The structure and ultrastructure of the egg capsules of stoneflies of the genus Isoperla (Insecta, Plecoptera, Perlodidae).

The egg capsules of five systellognathan stoneflies species representing the genus Isoperla (Plecoptera, Perlodidae) have been investigated using light and electron microscopes (SEM and TEM). We consider the structural modifications of egg coverings (egg capsules, eggshells) like: a shape of a capsule, presence of structures fixing an egg to the substratum under water, intrachorionic aeropylar system facilitating gas exchange as a factor adapting an egg/embryo to the environment. The structures protecting eggs against desiccation during a female flight before oviposition into water as well as against the dangers of external mechanical injury caused by turbulences in rapid water currents of mountain streams are described and discussed. The ground plan of the egg capsule in arctoperlarian stoneflies is also discussed.

The structure and ultrastructure of the egg capsule of Brachyptera risi (Plecoptera, Nemouroidea, Taeniopterygidae) with some remarks concerning choriogenesis.

The organization of the egg capsule of the euholognathan stonefly, which represents the family Taeniopterygidae (Nemuroidea) was investigated using light and electron microscopy techniques. The presence of a complex, multilayered egg capsule, composed of a vitelline envelope, multilayered chorion, and extrachorion is described. The morphology of the eggshell of Brachyptera risi was compared with that of euholognthan and systellognathan egg coverings and the ground plan of the egg capsule in Plecoptera was discussed.

Feeding habits, fine structure and microhabitat preference of Euthyplocia hecuba (Hagen, 1861) (Ephemeroptera: Euthyplociidae) nymphs from Honduras.

The Euthyplociidae are a tropical and subtropical Ephemeropteran group. The aim of this study was to augment knowledge on some aspects of the biology and ecology of Euthyplocia hecuba (Hagen, 1861) nymphs. Mayflies were collected in the Rio El Padre, located on the Caribbean slope of Honduras. Diet, microhabitat preference and some fine morphological aspects of the nymphs were examined. E. hecuba nymphs are very specialised organisms that occupy a specific ecological niche in the lotic/benthic community. Immature stages show an evident preference for life in soft and fine substrata. They are detritivorous burrowers that ingest large amounts of fine particles deposited by river flow in sedimentation areas. They show peculiar morphological adaptations for life in this particular substratum, such as mouthparts modified for digging and collection of fine organic sediments, digging legs with shovel-like tibiae and massive femora, and filamentous gills.

A characterization of the egg capsules of Anacroneuria starki and A. talamanca (Plecoptera: Perlidae), with a suggestion about the distribution of stoneflies in the Tropics.

In this study, the structure of egg capsules of two species of Neotropical Perlidae: Anacroneuria starki Fenoglio and Morisi (2001 a) and A. talamanca Stark (1998), were examined. Eggs were studied using a scanning electron microscope. A morphological characterization of these eggshells is presented: layers, attachment structures and other anatomical features are described. The egg capsules of the two species differ in some aspects, but both are characterized by thin-layered egg coverings (vitelline envelope, chorion and extrachorion). On the basis of these observations, the importance of eggshell structure for the biogeographical distribution of Plecoptera in the tropics is discussed. A key role for egg capsules in the adaptation process of Plecoptera to aquatic environments of the Neotropics is hypothesized.

Structure of ovaries and formation of egg envelopes in the stonefly, Leuctra autumnalis Aubert, 1948 (Plecoptera: Leuctridae). Ultrastructural studies.

The investigation of ovaries and the formation of egg envelopes of the stonefly Leuctra autumnalis was carried out with light and transmission electron microscopes. The ovary of the studied species is paired and consists of several dozen panoistic ovarioles opening individually to the oviduct. The process of egg capsule formation already begins in previtellogenesis. At this time the follicular cells secrete precursors of the vitelline envelope. Analysis of the presented data suggests that the oocyte itself also takes part in the formation of the vitelline envelope during late vitellogenesis. Simultaneously, the follicular cells produce precursors of further layers of the egg capsule, i.e. two-layered chorion and extrachorion, consisting of two gelatinous layers and a flocculent one. The completely developed capsule contains channels, probably micropylar ones.