Osmoregulation in the fresh water sponge,Spongilla lacustris

✍ Scribed by Brauer, Elizabeth B.

• Book ID: 102890043
• Publisher: John Wiley and Sons
• Year: 1975
• Tongue: English
• Weight: 937 KB
• Volume: 192
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1401920208

✦ Synopsis

Abstract

External medium passed through the canal system of small Spongilla lacustris at the rate of 70 body volumes per hour, allowing for little or no modification of its composition by the animal. Consequently any osmotic gradient between medium and animal was experienced at the cell level. Forty or more contractile vacuoles arranged around the nucleus in each basal pinacocyte removed fluid at the rate of 24.7 ± 1.0 μm^3^/cell/min in 1.3 milliosmolal (mosm) medium. Output of the contractile vacuoles depended in a nearly linear fashion on the osmotic concentration of the medium, decreasing to zero at 12–16 mosm. The contractile vacuoles responded to the osmotic concentration of the medium, not to ionic strength or the concentration ratios of particular ions. Osmotic concentration of the vacuolar fluid can be estimated as 10–40 mosm, leading to the hypothesis that contractile vacuoles of sponges function by isotonic water separation.