The size and shape of parasitic larvae of naiads (Unionidae) are not dependent on female size

The naiads, large freshwater mussels (Unionida), have very long life spans, are large-bodied, and produce thousands to millions of larvae (glochidia) which typically must attach to host fish tissues to metamorphose into a juvenile mussel. Glochidia develop within a female's marsupial gill demibranch, thus their number is restricted by female size. However, larger mussels acquire more energy, which could be invested in either larger-sized glochidia, in a more glochidia, or a combination of both. The high level of host specialization seen in many naiads may constrain glochidial size and shape around a narrow optimum, while naiads that use a wide range of host fishes may be predicted to possess greater plasticity in glochidial morphology. In this paper, we investigated the relationship between maternal body size and progeny body size and shape, aided by modern digital microscopy. We analyzed the between- and within- species variation of glochidia size and shape relative to female size in four widespread species of European naiads: Anodonta anatina, Anodonta cygnea, Unio crassus and Unio tumidus. Whereas the total reproductive output is collinear with female body size, substantial differences between species in glochidia size were found within genus Anodonta, but not genus Unio where glochidial size is remarkably consistent. The glochidial shape, however, differed within both Unio and Anodonta. We interpret this constant within-species glochidial size in Unio as reflecting a constraint imposed by the likelihood of successful transmission onto and off from a narrow range of hosts, whereas their shape seems to be less constrained. The Anodonta species, inhabiting a wide spectrum of habitats and using more than twice the number of fish hosts than Unio spp., have larger glochidia with greater variation in size and shape. Our results suggest that measures of glochidial variability may also serve as an indicator of host specificity in other naiads.

The Orava dam reservoir – an important site of aquatic molluscs in north-western Slovakia

Mollusc assemblages of the Orava reservoir, the biggest dam reservoir in Slovakia, were studied in 2020. The reservoir, built in 1941–1953, is situated in north-western Slovakia. Sixteen aquatic mollusc species (13 gastropods, 3 bivalves) were recorded. Valvata piscinalis (O. F. Müller), Radix auricularia (Linnaeus) and Gyraulus parvus (Say) were the most frequent; they were recorded in more than ten sites each. Rich mollusc assemblages, composed mainly of gastropods, were found in sites with rich littoral vegetation of macrophytes. The bivalve diversity and abundance were very small, especially compared to the other studied dam reservoirs. The current results were compared with the previous surveys. The occurrence of Radix lagotis (Schrank) is its first reliable record in Slovakia. Viviparus acerosus (Bourguignat), Aplexa hypnorum (Linnaeus), Anodonta cygnea (Linnaeus), non-native Potamopyrgus antipodarum (Gray) and Physa acuta (Draparnaud) were recorded in this area for the first time and their sites are outside their known range in Slovakia.

Use of swan mussel (Anodonta cygnea (Linne, 1758)) as a feed additive for african catfish (Clarias gariepinus (Burchell, 1822))

Purpose. Uzbekistan aquaculture has a huge deficit of balanced feed. In a case of feed production from local ingredients, the problem is the lack of stable source of animal protein. The purpose of this experiment was to find out how swan mussel Anodonta used as a feed additive for African catfish will affect fish growth. Methodology. Minced Anodonta was prepared as follow: mussels were collected from the bottom of ponds after fish harvesting; the collected mussels were kept in the separate aquarium; every day several mussels were taken out, their shells were opened and muscle parts were separated the (mostly mussel leg); then the separated muscle were kept for disinfection in KMnO4 solution of low concentration during 20 min and then crushed to a minced state. Feed was given to African catfish according to a special scheme at the rate of 7% of the fish weight. The control group did not receive the minced mussels and fish were fed with carp feeds.The mixed feed in the experimental group #1 consisted of 50% carp feed and 50% minced mussel. In the experimental group #2, African catfish were fed with minced mussels only. Findings. The experiment showed the clear advantage of feed containing 50% of minced clams and 50% of carp feed. The African catfish fed with this feed significantly overtook fish from the control group in weight because this feed turned out to be either the most balanced in composition or better absorbed by catfish. In the control group, the 100% mixed feed gave an increase of 83.8% in weight and 20.5% in length; in the experimental group #1, the feed (50% mixed feed : 50% minced mussel) gave an increase of 136% in weight and 31.1% in length; at the experiment #2 (100% minced mussel), the feed gave an increase of 95.5% and 20.1% in length. Originality. For the first time the swan mussel was used as a source of animal protein for African catfish.This experiment was conducted for the first time, and it was also found for the first time that the addition of minced swan mussel to the feed of African catfish contributed to a significant weight gain compared to the conventional feed:52.5% more compared to conventional feed and 40.5% more compared to pure minced swan mussel. Practical value. Aquaculturenow is in search of source of animal proteinin connection with growing global deficit of a high quality fishmeal for fish feed production. Use of bivalve mollusks Anodonta, which are also a pest in pond farms, is promising feed for obtaining physiologically determined weight gains. Key words: aquaculture, Africaт catfish (Clarias gariepinus (Burchell, 1822)), feed, animal protein, plant protein, water quality, swan mussel (Anodonta cygnea (Linne, 1758)), weight gain.

Changes of malacofauna in a small lowland river in eastern Poland

In 2016, the species composition and the structure of the dominance of molluscs in the Muchawka River (left-bank tributary of the Liwiec River) were assessed. The occurrence of 19 species of molluscs were recorded, including 11 species of snails and 8 species of mussels. The eudominant was Pisidium casertanum, which, only in the last two sites, constituted 43.1% of all molluscs. Two other species of molluscs from the Sphaeriidae family were also eudominants – Pisidium subtruncatum (22.8%) and Sphaerium corneum (10.3%). Snails were most frequently represented by the dominant Bithynia tentaculata, constituting 5.4% of all molluscs, and the subdominant Bathyomphalus contortus at 2.8%. Sixteen years after the first malacological analysis, an increase in species richness and differences in the dominance of molluscs were found in the Muchawka River. Clams from the Sphaeriidae family invariably dominated but with a different species composition. The disappearance of the protected Anodonta cygnea and Sphaerium rivicola has been noted, and the occurrence of the protected Unio crassus has also been noted.

Experimental infection of brown trout (Salmo trutta), zebrafi sh (Danio rerio), and swan mussel (Anodonta cygnea) with infectious pancreatic necrosis virus (IPVN)

Aim. Although more than 80 fi sh species and some invertebrate aquatic organisms are known to be susceptible to in- fectious pancreatic necrosis virus (IPNV) and aquatic birnaviruses, relatively little is known about its ability to infect brown trout (Salmo trutta), zebrafi sh (Danio rerio), and a mollusk, swan mussel (Anodonta cygnea). Therefore, the aim was to study in more detail the effects of IPNV on the said organisms. The information on the virulence of birnaviruses for aquatic organisms is important for better understanding of their transmission and for the identifi cation of suscep- tible or transient (symptomless) hosts. Methods. Cell culture method, using RTG-2 cells, was used for in vitro culti- vation of IPNV as well as virus titer assessment. The supernatants from infected RTG-2 cells were used for artifi cial inoculation to obtain experimental infection of the fi sh and mollusk. Fish and mollusk behaviour and mortality were monitored daily. The infectious titer of the virus in experimental animals was assessed by cell culture assay and reverse transcription PCR (RT-PCR). Results. This paper presents the results of IPNV experimental infection of brown trout (Salmo trutta), zebrafi sh (Danio rerio), and an aquatic invertebrate mollusk - swan mussel (Anodonta cygnea). The mortality of brown trout and zebrafi sh was 76.6 and 40 % respectively. Swan mussel was apparently resistant to the virus, but it apparently accumulated and maintained substantial levels (up to 10 -10 ID 50 /ml -1 ) of the virus for the dura- tion of the experiment (35 days). The highest infectious titer was found in brown trout (10 6 ID 50 /ml -1 ). In zebrafi sh and swan mussels, it was up to 10 4.5 ID 50 /ml -1 and 10 2 ID 50 /ml -1 respectively. Conclusions. At the end of the experiments the IPNV titers were higher than the initial viral doses in brown trout and zebrafi sh, indicating virus reproduction. In diseasesd fi sh the blackening, whirling and anorexia were observed. It was shown that swan mussel accumulates and maintains virus for at least 35 days under experimental conditions and that it may act as symptomless vector of IPNV