A new look at an old visual system: structure and development of the compound eyes and optic ganglia of the brine shrimp artemia salina linnaeus, 1758 (branchiopoda, anostraca)

Abstract

Compared to research carried out on decapod crustaceans, the development of the visual system in representatives of the entomostracan crustaceans is poorly understood. However, the structural evolution of the arthropod visual system is an important topic in the new debate on arthropod relationships, and entomostracan crustaceans play a key role in this discussion. Hence, data on structure and ontogeny of the entomostracan visual system are likely to contribute new aspects to our understanding of arthropod phylogeny. Therefore, we explored the proliferation of neuronal stem cells (in vivo incorporation of bromodeoxyuridine) and the developmental expression of synaptic proteins (immunohistochemistry against synapsins) in the developing optic neuropils of the brine shrimp Artemia salina Linnaeus, 1758 (Crustacea, Entomostraca, Branchiopoda, Anostraca) from hatching to adulthood. The morphology of the adult visual system was examined in serial sections of plastic embedded specimens. Our results indicate that the cellular material that gives rise to the visual system (compound eyes and two optic ganglia) is contributed by the mitotic activity of neuronal stem cells that are arranged in three band-shaped proliferation zones. Synapsin-like immunoreactivity in the lamina ganglionaris and the medulla externa initiated only after the anlagen of the compound eyes had already formed, suggesting that the emergence of the two optic neuropils lags behind the proliferative action of these stem cells. Neurogenesis in A. salina is compared to similar processes in malacostracan crustaceans and possible phylogenetic implications are discussed.

Evolution of arthropod visual systems: Development of the eyes and central visual pathways in the horseshoe crabLimulus polyphemusLinnaeus, 1758 (Chelicerata, Xiphosura)

“…Thus, we applied the proliferation marker bromodeoxyuridine (BrdU; Harzsch et al, 1999;Harzsch and Walossek, 2001;Wildt and Harzsch, 2002) and immunohistochemistry with photoreceptor-specific markers that have been characterized in adult animals (opsin, visual arrestin, myosin III; Battelle et al, 1998Battelle et al, , 2001). Our analyses focused on embryonic stages shortly before hatching, trilobite larvae, and young juveniles, because the study by French (1980) indicated that this time period includes rapid morphogenetic events.…”

“…Furthermore, in recent years, aspects of eye development emerge as important characters for phylogenetic analyses and, therefore, are examined in a variety of arthropods, including Crustacea (Harzsch et al, 1999;Melzer et al, 2000;Hafner and Tokarski, 2001;Harzsch and Walossek, 2001;Wildt and Harzsch, 2002), Hexapoda (Friedrich et al, 1996;Friedrich and Benzer, 2000;Friedrich, 2003), and Myriapoda . Comparative studies on eye development in insects have also revealed new insights into the molecular developmental changes that occurred during the evolutionary transition from hemimetabolous to holometabolous insects (Friedrich, 2003).…”

Phylogenetisches Symposium Göttingen

“…5B; Utting et al 2000, Harzsch and Glötzner 2002, Loesel et al 2002, Loesel and Strausfeld 2004, Loesel 2004, the olfactory system of Mandibulata (Fig. 5C, D ; Hildebrand 1999, Schachtner et al 2005) and structure and development of the optic ganglia (Harzsch et al 1999, Harzsch and Walossek 2001, Harzsch 2002b, Wildt and Harzsch 2002, Sinakevitch et al 2003, Strausfeld 2005, Harzsch et al, 2006b). The majority of these studies have not focussed on the identification of individual cells in the brain but rather on a comparison of certain classes of cells and their cytoarchitectural features, such as the interneurons associated with the central complex (Fig.…”

“…Next to the mitotic band in crustacean eyes, a morphogenetic zone is located, the transition zone in which new proto-ommatidia are formed which are added to the side of the retina ( Fig. 8A; Harzsch et al 1999, Melzer et al 2000, Harzsch and Walossek 2001, Hafner and Tokarski 2001, Wildt and Harzsch 2002. Melzer et al (2000) reported that the sequence of precluster emergence during retinal patterning of the branchiopod crustacean Triops cancriformis corresponds well with that seen in D. melanogaster (Fig.…”

“…What is more, information on the development of the lateral eyes take a more and more important role in contributing informative character sets ( Fig. 8-10; Harzsch et al 1999, Melzer et al 2000, Hafner and Tokarski 1998, Harzsch and Walossek 2001, Wildt and Harzsch 2002, Friedrich 2003, Harzsch and Hafner 2006. …”