Digestive morphophysiology of Gryllodes sigillatus (Orthoptera: Gryllidae)

Abstract

The evolution of the digestive system in the Order Orthoptera is disclosed from the study of the morphophysiology of the digestive process in its major taxa. This paper deals with a cricket representing the less known suborder Ensifera. Most amylase and trypsin activities occur in crop and caeca, respectively. Maltase and aminopeptidase are found in soluble and membrane-bound forms in caeca, with aminopeptidase also occurring in ventriculus. Amaranth was orally fed to Gryllodes sigillatus adults or injected into their haemolymph. The experiments were performed with starving and feeding insects with identical results. Following feeding of the dye the luminal side of the most anterior ventriculus (and in lesser amounts the midgut caeca) became heavily stained. In injected insects, the haemal side of the most posterior ventriculus was stained. This suggested that the anterior ventriculus is the main site of water absorption (the caeca is a secondary one), whereas the posterior ventriculus secretes water into the gut. Thus, a putative counter-current flux of fluid from posterior to anterior ventriculus may propel digestive enzyme recycling. This was confirmed by the finding that digestive enzymes are excreted at a low rate. The fine structure of midgut caeca and ventriculus cells revealed that they have morphological features that may be related to their involvement in secretion (movement from cell to lumen) and absorption (movement from lumen to cell) of fluids. Furthermore, morphological data showed that both merocrine and apocrine secretory mechanisms occur in midgut cells. The results showed that cricket digestion differs from that in grasshopper in having: (1) more membrane-bound digestive enzymes; (2) protein digestion slightly displaced toward the ventriculus; (3) midgut fluxes, and hence digestive enzyme recycling, in both starved and fed insects.

Morphology and fine organization of the midgut of Gampsocleis gratiosa (Orthoptera: Tettigoniidae)

“…Three midgut epithelial cell types, principal, regenerative and endocrine cells, were observed in G . gratiosa , similar to previous reports for other Orthoptera members [5, 12, 14, 16]. Endocrine cells in insect midgut perform important roles by releasing various peptides in many key physiological functions, and the kind and distribution of regulatory peptides vary with different species [17].…”

“…In Orthoptera, the caeca usually originate at the anterior end of the midgut. In Gryllidae, the two caeca are bulbous in shape [5, 14], whereas six bi-lobed finger-shaped caeca occur in Caelifera [2]. The midgut of G .…”

“…gratiosa consists of two bulbous gastric caeca and a cylindrical ventriculus. The gastric caeca originate at the anterior end of the ventriculus, similar to other members of Ensifera, e.g., Melanogryllus desertus (Orthoptera: Gryllidae) [14], Mecopoda niponensis (Orthoptera: Mecopodidae) [9], and Gryllodes sigillatus (Orthoptera: Gryllidae) [5]. Epithelial folds can increase the area of the midgut and are commonly observed in the gastric caeca.…”

“…gratiosa , epithelial folds were observed at the distal end of both gastric caeca, similar to those in G . sigillatus [5] and M . niponensis [9].…”

Dietary and phylogenetic correlates of digestive trypsin activity in insect pests

“…There are many examples in which phylogenetically distant species, despite having similar feeding habits, exhibit large differences in compartmentalization and midgut pH gradients (Terra & Ferreira, ). The highest trypsin activity or amounts of trypsin‐encoding mRNAs occur in midgut caeca of Orthoptera (Biagio et al., ), the anterior midgut of Phthiraptera (Waniek et al., ), Phasmida (Monteiro et al., ), Hymenoptera (Schumaker et al., ), and Lepidoptera (Jordão et al., ; Bolognesi et al., ), the anterior and/or posterior midgut of Coleoptera (Zhu & Baker, ; Hernández et al., ; Vinokurov et al., ,b; Lončar et al., ) and Diptera (Billingsley & Hecker, ; Muharsini et al., ; Do Vale et al., ; Dorrah et al., ), and the posterior midgut of Dictyoptera (Elpidina et al., ; Vinokurov et al., ). On the other hand, in some species trypsin distribution along the digestive tract is more related to feeding habit.…”