Distribution and Abundance of Calyco-phores (Siphonophora, Calycophorae) in the Mediterranean and Adriatic Sea

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Abstract

Abstract. The paper presents data on the distribution of calycophores in the open Mediterranean waters based on samples collected during the R/V “Atlantis II” cruise in May-June 1969, as well as the first data on the distribution and quantity of nectophores and gonophores in the coastal and open Adriatic waters. The following species were numerically important in the eastern Mediterranean: Eudoxoides spiralis, Bassia bassensis, Sulculeoaria chuni, Lensia campanella, and Diphyes dispar. In the western part of the study area, however, calycophores were found in low numbers. The presence of the immigrating Atlantic forms, Muggiaea atlantica and Lensia subtiloides, was also registered. Among 22 Adriatic calycophores, numerically important were: Muggiaea kochi, Lensia subtilis, Sphaeronectes gracilis, and S. irregularis. Other species were rarely found and mainly distributed in the Otranto Strait and the Southern Adriatic Pit.

Summary

This paper presents data on calycophores found in samples taken during the R/S “Atlantis II” cruise from Rhodos to Gibraltar in May–June 1969, the seasonal cruises along the eastern Adriatic coast in 1973/74, and those in the open Adriatic waters in 1974–1976.

In the eastern Mediterranean the species E. spiralis, B. bassensis, S. chuni, L. campanella, and D. dispar were numerically important. In contrast, calycophores were not as abundant in the western Mediterranean. However, the presence of the immigrating Atlantic forms M. atlantica and L. subtiloides was registered.

In the Adriatic Sea as many 22 species were found; the most widespread and numerically important were M. kochi, L. subtilis, S. gracilis, and S. irregularis.

The dominant species M. kochi contributed from 57 to 87% to the total number of nectophores. Other species were rarely present or of smaller quantitative importance and were mainly distributed in the Otranto Strait and the South Adriatic Pit; north of the Ancona-Losinj profile these forms were not registered at all.

A statistically significant positive correlation between the quantity of nectophores and sexual persons of gonophores was determined. Gonophores were more abundant than nectophores throughout the study period. They were especially numerous during the warmer months.

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