Gerald Kuchling - Academia.edu (original) (raw)

Papers by Gerald Kuchling

Endangered Species Research, Sep 17, 2020

Species with restricted ranges and long generation times are vulnerable to climate change due to ... more Species with restricted ranges and long generation times are vulnerable to climate change due to limited opportunity to disperse or adapt. Australia's rarest reptile, the western swamp turtle Pseudemydura umbrina, persists naturally in only one seasonal swamp that holds water in the Austral winter and spring. A marked reduction in winter rainfall in recent decades has shortened the swamp hydroperiod, restricting when turtles are able to feed, grow and reproduce. To mitigate possible future loss of reproductive capacity in the native habitat, assisted colonisation was trialled in 2016 using 35 captive-bred juveniles. Here, we report the outcomes of this 6 mo trial, which compared the growth of turtles released approximately 300 km south of the species' indigenous range with growth of turtles released at an existing northern translocation site. We showed that growth rates comparable to those at warmer northern translocation sites can be achieved in the south, even in an atypically cool spring as occurred in 2016. Microclimates available to P. umbrina at 2 southern sites were suitable for foraging and growth in late spring and early summer, but juvenile growth at one southern site was significantly better than at the other, likely due to higher prey biomass when water temperatures were suitable for foraging. These early results suggest that introduction of P. umbrina to seasonal wetlands near the south coast of Western Australia could be considered in the immediate future, but further trials are recommended to assess growth and survivorship over longer periods.

Journal of Sea Research, 2019

Dynamic energy budget (DEB) theory provides a generalised way to quantify how an organism assimil... more Dynamic energy budget (DEB) theory provides a generalised way to quantify how an organism assimilates and utilizes energy throughout its life cycle. Over 800 DEB models have been created to date, typically under the assumption of constant food supply. The Critically Endangered, semi-aquatic western swamp turtle occupies an ephemeral wetland environment in which food resources fluctuate from abundant to absent with the seasonal filling and drying of swamps. Approximately six months of each year are spent in aestivation underground when the swamps are dry and conditions are warm. We estimated DEB parameters for the western swamp turtle with the explicit incorporation of these seasonal fluctuations in food and temperature. A metabolic depression factor was applied during the aestivation stage, for which a value of around 50% best matched our life-history data. The swamp turtle had a very high Arrhenius temperature, being almost 2.5-fold greater than that of the other Testudine species for which there are DEB models (typical Arrhenius temperatures are around 8000K; western swamp turtle is 19371K). It also had the second highest somatic maintenance costs of the reptiles in the DEB 'Add My Pet' collection, and the highest for Testudines. We explore these results in context of the 'waste-to-hurry' hypothesis, which we suggest may apply for this species. We also consider how a DEB model for this species might be applied in its future conservation and management.

Australian Journal of Zoology, 2014

Thermal performance curves are useful for predicting how organisms might respond to environmental... more Thermal performance curves are useful for predicting how organisms might respond to environmental change, and are becoming increasingly applicable for ectothermic animals threatened by climate change. Here we present a thermal performance curve for the critically endangered western swamp turtle (Pseudemydura umbrina) based upon measurements of O 2 consumption and CO 2 production obtained by flow-through respirometry at temperatures between 15 and 30 C. Standard metabolic rate was significantly higher at 30 C (0.030 mL g-1 h-1 O 2 , 0.021 mL g-1 h-1 CO 2) than at 20 C (0.007 mL g-1 h-1 O 2 , 0.006 mL g-1 h-1 CO 2) and the 20À30 C Q 10 for O 2 and CO 2 were 4.60 and 3.55 respectively. Oxygen consumption rates at 15 C and 25 C were 0.002 (AE0.000) and 0.018 (AE0.000) mL g-1 h-1 , with a corresponding Q 10 of 9.21. Beyond~30 C there was a decline in physiological performance, which was supported by activity patterns reported for P. umbrina in the literature.

Biological Conservation, Dec 1, 2016

Abstract The embryos of many egg-laying species develop under the environmental conditions select... more Abstract The embryos of many egg-laying species develop under the environmental conditions selected by one or both parents, and these conditions may cease to be optimal under a changed climate. Assisted colonization is an emerging option to relocate species that are threatened by unfavourable changes in the local climate, but the incubation requirements of embryos are rarely considered in conservation translocations despite suggestions that relocation of early life stages could be more effective than relocating older animals. Here we review examples and outcomes of relocations of reptile eggs, and the decision tools currently available for guiding translocation decisions from an embryonic perspective. We then demonstrate a mechanistic approach, using the modelling framework NicheMapR, for assessing the optimal translocation range for the Western Swamp Turtle ( Pseudemydura umbrina ), a Critically Endangered reptile with an extremely restricted natural distribution. We determine thermal reaction norms and critical thermal limits for embryonic development based on laboratory and field data, and model soil temperatures at typical nest depths, simulate embryonic development at these depths, and map the probability of survival of P. umbrina embryos within the major bioregions of south-western Australia. The same model forced by future climates for 2050–70 demonstrates a southerly shift in the regions where embryos would be viable. However, if P. umbrina is to be translocated in the near future to regions 300–400 km south of its natural range, females will need to nest in relatively unshaded sites to achieve temperatures that are high enough to promote hatchling success.

Chelonian Conservation and Biology, 1995

Endangered Species Research, Apr 12, 2012

Climate change can affect the availability of transient habitats upon which many species depend f... more Climate change can affect the availability of transient habitats upon which many species depend for growth and reproduction. In southwestern Western Australia, declines in winter rainfall since the 1970s have shortened the hydroperiod of ephemeral swamps occupied by the Critically Endangered western swamp tortoise Pseudemydura umbrina reducing the length of the growing period of hatchlings and juveniles. Here, we tested whether the warmer water temperatures expected under global climate change could compensate for a shorter growing season. We increased pond temperatures of captive hatchlings and juveniles (1 and 2 yr old) by 1 to 2°C, and showed that growth rates and rates of food intake increased with temperature, with hatchlings in heated ponds increasing their mass by an additional 78% compared to hatchlings in unheated ponds. Hatchlings had a growth rate 8 times greater than that of juveniles. With an unlimited food supply, we predict that wild hatchlings will reach the critical mass (about 18 g) necessary to survive their first aestivation period at least 1 mo earlier under projected climate change by 2050. However, because shorter hydroperiods translate to longer periods for dry-season aestivation, small tortoises that have allocated all their energy to growth will be especially vulnerable to depletion of energy stores during aestivation.

Chelonian Conservation and Biology, Jun 1, 2012

Australia, with his research focusing on ecology, reproductive biology, captive breeding and cons... more Australia, with his research focusing on ecology, reproductive biology, captive breeding and conservation of endangered tortoises and turtles.

Springer eBooks, 1999

The anatomical, histological, endocrinological, physiological and behavioural methods used to stu... more The anatomical, histological, endocrinological, physiological and behavioural methods used to study reproduction of chelonians are principally the same as for other vertebrates. The box-like armour of chelonians, however, makes access to reproductive organs more difficult than in most other groups. Hurdles to reproductive biological investigations include difficulties in finding animals (or certain life stages) on a regular basis over the whole year, difficulties in readily assessing reproductive conditions in live animals (some species are even difficult to sex externally) and difficulties in obtaining blood or tissue samples. Reviews and comprehensive descriptions of general techniques for chelonian life history studies (including collecting, trapping, tracking, marking techniques, measurements and stomach flushing for dietary analyses) can be found in Gibbons (1990b), Graham (1979) and Wilbur and Morin (1988); details are beyond the scope of this book and are not presented here. Beyond the scope of this book also is the description of reproductive physiological laboratory techniques. This account deals primarily with methods to obtain reproductive biological data during field investigations.

Springer eBooks, 1999

In all organisms, reproduction is timed through natural selection to occur during those periods o... more In all organisms, reproduction is timed through natural selection to occur during those periods of the year that are most propitious for the survival of both parent and young. According to Baker (1938), these favourable conditions are the “ultimate cause” of a particular breeding season; the “proximate causes” which are another set of factors, initiate the sexual cycles at the appropriate time of the year (see Chap. 6). In the following account I will firstly discuss cycles according to the climatic zones, then discuss multi-year cycles and then some special adaptations to unpredictable or extreme environments. The focus of this chapter is on gonadal, mating and nesting cycles, and their timing.

Amphibia-reptilia, 1981

Tortoises (Testudo hermanni hermanni) which are cooled down to 5 °C show a considerable higher ox... more Tortoises (Testudo hermanni hermanni) which are cooled down to 5 °C show a considerable higher oxygen consumption during the first week at this temperature in June and August than in November, which is the time when hibernation normally starts. Prolonging the low temperature conditions in spring leads to an increase in oxygen consumption. The blood glucose concentration is reduced during normal hibernation, but can rise quickly when the animals are disturbed. During cold torpor induced in June and August the blood glucose concentration is drastically increased. The results support the hypothesis according which hibernation in the tortoise is the result of a metabolic preparation in autumn and cannot be induced artificially during spring and summer. Endogenous factors are involved in the termination of the physiological phenomena of hibernation in spring.

Amphibia-reptilia, 1981

Testudo hermanni hermanni shows a post-nuptial testicular cycle with the peak of spermiogenesis i... more Testudo hermanni hermanni shows a post-nuptial testicular cycle with the peak of spermiogenesis in July and August. Endogenous factors as well as the rising temperature initiate the beginning of spermatocytogenesis in spring. The temperature threshold for the initiation of complete spermiogenesis lies between 21 and 26 °C of constant environmental temperature. Gonadal regression in autumn is the result of low temperature and short photoperiod together with an endogenous readiness. From June to August low temperature (5 °C) and constant darkness did not induce gonadal regression.

International Zoo Yearbook, 1988

Chelonian Conservation and Biology, 2006

Gonads and accessory ducts of 140 live, captive-raised juvenile Erymnochelys madagascariensis (72... more Gonads and accessory ducts of 140 live, captive-raised juvenile Erymnochelys madagascariensis (72-375 g body mass) of 1-3 years of age as well as those of some wild, larger turtles were investigated by endoscopy. The gonads of all examined turtles could be visualized by endoscopy and unambiguously identified as testes or ovaries. Of the captive-raised juveniles, 75% were females and 25% males. One-year-old females have small, thin, transparent ovaries with transparent, whitish follicles and thin oviducts. Follicles in 2-year-old females increase in number and appear as transparent, whitish flat discs and the oviducts become broader and transparentwhitish to whitish. Three-year-old females have yellowish-whitish follicles and whitish oviducts. Juvenile females over 0.5 kg body mass have yellow follicles and white oviducts. A 1-year-old male and 2 small 2-year-old males show testes of rose pink-whitish color and transparent epididymes. Other 2-year-old males have yellowish-orange testes and in males. 130 g body mass, the epididymes turn transparent-whitish. Three-year-old males have yellow-orange testes that are thicker and rounder, and whitish epididymes with meandering ducti epididymides. The developmental changes of juvenile reproductive tracts seem to depend more on age than on size.

General and Comparative Endocrinology, Jun 1, 1981

Abstract Males of the tortoise Testudo h. hermanni of a natural population in Montenegro, Yugosla... more Abstract Males of the tortoise Testudo h. hermanni of a natural population in Montenegro, Yugoslavia, and captive ones in an outside area in Vienna, Austria, were used for a comparative investigation. Throughout the year testis and epididymis were examined histologically and the activity of β- N -acetylglucosaminidase in these organs was determined biochemically and histochemically. The activity of this enzyme increased in the testis and epididymis with the appearance of differentiated spermatozoa during summer. In the epithelium of the ductuli epididymides there were segments with very high and others with very low activity of this enzyme at that time. In the testis only moderate activity of 3β-hydroxysteroid dehydrogenase was found from January to June in the Leydig cells and at any time of the year in the Sertoli cells. The concentration of testosterone in blood plasma was maximal during summer, the main period of spermiogenesis, minimal during winter, and between these levels in spring, during the main mating period. The high concentration of plasma testosterone in summer may have been necessary for the activation of β- N -acetylglucosaminidase in the ductuli epididymides at the time of the passage of spermatozoa.

Journal of Zoology, Mar 1, 1993

The reproductive organs of logn‐term captive females and of wild females of the western swamp tor... more The reproductive organs of logn‐term captive females and of wild females of the western swamp tortoise, Pseudemydura umbrina, which were taken temporarily into captivity, were studied over several years by ultra‐sound scanning. Pseudemydura umbrina, a critically‐endangered species, is active during winter and spring when the ephemeral swamps it inhabits contain water and aestivates during summer and autumn (November to May/June) when the swamps are dry. The vitellogenic growth of ovarian follicles commences during aestivation in summer and continues during autumn and winter. The timing of the vitellogenic cycle is remarkably similar to that of many other Australian chelids and that of many other chelonians of temperate and subtropical regions, but the patterns of energy harvest, storage and allocation to ovarian follicles is different. Ovulation occurs between late September and early November and is preceded by a feeding bout and a sharp increase in female body mass. One clutch of 3–5 eggs (exceptionally of one or two) is laid in November/December. Sub‐adult females show cycles of follicular growth, followed by atresia, for several years before ovulating and laying eggs. Females taken into captivity may miss the following vitelogenic cycle, but captivity does not generally affect vitellogenic cycles. Ovulation and egg production of captive animals is easily suppressed, however, under stress or sub‐optimal food intake in spring. The sensitivity of ovulation to sub‐optimal conditions and the subsequent reabsorption of the yolk material may enhance survival of the reproducing individual during long dry periods in an unpredictable environment.

Zoophysiology, 1999

... The reproductive biology of the chelonia. Post a Comment. CONTRIBUTORS: Author: Kuchling, G. ... more ... The reproductive biology of the chelonia. Post a Comment. CONTRIBUTORS: Author: Kuchling, G. PUBLISHER: Springer (Berlin and New York). SERIES TITLE: YEAR: 1999. PUB TYPE: Book (ISBN 3540630139 ). VOLUME/EDITION: Volume 38. PAGES (INTRO/BODY): xi, 223 ...

The status of Kachuga trivittata is the most precarious of all the endemic turtles in Myanmar. Ka... more The status of Kachuga trivittata is the most precarious of all the endemic turtles in Myanmar. Kachuga trivittata is listed as "endangered" in the 2000 IUCN Red List of Threatened Species. However, the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group & Asian Turtle Trade Working Group (2000) proposed (pp. 160): "Actually a candidate for CR (critical) or EX (extinct), considering that no animals have been reliably recorded since 1935 despite mass trade of riverine turtles from MM (Myanmar) to CN (China)." Fig. 1: Kachuga trivittata female #5, Yadanabon Zoo, July 2003 KACHUGA TRIVITTATA IN CAPTIVITY No live K. trivittata were recorded between 1935 and 2002. Accordingly, until 2002 the species was not represented anywhere in captivity. The first live specimens recorded in Myanmar for 67 years were the two females and one male found in the Mahamuni Paya pond in July/August 2002 (Kuchling et al., in press; see Table 1). These three specimens were transferred to Yadanabon Zoo in Mandalay. However, there were no suitable facilities (ponds) for the maintenance of river turtles at Yadanabon Zoo and the turtles were moved several times between the elephant bathing pond and a preliminary ground pond. Unfortunately, the male (# 4) disappeared during November or December 2002. The larger female (#5) had a severe inflammation of the knee joint with osteomyelitis in January 2003, but recovered fully after antibiotic treatment.

Springer eBooks, 1999

The major threats to the persistence of chelonian species around the world are over-exploitation ... more The major threats to the persistence of chelonian species around the world are over-exploitation by humans, habitat loss and environmental degradation. That exploitation for food can extirpate chelonians was already convincingly demonstrated as early as the eighteenth century, when six out of eight species of giant tortoises on Indian Ocean islands were slaughtered and eaten until extinct (one more followed in the nineteenth century). Today, the IUCN-SSC (the World Conservation Union Species Survival Commission) classifies 38% of the world’s chelonians as threatened: 4% as critically endangered, 11% as endangered and 23% as vulnerable. Chelonians, thus, contain a much higher percentage of threatened taxa than birds and mammals, of which, respectively, 11 and 25% are threatened (Baillie 1996).

Endangered Species Research, Sep 17, 2020

Species with restricted ranges and long generation times are vulnerable to climate change due to ... more Species with restricted ranges and long generation times are vulnerable to climate change due to limited opportunity to disperse or adapt. Australia's rarest reptile, the western swamp turtle Pseudemydura umbrina, persists naturally in only one seasonal swamp that holds water in the Austral winter and spring. A marked reduction in winter rainfall in recent decades has shortened the swamp hydroperiod, restricting when turtles are able to feed, grow and reproduce. To mitigate possible future loss of reproductive capacity in the native habitat, assisted colonisation was trialled in 2016 using 35 captive-bred juveniles. Here, we report the outcomes of this 6 mo trial, which compared the growth of turtles released approximately 300 km south of the species' indigenous range with growth of turtles released at an existing northern translocation site. We showed that growth rates comparable to those at warmer northern translocation sites can be achieved in the south, even in an atypically cool spring as occurred in 2016. Microclimates available to P. umbrina at 2 southern sites were suitable for foraging and growth in late spring and early summer, but juvenile growth at one southern site was significantly better than at the other, likely due to higher prey biomass when water temperatures were suitable for foraging. These early results suggest that introduction of P. umbrina to seasonal wetlands near the south coast of Western Australia could be considered in the immediate future, but further trials are recommended to assess growth and survivorship over longer periods.

Journal of Sea Research, 2019

Dynamic energy budget (DEB) theory provides a generalised way to quantify how an organism assimil... more Dynamic energy budget (DEB) theory provides a generalised way to quantify how an organism assimilates and utilizes energy throughout its life cycle. Over 800 DEB models have been created to date, typically under the assumption of constant food supply. The Critically Endangered, semi-aquatic western swamp turtle occupies an ephemeral wetland environment in which food resources fluctuate from abundant to absent with the seasonal filling and drying of swamps. Approximately six months of each year are spent in aestivation underground when the swamps are dry and conditions are warm. We estimated DEB parameters for the western swamp turtle with the explicit incorporation of these seasonal fluctuations in food and temperature. A metabolic depression factor was applied during the aestivation stage, for which a value of around 50% best matched our life-history data. The swamp turtle had a very high Arrhenius temperature, being almost 2.5-fold greater than that of the other Testudine species for which there are DEB models (typical Arrhenius temperatures are around 8000K; western swamp turtle is 19371K). It also had the second highest somatic maintenance costs of the reptiles in the DEB 'Add My Pet' collection, and the highest for Testudines. We explore these results in context of the 'waste-to-hurry' hypothesis, which we suggest may apply for this species. We also consider how a DEB model for this species might be applied in its future conservation and management.

Australian Journal of Zoology, 2014

Thermal performance curves are useful for predicting how organisms might respond to environmental... more Thermal performance curves are useful for predicting how organisms might respond to environmental change, and are becoming increasingly applicable for ectothermic animals threatened by climate change. Here we present a thermal performance curve for the critically endangered western swamp turtle (Pseudemydura umbrina) based upon measurements of O 2 consumption and CO 2 production obtained by flow-through respirometry at temperatures between 15 and 30 C. Standard metabolic rate was significantly higher at 30 C (0.030 mL g-1 h-1 O 2 , 0.021 mL g-1 h-1 CO 2) than at 20 C (0.007 mL g-1 h-1 O 2 , 0.006 mL g-1 h-1 CO 2) and the 20À30 C Q 10 for O 2 and CO 2 were 4.60 and 3.55 respectively. Oxygen consumption rates at 15 C and 25 C were 0.002 (AE0.000) and 0.018 (AE0.000) mL g-1 h-1 , with a corresponding Q 10 of 9.21. Beyond~30 C there was a decline in physiological performance, which was supported by activity patterns reported for P. umbrina in the literature.

Biological Conservation, Dec 1, 2016

Abstract The embryos of many egg-laying species develop under the environmental conditions select... more Abstract The embryos of many egg-laying species develop under the environmental conditions selected by one or both parents, and these conditions may cease to be optimal under a changed climate. Assisted colonization is an emerging option to relocate species that are threatened by unfavourable changes in the local climate, but the incubation requirements of embryos are rarely considered in conservation translocations despite suggestions that relocation of early life stages could be more effective than relocating older animals. Here we review examples and outcomes of relocations of reptile eggs, and the decision tools currently available for guiding translocation decisions from an embryonic perspective. We then demonstrate a mechanistic approach, using the modelling framework NicheMapR, for assessing the optimal translocation range for the Western Swamp Turtle ( Pseudemydura umbrina ), a Critically Endangered reptile with an extremely restricted natural distribution. We determine thermal reaction norms and critical thermal limits for embryonic development based on laboratory and field data, and model soil temperatures at typical nest depths, simulate embryonic development at these depths, and map the probability of survival of P. umbrina embryos within the major bioregions of south-western Australia. The same model forced by future climates for 2050–70 demonstrates a southerly shift in the regions where embryos would be viable. However, if P. umbrina is to be translocated in the near future to regions 300–400 km south of its natural range, females will need to nest in relatively unshaded sites to achieve temperatures that are high enough to promote hatchling success.

Chelonian Conservation and Biology, 1995

Endangered Species Research, Apr 12, 2012

Climate change can affect the availability of transient habitats upon which many species depend f... more Climate change can affect the availability of transient habitats upon which many species depend for growth and reproduction. In southwestern Western Australia, declines in winter rainfall since the 1970s have shortened the hydroperiod of ephemeral swamps occupied by the Critically Endangered western swamp tortoise Pseudemydura umbrina reducing the length of the growing period of hatchlings and juveniles. Here, we tested whether the warmer water temperatures expected under global climate change could compensate for a shorter growing season. We increased pond temperatures of captive hatchlings and juveniles (1 and 2 yr old) by 1 to 2°C, and showed that growth rates and rates of food intake increased with temperature, with hatchlings in heated ponds increasing their mass by an additional 78% compared to hatchlings in unheated ponds. Hatchlings had a growth rate 8 times greater than that of juveniles. With an unlimited food supply, we predict that wild hatchlings will reach the critical mass (about 18 g) necessary to survive their first aestivation period at least 1 mo earlier under projected climate change by 2050. However, because shorter hydroperiods translate to longer periods for dry-season aestivation, small tortoises that have allocated all their energy to growth will be especially vulnerable to depletion of energy stores during aestivation.

Chelonian Conservation and Biology, Jun 1, 2012

Australia, with his research focusing on ecology, reproductive biology, captive breeding and cons... more Australia, with his research focusing on ecology, reproductive biology, captive breeding and conservation of endangered tortoises and turtles.

Springer eBooks, 1999

The anatomical, histological, endocrinological, physiological and behavioural methods used to stu... more The anatomical, histological, endocrinological, physiological and behavioural methods used to study reproduction of chelonians are principally the same as for other vertebrates. The box-like armour of chelonians, however, makes access to reproductive organs more difficult than in most other groups. Hurdles to reproductive biological investigations include difficulties in finding animals (or certain life stages) on a regular basis over the whole year, difficulties in readily assessing reproductive conditions in live animals (some species are even difficult to sex externally) and difficulties in obtaining blood or tissue samples. Reviews and comprehensive descriptions of general techniques for chelonian life history studies (including collecting, trapping, tracking, marking techniques, measurements and stomach flushing for dietary analyses) can be found in Gibbons (1990b), Graham (1979) and Wilbur and Morin (1988); details are beyond the scope of this book and are not presented here. Beyond the scope of this book also is the description of reproductive physiological laboratory techniques. This account deals primarily with methods to obtain reproductive biological data during field investigations.

Springer eBooks, 1999

In all organisms, reproduction is timed through natural selection to occur during those periods o... more In all organisms, reproduction is timed through natural selection to occur during those periods of the year that are most propitious for the survival of both parent and young. According to Baker (1938), these favourable conditions are the “ultimate cause” of a particular breeding season; the “proximate causes” which are another set of factors, initiate the sexual cycles at the appropriate time of the year (see Chap. 6). In the following account I will firstly discuss cycles according to the climatic zones, then discuss multi-year cycles and then some special adaptations to unpredictable or extreme environments. The focus of this chapter is on gonadal, mating and nesting cycles, and their timing.

Amphibia-reptilia, 1981

Tortoises (Testudo hermanni hermanni) which are cooled down to 5 °C show a considerable higher ox... more Tortoises (Testudo hermanni hermanni) which are cooled down to 5 °C show a considerable higher oxygen consumption during the first week at this temperature in June and August than in November, which is the time when hibernation normally starts. Prolonging the low temperature conditions in spring leads to an increase in oxygen consumption. The blood glucose concentration is reduced during normal hibernation, but can rise quickly when the animals are disturbed. During cold torpor induced in June and August the blood glucose concentration is drastically increased. The results support the hypothesis according which hibernation in the tortoise is the result of a metabolic preparation in autumn and cannot be induced artificially during spring and summer. Endogenous factors are involved in the termination of the physiological phenomena of hibernation in spring.

Amphibia-reptilia, 1981

Testudo hermanni hermanni shows a post-nuptial testicular cycle with the peak of spermiogenesis i... more Testudo hermanni hermanni shows a post-nuptial testicular cycle with the peak of spermiogenesis in July and August. Endogenous factors as well as the rising temperature initiate the beginning of spermatocytogenesis in spring. The temperature threshold for the initiation of complete spermiogenesis lies between 21 and 26 °C of constant environmental temperature. Gonadal regression in autumn is the result of low temperature and short photoperiod together with an endogenous readiness. From June to August low temperature (5 °C) and constant darkness did not induce gonadal regression.

International Zoo Yearbook, 1988

Chelonian Conservation and Biology, 2006

Gonads and accessory ducts of 140 live, captive-raised juvenile Erymnochelys madagascariensis (72... more Gonads and accessory ducts of 140 live, captive-raised juvenile Erymnochelys madagascariensis (72-375 g body mass) of 1-3 years of age as well as those of some wild, larger turtles were investigated by endoscopy. The gonads of all examined turtles could be visualized by endoscopy and unambiguously identified as testes or ovaries. Of the captive-raised juveniles, 75% were females and 25% males. One-year-old females have small, thin, transparent ovaries with transparent, whitish follicles and thin oviducts. Follicles in 2-year-old females increase in number and appear as transparent, whitish flat discs and the oviducts become broader and transparentwhitish to whitish. Three-year-old females have yellowish-whitish follicles and whitish oviducts. Juvenile females over 0.5 kg body mass have yellow follicles and white oviducts. A 1-year-old male and 2 small 2-year-old males show testes of rose pink-whitish color and transparent epididymes. Other 2-year-old males have yellowish-orange testes and in males. 130 g body mass, the epididymes turn transparent-whitish. Three-year-old males have yellow-orange testes that are thicker and rounder, and whitish epididymes with meandering ducti epididymides. The developmental changes of juvenile reproductive tracts seem to depend more on age than on size.

General and Comparative Endocrinology, Jun 1, 1981

Abstract Males of the tortoise Testudo h. hermanni of a natural population in Montenegro, Yugosla... more Abstract Males of the tortoise Testudo h. hermanni of a natural population in Montenegro, Yugoslavia, and captive ones in an outside area in Vienna, Austria, were used for a comparative investigation. Throughout the year testis and epididymis were examined histologically and the activity of β- N -acetylglucosaminidase in these organs was determined biochemically and histochemically. The activity of this enzyme increased in the testis and epididymis with the appearance of differentiated spermatozoa during summer. In the epithelium of the ductuli epididymides there were segments with very high and others with very low activity of this enzyme at that time. In the testis only moderate activity of 3β-hydroxysteroid dehydrogenase was found from January to June in the Leydig cells and at any time of the year in the Sertoli cells. The concentration of testosterone in blood plasma was maximal during summer, the main period of spermiogenesis, minimal during winter, and between these levels in spring, during the main mating period. The high concentration of plasma testosterone in summer may have been necessary for the activation of β- N -acetylglucosaminidase in the ductuli epididymides at the time of the passage of spermatozoa.

Journal of Zoology, Mar 1, 1993

The reproductive organs of logn‐term captive females and of wild females of the western swamp tor... more The reproductive organs of logn‐term captive females and of wild females of the western swamp tortoise, Pseudemydura umbrina, which were taken temporarily into captivity, were studied over several years by ultra‐sound scanning. Pseudemydura umbrina, a critically‐endangered species, is active during winter and spring when the ephemeral swamps it inhabits contain water and aestivates during summer and autumn (November to May/June) when the swamps are dry. The vitellogenic growth of ovarian follicles commences during aestivation in summer and continues during autumn and winter. The timing of the vitellogenic cycle is remarkably similar to that of many other Australian chelids and that of many other chelonians of temperate and subtropical regions, but the patterns of energy harvest, storage and allocation to ovarian follicles is different. Ovulation occurs between late September and early November and is preceded by a feeding bout and a sharp increase in female body mass. One clutch of 3–5 eggs (exceptionally of one or two) is laid in November/December. Sub‐adult females show cycles of follicular growth, followed by atresia, for several years before ovulating and laying eggs. Females taken into captivity may miss the following vitelogenic cycle, but captivity does not generally affect vitellogenic cycles. Ovulation and egg production of captive animals is easily suppressed, however, under stress or sub‐optimal food intake in spring. The sensitivity of ovulation to sub‐optimal conditions and the subsequent reabsorption of the yolk material may enhance survival of the reproducing individual during long dry periods in an unpredictable environment.

Zoophysiology, 1999

... The reproductive biology of the chelonia. Post a Comment. CONTRIBUTORS: Author: Kuchling, G. ... more ... The reproductive biology of the chelonia. Post a Comment. CONTRIBUTORS: Author: Kuchling, G. PUBLISHER: Springer (Berlin and New York). SERIES TITLE: YEAR: 1999. PUB TYPE: Book (ISBN 3540630139 ). VOLUME/EDITION: Volume 38. PAGES (INTRO/BODY): xi, 223 ...

The status of Kachuga trivittata is the most precarious of all the endemic turtles in Myanmar. Ka... more The status of Kachuga trivittata is the most precarious of all the endemic turtles in Myanmar. Kachuga trivittata is listed as "endangered" in the 2000 IUCN Red List of Threatened Species. However, the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group & Asian Turtle Trade Working Group (2000) proposed (pp. 160): "Actually a candidate for CR (critical) or EX (extinct), considering that no animals have been reliably recorded since 1935 despite mass trade of riverine turtles from MM (Myanmar) to CN (China)." Fig. 1: Kachuga trivittata female #5, Yadanabon Zoo, July 2003 KACHUGA TRIVITTATA IN CAPTIVITY No live K. trivittata were recorded between 1935 and 2002. Accordingly, until 2002 the species was not represented anywhere in captivity. The first live specimens recorded in Myanmar for 67 years were the two females and one male found in the Mahamuni Paya pond in July/August 2002 (Kuchling et al., in press; see Table 1). These three specimens were transferred to Yadanabon Zoo in Mandalay. However, there were no suitable facilities (ponds) for the maintenance of river turtles at Yadanabon Zoo and the turtles were moved several times between the elephant bathing pond and a preliminary ground pond. Unfortunately, the male (# 4) disappeared during November or December 2002. The larger female (#5) had a severe inflammation of the knee joint with osteomyelitis in January 2003, but recovered fully after antibiotic treatment.

Springer eBooks, 1999

The major threats to the persistence of chelonian species around the world are over-exploitation ... more The major threats to the persistence of chelonian species around the world are over-exploitation by humans, habitat loss and environmental degradation. That exploitation for food can extirpate chelonians was already convincingly demonstrated as early as the eighteenth century, when six out of eight species of giant tortoises on Indian Ocean islands were slaughtered and eaten until extinct (one more followed in the nineteenth century). Today, the IUCN-SSC (the World Conservation Union Species Survival Commission) classifies 38% of the world’s chelonians as threatened: 4% as critically endangered, 11% as endangered and 23% as vulnerable. Chelonians, thus, contain a much higher percentage of threatened taxa than birds and mammals, of which, respectively, 11 and 25% are threatened (Baillie 1996).