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Reproductive strategy is a central feature of the ecology of invasive species as it determines the potential for population increase and range expansion. The red swamp crayfish, Procambarus clarkii, has invaded many countries and caused serious problems in freshwater ecosystems. However, little is known about the effects of environmental conditions on crayfish paternity and offspring traits in the wild. We studied these reproductive characteristics of P. clarkii in wild populations from two different habitats (ponds and ditches) in three locations with different environmental conditions in China. Genotyping of 1,436 offspring and 30 mothers of 30 broods was conducted by using four microsatellites. An analysis of genotyping results revealed that gravid females were the exclusive mother of the progeny they tended. Twenty-nine of 30 mothers had mated with multiple (2-4) males, each of which contributed differently to the number of offspring in a brood. The average number of fathers per brood and the number of offspring per brood were similar (P > 0.05) among six sampling sites, indicating that in P. clarkii multiple paternity and offspring number per brood are independent of environmental conditions studied. Indirect benefits from increasing the genetic diversity of broods, male and sperm competition, and cryptic female choice are a possible explanation for the high level multiple paternity and different contribution of fathers to offspring in this species.

In this paper, magnesium-doped calcium copper titanate (M-CCTO) submicron particles, which had high dielectric constant by a broadband dielectric analyzer, were successfully designed and prepared by the coprecipitation method. Then, the silicone elastomer filled with M-CCTO particles had high dielectric constant, low dielectric loss, and actuated strain which was greatly improved in low electric field. Compared with CCTO/commercial polydimethyl siloxane (PDMS) composites, M-CCTO/PDMS composites with 2 wt% content exhibited higher actuated strain, which increased 41.6% in a low electric field of 10 V/lm. It is found that the Mg doping enhanced the change in actuated strain approximately to 2 times in pure silicone elastomer, as well. Our work provided a simple, low-cost and effective method to prepare high performance dielectric elastomers (DEs), which facilitated the wide application of DEs composites, especially in the biological and medical fields such as biosensors, artificial muscles, and prosthetics. POLYM. COMPOS., 39:691-697,

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