Resumo
Los estudios de crecimiento en crustáceos típicamente utilizan análisis modal en lugar de focalizarse en el crecimiento individual de los organismos. En el presente trabajo, utilizamos morfometría geométrica para determinar cómo varia la forma y el tamaño a lo largo de la vida del cangrejo de agua dulce, Aegla uruguayana Schmitt, 1942. Un total de 66 individuos, en diferentes etapas del ciclo de vida, se examinaron diariamente, registrándose la presencia de exuvias. Imágenes digitales de cada muda fueron obtenidas de la región dorsal del cefalotórax y se utilizaron para registrar las configuraciones de landmarks. El incremento por muda y el período de intermuda se estimaron para cada cangrejo. Diferencias de forma entre tamaños (alometría) y sexos (dimorfismo sexual; SD) se observaron. Se registró la presencia de alometría entre los especímenes; sin embargo, el SD no fue estadísticamente significativo respecto del tamaño. El período intermuda aumentó de manera directamente proporcional al tamaño, pero la frecuencia de muda fue similar entre los sexos. Durante la ontogenia, los juveniles presentaron rostro corto y romo, frente robusta, y ancho del cefalotórax estrecho. Los adultos presentaron la región anterior y posterior del cefalotórax bien definido en relación con los juveniles. El rostro fue largo y estilizado y la frente estrecha. Los métodos de morfometría geométrica fueron muy efectivos para el análisis del crecimiento individual en aéglidos y permitieron evitar la manipulación excesiva de los individuos a través del análisis de las mudas(AU)
Crustacean growth studies typically use modal analysis rather than focusing on the growth of individuals. In the present work, we use geometric morphometrics to determine how organism shape and size varies during the life of the freshwater crab, Aegla uruguayana Schmitt, 1942. A total of 66 individuals from diverse life cycle stages were examined daily and each exuvia was recorded. Digital images of the dorsal region of the cephalothorax were obtained for each exuvia and were subsequently used to record landmark configurations. Moult increment and intermoult period were estimated for each crab. Differences in shape between crabs of different sizes (allometry) and sexes (sexual dimorphism; SD) were observed. Allometry was registered among specimens; however, SD was not statistically significant between crabs of a given size. The intermoult period increased as size increased, but the moult frequency was similar between the sexes. Regarding ontogeny, juveniles had short and blunt rostrum, robust forehead region, and narrow cephalothorax. Unlike juveniles crabs, adults presented a well-defined anterior and posterior cephalothorax region. The rostrum was long and stylised and the forehead narrow. Geometric morphometric methods were highly effective for the analysis of aeglid-individual- growth and avoided excessive handling of individuals through exuvia analysis(AU)
Assuntos
Animais , Crustáceos/anatomia & histologia , Crustáceos/crescimento & desenvolvimento , Tórax/anatomia & histologia , Cabeça/anatomia & histologia , Caracteres Sexuais , Muda , CrescimentoResumo
Los estudios de crecimiento en crustáceos típicamente utilizan análisis modal en lugar de focalizarse en el crecimiento individual de los organismos. En el presente trabajo, utilizamos morfometría geométrica para determinar cómo varia la forma y el tamaño a lo largo de la vida del cangrejo de agua dulce, Aegla uruguayana Schmitt, 1942. Un total de 66 individuos, en diferentes etapas del ciclo de vida, se examinaron diariamente, registrándose la presencia de exuvias. Imágenes digitales de cada muda fueron obtenidas de la región dorsal del cefalotórax y se utilizaron para registrar las configuraciones de landmarks. El incremento por muda y el período de intermuda se estimaron para cada cangrejo. Diferencias de forma entre tamaños (alometría) y sexos (dimorfismo sexual; SD) se observaron. Se registró la presencia de alometría entre los especímenes; sin embargo, el SD no fue estadísticamente significativo respecto del tamaño. El período intermuda aumentó de manera directamente proporcional al tamaño, pero la frecuencia de muda fue similar entre los sexos. Durante la ontogenia, los juveniles presentaron rostro corto y romo, frente robusta, y ancho del cefalotórax estrecho. Los adultos presentaron la región anterior y posterior del cefalotórax bien definido en relación con los juveniles. El rostro fue largo y estilizado y la frente estrecha. Los métodos de morfometría geométrica fueron muy efectivos para el análisis del crecimiento individual en aéglidos y permitieron evitar la manipulación excesiva de los individuos a través del análisis de las mudas
Crustacean growth studies typically use modal analysis rather than focusing on the growth of individuals. In the present work, we use geometric morphometrics to determine how organism shape and size varies during the life of the freshwater crab, Aegla uruguayana Schmitt, 1942. A total of 66 individuals from diverse life cycle stages were examined daily and each exuvia was recorded. Digital images of the dorsal region of the cephalothorax were obtained for each exuvia and were subsequently used to record landmark configurations. Moult increment and intermoult period were estimated for each crab. Differences in shape between crabs of different sizes (allometry) and sexes (sexual dimorphism; SD) were observed. Allometry was registered among specimens; however, SD was not statistically significant between crabs of a given size. The intermoult period increased as size increased, but the moult frequency was similar between the sexes. Regarding ontogeny, juveniles had short and blunt rostrum, robust forehead region, and narrow cephalothorax. Unlike juveniles crabs, adults presented a well-defined anterior and posterior cephalothorax region. The rostrum was long and stylised and the forehead narrow. Geometric morphometric methods were highly effective for the analysis of aeglid-individual- growth and avoided excessive handling of individuals through exuvia analysis
Assuntos
Animais , Cabeça/anatomia & histologia , Caracteres Sexuais , Crustáceos/anatomia & histologia , Crustáceos/crescimento & desenvolvimento , Muda , Tórax/anatomia & histologia , CrescimentoResumo
A study on population structure of Aegla schmitti Hobbs III, 1979 was carried out at Mananciais da Serra, in the municipality of Piraquara, state of Paraná, Brazil (25º29'S, 48º58'W). The following aspects were treated: temporal fluctuation in abundance, sex ratio, reproductive period and size composition based on carapace length. The animals were colleted with traps, nets, measured and returned to the reservoirs. This population was sampled monthly, in two reservoirs (Carvalho and Carvalhinho) constructed in the headwater streams with swift current and steep gradient, located on west side of Serra do Mar mountains, from November, 2004 to January, 2006. The water temperature varied from 11.0 (July, 2005) to 18.2ºC (March, 2007), dissolved oxygen from 7.0 to 9.5 mg/l and pH from 4.8 to 6.7, during collection period. A total of 1230 individuals were collected, among which, 819 were males and 411 females (30 ovigerous). The abundance varied from 23 (December, 2004) to 122 (June, 2005) crabs and the sex ratio of the whole population was 1:0.5 (M:F). Male carapace length varied from 4.38 to 36.46 mm and female, from 4.28 to 32.56 mm. Ovigerous females occurred from April, 2005 to November, 2005. Higher crab abundance was recorded in the Carvalho Reservoir, which explained by the presence of numerous breaches on the old tank walls that acted as shelters for these animals. Aegla schmitti females incubate egg mass during colder months and its juveniles hatch mainly in spring, as most Aegla Leach, 1820 species occurring in southeastern and southern Brazil.
Resumo
A study on population structure of Aegla schmitti Hobbs III, 1979 was carried out at Mananciais da Serra, in the municipality of Piraquara, state of Paraná, Brazil (25º29'S, 48º58'W). The following aspects were treated: temporal fluctuation in abundance, sex ratio, reproductive period and size composition based on carapace length. The animals were colleted with traps, nets, measured and returned to the reservoirs. This population was sampled monthly, in two reservoirs (Carvalho and Carvalhinho) constructed in the headwater streams with swift current and steep gradient, located on west side of Serra do Mar mountains, from November, 2004 to January, 2006. The water temperature varied from 11.0 (July, 2005) to 18.2ºC (March, 2007), dissolved oxygen from 7.0 to 9.5 mg/l and pH from 4.8 to 6.7, during collection period. A total of 1230 individuals were collected, among which, 819 were males and 411 females (30 ovigerous). The abundance varied from 23 (December, 2004) to 122 (June, 2005) crabs and the sex ratio of the whole population was 1:0.5 (M:F). Male carapace length varied from 4.38 to 36.46 mm and female, from 4.28 to 32.56 mm. Ovigerous females occurred from April, 2005 to November, 2005. Higher crab abundance was recorded in the Carvalho Reservoir, which explained by the presence of numerous breaches on the old tank walls that acted as shelters for these animals. Aegla schmitti females incubate egg mass during colder months and its juveniles hatch mainly in spring, as most Aegla Leach, 1820 species occurring in southeastern and southern Brazil.
Resumo
A study on population structure of Aegla schmitti Hobbs III, 1979 was carried out at Mananciais da Serra, in the municipality of Piraquara, state of Paraná, Brazil (25º29'S, 48º58'W). The following aspects were treated: temporal fluctuation in abundance, sex ratio, reproductive period and size composition based on carapace length. The animals were colleted with traps, nets, measured and returned to the reservoirs. This population was sampled monthly, in two reservoirs (Carvalho and Carvalhinho) constructed in the headwater streams with swift current and steep gradient, located on west side of Serra do Mar mountains, from November, 2004 to January, 2006. The water temperature varied from 11.0 (July, 2005) to 18.2ºC (March, 2007), dissolved oxygen from 7.0 to 9.5 mg/l and pH from 4.8 to 6.7, during collection period. A total of 1230 individuals were collected, among which, 819 were males and 411 females (30 ovigerous). The abundance varied from 23 (December, 2004) to 122 (June, 2005) crabs and the sex ratio of the whole population was 1:0.5 (M:F). Male carapace length varied from 4.38 to 36.46 mm and female, from 4.28 to 32.56 mm. Ovigerous females occurred from April, 2005 to November, 2005. Higher crab abundance was recorded in the Carvalho Reservoir, which explained by the presence of numerous breaches on the old tank walls that acted as shelters for these animals. Aegla schmitti females incubate egg mass during colder months and its juveniles hatch mainly in spring, as most Aegla Leach, 1820 species occurring in southeastern and southern Brazil.