ISSN:
1432-0878
Keywords:
Fenestra dorsalis
;
Allanaspides
;
Syncarida
;
Ion transport
;
Ultrastructure
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The genus Allanaspides (Crustacea, Syncarida) is characterised by a conspicuous modification of the cephalo-thoracic tergite, the fenestra dorsalis. The ultrastructure of the fenestra dorsalis was examined in both known species of Allanaspides. The organ is separated from surrounding tissue by a clearly demarcated transition zone in which the cuticle thickens and looses its normal laminated structure. In the cells of the fenestra dorsalis, three regions may be distinguished. The apical region has an abundance of long invaginations, often packed closely together. The invaginations possess numerous microtubules plus numerous mitochondria whose membranes are closely associated with the invaginated membranes. Both microtubules and mitochondria are aligned in the same direction as the invaginations. The middle region of the cells contains many intracellular vacuoles in Allanaspides hickmani whilst in Allanaspides helonomus the same region contains extensive extracellular spaces. The basal region of the cells is marked by deep infoldings and an abundance of mitochondria. Microtubules are common and these, together with the mitochondria, are aligned along the direction of the infoldings. Adjacent cells are linked by frequent septate junctions. The fine structure of fenestra dorsalis tissue indicates an active participation in ion and/or water movement. However, in contrast to other crustacean tissues known to be involved in this function, it is postulated that the fenestra dorsalis of Allanaspides provides a two-stage transport system, in which “mitochondrial pumps” are present on both the inner and outer cell surfaces.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00307469
