Cellulose Digestion and Assimilation by Three Leaf‐shredding Aquatic Insects

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Abstract. The capacity of three leaf-shredding aquatic insects, Pteronarcys proteus (Plecoptera: Pteronarcidae), Tipula abdominalis (Diptera: Tipulidae), and Pycnopsyche luculenta (Trichoptera: Limnephilidae), to digest and assimilate cellulose was investigated. Pteronarcys nymphs collected from two second-order woodland streams over a 14-mo period exhibited high levels of cellulolytic activity in their alimentary tracts, especially in the anterior gut. Similar though slightly lower activity levels were measured in Pycnopsyche guts. Cellulolytic activity in Tipula larvae collected from the streams during the same period was low to absent, and when present, was concentrated in the hindgut. General proteolytic activity was similar in the alimentary tracts of all three species. Ecological Society of AmericaAssimilation of uniformly labelled 14C-cellulose was determined by a dual-label technique, and assimilation efficiencies were estimated at 11.2% for Pteronarcys, 18.5% for Tipula, and 12.0% for Pycnopsyche. Confirmation that labelled digestion products passed the gut wall in two species was obtained by in vitro label transport experiments. Ion exchange fractionation of labelled digestion products crossing the gut wall showed that >90% of the label was transported as organic acids and amino acids in Tipula, while >40% of the label crossing the gut wall in Pteronarcys was neutral sugar. Based on the label experiments and published information, we hypothesize that Tipula relies mainly on microbial endosymbionts for cellulose hydrolysis, while Pteronarcys accomplishes hydrolysis largely by means of acquired microbial enzymes obtained through ingestion of microbially conditioned detritus. This study demonstrates the potential for certain leaf-shredding stream insects to derive nutritional benefit from plant polysaccharides, although not without microbial mediation.

Consumption of aquatic bryophytes by alpine stream invertebrates in New Zealand

“…from New Zealand, have a very high midgut pH (Trought 1982;Sinsabaugh et al 1985;Barlocher & Porter 1986) which enhances digestibility of celluloses and hemicelluloses (Terra 1990). Their hindguts may also contain large populations of endosymbiotic bacteria that can digest these structural materials to the probable benefit of the host (Sinsabaugh et al 1985;Griffiths & Cheshire 1987;Terra 1990). Despite their relatively low nutritional value, bryophytes may therefore still represent a valuable food source to L. hudsoni if the larvae possess an appropriate digestive system.…”

Leaf choice by crustaceans in a mangrove forest in Queensland

“…It is currently believed that detritivores digest microbial organisms growing on detritus rather than the detritus itself, although a few studies show that plant detritus can supply Energy flow: the role of shredders Typically, shredders have high ingestion rates and low assimilation values (Sinsabough et al 1985). Similarly, about 68% of the material ingested by Sesarma erythrodactyla is egested as small particles and thus made available to species which collect small particles.…”

Isolation of Polymer-Degrading Bacteria and Characterization of the Hindgut Bacterial Community from the Detritus-Feeding Larvae of Tipula abdominalis (Diptera: Tipulidae)

“…The larva itself is not capable of tissue-level synthesis of cellulolytic enzymes (22), and it was proposed that the larvae benefit nutritionally from microbially mediated digestion of leaf lignocellulose, providing simple fermentation products which can be used by the larvae (13). Scanning electron microscopy studies demonstrated a dense and morphologically diverse microbial community in the hindgut of T. abdominalis larvae (12).…”