Trophic relationships between macroinvertebrates and fish in a pampean lowland stream (Argentina)

Abstract

ABSTRACT. The diet and trophic relationships between the macroinvertebrates Phyllogomphoides joaquini Rodrigues Capítulo, 1992 and Coenagrionidae (Odonata), Chironomidae (Diptera), Diplodon delodontus (Lamarck, 1919) (Bivalvia: Hyriidae), and Pomacea canaliculata (Lamarck, 1822) (Gastropoda: Ampulariidae) and the fishes Pimelodella laticeps Eigenmann, 1917 (Heptapteridae) and Bryconamericus iheringii (Boulenger, 1887) (Characidae) in a temperate lowland lotic system in Argentina were assessed on the basis of gut contents and stable-isotope analyses. The feeding strategies were analyzed by the Amundsen method. Relative food items contribution for the taxa studied indicated a generalist-type trophic strategy. In macroinvertebrates, in general, the values of stable isotope confirmed the result of the analysis of gut contents. With the fish, stable-isotope analysis demonstrated that both species are predators, although B. iheringii exhibited a more omnivorous behaviour. These feeding studies allowed us to determine the trophic relationships among taxa studied. Detritus and diatoms were a principal source of food for all the macroinvertebrates studied. In La Choza stream the particulate organic matter is a major no limited food resource, has a significant influence upon the community.KEYWORDS. Diet, stable isotope, temperate plain streams. RESUMEN.Relaciones tróficas entre los macroinvertebrados y peces en un arroyo de la llanura pampeana (Argentina). Se evaluó la dieta y las relaciones tróficas entre los macroinvertebrados Phyllogomphoides joaquini Rodrigues Capítulo, 1992 y Coenagrionidae (Odonata), Chironomidae (Diptera), Diplodon delodontus (Lamarck, 1919) (Bivalvia: Hyriidae), Pomacea canaliculata (Lamarck, 1822) (Gastropoda: Ampulariidae) y los peces Pimelodella laticeps Eigenmann, 1917 (Heptapteridae) y Bryconamericus iheringii (Boulenger, 1887) (Characidae) en un ecosistema lótico pampásico, sobre la base del contenido estomacal y el análisis de isótopos estables. La estrategia alimentaria fue analizada mediante el método de Amundsen. La contribución relativa de cada categoría alimenticia para los taxa estudiados indicó que la estrategia predominante fue de tipo generalista. En general, en los macroinvertebrados, los valores de los isótopos estables confirmaron los resultados obtenidos por el análisis del contenido estomacal. En los peces, los isótopos estables demostraron que ambas especies son depredadores, aunque B. iheringii tiene un comportamiento más omnívoro. Además, el estudio de la alimentación, nos permitió establecer las conexiones tróficas entre los taxa estudiados. La principal fuente de alimento para los macroinvertebrados estudiados fueron el detritus y las diatomeas. En el arroyo La Choza la materia orgánica particulada es una fuente de recursos ilimitada con influencia significativa en toda la comunidad. PALABRAS-CLAVE.Dieta, isótopos estables, arroyo templado de llanura.

Feeding ecology of the siluriform Pimelodella laticeps Eigenmann, 1917 in a Pampean stream from Argentina

“…species, Acanthocyclops robustus lives mainly in the limnetic zones of large ponds and lakes (Dussart & Fernando 1990); Ectocyclops phaleratus is an uncommon benthic species, inhabiting mainly the littoral zone and only occasionally the water column (Dussart, 1969;Reid, 1985); Macrocyclops albidus lives among macrophytes, reaching its maximum development during summer (Pennak 1966); and Tropocyclops prasinus is a common species within the periphytic and benthic communities (Dussart, 1969), in warm waters, tolerating brackish water, and rarely behaving as planktonic (Margalef, 1983). Chironomid larvae and mayfly nymphs, which taxa are common in lotic and lentic Neotropical environments where the food availability is ample (Marchese, 1984;Kaisin, 1989;López van Oosterom et al, 2013), were found in the diet of P. laticeps at high frequencies during spring.…”

“…Almirón et al (2000) and López van Oosterom et al (2013) remarked that P. laticeps is a permanent species in the El Pescado Stream because of the fish ecologic plasticity facing the marked instability of habitat. Colautti et al (2009) noted that the species is also permanent in the La Choza Stream; whereas Paracampo (2012) recorded the catfish as a semipermanent species in El Pescado Stream.…”

“…In relation to water quality, an investigation on the fish assemblage from the River Suquía concluded that the genus Pimelodella lives only at sites with good water quality (Hued & Bistoni, 2007). After the first studies on diet of P. laticeps in pampean environments (Destefanis & Freyre, 1972;Escalante, 1984), the interest in characterizing the eating habits of the gray catfish increased recently (Grosman et al, 2002;Freyre et al, 2003;Diovisalvi et al, 2010;Fernández et al, 2012;López van Oosterom et al, 2013).…”

Dieta de Pomacea canaliculata (Gastropoda: Ampullariidae) en su hábitat natural basada en análisis de contenidos digestivos e isótopos estables

“…Mineral materials were also recorded in the stomach contents of P. canaliculata, but it is unknown whether they were part of the grit present in the gizzard that is used for triturating food (Andrews, 1965), or they were incorporated by scraping during the ingestion, taking into account that the stream studied presents a high content of fine sediment in the stream bottom (Ocon et al, 2013;López-van Oosterom et al, 2013).…”

Changes in the epipelic diatom assemblage in nutrient rich streams due to the variations of simultaneous stressors

“…The streambed of the Pampean streams is composed of fine sediments (clay and silt) that are colonized by an epipelic biofilm in which diatoms are the dominant group, A c c e p t e d M a n u s c r i p t constituting the basal trophic levels for extensive food webs Ocón et al, 2013). These streams show a relatively high concentration of nutrients when they are compared with other lotic systems of the world (Bauer et al, 2002, Giorgi et al, 2005, and can be classified as eutrophic when phosphorus is considered, or as mesotrophic when nitrogen is taken into account (Feijó & Lombardo, 2007).…”