Investigation of the intestinal spherocrystals of different Cephalobaenida (Pentastomida)

Abstract

The midgut cells of cephalobaenid pentastomids contain spherocrystals varying in size and appearance between the genera. Iron was detected in the vicinity of the crystals in all three genera, being considerably fainter in Reighardia sternae than in the other species. Ultrastructurally a distinct lamination of the spherocrystals was evident, being faint in R. sternae but clearly expressed in Raillietiella hemidactyli and Cephalobaena tetrapoda. According to the species, their diameter ranged from 1.3 to 6.25 microns. The size and number of the crystals were highest in R. hemidactyli and lowest in R. sternae. The inclusions were formed in the endoplasmic reticulum and migrated toward the cellular apex, accumulating there and being expelled into the midgut lumen. As determined by energy-dispersive X-ray analysis, calcium turned out to be the main component of the crystals. Furthermore, small amounts of chlorine and iron could be traced in the crystals. The relevance of the crystals is regarded as a kind of storage excretion such as that present in many other arthropods.

Investigation of different ontogenetic stages of Raillietiella sp. (Pentastomida: Cephalobaenida): excretory functions of the midgut

“…Normally they contain calcium; thus, most authors consider it the most important functional element in these inclusions. Actually, calcium is detectable in the midgut cells of Sebekia wedli and R. boulengeri (Doucet 1965) and directly so in the spherocrystals of R. hemidactyli and Reighardia sternae (Thomas and BoÈ ckeler 1994). In the presently investigated Raillietiella, calcium was unequivocally detected in the infective larva only.…”

“…In the investigated raillietiellids a very small amount of iron was detectable in the crystals of adult specimens. The presence of iron, however, should not be brought into connection with a blood-sucking mode of life since, on the one hand, it may be present in nonblood-sucking species but, on the other, it is lacking in some bloodsuckers (Farina et al 1990; Thomas and BoÈ ckeler 1994).…”

“…With regard to the considerably higher peaks reached in former investigations of pentastomid spherocrystals (Thomas and BoÈ ckeler 1994), one has to take into consideration that they were reached by integral measurement of entire cellular regions, whereas in the present study the beam was focused on individual crystals. The dissolving of the spherocrystals inside the midgut epithelium, which has been postulated for the spherocrystals in Cephalobaena tetrapoda (Thomas and BoÈ ckeler 1994), had previously been described by Turbeck (1974) for lepidopterous larvae, where degradation was visible by a blurring of the layers and was ascribed to a lowering of the intracellular pH.…”

“…The dissolving of the spherocrystals inside the midgut epithelium, which has been postulated for the spherocrystals in Cephalobaena tetrapoda (Thomas and BoÈ ckeler 1994), had previously been described by Turbeck (1974) for lepidopterous larvae, where degradation was visible by a blurring of the layers and was ascribed to a lowering of the intracellular pH. Wessing and Eichelberg (1978) correspondingly stated that the spherocrystals of Drosophila are formed in an alkaline environment and dissolve in an acid milieu.…”

“…Investigation of the inclusion of these in adult members of the order Cephalobaenida (Thomas and BoÈ ckeler 1994) has revealed their role in ion regulation and metabolism. Information on their inclusion in earlier ontogenetic stages of pentastomids has been lacking until now.…”