A daily cycle of apocrine secretion by the B cells in the hepatopancreas of terrestrial isopods

Abstract

The ultrastructure of the two cell types of the hepatopancreas of the terrestrial isopods Oniscus asellus and Porcellio scaber was examined at hourly intervals in animals habituated to a 16 h light: 8 h dark cycle. The ultrastructure of the B cells undergoes substantial changes which are repeated every 24 h. This 'B cell cycle' can be divided into two stages. During the first, 'extrusive' stage, which begins about 1 h before the onset of the light period, the contents of the B cells apical to the nuclei are voided into the lumen of the hepatopancreas. The second, 'restitutive,' stage begins about 10 h after the onset of the light cycle. The B cells swell in size by the accumulation of the new material until the next extrusive stage. The ultrastructural appearance of the S cells was similar at all stages of the daily and moult cycles; they were never observed to void any material into the lumen of the hepatopancreas. The differences between the rates of turnover of the contents of the S and B cells have important implications for understanding the dynamics of accumulation and loss of metal pollutants in terrestrial isopods.

The Influence of Zinc on the Uptake and Loss of Cadmium and Lead in the Woodlouse, Porcellio scaber (Isopoda, Oniscidea)

“…The animals can eliminate the assimilated lead to about 50%, but after 2}4 weeks of feeding on uncontaminated litter the decline ceased (see Witzel, 1998). According to the histochemical "ndings of, e.g., Hopkin and Martin (1982b) and Hames and Hopkin (1991a) were not signi"cantly in#uenced by the presence of zinc, although there were di!erences in the lead content in the di!erent experiments. But this e!ect was more likely caused by di!erences in the weight of the animals.…”

“…B cells have secretory function and void cell material in a 24-h rhythm into the lumen of the hepatopancreas, whereas S cells have only a storage function and never void any material. Thus metals that are stored in the granules of S cells remain in the body until the death of the animal (Hames and Hopkin, 1991a). Although there seems to be no point for further discussion contradictory statements have been made about the ability of P. scaber to eliminate cadmium.…”

Influence of soil pH on the toxicity of zinc oxide nanoparticles to the terrestrial isopod Porcellionides pruinosus

“…The hepatopancreas of isopods is composed of small (S) and big (B) cells, whose functions are absorption and absorption/secretion, respectively [44].…”

“…It has been shown that zinc will form granules in both B and S cells of P. scaber [44]. However, the capacity to excrete metals is speciesdependent [46].…”

Localization of metals in cells of saprophagous soil arthropods (Isopoda, Diplopoda, Collembola)

“…But Hopkin et al (1985a) have shown that the copper level in intermolt animals is too high to allow for massive copper loss during molting. Furthermore, the cells containing the copper granules (S-cells) do not undergo a daily cycle (Hames and Hopkin, 1990) and never void their contents into the lumen of the hepatopancreas (Hopkin, 1990). Consequently, the vast majority of metals stored in these copper-containing granules remains within the epithelium until the isopod dies.…”