The fingernail clams (Bivalvia: Veneroida: Sphaeriidae) of Morocco: Diversity, distribution and conservation status

In Morocco, many uncertainties surround the current diversity and distribution of the bivalve family Sphaeriidae. Such information, including taxonomy and conservation status, are vital for further studies to improve the knowledge of this family in Morocco and represents the first step towards the development of a national conservation plan for all freshwater bivalves. Between 2016 and 2019, several investigations were carried out to assess the diversity and distribution of Sphaeriidae in the different basins of Morocco, covering different types of habitat (lakes, springs, rivers and small ponds). The identification of specimens and their morpho-ecological features was based on morphological and morphometric analyses. The data on the general distribution of the collected species allowed the evaluation of their conservation status as well. The shell morphology and morphometric analyses revealed the existence of five species belonging to the genus Pisidium [P. casertanum (Poli, 1791), P. (cf.) personatum Malm, 1855, P. subtruncatum Malm, 1855, P. amnicum (O. F. Müller, 1774) and Pisidium sp.] and one species to the genus of Musculium [M. lacustre (O. F. Müller, 1774)]. Sphaeriidae were found in all Moroccan basins, except Bouregreg and Sakia El Hamra-Oued Eddahab Basins. The results showed that Sebou Basin was the species richest with the occurrence of the five species, while Loukkos and Sous-Massa Basins had the lowest-species richness with one species only. The conservation status of sphaeriids in Morocco was evaluated for the first time and resulted in P. (cf.) personatum and P. subtruncatum being proposed as Least Concern and Vulnerable, respectively, while the status of Regionally Extinct is suggested for both species P. amnicum and M. lacustre. First evaluation of the diversity and species richness of the family Sphaeriidae in Morocco with an assignment of an updated conservation status of the recorded species.

Efficacy and Nontarget Effects of a Spinosad-Based Larvicide in Minnesota Vernal Pools and Cattail Marshes

ABSTRACT Larvicides that contain spinosad, a bacterial metabolite, are used to control mosquitoes in diverse aquatic habitats. These same habitats are home to other invertebrates, including Crustacea—fairy shrimp, isopods, and amphipods—and mollusks—fingernail clams and freshwater snails. A double-blind study evaluated the effects of Natular® G, a granular treatment containing spinosad, on spring Aedes spp. and nontarget invertebrates in vernal wetlands. Within 14 days after application, Natular G controlled larvae of spring Aedes by 53–84%, depending on species, but had no significant effects on numbers of fairy shrimp, fingernail clams, or freshwater snails. A second double-blind study evaluated effects on Coquillettidia perturbans and nontarget isopods and amphipods in cattail marshes. Treatment reduced emergence of Cq. perturbans by 25% but did not change numbers of isopods or amphipods. The 2 experiments indicate Natular G could be effective against spring Aedes in vernal wetlands, less so against Cq. perturbans in cattail marshes, and yet pose minimal risk to crustaceans and mollusks in either vernal wetlands or cattail marshes.

Fluorides in Wastewater Discharges: Toxic Challenges to the St. Lawrence River Biological Community

This literature review examines the risk to fluvial organisms of fluoride released to the St. Lawrence River by the Montréal Urban Community waste-water treatment plant. The following key points are presented regarding the behaviour of fluoride in aquatic systems: fluoride is not removed by primary sewage treatment methods; fluoride from the treatment plant is rapidly diluted to background levels; aquatic plants do not accumulate significant levels of fluoride; fluoride is generally sequestered in the shell/exoskeleton/skeleton and skin of animals and released via the urinary system; fluoride ion is not very toxic in aquatic systems; there is rarely a large difference between acute and chronic (or lethal and sublethal) threshold levels of fluoride in aquatic systems; the most sensitive aquatic organisms are trout and fingernail clams; finally, the only significant evidence of synergistic action is with aluminium. It is concluded that fluoridation of the city of Montréal’s drinking water would not pose any significant additional risk to the biological community in the receiving waters of the St. Lawrence River.

Lesser Scaup diets during migration and winter in the Mississippi flyway

We examined diets of Lesser Scaup (Aythya affinis) during midwinter (N = 41) in southwestern Louisiana (1986), and during spring (N = 57) and fall (N = 48) in northwestern Minnesota (1984–1988). Diets of males and females generally were similar during migration and winter. Diets of adults and immatures differed during fall migration but were similar during winter. In fall, immature scaup fed heavily on amphipods and did not consume certain foods, such as fish and fingernail clams, that were important in adult diets. Aggregate percent dry weight of animal foods was higher during fall (adults 91%, immatures 93%) and spring (92%) than during midwinter (61%). Important foods during all periods were crustaceans, insects, and mollusks.

Use of Fingernail Clams (Pisidiidae) and X-Ray Fluorescence Spectrometry for Monitoring Metal Pollution in Contwoyto Lake, N.W.T.

The suitability of freshwater molluscs, particularly fingernail clams, (Family Pisidiidae) as biological monitors of metal pollution in northern Canada is briefly examined. Qualitative and quantitative analyses of mollusc samples by X-ray fluorescence spectrometry were performed on samples collected just prior to exposure and after approximately three months of exposure to effluent from a newly opened gold mine located near Contwoyto Lake, N.W.T. The resulting contamination factors (post-exposure meta 1 levels in samples divided by pre-exposure levels) indicated an increase of iron, lead and zinc in the clam shells while copper decreased and arsenic remained constant, Contamination factors for clam shells were generally higher than corresponding factors for sampled sediments and fish, suggesting that, as an early warning system, clams may be superior monitors. Preliminary results also indicate that X-ray fluorescence spectrometry is valuable as an analytical technique for shells and soft tissues of freshwater molluscs. The non-destructive nature of XRF allows qualitative analyses to be followed by quantitative analyses and subsequent archiving of samples.