Shrimp keepers and breeders are always looking into ways to improve color and brightness of their shrimps. While careful breeding and selection plays a big role in the perfect and gorgeous tint, let’s talk about what any hobbyist could do today by supplementing pigment improving elements into the shrimp diet. And the stars here are carotenoids.
Carotenoids are a family of over 600 natural lipid-soluble pigments that are produced within microalgae, phytoplankton, and higher plants. They are responsible, in combination with proteins, for many of the brilliant yellow to red colors in plants and the wide range of blue, green, purple, brown and reddish colors of fish and crustaceans.
However, shrimps are unable to produce carotenoids including astaxanthin themselves, only plants and protists (bacteria, algae, fungi) are capable of synthesizing carotenoids.
Ever wonder why shrimp look red when cooked? Here is when carotenoproteins come into play. Carotenoids form a bond with proteins and when this bond is broken due to the high temperature, then the reddish color of the carotenoid, most often astaxanthin, replaces the natural color of the shrimp produced by the carotenoproteins.
In Caridina shrimp the pigments are found in the cuticle (exoskeleton) or in specialized cells called chromatophores. Chromatophores are mostly responsible for color underneath the cuticle deeper in the body.
Chromatophores are broken into four main categories:
- Black chromatophores, containing ommochromes, which absorb light
- Red chromatophores, generally containing astaxanthin
- Yellow chromatophores, generally containing lutein
- White chromatophores, containing pterines or flavines, which reflect light
Astaxanthin is one of the most powerful carotenoids. Survival was higher in shrimps fed the astaxanthin diet, and a positive correlation between survival and pigment concentration of tissues suggested that the carotenoids functioned as an intracellular oxygen reserve.
Shrimp fed astaxanthin at 100 mg/kg diet had an average survival rate of 77% in contrast to shrimp supplemented with β-carotene which averaged 40% (Chien 1996).
Additional benefits of this essential carotenoid include roles as an antioxidant and provitamin A activity, as well as enhancing immune response, reproduction, growth, maturation, photoprotection, and defense against hypoxic conditions.
Astaxanthin is crucial supplement for shrimps as it improves not only color but affects survival rates as well.
Red Cherry Shrimps were fed astaxanthin diet for 8 weeks and kept in 3 different color gravels (white, red and black)
After 8 weeks researches could easily observe color difference, weight gain and survivability.
There are some unexpected natural sources of astaxanthin as well. Paprika contains the xanthophylls beta-carotene, beta-cryptoxanthin, capsanthin and capsorubin, some of which can be slowly converted to astaxanthin.
Astaxanthin is added to most commercial complete food for shrimp produced by companies such as Shrimp King, Shirakura, MK Breed, Garnelenhaus.
You can also supplement shrimps with other carotenoids using natural alternatives. Natural snacks for shrimps that contain carotenoids: marigold petals, pumpkin, carrots, spinach, mulberry leaves,dandelions, moringa, kale.
Goodwin T.W. The Biochemistry of the Carotenoids, 2nd ed., Chapman and Hall, London, 1984, pp. 64-96
A Review of the Carotenoid, Astaxanthin, as a Pigment and Vitamin Source for Cultured Penaeus Prawn By Todd Lorenz, Ph.D
Matsuno T. and S. Hirao. Marine Carotenoids, in “Marine Biogenc Lipids, Fats, and Oils” (ed. by R. G. Ackman), Vol. 1, CRC Press, Florida, 1989, pp. 251-388.
Effect of Dietary Astaxanthin and Background Color on Pigmentation and Growth of Red Cherry Shrimp, Neocaridina heteropoda
Department of Animal Production Technology and Fisheries Faculty of Agricultural Technology,
Nongnuch Laohavisuti and Uscharee Ruangdej
Remarkable Shrimps: Adaptations and Natural History of the Carideans Raymond T. Bauer