Abstract
In this study, I investigated the reproductive biology of fish species from the family Characidae of the order Characiformes. I also investigated the relationship between reproductive biology and body weight and interpreted this relationship in a phylogenetic context. The results of the present study contribute to the understanding of the evolution of the reproductive strategies present in the species of this family. Most larger characid species and other characiforms exhibit a reproductive pattern that is generally characterized by a short seasonal reproductive period that lasts one to three months, between September and April. This is accompanied by total spawning, an extremely high fecundity, and, in many species, a reproductive migration. Many species with lower fecundity exhibit some form of parental care. Although reduction in body size may represent an adaptive advantage, it may also require evolutionary responses to new biological problems that arise. In terms of reproduction, smaller species have a tendency to reduce the number of oocytes that they produce. Many small characids have a reproductive pattern similar to that of larger characiforms. On the other hand they may also exhibit a range of modifications that possibly relate to the decrease in body size and the consequent reduction in fecundity. Examples of changes in the general reproductive pattern include the following: reduction in the size of mature oocytes; increase in fecundity; production of several batches of oocytes; an extended reproductive period or even continuous reproduction that allows individuals to reproduce more than once a year; high growth rates; rapid recruitment of juveniles; presence of more than one reproductive cohort that increases the sexually active population; and multiple independent development of insemination as a reproductive strategy. These changes are possibly associated with adaptive pressures that are related to the reduction in body size. In addition, such reproductive characteristics or novelties may reflect the phylogenetic history of a given species.
Highlights
This study evaluated some of the data available in the literature about reproduction in species of the family Characidae, order Characiformes
The available data were evaluated in relation to the body sizes of the species and were interpreted within a phylogenetic context to contribute to the understanding of the evolution of the different reproductive strategies found within the species of this family
Relationships among family members are still controversial, but a series of recent papers, starting with MALABARBA & WEITZMAN (2003), and corroborated by CALCAGNOTTO et al (2005), MIRANDE (2009, 2010) and JAVONILLO et al (2010), have demonstrated that Characidae includes a series of basal taxa and a large internal clade composed of all characid species that share the synapomorphic lack of a supraorbital bone (Figs 1, 2)
Summary
Neotropical freshwater fishes, one of the most diverse groups of vertebrates on the planet, is dominated by the orders Siluriformes and Characiformes, which represent approximately 47% and 37%, respectively, of the total number of freshwater species found in the Neotropics (REIS et al, 2003). There is a large internal clade, including all species sharing the apomorphic lack of a supraorbital and less than 40 vertebrae, that includes most of the small species of the family, with more than 82% reaching a maximum of 120 mm in length, and only about 17% exceeding this length These include the Aphyocharacinae, Aphyoditeinae, Characinae, Cheirodontinae, Heterocharacinae, Rhoadsiinae, Stethaprioninae, Stevardiinae (sensu MIRANDE, 2010), and Tetragonopterinae (sensu stricto, containing only Tetragonopterus). This framework allows us to formulate the hypothesis that there was one significant event of body size reduction (miniaturization) in the common ancestor of all species sharing the apomorphic lack of a supraorbital and less than 40 vertebrae. That in any type of environment, the smaller fish are able to occupy niches that are not available to the larger fish and that a reduced size could represent an adaptive solution for some species
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