Predation on the bivalve Macoma balthica by the sopod Saduria entomon: laboratory and field experiments

Abstract

Infaunal predators participate in structuring benthic comnlunities by affecting species negatively or positively. The impact of the predatory isopod Saduria entomon (L.) on the bivalve Macoma balthica (L.) was studied in parallel in the laboratory and the field. The hypotheses tested were (1) S. entomon preys on newly settled and small M. balthica and (2) S. entomon affects the recruiting macrofauna significantly. In the laboratory several experiments with 1 specific size class of M. balthica per experiment were performed. Sizes ranged from newly settled postlarvae to 3.2 mm long specimens. Analysis revealed that S. entomon preys actively on M. balthica above a certain minimum size (0.8 mm), and on all the larger sizes tested. In a d l t i o n , pilot experiments showed that 34 mm long S. entomonwere able to open and eat 17 mm long M. balthica, a prey half as large as the predator Recruitment, establishment and early succession were studied in the field. Boxes with and without enclosed S. entomon were sampled after 3 mo. The assemblages that had developed were similarly diverse and abundant in both treatments. However, M. balthica decreased significantly when S. entornon was present.

Burrowing behaviour of the Baltic clam Macoma balthica: effects of sediment type, hypoxia and predator presence

“…The algae were collected 1 d before the start of the experiment at a sandy bottom site with loose-lying, drift algae. The algal mat consisted mainly of species of brown and green algae (Pilayella littoralis, Cladophora glomerata) and was added to the aquaria at a wet weight of 130 g per aquarium (2160 g WW m -2 ), corresponding to high densities of algal mats that can be found in the field (Bonsdorff 1992, Norkko & Bonsdorff 1996b end of the experiment, the algae were removed from the sediment surface and dried for 3 d at 60°C for dry weight. The mean DW of algae in the aquaria was 19.30 ± 0.85 g, (mean ± SE), corresponding to 322 g DW m -2…”

“…Stress responses are often speciesspecific, and generally M. balthica is considered tolerant of hypoxia (Dries & Theede 1974). Drifting algal mats occur frequently in the northern Baltic Sea, varying seasonally in abundance and density (Bonsdorff 1992). Algal mats induce hypoxic conditions and have more severe effects on infauna than hypoxia alone (Norkko & Bonsdorff 1996a).…”

“…The isopod Saduria entomon was used as a predator in this study. S. entomon is known to be a predator and siphon-cropper of M. balthica (Ejdung & Bonsdorff 1992, Bonsdorff et al 1995, as well as of other infauna species (Sandberg & Bonsdorff 1990). S. entomon is tolerant of hypoxia, anoxia and hydrogen sulphide (Hagerman & Szaniawska 1990, 1992, Vismann 1991 and is abundant at mud sites together with M. balthica.…”

Predation by crustaceans on native and non-native Baltic clams

“…The predatory isopod Saduria entomon, absent in the North Sea, occurs throughout the Baltic. These predators are omnivores (Green 1957, Mattila et al 1990, Cohen et al 1995and references therein, Ejdung & Elmgren 2001 and include M. balthica in their diet (Mattila et al 1990, Ejdung & Bonsdorff 1992, van der Veer et al 1998. C. maenas and S. entomon can feed on all prey sizes (1 to 6 mm) offered in our experiments (Ejdung & Bonsdorff 1992, Hiddink et al 2002.…”

“…These predators are omnivores (Green 1957, Mattila et al 1990, Cohen et al 1995and references therein, Ejdung & Elmgren 2001 and include M. balthica in their diet (Mattila et al 1990, Ejdung & Bonsdorff 1992, van der Veer et al 1998. C. maenas and S. entomon can feed on all prey sizes (1 to 6 mm) offered in our experiments (Ejdung & Bonsdorff 1992, Hiddink et al 2002. C. crangon (15 to 25 mm long) eat M. balthica up to 1.5 mm long (Hiddink et al 2002) but information on the M. balthica size span that medium (40 to 50 mm long) and large (50 to 60 mm) C. crangon can eat is to our knowledge lacking.…”