Between-habitats differences in burrow characteristics and trophic modes in the southwestern Atlantic burrowing crab Chasmagnathus granulata

O. IRIBARNE,; BORTOLUS, A.; BOTTO, F

MARINE ECOLOGY PROGRESS SERIES

INTER-RESEARCH

Lugar: Oldendorf/Luhe; Año: 1997 vol. 155 p. 132 - 145

0171-8630

ABSTRACT Burrow characteristics, food type, and feeding h a b ~ t sof the SW Atlantlc burrowing crab Chasmagnathus grdnulata were compared between ~ n d i v ~ d u allisv ing in mud flats and In Spartinadominated marshes. Burrows were shorter (X - 19.7 cm, SD = 5 8, n = 54) and more dynamlc (entrance displacement: X = 3 2 cm d-l, SD = 1 7, n = 21) in mud flats than In Spartlna-dominated areas (length X = 41 cm, SD = 12, n = 78, no entrance displacement). Sediment turnover rate was much higher in mud flats (X - 5 9 kg m-' d-l) than in Spartlna-dominated areas ( X = 2 4 kg m-' d.'). Burrow shape differed between areas, being straight, near-vert~catlu nnels in the vegetated area, but oblique (average angle to vertical = 60'. SD = 16", n = 110), and having a funnel-shape entrance and a much large]- diameter in mud flats Stomach contents also differed between habitats. Pleces of plants dominated contents in the vegetated area, while sediment (with polychaetes, diatoms, ostracods, and nematodes) dom~na t edin the mud flats, lndicatlng that crabs are mainly deposit feeders In the mud flats and herb~vorousin the Spart~na-dominateda reas. This pattern suggests that the heuristic model relatlng burrow arch~tecture to trophic modes prev~ouslyp roposed for fossorial thalassinidean shrimps applies to individuals of a C granulata populat~on The burrow content showed higher organic content and vegetal parts in the vegetated area than in the other area. Burrows in the mud flat showed a significantly higher abundance of nematodes and ostracods. Due to their hydrodynalnic characteristics and content, burrows in the mud flats may work as passive traps for sediment and organic matter. Given the extensive intertidal area inhabited by C granulata in SW Atlantic estuanes, and the locatlon of their burrows (between marshes and the open estuary), these burrows may work as traps for detritus, thus reduclng the export rate of organic matter from marshes.