Gastro-intestinal handling of water and solutes in three species of elasmobranch fish, the white-spotted bamboo shark, Chiloscyllium plagiosum, little skate, Leucoraja erinacea and the clear nose skate Raja eglanteria

W. Gary Anderson, Patricia J. Dasiewicz, Suadi Liban, Calen Ryan, Josi R. Taylor, Martin Grosell, Dirk Weihrauch

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

The present study reports aspects of GI tract physiology in the white-spotted bamboo shark, Chiloscyllium plagiosum, little skate, Leucoraja erinacea and the clear nose skate, Raja eglanteria. Plasma and stomach fluid osmolality and solute values were comparable between species, and stomach pH was low in all species (2.2 to 3.4) suggesting these elasmobranchs may maintain a consistently low stomach pH. Intestinal osmolality, pH and ion values were comparable between species, however, some differences in ion values were observed. In particular Ca2+ (19.67 ± 3.65 mM) and Mg2+ (43.99 ± 5.11 mM) were high in L. erinacea and Mg2+ was high (130.0 ± 39.8 mM) in C. palgiosum which may be an indication of drinking. Furthermore, intestinal fluid HCO3- values were low (8.19 ± 2.42 and 8.63 ± 1.48 mM) in both skates but very high in C. plagiosum (73.3 ± 16.3 mM) suggesting ingested seawater may be processed by species-specific mechanisms. Urea values from the intestine to the colon dropped precipitously in all species, with the greatest decrease seen in C. plagiosum (426.0 ± 8.1 to 0 mM). This led to the examination of the molecular expression of both a urea transporter and a Rhesus like ammonia transporter in the intestine, rectal gland and kidney in L. erinacea. Both these transporters were expressed in all tissues; however, expression levels of the Rhesus like ammonia transporter were orders of magnitude higher than the urea transporter in the same tissue. Intestinal flux rates of solutes in L. erinacea were, for the most part, in an inward direction with the notable exception of urea. Colon flux rates of solutes in L. erinacea were all in an outward direction, although absolute rates were considerably lower than the intestine, suggestive of a much tighter epithelia. Results are discussed in the context of the potential role of the GI tract in salt and water, and nitrogen, homeostasis in elasmobranchs.

Original languageEnglish (US)
Pages (from-to)493-502
Number of pages10
JournalComparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Volume155
Issue number4
DOIs
StatePublished - Apr 2010

Keywords

  • Ammonia
  • Elasmobranch
  • Intestine
  • Little skate
  • Osmoregulation
  • Urea

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Physiology

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