Osmoregulation as a Homeostatic Mechanism using the Comparitive Melting-Point Method for two Crab Species.
Osmoregulation as a Homeostatic Mechanism using the Comparitive Melting-Point Method for two Crab Species.
Abstract
Two crab species, Plagusia and Cyclograpsus, were collected from a local estuary in the littoral and deep water zone for osmoregulation studies. To examine differences in osmoregulatory mechanisms among the species, haemolymph of the specimens was extracted once they were acclimated to varying concentrations of seawater. Using the comparative melting-point, capillary tubes were filled with small samples of seawater and blood then frozen and melted in a -15˚C ethanol bath. The melting time of each was observed thereafter. Subject’s time range fell over 17 minutes of which the majority of the most salinated samples melted last and the remaining concentrations melting according to the different data sets. The study revealed the Plagusia crab as the osmoconformer and the Cyclograpsus as the osmoregulator.
Introduction
For an organism to keep its body in a state of equilibrium it makes use of homeostatic mechanisms. These mechanisms are caused by fluctuations in extracellular fluid (Richardson, 2005). They act on a system of negative feedback in order to preserve or re-establish the ideal state. The relevant homeostatic mechanism tested in this investigation is osmoregulation. Osmoregulation is vital for organisms to be able to maintain a constant, ideal osmotic pressure within their body. It is a homeostastic mechanism in which they keep an optimal concentration of solutes and quantity of water in the bodily fluids (Canalon, 2009).
Osmoregulation in crustaceans has been subjected to study by numerous authors (Morris, 2001) (Charmantier et al., 1988) (Thurman, 2003) typically in terrestrial and estuarine species (Bursey, 1976). For crab species living in estuaries, they are exposed to varying levels of salinity. In order to survive this environment, they cope by using one of two major “sub-mechanisms”; osmoregulation and osmoconforming.
Abstract
Two crab species, Plagusia and Cyclograpsus, were collected from a local estuary in the littoral and deep water zone for osmoregulation studies. To examine differences in osmoregulatory mechanisms among the species, haemolymph of the specimens was extracted once they were acclimated to varying concentrations of seawater. Using the comparative melting-point, capillary tubes were filled with small samples of seawater and blood then frozen and melted in a -15˚C ethanol bath. The melting time of each was observed thereafter. Subject’s time range fell over 17 minutes of which the majority of the most salinated samples melted last and the remaining concentrations melting according to the different data sets. The study revealed the Plagusia crab as the osmoconformer and the Cyclograpsus as the osmoregulator.
Introduction
For an organism to keep its body in a state of equilibrium it makes use of homeostatic mechanisms. These mechanisms are caused by fluctuations in extracellular fluid (Richardson, 2005). They act on a system of negative feedback in order to preserve or re-establish the ideal state. The relevant homeostatic mechanism tested in this investigation is osmoregulation. Osmoregulation is vital for organisms to be able to maintain a constant, ideal osmotic pressure within their body. It is a homeostastic mechanism in which they keep an optimal concentration of solutes and quantity of water in the bodily fluids (Canalon, 2009).
Osmoregulation in crustaceans has been subjected to study by numerous authors (Morris, 2001) (Charmantier et al., 1988) (Thurman, 2003) typically in terrestrial and estuarine species (Bursey, 1976). For crab species living in estuaries, they are exposed to varying levels of salinity. In order to survive this environment, they cope by using one of two major “sub-mechanisms”; osmoregulation and osmoconforming.
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