Release of the enzyme chitobiase by the copepod Temora longicornis:characteristics and potential tool for estimating crustacean biomass production in the sea

Abstract

ABSTRACT. The chitlnolytic enzyme chitobiase (N-acetyl-P-D-glucosaminidase), which is expressed during the pre-moult phase of crustaceans, is released into the ambient water after shedding of the exuvium. We examined the potential use of chitobiase activity in water samples as a measure of secondary production of crustaceans. Chitobiase activity, expressed on the substrate 4-methylumbelliferyl-N-acetyl-P-D-glucosaminide (MUFNAG), was measured in experiments with the marine copepod Ternora longicornis, with focus on the dissolved ('free', c0.2 pm) fraction. Significant activity of free chitobiase was found in the ambient water of individual copepodites when they moulted to enter the next stage. The activity of the chitobiase released was linearly related to body weight and to the increment of body weight. In bacteria-poor water (filtered through 0.2 pm), no significant decrease of free T longicornis chitobiase occurred in the first 24 h. In non-manipulated water, the decay of free T. longicornis chitobiase by bacteria was exponential with time, with relative rates varying by 4 to 13% h-' at 15°C. The particle-bound chitobiase activity was related to the number of bacteria. Different sources of chitoblase could be distinguished by enzyme characteristics. The K, value of T longicornis chitobiase was 55 pm01 I-', comparable to values published for Daphnia species. In Oxyrrhis marina, a heterotrophic dinoflagellate serving as the main food item in the longicornis culture, enzyme assays indicated a K, < 0.2 pm01 1-'. Water predominantly containing bacteria showed a K, > 100 pm01 1-l. The usefulness of free chitobiase as a natural tracer of secondary production was tested in a culture vessel of T. longicornis. The rate of chitobiase release was derived from the chitobiase activity in the ambient culture water over time and the rate of decay in water samples devoid of copepods. From the relation between release of chitobiase and increase of body weight of moultlng copepodites, the total daily biomass increase in the culture vessel was calculated. These estimates compared well wlth classical monitoring of biomass changes. If this relation found in T. longicornis is representative of marine crustaceans in general, tracking of free chitobiase in water samples could be a biochemical tool for estimating in situ secondary production in natural waters.

Are Bacteria the Major Producers of Extracellular Glycolytic Enzymes in Aquatic Environments?

“…VRBA et al, 1993). As far as we know, the high-affinity -N-acetylhexosaminidase has been always detected in the presence of protistan bacterivores (VRBA et al, 1993(VRBA et al, , 1996aOOSTERHUIS et al, 2000) or related to their biomass (ZUBKOV and SLEIGH, 1998).…”

“…To summarise, the following possible sources of -N-acetylhexosaminidases may significantly contribute to its total activity in aquatic environments: (i) chitinolytic bacteria producing particle-bound, low-affinity (K M ≥ 100 µmol l -1 ) -N-acetylhexosaminidase (VRBA et al, 1993;MACEK et al, 1996); (ii) another particle-bound, high-affinity (K M < 1 µmol l -1 ) enzyme related to protozoan occurrence (probably to digestion of prokaryotic prey; GON-ZÁLEZ et al, 1993;VRBA et al, 1993VRBA et al, , 1996dZUBKOV and SLEIGH, 1998); (iii) a free, lowaffinity (K M~6 0 µmol l -1 ) -N-acetylhexosaminidase released into water during arthropod moulting (VRBA and MACHÁČEK, 1994;ESPIE and ROSS, 1995;VRBA et al, 1997;JENKINS et al, 1998;OOSTERHUIS et al, 2000); (iv) in addition, diatoms apparently produce a particle-bound, low-affinity (K M > 150 µmol l -1 ) -N-acetylhexosaminidase (SMUCKER and KIM, 1991;VRBA et al, 1997;SHERR and SHERR, 1999; this study).…”

“…VRBA et al, 1992VRBA et al, , 1996cHOPPE et al, 1998). During the last decade, it has become obvious that other sources may contribute to the extracellular activity of -N-acetylhexosaminidase, chitobiase or lysozyme detected in water samples (GONZÁLES et al, 1993;VRBA et al, 1993VRBA et al, , 1996aVRBA et al, , d, 1997VRBA and MACHÁČ EK, 1994;ESPIE and ROFF, 1995;JENKINS et al, 1998;ZUBKOV and SLEIGH 1998;SHERR and SHERR 1999;OOSTERHUIS et al, 2000;VRBA, 2000). Moreover, KARNER et al (1994) reported release of α-glucosidase and aminopeptidase by phagotrophic flagellates and BOCHDANSKY et al (1995) experimentally proved that marine copepods may release α-and -glucosidases.…”

Metabolic energy demand and food utilization of the hydrothermal vent crab Xenograpsus testudinatus (Crustacea: Brachyura)

“…Crustaceans require chitinolytic enzymes for molting (Oosterhuis et al 2000) but they also synthesize chitinolytic enzymes in the digestive organs (Saborowski et al 1993, Peters et al 1999. High activities of digestive chytinolytic enzymes may indicate that the vent crabs are capable of digesting and utilizing chitin from crustacean shells as a source of both carbon and nitrogen .…”

Multiple Enzyme Analyzer (MEA): Steps toward the in situ detection of microbial community ectoenzyme activities

“…One step in organic matter use is the production of ectoenzymes by bacteria and phytoplankton (Martinez and Azam 1993;Gonzalez-Gil et al 1998), usually on or near the cell surface, to initiate the hydrolysis of polymers otherwise too large to be taken up by the cell. Similar enzymes may also be released into the water, either by bacteria and phytoplankton or by zooplankton during molting (Oosterhuis et al 2000;Richards et al 2008). The activity of a particular ectoenzyme can act as an indicator of the nutritional needs of a microbial community (Sala et al 2001) and may rapidly change in response to substrate availability and ecosystem dynamics, such as the growth and decay of phytoplankton blooms (Lancelot and Billen 1984;Riemann et al 2000).…”