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<p>The brown sea cucumber, <i>Isostichopus fuscus</i>, listed under CITES, has been explored for aquaculture to alleviate pressure on its natural populations in the tropical Eastern Pacific. However, high mortality rates during early life stages, particularly in juveniles, present a significant challenge. Optimizing culture conditions requires a deeper understanding of its digestive physiology. This study analyzed digestive enzymatic activities in the tentacles, foregut, and mid-hindgut of <i>I. fuscus</i> and evaluated in vitro digestion of six potential diet components: macroalgae powders (<i>Egregia</i> sp., <i>Ulva lactuca</i>, <i>Macrocystis pyrifera</i>, and <i>Sargassum</i> sp.) and protein sources (fish and soy flours). Protein digestion occurred mainly in the foregut (3.57 ± 1.52&#xa0;mU/mg protein) and mid-hindgut (69.14 ± 7.68&#xa0;mU/mg protein) peaking at pH 7 and 8. Specific substrates (BApNA and SApNA) and inhibitors (PMSF and TLCK) were used to determine that the proteolytic activity is driven by serine peptidases, trypsin, and to a higher extent, chymotrypsin. Serine peptidase activity was detected in tentacles, foregut, and peaked in the mid-hindgut, where chymotrypsin activity reached 47.08 U/mg protein. Amylase activity was higher in the mid-hindgut (5.64 ± 0.28&#xa0;mU/mg protein) compared to the foregut (0.06 ± 0.06&#xa0;mU/mg protein), while lipase activity was found only in the tentacles (0.011 ± 0.003&#xa0;mU/mg protein). This is the first report of amylase and lipase activity in <i>I. fuscus</i>, highlighting its ability to digest carbohydrates and lipids. In vitro tests revealed greater hydrolysis (&gt; 2.4%) of <i>Egregia</i> sp., fish meal, and soybean meal. These findings provide a basis for developing experimental diets specifically designed to enhance the survival and growth of <i>I. fuscus</i> in aquaculture systems.</p>

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Characterization of the enzymatic activity along the digestive tract of the brown sea cucumber Isostichopus fuscus and in vitro digestibility of dietary ingredients

  • 期刊论文

  • 发表日期：

    2025年7月3日

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  • Miguel Ángel Suárez Roca,
  • Sergio Scarry González Peláez,
  • Oscar Trujillo Millán,
  • Teresa Sicard González,
  • Liliana Rojo Arreola

摘要

The brown sea cucumber, Isostichopus fuscus, listed under CITES, has been explored for aquaculture to alleviate pressure on its natural populations in the tropical Eastern Pacific. However, high mortality rates during early life stages, particularly in juveniles, present a significant challenge. Optimizing culture conditions requires a deeper understanding of its digestive physiology. This study analyzed digestive enzymatic activities in the tentacles, foregut, and mid-hindgut of I. fuscus and evaluated in vitro digestion of six potential diet components: macroalgae powders (Egregia sp., Ulva lactuca, Macrocystis pyrifera, and Sargassum sp.) and protein sources (fish and soy flours). Protein digestion occurred mainly in the foregut (3.57 ± 1.52 mU/mg protein) and mid-hindgut (69.14 ± 7.68 mU/mg protein) peaking at pH 7 and 8. Specific substrates (BApNA and SApNA) and inhibitors (PMSF and TLCK) were used to determine that the proteolytic activity is driven by serine peptidases, trypsin, and to a higher extent, chymotrypsin. Serine peptidase activity was detected in tentacles, foregut, and peaked in the mid-hindgut, where chymotrypsin activity reached 47.08 U/mg protein. Amylase activity was higher in the mid-hindgut (5.64 ± 0.28 mU/mg protein) compared to the foregut (0.06 ± 0.06 mU/mg protein), while lipase activity was found only in the tentacles (0.011 ± 0.003 mU/mg protein). This is the first report of amylase and lipase activity in I. fuscus, highlighting its ability to digest carbohydrates and lipids. In vitro tests revealed greater hydrolysis (> 2.4%) of Egregia sp., fish meal, and soybean meal. These findings provide a basis for developing experimental diets specifically designed to enhance the survival and growth of I. fuscus in aquaculture systems.