Roger F. Uglow

Heart and scaphognathite activity in the shore crab Carcinus maenas (L.)

Abstract Simultaneous recordings of the activity of the heart and both scaphognathites of Carcinus maenas (L.) were investigated during a wide repertoire of normal activities. The scope of activity for the heart and scaphognathites could usefully be subdivided into three smaller ranges or levels which, although arbitrary, were recognizable on the basis of frequency and arrhythmic phenomena. Alterations of heart and scaphognathite activity induced by a variety of laboratory treatments were investigated in order to evaluate and aid the interpretation of such data for comparative purposes. Providing the recent manipulative history of the animal is known, the behaviours of heart and scaphognathites have been shown to be predictable and useful as sensitive sources of comparative data. The observed behaviour of the heart and scaphognathites has been discussed in terms of their nervous control systems and of their implications in a variable system of blood circulation and gill ventilation.

Aspects of blood physiology and ammonia excretion in Nephrops norvegicus under hypoxia

Abstract 1. 1. Circulating haemocyanin, glucose, lactate, and ammonia concentrations and ammonia excretion rates of Nephrops norvegicus were studied in normoxia and in various hypoxia levels for periods up to 3 weeks. 2. 2. Increases in circulating glucose and lactate took place in oxygen tensions PwO2; = 3. 3. In moderate hypoxia (half saturation), N. norvegiens synthesised haemocyanin; in more severe hypoxia some haemocyanin catabolism occurred. 4. 4. Mean normoxic blood ammonia concentration was 130 μM NH+4/1 with large individual variation. Blood ammonia levels decreased with time in both normoxia and hypoxia showing a lowered metabolic rate (activity level) over the experimental period. In short term experiments, blood ammmonia levels decreased in hypoxia. 5. 5. Mean ammonia excretion rate was O.16μ M NH+4 g/wet wt/hr under normoxia and excretion rate showed a negative, linear relationship to external oxygen tension.

Two methods for the assessment of the oxygen content of small volumes of seawater

Modified micro-Winkler and couloximetric methods are described for the measurement of oxygen in small volumes of water. The former uses a sample size of 1 cm3, while the latter is routinely run with 25-μl samples. Both are accurate, producing results <2% above and 4% below expected values calculated from two previously published sets of tables for the oxygen content of air-saturated seawater. They are also precise assessments, with the se of the micro-Winkler results being 0.23% of the mean of five repeated measurements, while the same figure for the couloximeter is 0.21%. They overcome many of the problems associated with standard methods of measuring oxygen content, such as temperature, salinity and pressure-related effects as well as obviating the need for relatively large quantities of water. Being an essentially inert system the couloximeter may be used for measuring the oxygen content of fluids which pose problems for other methods, such as blood and haemolymph. It is also an absolute method, requiring no calibration. These techniques have been used in the past for measuring oxygen consumption in polar marine invertebrates at temperatures below 0°C and temperate crustacean species.

Determination of trimethylamine in fish by flow injection analysis

Abstract Increased trimethylamine (TMA) levels in tissues are considered to be characteristic of marine fish spoilage. A direct method has been developed for the determination of TMA in aqueous solutions and in fish muscle extracts, which involves the extraction of a small quantity of tissue (1 g) in perchloric acid and the subsequent analysis of the extract by an inexpensive flow injection/gas-diffusion system. Interferences from other volatile amines presentin the extract were suppressed by the use of formaldehyde. The calibration was found to be linear between 0–200 μmole 1 −1 ( r = 0.999) with an R.S.D. of 1.15% ( n = 10) at 50 μmole 1 −1 TMA and a limit of detection of 6 μmole 1 −1 (= 0.53 μ g TMG g −1 of west tissue under these conditions and in this study).

A technique for the measurement of total ammonia in small volumes of seawater and haemolymph

Abstract A rapid and precise technique combining flow-injection analysis and gas-diffusion is described for the measurement of total ammonia (NH3 + NH4 +) in small volumes (100–450 μl) of seawater and diluted haemolymph. Calibration of the method with seawater ammonia standard solutions in the range 1.0–50.0 μmol ammonia l-1 (n=8), and with saline ammonia standard solutions in the range 5.0–50.0 μmol ammonia l-1 (n=6)gave linear calibration curves (r=O.999 in each case) with precision in the range 0.2–3.0%. Precision of measurement of ammoniain samples of seawater and diluted haemolymph was 0.9–3.3% (n=11–13). The lower limit of detection is 0.20 μmol ammonia l-1. Thirty determinations can be made per hour.

Some effects of aerial exposure on the respiratory physiology and blood chemistry of Carcinus maenas (L.) and Liocarcinus puber (L.)

The responses of the crabs, Carcinus maenas (L.) and Liocarcinus puber (L.) to aerial exposure (15 °C) was studied. Both species showed lower MO2 values in air than in water, with the drop being larger (81%) in L. puber than in Carcinus (42%). Lengthy (24 h) aerial exposure produced large increases of circulating lactate in Liocarcinus puber but only a small change in Carcinus. Blood glucose levels were maximal after 4 h exposure but dropped to initial (pre-exposure) values after 24 h exposure. No Carcinus died after 24 h exposure but 77% of the Liocarcinus puber sample died with such treatment. Both species lost body mass and increased haemolymph osmolality during exposure. The findings have been considered in relation to gill structure and resistance of gills to collapse in air.

On a technique for monitoring heart and scaphognathite activity in natantia

A modified impedance technique for monitoring heart and scaphognathite activity of crustaceans has been described. Examples are given of recordings of cardiac and ventilatory activity of Crangon crangon (L.), during a variety of its normal activities. The advantage of the technique in studies of small (≈ 0.3–0.4 g) crustaceans is discussed.

Effects of hypoxia on osmotic and ionic regulation in the brown shrimp Crangon crangon (L.) from brackish water

When exposed to hypoxia (PwO2, <Pcr) and low salinity conditions, the shrimp, Crangon crangon (L.) shows a progressive loss of blood chloride until a new, stable value, still higher than that of the medium, is reached. Simultaneously, circulating levels of calcium progressively increase. Under identical experimental conditions, circulating levels of sodium and magnesium and the blood total osmolarity (Δ °C) are unchanged. The possible explanations for such changes are considered along with their adaptive significance.

Ventilatory behaviour and chloride regulation in relation to oxygen tension in the shrimp Palaemon adspersus Rathke maintained in hypotonic medium

Abstract When exposed to gradually lowered PwO2 values, the brackish water shrimp Palaemon adspersus Rathke responds with an increased ventilation rate with maximum around PwO2 70–80 mm Hg below which the rate is rapidly lowered. Heart rate shows a steady decline with oxygen tensions. When PwO2 levels are subsequently increased again, ventilation rate shows a linear increase, but with a clear overshoot effect at PwO2 over 100 mm Hg. P. adspersus haemolymph has in normoxic condition a Cl− value of 408 mM · 1−1 (medium 250–275 mM · 1−1). The chloride of the haemolymph decreased when PwO2 was lowered below ca. 100 mm Hg. At PwO2 80 mm Hg (ca. Pcr) the haemolymph Cl− begins to show a steady decrease to a new, lower and stable value. At still lower tensions haemolymph Cl− decreased more rapidly and after 1–1.5 h Cl− reached isochlorinity in PwO2 25 mm Hg and less. This phenomenon is considered a re-allocation of energy from ion transport to other vital processes with the consequence of a gradual decrease in ha...

Size, temperature, and scaphognathite frequency-dependent variations of ventilation volumes in Carcinus maenas (L.)

Abstract There is a direct, linear relationship between scaphognathie beat frequency and absolute ventilation volume in Carcinus maenas (L). The absolute ventilation volume is directly proportional to the size of the animals. At all scaphognathie frequencies small animals have a greater relative ventilation volume than large animals. The absolute stroke volume (ml/beat) is greater in large animals than in small animals. The majority of the available evidence suggests that, whilst the force of the scaphognathie stroke may be variable, the amplitude of its excursion remains constant at all beat frequencies.