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- Elofsson, Rolf
(författare)
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Rhabdom adaptation and its phylogenetic significance
- 1976
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Ingår i: Zoologica Scripta. - : Wiley. - 0300-3256 .- 1463-6409. ; 5, s. 97-101
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Tidskriftsartikel (refereegranskat)abstract
- Rhabdom adaptation and its phylogenetic significance. Zool. Scr. 5 (3–4): 97–101, 1976. — The rhabdoms of arthropod compound eyes are structurally differentiated into open, fused layered, and fused continuous. All are capable of perceiving polarized light. The fused layered, and under certain conditions the fused continuous, perform particularly well. — The fused layered rhabdoms occur in malacostracan crustaceans and in various insect groups. This, together with, among other things, the presence of open rhabdoms in insects and crustaceans, indicates convergent development of organs and parts of organs. — Elaborate visual organs of more than one kind occur in crustaceans, as is exemplified by the compound and nauplius eyes. This shows that more than one construction on the organ level is possible in a restricted taxo-nomical unit for the. perception of light. The different rhabdom types performing well in receiving polarized light also show parallel evolution on a level below the organ. — The result of adaptation analyses indicates the need for a restricted use of the concept of homology basic to morphological investigations and a base for phylogenetic speculations. It also envisages a fruitful approach to a peep into the workshop of evolution. — It is concluded that a fully formed compound eye in arthropod ancestors is hardly conceivable. A realistic alternative is an inherent capacity of forming a compound eye. Thus the ancestral compound eye could have ranged from nothing to a partly-developed stage. The recent eyes need not originate from one source.
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| 2. |
- Elofsson, Rolf, et al.
(författare)
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The Eltringham organ and a new thoracic gland: Ultrastructure and presumed pheromone function (Insecta. Myrmeleontidae)
- 1974
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Ingår i: Zoologica Scripta. - : Wiley. - 0300-3256 .- 1463-6409. ; 3, s. 31-40
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Tidskriftsartikel (refereegranskat)abstract
- Eltringham's organ is a club-like projection from the posterior margin of hind-wings of some myrmeleontid insects. It bears laterally directed setae, each having a specialized epidermal cell beneath, which gives off secretion into a sub-setal lumen. The lumen continues into the wall of the moat-like socket of the setae. Eltringham's organ fits into an excavation of the lateral body wall connected with the opening of a thoracic gland. The thoracic gland in these animals has not previously been described. It consists of a hollow tube, feebly developed in females. The tube wall houses two cell types: gland cells and cuticular cells. The latter form the cuticle of the general duct lumen and a specialized duct leading from each gland cell. The gland cells have a microvilli-filled cavity which collects the secretion. The thoracic gland produces a pheromone secretion whose distribution is aided by Eltringham's organ where present.
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