EFFECTS OF TEMPERATURE AND SALINITY ON NITROGENOUS EXCRETION BY LITOPENAEUS VANNAMEI JUVENILES

Dong-Huo Jiang, A.L. Lawrence, W.H. Neill, H. Gong-2000

Journal of Experimental Marine Biology and Ecology, 253 (2): 193-209
Abstract:

Excretion rates of ammonia-N, nitrite-N, nitrate-N, and dissolved organic nitrogen (DON) for juvenile Litopenaeus vannamei (3.85±0.83 g) were quantified in response to nine different combinations of temperature (24, 28, and 32°C) and salinity (10, 25, and 40 ppt) under laboratory conditions. Results indicated that L. vannamei is ammonotelic, with ammonia-N accounting for 61.9--84.3% of total nitrogen (TN) excretion. There were significant effects of temperature and salinity, but no significant interaction between them, on ammonia-N excretion rate (RAN). RAN increased with increasing temperature, over the interval 24--32°C. RAN was lower at 25 ppt than at 10 and 40 ppt, at all temperatures. DON excretion rate (RDON) was not significantly influenced by either temperature or salinity; the overall mean RDON was about 5.24 µg-N g -1 h -1. However, the percentages of DON in TN (PDON) varied from 15.4 to 36.4% under the various temperature--salinity combinations. PDON at 28 and 32°C was significantly lower than at 24°C, and PDON at 10 ppt was significantly lower than at 25 and 40 ppt. Only very small amounts of nitrogen were excreted by L. vannamei as nitrite-N and nitrate-N.

(Shrimp Mariculture Project, Texas Agricultural Experiment Station, Texas A&M University System, 1300 Port Street, Port Aransas, TX 78373, USA)

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