![]() | |||
![]() |
![]() |
||
Physiological ecology | |||
Aspects of the physiological ecology of shallow-water marine isopods are considered here, while the special physiological challenges that confront semiterrestrial forms are dealt with elsewhere in the ODYSSEY: EVOLUTION TO LAND. | |||
![]() |
|||
|
|||
Osmotic regulation is considered here, while topics of GAS EXCHANGE and BEHAVIOUR are dealt with in their own sections. | |||
Research study 1 |
|||
NOTE1 the first species listed, G. (oregonensis) oregonense is widely distributed along the west coast; S. pentodon is more restricted, initially only in San Francisco Bay, but spreading to other areas NOTE2 in a companion paper to this one the author discusses the taxonomic status at that time of 2 subspecies of G. oregonensis (oregonensis and lutea), but it appears now that the species currently recognised are G. oregonense and G. lutea. NOTE3 seawater (34‰) from Marin County, California = 100%. This is diluted with distilled water to produce salinities of 25-75%, or boiled off to produce 125% |
|||
Research study 2 |
|||
A study on morphological adaptations, and salinity and humidity tolerances, of 5 species of isopods collected around the Pacific Marine Station, Dillon Beach, California and representing a transitional series from marine to terrestrial life, reveals features correlative with the habitats occupied. In general, the more terrestrial isopods are more heavily chitinised than marine forms, are less tolerant of seawater immersion, and resist drying better. NOTE the species include (from marine to terrestrial) Cirolana harfordi, Idotea wosnesenskii, Ligia occidentalis, Alloniscus perconvexus, and Porcellio scaber |
|||
Research study 3 |
|||
NOTE the species overlap in parts of northern California. Prior to a decade ago, L. occidentalis occurred no further north than southern Oregon. Recently, however, it has been found in Howe Sound and on Savary Island, British Columbia NOTE although both species live close to the shore, neither seems inclined to enter seawater for more than brief periods. So it may actually have been more appropriate to measure osmoregulatory abilities of these semiterrestrial forms in their normal medium of air, rather than in water |
|||
Research study 4 |
|||
Sphaeromid isopods Gnorimosphaeroma oregonense are often air exposed but seek out microhabitats with high relative humidities. In experiments using isopods in humidity gradients of 76-100%, researchers in Edmonton, Alberta find that the animals aggregate in high-humidity areas by a “reversal turn” reaction occurring in lower humidity areas. In this behaviour the test animals simply reverse their direction NOTE when this article was written hygroreceptors had not been identified in isopods, and may still not be. The preliminary evidence noted above is that behaviour in a humidity gradient varies in relation to internal osmotic concentrations, suggesting a link between internal osmotic or ionic status and hygroperception Several Gnorimosphaeroma oregonense in |
|||
Research study 5 |
|||
NOTE the exoskeletons on these are notable thin and these appendages are also responsible for most of the gas exchange NOTE 100% salinity is set at 1000mosmol . kg-1
|
|||
![]() |
|||
RETURN TO TOP |