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On the Distribution of the Crustacean Dorsal Organ
Author(s) -
Martin Joel W.,
Laverack Michael S.
Publication year - 1992
Publication title -
acta zoologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.414
H-Index - 37
eISSN - 1463-6395
pISSN - 0001-7272
DOI - 10.1111/j.1463-6395.1992.tb01108.x
Subject(s) - malacostraca , crustacean , biology , dorsum , living fossil , decapoda , anatomy , zoology , branchiopoda , taxon , ecdysis , evolutionary biology , larva , ecology , cladocera , instar
An oval, dorsal organ, variously bearing four minute pits around a central pore and/or encircled by a cuticular border, has been reported for the cephalic region of various groups of living and fossil crustaceans. Although varying somewhat in location and in size, the organ appears basically uniform in organization in at least two of the major crustacean taxa: Branchiopoda (especially Laevicaudata) and Malacostraca (Decapoda and Syncarida). Little is known about its ultrastructure and function in various groups, and it is likely that the term ‘dorsal organ’ also has been applied to several nonhomologous structures. In particular, the embryonic dorsal organ, reviewed recently by Fioroni (Fioroni, P. 1980.— Zoologische Jahrbücher (Anatomie) 104: 425–465) and apparently functioning in nutrition and ecdysis, is not the topic of this paper; that organ is similar in name and location only and appears in embryonic uniramians, chelicerates, and crustaceans. The function of the dorsal organ in branchiopods is in ion regulation, possibly a secondary modification of the original function in marine crustaceans, which is unknown. In larval decapods, the organ probably functions as a chemo‐ or mechano‐receptor. We review the known occurrence of the crustacean dorsal organ, describe the similarities and differences in structure in various taxa, and review the competing hypotheses concerning its function. Phylogenetic implications are discussed.