Feeding and growth in early larval shrimp Macrobrachium amazonicum from the Pantanal, southwestern Brazil

Abstract

The palaemonid shrimp Macrobrachium amazonicum (Heller 1862) lives in coastal rivers and estuaries along the northern coasts of South America as well as in inland waters of the Amazon, Orinoco, and upper La Plata (Paraguay-Paraná) River systems. In an experimental investigation on a little known, hydrologically isolated population from the Pantanal (upper Paraguay basin), we studied ontogenetic changes in early larval feeding and growth. Similar to a previously studied population from the Amazon estuary, the first zoeal stage (Z I) hatched with conspicuous fat reserves remaining from the egg yolk. While Z I is a non-feeding stage, Z II is facultatively lecithotrophic, and Z III is planktotrophic, requiring food for further development. Compared to estuarine larvae, those from the Pantanal hatched with lesser amounts of lipid droplets, and they survived for significantly shorter periods in the absence of food (maximally 8-9 d versus 14-15 d, at 29°C). Both populations moulted in short intervals (ca. 2 d) through larval stages Z I to VI. Biomass increased exponentially, with a higher growth rate observed in the Pantanal larvae. These develop in lentic inland waters, where high productivity allows for fast growth of planktonic predators. By contrast, the early larval stages of the Amazon population show a higher endotrophic potential and are thus better adapted to conditions of food limitation occurring during riverine downstream transport through lotic waters, towards coastal marine habitats. Initial larval independence from food in the Pantanal clade is interpreted as a plesiomorphic trait persisting from coastal marine ancestors. KEY WORDS: Caridean shrimp · Larval feeding · Larval growth · Lecithotrophy · StarvationResale or republication not permitted without written consent of the publisher Aquat Biol 9: [251][252][253][254][255][256][257][258][259][260][261] 2010 guay and Paraná River basins (La Plata system), are hydrologically separated and thus genetically completely isolated from all others.The occurrence of Macrobrachium amazonicum in the La Plata system has occasionally been considered to be the result of a recent anthropogenic introduction (Bialetzki et al. 1997, citing a technical report by Torloni et al. 1993). In a recent review, Maciel & Valenti (2009) also cited Magalhães et al. (2005) in this context. However, this reference is based on a misunderstanding of a statement, where Magalhães and coauthors are actually saying (p. 1933) that M. amazonicum was probably introduced into water reservoirs and rivers of the northeastern and eastern states of Brazil (citing Ramos-Porto & Coelho 1998), while the populations in the La Plata basin are explicitly referred to as belonging to the 'native fauna ' (cf. Holthuis 1952). This is in fact strongly corroborated by much earlier records from northern Paraguay (dating back to A. Borelli's expedition in 1893-94, published by Nobili 1896) and from the Pantanal of Mato Grosso, southwestern Brazil (Moreira 1912(Moreira , 1913.Due to hydrological frag...

Amphidromy in shrimps: a life cycle between rivers and the sea

“…The greater dependence on lecithotrophy in Amazonian larvae is likely an adaptation to the very long drift times in moving river water from upstream hatching sites to coastal estuaries. Pantanal populations have evolved further away from lecithotrophy as development occurs completely in a plankton-rich more stable lentic habitat (Anger & Hayd, 2010). These authors hypothesized that the continued albeit limited dependence on lecithotrophy in the Pantanal larvae is a vestige of the more extensive lecithotrophy evolved in coastal marine ancestors invading riverine freshwater habitats.…”

“…Interestingly, in the North American M. ohione, which inhabits rivers emptying into the Gulf of Mexico and southeastern Atlantic coast of the United States, larvae show a lower dependence on lecithotrophy than any of the M. amazonicum populations from South America studied by Anger & Hayd (2010). Zoeae I are completely lecithotrophic, but all yolk reserves are used or disappear after the molt to Zoea II which, as in later stages, is completely planktotrophic (Bauer & Delahoussaye, 2008 and references therein).…”

“…In the Pantanal (upper Paraguay basin) wetland populations, planktonic larvae develop completely in the relatively stable plankton-rich freshwater wetlands. Anger & Hayd (2010) compared the dependence on larval lecithotrophy of early larval stages between a Pantanal population and one from northeastern Brazil, in which larvae drifting from upstream Amazon River populations arrive and develop in low salinity estuaries. They found that Pantanal larvae were hatched with lower amounts of embryonic yolk reserve and were less dependent on lecithotrophy than the Amazon River estuarine larvae.…”

“…Instead, the larvae utilize yolk droplets remaining from embryonic development as a nutritional resource. Such larvae must molt to Stage II (first feeding stage) or sometimes Stage III (Anger & Hayd, 2010) before their food stores are used up or they will starve to death (Rome et al, 2009 and references therein).…”

“…Macrobrachium amazonicum in South America is composed of populations ranging in distribution from coastal to far inland locations in two (northern and southern) hydrologically separate river systems across tropical South America (Anger & Hayd 2010). These populations have differences in life history and sexual dimorphism which indicates that they may consist of incipient or sibling species (Vergamini et al, 2011;Hayd & Anger, 2013).…”