Direct Development and Posthatching Brood Care as Key Features of the Evolution of Freshwater Decapoda and Challenges fo
Direct development and posthatching brood care are among the key evolutionary adaptations of decapod crustaceans to life in fresh water. Direct development is obligatory in aeglid anomurans, primary freshwater crabs, and freshwater crayfish. It also occur
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Direct Development and Posthatching Brood Care as Key Features of the Evolution of Freshwater Decapoda and Challenges for Conservation Günter Vogt
Abstract Direct development and posthatching brood care are among the key evolutionary adaptations of decapod crustaceans to life in fresh water. Direct development is obligatory in aeglid anomurans, primary freshwater crabs, and freshwater crayfish. It also occurs in some species of secondary freshwater crabs and freshwater shrimps. Posthatching brood care is the rule in aeglids, primary freshwater crabs, and crayfish, infrequent in secondary freshwater crabs, and rare in freshwater shrimps. Extended brood care is most intense in crayfish where it includes the attachment of hatchlings by a safety line, and specific behaviours of the mother and her offspring. Direct development and posthatching brood care are associated with reduced dispersal and reduced gene flow among populations, which may explain the high degree of endemism and speciation in freshwater decapods. Due to the reduced dispersal and recolonization abilities aeglids, primary freshwater crabs, and crayfish that live in stressed freshwater habitats may face a higher threat of extinction than do species of amphidromous shrimps and crabs that can undergo long-distance migrations.
Keywords Freshwater Decapoda Direct development Posthatching brood care Evolutionary adaptation Speciation Endemism Conservation
6.1
Introduction
The abbreviation or complete suppression of larval development and the extension of brood care after hatching are among the key adaptations of decapod crustaceans to life in fresh water. These characteristics are also seen in other taxa found in fresh waters including the species-rich gastropods and fishes (Gross and Sargent 1985; G. Vogt (&) Faculty of Biosciences, University of Heidelberg, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany e-mail: [email protected] © Springer International Publishing AG 2016 T. Kawai and N. Cumberlidge (eds.), A Global Overview of the Conservation of Freshwater Decapod Crustaceans, DOI 10.1007/978-3-319-42527-6_6
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Anger 1995; Strong et al. 2008; Vogt 2013). Freshwater decapods show the entire range of developmental strategies from extended larval cycles to direct development, but the latter is by far the most common (Anger 1995, 2001, 2013; Schubart et al. 2000; Bauer 2013; Vogt 2013). Direct development is the complete abolishment of planktonic larvae and the release of benthic juveniles or juvenile-like decapodids from the mother (Rabalais and Gore 1985; Anger 2001). This is achieved either by carrying the embryos on the maternal pleopods until they hatch as juveniles, or by the brooding of earlier hatched zoeal stages either on the maternal pleopods, or in freshwater nursery pools or burrows until the juvenile stage has been reached. This chapter starts with a detailed account of direct development and posthatching brood care in freshwater shrimps, aeglid anomurans, primary and secondary freshwater crabs, and freshw
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