Alimentary Items Research Articles

Feeding ecology of <i>Bathyraja macloviana</i> (Rajiformes, Arhynchobatidae): a polychaete-feeding skate from the South-west Atlantic

The present paper analyses the diet, feeding strategy and niche width of B. macloviana in a sector of the Argentinean Continental Shelf (ACS). Individuals (n = 147) were collected from 43 sampling stations in late summer and autumn 2001. Thirty one alimentary items in the gut contents were found, with a clear dominance of polychaetes. Crustaceans were secondary alimentary items. The polychaete Travisia kerguelensis was the main food item ingested, followed by Nepthyidae, Sabellidae and Lumbrineridae, while Gammaridae and Cirolanidae were the main items among crustaceans. The niche width and feeding strategy displayed by B. macloviana support the specialisation towards polychaetes throughout this study. Slow motile and infaunal species constitute major preys. The results suggest that this skate actively selects worms, reflecting, in some sense, the composition of the polychaete assemblage, and allowing a low dietary overlap with other sympatric skates of the ACS.

Comparative dietary analysis of two populations of Mimagoniates rheocharis (Characidae: Glandulocaudinae) from two streams of Southern Brazil

The diet of two populations of Mimagoniates rheocharis, from two freshwater streams of the rio Tramandaí, northeastern Rio Grande do Sul, Brazil, are described and compared. The specimens were collected monthly from January 1998 to March 1999, with dip nets and seine nets and preserved in 10% formalin. In laboratory, the standard length of each specimen was measured. The stomachs were removed and dissected for identification of the alimentary items. The data were analyzed using the frequency of occurrence, percent composition and index of alimentary importance methods, being the last two compared among different classes of standard length. Three methods of analysis showed the highest values for allochthonous insects, regardless the locality of collection or body size of the specimens.

Variação da alimentação natural de Serrasalmus spilopleura Kner, 1860 (Pisces, Serrasalmidae) em função do ciclo lunar e das estações do ano na lagoa de Extremoz, Rio Grande do Norte, Brasil

The present paper aims to study feeding aspects of Serrasalmus spilopleura (Kner, 1860) from Extremoz Lake (5º 42’76”S and 35º17’69”W), Rio Grande do Norte state, Brazil, in the period from July/1998 to April/1999 connecting lunar cycle to the seasons of the year. 337 specimens were collected in each phase of the moon, being used five ambush nets which varied from 2,0 to 5,0 centimeters with knots in four different points and catchings of five hours, times (17h00 - 22h00). The species showed feeding activity during the study period, independently of the season of the year and the phase of the moon, with small variations in the alimentary items. Insects appeared as principal food characterizing the species as carnivorous with tendency to insectivorous.

Ecological and reproductive aspects of Neoechinorhynchus pimelodi Brasil-Sato & Pavanelli (Eoacanthocephala, Neoechinorhynchidae) of Pimelodus maculatus Lacépède (Siluroidei, Pimelodidae) of the São Francisco River, Brazil

Ecological and reproductive aspects of Neoechinorhynchus pimelodi Brasil-Sato & Pavanelli, 1998, in Pimelodus maculatus Lacepede, 1803 collected in the Sao Francisco river during periods of drought (July 1995 and 1996) and floodings (January 1996 and 1997) of this river basin are provided. In tropical regions where the amount of rainfall alters the hydrological regimen of limnological systems water temperature has not had an important role in infections of N. pimelodi in P. maculatus. Prevalence was somewhat higher during drought periods. Intensity of infection varied slightly between collecting periods. Mature male and female acanthocephalans were present in all periods. Females were predominant. Mature females were present in higher numbers during flooding periods with a corresponding decrease in juvenile acanthocephalans. Recruitment and constant losses of N. pimelodi seem to be controlled by transmission mechanisms independently of density. Mechanisms may consist of infected prey availability (potential intermediate hosts) and changes of preferred alimentary items in the diets of juvenile and mature P. maculatus.