Il Discus (Symphysodon Aequifasciatus)
- Creato: Venerdì, 22 Aprile 2011 07:17
- Scritto da Claudio Visalli (Claudio)
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Characterization of Discus Mucus During Parenting - By Fred Goodall
Results of studies conducted in 2004 and 2005 have finally answered the question of what is in discus "slime coat" which the fry feed upon.
Mass spectrometry, protein analysis by Bradford assay, free amino acid analysis by chemical testing and finally Electrophoresis was used to identify the proteins, amino acids and peptides in parent discus mucus during fry feeding and cross compared those findings to juvenile discus mucus. All samples were taken by "skin scraping" from the bodies of the test subjects and the ventral area was avoided in all test subjects to eliminate contamination of results by urine.
Fry were in three groups: fry fed only parent fish mucus, those fed with Artemia napulii and tested 1 hour later, those fed Artemia and tested 3 hours later. The interesting thing is that it was found that all fry reduced feeding ( bites of mucus were monitored in a 30 second period ) by day 15 of free swimming. For the fry fed Artemia bite / feeding rates decreased during the 1 hour after eating Artemia... but by 3 hours after Artemia feeding... bites of mucus slowly increased but by day 15 free swimming the bite rate ( number of bites of parent mucus in 30 second periods ) for all 3 groups stayed very low until day 30 of free swimming when the bite rate dropped under 1 bite every 30 seconds.
Parent discus epidermal mucus from females feeding fry of day 10 to 15 free swimming age was compared to non parenting discus of 5 to 6 months age. Parent fish were between 600 grams and 700 grams body weight and juvenile discus were 350 g to 400 g body weight. Individual comparisons might vary due to body mass and production of mucus but as a group compared to another group the body weight "control" allowed uniform group results (1).
These results were that parent discus slime coat ( epidermal mucus ) contains a higher amount of overall protein and specifically a much higher amount of Phenylalanine, an "essential amino acid" while juvenile discus mucus contains higher levels of Alanine, Aspartic acid, Glycine, Proline, Serine, and Leucine. Both parent and juvenile discus had high levels of the essential amino acids Isoleucine and Lysine in their mucus ( Chong, et all, 2005) (1). Spectrometry analysis showed that the parent discus mucus showed matching peptides to a trout ( Oncorhynchus mykiss ) mucus protein named type II epidermal keratin. This is a "structure building" protein and regulates skin growth (1)
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For more details on the findings see the paper: Chong K, Joshi S, Jin LT, Shu-Chien AC. (2005) - Proteomics profiling of epidermal mucus secretion of a cichlid (Symphysodon aequifasciata) demonstrating parental care behavior. Proteomics.
Special thanks to http://www.pds.ph administrator
1. Govoni J.J., Boehlert G. W., Yatanabe, Y. ( 1986 ) The physiology of digestion in fish larvae. Environmental Biology of Fish 16. 59 - 77
2. Warner A H & Matheson C. ( 1998 ) Release of proteases from larvae of the brine shrimp Artemia francissoma and their potential role during the molting process. Comparative Biochemistry and Physiology 119B. 255 - 263.
1. Kenny Chong, Tham Sock Yim, John Foo, Lam Toong Jin, Alexander Chong, 2005 Aquaculture"Characterisation of proteins in epidermal mucus of discus fish ( Symphysodon spp.) duringparental phase".
2. Shephard, K.I. , 1994 Functions for Fish Mucus. Rev. Fish Biol. Fish. 4, 401 - 429.
3. Alexander Chong, Roshada Hashim, Leng-Choy Lee and Ahyaudin bin Ali, 2002, Aquaculture Research, 33, 663 - 672 "Characterization of protease activity in developing discus Symphysodon aequifasciata larva"
Published: January 2006 Practical Fishkeeping Magazine
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