AJP - Regulatory, Integrative and Comparative Physiology, Vol 234, Issue 5 216-R222, Copyright © 1978 by American Physiological Society
Micropuncture studies of the osmoregulation in the nauplius of Artemia salina
D. Russler and J. Mangos
The osmoregulation of the nauplius of the brine shrimp, Artemia salina, was
investigated using micropuncture and microanalytical techniques. The
naupliar body fluid, hemolymph was hyposmotic to and had lower Na
concentrations than the suspending medium for the range of medium
salinities from 80 to 4,900 mM NaCl. In medium containing 20 mM NaCl, the
hemolymph was hyperosmotic to the medium, with osmolarity of 101 +/- 8
mosmol/1 and with [Na] of 49 +/- 11 meq/1. Whereas the maximal observed
NaCl concentration gradient between hemolymph and medium was 4,785 mM,
during the incubation of nauplii in artificial seawater (osmolarity: 932
mosmol/1; and [Na]: 502 meq/1) the osmolarity and [Na] of the naupliar
hemolymph were 161 +/- SD 16 mosmol/1 and 86 +/- 14 meq/1, respectively.
The influx and efflux of Na between medium and hemolymph were measured
using 22Na. The fluxes of this ion were temperature dependent. The main
site of efflux of 22Na was the neck organ as was shown by experiments of
differential recovery of 22Na introduced in the hemolymph. These studies
demonstrate that the nauplius of A. salina has the ability to osmoregulate
not only against high environmental salinities but also against low
salinities approaching those of freshwater.
