摘要: Insect growth and development are precisely controlled by hormone homeostasis. The prothoracicotropic hormone (PTTH) receptor, Torso, is a member of the receptor tyrosine kinase family in insects. Activation of Torso by PTTH triggers biosynthesis and release of the steroid hormone in the prothoracic gland (PG). Although numbers of genes functioning in steroid hormone synthesis and metabolism have been identified in insects, the PTTH transduction pathway via its receptor Torso is poorly understood. In the current study, we describe a loss-of-function analysis of Torso in the silkworm, Bombyx mori, by targeted gene disruption using the transgenic CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/RNA-guided Cas9 nucleases) system. Depletion of B. mori Torso (BmTorso) did not eventually affect larval ecdysis and metamorphosis processes. Instead, BmTorso deficiency resulted in significant extension of developing time during larval and pupal stages with increased pupa and cocoon sizes. The ecdysteriod titers in the hemolymph of BmTorso mutants sharpy declined. Transcriptional levels of genes involved in ecdysone biosynthesis and ecdysteroid signaling pathways were significantly reduced in BmTorso-deficient animals. Additionally, RNA-Seq analysis revealed that genes involved in the longevity pathway and protein processing in the endoplasmic reticulum pathway were affected after BmTorso deletion. These results indicate that Torso is critical for maintaining steroid hormone homeostasis in insects.

摘要: Although radicle pruning has well been observed in plant-animal interactions, research has not been conducted to determine how radicle pruning by seed-eating animals regulates nutrition mobilization of cotyledonary reserves and absorption of soil nutrients. We used stable nitrogen isotopes to test how acorns of early-germinating oak species (Quercus variabilis,Q. aliena, andQ. mogolica) trade off nutrients in the cotyledons and those in the soil in response to radicle pruning by seed-eating rodents. Radicle pruning by rodents resulted in root branching in the 3 early-germinating oak species. Moreover, radicle pruning increased shoot dry weight and substantially reduced the root-to-shoot ratio of oak species. Corresponding to the decreased dry weight of roots and root-to-shoot ratio, the dry weight of the remnant cotyledons was higher after radicle pruning in the 3 oak species. We provided first evidence that radicle pruning by seed-eating animals improved seedling performance of early-germinating oaks by increasing absorption of nutrients from soil. The results indicate that early-germinating oak seedlings trade off nutrition budget by altering nutrient absorption from soil and reserve mobilization from cotyledons in response to radicle pruning by seed-eating animals. Our study provided new insight into the nutrition allocation mechanism of young seedlings in response to radicle pruning by seed-eating animals, reflecting a mutualistic interaction between early-germinating oak and food-hoarding animals.

摘要: The ingestion of organic and mineral materials by earthworms is a prominent functional role that has profound consequences for the decomposition and stabilization of soil organic matter. To investigate the litter consumption of the African nightcrawler earthworm Eudrilus eugeniae under different tropical conditions, we used DNA barcoding to identify specimens of E. eugeniae collected from sites across the Adamawa region in Cameroon, and studied the influence of habitat suitability (soil properties), soil moisture, litter type, and population density on litter consumption. A total of four litter consumption experiments were carried out using soils collected from refuse disposal sites, agricultural lands, and savannahs dominated by the Mexican sunflower Tithonia diversifolia. The results revealed that litter consumption significantly increased in the refuse disposal and agricultural soils as opposed to the Mexican sunflower (T. diversifolia) soil, a cow dung enriched substrate, and a sterile soil horizon from the savannah (P < 0.05). The optimum moistures for litter consumption were between 24% and 50%. Litter type did not affect the consumption rate of the earthworms (P > 0.05). We observed a general positive density-dependent consumption with litter mass loss increasing with increasing density. Our results suggest that E. eugeniae has a strong direct effect on the decomposition of plant materials than expected from previous estimations, and that litter consumption rates are determined by several habitat components and population density.

摘要: The diet of juvenile, including hatchlings and presumed yearlings of the Saltwater Crocodile, Crocodylus porosus, was studied at the Kuching Wetlands National Park, western Sarawak, East Malaysia (Borneo), using both frequency of occurrence and volumetric composition of diet through the stomach flushing technique. Crustaceans form the primary component of the diet of juvenile crocodiles, comprising shrimps of the family Atyidae (Caridina sp., and Penaeus indicus), occurring in the stomach of 17 individuals (53% by occurrence). An estimated 91.7% of hatchlings stomach-flushed had shrimps, and the emergence of hatchlings may be associated by inland migration of its shellfish prey, as reported in the literature. The secondary food item of hatchlings and presumed yearlings was ocypodid crabs, occurring in 16 individuals (in addition to a subadult), and comprise 47%-50% by occurrence. Other items taken incidentally include rodents (in large yearlings, exceeding 100 cm in total length), and fish (in seven hatchlings and in one subadult), or in 29% of total individuals captured (47.7% in hatchlings and 15% in yearlings). A dietary change in ontogeny is therefore evident, as reported earlier in crocodilians.

摘要: Variation in age structure and body size benefits are identified to understand the evolution of life history. Here, we estimated the age structure and body size of two species of odorous frogs (Odorrana margaretae and Odorrana grahami) by using skeletochronology. The ages at sexual maturity of O. grahami and O. margaretae in both sexes were 1 and 2 years, respectively. For both sexes, the maximum age observed in O. margaretae was six years. For O. grahami, the maximum age observed in males and females were 4 and 5 years, respectively. Males and females did not differ in mean age in the two species. The average body size of both species considerably differed between sexes, with females being larger than males. The body size of females was also larger than that of males when the effect of age was removed. We also found positive correlations between body size and age within each sex in O. margaretae, but only for female in O. grahami. The female-biased sexual size dimorphism of the two species suggested that fecundity selection for larger female size may increase the reproductive output.