Spondylus spinosus
Πληροφορίες
The spiny oyster occurs on rocky bottoms at depths of 2–40 m. It can form large populations of up to 15 individuals per square metre and often can be found together with another alien bivalve, Chama pacifica.
The size at first reproduction of the spiny oyster is 30 mm shell length. In the eastern Mediterranean, gonad development began when seawater temperature was ~20°C and spawning take place at ~27°C (June-August).
This oyster resembles another Mediterranean alien species, Spondylus groschi, but the latter’s larger number of main ribs (6–16 compared with 6–7 in S. spinosus), the homogeneous shape of its spines (large and flat like a palette knife) and their colour (compared with white spines in S. spinosus) distinguish these two non-native species.
Native to the Indo-Pacific and Red Sea, the spiny oyster was first recorded in the Mediterranean in 1988 in Israel, subsequently spreading to the Turkish and Lebanese coasts; it is presently confined to the eastern Mediterranean Sea. It is presumed that it arrived via the Suez Canal and its further dissemination was assisted by ships.
The spiny oyster, either alone or together with the jewel box oyster, Chama pacifica, can form dense aggregations that produce solid reefs at some sites, completely replacing native oyster species.
Competition and reduced plankton availability caused by decreased water flow can also slow down the growth of other benthic organisms.
The economic impact of this invasive species is unknown. It is a valuable species for seashell collectors, with a small trading market. In Lebanon it is also harvested and sold for food in restaurants.
Shabtay, A., 2011. The invasive oyster Spondylus spinosus Schreibers, 1793 in the Israeli Mediterranean coast. PhD thesis, Tel Aviv University, 97pp.
