Osmotic and ionic regulation

This paper represents the results of more than 30 years field observations and research work carried out from the Isefjord Laboratory, Vellerup Vig (Zealand, Denmark), which is owned and financed by the author. The Isefjord complex, 36 km long, including the main fjord and the Roskilde Fjord, and covering about 400 km2, is a shallow (7–10 m, max. 30 m) area dominated by substrata of fine sand to mud with a high content of organic matter. As a guidebook for future research the first part gives information about distribution, systematics, ecology, and breeding of the majority of the 477 animal species described. Nearly 400 species are invertebrates and of the chordates 68 species are true fishes. 63% of all animal species have not previously been recorded from the area, 27 species are new to Danish seas, and one (Polychaeta, Capitellidae) is new to science. The hydrography is treated mainly on the basis of literature. The fjord system may be classified as mixohaline: the Isefjord proper is polyhali...

Systematics and ecology of the Isefjord marine fauna (Denmark) with a survey of the eelgrass (Zostera) vegetation and its communities

Chapter 15 – molting and its control

2 – Molting and Regeneration

The common ragworm Hediste diversicolor inhabits the shallow marine and brackish waters in the North Temperate Zone of the Atlantic. This infaunal species builds U or Y-shaped burrows in the soft sediments. H. diversicolor is gonochoristic and remains atokous throughout its life. Due to the facility of harvesting of individuals by hand and their maintenance, this species represents a good biological material for experimental studies. In consequence, the common ragworm served as a model for endocrine control of reproduction in Polychaeta and played a fundamental role in the study of immune defence in Polychaeta. Life history characteristics (longevity, spawning season, feeding tactics and growth) and population dynamics (sex ratio, density and biomass) vary greatly according to geographical location of the populations. In addition, inter-population morphological, biochemical and physiological differences have been noticed in individuals from different areas and different environmental conditions in the same areas and could be related to the limited dispersal capacity of the species. 
H. diversicolor interacts with its environment. The construction of burrows by individuals increases the sediment–water interface. When they ventilate their burrows, individuals verticalize oxic zones into the sediment and promote microbial and meiofaunal growth alongside their burrows. Moreover, the common ragworm is a species of commercial interest because of its use as bait in recreational fishing and as food in aquaculture. In order to alleviate environmental pressure caused by excessive demand over optimal sustainable yield of bait fisheries, intensive aquaculture has been proposed. The common ragworm could be also used as biomonitor of pollution in estuarine ecosystems.

A review of the biology, ecology and potential use of the common ragworm Hediste diversicolor (O.F. Müller) (Annelida: Polychaeta)

1. The osmotic performance of the small cancroid crab Rhithropanopeus harrisi (Brachyura) has been surveyed in order to assess the mechanisms mainly responsible for its success in colonizing waters of low salinity.2. This crab shows hyper-regulation of chloride and osmotic pressure in media up to about 60-70% sea water, and a slight tendency to hypo-regulate in higher salinities.3. Like other crabs, Rh. harrisi maintains a relatively high blood concentration and produces a blood-isotonic urine.4. Urine production, estimated by an indirect method, approximates 24% of the body weight per day in low salinities, implying a high rate of water turnover.5. Approximately ⅓ of the total salt loss is via the urine.6. Inward permeability to water, as judged by D2O influx rate, is decreased at lower salinities. This mechanism, here demonstrated for the first time in crustaceans, is suggested as being of adaptive significance.7. Urinary output of water exceeds the diffusional net (osmotic) input of water as calculated...

Osmotic regulation and adaptive reduction of water-permeability in a brackish-water crab rhithropanopeus harrisi (brachyura, xanthidae)

1. The apparent water-permeability of Carcinus maenas, as measured by D2O influx, is 2-3 times higher than that of the more euryhaline crab Rhithropanopeus. 2. Like Rhithropanopeus, Carcinus shows a reduction of water-exchange rate at lower salinities. The highest hourly water-exchange fraction is in 75% SW (K = 2.73), the lowest in 30% SW (K = 1.76); values refer to a crab with wet weight of 10 g, at 18° C. 3. The calculated net diffusional (osmotic) water influx is adequate to account for the urine production of Carcinus in 50-70% SW, but does not account for urine production in SW, and only inadequately for the urine produced in 30-40% SW, and it seems necessary to postulate some isotonic transport of water.

The apparent water-permeability of carcinus maenas (crustacea, brachyura, portunidae) as a function of salinity.

1. Removal of both eyestalks causes a shortening of the following intermoults in Cambarus clarkii. The removal of a moult-inhibiting substance produced in the eyestalks is accepted as a reasonable explanation.2. The methods employed have been such as to show: (a) that the processes leading up to moulting can be initiated in the absence of the eyestalks; and (b) that the effect upon moulting is associated with the absence of the eyestalks, not with the shock of their removal.3. Injury other than eyestalk removal does not shorten the intermoult when performed early in the intermoult.4. Eyestalk removal always results in death, but the processes related to viability which are affected by eyestalk removal can be distinguished from the moulting processes which are affected by the same operation, although there is an apparent correlation between moulting and viability.

Studies on the effects of eyestalk removal upon young crayfish (cambarus clarkii girard)

1. Laboratory studies have been made of the level of chloride regulation in Neresis diversicolor from representative parts of its geographical and ecological range. Areas studied include marine-dominated habitats in Scotland and southern England, estuarine habitats in southern England, conditions of low salinity in the Gulf of Finland, and intermediate salinities in the Isefjord, Denmark.2. Animals have been adapted from their environmental salinity to a series of salinities from full sea water or higher down to fresh water, and the chloride level of the coelomic fluid has been determined after full adaptation and feeding at each salinity.3. Results indicate that N. diversicolor as a species shows a uniform pattern and level of chloride regulation regardless of the region in which it is found. The test does not demonstrate physiological races differing in respect to salinity tolerance, although the possibility that other criteria may prove diagnostic of such races is not ruled out.4. It is suggested that ...

Comparison of the level of chloride regulation by nereis diversicolor in different parts of its geographical range

1. The heart of Cancer irroratus has been perfused in situ, the beat recorded mechanically, and the inhibitory and excitatory nerves stimulated while the heart was perfused with various drugs.2. Nervous inhibition of the heart induced by stimulation of the inhibitory nerves is usually total with no inhibitory after-effect.3. Nervous excitation of the heart induced by stimulation of the excitatory nerves frequently shows a stimulatory after-effect.4. The cardio-inhibitory nerves appear to be more effective than the excitatory nerves, but each type of, nerve can modify to some extent the effectiveness of the other.5. The excitatory nerves are effective when stimulated at frequencies ranging from 200-300 per second down to 10 per second or less.6. The inhibitory nerves produce total inhibition when stimulated from 15-20 to 100-200 times per second. At frequencies extending above and below this range, partial inhibition may be obtained.7. Strychnine, in concentrations of 1:2,500, blocks reversibly the action ...

Ralph I. Smith

Papers

Osmotic regulation and adaptive reduction of water-permeability in a brackish-water crab rhithropanopeus harrisi (brachyura, xanthidae)

The apparent water-permeability of carcinus maenas (crustacea, brachyura, portunidae) as a function of salinity.

Studies on the effects of eyestalk removal upon young crayfish (cambarus clarkii girard)

Comparison of the level of chloride regulation by nereis diversicolor in different parts of its geographical range

The action of electrical stimulation and of certain drugs on cardiac nerves of the crab, Cancer irroratus.