Crocodylus johnstoni in the McKinlay River Area N. T, VI.* Nesting Biology

1983 ◽  
Vol 10 (3) ◽  
pp. 607 ◽  
Author(s):  
GJW Webb ◽  
SC Manolis ◽  
R Buckworth
Keyword(s):  
Clutch Size ◽  
Incubation Temperature ◽  
Management Program ◽  
Alligator Mississippiensis ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
Nesting Biology ◽  
Crocodylus Johnstoni ◽  
Hatching Time ◽  
Potential Strategy

In the McKinlay River area most female C. johnstoni mature at 74-78 cm snout-vent length (SVL), and 11-14 years of age, whereas maies are about 87 cm SYL and 16-17 years of age. Adult sex ratios in the field are lM:3-4F. There is a well defined, brief nesting period in late August and early September, and the nests are typical 'hole' nests excavated in sand or other friable substrates close to permanent water. Mean clutch size is 13.2 � 3.2 eggs (� SD) and mean egg dimensions are: length 6.64 � 0.26 cm, breadth 4.19 � 0.19 cm and weight 68.2 � 8.0 g. There is a variable but significant increase in egg size with clutch size, and large clutches of large eggs tend to be laid earlier in the nesting season than small clutches of small eggs. From 2 to 4% of eggs are infertile. Nest temperatures show considerable daily variation and baseline levels differ between shaded and exposed nest sites. Incubation times are temperaturedependent and range from 9 to 14 weeks. Females excavate nests at hatching time, but attend the nests little, ifat all, during incubation. Hatchlings are 11.2 � 0.5 cm SVL and weigh 42.0 � 6.1 g. Formulae for predicting egg and hatchling dimensions from each other are presented. A preliminary method for aging C. johnstoni embryos is described. Artificial incubation at 26�, 30� and 34�C, respectively, resulted in 0, 63% and 21% survival; at 26 and 34�C physically deformed embryos were common. Hatching success is correlated with the age at which eggs are transported to incubators. Sex determinantion is influenced by incubation temperature, and at temperatures we tested between 26 and 34�C, females predominated; males were produced at 31-32�C. Histological examination of females from high-temperature incubation (34�C) indicated slight hermaphroditic tendencies in two of 35 animals examined; their status remains to be clarified. The temperature-sensitive period for sex determination appears to be between 20 and 57 days of age (30�C equivalent ages), but this may well vary with incubation temperature, as in Alligator mississippiensis. Egg losses due to predators (particular varanid lizards) were estimated as 64%, although they may have been increased by our interference with nests. Eggs are also lost to flooding and overheating, and a 60-70% annual egg mortality may be common. In one experiment, hatchling mortality was estimated at 98% within the first year. An egg and/or hatchling harvest balanced by a proportional return to the wild of raised 1-year-olds (5% and 10% of eggs and hatchlings collected respectively) is a potential strategy through which sustained-yield harvesting could be introduced into a conservation-management program.

scholarly journals Improved genome assembly of American alligator genome reveals conserved architecture of estrogen signaling

2016 ◽  
Author(s):  
Edward S. Rice ◽  
Satomi Kohno ◽  
John St. John ◽  
Son Pham ◽  
Jonathan Howard ◽  
...  
Keyword(s):  
Sex Determination ◽  
Genome Assembly ◽  
Critical Period ◽  
Incubation Temperature ◽  
Current Model ◽  
Alligator Mississippiensis ◽  
Estrogen Signaling ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
American Alligator

AbstractThe American alligator, Alligator mississippiensis, like all crocodilians, has temperature-dependent sex determination, in which the sex of an embryo is determined by the incubation temperature of the egg during a critical period of development. The lack of genetic differences between male and female alligators leaves open the question of how the genes responsible for sex determination and differentiation are regulated. One insight into this question comes from the fact that exposing an embryo incubated at male-producing temperature to estrogen causes it to develop ovaries. Because estrogen response elements are known to regulate genes over long distances, a contiguous genome assembly is crucial for predicting and understanding its impact.We present an improved assembly of the American alligator genome, scaffolded with in vitro proximity ligation (Chicago) data. We use this assembly to scaffold two other crocodilian genomes based on synteny. We perform RNA sequencing of tissues from American alligator embryos to find genes that are differentially expressed between embryos incubated at male-versus female-producing temperature. Finally, we use the improved contiguity of our assembly along with the current model of CTCF-mediated chromatin looping to predict regions of the genome likely to contain estrogen-responsive genes. We find that these regions are significantly enriched for genes with female-biased expression in developing gonads after the critical period during which sex is determined by incubation temperature. We thus conclude that estrogen signaling is a major driver of female-biased gene expression in the post-temperature sensitive period gonads.

The temperature-sensitive period (TSP) during incubation of broad-snouted caiman (Caiman latirostris) eggs

2007 ◽  
Vol 28 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Carlos Piña ◽  
Alejandro Larriera ◽  
Pablo Siroski ◽  
Luciano Verdade ◽  
Valentine Lance
Keyword(s):  
Sex Determination ◽  
Egg Laying ◽  
Alligator Mississippiensis ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
American Alligator ◽  
Temperature Dependent ◽  
The Many

AbstractAll crocodiles studied to date exhibit temperature-dependent sex determination. During the many weeks from egg laying to hatch there is a period of 10 to 15 d in the middle third of incubation (in the American alligator) during which the sex of the embryo is irreversibly fixed, referred to as the temperature-sensitive period or TSP. In this work we investigated the TSP in Caiman latirostris eggs incubated at female-inducing and male-inducing temperatures (29° C and 33° C respectively) by switching eggs from 29° C to 33° C and vice versa at timed interval throughout incubation. Compared to Alligator mississippiensis the duration of TSP was longer, and the onset of TSP was at an earlier stage of incubation.

Temperature and non-aromatizable androgens: a common pathway in male sex determination in a turtle with temperature-dependent sex determination?

1996 ◽  
Vol 149 (3) ◽  
pp. 457-463 ◽  
Author(s):  
D Crews ◽  
A R Cantú ◽  
J M Bergeron
Keyword(s):  
Sex Determination ◽  
Incubation Temperature ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
Temperature Dependent ◽  
Dose Response Relationship ◽  
Common Pathway ◽  
Slider Turtle ◽  
Male Sex ◽  
Incubation Temperatures

Abstract This study addressed the hypothesis that, in the red-eared slider turtle, Trachemys scripta, non-aromatizable androgens are the physiological equivalent of temperature in determining male development. In the first experiment, eggs were treated in the middle of the temperature-sensitive period with 1·0 or 10·0 μg androsterone, 5α-dihydrotestosterone, 3α-androstanediol, or 3β-androstanediol, while at an all-male, male-biased, or one of two female-biased incubation temperatures. In the second experiment, eggs were treated with the same dosages of dihydrotestosterone at different stages of embryonic development while at a male-biased, threshold, or a female-biased incubation temperature. Results of experiment one indicated that hormone-induced masculinization is specific to non-aromatizable androgens. Results of experiment two indicated that the sensitivity to dihydrotestosterone corresponds to the temperature-sensitive window during development. Further, there is a dose–response relationship but no apparent synergism between exogenous dihydrotestosterone and incubation temperature. When considered with other research, it is suggested that non-aromatizable androgens and their products are involved in the initiation of male sex determination whereas oestrogens and their aromatizable androgen precursors are involved in the initiation of female sex determination. Journal of Endocrinology (1996) 149, 457–463

PERÍODO DE DESOVA E SUCESSO REPRODUTIVO DO TRACAJÁ Podocnemis unifilis TROSCHEL 1848 (TESTUDINES: PODOCNEMIDIDAE) NA VÁRZEA DA RDSM – MÉDIO SOLIMÕES, BRASIL

2008 ◽  
Vol 2 (1) ◽  
pp. 63-75
Author(s):  
Augusto Fachín Terán ◽  
Eduardo Matheus Von Mülhen
Keyword(s):  
Hatching Success ◽  
Management Program ◽  
Nesting Biology ◽  
Sand Beach ◽  
Podocnemis Unifilis ◽  
Turtle Population ◽  
Nesting Beaches ◽  
Conservation And Management ◽  
Tegu Lizard ◽  
Solimões River

In this study the nesting biology of Podocnem is unifilis was investigated from July to November 1998 at the Mamirauá Sustainable Development Reserve, located in the Solimões river, near Tefé, Amazonas, Brazil. Podocnemis unifilis nested in August and September, with the hatching event occurring in October and November. Nests were excavated in clay soils (67.5%), sand (25%), and leaf litter (7.5%). Hatching success was highest in the sand beach nests and lowest in the clay banks nests. Humans and the tegu lizard (Tupinambis) were the main egg predators. This turtle population can recover only by the protection of nesting beaches, educational programs for the in habitants of the Reserve, participation of the community in the conservation and management program , and permanent guarding of the nesting beaches by Instituto Brasileiro do Meio Ambiente e Dos Recursos Naturais Renováveis-IBAMA authorities.

scholarly journals MATERNAL-ZYGOTIC GENE INTERACTIONS DURING FORMATION OF THE DORSOVENTRAL PATTERN IN DROSOPHILA EMBRYOS

Genetics ◽  
1983 ◽  
Vol 105 (3) ◽  
pp. 615-632 ◽  
Author(s):  
Pat Simpson
Keyword(s):  
Early Embryo ◽  
Drosophila Embryo ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
Mutant Genotype ◽  
Dominant Phenotype ◽  
Zygotic Gene ◽  
Definition Of ◽  
Mutant Phenotypes ◽  
Dominant Lethality

ABSTRACT Maternal-zygotic interactions involving the three genes dorsal (dl), twist (twi) and snail (sna) are described. The results suggest that all three are involved in the process by which the dorsoventral pattern of the Drosophila embryo is established. First, the lethal embryonic mutant phenotypes are rather similar. In homozygous twi or sna embryos invagination of the ventral presumptive mesodermal cells fails to occur, and the resulting embryos are devoid of internal organs. This is very similar to the dominant phenotype described for dl; in the case of dl, however, the effect is a maternal one dependent on the mutant genotype of the female. Second, a synergistic interaction has been found whereby dominant lethality of twi  - or sna-bearing zygotes is observed in embryos derived from heterozygous dl females at high temperature. The temperature sensitivity of this interaction permitted definition of a temperature-sensitive period which is probably that of dl. This was found to extend from approximately 12 hr prior to oviposition to 2— 3 hr of embryogenesis. A zygotic action for the dl gene in addition to the maternal effect was revealed by the finding that extra doses of dl  + in the zygotes can partially rescue the dominant lethality of heterozygous twi embryos derived from heterozygous dl females. Two possible interpretations of the synergism are considered: (1) twi and sna are activated in the embryos as a result of positional signals placed in the egg as a consequence of the functioning of the dl gene during oogenesis and, thus, play a role in embryonic determination. (2) The gene products of dl  + and twi  + (or sna  +) combine to produce a functional molecule that is involved in the specification of dorsoventral pattern in the early embryo.

scholarly journals First evidence for a latitudinal body mass effect in extant Crocodylia and the relationships of their reproductive characters

2020 ◽  
Vol 129 (4) ◽  
pp. 875-887
Author(s):  
Rebecca J Lakin ◽  
Paul M Barrett ◽  
Colin Stevenson ◽  
Robert J Thomas ◽  
Matthew A Wills
Keyword(s):  
Clutch Size ◽  
Body Mass ◽  
Linear Models ◽  
Incubation Temperature ◽  
Mass Effect ◽  
Distribution Patterns ◽  
Egg Mass ◽  
Phylogenetically Independent Contrasts ◽  
Extant Species ◽  
Female Body Mass

Abstract Relationships between distribution patterns and body size have been documented in many endothermic taxa. However, the evidence for these trends in ectotherms generally is equivocal, and there have been no studies of effects in crocodylians specifically. Here, we examine the relationship between latitudinal distribution and body mass in 20 extant species of crocodylians, as well as the relationships between seven important reproductive variables. Using phylogenetically independent contrasts to inform generalized linear models, we provide the first evidence of a latitudinal effect on adult female body mass in crocodylians. In addition, we explore the relationships between reproductive variables including egg mass, hatchling mass and clutch size. We report no correlation between egg mass and clutch size, upholding previously reported within-species trends. We also find no evidence of a correlation between measures of latitudinal range and incubation temperature, contrasting with the trends found in turtles.

scholarly journals Reproductive strategy, egg characteristics and embryonic development of Greenland halibut (Reinhardtius hippoglossoides)

2012 ◽  
Vol 70 (2) ◽  
pp. 342-351 ◽  
Author(s):  
Rosario Domínguez-Petit ◽  
Patrick Ouellet ◽  
Yvan Lambert
Keyword(s):  
Embryonic Development ◽  
Reproductive Strategy ◽  
Biochemical Composition ◽  
Incubation Temperature ◽  
Life Stage ◽  
Early Life Stage ◽  
Greenland Halibut ◽  
Hatching Time ◽  
Greenland Halibut Reinhardtius Hippoglossoides ◽  
Reinhardtius Hippoglossoides

Abstract Domínguez-Petit, R., Ouellet, P., and Lambert, Y. 2013. Reproductive strategy, egg characteristics and embryonic development of Greenland halibut (Reinhardtius hippoglossoides). – ICES Journal of Marine Science, 70: 342–351. Despite the commercial importance of Greenland halibut (GH), important gaps exist in our knowledge of the reproductive and early life stage biology for this species. The present study examined through laboratory experiments the spawning strategy, realized fecundity, egg characteristics, biochemical composition, and embryonic development of GH. The results confirmed the hypothesis that GH is a single-batch spawner producing large eggs, resulting in low realized fecundity. Embryonic development and hatching time are highly dependent on incubation temperature; 50% hatching occurred after 46, 30, and 24 days at 2, 4, and 6°C, respectively. Few changes in the biochemical composition of the eggs are observed during embryonic development. Newly hatched larvae are not well developed, having a large yolk sac, no pigmentation and incomplete development of the jaws. Egg specific density confirmed the mesopelagic distribution of the eggs at sea. However, important buoyancy changes occurring in the last 3–4 days before hatching indicate that larvae hatch higher in the water column. These results are important for understanding advection and dispersion processes of GH eggs and larvae and the connectivity between spawning grounds and nursery areas.

Effect of Incubation Temperature on Development of Crocodylus johnstoni Embryos

1990 ◽  
Vol 63 (5) ◽  
pp. 949-964 ◽  
Author(s):  
P. J. Whitehead ◽  
G. J. W. Webb ◽  
R. S. Seymour
Keyword(s):  
Incubation Temperature ◽  
Crocodylus Johnstoni

scholarly journals Nesting biology and population dynamics of Jankowski's Bunting Emberiza jankowskii in Western Jilin, China

2008 ◽  
Vol 18 (2) ◽  
pp. 153-163 ◽  
Author(s):  
Yun-Lei Jiang ◽  
Wei Gao ◽  
Fu-Min Lei ◽  
Hai-Tao Wang ◽  
Dong-Mei Wan ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Clutch Size ◽  
Nest Success ◽  
Tree Planting ◽  
Hatching Rate ◽  
Nesting Biology ◽  
Individual Level ◽  
Declining Populations ◽  
The Individual ◽  
Western Jilin

AbstractJankowski's Bunting Emberiza jankowskii is endemic to China, Russia and Northern Korea, and was listed as a ‘Vulnerable’ species. The population in Dagang Forestry of western Jilin is one of the small remaining discrete breeding populations in the species' range. Very little information on the nesting biology and population dynamics has previously been published. We studied the nesting biology from 1999 to 2002 and population dynamics of the bunting from 1999 to 2006 (except 2003). A total of 74 nesting attempts were monitored. Jankowski's Bunting breeding season began in late April and usually ended in late July. Both sexes participated in nest-building, feeding young and defending the nest. Mean full clutch size for three years combined was 5.26 ± 0.76 eggs, and ranged from four to seven. Clutch size decreased with nest-initiation date. Mean hatching rate was 41.2%. Overall probability of Mayfield nest success to fledging was low for the three years, averaging 0.218 ± 0.007. The factors leading to low nest success include nest parasitization, nest predation, human activities and nest abandonment. Low survival of Jankowski's Bunting nests may be a factor in declining populations and the slow recovery of populations because of low recruitment at the population and the individual level. The population of Jankowski's Bunting in the Dagang Forestry grassland was small and declined dramatically from 1999 to 2006. The main threat is habitat loss and fragmentation due to agriculture, tree planting and housing following human colonization of the region. The habitat has been reduced in extent by c. 70% since the 1960s. In addition, grazing by domestic livestock dramatically destroyed their preferred vegetation. Furthermore, the restriction to several small, discrete sites makes the bunting inherently vulnerable to catastrophic and stochastic events that can eliminate subpopulations. Jankowski's bunting is one of the most threatened species in China and faces an unpredictable future. Maintaining the structure and general composition of remaining Jankowski's Bunting nesting habitat is important to ensure continued presence of this species in western Jilin and worldwide.

scholarly journals Heterotaxy in Caenorhabditis : widespread natural variation in left–right arrangement of the major organs

2016 ◽  
Vol 371 (1710) ◽  
pp. 20150404 ◽  
Author(s):  
Melissa R. Alcorn ◽  
Davon C. Callander ◽  
Agustín López-Santos ◽  
Yamila N. Torres Cleuren ◽  
Bilge Birsoy ◽  
...  
Keyword(s):  
Genome Wide Association Study ◽  
Recombinant Inbred Lines ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
Internal Organs ◽  
Genome Wide ◽  
A Genome ◽  
Natural Isolates ◽  
Left Right Asymmetry ◽  
Genomic Regions

Although the arrangement of internal organs in most metazoans is profoundly left–right (L/R) asymmetric with a predominant handedness, rare individuals show full (mirror-symmetric) or partial (heterotaxy) reversals. While the nematode Caenorhabditis elegans is known for its highly determinate development, including stereotyped L/R organ handedness, we found that L/R asymmetry of the major organs, the gut and gonad, varies among natural isolates of the species in both males and hermaphrodites. In hermaphrodites, heterotaxy can involve one or both bilaterally asymmetric gonad arms. Male heterotaxy is probably not attributable to relaxed selection in this hermaphroditic species, as it is also seen in gonochoristic Caenorhabditis species. Heterotaxy increases in many isolates at elevated temperature, with one showing a pregastrulation temperature-sensitive period, suggesting a very early embryonic or germline effect on this much later developmental outcome. A genome-wide association study of 100 isolates showed that male heterotaxy is associated with three genomic regions. Analysis of recombinant inbred lines suggests that a small number of loci are responsible for the observed variation. These findings reveal that heterotaxy is a widely varying quantitative trait in an animal with an otherwise highly stereotyped anatomy, demonstrating unexpected plasticity in an L/R arrangement of the major organs even in a simple animal. This article is part of the themed issue ‘Provocative questions in left–right asymmetry’.

Sign in / Sign up

Export Citation Format

Share Document