Amazonian shrimps (Decapoda, Palaemonidae) of several genera from the generally nutrient-poor, acid waters of the Rio Negro basin show two different breeding patterns: in the annually inundated (Jan./Feb. to Sept./Oct.) lowland forest (= ”igapo”) they breed during a period with rising and high water levels only (Dec. to July); in the headwater streams draining the ''terra firme” (= regions not subject to annual inundations), the same species breed continuously the year round. All species from these nutrient-poor and hence, plankton-deficient, waters have abreviated life cycles with 1 - 3 benthic larval stages; this includes several Macrobrachium species. However, Macrobrachium amazonicum from the plankton-rich floodplain lakes, which are fed by the richer water of the Amazon river, maintains the marine pattern of development with numerous stages of filter-feeding, planktonic larvae. Phylogenetic convergence (several genera developing independently the same adaptive pattern) and divergence (the same genus/species exhibiting different patterns in different environments) are discussed in relation to recent, general molecular genetics. © 1992, Taylor & Francis Group, LLC. All rights reserved.
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