Etudes sur l'�picuticule des insectes

The eye of Orchomene sp. cf. O. rossi , an amphipod living under the Ross Ice Shelf (Antarctica)

The structural organization of the eye of freshly caught Orchomene sp. cf. O. rossi is described and compared with that of individuals that were exposed to sunlight for 2 h, or were kept in complete darkness for 2 and 7 days. Orchomene sp. cf. O. rossi occurs under the 400 m thick Ross Ice Shelf in water of — 2 °C. Its eyes, containing 360 ommatidia, are relatively large and of orange colour. External facets are not developed, but the dioptric structures, consisting of a cornea 30 μm thick and the bipartite crystalline cones (ca. 65 μm long and 55 μm wide), are transparent and allow one to see the underlying ommatidial organization and retinula. Rhabdoms, comprising rhabdomeres of five retinula cells per omma, are voluminous (up to 50 μm in diameter and 160 μm in length) and surround the proximal ends of the crystalline cones. There are a few black screening pigment granules in the retinula cell plasma, but their number is too small to effectively shield and insulate neighbouring ommatidia from each other. Interstitial cells, containing vesicles of 0.3 μm diameter, occupy the spaces between adjacent ommatidial groups of retinula cells, but do not extend into the layer of retinula cell nuclei. Based on the anatomy, the eye of Orchomene sp. cf. O. rossi seems to be adapted to maximize photon capture at the expense of acuity.

Cytodifferentiation in the accessory glands of Tenebrio molitor II. Patterns of leucine incorporation in the tubular glands of post-ecdysial adult males

The tubular accessory gland of male mealworm beetles undergoes rapid and progressive terminal differentiation in the 8-day period after ecdysis to the adult. Total protein and RNA content are maximal at five and eight days respectively. Rates of leucine incorporation rise gradually through the first four days and then increase abruptly in the 5-to 7-day interval. SDS-polyacrylamide gel electrophoresis demonstrates a variety of proteins; two classes with high mobility (Class A and B) appear prominent in homogenates of 5- to 8-day glands. Double-label procedures show that as the glands mature, an increasing proportion of the total leucine incorporation passes into Class A and B proteins, until at eight days, Class A and B proteins account for 50% of the total for the gland. The relative incorporation into A vs. B also changes linearly over this interval. The developmental program of the tubular gland includes both a linearly biosynthetic increase in the proportion of differentiation-specific proteins and an abrupt change in the overall rates of leucine incorporation.

The fine structure of a parasitic ciliate Terebrospira during ingestion of the exoskeleton of a shrimp Palaemonetes

The ciliated protozoan, Terebrospira chattoni, invades the exoskeleton of the shrimp, Palaemonetes pugio, eating out long galleries parallel to the surface of the exoskeleton. Solubilization of the exoskeleton occurs around an area of the elaborately infolded surface membrane at the anterior of the organism. Dissolved products of the digestion of the exoskeleton are taken into the body by the formation of coated vesicles at pores in the membrane. The surface membrane that is taken in by pinocytosis is apparently recycled by the introduction into the membrane of organelles implicated in membrane recycling in other ciliates. Acid phosphatase can be demonstrated on the surface membrane as well as in the endocuticle around the organism.

Intercellular communication in a positional field. Ultrastructural correlates and tracer analysis of communication between insect epidermal cells

The junctional membrane in the epidermal cells of the larval beetle (Tenebrio molitor L.) is comprised of macular gap junctions embedded in septate junctions. Ultrastructural and morphometric analysis of the distribution of gap junctions within the segmental epidermis suggests that this junction alone could account for the high electrotonic coupling recorded for the epidermal sheet. Analysis of the lanthanum-impregnated septate junction makes it doubtful that this junction serves as a communicating channel between beetle cells. A new model for the septate junction is presented in which pleated septa, less than 30 A thick, connect adjacent plasma membranes; the septa themselves are interconnected by two interseptal platforms that are coplanar with the plasma membranes. Iontophoretic injection of organic tracers into single epidermal cells suggests that only molecules of less than MW 1000 can transfer between cells through low-resistance junctions.