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Freshwater mussels are declining globally, and effective conservation requires prioritizing research and actions to identify and mitigate threats impacting mussel species. Conservation priorities vary widely, ranging from preventing imminent extinction to maintaining abundant populations. Here, we develop a portfolio of priority research topics for freshwater mussel conservation assessment. To address these topics, we group research priorities into two categories: intrinsic or extrinsic factors. Intrinsic factors are indicators of organismal or po-pulation status, while extrinsic factors encompass environmental variables and threats. An understanding of intrinsic factors is useful in monitoring, and of extrinsic factors are important to understand ongoing and po-tential impacts on conservation status. This dual approach can guide conservation status assessments prior to the establishment of priority species and implementation of conservation management actions.

Digestive enzymes and their effects on in vitro digestibility of feeds and feedstuffs, as well as on growth performance quality were studied in Siamese fighting fish (Betta splendens Regan, 1910). The specific activities of total protease, amylase, trypsin and chymotrypsin increased during development and were higher in females than in males at maturation (P < 0.05). The activity ratio of trypsin to chymotrypsin corresponded to fish growth, and showed lower values in females than in males. White muscle levels of RNA decreased during development, with females having higher levels than males, while the protein levels increased with no difference between sexes. In the oocytes, trypsin-like and chymotrypsin-like specific activities were very low, and the concentrations of RNA, protein and protein/lipid ratio were higher than in the muscle. For in vitro digestibility, wheat gluten, soybean meal and fish meal were among good protein sources while the meals from peanut, fish and soybean were good carbohydrate sources. Golden apple snail meat was a good source for both protein and carbohydrate. The crude enzyme extracts from different growth stages and sexes had different abilities to digest the same feeds and feedstuffs. This will make it possible to preliminarily study the authenticated nutritional quality of raw materials for future feed formulations for B. splendens.Keywords: Betta splendens, digestive enzymes, feedstuff, in vitro digestibility, muscle quality, oocyte quality, Siamese fighting fishAfrican Journal of Biotechnology Vol. 12(14), pp. 1689-1702

Summary Analyses of several organic and inorganic elements in the plasma of different fish species in control and infested conditions with the freshwater mussel Hyriopsis (Limnoscapha) myersiana (Lea, 1856) were undertaken. The most suitable composition of plasma corresponded to the fish species which produced the highest number of transformed glochidia. The infestation assay showed that glochidia of H. myersiana had a short transformation period of 6–12 days to reach the juvenile stage. The highest recovery peak could be seen in the plasma of the common carp, with lower peaks in the nile tilapia, hybrid catfish and striped catfish. The significant increase at days 3 (P

Several organic and inorganic sources from the plasma of different fish species and horse serum were utilized as additives to the artificial culture M199 medium to improve glochidial survival and transformation of Hyriopsis myersiana. After 2–3 days of culturing in the medium containing plasma of Nile tilapia or hybrid catfish, striped catfish or horse serum, the glochidia presented significantly (P

Summary The ultrastructure of early stages of the mussel, Hyriopsis (Limnoscapha) myersiana (Lea, 1856), was observed by scanning electron microscopy from the glochidial period until the onset of the juvenile stage 10 days later. Further observations were performed for an additional 13 days to assess juvenile development. Glochidia extracted from the brood chambers have a hookless, semi-oval and equivalve calcareous shell with numerous pores in the internal surface, pits in the external surface and cuticular spines in the ventral region. Keratin fibers with a random arrangement in the cuticle of the glochidial shell were also detected. The appearance of the foot within 10 days of in vitro glochidial culture was considered the main feature of metamorphosis to the juvenile stage. Another change during the following 13 days was the formation of a new periostracum exhibiting growth lines under the old glochidial shell. This development occurs mainly in the anterior region and is followed by hardening of the p...

The freshwater pearl mussel, Hyriopsis myersiana (Limnoscapha) (Lea, 1856) was cultured in two artificial media at 23±2°C. Each artificial medium contained a mixture of M199, (Life Technologies, No. 71N0262) horse serum or fish ( Oreochromis niloticus ) artificial medium plasma as a protein source, and antibiotics/antimycotics at a ratio of 2:1:0.5. Glochidia were reared until they became juveniles, i.e. until the mantle and foot could be observed under a light microscope. The duration of glochidia development until the juvenile stage was 9–10 days in both media. After 1 month of controlled feeding with phytoplankton, the juveniles showed an elongate of shell with several growth lines. The more suitable artificial culture formula for the transformation from glochidia to juvenile stage was the medium containing protein from fish plasma. Survival from glochidia to juvenile stage was up to 85.3±3.9% in fish plasma, while it was equal to 46.2±12.7% in horse serum. The transformation from glochidia to juvenile stage was up to 84.3±2.3% in fish plasma, while it was equal to 44.3±8.9% in horse serum. Percentage survival and transformation from glochidia to juvenile stage were significantly higher in fish plasma than in horse serum ( P

Journal homepage: http://kasetsartjnatsci.kasetsart.org/ Temperature (20-80°C) and pH (2-12) profiles of amylase and lipase at three stages (10-dayold, 1.5-month-old and 3-month-old) in Siamese fighting fish Betta splendens Regan, 1910) were studied. At least nine amylase activities were observed during development: pH 7 at 40°C, pH 9 at 30°C and 50° C, pH 8 and pH 11 at 50°C in females and pH 8 and pH 11 at 40°C and 60°C in males. At the younger stage (≤ 1.5 month old), activity at pH 7 and 40°C, and at pH 9 and 30°C and 50°C was observed. At the older stage (≥ 1.5 month old), amylase activity at pH 8 and pH 11 in the temperature range of 40-60°C was found. Lipase had at least five levels of activity: pH 7 at 20°C and 40°C, pH 8 at 20-40°C and 60°C, and at pH 11, where the activity peak disappeared in the maturing stage (3 month old) in both sexes. Amylase had very low specific activity at the 10-day-old stage, while lipase had a high specific activity, similar to older stages. The most suitable pH to determine amylase and lipase activity in Siamese fighting fish was pH 8, whereas a temperature of 50°C was appropriate for amylase and 40°C was suitable for lipase, regardless of sex and age. This information is a prerequisite for future studies of the in vitro digestibility evaluation of nutrient utilization in Siamese fighting fish.

Journal homepage: http://kasetsartjnatsci.kasetsart.org/ Characterization of total proteases, trypsin and chymotrypsin were performed at pH 2 12 and temperatures 20-80°C in three life stages of Siamese fighting fish (Betta splendens Regan, 1910). At least fourteen protease activities were detected, including seven acidic (pH levels 2, 4 and 5-6), one neutral (pH 7), and six alkaline (pH levels 8-12) activities in the optimal temperature range of 30-60°C. The neutral and alkaline pH profiles were different between sexes during the on-growing stage (1.5 month-old). The acidic proteases played a major role in digestion in the early life stage (10-day-old), while the alkaline proteases became more important toward older stages. Trypsin and chymotrypsin showed similar characteristics with at least five activities observed. For trypsin, activity was detected with pH 7 and 8 at 50°C, and pH 10 at 30, 50 and 60°C. For chymotrypsin, activity was found at pH levels 7 and 8 at 50°C, and pH 10 at 30, 40 and 50°C. Regardless of sex and age, the most suitable conditions for studying digestive enzyme activities in general were at pH 8 and 50°C for total proteases, pH 7-8 and 50°C or pH 10 and 30-35°C for trypsin and pH 7-8 and 50°C or pH 10 and 40°C for chymotrypsin. Trypsin and chymotrypsin are important proteases showing similar general optimal conditions to that of total proteases. This information provides elementary knowledge for studying protein digestibility by in vitro techniques and for determining growth performance quality using digestive enzyme markers in Siamese fighting fish.

Freshwater mussel Chamberlainia hainesiana is a vulnerable species in Thailand. The species has a lustrous nacreous shell that can be utilized for various purposes, and has a potential industrial use for producing freshwater pearl. Characterization of digestive enzymes would provide critical information prerequisite for studying the development of digestive enzymes during on–growing as well as for in vitro digestibility study important for the development of suitable artificial feed formulations for the commercial culture. The aim of this preliminary study was to determine optimum pH and temperature for three digestive enzymes: amylase, protease and lipase, from digestive gland including stomach of adult C. hainesiana under various pH’s (2–11) and temperatures (25–80°C). The results revealed at least three isoforms of amylase and protease, and at least 4–5 isoforms of lipase. No alkaline protease activity was detected. For future enzyme expression study, the suitable optimal conditions are 40°C pH 6 for amylase activity, 50°C pH 5 for protease activity, and 50°C pH 8 for lipase activity. At natural habitat of around 30°C, these enzymes are most active at pH 6, 6, and 8 (or 10), respectively, which are suitable conditions for future study on in vitro digestibility.