Effects of shape variations on the energy metabolism of the sand cricket Gryllus firmus: a geometric morphometric analysis

Respiration and energy metabolism are key processes in animals, which are severely constrained by the design of physical structures, such as respiratory structures. Insects have very particular respiratory systems, based on gas diffusion across tracheae. Since the efficiency of the tracheal respiratory system is highly dependent on body shape, the pattern of morphological variation during ontogeny could have important metabolic consequences. We studied this problem combining through-flow respirometry and geometric morphometrics in 88 nymphs of the sand cricket, Gryllus firmus. After measuring production in each individual, we took digital photographs and defined eight landmarks for geometric morphometric analysis. The analysis suggested that ontogenic deformations were mostly related to enlargement of the abdomen, compared to thorax and head. We found that (controlling for body size) metabolic variables and especially resting metabolism are positively correlated with a shape-component associated to an elongation of the abdomen. Our results are in agreement with the mechanics of tracheal ventilation in orthopterans, as gas circulation occurs by changes in abdominal pressures due to abdominal contractions and expansions along the longitudinal axis.

Pectinaria chilensis NILSSON, 1928 (POLYCHAETA: PECTINARIIDAE): taxonomic characterization, new distributional records and ecological notes from the chilean coast

Se revisa Pectinaria chilensis de la costa de Chile a partir de ejemplares recolectados en fondos blandos sublitorales, entre 45 y 93m de profundidad, en cuatro localidades del norte de Chile. Estos especímenes fueron comparados con ejemplares recolectados a 17m de profundidad en Coronel, Golfo de Arauco, Chile, localidad tipo de la especie. Se incluye una caracterización taxonómica, ilustraciones, y nuevas localidades en la distribución geográfica de la especie. Se provee información del hábitat (batimetría, tipo de sedimento, contenido de materia orgánica total y O2 disuelto de fondo) y se incluye una clave para diferenciar las dos especies de Pectinariidae registradas en Chile.

The taxonomy, geographical distribution, and ecological aspects of Pectinaria chilensis are reviewed. Specimens were collected in sublittoral soft bottoms, between 45 and 93m depth, at four localities in northern Chile. These specimens are compared with individuals collected from 17m depth at Coronel, Gulf of Arauco, Chile, the type locality of the species. A taxonomic characterization, illustrations and a list of new localities in the geographical distribution of this species are presented. Ecological information (bathymetry, sediment type, total organic matter content and dissolved O2 concentration of sea water above the bottom) is included, as well as a key for differentiating the two Pectinariidae species registered in Chile to date.

Revisa-se Pectinaria chilensis da costa do Chile a partir de exemplares recolhidos em fundos brandos sub-litorais, entre 45 e 93m de profundidade, em quatro localidades ao norte do Chile. Estes espécimes foram comparados com exemplares recolhidos a 17m de profundidade em Coronel, Golfo de Arauco, Chile, localidade padrão da espécie. Se inclui uma caracterização taxonômica, ilustrações, e novas localidades na distribuição geográfica da espécie. Se fornece informação do hábitat (batimetria, tipo de sedimento, conteúdo de matéria orgânica total e O2 dissolvido de fundo) e se inclui uma clave para diferenciar as duas espécies de Pectinariidae registradas no Chile.