Hemocyte profiles of Hierodula tenuidentata and Empusa fasciata under starvation, dietary variation, and thermal stress.

Abstract

Insect immunology represents a critical component of circulatory physiology research. Considering the ecological significance of mantids and their predatory roles, this study investigated the types of hemocytes and their modulation by starvation, prey quality, and temperature in Hierodula tenuidentata and Empusa fasciata. This study also documents the presence of these two species in Semnan province, Iran for the first time, expanding our knowledge of their distribution. Field-collected oothecae were incubated under controlled conditions (temperature 25 ± 1°C, relative humidity 50%, and a photoperiod of 14:10 light:dark hours) until nymphal emergence. Following hemolymph extraction and staining with Giemsa solution, four hemocyte types - prohemocytes, plasmatocytes, granulocytes, and oenocytoids - were identified in both species; spherulocytes appeared exclusively in adult H. tenuidentata under a light microscope. Differential hemocyte counts revealed granulocytes as predominant in H. tenuidentata, whereas both granulocytes and plasmatocytes were abundant in E. fasciata across developmental stages. Prohemocytes were more abundant in the early-instar nymphs than in the late-instar nymphs of both mantids. Hemocyte density declined progressively with prolonged starvation, reaching a minimum after 4 days. The highest hemocyte concentrations were observed in mantids fed grasshoppers after 1 week, whereas markedly lower counts occurred with low-quality prey, such as Musca domestica L. (Diptera: Muscidae) and Lycaena sp. (Lepidoptera: Lycaenidae). Heat stress significantly elevated hemocyte density, whereas cold exposure induced substantial reductions in hemocyte density. Hemocyte fluctuations were more pronounced after 48 hours than after 24 hours. These findings suggest that short-term dietary deprivation, prey type, and thermal stress may rapidly alter immune profiles in H. tenuidentata and E. fasciata.