关键词: 花绒寄甲, 人工饲料, 肠道微生物, 16S rDNA, 生长发育, 繁殖

Abstract: 【Aim】The artificial breeding and propagation of Dastarcus helophoroides have been successfully achieved indoors. However, different diet formulae have significant effects on the growth and development of D. helophoroides adults and their offspring. According to the artificial diets allocated by D. helophoroides adults under field conditions, whether they are suitable for the growth and development of long-term indoor breeding population at this stage needs to be further studied. The aim of this study is to investigate the effects of different diets on the growth and development, reproduction and the adult intestinal bacterial community of D. helophoroides, so as to provide a theoretical basis for optimizing diet formula.【Methods】Six different diet formulae ［dry yeast 10 g+sucrose 3 g+agar 3 g+freeze-dried egg yolk powder 9 g+purified water 40 mL(Ⅰ), wood flour 5 g+dry yeast 10 g+sucrose 3 g+agar 3 g+freeze-dried egg yolk powder 9 g+purified water 35 mL (Ⅱ)， silkworm pupa powder 10 g+dry yeast 10 g+sucrose 3 g+agar 3 g+freeze-dried egg yolk powder 9 g+purified water 30 mL(Ⅲ), dry powder of Zophobas atratus 10 g+dry yeast 10 g+sucrose 3 g+agar 3 g+freeze-dried egg yolk powder 9 g+purified water 30 mL(Ⅳ)， wood flour 5 g+silkworm pupa powder 10 g+dry yeast 10 g+sucrose 3 g+agar 3 g+freeze-dried egg yolk powder 9 g+purified water 25 mL(Ⅴ) and wood flour 5 g+dry powder of Z. atratus 10 g+dry yeast 10 g+sucrose 3 g+agar 3 g+freeze-dried egg yolk powder 9 g+purified water 25 mL(Ⅵ)］ were prepared and used to feed the newly emerged adult of D. helophoroides, using the newly emerged adult of D. helophoroides fed with no diet as the control group. Parameters including the adult body weight, body length, body width, cumulative mortality in 64 d, pre-oviposition period, average daily number of eggs laid per female and total number of eggs laid per female in 64 d of the parental generation were recorded. Additionally, parameters including the hatching rate, larval parasitism rate, cocooning rate, larval duration, cocoon period, and eclosion rate of the first-generation offspring of D. helophoroides were measured. At the same time, the Illumina NovaSeq was utilized to sequence the V4-V5 variation regions of 16S rDNA of the intestinal bacteria in the newly emerged adult of D. helophoroides fed with different diets. The diversity, species composition, and community structure differences of the intestinal bacteria were analyzed, and the gene function of the intestinal bacteria was predicted. The correlation analysis between the abundance of the core intestinal bacteria and various physiological parameters was conducted to elucidate the intestinal bacteria highly associated with the growth and development, and reproduction of D. helophoroides.【Results】 The body weight (0.0287 g) of D. helophoroides adults fed with diet Ⅵ was the highest. The total number of eggs laid per female in 64 d of D. helophoroides adults fed with diet Ⅵ was the highest (1 199.03 grains), followed by that of D. helophoroides adults fed with diet Ⅳ (1 068.19 grains), and those of D. helophoroides adults fed with dietsⅠ and Ⅲ were the lowest (756.11 and 732.61 grains, respectively). The body length (8.1319 cm) and cumulative mortality in 64 d (18.05%) of D. helophoroides adults fed with diets Ⅲ and Ⅱ, respectively, were the highest. Meanwhile, the pre-oviposition period of adult D. helophoroides fed with diets IV－VI was the shortest, averaging (21.44±0.20) d. The hatching rate and eclosion rate of the first-generation offspring of D. helophoroides from the adults fed with diet VI were the highest, and significantly higher than those from the adults fed with diets I and II. The larval parasitism rate (85.36%) and cocooning rate (97.34%) of the first-generation offspring of D. helophoroides from the adults fed with diets Ⅱ and Ⅲ, respectively, were the highest. A total of 4 781 552 optimized sequences of 16S rDNA were obtained from the intestinal bacteria of the newly emerged adults of D. helophoroides. A total of 758 operational taxonomic units (OTUs) were obtained by clustering analysis, and were annotated into 11 phyla, 22 classes, 40 orders, 63 families and 90 genera. At the phylum level, the intestinal dominant bacteria were Firmicutes and Protebacteria. At the genus level, the dominant intestinal bacteria of the newly emerged adults fed with diet was Lactococcus, with the abundance significantly increased compared to that of the control group. The relative abundance of the genus Lactococcus in the intestine of adults fed with diets IV－VI also gradually increased with feeding time. The results of alpha diversity analysis indicated that the intestinal bacterial diversity in the control group was the highest, while feeding on different diets resulted in a decreased intestinal bacterial diversity. Beta diversity analysis results showed that the adult intestinal bacterial community structure of the control group differed greatly from that fed with different diets. However, the intestinal bacterial community structure among adults fed with different diets was similar. KEGG analysis results revealed that the intestinal bacterial genes involved in metabolic pathways in adults fed with different diets at different time points were similar to those in the control group， with no significant differences. The abundance of core intestinal bacteria was correlated with adult growth, reproduction, and offspring larval adaptability. The presence of Pediococcus with higher relative abundance may reduce the hatching rate of the first-generation offspring, while Enterococcus may shorten the pre-oviposition period of the parent adults, reduce the larval parasitism rate and increase the eclosion rate of the first-generation offspring. However, Enterococcus had opposite effects in pre-oviposition period with Lactobacillus and in eclosion rate with Bacillus, respectively.【Conclusion】 Feeding on different diets significantly affects the adult growth and development, reproduction and intestinal microbes, and offspring fitness of D. helophoroides. Adults fed with artificial diet VI, which contained dry powder of Z. atratus and wood powder, exhibited the highest reproductive capacity and highest offspring fitness, indicating that this diet is more suitable for long-term indoor rearing of D. helophoroides populations. Concurrently, the intestinal bacterial underwent change in community structure as a result of feeding on different diets, leading to the decreased bacterial abundance and diversity but increased relative abundance of Lactococcus. Lactococcus may play an important role in the reproduction of adults and the growth and development of larvae, offering important references for improving the indoor breeding of D. helophoroides.

Key words: Dastarcus helophoroides, artificial diet, intestinal microbes, 16S rDNA, growth and development, reproduction