Beobachtungen über Vorkommen, Abundanzen und Körpergrößen von mediterranen Arten der GattungAstropecten

Abstract

Observations on occurrence, abundance and body sizes of Mediterranean species of the genus Astropecten (Asteroidea, Echinodermata). At various coastal positions of the western Mediterranean starfishes of the genus Astropecten were recorded. The largest of the six species, A. aranciacus, proved to be a generalist in occurrence; however, its abundance is exceeded by other Astropecten species at various positions. It appears that the sand quality influences the local abundance of A. aranciacus. Water depth is also influential. This is shown not only by the zonation of the species studied, but also by special frequency distributions of body sizes as related to water depth. The shallow water areas near the beach may be a refuge for juveniles of A. bispinosus. The frequency distribution of body sizes for A. jonstoni is usually bimodal. For the smaller mode, samples taken at different times yielded a growth rate of 4 mm in 37 days. EINLEITUNG Von den sechs Seestern-Arten der Gattung Astropecten, die im Mittelmeer nachgewiesen sind (ToRTONESE, 1965), kommen ftinf, n~imlich A. aranciacus, A. bispinosus, A. jonstoni, A. irregularis und A. platyacanthus an man&er Ktistenstelle auf Sand

Temperature induced disease in the starfish Astropecten jonstoni

“…In April 2006, 100 A. jonstoni uncovered by harrow and collected by SCUBA divers (see Ribi et al, 1976) from 8 m at the Costa Colostrai North (water 168C and 35 ppt) were measured and immediately transferred into individual containers at 13+18C for transportation to the University of Zurich (Switzerland). Three days after collection, the 99 surviving animals were moved into covered and aerated 3-l plastic jars containing sterile sand and artificial seawater, cooled by partial immersion in 128C fresh water.…”

“…The starfish Astropecten jonstoni lives on sandy bottoms in a depth of 1 to 10 m (Ribi et al, 1976). Except for a few hours per day when they actively wander over the sand searching for food, A. jonstoni spend most of the time buried within the sediment (Ferlin-Lubini & Ribi, 1978).…”

“…Except for a few hours per day when they actively wander over the sand searching for food, A. jonstoni spend most of the time buried within the sediment (Ferlin-Lubini & Ribi, 1978). In the 1970s starfish of the genus Astopecten were present in large numbers along two sandy coasts in the south-east of Sardinia (Italy) (Ribi et al, 1976). When investigations were resumed in 1999 fewer active individuals could be found at the study sites than in the 1970s, with direct field observations suggesting an increase in sightings of dying animals on the sand surface (Maag, Schärer, Steinmann, personal observations).…”

Daily activity pattern ofAstropecten aranciacus (Echinodermata: Asteroidea) and two related species under natural conditions

“…Observations made at various places are listed in Table 1; the locations concerned are described elsewhere (Ribi et al, 1976).…”

“…The two sea-stars species, Astropecten aranciacus and A. bispinosus, coexist at various localities along the Mediterranean coast (Ribi et al, 1976). Competition for food appears likely on the Costa Colostrai in Sardinia, Italy (Ribi et al, 1977).…”