Wolffia columbiana is a member of the family Lemnaceae and native to the Americas. In 2013, the first two occurrences of Wolffia columbiana in Europe were found in Germany and the Netherlands. Differentiation between W. columbiana and the rare native W. arrhiza is difficult and a scanning electron microscope (SEM) was used to confirm plant identification. A brief description of both populations of W. columbiana and some identifying characteristics are given. Due to their small size, Wolffia species are easily overlooked in the field and/or misidentified, and thus it seems likely, that even more unknown occurrences of alien Wolffia species might occur in Europe. The remaining known occurrences of putative W. arrhiza should be inspected to check their identity. We hypothesize, that alien W. columbiana might be sometimes overlooked or misidentified as the native W. arrhiza, and thus it may have a more widespread distribution within Europe than thought.

In 2010, Didemnum perlucidum F. Monniot, 1983, a potentially invasive colonial ascidian, was found for the first time in Western Australia (WA). During routine introduced marine pest monitoring along the WA coast in 2011–2012, the Department of Fisheries confirmed additional disjunct populations in a span of ~ 2,800 km along the coast. Colonies of the ascidian were apparently flourishing in water temperatures from tropical through to temperate. Colour was not a reliable detection method for this colonial ascidian. Colonies in winter showed the expected senescence, becoming smaller, friable and often partially detached from the substrate. While winter monitoring would reduce likelihood of detection, it may present the best opportunity for eradication. Due to the widespread distribution, eradication of D. perlucidum is now unlikely. However, implementing local control measures to protect high value areas, such as marine parks or protected areas, from incursions remains feasible. A robust monitoring program is vital to detecting D. perlucidum early in its invasion history, and that would provide the best opportunity for local eradication effort.

Research and monitoring efforts led to the discovery of four new non-indigenous tunicates and one new non-indigenous anemone in Nova Scotia in 2012 and 2013. In this report, we summarize and interpret the circumstances leading up to and actions taken following the first Nova Scotian records of the high impact invasive tunicate Didemnum vexillum Kott, 2002 as well as the tunicates Styela clava Herdman, 1881, Ascidiella aspersa (Müller, 1776), and Diplosoma listerianum (Milne-Edwards, 1841) and the anemone Diadumene lineata (Verrill, 1869). While dockside research and monitoring were responsible for detections of four species, the possibility that Didemnum vexillum was present was first reported by a member of the public, through Fisheries and Oceans Canada’s Aquatic Invasive Species Monitoring program.

During a field survey to monitor marine non-indigenous species in several marinas of the Archipelago of Madeira (Portugal), the invasive sabellid polychaete Branchiomma bairdi McIntosh, 1885 was detected for the first time on Madeira Island, reaching densities of 238–516 ind.m-2. B. bairdi was originally described from the western Atlantic (from Bermuda to Caribbean Sea) but the origin of this species is still unknown. This species has been recorded as an invasive species for the Pacific coast of Panama, Gulf of California, Mediterranean Sea, Canary Islands, and Australia. Hull fouling is the most likely vector for the introduction of the species.

The mytilid Semimytilus algosus (Gould, 1850) was collected from a fishing vessel after an in-water hull cleaning operation at Nuevo Gulf, north Patagonia, Argentina. This species is native to the Pacific coast of South America and had not been detected on the Atlantic coast of this continent. Histological slides from male and female portions of gonads of a subsample of specimens showed spawning activity. The gonad stages observed were: developing stage, ready to spawn, spawning, or had already spawned, suggesting the possibility of establishment of a breeding population in the area. The water temperatures, its seasonal range, and the habitats occupied by S. algosus in its native area are very similar to those present in Nuevo Gulf. The plasticity of this species, and its rapid invasion in other regions of the world, suggest that it could become a new invasive species in the Southwestern Atlantic in the near future. Targeted monitoring of the rocky shores of Nuevo Gulf is recommended to determine whether this non-native species is at an early stage of becoming established.

Based on its native distribution and temperature constraints, the invasive zebra mussel (Dreissena polymorpha) was not expected to colonize southern portions of the U.S., but it has now spread from the Laurentian Great Lakes to the Gulf of Mexico. Temperature is critical in zebra mussel reproduction, yet no studies have compared gametogenesis in the cooler north vs. the warmer south. We studied zebra mussel seasonal gametogenesis in Marion Reservoir, Kansas, histologically, examining monthly gonad development and categorizing mussels into one of five stages: resting, early development, late development, mature, or reabsorbing. We also histologically examined multiple size classes to determine size at maturity, and measured juveniles on artificial substrates in the reservoir to determine time to maturity. Adults were mature March–August (at 7.8–34.6°C), compared to mid-June–September (at 18–24°C) in the Great Lakes. Sixty percent of zebra mussels were mature at 5 mm; 100% were mature at 7 mm, compared to 7.5–10 mm in the northern U.S. and 5–12 mm in Europe. Zebra mussels reached maturity within 4 weeks compared to 5 weeks in the Great Lakes and Europe. We conclude that zebra mussels in Kansas matured faster, at a smaller size, and that there could be multiple generations within one year, possibly contributing to greater spread across the region.

In Europe and North America, human-made canals and reservoirs have contributed to the spread of non-native species. The mysid shrimp Hemimysis anomala G.O. Sars, 1907, which is native to the Ponto-Caspian region of Eurasia, expanded its range through intentional stocking in reservoirs and movement through shipping canals within Europe. The species later invaded the Laurentian Great Lakes, most likely through ballast transport in the early 2000s. Our survey of the New York State canal system (USA) found the species at 10 sites, spanning over 80 km of canal, which confirms the species continues to colonize human-made canal systems and that canals may catalyze its spread. We report two primary geographic areas where Hemimysis is present in the New York State canal system—in the Erie Canal east of Oneida Lake and in the Cayuga-Seneca Canal in the Finger Lakes region. Body length was significantly smaller in the western assemblage (Cayuga-Seneca Canal) compared to the assemblage east of Oneida Lake, but within each geographic area there were no significant differences in the proportion of juveniles relative to adults by longitude or the maximum density by longitude. Future studies should examine the role of surface-water flow and recreational boating traffic in the spread of Hemimysis as well as to what extent canal ecosystems are impacted by the establishment of this omnivorous crustacean.

The first record of adult Oriental shrimps Palaemon macrodactylus Rathbun, 1902 in the Venice Lagoon (north Adriatic Sea) is presented based on six specimens collected in a shallow water habitat during May 2012. The record is discussed in the context of the widespread distribution of the species, taking into account the possible ways of introduction and the possible consequences of the presence of P. macrodactylus in the Venice Lagoon.

Carassius gibelio (Prussian carp) is considered native from central Europe to Siberia and invasive in Asia, Europe, and the Middle East. To-date, there have been no published occurrences of C. gibelio in open waters of North America. Although there are reports from the late 1800’s that C. gibelio was imported into the USA, some doubt exists regarding the identity of those fish and it is unknown whether any were released into the wild. Here we report the first confirmed records of C. gibelio in the wild in North America and estimate its current distribution by compiling records from private and public sources. Morphology and DNA sequences were used to verify identification. Initial specimens of C. gibelio were found in a shallow lake in 2006 in Alberta, Canada. Routine provincial government and private fish surveys from 2008–2014 further identified C. gibelio throughout natural streams and manmade drainage ditches. These surveys document that C. gibelio is now widely distributed throughout southern Alberta. Further spread is likely due to connectivity of the waterways and the life-history attributes of this fish.

Asian carps (bighead and silver carp) were collected with boat electrofishing over four years in three South Dakota tributaries to the Missouri River at the beginning of their invasion into this region. This paper documents their annual movement upstream into these tributaries and identifies differences in distribution by age-0, juvenile, and adults. By the end of this study in 2012, Asian carps dispersion was slowed or halted in these tributaries due to artificial and natural barriers. These records represent the northern most records of Asian carps in North America (46.931042, -98.708975).

Human-mediated translocation of species is widely considered to be a serious problem for the conservation of biodiversity. Documentation of new records is important to understand the causes of extralimital species introductions because of their potential to displace native species and interfere with ecosystem functions. In Brazil, concern about documenting the presence of non-native fishes has predominantly focused on species from other continents; a relatively minor effort has been devoted to the extralimital spread of species from other basins inside the country. Here we summarize several records of a popular sportfish, the dourado, Salminus brasiliensis (Characidae) outside its natural range in Brazil, and discuss the potential causes and consequences of its introduction. More empirical research is needed to quantify new extralimital spread records of this species resulting from sport fishing. Confirmation of anecdotal reports is important to provide managers and stakeholders with reliable information. We focus the discussion on this species and other apex predators frequently introduced for sport fishing purposes.

Freshwater fish from the Guwahati in River Brahmaputra, Assam, India were screened for infection with Monogenea. The recovered parasites were diagnosed by PCR and sequencing the 18S and 28S rDNA subunit regions. Comparison of the obtained nucleotide sequences with sequences in GenBank identified the specimens as Dactylogyrus extensus Mueller and Van Cleave, 1932 and D. lamellatus Achmerow, 1952, recovered from Cyprinus carpio and Ctenopharyngodon idella (Cypriniformes: Cyprinidae) respectively. The obtained sequences differed by only 2-3 nucleotides from the sequences deposited in GenBank. The presence of D. extensus and D. lamellatus in India can result from the introductions of their respective host carrying their parasites with them.

Ants are among the world’s most destructive invaders, and Pacific Islands are particularly susceptible to invasion by non-native ant species. A species from the taxonomically problematic Pheidole flavens-complex is reported here for the first time from the southwestern Pacific. Specimens of the species reported here were collected November 2011 from an established colony on Espiritu Santo, Vanuatu, during a survey of the island’s ant fauna. Morphological and genetic analyses revealed these Vanuatu specimens belong to the Neotropical P. flavens group. The DNA sequence data most closely matched those of two specimens previously determined as P. moerens Wheeler and P. flavens Roger. A closely related taxon currently being treated as P. moerens Wheeler was reported from Hawaii in 2005. Preliminary morphological analysis suggests that the Vanuatu population reported here represents a different species than the Hawaii P. moerens. However, a valid species name cannot be confidently applied to either the Hawaii population or the Vanuatu population until a comprehensive taxonomic revision of the flavens-complex is completed. Species of the Pheidole flavens-complex are occasionally considered pest ants, but have not been documented as causing significant harm to native species, food security or public health. However, the recent spread of species in this complex across the southeastern United States, recent introductions to California and Hawaii, and the recent discovery in Vanuatu suggests their potential for human-mediated dispersal and establishment. We hope that raising awareness of this new incursion will improve the chances of early detection and eradication before the species spreads further into the Pacific Island region. We provide specimen photographs of the major and minor caste and a brief diagnosis that can be used to separate this species from other Pheidole species introduced in the Pacific island region, including Pheidole megacephala (Fabricius) and the morphologically similar Pheidole parva.

Invasions of the tropical house gecko (Hemidactylus mabouia Moreau de Jonnes, 1818) in the tropical Americas are well documented. While this gecko has been reported as well established and expanding its range in Florida, here we document the first record in the United States outside of this state. We detected a small reproducing population in Cameron County, Brownsville, Texas. We expect a rapid colonization of buildings by this species in southern Texas. We consider that this potential invasion poses novel obstacles to the continued presence of the earlier invasive Mediterranean gecko (Hemidactylus turcicus Linnaeus, 1758) across Texas.