幼虫密度对草地螟血细胞数量和组成的影响

为了阐明幼虫密度对草地螟Loxostege sticticalis L.（鳞翅目： 螟蛾科）细胞免疫能力的影响， 本研究调查了在活体灰菜植株上1，5，10和20头/瓶（900 mL）4种密度条件下的其5龄幼虫血细胞种类、数量和组成。结果表明： 草地螟幼虫血淋巴中有原血细胞、浆血细胞、 颗粒血细胞、珠血细胞和类绛色血细胞等5种（类）血细胞。血细胞总数、 浆血细胞、颗粒血细胞数量随幼虫密度的增加而显著递增， 但原血细胞、珠血细胞和类绛色血细胞数量在幼虫密度间的差异不明显；各种血细胞所占血细胞总数的比例在4个密度中的排序相同， 但10和20头/瓶密度下的浆血细胞比例显著高于1头/瓶的，其余4种血细胞的比例在不同密度之间无显著差异。可见， 幼虫密度主要是通过影响草地螟幼虫浆血细胞和颗粒血细胞的数量及血细胞总数， 从而影响草地螟的细胞免疫能力。

Effects of larval density on the number and composition of hemocytes in the beet webworm, Loxostege sticticalis (Lepidoptera: Pyralidae)

To understand the roles of larval density in the cellular immunity of the beet webworm, Loxostege sticticalis L. (Lepidoptera: Pyralidae), the types, number and composition of hemocytes in its 5th instar larvae reared on intact plants of Chenopodium album L. at the density of 1, 5, 10, and 20 larvae/jar (900 mL) were investigated. Five types of hemocytes were identified from larval L. sticticalis, i.e., prohemocytes, granular hemocytes, plasmatocytes, spherulocytes and oenocytoids. The numbers of plasmatocytes, granular hemocytes and total hemocytes increased as the larval density increased, but the numbers of prohemocytes, spherulocytes, and oenocytoids were insignificantly affected by the larval density. The proportion of each hemocyte type to the total haemocetes ranked in a similar order in the four treatments but the ratios of plasmatocytes at the density of 10 and 20 larvae/jar were remarkably higher than that of the isolated larvae. These results suggest that the larval density can affect the number of plasmatocytes and granular hemocytes, and this impact in turn can affect the cellular immune capacity in larval L. sticticalis.