Validation of skeletochronology to determine age of freshwater crocodiles (Crocodylus johnstoni)

1997 ◽  
Vol 48 (4) ◽  
pp. 343 ◽  
Author(s):  
Anton D. Tucker
Keyword(s):  
Age Estimation ◽  
Egg Laying ◽  
Interference Microscopy ◽  
Adult Males ◽  
Size Estimation ◽  
Thin Sections ◽  
Crocodylus Johnstoni ◽  
Old Adult ◽  
Different Seasons ◽  
Australian Freshwater

Age was estimated for wild Australian freshwater crocodiles from skeletochronology of growth marks in postoccipital osteoderms. Growth marks were distinct and counted reliably in unstained calcified thin sections (60–80 µm) viewed by Nomarski interference microscopy. The periodicity of growth marks was validated directly from crocodiles of known age (up to 19 years) and from individuals sampled sequentially in different seasons. Growth marks comprised annuli deposited in winter and zones deposited in summer. Errors in age estimation for small crocodiles resulted from difficulty in assigning the growing edge as either a zone or an annulus. No osseous remodelling was noted for immature animals. Age estimates for adult females became unreliable as previous annuli were obscured by osseous remodelling, presumably resulting from calcium mobilization by egg-laying females. Old adult males continued to deposit annuli, but these were more difficult to distinguish, being more closely spaced than in young crocodiles. Skeletochronology permitted reliable (coefficient of variation, 3·4%) and accurate (±1 year) age estimation up to about 20 years. Osteoderm dimensions were strongly correlated with average snout–vent length, mass and age and have acceptable potential as an indirect means of age and size estimation for Crocodylus johnstoni.

Movements and Home Ranges of Crocodylus johnstoni in the Lynd River, Queensland

1997 ◽  
Vol 24 (4) ◽  
pp. 379 ◽  
Author(s):  
A. D. Tucker ◽  
C. J. Limpus ◽  
H. I. McCallum ◽  
K. R. McDonald
Keyword(s):  
Field Trips ◽  
Home Ranges ◽  
Adult Males ◽  
Dominance Hierarchies ◽  
Breeding Sites ◽  
Crocodylus Johnstoni ◽  
Upstream Direction ◽  
A Minor ◽  
Australian Freshwater ◽  
Local Dominance

Movements of Australian freshwater crocodiles, Crocodylus johnstoni, were examined by a mark–recapture study spanning 20 years in the Lynd River, Queensland. After adjustment for detection bias, there was a minor upstream direction to movements. Seasonal changes of location were not evident from field trips taken only twice yearly. Annual movements averaged less than 1 km except for those of pubescent males, which appeared to be nomadic. Creche dispersal was randomly directed but associated with a threshold in mass/length ratio. On average, males were found further from previous capture sites than were females. Adults of both sexes moved shorter distances than did immature crocodiles with a clear reduction in movements occurring as mass/length ratios approached 0·17 kg per cm snout–vent length. Reduced movement at that general size ratio probably indicated the onset of territoriality associated with maturity. Females usually remained near breeding sites even in years when they did not breed. Nomadic tendencies of pubescent males are probably associated with unsuccessful attempts at entering local dominance hierarchies. Linear home ranges were estimated to be 1·5–1·9 km for immature animals, 1·2 km for pubescent females, 30·3 km for pubescent males, 0·6 km for mature females and 1·6 km for adult males.

scholarly journals Osmoregulatory mechanisms of the Australian freshwater crocodile, Crocodylus johnstoni , in freshwater and estuarine habitats

1999 ◽  
Vol 169 (3) ◽  
pp. 215-223 ◽  
Author(s):  
L. E. Taplin ◽  
G. C. Grigg ◽  
L. A. Beard ◽  
T. Pulsford
Keyword(s):  
Crocodylus Johnstoni ◽  
Freshwater Crocodile ◽  
Australian Freshwater

The annual testicular cycle of the brown-headed cowbird (Molothrus ater)

1968 ◽  
Vol 46 (1) ◽  
pp. 77-87 ◽  
Author(s):  
D. M. Scott ◽  
A. L. A. Middleton
Keyword(s):  
Breeding Season ◽  
Molothrus Ater ◽  
Age Groups ◽  
Egg Laying ◽  
Sperm Production ◽  
Behavioral Differences ◽  
Testicular Regression ◽  
Old Adult ◽  
The Mean ◽  
Two Age Groups

An analysis of the spermatogenic condition and of the weights of testes from about 450 brown-headed cowbirds (Molothrus ater) was made to determine the annual cycle of this species at London, Ontario, and to ascertain variation in the cycle due to age. Testes of birds more than 1 year old (adult) reached maximal weights in late April and early May coincident with the beginning of egg-laying, and about 3 weeks before the testes of 1-year-old birds (yearlings) reached their maximal weight. The mean weights of testes of adults were usually greater, often significantly so, than those of yearlings. From about May 23 to June 23 there were no statistically significant differences in the weights of testes from the two age groups. Beginning in late June, the weights of testes declined rapidly in both age groups and reached a minimum in August. Minimal weights of testes persisted in captive birds until February.Large amounts of sperm were present in the testes of adults in mid-April and of yearlings in late April well in advance of maximal testicular weights. Sperm production occurred in most birds until early July but had ceased in most by late July.Testes, apparently undergoing regression, were noted significantly (p <.005) more frequently in adults than in yearlings in May and early June at the height of the breeding season. The significance of this observation and some aspects of testicular regression, previously unrecorded, are discussed. Adult birds are more sedentary than most yearlings in the breeding season and, unlike the latter, habitually associate with the same female. These behavioral differences may be related to the observed differences between the age groups in the testicular cycle.

Reconstructing reproductive histories of black bears from the incremental layering in dental cementum

1992 ◽  
Vol 70 (11) ◽  
pp. 2150-2160 ◽  
Author(s):  
Pamela L. Coy ◽  
David L. Garshelis
Keyword(s):  
Ursus Americanus ◽  
Black Bears ◽  
Adult Males ◽  
Thin Sections ◽  
Dental Cementum ◽  
Outer Annulus ◽  
First Reproduction ◽  
Dark Staining ◽  
Reproductive Rates ◽  
Light Staining

Known reproductive histories of female radio-collared black bears (Ursus americanus) in Minnesota were matched against the spacing of growth layers in stained thin sections of their teeth. Light-staining bands of cementum, deposited during the summer months, were relatively narrow during years when females were raising cubs. Because females in this study never successfully reared cubs in 2 consecutive years, narrow light bands were bordered by wider bands, causing the intervening dark-staining fall–winter annuli to appear paired. Adult males exhibited similar pairing of dark annuli, caused not by altered annular spacing but by deposition of distinct summer accessory lines. Paired dark annuli in females accurately reflected known cub-rearing records, although it was more difficult to determine the years of cub production (reading teeth from the outer annulus inward) than the ages of females when they produced cubs (counting annuli outward from the dentin–cementum interface). The distribution of ages of first reproduction gleaned from teeth of harvested females coincided with that of females with known reproductive histories, indicating that teeth currently collected from harvested black bears by management agencies across North America could provide reasonably good accounts of both present and past reproductive rates.

Morphometric analysis of the Australian freshwater crocodile (Crocodylus johnstoni)

2017 ◽  
Vol 65 (2) ◽  
pp. 97 ◽  
Author(s):  
Glenn P. Edwards ◽  
Grahame J. Webb ◽  
S. Charlie Manolis ◽  
Alex Mazanov
Keyword(s):  
Morphometric Analysis ◽  
Body Measurements ◽  
Body Parts ◽  
Allometric Growth ◽  
Relative Growth ◽  
Crocodylus Johnstoni ◽  
Arnhem Land ◽  
Freshwater Crocodile ◽  
Crocodylus Porosus ◽  
Australian Freshwater

We conducted a morphometric analysis of 279 Crocodylus johnstoni, using specimens from the McKinlay River (n = 265) and Arnhem Land (n = 14), to meet the management need for predicting body size of C. johnstoni from isolated body parts. The results also allow reconstruction of C. johnstoni dimensions for comparison with other crocodilian species. We detected sexual dimorphism in some body measurements from the McKinlay River, and geographic variation in the morphology of McKinlay River and Arnhem Land populations, but differences were slight. There is pronounced allometric growth in C. johnstoni in the immediate post-hatching phase, largely due to elongation of the snout after exiting the confines of the egg. We compared the size, shape and relative growth of C. johnstoni with that of other crocodilian species for which equivalent data are available, but particularly the other Australian crocodile, Crocodylus porosus. C. porosus has a proportionately longer tail and a shorter but wider snout than C. johnstoni, and we discuss possible ecological correlates of these and other differences.

scholarly journals Developmental- and tissue-specific changes of ubiquitin forms in Drosophila melanogaster.

2018 ◽  
Author(s):  
Ágota Nagy ◽  
Levente Kovács ◽  
Zoltán Lipinszki ◽  
Margit Pál ◽  
Péter Deák
Keyword(s):  
Developmental Stages ◽  
Biological Function ◽  
Antagonistic Activity ◽  
Adult Males ◽  
Equilibrium Dynamics ◽  
First Instar ◽  
Old Adult ◽  
Covalently Linked ◽  
Free Ubiquitin ◽  
Immunoblotting Technique

In most Eukaryotes, ubiquitin either exists as free monoubiquitin or as a molecule that is covalently linked to other proteins. These two forms cycle between each other and due to the concerted antagonistic activity of ubiquitylating and deubiquitylating enzymes, an intracellular ubiquitin equilibrium is maintained that is essential for normal biological function. However, measuring the level and ratio of these forms of ubiquitin has been difficult and time consuming. In this paper, we have adapted a simple immunoblotting technique to monitor ubiquitin content and equilibrium dynamics in different developmental stages and tissues of Drosophila. Our data show that the level of total ubiquitin is distinct in different developmental stages, lowest at the larval-pupal transition and in three days old adult males, and highest in first instar larvae. Interestingly, the ratio of free mono-ubiquitin remains within 30-50% range of the total throughout larval development, but peaks to 70-80% at the larval-pupal and the pupal-adult transitions. It stays within the 70-80% range in adults. In developmentally and physiologically active tissues, the ratio of free ubiquitin is similarly high, most likely reflecting a high demand for ubiquitin availability. We also used this method to demonstrate the disruption of the finely tuned ubiquitin equilibrium by the abolition of proteasome function or the housekeeping deubiquitylase, Usp5. Our data support the notion that the ubiquitin equilibrium is regulated by tissue- and developmental stage-specific mechanisms.

Organization of the cytoskeleton during cellularization in Drosophila melanogaster embryos: Confocal laser scanning and electron microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 462-463
Author(s):  
Kazuo Katoh ◽  
Harunori Ishikawa
Keyword(s):  
Electron Microscopy ◽  
Drosophila Melanogaster ◽  
Phosphate Buffer ◽  
Laser Scanning ◽  
Picric Acid ◽  
Egg Laying ◽  
Laser Scanning Microscopy ◽  
Confocal Laser Scanning ◽  
Confocal Laser ◽  
Thin Sections

The three-dimensional organization of cytoskeletal components in the early Drosophila melanogaster embryos during cellularization was examined by confocal laser scanning microscopy of the whole embryos and thin section electron microscopy.For confocal microscopy, Drosophila embryos at 2-3 hr after egg-laying were dechorionated and fixed with 8% paraformaldehyde-1% picric acid in 0.1M phosphate buffer (pH 7.2). Embryos were first blocked with normal goat serum, incubated with monoclonal antibody raised against Drosophila embryo α-tubulin for 4 hr, and then were incubated with FITC-conjugated anti-mouse IgG for 2 hr. Some embryos were stained with rhodamine-labeled phailoidin for F-actin visualization. After staining, the whole embryos were mounted on slide glass with an appropriate spacer and examined under the confocal microscope (Bio-Rad, Lasersharp MRC-500). For electron microscopy, dechorionated embryos were fixed with 1/2 Karnovsky's fixative followed by OsO4 fixation. To better preserve actin filaments, embryos were fixed with the same 1/2 Karnovsky's fixative containing 10 μM phailoidin and 0.1% saponin in 0.1M phosphate buffer, pH 7.2. Such fixed embryos were dehydrated and then embedded in Epoxy resin. Thin sections were cut and examined under a Hitachi H-800 type electron microscope.

scholarly journals MEASUREMENT OF THICKNESS WITHIN SECTIONS BY QUANTITATIVE ELECTRON MICROSCOPY

1969 ◽  
Vol 40 (3) ◽  
pp. 768-772 ◽  
Author(s):  
Lloyd Silverman ◽  
Berit Schreiner ◽  
David Glick
Keyword(s):  
Electron Microscopy ◽  
Phosphotungstic Acid ◽  
Exchange Resin ◽  
Interference Microscopy ◽  
Quantitative Electron Microscopy ◽  
Thin Sections ◽  
Calculated Mass ◽  
Thickness Standard ◽  
Embedding Medium ◽  
Measurement Of Thickness

To apply the method of quantitative electron microscopy to the measurement of mass in thin sections, the thickness of the section at or very near the structure to be studied must be known. Dowex anion exchange resin AG 1 x 2, stained with phosphotungstic acid (PTA) at pH 6.4, was used as a thickness standard which could be embedded and sectioned. The sectioned PTA-Dowex appeared uniformly stained and exhibited suitable electron opacity. The stoichiometry of the reaction between PTA and the Dowex resin was measured by three independent methods based on gravimetric, colorimetric, and nitrogen determinations whose results showed close agreement. From the PTA uptake, the density of the stained spheres was calculated. Mass of a defined area of PTA-Dowex was measured by quantitative electron microscopy, and from this mass and density, the volume and then the thickness were calculated. The values for thickness were compared to those obtained by interference microscopy on the embedding medium alone in the same sections.

scholarly journals Variation of osteocyte lacunae size within the tetrapod skeleton: implications for palaeogenomics

2011 ◽  
Vol 7 (5) ◽  
pp. 751-754 ◽  
Author(s):  
Shaena Montanari ◽  
Stephen L. Brusatte ◽  
Wendy De Wolf ◽  
Mark A. Norell
Keyword(s):  
Genome Size ◽  
Bone Cells ◽  
Genetic Material ◽  
Size Variation ◽  
Bone Cell ◽  
Estimation Methods ◽  
Size Estimation ◽  
Thin Sections ◽  
Osteocyte Lacunae ◽  
Significant Difference

Recent studies have emphasized the ability to reconstruct genome sizes (C-values) of extinct organisms such as dinosaurs, using correlations between known genome sizes and bone cell (osteocyte lacunae) volumes. Because of the established positive relationship between cell size and genome size in extant vertebrates, osteocyte lacunae volume is a viable proxy for reconstructing C-values in the absence of any viable genetic material. However, intra-skeletal osteocyte lacunae size variation, which could cause error in genome size estimation, has remained unexplored. Here, 11 skeletal elements of one individual from each of four major clades (Mammalia, Amphibia, Aves, Reptilia) were examined histologically. Skeletal elements in all four clades exhibit significant differences in the average sizes of their lacunae. This variation, however, generally does not cause a significant difference in the estimated genome size when common phylogenetic estimation methods are employed. On the other hand, the spread of the estimations illustrates that this method may not be precise. High variance in genome size estimations remains an outstanding problem. Additionally, a suite of new methods is introduced to further automate the measurement of bone cells and other microstructural features on histological thin sections.

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