Journal Article•
Sodium regulation in the freshwater mollusc Limnaea stagnalis (L.) (Gastropoda: Pulmonata).
01 Aug 1970-The Journal of Experimental Biology (The Company of Biologists Ltd)-Vol. 53, Iss: 1, pp 147-163
TL;DR: Limnaea stagnalis has a sodium uptake mechanism with a high affinity for sodium ions, near maximum influx occurring in external sodium concentrations of 1.5-2 mM-Na/l and half maximum influx at 0.25 mM/l, and an experimentally induced reduction of blood volume increases sodium uptake to three times the normal level.
Abstract: 1. Sodium regulation in normal, sodium-depleted and blood-depleted snails has been investigated. 2. Limnaea stagnalis has a sodium uptake mechanism with a high affinity for sodium ions, near maximum influx occurring in external sodium concentrations of 1.5-2 mM-Na/l and half maximum influx at 0.25 mM-Na/l. 3. L. stagnalis can maintain sodium balance in media containing 0.025 mM-Na/l. Adaptation to this concentration is achieved mainly by an increased rate of sodium uptake and a fall of 37 % in blood sodium concentration, but also by a reduction of the sodium loss rate and a decrease in blood volume. 4. A loss of 23% of total body sodium is necessary to stimulate increased sodium uptake. This loss causes near maximal stimulation of the sodium uptake mechanism. 5. An experimentally induced reduction of blood volume in L. stagnalis increases sodium uptake to three times the normal level. 6. About 40% of sodium influx from artificial tap water containing 0.35 mM-Na/l into normal snails is due to an exchange component. Similar exchange components of sodium influx were also observed in sodium-depleted and blood-depleted snails in the same external sodium concentration.
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TL;DR: The fate of molluscan mucus is largely unknown and probably makes a considerable contribution to POM in inshore waters, although its is readily degradable by marine microbes.
Abstract: Mucus functions in many invertebrate physiological processes and also influences structuring of the community and the ecosystem. Molluscan mucus is mostly water. The remaining components are protein, carbohydrate and lipid. The detailed structure of the protein–polysaccharide acidic glycosaminoglycan component is not yet known. Mucus is probably released in dehydrated form in distinct, membrane-bound packages, which then absorb water. A functioning mucus is probably formed by mixing of mucins from different types of gland. Under small deformities, hydrated mucus is a viscoelastic solid, able to function as a rope. As stress increases, it yields to become a liquid which can return to the solid state once the stress is released. It is these properties that allow locomotion by molluscs on what is seemingly an adhesive. On dehydration, the strength and stiffness of mucus increase such that molluscs can suspend their body by a thread of it. Mucus production has been studied quantitatively by various methods, some gravimetric and some colorimentric using pedal, faecal, pseudofaecal and hypobranchial mucus: there is much spatial and temporal variation. In locomotion mucus is a coupling agent between foot and substratum; a medium in which propulsive cilia beat; and a drogue. Mucus deposited as a trail by gastropods is an important facet of their environment. Many species follow mucus trails possibly contributing to the observed patchy distributions of gastropods. The methods by which the presence and polarity of mucus trails are detected is poorly understood. Mucus plays a vital role in feeding. In filter-feeding bivalves, mucus aids the transport of food from gill to mouth and is employed to cleanse the mantle cavity of particles rejected by the labial palps. In gastropods mucus nets and bags are used to trap food prior to ingestion and some groups roll their prey in mucus to prevent its escape. Pedal mucus may be ingested after it has become studded with organic material and perhaps act as a fertilizer for microbial growth. A copious secretion of epithelial mucus is used to isolate molluscs from their environment and mucus may also serve as an ionoregulator. Mucus may also contain specific products to render the animal poisonous, distasteful or irritating. Agglutinin and lysozyme have been found in mucus from marine molluscs. Mucus secretion can present a considerable drain of energy (up to 70% of consumed energy). The fate of molluscan mucus is largely unknown and probably makes a considerable contribution to POM in inshore waters, although its is readily degradable by marine microbes. Given the persistence of mucus, densities of benthic gastropods and their motility patterns, much of the gastropod-inhabited benthos is likely to be covered for most of the time with a layer of pedal mucus.
180 citations
TL;DR: The authors used the chemistry of lakes from the Eastern Rift of Africa as an analogue to the Plio-Pleistocene Lake Turkana and showed that the earliest lake phase was very fresh and continued until the end of the Kubi Algi Formation.
93 citations
TL;DR: The Antarctic nematode Panagrolaimus davidi has a variety of mechanisms that ensure its survival in its harsh terrestrial Antarctic habitat, including freezing tolerance and cryoprotective dehydration.
Abstract: The relative importance of freezing tolerance and cryoprotective dehydration in the Antarctic nematode Panagrolaimus davidi has been investigated. If nucleation of the medium is initiated at a high subzero temperature (-1°C), the nematodes do not freeze but dehydrate. This effect occurs in deionised water, indicating that the loss of water is driven by the difference in vapour pressure of ice and supercooled water at the same temperature. If the nematodes are held above their nucleation temperature for a sufficient time, or are cooled slowly, enough water is lost to prevent freezing (cryoprotective dehydration). However, if the medium is nucleated at lower temperatures or if the sample is cooled at a faster cooling rate, the nematodes freeze and can survive intracellular ice formation. P. davidi thus has a variety of mechanisms that ensure its survival in its harsh terrestrial Antarctic habitat.
88 citations
Cites methods from "Sodium regulation in the freshwater..."
...Nematodes were separated from cultures by allowing them to migrate through tissue paper (Hooper, 1986), washed several times in tapwater and then into an artificial tapwater (ATW; Greenaway, 1970), before storage at 5°C until use (on the same day)....
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87 citations
TL;DR: It is found that acute exposure to low environmental calcium has a highly significant effect on locomotion and respiration, which may have consequences for snail fitness when no morphological effects are apparent.
Abstract: SUMMARY Environmental calcium is a major factor affecting the distribution of freshwater gastropods. Whilst the effects on growth and morphology are fairly well understood, little is known about how calcium availability affects other aspects of gastropod biology. Lymnaea stagnalis (L.) is considered a calciphile and exhibits reduced growth and survival in environments containing less than 20 mg l −1 Ca 2+ . Many freshwater systems exhibit fluctuations in calcium concentration over time: where calcium levels are normally high there may be periods of low [Ca 2+ ], for example following periods of flooding. Here we examined the effects of acute periods of low (20 mg l −1 ) environmental calcium on the physiology and behaviour of L. stagnalis , specifically measuring how locomotion and respiration differ between high calcium (80 mg l −1 ) and low calcium (20 mg l −1 ) environments. We found that in a low calcium environment crawling speed is reduced, and that this coincides with an increase in cutaneous respiration, indicating that the increased metabolic demands of calcium acquisition at low [Ca 2+ ] reduce the energy available for locomotion. Conversely we found a decrease in aerial respiration in hypoxic conditions in the low calcium relative to the high calcium environment. In conclusion, we found that acute exposure to low environmental calcium has a highly significant effect on locomotion and respiration, which may have consequences for snail fitness when no morphological effects are apparent.
86 citations
References
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Book•
01 Jan 1965
TL;DR: This book is a systematic presentation of material concerning osmoregulation in each of the major phyla of invertebrates and vertebrates and one chapter is devoted to osmotic problems encountered by eggs and embryos of aquatic animals.
Abstract: August Krogh, 242 pp., $1.75, Dover, New York, 1966. Material in this book is presented in a systematic fashion with separate chapters devoted to osmotic regulation in each of the major phyla of invertebrates and vertebrates, and one chapter is devoted to osmotic problems encountered by eggs and embryos of aquatic animals. The scientific name of each animal discussed is given and at least some mention is made of osmoregulation in several hundred genera with some discussed at length. A section perhaps as useful to the teacher of zoology or comparative physiology as any part of the book is the final short chapter dealing with methods. Among others, simple techniques for determination of osmotic concentration and of volume changes are included. The methods presented are ones feasible for use in student laboratories and do not require elaborate equipment. An extensive list of references concludes the volume but, by the author's own admission, it is not a comprehensive list. Since the book was first published in 1939 and has not been altered, no recent references are included. Information is presented in a fashion perhaps too sophisticated to make the book of great use to the beginning science student since the author presupposes some knowledge of biology and chemistry on the part of his reader. However, such an accumulation of material concerning osmoregulation as is presented by Professor Krogh would be difficult, if not impossible to find in any other single volume. For this reason, this book could well occupy a place in the library of any biologist. Barbara Shirley Department of Life Sciences University of Tulsa Tulsa, Oklahoma
614 citations
TL;DR: In this article, the freezing-point of small volumes of aqueous solutions is determined by first freezing the sample and then determining the thawing point, and the method works best with volumes of the order of 10-3 to 10-4 mm3.
Abstract: For purposes of determining the freezing-point of small volumes of aqueous solutions the difficulties of undercooling are avoided by first freezing the sample and then determining the thawing-point. Apparatus and procedure specially designed for simplicity of construction and operation are described. The method works best with volumes of the order of 10-3 to 10-4 mm3 and its accuracy in terms of standard deviation is ?0.003? C for freezing-point depressions of the order of 1 to 2? C.
397 citations
TL;DR: Calculated the minimal energy required for extrusion of sodium from the normal frog's sartorius if sodium entered as fast as potassium, and found that more than the energy available from the metabolism of the resting muscle would be needed.
Abstract: Krogh, in his Croonian Lecture1 before the Royal Society, considered the apparent impermeability of striated muscle to sodium to be due to an active extrusion of sodium ions. Discussing this view, Conway2 calculated the minimal energy required for extrusion of sodium from the normal frog's sartorius if sodium entered as fast as potassium. The result was that more than the energy available from the metabolism of the resting muscle would be needed.
152 citations
TL;DR: A scheme is suggested whereby the external and internal sodium concentrations interact together on the influx to produce a self-regulating system which maintains the animal in sodium balance.
Abstract: 1. The effects of external and internal sodium concentrations on the uptake of sodium ions by the crayfish, Astacus pallipes , has been studied. 2. The normal sodium influx, measured with 24 Na, from O.3 mM /l. NaCl solution is 1.5 µM./10 g. body weight/hr. The rate of loss of sodium to de-ionized water has roughly the same value. 3. Net loss of sodium reduces the external sodium concentration required for sodium balance. The minimum equilibrium concentration is about 0.04 mM./l. NaCl. 4. The relation between the external sodium concentration and the sodium influx is non-linear. The influx has a maximum of about 10 µM./10 g./hr. at an external concentration of approx. 1 mM./l. 5. The 24 Na influx is a true measure of the sodium uptake rate at low external concentrations. At higher concentrations the influx may exceed the uptake rate by some 20%. 6. Net loss of sodium increases the influx by three to five times. Loss of 5-10% of the total internal sodium increases the influx from the normal to the maximum level. A 1% change has a significant effect on the influx. Changes in the internal sodium content reflect changes of the blood sodium concentration. 7. A scheme is suggested whereby the external and internal sodium concentrations interact together on the influx to produce a self-regulating system which maintains the animal in sodium balance.
138 citations