Time Of Hatching Research Articles

Climate-induced life cycle and growth variations of neon flying squid (Ommastrephes bartramii) in the North Pacific Ocean

Climate change has had large impacts on marine animals, including neon flying squid Ommastrephes bartramii (O. bartramii) in the North Pacific Ocean. O. bartramii statoliths from 2012, 2015, and 2016 were used to evaluate the variations in life cycle events. The relationship between mantle length and body weight showed significant differences between years and gender. The oldest squid was collected in 2016 at 271 days old, further proving that O. bartramii has nearly a 1-year life span. The hatching season ranged from December to May and the peak hatching time in 2015 was one-half month later than in 2012 and 2016. Growth rates varied with environmental factors such as sea surface temperature (SST) and chlorophyll a concentration (chl. a), indicating that higher SST and chl. a concentrations led to faster growth. An extreme El Niño event with lower SST in 2015 also led to younger age class and slower growth rates. The occurrence of differences in body size and growth rates between years, caused by the interannual variations of environmental factors, makes it necessary to use separate growth curves for different years when analyzing North Pacific O. Bartramii populations.

Timing of increased temperature sensitivity coincides with nervous system development in winter moth embryos.

ABSTRACTClimate change is rapidly altering the environment and many species will need to genetically adapt their seasonal timing to keep up with these changes. Insect development rate is largely influenced by temperature, but we know little about the mechanisms underlying the temperature sensitivity of development. Here, we investigate seasonal timing of egg hatching in the winter moth, one of the few species which has been found to genetically adapt to climate change, likely through selection on temperature sensitivity of egg development rate. To study when during development winter moth embryos are most sensitive to changes in ambient temperature, we gave eggs an increase or decrease in temperature at different moments during their development. We measured their developmental progression and time of egg hatching, and used fluorescence microscopy to construct a timeline of embryonic development for the winter moth. We found that egg development rate responded more strongly to temperature once embryos were in the fully extended germband stage. This is the phylotypic stage at which all insect embryos have developed a rudimentary nervous system. Furthermore, at this stage, timing of ecdysone signaling determines developmental progression, which could act as an environment dependent gateway. Intriguingly, this may suggest that, from the phylotypic stage onward, insect embryos can start to integrate internal and environmental stimuli to actively regulate important developmental processes. As we found evidence that there is genetic variation for temperature sensitivity of egg development rate in our study population, such regulation could be a target of selection imposed by climate change.

Effects of ventilation programme and eggshell thickness on hatchability rate and hatching time of broiler eggs

The aim of the research was to determine whether enrichment of the atmosphere in an incubator with carbon dioxide (CO2) and oxygen (O2) and eggshell thickness (EST) affected embryonic death (ED), hatchability of fertile eggs (HFE) and hatching time (HT). A total of 320 Ross 308 eggs were used and the experiment was repeated twice. Eggshell thickness was classified as thin (<31 μm), medium (31 - 32 μm) and thick (>32 μm). The incubators were operated with their internal atmosphere enriched with CO2 (1.57% CO2; 20.23% O2) or O2 (0.50% CO2; 22.44% O2). Embryonic death, HFE and HT data were monitored at three periods, namely early (<486 hours), middle (486 - 492 hours), and late (492 - 510 hours). Early ED, late ED and hatchability of fertile eggs were not affected by EST or by the incubator’s internal atmosphere (P >0.05). Thus, O2 supplementation to the incubator was deemed unnecessary at 822 m altitude. There was a highly significant interaction between EST and HT. Eggs with shells 31 to 32 μm thick hatched at an appreciably greater rate between 486 and 492 hours of incubation (17%) than eggs with thicker (0.6%) or thinner (0.4%) shells in both the CO2 and O2 enriched atmospheres. The hatching rate was significantly higher in the eggs with an intermediate EST than in thick-shelled eggs. A greater proportion of eggs hatched at the late HT as opposed to earlier, regardless of EST.

Embryonic exposure to predation risk and hatch time variation in fathead minnows

Organisms are exposed to a wealth of chemical information during their development. Some of these chemical cues indicate present or future dangers, such as the presence of predators that feed on either the developing embryos or their nearby parents. Organisms may use this information to modify their morphology or life-history, including hatching timing, or may retain information about risk until it gains relevance. Previous research has shown predation-induced alterations in hatching among embryonic minnows that were exposed to mechanical-injury-released alarm cues from conspecific embryos. Here, we test whether minnows likewise hatch early in response to alarm cues from injured adult conspecifics. We know that embryonic minnows can detect adult alarm cues and use them to facilitate learned recognition of predators; however, it is unknown whether these adult alarm cues will also induce a change in hatching time. Early hatching may allow animals to rapidly disperse away from potential predators, but late hatching may allow animals to grow and develop structures that allow them to effectively escape when they do hatch. Here, we found here that unlike embryonic fathead minnows (Pimephales promelas) exposed to embryonic cues, embryonic minnows exposed to adult alarm cues do not exhibit early hatching. The ability of embryos to recognize adult alarm cues as a future threat, but not a current one, demonstrates sophisticated ontogenetic specificity in the hatching response of embryonic minnows.

Embryo-to-embryo communication facilitates synchronous hatching in grasshoppers

Synchronous hatching within single egg clutches is moderately common in locusts and other insects and can be mediated by vibrational stimuli generated by adjacent embryos. However, in non-locust grasshoppers, there has been little research on the patterns of egg hatching and the mechanisms controlling the time of hatching. In this study, the hatching patterns of six grasshoppers (Atractomorpha lata, Oxya yezoensis, Acrida cinerea, Chorthippus biguttulus, Gastrimargus marmoratus, and Oedaleus infernalis) were observed under various laboratory treatments. Under continuous illumination and a 25/30°C thermocycle, the eggs of these grasshoppers tended to hatch during the first half of the daily warm period. Eggs removed from egg pods and cultured at 30°C tended to hatch significantly earlier and more synchronously when kept in groups vs. singly. In general, eggs hatched earlier when egg group size was increased. Egg hatching was stimulated by hatched nymphs in some species, but not in others. In all species, two eggs separated by several millimeters on sand hatched less synchronously than those kept in contact with one another, but the hatching synchrony of similarly separated eggs was restored if they were connected by a piece of wire, suggesting that a physical signal transmitted through the wire facilitated synchronized hatching. In contrast, hatching times in the Emma field cricket, Teleogryllus emma, which lays single, isolated eggs, were not influenced by artificial clumping in laboratory experiments. These results are discussed and compared with the characteristics of other insects.

Effect of simulated sudden thunderstorm flood on the early stage development of Japanese flounder Paralichthys olivaceus

The early stage development response of Japanese flounder to simultaneous gradual drop in salinity (34, 24, 14 psu) and temperature with different durations (1, 3, 6 h) were investigated to gain better understanding of the decrease in natural stock and its relationship to global weather pattern changes. A series of small-scale laboratory set-up containing six replicates per treatment using plastic microplates were each stocked with 78 fertilized Japanese flounder eggs in gastrula stage and exposed to gradual salinity and temperature drop conditions followed by the recovery to ambient conditions. Two-way ANOVA showed that salinity (S) and exposure time (E) individually or as a combination (S × E) had no effects on hatching success rate, percentage of abnormality, pre-anal length, final total length at 4 days post-hatch (dph) and survival rate at 4 dph. Onset hatching time, newly hatched larvae total length and yolk sac volume showed individual effects but recorded no interaction effects between S and E. Results obtained indicated that the early developmental stages of Japanese flounder were quite resilient to the stressful conditions subjected on them.

Effects of Hatching and Feeding Times and Hatchery Temperature on Body and Organs’ Weight of Post-hatched Chicks

BACKGROUND: In commercial hatcheries, chicks are deprived of feed and water for up to 72 h, which is a det-rimental effect on growth performance. OBJECTIVES: Two experiments were designed to investigate the effect of hatching parameters and feeding time on the body and organ weights of chickens. METHODS: In the first experiment, 300 of both early- and later-hatched broiler chicks received feed immedi-ately after hatching or 48 h later and were divided into four experimental groups. The body and internal organ weights of chicks were determined for up to seven days. In the second study, 370 embryos, which were incubated in a setter until the 18th day, were transferred to two hatchers, which differed their air and eggshell temperatures. Then, hatching and post-hatched parameters were followed. RESULTS: Comparing early-hatched chicks, later-hatched chicks had significantly greater weight (p <0.05) on day 3 and better yolk utilization and higher relative liver and intestine (p <0.01) weights on day 2. However, early-fed chicks indicated significantly higher body weight (p <0.0001) until day 7 and early yolk utilization and higher internal organ weights than later-fed chicks. In the second experiment, when the air temperature of hatcher A (control) was kept at 37.5oC, its eggshell temperature was determined at 38.5oC, while the eggshell temperature of hatcher B was optimized at 37.5oC, and its air temperature showed 36.5oC. Earlier hatchability was higher in the control hatcher (46.8%) than hatcher B (27.1%), but later hatchability was reversed. However, final hatchability was lower in hatcher B (96.6%) than the control hatcher (98.3%). CONCLUSIONS: Later-hatched and early-fed chicks showed greater body and internal organ weights, indicating better maturation of these chicks. The results of the second study indicated that the hatching window could be shorter and also shifted to the end of the incubation time by reducing the egg temperature.

Effect of high eggshell temperature during the early period of incubation on hatchability, hatch time, residual yolk, and first-week broiler performance1

During incubation, temperature is the main environmental condition affecting the hatchability and chick quality. The effect of high temperature after the first week of incubation to hatching has been widely investigated. However, very little is known during the early period of incubation. This study was conducted to investigate the effect of increased eggshell temperature ( EST ) during the first 6 embryonic d of incubation (E) on hatchability, hatch time, and first-week broiler performance. A total of 1,680 hatching eggs were divided randomly into 4 treatment groups were as follows: Control (37.8°C), High EST (38.6°C) from E0 to E3, E3 to E6, and E0 to E6. The EST was maintained at 37.8°C from E6 onward in all groups. Fertile hatchability was significantly better in eggs maintained at the control temperature (37.8°C EST through incubation) and at 38.6°C EST from E0 to E3 (High E0-E3) compared to eggs exposed to an EST of 38.6°C from E3 to E6 (HighE3-E6) and E0 to E6 (HighE0-E6) of incubation ( P < 0.05) due to decreased early embryonic mortality ( P < 0.05). The average hatch time differed among all treatments, with the earliest hatch time for HighE0-E6 followed by the HighE0-E3, HighE3-E6, and Control groups ( P < 0.01). Yolk free body mass ( YFBM ) and residual yolk sac ( RYS ) weight were not significantly affected by high EST (38.6°C) during the first 6 d of incubation. At 7 d of age, the HighE0-E3 and Control groups were found to have greater BW than the other 2 groups ( P < 0.05). No significant difference was found for feed consumption ( FC ), feed conversion ratio ( FCR ), or mortality among the treatments for 7 d ( P > 0.05). These results suggest that compared with the control condition, the exposure of eggs to 38.6°C EST from E0 to E6 or from E3 to E6 of incubation shortened the hatch time but decreased fertile hatchability and the first week BW ( P < 0.05). However, compared with the control temperature, increased EST during the first 3 d of incubation did not impact hatchability, percentage of second-grade chicks and first-week broiler performance ( P > 0.05), but chicks hatched earlier ( P < 0.05).

Research Note: The effects of chick pipping location on broiler live performance

The objective of this study was to determine the effects of chick pipping location on live broiler performance. A total of 1,350 hatching eggs were collected from a commercial flock of Ross 308 at 38 wk of age. Eggs were incubated with either their large end up (LEU) or small end up (SEU). After transfer on d 19, the air cell area of each fertile egg was marked with a marker pen on the egg surface with a candling light and monitored every 6 h during the hatching period to accurately determine the location of the pip hole. Chicks were classified into 3 groups: 1) egg position LEU and pipped through the air cell (LAC); 2) egg position SEU and pipped through the air cell (SAC); and 3) egg position SEU and pipped through the small end of the egg, not through the air cell (SSE). Individual BW was recorded at placement and at 7, 21, and 35 d of age. Feed consumption was also determined at 7, 21, and 35 d of age. The feed conversion ratio (FCR) was calculated on a pen basis for the same time periods. Mortality was recorded twice a day, and percent mortality was calculated throughout the study. The European production efficiency index (EPEI) was also calculated.All chicks that hatched from LEU eggs emerged from the egg at the region of the air cell; however, only 10.3% of chicks from the SEU position hatched through air cells. Pipping location greatly affected the hatch time. Chicks pipped through the air cell location hatched earlier than the chicks pipped without using air cell (P < 0.001). The initial BW at placement was higher in the LAC and SAC groups than in the SSE group (P < 0.001). This BW difference was still evident in the subsequent growing period, and the chicks that pipped the SSE exhibited a lower (P = 0.059) BW at 35 d. Additionally, the SSE group had a poorer FCR and numerically higher mortality than the other two groups at 35 d. Overall, the EPEI values in the LAC and SAC groups were higher than that in the SSE group at 35 d (P < 0.001). We concluded that broiler performance was negatively affected when the chicks pipped and hatched without using air cells.

A Systematic Review of the Effects of Temperature on Anopheles Mosquito Development and Survival: Implications for Malaria Control in a Future Warmer Climate.

The rearing temperature of the immature stages can have a significant impact on the life-history traits and the ability of adult mosquitoes to transmit diseases. This review assessed published evidence of the effects of temperature on the immature stages, life-history traits, insecticide susceptibility, and expression of enzymes in the adult Anopheles mosquito. Original articles published through 31 March 2021 were systematically retrieved from Scopus, Google Scholar, Science Direct, PubMed, ProQuest, and Web of Science databases. After applying eligibility criteria, 29 studies were included. The review revealed that immature stages of An. arabiensis were more tolerant (in terms of survival) to a higher temperature than An. funestus and An. quadriannulatus. Higher temperatures resulted in smaller larval sizes and decreased hatching and pupation time. The development rate and survival of An. stephensi was significantly reduced at a higher temperature than a lower temperature. Increasing temperatures decreased the longevity, body size, length of the gonotrophic cycle, and fecundity of Anopheles mosquitoes. Higher rearing temperatures increased pyrethroid resistance in adults of the An. arabiensis SENN DDT strain, and increased pyrethroid tolerance in the An. arabiensis SENN strain. Increasing temperature also significantly increased Nitric Oxide Synthase (NOS) expression and decreased insecticide toxicity. Both extreme low and high temperatures affect Anopheles mosquito development and survival. Climate change could have diverse effects on Anopheles mosquitoes. The sensitivities of Anopeheles mosquitoes to temperature differ from species to species, even among the same complex. Notwithstanding, there seem to be limited studies on the effects of temperature on adult life-history traits of Anopheles mosquitoes, and more studies are needed to clarify this relationship.

Hatch timing of two subarctic salmonids in a stream network estimated by otolith increments

AbstractHatch timing in autumn‐spawning stream salmonids is poorly understood in the subarctic region because snow cover prevents direct sampling of cryptic early life stages. Otolith micro‐increment analysis was used to infer hatch dates of white‐spotted charr Salvelinus leucomaenis (Pallas) and masu salmon Oncorhynchus masou (Brevoort) in a mainstem‐tributary network in northern Japan. Accuracy and precision were validated by ageing hatchery individuals with known hatch date ranges. In July 2018, 93 wild young‐of‐the‐year white‐spotted charr and 81 masu salmon were collected and aged. Masu salmon hatched, on average, 24 days earlier (mean = February 8) than white‐spotted charr (March 4), and hatch dates spanned a minimum of 2 months for each species. In masu salmon, hatch dates of individuals collected in the mainstem were nearly 3 weeks earlier than those in a tributary. This study provided knowledge on intra‐ and inter‐specific variation in hatch timing of native salmonids in a subarctic stream network.

Trophic transfer and toxicity of heavy metals from dengue mosquito Aedes aegypti to predator dragonfly Tramea cophysa.

Heavy metal pollution in aquatic habitats can be detrimental to both prey and predators in a food web. To investigate the potential for bio-transfer and bioaccumulation of heavy metals between specific trophic levels, 3rd instar larvae of Aedes aegypti were exposed to mercury (Hg), lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) for three consecutive generations and fed to dragonfly (Tramea cophysa) nymphs. Exposure to Hg caused the highest mortality in A. aegypti larvae and T. cophysa nymphs. Bioaccumulation and life-history parameters of A. aegypti, including egg hatching time, larval and pupal duration, male and female life span, and fecundity, were also evaluated after metals exposure. All life-history parameters except larval duration were significantly affected by heavy metal treatments. Bioaccumulation of metals in A. aegypti larvae and adults gradually and significantly increased from 1st to 3rd generation. To the best of our knowledge, this is the first study describing the acute toxicity of heavy metals to mosquitoes. Our study shows that heavy metals cause dietary toxicity to an aquatic predator, dragonfly, via trophic transfer, which could have considerable consequences on aquatic ecosystems.

Effects of hatch window and nutrient access in the hatcher on performance and processing yield of broiler chicks reared according to time of hatch

The effects of hatch window and hatching basket nutrient availability on organ weights, performance, and processing yield of broilers were investigated. Eggs were hatched in illuminated hatchers. At the end of each hatch window period (HWP), hatched chicks were placed into control (CTL) hatching baskets with no nutrients or baskets providing access to feed and water (FAW). This resulted in 6 treatments in a factorial arrangement of 3 HWP (early, middle, or late) and 2 basket types (CTL or FAW). Chicks remained in experimental baskets until 504 h and were then subjected to a 4 h holding period at the hatchery without nutrient access. Subsequently, 1,500 hatched chicks were reared in floor pens for 42 d with 5 replicate pens per treatment. Common diets and water were provided ad libitum. Bird weights and feed consumption were recorded weekly. Individual bird weights were taken at 21 and 42 d. At 43 d, 14 males from each pen were processed. There was an interaction between HWP and basket type on placement BW (P = 0.028) and BW change in the hatcher (P < 0.001). The HWP influenced BW at hatch (P = 0.007), 7 d (P < 0.001), and 14 d (P < 0.001) and FI at 7 d (P < 0.001) and 14 d (P = 0.002). Chicks from FAW baskets were heavier (P < 0.001) than those from CTL baskets at 7 d; afterward, they were similar (P > 0.05) in BW. Yolk and liver weights were similar (P > 0.05) between basket treatments at 3 d posthatch. No differences (P > 0.05) in FCR, mortality, or processing were observed between basket treatments. Interestingly, early hatching chicks were lightest at hatch but subsequently had higher FI and BWG. These findings indicate that hatcher nutrient access may reduce weight loss in the hatcher, especially for early hatching chicks, but had no influence on subsequent performance or processing yields beyond 7 d.

The formation of a hatching line in the serosal cuticle confers multifaceted adaptive functions on the eggshell of a cicada

Insect eggshells must meet various demands of developing embryos. These demands sometimes conflict with each other; therefore, there are tradeoffs between eggshell properties, such as robustness and permeability. To meet these conflicting demands, particular eggshell structures have evolved in diverse insect species. Here, we report a rare eggshell structure found in the eggshell of a cicada, Cryptotympana facialis. This species has a prolonged egg period with embryonic diapause and a trait of humidity-inducible hatching, which would impose severe demands on the eggshell. We found that in eggs of this species, unlike many other insect eggs, a dedicated cleavage site, known as a hatching line, was formed not in the chorion but in the serosal cuticle. The hatching line was composed of a fine furrow accompanied by ridges on both sides. This furrow-ridge structure formed in the terminal phase of embryogenesis through the partial degradation of an initially thick and nearly flat cuticle layer. We showed that the permeability of the eggshell was low in the diapause stage, when the cuticle was thick, and increased with degradation of the serosal cuticle. We also demonstrated that the force required to cleave the eggshell was reduced after the formation of the hatching line. These results suggest that the establishment of the hatching line on the serosal cuticle enables flexible modification of eggshell properties during embryogenesis, and we predict that it is an adaptation to maximize the protective role of the shell during the long egg period while reducing the barrier to emerging nymphs at the time of hatching.

The effect of delayed feeding post-hatch on caeca development in broiler chickens

ABSTRACT 1. Broiler chicks are frequently deprived of food up to 72 h due to uneven hatching rates, management procedures and transportation to farms. Little is known about the effect of delayed feeding due to extended hatching times on the early neonatal development of the caeca. Therefore, the objective of this study was to investigate the developmental changes and effects of a 48-h delay in feed access immediately post-hatch (PH) on the caeca. 2. After hatch, birds (Ross 708) were randomly divided into two treatment groups (n = 6 battery pen/treatment). One group (early fed; EF) received feed and water immediately after hatch, while the second group (late fed; LF) had access to water but had delayed access to feed for 48 h. Contents averaging across all regions of the caeca were collected for mRNA expression as well as for histological analysis at −48, 0, 4 h PH and then at 1, 2, 3, 4, 6, 8, 10, 12 and 14 days PH. 3. Expression of MCT-1 (a nutrient transporter), Cox7A2 (related to mitochondrial function) IgA, pIgR, and ChIL-8 (immune function) genes was affected by delayed access to feed that was dependent by the time PH. Expression of immune and gut barrier function-related genes (LEAP2 and MUC2, respectively) was increased in LF group. There was no effect of feed delay on expression of genes related to mitochondrial functions in the caeca, although developmental changes were observed (ATP5F1B, Cox4|1). Caecal mucus and muscle thickness were affected by delayed access to feed during caeca development. 4. The data suggested a limited effect of delayed feed access PH on the developmental changes in caecal functions. However, the caeca seemed to be relatively resistant to delayed access to feed early PH, with only a few genes affected.

Incubation of Oryzias woworae Eggs at Different Temperature on Embryo Development and Hatching Performance

Oryzias woworae is one of Muna Island's endemic fish, Sulawesi, which needs to be developed in cultivation and can be used as ornamental fish with high economic value. However, information on fish farming is not yet well available, especially at egg incubation temperatures. This study aims to determine the optimal temperature of the incubation water medium for the hatching performance of O. woworae eggs. The study used experimental methods with the treatment of differences in egg incubation temperatures at 24-26°C (temperature fluctuations in the laboratory), 24°C, 28°C and 32°C. The research parameters were analyzed descriptively, namely embryogenesis, hatching time, and hatching rates. The results showed that differences in incubation temperature affected the embryogenesis of O. woworae eggs. The obtained fastest time for hatching eggs O. woworae at a temperature of 32°C with six days 5 hours 49 minutes and 100% hatching. The egg incubation temperature 24-26°C is the lowest hatching time and hatching rate, nine days 11 hours 38 minutes and 53.33%. The use of 32°C in the incubation medium is the optimal temperature to accelerate embryogenesis and the hatching rate of O. woworae eggs.

Modeling the dispersal of polar cod (Boreogadus saida) and saffron cod (Eleginus gracilis) early life stages in the Pacific Arctic using a biophysical transport model

Polar cod (Boreogadus saida) and saffron cod (Eleginus gracilis) are the most abundant and ecologically important forage fishes in the Pacific Arctic marine ecosystem, yet little is known about their spawning locations or the habitats occupied by their early life stages (ELS). We developed a biophysical transport model coupled to a Pan-Arctic hydrodynamic ocean circulation model to identify potential spawning locations and examine connectivity between the northern Bering, Chukchi, and Beaufort seas. We simulated the growth and transport of newly hatched polar cod and saffron cod larvae until the early juvenile stage (to 45 mm in length) using circulation model hindcasts from 2004 to 2015. Analyses identified species-specific differences in dispersal trajectories, despite similar hatch times and locations. Strong interannual variability in growth and dispersal was linked to several global-scale climate indices, suggesting that larval growth and transport may be sensitive to environmental perturbations. Results show that polar cod spawned in the northern Chukchi Sea may be an important source of larvae for the Beaufort Sea and Arctic Basin, while observed larval aggregations in the Chukchi Sea likely originated in the northern Bering and southern Chukchi seas. This study provides new information about potential spawning times and locations for polar cod and saffron cod in the Pacific Arctic and helps to identify important ELS habitat. This knowledge can help improve the management of these species and, by examining how larval connectivity changes in response to changing environmental conditions, improve our ability to anticipate how these species may respond in a rapidly changing Arctic.

Femoral mechanical performance of precocial and altricial birds: a simulation study

BackgroundAs the major load-bearing structures, bones exhibit various properties related to mechanical performance to adapt to different locomotor intensities. The habits and ontogenetic changes of locomotion in animals can, thus, be explored by assessing skeletal mechanical performance.MethodsIn this study, we investigated the growing femoral mechanical performance in an ontogenetic series of Cabot’s Tragopans (Tragopan caboti) and Pigeons (Columba livia domestica). Micro-computed tomography-based finite element analysis was conducted to evaluate the stress, strain, and strain energy density (SED) of femora under axial and radial loading.ResultsFemora deflected medio-laterally and dorso-ventrally under axial and radial loading, respectively. Femora deformed and tensed more severely under radial loading than axial loading. In adult individuals, Cabot’s Tragopans had lower strain and SED than pigeons. During ontogeny, the strain and SED of pigeons decreased sharply, while Cabot’s Tragopans showed moderately change. The structural properties of hatchling pigeons are more robust than those of hatchling Cabot’s Tragopans.ConclusionsLimb postures have dominant effect on skeletal deformation. The erect posture is preferred by large mammals and birds to achieve a high safety factor of bones during locomotion. Adult Cabot’s Tragopans have stronger femora than pigeons, reflecting a better bone adaption to the terrestrial locomotion of the studied pheasant species. Changes in strain and SED during growth reflect the marked difference in locomotor ability between precocial and altricial hatchlings. The femora of hatchling Cabot’s Tragopans were built with better energy efficiency than deformation resistance, enabling optimized mechanical performance. In contrast, although weak in mechanical function at the time of hatching, pigeon femora were suggested to be established with a more mature structural design as a prerequisite for rapid growth. These results will be helpful for studies regarding developmental patterns of fossil avian species.

Effects of water quality on the reproductive behavior and capacity of Andrias davidianus under tourism disturbance.

Water quality under tourism disturbance was simulated through controlling the water intake of the ecological breeding ponds of Chinese giant salamander (Andrias davidianus, CGS). Both the reproductive behavior (oviposition and parental care) and capacity (relative egg production, fertilizing rate of eggs, and hatching rate of fertilized eggs) of CGS were examined using a real-time infrared digital monitoring system. The relationships among reproductive behavior, capacity, and the corresponding parameters of water quality were analyzed, to understand how water quality under tourism disturbance would affect the reproductive behavior and capacity of CGS. The examined oviposition behavior and capacity of CGS showed no variation in general, but the parental care behavior such as tail fanning and agitation time of the male CGS were prolonged significantly in the groups under tourism disturbance. Such prolonged behaviors would help increase the content of dissolved oxygen (DO) to meet the high demands of DO during embryonic development of CGS. In addition, the overall hatching time of fertilized eggs was increased significantly under disturbance conditions when it compared with the control, which would ensure the overall hatching rate among these comparative groups unaffected. In summary, the prolongations of some reproductive behavior (tail fanning and agitation of the male CGS and the development time of fertilized egg) would be a kind of positive actions of CGS in response to the changes of water quality resulted from tourism disturbance.

Dehydration-Induced Mortality and Premature Hatching in Gliding Treefrogs with Even Small Reductions in Humidity

Climate change is affecting rainfall patterns and increasing dry spells in the tropics. Although many environmental conditions can affect the hatching timing and survival of amphibian embryos, increased variation in rainfall and humidity can have particularly strong effects on species facing higher risk from dehydration, such as those with terrestrial eggs. Thus, it is important to understand how these environmental changes may affect the development, behavior, and immediate and long-term survival of amphibian embryos. We investigated whether Gliding Treefrog embryos (Agalychnis spurrelli) adaptively shift their hatching timing in response to dehydration risk, at the cost of smaller hatchling size. We raised embryos under three humidity levels and assessed egg and clutch hydration, hatching timing, and egg mortality. Mean humidity of 92% in Experiment I led to over 98% egg mortality by dehydration. A decrease from over 99 to 96% mean relative humidity in Experiment II induced premature hatching and reduced hatchling size across ages. Both clutch thickness and egg size increased at 99% and decreased at 96% humidity. Our results suggest that embryos of A. spurrelli are extremely dependent on consistent precipitation and particularly vulnerable to climate change. Although we did not directly measure differences in hatchling fitness, our results and previous findings suggest that small, premature hatchlings of A. spurrelli from dehydrated eggs would suffer higher mortality as tadpoles, thus embryos' self-defense against dehydration likely carries a delayed cost. These findings add to our understanding of how predicted climate changes may impact anuran early life stages.