The invasive, plague-carrying, North American spiny-cheek crayfish, Orconectes limosus, has apparently only recently reached the UK despite being first introduced into continental Europe in 1890. A number of populations have now developed over a wide geographic area in England. It is thought that these have arisen from deliberate introductions by anglers or from aquarium pets being released by the general public. O. limosus probably poses as great a threat to the indigenous white-clawed crayfish, Austropotamobius pallipes, in the UK as does the North American signal crayfish, Pacifastacus leniusculus. Like the signal crayfish, O. limosus burrows extensively. A developing lake population of O. limosus has been studied by trapping and direct observation for the first time in the UK to see whether it could be controlled before it spreads to adjacent lakes and a river. Although large numbers appear to be present they are not easily caught in traps and the CPUE over the year of trapping was low (1.28), although in certain months, i.e. September and October, it was relatively high (2.0). Trap catches were dominated by adult males. Mating and egg-laying took place in the spring. A berried female of 62 mm CL and a male of 65 mm CL were found, which were probably at least four years old. A review of the life-history of O. limosus is also undertaken as there appears to be some variation within Europe, with two periods of mating being reported for some populations. The only way to control the population would appear to be by chemical or physical (dewatering) means.

The recent finding of the signal crayfish, Pacifastacus leniusculus (Dana, 1852) in the Brugneto Lake (Trebbia River basin, Liguria, NW Italy) raises new management problems. In this paper, the results of trapping carried out between November 2005 and October 2006, the population structure and the diseases of P. leniusculus inhabiting Brugneto Lake are analysed. The total sex ratio observed was 1:1.03 (males/females) and it did not differ significantly from the theoretical 1:1 value, whereas the sex ratio recorded during winter differed significantly from the theoretical value. The CPUE (Catch Per Unit Effort) calculated was significantly related both to mean seasonal temperature and water-level variations. Regarding diseases only the presence of chitinoclastic bacteria on exoskeleton were found. Branchiobdellidae (Annelida, Clitellata) were not observed either on the exoskeleton or in the branchialchambers, neither were ectocommensals, nor melanisation caused by bacterial infections on gill filaments. Fortunately, melanised spots on the legs usually caused by an infection of Aphanomyces astaci Schikora were not found.

Among ca. 750 species of Crustacea recorded from Poland, 18 representatives of 5 orders of macrocrustaceans have been identified as alien species that have invaded or have been introduced to Polish waters. Out of 44 freshwater, brackishwater and semiterrestrial species of Amphipoda occurring in Poland (not counting several stygobiotic species), 8 species from three families may be included in this group. They are Corophiidae: Chelicorophium curvispinum (=Corophium curvispinum), Gammaridae: Gammarus roeselii, G. tigrinus, Chaetogammarus ischnus (=Echinogammarus ischnus), Pontogammaridae: Dikerogammarus haemobaphes, D. villosus, Pontogammarus robustoides and Obesogammarus crassus. It is noticeable that most of them (C. curvispinum, C. ischnus, D. haemobaphes, D. villosus, P. robustoides, O. crassus) are of Ponto-Caspian origin, one species was introduced from North America (G. tigrinus), and one from south-eastern Europe (G. roeselii). All the species listed above have spread widely in Poland, in large rivers and artifical reservoirs (Chelicorophium curvispinum, Dikerogammarus villosus, D. haemobaphes, Pontogammarus robustoides, Gammarus tigrinus) or in medium sized rivers (Gammarus roeselii), in brackish coastal waters (Obesogammarus crassus) or both in fresh and brackish waters (Gammarus tigrinus, Pontogammarus robustoides). In most places they successfully outnumber or even completely replace native amphipod species. This paper presents data on biogeography, history, biology and ecology of alien species, as well as the consequences of their invasion in Poland with an extended bibliography and references to other European countries.

During a survey of the Belarusian part of the Dnieper River conducted on 19-22 July 2006, we revealed five invasive Ponto-Caspian amphipod species in its benthos community: Chaetogammarus ischnus, Chelicorophium curvispinum, Dikerogammarus haemobaphes, Dikerogammarus villosus and Pontogammarus robustoides. All of them except C. curvispinum are reported in Belarus for the first time. The number of alien amphipod species and their abundance were found to decrease gradually in the upper sections of the river.

We summarize and analyze all known records of the freshwater snail, Ferrissia fragilis (Tryon, 1863) in the Czech Republic. In 1942 this species was found in the Czech Republic for the first time and a total of 155 species records were obtained by the end of 2005. Based on distribution data, we observed the gradual expansion of this gastropod not only in the Elbe Lowland, where its occurrence is concentrated, but also in other regions of the Czech Republic particularly between 2001 and 2005. Information on habitat, altitude and co-occurrence with other molluscs are presented.

In the 2002 North American freshwater limpet Ferrissia fragilis (Tryon, 1863) was recorded for the first time in the continental waters of Black Sea Region. This is considered to be a continuation of invasion in the Black Sea Region as this species was previously introduced into Crimean Peninsula reservoirs in the early 20th century. A juvenile form of F. fragilis found in Central Crimea was previously described as the freshwater limpet Ancylus lacustris brevis (Puzanov 1925). According to the rules and recommendations (8B and 8.3) of the International Code of Zoological Nomenclature we point that this information can not be used as nomenclatural act (recommendation of ICZN about providing of first publication with nomenclature act as printing on paper). Since 2002, F. fragilis has been sampled in the freshwaters of the Dniestr Delta. It was observed that this invader could sustain the extreme conditions of an unusually cold winter (2005-2006).

Reciprocal crosses between non-native goldfish Carassius auratus and native crucian carp Carassius carassius were produced. The F1 hybrids were viable and vigorous, but attempts to produce F2 progenies were not successful, nor were attempts to produce back crosses. The implications of hybridization, with regard to perceived decline in crucian carp numbers, are considered for water bodies in which these species are now sympatric.

Twenty alien species were targeted in a rapid assessment of all Irish coasts during 2005 to 2006 at twenty-nine floating pontoon sites consisting of marinas, jetties or fish-farms. Twelve species were found and the survey provided twenty-five new locality records. Four species had not been recorded previously in Ireland. Three of these were tunicates Corella eumyota, Botrylloides violaceus and a cryptogenic Didemnum sp. The fourth species was not targeted, the amphipod Monocorophium insidiosum. The majority of the new locality records (67%) were from the Irish Sea coast. Some of the targeted species were removed from leisure craft hulls: Balanus improvisus, C. eumyota, Corophium mutica, Didemnum sp. and Styela clava.

The Lessepsian migrant fish Lagocephalus sceleratus was recorded for the first time in July and in December 2005 from the Cretan Sea (Aegean, Greece). The species identity was confirmed by both morphometric and genetic analyses. These records indicate that the species has established populations around the continental shelf of Crete.

The green alga Codium fragile subsp. tomentosoides is one of the most common alien macroalgae in the Mediterranean, with a wide distribution in both the western and eastern basin. Populations of this taxon are present in Greece at least since the last decade of the 20th century, and today it can be found in several locations of the central and north Aegean Sea. Its spread seems to be still in progress along Greek coasts, presenting some sporadic blooms. However, no invasive behavior was observed at any studied site until today.

Theora lubrica is reported for the first time from Haifa Bay, Israel, in 2006. This Asian semelid bivalve is one of the most invasive ship-transported mollusc species to enter the Mediterranean Sea. It was first recorded in 2001 in Livorno Harbour, Italy, and has since established there a viable population. Its occurrence in ports or port-proximate environments lends credence to shipping serving as its vector.

A total of 236 specimens of the Gammaropsis togoensis (Schellenberg, 1925) were collected in Iskenderun Bay, SE Turkey during 2005-2006. Already known from the Mediterranean coast of Israel, this is the first record of this alien amphipod from Turkey.