First records of the tanaid species Zeuxo holdichi and Apseudopsis tridens (Crustacea: Peracarida) From the Venice Lagoon (Italy, Northern Adriatic Sea)

Abstract

Two new records of the tanaid species Zeuxo holdichi and Apseudopsis tridens are reported for the Venice lagoon. Soft bottom sediment samples were collected as part of a monitoring survey to evaluate the ecological status of the lagoon within the European Directive 2000/60/EC. Specimens of Z. holdichi and A. tridens were found in four and two sampling stations respectively, located in diferent parts of the lagoon. The tanaidomorph species Z. holdichi was previously reported for the Atlantic coasts of France, Spain, Portugal and for southwest England, while the apseudomorph tanaid A. tridens was described only for the Israeli coasts. Therefore, this study represents the frst record of Z. holdichi for the Mediterranean Sea and the frst observation of A. tridens in Italian waters. Despite the low intrinsic dispersal potential of these tanaid species, their native origin or their possible alien status in Italian waters is debated. The dubious native origin of Z. holdichi and the possible underestimation of both species’ presence in Italian Seas due to the lack of taxonomic specialists, attribute to these tanaids a cryptogenic nature. The ability of both species to cope with the diferent environmental parameters characterizing the lagoon may increase the probability of competition with other species that have similar ecological and trophic guilds.