ABSTRACT
Insects in many species vary greatly in the expression of secondary sexual traits, resulting in sexual dimorphism, which has been proposed to be a consequence of differences in sexual selection. In this study, we analyze the occurrence of sexual shape dimorphism and the correlation between geometric body size in males and females and sex ratio in the genus Ceroglossus (Coleoptera: Carabidae) using geometric morphometrics and randomization analysis. Our results show a positive relationship between the centroid size of males and females and sex ratio. However, we also observed a trend to maintain a "similar" body shape between sexes and species due to characteristics associated with sexual selection of the group in which the scarcity of outstanding morphological characters does not restrict reproduction capacity. The trend in sexual proportions was found to be near 1:1 for the eight species. We propose that the observed differences between sexes associated with the sex ratio are due to an energy cost caused by sexual selection; nevertheless, since proportions are similar for all the species, it is really not relevant to generate more conspicuous structures for a stronger male-male competence.
Subject(s)
Body Size , Coleoptera/physiology , Sex Ratio , Animals , Female , MaleABSTRACT
The alteration of habitat generates different degrees of stress in insects. It has been suggested that the degrees of phenotypic disturbances reflect the ability of an individual to overcome the effects of stress. The Baker River Basin in the Aysén Region, Chilean Patagonia has a very fragmented landscape, due to the destruction of the native forest and the use of land for agriculture and animal husbandry. This alteration should generate different degrees of disturbances in the insect communities, whose effects may be quantified by geometric morphometric tools. We analyzed morphological differences in 244 males and 133 females of the the Chilean magnificent beetle, Ceroglossus chilensis (Eschscholtz) (Coleoptera: Carabidae) collected in January, 2007, in mixed forests of Nothofagus dombeyi Mirbel (Ørsted) (Fagales: Nothofagaceae) and N. nitida Hofmus and in Second-growth forest of N. pumilio (Poepp. & Endl.) Krasser. Males were generally wider in the pronotum, while females had wider abdominal sternites. Although there were significant differences in shape and size between mature forests and second-growth forest, these were less significant among the sites within each type of vegetal formation. Individuals had more shape variations in the mature forest. We suggest that differences in shape are due at least in part to the isolation of the habitat. The differences found between sexes raises the question of how morphological variations and sexual dimorphism may be affected spatially by natural selection.
Subject(s)
Coleoptera/anatomy & histology , Ecosystem , Sex Characteristics , Animals , Biometry , Chile , Female , MaleABSTRACT
Reproduction and ultrastructure of egg and first instar larvae of Gyriosomus kingi (Coleoptera: Tenebrionidae) from the desert of Atacama. Gyriosomus is an important Chilean genus of Tenebrionidae, inhabiting the coastal desert of this country. in this environment, the Gyriosomus-species are both eremic and endemic components of the epigean entomofauna. Despite the ecological importance of these species in the Chilean desert, there is a lack of knowledge on the preimaginal stages of them. in this paper we describe the egg and first instar larval morphology of G. kingi Reed, 1873, along with some bionomic aspects of the female. The eggs and larva were obtained from couples kept under laboratory conditions, after being captured during the spring of year 2002, in coastal sites of National Park Llanos de Challe, located in the southern border of the Atacama Desert (28°01S, 71°03W). The first third of the chorion presents subhexagonal cells lacking aeropyles. The larvae is oligopod and elongated. its cephalic capsule is strongly chitinized with the prothoracic legs longer and thicker than the rest. According laboratory observations, each egg-laying includes seven to ten eggs each time, with a maximum of six egg-laying per female. The eggs are buried into the soil, covered by a mucilaginous layer which creates a clay-sandy film attached to the chorion. Rev. Biol. Trop. 55 (2): 637-644. Epub 2007 June, 29.
Gyriosomus es un importante género chileno de Tenebrionidae, habitante del desierto costero del país. En este ambiente, las especies de Gyriosomus son un componente erémico y endémico de la entomofauna epígea. A pesar de la importancia ecológica que estas especies tienen en el desierto chileno, poco se conoce respecto de la morfología de los estados preimaginales. En este trabajo se describe la morfología del huevo y de la larva de primer estadio de G. kingi Reed, 1873, y se entregan algunos antecedentes acerca de la bionomía de la hembra. Los huevos y las larvas fueron obtenidos a partir de parejas mantenidas en condiciones de laboratorio. Los adultos fueron capturados durante la primavera del año 2002, en sitios costeros del Parque Nacional Llanos de Challe, localizado en la frontera sur del Desierto de Atacama (28°01S; 71°03W). El primer tercio del corión del huevo presenta celdas subhexagonales sin aeropilas. La larva es oligópoda y elongada. Su cápsula cefálica está fuertemente quitinizada y sus patas protorácicas son más largas y más gruesas que las restantes. Según observaciones de laboratorio, cada ovipostura incluye de siete a diez huevos cada vez, con un máximo de seis oviposturas por hembra. Los huevos son enterrados en el suelo, recubiertos con un mucílago que genera una película de arena-arcilla adherida al corión.
Subject(s)
Animals , Female , Coleoptera/ultrastructure , Ovum/ultrastructure , Coleoptera/classification , Coleoptera/physiology , Chile , Larva/ultrastructure , ReproductionABSTRACT
Two leech species were found parasitizing the shrimp Cryphiops caementarius from Limarí river, Chile. These ectoparasites can act as population regulators or development inhibitors in their host; however the biological characteristics of this host-parasite interaction are unknown. We analyze the inter-specific differences of the parasitism and its relation with host size and sex using quantitative descriptors. Abundance, prevalence, intensity and range were estimated with respect to host size and sex. The leeches belong to two species of Glossiphonidae: Helobdella triserialis and H. duplicata. Forty-seven percent of the hosts were parasitized by one or both leech species. H. triserialis was found only in the pleopod of the hosts with the highest prevalence values (42%), intensity (2.9) and range (1-11). H. duplicata was found only in the branchial filaments with 7 % prevalence, an intensity of 1.7 and a range of 1-4. The host's total length and sex can explain the variation in leech intensity and infection prevalence. However, when only the host's sex is considered, prevalence only increased with size in female hosts. Morphological characteristics of the females could explain the greater H. triserialis intensity in the base of the pleopod and would be related to a greater abdomen development.
Subject(s)
Animals , Male , Female , Host-Parasite Interactions , Palaemonidae/parasitology , Leeches/physiology , Chile , Sex Factors , Palaemonidae/anatomy & histology , Prevalence , Rivers , Leeches/classification , Body SizeABSTRACT
Gyriosomus is an important Chilean genus of Tenebrionidae, inhabiting the coastal desert of this country. In this environment, the Gyriosomus-species are both eremic and endemic components of the epigean entomofauna. Despite the ecological importance of these species in the Chilean desert, there is a lack of knowledge on the preimaginal stages of them. In this paper we describe the egg and first instar larval morphology of G. kingi Reed, 1873, along with some bionomic aspects of the female. The eggs and larva were obtained from couples kept under laboratory conditions, after being captured during the spring of year 2002, in coastal sites of National Park Llanos de Challe, located in the southern border of the Atacama Desert (28 degrees 01' S, 71 degrees 03' W). The first third of the chorion presents subhexagonal cells lacking aeropyles. The larvae is oligopod and elongated. Its cephalic capsule is strongly chitinized with the prothoracic legs longer and thicker than the rest. According laboratory observations, each egg-laying includes seven to ten eggs each time, with a maximum of six egg-laying per female. The eggs are buried into the soil, covered by a mucilaginous layer which creates a clay-sandy film attached to the chorion.
Subject(s)
Coleoptera/ultrastructure , Ovum/ultrastructure , Animals , Chile , Coleoptera/classification , Coleoptera/physiology , Female , Larva/ultrastructure , ReproductionABSTRACT
Two leech species were found parasitizing the shrimp Cryphiops caementarius from Limarí river, Chile. These ectoparasites can act as population regulators or development inhibitors in their host; however the biological characteristics of this host-parasite interaction are unknown. We analyze the inter-specific differences of the parasitism and its relation with host size and sex using quantitative descriptors. Abundance, prevalence, intensity and range were estimated with respect to host size and sex. The leeches belong to two species of Glossiphonidae: Helobdella triserialis and H. duplicata. Forty-seven percent of the hosts were parasitized by one or both leech species. H. triserialis was found only in the pleopod of the hosts with the highest prevalence values (42%), intensity (2.9) and range (1-11). H. duplicata was found only in the branchial filaments with 7 % prevalence, an intensity of 1.7 and a range of 1-4. The host's total length and sex can explain the variation in leech intensity and infection prevalence. However, when only the host's sex is considered, prevalence only increased with size in female hosts. Morphological characteristics of the females could explain the greater H. triserialis intensity in the base of the pleopod and would be related to a greater abdomen development.
Subject(s)
Host-Parasite Interactions , Leeches/physiology , Palaemonidae/parasitology , Animals , Body Size , Chile , Female , Leeches/classification , Male , Palaemonidae/anatomy & histology , Prevalence , Rivers , Sex FactorsABSTRACT
Pleurodema thaul Lesson, 1826 es una especie de amplia distribución geográfica y gran variabilidad morfológica, por lo cual, se plantea el estudio de su parasitofauna para contribuir a dilucidar el estado taxonómico de las diferentes poblaciones. En este trabajo se da a conocer la composición taxonómica de la parasitofauna encontrada en una población local de P. thaul, ubicada en Concepción, además de características cuantitativas (prevalencia, intensidad y abundancia) y microhabitat de los taxa parasitarios encontrados. Se encontraron tres especies de nemátodos: aplectan chilensis, rhabdias sp. y oswaldocruzia sp. más una especie de protozoo coccidio del género eimeria, constituyendo los primeros registros para P thaul