The presence of non-native Asian earthworms in northeastern North America has raised concerns in the last decades following the observation of how intensely they can disturb the soil and initiate cascading effects in invaded areas. A recent study showed that the known northern distribution of these earthworms in northeastern North America reached the southern parts of the province of Ontario (Canada) as well as the northeastern states in the U.S.A. that border the province of Québec (Canada). In 2021, more specimens were found in southern Ontario and in the province of New Brunswick. Here we report the first record of a non-native Asian earthworm (Amynthas tokioensis) in the province of Québec, which confirms the progression of the invasive Asian earthworms in Canada.

Wood-boring beetles, including longhorned beetles, are significant exotic insects that disperse outside their native habitats due to global trade. Detection and accurate identification of these beetles pose challenges due to cryptic behavior of larvae and their similar external morphology. In this study, we focus on the identification of two unidentified longhorned beetle larvae found in a wooden Gymboree toy and a wooden bed frame. Both larvae died during rearing, with confirmed lifespans of at least 6 and 7 years, respectively. Molecular identification using mitochondrial COI gene successfully identified larvae as Stromatium longicorne (Newman, 1842) (Coleoptera: Cerambycidae), a species inhabiting various species of dry woods and native to Southern Asia. The detection of S. longicorne in South Korea confirmed the case of non-native longhorned beetles introduced through processed wood products. This discovery adds a new non-native longhorned beetle species to South Korea and raises concerns about potential establishment of subtropic insects through processed wood products and under warmer conditions due to global warming.

Both morphological and molecular data confirmed the presence of the Australian Dysphania cristata in the Mediterranean basin. This is the first record in this region (made in Mahdia city, Tunisia). A brief morphological description of this species is provided along with a subsequent comparison with related and similarly looking Dysphania species. The status of D. cristata in Tunisia is also discussed.

Native to Europe, Western Asia, and the Caucasus, Aethusa cynapium L. is an invasive plant that has been introduced in many parts of the world, including North America, North Africa, the Russian Far East, and Japan. As for the Republic of Korea, the species is currently found in the Yangjaecheon Stream in Gaepo-dong, Gangnam-gu, in Seoul. Morphologically, it is similar to Cicuta virosa and Conium maculatum but can be distinguished from them by its striated stems, triangular or ovate leaflets, 6–25.3 mm unequal rays, three linear-lanceolate involucels, and filiform ribs on fruits. Considering that its seeds can remain viable in the soil for 10–20 years, local and regulatory authorities should pay close attention to this potentially dangerous species. Our study provides photographs, morphological description, and a geographical distribution map of A. cynapium.

As introduced species constitute a major threat to biodiversity, it is crucial to properly monitor their spread to new regions. The present study reports new records of four species: 1) the amphipod Ampithoe valida S.I. Smith, 1873 and 2) the polychaete Polydora colonia Moore, 1907, both new records for Brittany (North-West part of France); 3) the polychaete Bispira polyomma Giangrande & Faasse, 2012, a first finding in the North-East Atlantic; and 4) the flatworm Prostheceraeus moseleyi Lang, 1884 with a confirmed northernmost record in North-East Atlantic. These species were recorded within two semi-enclosed bays: the Morbihan Gulf on the southern coast of Brittany and the Bay of Brest in the North-West part of Brittany. Both localities are already known to host numerous non-indigenous species as well as benthic macrofaunal distributional range limits. Morphological variations and inconsistencies are discussed and reported for A. valida, revealing missing characters and errors in the literature. This work adds three non-indigenous species to Brittany and two non-indigenous species to French waters, for which we discuss potential introduction vectors.

This paper reports the first recorded presence of a non-native protobranch bivalve, Yoldia limatula (American file clam), in the United Kingdom. In November 2020, it was found to be present in already high numbers (257 individuals recorded) in subtidal sediments in the estuarine zone of the Tees River, Northeast England. This record is far outside the species’ native range of North America. The species has recently also been found on the continental margin of Northwest Europe. It is likely to have been introduced into the UK via marine traffic, with larval displacement through ballast water exchange thought the most likely route of entry. The bioturbating activities of the species in its native range are discussed, which might have significant ecosystem implications if the species were to become fully established in UK waters. An identification guide to separate this species from similar species of protobranch bivalves in the UK is included.

The invasive charru mussel Mytella strigata (Hanley, 1843) was first reported by fishermen in the upper Gulf of Thailand in 2017 and was scientifically surveyed in November 2018. A survey in August 2023 demonstrated that the mussel had not spread significantly in the region in nearly five years. Populations remained dense in aquaculture ponds and the Bangpakong River estuary where it was most abundant in 2018, but M. strigata occurred at only one of 10 rocky shore sites on the open coast. Size frequency histograms for all populations of M. strigata sampled were unimodal, suggesting there was one spawning season, but settlement apparently occurred at different times at the various sites. At sites where M. strigata occurred with the Asian green mussel Perna viridis (Linnaeus, 1758), the evidence that M. strigata was outcompeting P. viridis was uncertain. Data obtained during the 2018 and 2023 surveys provide a sound basis for monitoring the status of M. strigata in the upper Gulf of Thailand in the future. There is an urgent requirement to undertake basic biological research on population parameters such as reproductive periodicity, growth rates and, in particular, the environmental and economics of the widespread invasion of this species.

Ecosystem engineering bivalves can shape aquatic ecosystems because their high filtration capacity changes water quality and their shells increase the fractal dimension of benthic ecosystems with consequent abiotic and biotic effects. The Asian date mussel Arcuatula senhousia (W. H. Benson, 1842), native to East Asia between the South China Sea and Siberia, is one such bivalve that, despite its small size, can reshape a benthic ecosystem when forming dense, continuous mats. We describe here the first detected population of this non-indigenous species in southern Portugal. The Asian date mussel was found in the middle portion of the Guadiana estuary in 2022. There, river flow has been highly regulated since the construction of the biggest European reservoir in 2002, which may have been the precursor for the establishment of numerous non-indigenous species. We also discuss if this new non-indigenous species indicates an ongoing invasion meltdown process or if it can be framed under the empty niche or niche replacement hypothesis. So far, there is only circumstantial evidence supporting the niche theory hypotheses, but the interaction of several hypotheses promoting the spread and establishment of this species is also likely. Moving forward, better-informed management and conservation efforts should rely on new empirical and experimental evidence to understand the establishment mechanisms of non-indigenous species in the Guadiana estuary.

A single adult specimen of Thalamita oculea, a portunid crab known from the Indian Ocean, was recently collected off the Israeli coast, in the southeastern Mediterranean Sea. Morphological characters, as well as molecular analyses based on the mitochondrial barcoding gene 16S ribosomal RNA, support the identification. The species is described, illustrated, and differentiated from its Mediterranean congeners. As the Israeli shelf serves as an important way station and breeding ground for invasive Erythraean biota, T. oculea may potentially spread along the Levant coastline.

Marine species are expanding polewards with rising temperatures. In the Northwest Atlantic, tropical/subtropical species native to the Caribbean have been documented as spreading into temperate regions. One such species, the green porcelain crab (Petrolisthes armatus), has been migrating up the southeastern United States coastline from Florida since the 1990s. Until 2018, the species had not been detected north of Wilmington, North Carolina (NC). Here, we document the establishment of P. armatus populations along the NC central coast. During biodiversity monitoring, we detected the first record of P. armatus in 2018 in Beaufort, NC, and subsequent records of the crab were detected at multiple locations in the region over a four-year time period (2018–2022), often at relatively high abundances. Morphological and genetic evidence confirmed the identity of P. armatus in this region and distinguished it from its less abundant native congener, P. galathinus (banded porcelain crab). While cold winter temperatures have likely limited the species’ ability to spread northwards in the past, rising winter temperatures in recent years may facilitate its continued expansion. It is vital that we continue monitoring the species’ population demographics in its expanding range, as well as determine community-level impacts in the region.

We screened the gill and somatic muscle of 152 wild-caught invasive giant tiger prawns (GTPs), Penaeus monodon Fabricius, 1798 (Penaeoidea: Penaeidae) for infection by white spot syndrome virus (WSSV), infectious hypodermal and hematopoietic necrosis virus (IHHNV), and Taura syndrome virus (TSV) using molecular methods (PCR and qPCR) and transmission electron microscopy (TEM). The sampled GTPs comprised 1 freshly-collected specimen from Mississippi Sound (Northern Gulf of Mexico) during 2020; 54 frozen specimens originally captured from the Northern Gulf of Mexico off Mississippi, Alabama, and Florida during 2014–2016; 76 frozen specimens originally captured from the Northwestern Atlantic Ocean off North Carolina, South Carolina, Georgia, and Florida during 2014–2020; and 21 museum-accessioned specimens (19 initially ethanol-preserved; 2 initially formalin-fixed) captured from the Gulf of Mexico and Northwestern Atlantic Ocean off Florida during 1988, 2011–2013, and 2016. Molecular viral detection relied upon qPCR with TaqMan chemistry for WSSV, conventional PCR for IHHNV, and rt-PCR for Taura virus. TEM was performed on WSSV qPCR+ positive GTP gill to confirm viral infection. A total of 18 GTPs were positive for WSSV by qPCR, 1 was positive for IHHNV by conventional PCR, and none were positive for Taura virus. This is the first report of a WSSV or IHHNV infection in a wild-caught GTP from the Gulf of Mexico or Northwestern Atlantic Ocean and first detection of an IHHNV infection in a wild-caught host in the Northwestern Atlantic Ocean. The phylogenetic analyses indicated that, broadly, sympatric WSSV isolates (unless identical) do not share a recent common ancestor (they are paraphyletic), suggesting that the virus has been repeatedly translocated and introduced into the Gulf of Mexico and Northwestern Atlantic Ocean and that it originated from different localities.

A first record of non-native Sebastes schlegelii (Hilgendorf, 1880) was made in Bulgarian Black Sea waters. One specimen was collected from the coastal waters (Varna breakwater) of the Bulgarian Black Sea. The identification was based on morphological characteristics and DNA barcoding. The morphological measurements covered 34 morphometric and 6 meristic features. A fragment of cytochrome oxidase subunit I (COI) gene of mitochondrial DNA was sequenced to supplement the species identification. Moreover, five specimens were caught during 2022 and 2023 by sport fishermen. These collections represent the first official report of S. schlegelii along the western Black Sea coast.

A new locality of Elodea nuttallii (Planch.) H.St.John (Hydrocharitaceae), native to North America, has been recorded for the first time in Göksu Nature Park (Bolu/Türkiye). Elodea nuttallii is a potentially invasive macrophyte and often confused with Elodea canadensis Michaux, whose existence was previously known in Türkiye. The description, distribution map, notes about the habitat of Elodea nuttallii, and the morphological differences between the two taxa are given in this article.

We report the first records for the Eurasian zooplankton species Thermocyclops crassus (Fischer, 1853) (Copepoda, Cyclopoida) from two freshwater sites in eastern Canada collected between 2020 and 2022. Thermocyclops crassus were found at high densities (between 8 × 10³ and 2 × 10⁵ adults/m³) in Lake St. Pierre on the St. Lawrence River, Québec, but at very low densities (between 0.3 and 0.7 adults/m³) in Wentzell’s Lake on the LaHave River system, Nova Scotia. We discuss possible introduction pathways for both sites as well as the need for enhanced biosurveillance and increased public education in eastern Canada.

This study reports the spread of the New Zealand mud snail Potamopyrgus antipodarum throughout freshwater ecosystems of Madeira Island, located in the NE Atlantic. Potamopyrgus antipodarum was first detected in 2017–2018 in two streams located in the north coast of the island. Since then, we have visually inspected the island's freshwater ecosystems and detected this gastropod in nine other streams. Previous evidence suggests that this species was introduced to Madeira since at least 2017, likely in the northern part. Our findings indicate that P. antipodarum is now well-established in the initial invaded locations and has since spread to the south region and upper streams of the island. Although it is difficult to conclusively determine the origin and vector of this introduction, it is plausible to assume that humans and fish may have contributed to its current distribution. Our records represent the first evidence of vast geographical distribution of P. antipodarum on Madeira Island. Madeira seems to be the first invaded oceanic island of Macaronesia and the westernmost European distribution range for this invasive species.

Palaemon sinensis is a landlocked shrimp imported to Japan from China for use as fishing bait. This species was first confirmed in the wild in Japan in 2005, mainly appearing in riverside pools and irrigation canals. The July 2018 flood in western Japan greatly altered streambeds, adjacent riparian, and aquatic zones. However, there is no information on the effects of extreme flood disturbances on populations of this species. In this study, we compared the occurrence of freshwater shrimp before and after the 2018 flood. The results showed that, in the post-flood survey in 2022, P. sinensis appeared in four out of 12 canals but not at the river sampling stations. At the river sampling stations, the amphidromous shrimp Caridina leucosticta was recorded before and after the flood. Other landlocked species, Neocaridina spp., which may show positive stereotaxis to submerged vegetation, appeared after flooding. The present study is the first follow-up survey of the exotic P. sinensis shrimp after the 2018 flood. This species showed relatively low resistance to flooding compared with other freshwater shrimp species. However, irrigation canals were found to be less susceptible to flooding disturbances than rivers as habitats for this species.

Crayfish are known to effectively invade freshwater systems worldwide. Whilst no native crayfish species exist in Israel, three exotic species have been documented in recent years, and their introduction details are hereby discussed. Three of these introduction events, one of each species, were previously reported; one was established, one failed to establish, and the third was successfully eradicated. However, more recently, invasive crayfish have been independently detected multiple times, involving a variety of natural and artificial habitats. Altogether, three invasive crayfish species currently inhabit Israeli freshwaters: Cherax quadricarinatus, Procambarus clarkii, and Procambarus virginalis. They were found in fourteen independent cases, and at least five of them represent established populations. Similar to other crayfish invasions around the globe, we speculate that the invasive populations in Israel result from the intentional release of aquarium inhabitants, as well as from aquaculture escapees. The import and trade policy of aquatic organisms in Israel requires thorough revision to prevent future invasions. Thought should also be given to the prevention of the spread of the existing invasive populations as well as to their eradication, if possible.

The brown bullhead Ameiurus nebulosus (Lesueur, 1819) is recorded for the first time in the Neman river basin in Belarus. In August 2021, 41 specimens were caught in closed reservoir of the Novodvorka River (Novy Dvor village, Shchuchyn district, Grodno region), and 2 specimens were caught from closed reservoir of the Livanka River (Zasulye village, Stolbtsy district, Minsk region). Both rivers belong to the Neman river basin. In our opinion, the main reason for the origin of brown bullhead in the studied reservoirs is associated with intentional release in nature by anglers.

This study reports on a new translocated population of the Western Greece Goby (Economidichthys pygmaeus Holly, 1929) within the Thrace freshwater ecoregion in Northeastern Greece, approximately 370 km east of the species’ native range (Ionian freshwater ecoregion; Western Greece). Specimens were identified by morphological examination and molecular confirmation. Based on a literature review and anecdotal information the Western Greece Goby was possibly introduced within the last two to five years, perhaps associated with fish farm imports from Western Greece. Population characteristics of the species in the new locations indicate that the species is fully established within an important biodiversity hotspot, the Aggitis sub-basin of the Strymon River, a transboundary river shared with Greece, Bulgaria and North Macedonia. This record represents the easternmost range expansion of the Western Greece Goby. In addition, it confirms a noticeable trend of expansion of this species since it has been also documented in the Southeastern Adriatic (Albania, North Macedonia) and the Western Aegean (southern Greece) during the last decade. This introduction may trigger ecological consequences, including the homogenization of formerly isolated ichthyofaunas.

This report highlights the first recorded occurrence of the Chinese sleeper fish Perccottus glenii (Osteichthyes, Odontobutidae) in the Siverskyi Donets river basin. This invasive species was not historically present in the region but has now established a foothold in the nearby Dnipro river basin. The expansion of the species’ range is believed to have been influenced by both intentional and accidental fish stocking. Additionally, evidence suggests that the species is capable of reaching maturity at a relatively small size, which may have contributed to its successful colonization.

The presence of the cyprinid Pseudorasbora parva is here reported for the first time in Lake Bracciano (Central Italy), a dormant volcanic lake not connected to other water bodies. The lake, historically classified as oligo-mesotrophic, has a surface area of 57 km² and its maximum depth is 165 m. Pseudorasbora parva specimens were first collected during a fish community survey in 2017 and again in 2022. Their total length and body weight ranged from 21 and 81 mm and from 0.25 and 6.43 g, respectively. Since Lake Bracciano is not part of a system of connected water bodies, this record could be evidence of at least a translocation event prior to the first record of 2017, suggesting the need for additional studies and measures to deal with the spread of this invasive species.

Sailfin catfish, Pterygoplichthys, is a genus of fish common in the ornamental aquarium trade. Originally from South America, they are now invasive in numerous locations around the globe. We report the first records of Pterygoplichthys in the United Kingdom. We captured one Pterygoplichthys joselimaianus and one Pterygoplichthys pardalis in an artificial side channel of the River Kelvin in Glasgow, Scotland on 30 August 2021 and 6 September 2021, respectively. Further monitoring and public education will be important as river temperatures increase to prevent establishment of these species, which have become invasive in other parts of the world.

The introduction and dispersal of salmonids have been widespread in Patagonian basins, including anadromous species such as Chinook salmon (Oncorhynchus tshawytscha), rainbow trout or steelhead (O. mykiss), sea-run brown trout (Salmo trutta), and, to a lesser extent, coho salmon (Oncorhynchus kisutch). In recent years, Chinook salmon and steelhead have been reported in the Paraná and Uruguay rivers and in the estuary of La Plata River. This could be a result of long-distance movements, where stray individuals travel northward along the cold Malvinas current. They enter these rivers when it collides with the warm current originating from Brazil. However, this entry takes place within a specific timeframe when the water temperature remains below its lethal thermal threshold. Due to this temperature constraint and their reproductive characteristics, the introduction of salmonids into this basin would not present a risk to the native species. The projected impact of climate change, which anticipates an increase in river temperatures and a southward shift of the Brazilian current, would further support this hypothesis.

Fish translocation for the ornamental fish sector has resulted in the co-introduction of their parasites in a new region. In this study, we are characterized a non-indigenous monogenean, Sciadicleithrum iphthimum, which infected an introduced cichlid, Pterophyllum scalare (Angelfish) imported into India for ornamental purposes. The present species was identified using morphological and molecular data using 18S and 28S rDNA sequences, and they were generated for the first time. We are providing here a morphological description and phylogenetic analysis of S. iphthimum, which appeared genetically close to Sciadicleithrum spp. and nested within dactylogyrid parasites.

The parasites of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) (Cichliformes: Cichlidae) are poorly documented in the U.S. Gyrodactylids can be pathogens of cultured and wild fish populations and their infections can be relevant to the captive maintenance of fishes as well as wild fish health monitoring programs. As part of a survey of the parasites of Nile tilapia cultured within high density flow-through raceways (hydrologically linked to Sougahatchee Creek, Tallapoosa River), we observed numerous specimens of Gyrodactylus cichlidarum Paperna, 1968 (38% prevalence; 2.5 mean intensity) attached to the skin, fins, and gill filaments. This parasite was originally described from the skin and gill of mango tilapia, Sarotherodon galilaeus (Linnaeus, 1758) (Cichlidae) from pools and streams in the Accra Plains, Ghana. Live specimens of G. cichlidarum intended for morphology were heat-killed, formalin-fixed, routinely stained, cleared, and whole-mounted on glass slides. Additional specimens were preserved in 95% ethanol for DNA extraction and sequencing of the internal transcribed spacers 1 and 2 (ITS1, ITS2) and the 5.8S ribosomal DNA. We identified our specimens as G. cichlidarum by having a ventral bar with a distinctive dorsal posteromedial knob and marginal hooks that have a wide aperture and flat sickle base. Our two identical sequences of the ITS1-5.8S-ITS2 differed from a sequence of G. cichlidarum from the United Kingdom by 1 bp. Although this parasite was mentioned in a vaccine study of Nile tilapia in the U.S. in 2011, the present study is the first to diagnose the morphology of G. cichlidarum infecting Nile tilapia in the U.S. (and thereby also the first to deposit whole-mounted voucher specimens of G. cichlidarum from this host and locality). The present study also provides the first nucleotide sequences tethered to a morphological voucher of G. cichlidarum in the U.S., and these resulting sequences were included in a phylogenetic analysis.