Abstract
Carnivorous aquatic plants, genus Utricularia (Lentibulariaceae), capture small aquatic organisms, such as rotifers, copepods, and cladocerans, by means of anatomical structures named bladders. The present study aimed to determine prey size and composition in U. gibba and U inflata, which were collected from a small lake and an herbaceous wetland, respectively, located in Paria Peninsula (Sucre State, Venezuela). Water pH, conductivity, dissolved oxygen, and salinity were measured in situ at each sampling location, and water samples were collected to determine N-Kjeldahl, total-P, Na+, K+, Ca++, Mg++, and Cl-. Fifty bladders from each plant species were measured and their contents were analyzed. N-Kjeldahl and total-P values were similar in both sites, and were also similar to values reported for eutrophic ecosystems, although Na+, K+, Ca++, Mg++ concentrations and in situ water parameter values were higher in the herbaceous wetland. Bladder content showed the following zooplankton groups: rotifers, cladocerans, copepods, annelids, rhizopodeans, and insects; and the following phytoplankton divisions: Bacillariophyta, Chlorophyta, Cyanophyta, and Euglenophyta. U. inflata presented smaller and fewer bladders, but higher abundance and total algal and animal morphospecies richness than U. gibba. Prey composition similarity at the taxon level between the two carnivorous species was low.
Highlights
Most carnivorous plants live in mineralpoor and acidic environments, and absorb a portion of their nutrients from dead animals through a variety of morphological, physiological, and/or behavioral adaptations that let them attract, capture, and digest their prey (Schnell 1976, Slack 1980, Knight 1992, Ellison and Gotelli 2001)
Utricularia plants present flat bladders or utricles of varied shapes with bristles or trichomes on the rhizoids, stolons, or foliar segments (Cook 1996), which help capture a wide variety of small aquatic animals (Friday 1989)
Some authors have claimed that prey slowly asphyxiates inside the trap and bacteria decompose it later (Sculthorpe 1967), others have suggested the prey is digested with enzymes or other digestive substances (Hegner 1926, HeslopHarrison 1978). The carnivory of these plants has been known for a long time (Pietropaolo and Pietropaolo 1986), intensive research to discover the ecology of Utricularia has been undertaken only recently
Summary
Most carnivorous plants live in mineralpoor and acidic environments, and absorb a portion of their nutrients from dead animals through a variety of morphological, physiological, and/or behavioral adaptations that let them attract, capture, and digest their prey (Schnell 1976, Slack 1980, Knight 1992, Ellison and Gotelli 2001). New studies include morphological aspects of the species that conform the genus Utricularia (Rutishauser and Brugger 1992, Sattler and Rutishauser 1992, Rutishauser 1993), the time it takes to capture their prey, the cost of their carnivory, their investment on carnivory and the quantification of number, size and biomass of the bladders (Friday 1989, 1992, Knight and Frost 1991, Knight 1992, Pompêo and Bertuga 1996). It is known that the bladders catch small aquatic animals such as rotifers, copepods, ostracods, cladocerans, ciliates, gastrotriches and chrinomids (Friday 1989, Knight and Frost 1991, Pompêo and Bertuga 1996, Mette et al 2000) from which the plants absorb N and P (Friday and Quarmby 1994). Our study intended to determine the scarcely known bladder prey content in U. inflata Walter and U. gibba L., and characterize the physicochemical environment where these plants grow
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