Rate of chitobiase degradation as a measure of development rate in planktonic Crustacea

• Published in: Canadian journal of fisheries and aquatic sciences 2000-10, Vol.57 (10), p.1965-1968
• Main Authors: Sastri, Akash R, Roff, John C
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Body size; Ceriodaphnia; chitobiase; Crustacea; Crustaceans; Daphnia magna; Daphnia pulex; Enzymes; Fundamental and applied biological sciences. Psychology; Invertebrates; Life cycle. Embryology. Development; Physiology. Development; Plankton; Zooplankton
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f00-174

We have developed a method to determine development time (molt rate) in both single and mixed populations of crustacean zooplankton based on turnover of the chitinolytic enzyme chitobiase in the ambient medium. We examined the relationship between body size and chitobiase activity released into the medium following molt in three freshwater cladoceran species, Ceriodaphnia spp., Daphnia pulex, and Daphnia magna. Chitobiase activity increased with body length, and a common relationship was observed among all three species (r 2 = 0.82, p < 0.0001). Under steady-state conditions in laboratory cultures, the rate of decay of this enzyme in the medium was balanced by its rate of production by molting animals. The rate of decay of the enzyme in the absence of animals was therefore also its rate of production, which is a measure of the average rate of development of the crustacean zooplankton community. Development times for a D. magna culture (2×) and a Ceriodaphnia spp. - D. magna mixed culture were 65.4 vs. 62 h, 59 vs. 67 h, and 46.6 vs. 50 h, respectively, as measured by this "chitobiase method" versus conventional molt rate determinations.