DECAPOD LARVAE AND ANTIBIOTICS
From: Brent Newman btabkn@upe.ac.za
To: crust-l@VIMS.EDU
Sent: June 26, 2000
QUESTION:
A colleague and I have been rearing decapod larvae (Hymenosoma obiculare) in the laboratory, and have a problem with fungal growth. Rearing water (natural seawater) is filtered to 0.5 microns and UV irradiated before use, but the swimming setae on the maxillipeds, especially at high temperatures, develop fungal growths. Although we are still having good survival, this obviously is not a situation which we want. Could anyone advise whether this is fairly common problem (I have seen no specific reference to this problem although fungal problems are mentioned in several papers), and could anyone suggest a suitable antibiotic we could use to eliminate this problem.
Dr Brent Newman
SAB Institute for Coastal Resource Management
University of Port Elizabeth
PO Box 1600 Port Elizabeth
South Africa 6000
Phone +27 41 5042877
Fax +27 41 5832 317
E-mail btabkn@upe.ac.za
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COMMENTS 1 :
We've noticed that egg mortality in blue crabs increases dramatically with heat stress. So you'll want to watch for aberrant development and fungal infections in embryos. A pre-treatment of pen-strep at 500 mg/l ea. helps against bacteria, and amphotericin-B (as Fungizone) is useful against fungi.
Fungizone comes in two formulations. I believe you can get it from Fisher. The liquid formulation contains penicillin, streptomycin and amphotericin B as 0.85% saline. This formulation is a broad antibacterial, antifungal spectrum. The lyophilized formulation contains amphotericin B and sodium deoxycholate. It is specifically for fungi. I would recommend the liquid formulation as it is easy to use and distribute. I used the 500 mg/l pen-strep formulation for egg development work with Cancer anthonyi.
Several papers have examined the efficacy of various fungicides for use in shrimp aquaculture. Early studies reported on the efficacy of malachite green in shrimp culture and used reduced zoopore motility as the primary effect (Bland et al. 1976). Trifluralin and captan showed efficacy (as reductions in mortalities) over 96 hr exposures with minimal larval mortalities (Armstrong et al. 1976). Benomyl was toxic to larvae in 96 hr exposures but showed some efficacy over 48 hr. Furanace showed excellent efficacy against H. milfordensis in shrimp aquaculture (Lio-Po et al. 1985).
Jeffrey Shields
Associate Research Professor
Virginia Institute of Marine Science
Gloucester Point, VA 23062, USA
Tel (804) 684-7128; Fax (804) 684-7186
E-mail: jeff@VIMS.EDU
http://www.lam.mus.ca.us/~tcs/
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COMMENTS 2:
We used to rear all our larvae at U. of MD in a weak solution of Chloramphenicol (sp?) at 5 mg/L. It might affect their ability to osmoregulate to some degree (since antibiotic may affect ciliary action), but if you're after morphology alone or comparative data, it's probably OK.
Reference: Fisher WS, Nelson RT (1978) Application of antibiotics in the cultivation of Dungeness crab Cancer magister. J. Fish. Res. Board Can. 35: 1343-1349.
Joe Staton
E-mail: jstaton@sc.edu