The sex ratio of crocodiles is strongly biased towards females, often as high as 10 females to 1 male. In crocodilians, the temperature of egg incubation is the environmental factor determining sex. If the temperature...The sex ratio of crocodiles is strongly biased towards females, often as high as 10 females to 1 male. In crocodilians, the temperature of egg incubation is the environmental factor determining sex. If the temperature is low, around 30˚C, the hatchlings are all females. Higher temperature, around 34˚C, hatch all males. This study was made to consider the asymptotic stability of a positive equilibrium point in a nonlinear discrete model of the basic nesting population model, which is described in three-region depending on the temperature of egg incubation. This model is based on key life-historical data and Murray’s research. To study above, we have applied the classical linearization method and P. Cull’s method and moreover, we employ non-standard discretization methods for later our Equations (6)-(8) and (15).展开更多
We explored the morphological organization of the skull within Crocodylidae,analyzing functional and phylogenetic interactions between its 2 constituent functional modules:the rostrum and the postrostrum.We used...We explored the morphological organization of the skull within Crocodylidae,analyzing functional and phylogenetic interactions between its 2 constituent functional modules:the rostrum and the postrostrum.We used geometric morphometrics to identify localized shape changes,focusing on the differences between the major clades of the crown-group Crocodylia:Alligatoridae and Crocodylidae.We used published bite performance data to correlate rostral function with postrostral morphology.The skull modules appear more integrated within Alligatoridae than within Crocodyliade.Phylogenetic effects on shape variation are more evident in Alligatoridae than in Crocodylidae,where functional parameters concerning the rostral morphology are proportionally more important than phylogeny.Long-snouted species are characterized by low structural performance,which is significantly associated with a reduction of the pterygoid-quadrate cranial nipper,suggesting that the nipper is important for the ingestion of large food items in generalist species.This functional association is coupled with a significant evolutionary allometry at the clade level,while Alligatoridae and Crocodylidae show different degrees of evolutionary allometry for their entire shape and rostrum.The postrostrum is more conservative than the rostrum in terms of morphospace occupation,evolutionary allometry and phylogenetic signal.展开更多
Serum samples from all 23 extant crocodilian species were tested for phospholipase A2 (PLA2) activity against nine different bacterial species. The data were used?to generate a PLA2 activity profile for each crocodili...Serum samples from all 23 extant crocodilian species were tested for phospholipase A2 (PLA2) activity against nine different bacterial species. The data were used?to generate a PLA2 activity profile for each crocodilian species, and the data were used to compare the activities of the three main lineages (Alligatoridae,?Crocodylidae, and Gavialidae), the seven different genera, and to compare all?of the 23 individual species. The data revealed that the three lineages ofcrocodilians (Alligatoridae, Crocodylidae, and Gavialidae) exhibited PLA2 activities toward nine species of bacteria that were statistically?distinguishable. In?addition,?the PLA2 activities of crocodilians in a specific genus tended to be more similar to other?members in their genus than to members of other crocodilian genera.展开更多
Chitotriosidase (ChT) is an endoglucosaminidase enzyme that cleaves chitinous substrates and has been strongly associated with innate immune activity and the ability to identify non-selftissues. This enzyme activity w...Chitotriosidase (ChT) is an endoglucosaminidase enzyme that cleaves chitinous substrates and has been strongly associated with innate immune activity and the ability to identify non-selftissues. This enzyme activity was detected and characterized the serum from the American alligator (Alligator mississippiensis) using a fluorometric probe. Alligator serum exhibited volume-dependent activity, with activity (2.1 ± 0.3 μmol/min) observed at dilutions as low as a 1:150, and maximum activity (5.2 ± 0.6 μmol/min) measured at a dilution of 1:30. Alligator serum ChT showed linear activity for approximately 20 min, at which time activity decreased exponentially, presumably due to the depletion of substrate. In addition, the ChT activity in alligator serum was temperature-dependent with low activity at 5°C, a sharp increase from 10°C - 30°C, and maximal activity from 30°C - 40°C. The activity was inhibited in the presence of water-soluble chitin, but not mannan, indicating the specificity of the enzyme. The presence of ChT in alligator serum is likely to be partially responsible for the potent innate immune system of these crocodylians, and particularly antifungal activities.展开更多
文摘The sex ratio of crocodiles is strongly biased towards females, often as high as 10 females to 1 male. In crocodilians, the temperature of egg incubation is the environmental factor determining sex. If the temperature is low, around 30˚C, the hatchlings are all females. Higher temperature, around 34˚C, hatch all males. This study was made to consider the asymptotic stability of a positive equilibrium point in a nonlinear discrete model of the basic nesting population model, which is described in three-region depending on the temperature of egg incubation. This model is based on key life-historical data and Murray’s research. To study above, we have applied the classical linearization method and P. Cull’s method and moreover, we employ non-standard discretization methods for later our Equations (6)-(8) and (15).
基金Paolo Piras had access to the collections of the Natural History Museum in London,the Institut Royal des Sciences Naturelles in Bruxelles and the Museum d’Histoire Naturelle in Paris thanks to the SYNTHESYS program,and to the collection of the Field Museum in Chicago thanks to the Visiting Scholarship Program.Funds from the Geological Science Department of‘Roma Tre’University made possible the visit to the American Museum of Natural History,New York.Part of this research was conducted during a postdoctoral visit by Paolo Piras,supervised by Jorge Cubo,to the UniversitéPierre et Marie Curie.Funds were also provided by Project CGL-2009-11838 from the Spanish Ministerio de Ciencia e Innovacion Cientifica,Spain.
文摘We explored the morphological organization of the skull within Crocodylidae,analyzing functional and phylogenetic interactions between its 2 constituent functional modules:the rostrum and the postrostrum.We used geometric morphometrics to identify localized shape changes,focusing on the differences between the major clades of the crown-group Crocodylia:Alligatoridae and Crocodylidae.We used published bite performance data to correlate rostral function with postrostral morphology.The skull modules appear more integrated within Alligatoridae than within Crocodyliade.Phylogenetic effects on shape variation are more evident in Alligatoridae than in Crocodylidae,where functional parameters concerning the rostral morphology are proportionally more important than phylogeny.Long-snouted species are characterized by low structural performance,which is significantly associated with a reduction of the pterygoid-quadrate cranial nipper,suggesting that the nipper is important for the ingestion of large food items in generalist species.This functional association is coupled with a significant evolutionary allometry at the clade level,while Alligatoridae and Crocodylidae show different degrees of evolutionary allometry for their entire shape and rostrum.The postrostrum is more conservative than the rostrum in terms of morphospace occupation,evolutionary allometry and phylogenetic signal.
文摘Serum samples from all 23 extant crocodilian species were tested for phospholipase A2 (PLA2) activity against nine different bacterial species. The data were used?to generate a PLA2 activity profile for each crocodilian species, and the data were used to compare the activities of the three main lineages (Alligatoridae,?Crocodylidae, and Gavialidae), the seven different genera, and to compare all?of the 23 individual species. The data revealed that the three lineages ofcrocodilians (Alligatoridae, Crocodylidae, and Gavialidae) exhibited PLA2 activities toward nine species of bacteria that were statistically?distinguishable. In?addition,?the PLA2 activities of crocodilians in a specific genus tended to be more similar to other?members in their genus than to members of other crocodilian genera.
文摘Chitotriosidase (ChT) is an endoglucosaminidase enzyme that cleaves chitinous substrates and has been strongly associated with innate immune activity and the ability to identify non-selftissues. This enzyme activity was detected and characterized the serum from the American alligator (Alligator mississippiensis) using a fluorometric probe. Alligator serum exhibited volume-dependent activity, with activity (2.1 ± 0.3 μmol/min) observed at dilutions as low as a 1:150, and maximum activity (5.2 ± 0.6 μmol/min) measured at a dilution of 1:30. Alligator serum ChT showed linear activity for approximately 20 min, at which time activity decreased exponentially, presumably due to the depletion of substrate. In addition, the ChT activity in alligator serum was temperature-dependent with low activity at 5°C, a sharp increase from 10°C - 30°C, and maximal activity from 30°C - 40°C. The activity was inhibited in the presence of water-soluble chitin, but not mannan, indicating the specificity of the enzyme. The presence of ChT in alligator serum is likely to be partially responsible for the potent innate immune system of these crocodylians, and particularly antifungal activities.
