Stage 1 to Stage 3 in Astacopsis and Parastacoides is similar to that described for other parastacid, astacid and cambarid crayfishes, but major differences in development between Astacopsis and other crayfishes are an extra developmental stage as well as the timing of the development of the uropods. The postembryonic development in Astacopsis is different from that in other parastacids as well as astaciddcambarids in having retained some of the ancestral marine larval characters, and it is considered to be primitive. Given this new information, it is proposed that early development in freshwater crayfishes recapitulates the entire primitive decapod sequence of larval stages.

Live Confocal Analysis of Fertilization and Early Development

2001 ◽  
Vol 7 (S2) ◽  
pp. 1012-1013
Author(s):  
Uyen Tram ◽  
William Sullivan
Keyword(s):  
Drosophila Melanogaster ◽  
Embryonic Development ◽  
Real Time ◽  
Early Development ◽  
Fluorescent Probes ◽  
Primary Defect ◽  
Fluorescent Analysis ◽  
Dynamic Event ◽  
Enormous Amount ◽  
Fluorescent Studies

Embryonic development is a dynamic event and is best studied in live animals in real time. Much of our knowledge of the early events of embryogenesis, however, comes from immunofluourescent analysis of fixed embryos. While these studies provide an enormous amount of information about the organization of different structures during development, they can give only a static glimpse of a very dynamic event. More recently real-time fluorescent studies of living embryos have become much more routine and have given new insights to how different structures and organelles (chromosomes, centrosomes, cytoskeleton, etc.) are coordinately regulated. This is in large part due to the development of commercially available fluorescent probes, GFP technology, and newly developed sensitive fluorescent microscopes. For example, live confocal fluorescent analysis proved essential in determining the primary defect in mutations that disrupt early nuclear divisions in Drosophila melanogaster. For organisms in which GPF transgenics is not available, fluorescent probes that label DNA, microtubules, and actin are available for microinjection.

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