Keyword: age determination

Formação, eclosão e troca dentária em Subulo gouazoubira e Mazama rufa (Arctyodactila: Cervidae) e sua aplicação na estimação de idade em pequenos cervídeos

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O uso de marcos dentários para a estimação da idade é comum em estudos de diversos taxa. Em especial, o processo de formação e substituição dos dentes molariformes, com cronologia geneticamente determinada, é frequentemente utilizado em técnicas de identificação da idade em mamíferos. No presente trabalho, foram realizadas análises radiográficas para investigar a cronologia mensal de eventos dentários, tais como o surgimento de cistos formadores de dentes, mineralização de coroa e raiz, eclosão e troca dentária em Subulo gouazoubira e Mazama rufa. Os indivíduos foram radiografados sob anestesia geral e os achados radiológicos foram organizados do primeiro ao vigésimo quinto mês de vida. Uma vez definidos os eventos dentários mensais, esses resultados foram comparados com quatro S. gouazoubira vivos e 31 preparações osteológicas de cabeças (25 S. gouazoubira, três M. rufa, dois M. nana e um M. jucunda). Vinte e dois animais foram identificados como tendo idades entre um a 24 meses, enquanto outros 13 tinham 25 meses ou mais. Todos os eventos dentários listados estavam presentes nas determinações de idade realizadas, evidenciando a acurácia mensal da técnica.

Dental development in Subulo gouazoubira and Mazama rufa (Arctiodactyla: Cervidae), and its application for age determination in deers. The use of dentition and dental traits for age determination is common in studies of several taxa. In particular, the genetically determined process of forming and replacing molariform teeth is frequently used for age determination in mammals. In the present study, radiographic analyses were conducted to investigate the monthly chronology of dental development, such as the appearance of tooth-forming cysts, crown and root mineralization, tooth eruption, and tooth exchange in Subulo gouazoubira and Mazama rufa. Subjects were anesthetized and radiographed, and radiological findings were organized from the first to the twenty-fifth month of age. Once the monthly stages were defined, these data were compared with four S. gouazoubira alive and 31 osteological preparations of heads (25 S. gouazoubira, three M. rufa, two M. nana, and one M. jucunda). Of these examinations, 22 were identified as having between one and 24 months of age, and the other 13 were 25 months old or older. All stages listed were observed in the age determinations performed, confirming the monthly accuracy of the technique.

Graphical abstract for the article “Formação, eclosão e troca dentária em Subulo gouazoubira e Mazama rufa (Arctyodactila: Cervidae) e sua aplicação na estimação de idade em pequenos cervídeos” (Martins de Souza et al., 2025)

New record of a stranded sperm whale (Physeter macrocephalus) and a review of strandings along the continental Argentine coast

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We present a new record of sperm whale with notes on diet, age determination and a review of strandings along the continental Argentine coast. A complete necropsy was made in the field, and morphometric data were taken. The specimen stranded was a mature male of 64+ years old. This is the oldest specimen determined for a sperm whale in the Southwest Atlantic coast. In the stomach contents a total of 302 cephalopod lower beaks were recovered. Cestodes were present in the blubber but parasites were not found in stomach and intestine contents.

Nuevo registro de un cachalote (Physeter macrocephalus) varado y una revisión de varamientos en las costas de Argentina continental. Presentamos un nuevo registro de un cachalote, con notas sobre la dieta, la determinación de edad y la presencia de parásitos, junto con una revisión de los varamientos a lo largo de toda la costa continental argentina. El animal varado fue un macho maduro de 64+ años. Este es el individuo más longevo registrado para esta especie en el Atlántico Sudoccidental. En el contenido estomacal se colectaron 302 picos inferiores de cefalópodos. Los únicos parásitos presentes fueron cestodes en la capa de grasa; no se encotraron helmintos gastrointestinales.

Morphological variation and age determination in Calomys venustus (Thomas, 1894) (Rodentia, Muridae)

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The morphological and morphometric characters of Calomys venustus are studied to recognize variations according to age and sex. Measurements were obtained from litters born in laboratory from mating of wild mice. The litters were distributed into age classes by sex. Eighteen cranial measurements, body length, tail length, body weight and eye lens weight were recorded for each individual as well as the tooth wear. A selection of characters was done, previous to a two-way ANOVA (age and sex). The D² of Mahalanobis between each pair of age group was calculated by considering all characters simultaneously. Discriminant functions were performed according to sex for each age group by using the selected characters in order to develop a technique for assigning individuals to age groups. A Chi-Square test was applied to compare the class of tooth wear and the chronological age of the animals. A significant correlation was established between age and the following characters: length of bone palate, mandible length, mandible height, nasal width, interorbital width, maximum width of neurocrania, distance between yugular processes, condylo-molar 1 length, zygomatic width, basal length, condylo-zygomatic length, incisive-molar 3 length and length of diastema. Characters can discriminate from two to four homogeneous morphological groups. The assignment to a tooth wear class showed significant differences with respect to the real age. The great variability in tooth wear renders this method inappropriate for an accurate assignation of individuals of C. venustus to an age class. The discriminant functions allow a better assignment of specimens to morphologically homogeneous groups, distinguishable among themselves.

Variación morfológica y determinación de la edad en Calomys venustus (Thomas, 1894) (Rodentia, Muridae). Con el propósito de reconocer variaciones respecto a la edad y sexo en ejemplares de Calomys venustus, se analizaron caracteres morfológicos y morfométricos. El estudio se llevó a cabo en crías obtenidas en laboratorio a partir de parejas de campo. Las crías fueron distribuidas en clases de edades por sexo. Para cada animal fueron registradas medidas craneales, longitud corporal, longitud de la cola, masa corporal y peso de cristalinos, como así también desgaste molar. Los caracteres fueron seleccionados mediante un ANOVA de dos vías (edad y sexo). La D² de Mahalanobis entre cada par de grupos de edades fue calculada, considerando todos los caracteres simultáneamente. Fueron construidas funciones discriminantes para cada grupo de edad y sexo utilizando los caracteres seleccionados a fin de poder asignar los individuos a los grupos de edades. Para la comparación entre la clase de desgaste y la edad de los animales fue aplicada una Chi-cuadrada. Trece caracteres craneométricos mostraron variación significativa con la edad, pudiendo reconocerse desde dos hasta cuatro grupos morfológicamente homogéneos. La asignación a la clase de desgaste molar mostró diferencias significativas con respecto a la edad real.