Bacteria Associated with the Surface and Gut of Marine Copepods

Abstract

Little is known about the nature of bacteria associated with the surface and gut of marine copepods, either in laboratory-reared animals or in the natural environment. Nor is it known whether such animals possess a gut flora. The present report deals with studies of microorganisms isolated from healthy, laboratoryreared copepods of the species Acartia tonsa Dana, from several species of wild copepods collected from a marine or estuarine environment, and from laboratory dishes containing moribund copepods. Evidence for a unique gut flora in laboratory-reared animals is presented; the predominant bacteria were represented by the genus Vibrio. Other organisms such as Pseudomonas and Cytophaga were found less abundantly associated with the copepods and not specifically associated with the gut. Acartia tonsa Dana, an estuarine and neritic calanoid copepod, has proved to be useful as an experimental animal in standardized laboratory culture (25). However, little is known about the effects of associated microorganisms on such marine invertebrates, or, in fact, about the actual associations themselves, either in the natural environment or in laboratory cultures. Ecological relationships and changes in such relationships that might occur when wild copepods are brought into culture should be understood, especially if there is a unique association between copepods and bacteria, such as symbiosis or commensalism. Mass mortalities frequently observed in laboratory culture of copepods may be caused by specific pathogens or opportunistic bacteria, but little is known about bacterial pathogens infecting copepods. In addition, the gut flora of the copepod may confer protection on the animals, but until the existence of a commensal gut flora in the copepod is established, such an hypothesis cannot be proven. Research for the project reported here was initiated on a cruise in the Gulf of Mexico aboard the U.S.N.S. MIZAR. Several species of copepods were collected at four different stations, including sites in the open ocean, off the continental shelf, and in the Mississippi Delta. Samples were also collected in the Anclote River,

Luminous microflora associated with the fishes Mugil cephalus and Tachysurus arius

“…Maximum luminous bacterial load was registered in the gut of T. arius when crustaceans formed the major constituents of the diet. The association of luminous bacteria with crustaceans was documented by Baross et al [16] and Sochard et al [17]. Proliferation of luminous microbes might have taken place in the gut of T. arius as a result of the large amount of chitin available during that season.…”

Bacterial diversity associated with freshwater zooplankton

“…Defecation by the host, on the other hand, releases gut flora to the surrounding environment (Tang, 2005). Thus, there is an active exchange of bacteria between zooplankton and the surrounding water, but the different physicochemical characteristics between these environments may favour different bacteria (Sochard et al, 1979;Delille and Razouls, 1994;Hansen and Bech, 1996). Indeed, the anoxic environment of zooplankton gut and faecal pellets may favour strict anaerobes, which otherwise may not survive in the oxygenated water column (Bianchi et al, 1992;Proctor, 1997;Braun et al, 1999).…”

Bacterial flora from the gut of the wild and cultured banana prawn, Penaeus merguiensis

“…Within marine and other aquatic animals, the colonization of the digestive system by micro-organisms is influenced by a number of both host-and non-host-related factors (for a review see Harris 1993). Such factors include the ingestion of the surrounding free-living bacterial community (Austin and Austin 1989), physicochemical aspects of the gut (Hood et al 1971;Huq et al 1986;Griffin et al 1987;Harris et al 1991), environmental conditions and seasonality (Bernard 1970;Sugita et al Campbell and Buswell 1983), diet (Sochard et al 1979;Campbell and Buswell 1983), physiological condition of the host (Yasuda and Kitao 1980) and possibly even habitat type (Sakata 1989;Harris 1993) and farming practices (Prieur et al 1990;Strom and Olafsen 1990). Within the natural environment, conditions may lead to the development of stable populations of gut flora, which may represent the natural or 'normal' flora of the host animal (Lynch and Hobbie 1988;van der Waiij 1992).…”