Remains of the protozoan sticholonche zanclea in the faecal pellets of Paracalanus quasimodo, Parvocalanus crassirostris, Temora stylifera and Temora turbinata (copepoda, calanoida) in Brazilian coastal waters

Abstract

Studies of copepod feeding have identified these organisms as key species in marine ecosystems, because they have a pivotal position in food webs: they control primary production through grazing, and are also a crucial link between the microbial food web and higher trophic levels, especially because they are able to predate on protozoa (STOECKER; CAPUZZO, 1990). The ingestion of protozoans has attracted particular attention, not only because it extends our understanding of the manifold energy pathways that structure aquatic food webs, but also because it involves an important behavioral aspect, i.e., what strategies are used to locate and capture preferred prey (AZEMAR et al., 2007). Copepods of the genera Paracalanus and Temora are believed to devote most of their time to filter feeding (VAN DUREN; VIDELER, 1995). The feeding habits of the copepods Paracalanus quasimodo , Temora stylifera and T. turbinata have shown that these species are omnivorous, but primarily opportunistic herbivores and that carnivory is infrequent (TURNER, 1984a, 1984b). Paracalanus quasimodo , Parvocalanus crassirostris , Temora stylifera and T. turbinata are abundant in Brazilian coastal waters, and are assumed to play a fundamental role in the control of primary production. Scanning electron microscopy analysis of the faecal pellets of these copepods was performed to assess the main food item ingested during the occurrence of different water masses in the Sao Sebastiao Channel (SSC), a coastal ecosystem located on the northeast coast of Sao Paulo State. Sampling was carried out every three months in the SSC, from January 1996 to July 1997 and also in July 1998 and January 1999, at two sampling points (map available in Eskinazi-Sant’Anna; Bjornberg, 2006). Surface (0.5 m) water samples (250 ml) for phytoplankton and protozooplankton analyses were taken with a Van Dorn bottle (5 L) and preserved in Lugol’s solution. Phytoplankton was enumerated using the inverted microscope method and carbon content determined using the volume:carbon conversions. Mesozooplankton was collected during 2-min surface tows with a 150-mm mesh net. Adult females of the copepods Parvocalanus crassirostris , Paracalanus quasimodo , Temora stylifera and Temora turbinata were sorted under a WILD M8 stereomicroscope, isolated within 20 min of collection, and transferred to Petri dishes containing collected surface sea water, and then left for 30 to 120 min to produce faecal pellets. The expelled faecal pellets (38 from P. crassirostris , 78 from P. quasimodo , 37 from T. stylifera and 21 from T. turbinata ) were individually removed by pipette and placed in petri dishes containing a mixture of filtered sea water (Nuclepore cellulose acetate membrane filters 20 mm) and 10 mm screened surface sea water. The pellets were then left for 24 h at 24