FIRST RECORD OF THE FOUNTAIN BLADDER SNAIL PHYSA FONTINALIS (LINNAEUS, 1758) (GASTROPODA: HYGROPHILA) IN MOROCCO

a bsTracT : Alien and invasive species pose a significant threat to global biodiversity, causing costly economic and environmental damage. Recent field surveys in northern Morocco have led to the discovery of the fountain bladder snail Physa fontinalis (Linnaeus, 1758), providing the first evidence of its occurrence in North Africa. The exotic species is currently only known from one locality in Morocco, future surveys may reveal its presence elsewhere. It is essential to monitor its spread within invaded areas and conduct studies to improve our understanding of its biology, ecology, and


INTRODUCTION
Aquatic snails belonging to family Physidae Fitzinger, 1833 are air-breathing freshwater gastropods, commonly known as the Bladder snails.Members of the family have sinistral shells, which are semi-transparent and fragile, with no operculum or umbilicus (TacheT et al. 2010).Bladder snails have slender and elongated tentacles, and the family is characterised by the presence of a preputial gland.Some species have an extended mantle margin that can partially cover the shell (Te 1978, Glöer 2019).
Also commonly known as pond snails (boucheT & rocroi 2005), Physidae are opportunistic aquatic gastropods, their diet includes both detritus and algae and they can inhabit all types of environments including streams, rivers, ponds, lakes, springs, canals and irrigation ditches.Additionally, they occur in both nutrient-poor and richly vegetated habitats (Glöer 2019) and are hermaphrodites.They encapsulate their eggs in a gelatinous substance that can hold between 40 and 180 eggs (oscoz et al. 2011).Considering the water quality, they can tolerate high temperatures and salinity, and some species are resistant to organic pollution (larraz et al. 2007, Vázquez-caPoTe et al. 2015).
The family Physidae is highly diverse, consisting of approximately 80 species with a cosmopolitan distribution across almost all continents (TaYlor 2003).The widespread distribution of these species is largely attributed to human-mediated introductions (AlbrechT et al. 2009).Previously, the only known representative of the Physidae family in Morocco was the non-native Physella acuta (Draparnaud, 1805), which is widely distributed throughout the country (TaYbi et al. 2017(TaYbi et al. , 2023b)).Recent field surveys conducted in the Northern part of Morocco have led to the discovery of Physa fontinalis (Linnaeus, 1758), which represents the first confirmed record of this exotic species in Morocco and in North Africa as a whole.

MATERIAL AND METHODS
In order to promote knowledge on the freshwater molluscs of Morocco, several field expeditions have been conducted since 2014 in the northern part of the country, with a special focus on Protected Areas.Most of these sampling sites were visited several times.The gastropods (and benthic fauna in general) were collected using Surber samplers (20×25 cm surface area, 400 µm mesh).For each sample, a first sorting was carried out on the field during which the fauna was preserved in a jar containing alcohol.A second and finer sorting was performed in the laboratory under a binocular loupe in which all remaining mac-roinvertebrates were recovered and stored in alcohol up to 70% of the volume.Water conductivity, pH, and dissolved oxygen were measured in situ with a multiparametric measuring device (WTW, Multi-Line P4).Other parameters (ammonium and Biological Oxygen Demand (BOD 5 )) were measured in the laboratory.Photographs were made with a digital camera system (Leica Microscope M205C with digital camera Leica DMC5400).The map was made using ArcGIS software.Voucher specimens were deposited in the collections of the authors.Identifications were made using the identification key of Glöer (2019).

RESULTS
The first natural population of Physa fontinalis has been discovered in Morocco.About twenty individuals of the fountain bladder snail were collected in a small retention reservoir for waters from the Isekagen spring, as well as in its irrigation channels on 05/10/2022 and 10/09/2023 (Fig. 1).The spring is located in the north-east of Morocco (35°09'53.7"N,3°00'06.4"W), in the province of Nador.The shell size ranged between 6.5-8 mm in height and 4-6 mm in broad.
The body of Physa fontinalis is brown to black and the edges of the mantle extend as finger-like lobes Physa fontinalis seems to require habitats with good water quality.The analysis of the physico-chemical parameters of the water (ammonium and BOD 5 ) showed a good environmental quality of the water, according to the Moroccan standards for the quality of surface waters (Table 1).

DISCUSSION
Physa fontinalis is a Holarctic species; it has a wide distribution in the western Palaearctic, covering nearly all of Europe (Glöer 2019).In the neighbour-ing areas in the south-western Palearctic, the species has been recorded from the south of the Iberian Peninsula, Madeira and Canary Islands (GbiF 2023).We record it for the first time from Morocco and therefore from North Africa, increasing the known aliens of the Bladder snails to two species in Morocco.The pathways by which P. fontinalis was introduced into Morocco are unknown, although aquar istics and the ornamental plant trade remain the most likely pathways, as is the case for the majority of exotic gastropods in Moroccan freshwaters (TaYbi et al. 2023b).Future surveys may reveal more occurrences of Physa fontinalis in the country and the rest of the continent.
In recent years, there has been significant progress in knowledge of the freshwater mollusc fauna of Morocco, with the addition of many new species, including genera and species that are new to science (Glöer et al. 2020a, b, Mabrouki et al. 2021, 2023a, TaYbi et al. 2022, BesPalaYa et al. 2023).However, the inventory list of the freshwater gastropod fauna of Morocco is certainly still incomplete.It is more important than ever to step up research into these vulnerable invertebrates, given the multiple threats they face.Freshwater habitats and biodiversity are increasingly being affected by human activities in Morocco, and freshwater ecosystems may well be the most endangered ecosystems, by water pollution in densely populated regions and leaching through permeable soils of contaminants such as water Usually more tolerant and resilient than native gastropods fauna, these invasive snails well take advantage of the effects of climate change and the increasing deterioration of water quality of the freshwater ecosystems of North Africa.Hence the importance of monitoring these species in order to mitigate the impact on indigenous communities.

Fig. 1 .
Fig. 1.Distribution range of Physa fontinalis in the extreme south-western Palearctic and its habitat in Morocco at Isekagen Spring (old records from GBIF 2023)