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Based on morphological and molecular evidence, three new earthworm species of the genera AmynthasKinberg, 1867 and MetaphireSims and Easton, 1972 from Leshan City of southwest China's Sichuan Province were identified in this study. They are named Amynthas agenesis sp. nov., Metaphire jinhensis sp. nov., and M. ebianensis sp. nov. All three new species have a large size (the dimensions of the adult body are more than 200 mm × 10 mm) and three pairs of spermathecal pores in 6/7–8/9. Although these three new species are morphologically somewhat similar to the other species in the same group, they are distinguishable in several morphological characteristics. Metaphire jinhensis sp. nov. has paired and bunchy ovaries that are attached to septa 12/13. Metaphire ebianensis sp. nov. has large and well-developed prostate glands, and each of its seminal vesicles has a dorsal lobe. Amynthas agenesis sp. nov. has accessory glands in spermathecae, prostate, and intestinal caeca regions. The maximum likelihood tree was constructed based on the mitochondrial cytochrome c oxidase subunit I gene, and it showed that the three new species are clustered on different branches. Besides, phylogenetic trees also suggested that the genera Amynthas and Metaphire did not evolve separately within their respective taxa and thus were not monophyletic. This study provides a detailed taxonomic characterization of three new species and helps to better understand the species diversity of earthworms, which is urgently needed to ensure the ecological stability of wild earthworms.
Phenotypic plasticity, the ability of organisms to change their phenotype depending on external stimuli, enables their survival in fluctuating environments. An extreme example is polyphenism, in which a single genotype produces discrete phenotypes in response to external cues. However, under persistent environmental conditions, natural selection would favor reduced plasticity. This study focused on the loss of reproductive polyphenism and revealed the underlying mechanism in the pea aphid Acyrthosiphon pisum. Although most populations exhibit reproductive polyphenism, known as cyclical parthenogenesis, with a seasonal shift between parthenogenesis and sexual reproduction, some exhibit obligate parthenogenesis. To investigate the potential role of changes in the environmental sensitivity of the juvenile hormone (JH) pathway during this evolutionary shift, we analyzed the expression of genes involved in JH synthesis and degradation. We found that five of seven JH-related genes exhibited photoperiodic responses in one cyclical-parthenogenetic strain, whereas none of them responded to photoperiod in the two obligate-parthenogenetic strains. Notably, CYP15A and JHEH genes, which are involved in the final step of JH synthesis and in the initiation of JH degradation, respectively, showed strong photoperiodic responses in the cyclical-parthenogenetic strain but showed no responses in the obligate-parthenogenetic strains. Acetone treatment induces male production in obligate-parthenogenetic strains, suggesting that the developmental pathway for male production remains functional in these strains. These results suggest that the loss of the photoperiodic response in both JH synthesis and degradation pathways is a key mechanism underlying the elimination of the sexual phase, resulting in the loss of reproductive polyphenism in aphids.
Cephalopods, as prey for predators of various taxa, frequently experience arm loss. Arm loss in octopods may arise not only from predation pressure but also species-specific reproductive ecology. Therefore, investigating the occurrence of arm loss may provide insights into various aspects of octopods' reproductive ecology. In this study, we explored the seasonal and sexual differences in arm loss occurrences in two small octopus species, the Japanese pygmy octopus, Octopus parvus, and the Japanese blue-lined octopus, Hapalochlaena cf. fasciata. Notably, O. parvus exhibited a higher arm loss rate compared with previously studied species, potentially attributable to its relatively small size and sublethal predation by large crabs sharing the species' intertidal habitat. Regarding H. cf. fasciata, arm loss in males and females tended to increase toward the spawning season, with males experiencing a more rapid increase. The smaller size of males and arm loss due to male–male conflict related to reproduction and sexual cannibalism during copulation are likely contributing factors. Additionally, the impact of arm loss on egg retention and protective measures may prompt females to adopt behaviors minimizing the risk of arm loss.
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