W. Dall

Changes in lipid and protein during starvation and the moulting cycle in the tiger prawn, Penaeus esculentus Haswell

Abstract Tiger prawns, Penaeus esculentus Haswell (mean wt 20.8 ± 0.3 g, range 13.9–27.7 g) contained 1–2% extractable lipid, 13% protein (biuret method) and 71–74% water (wet wt). In 21 days, the weight of fed prawns increased by 3% and that of starved prawns decreased by 4.4%. Protein was the major energy source during 14 days of starvation, with a loss of 550 mg of total protein compared with a loss of 84 mg of total lipid. The absolute amount of water present remained constant. Of three different tissue compartments, abdomen, cephalothorax, and digestive gland, the abdomen contributed the most protein (330 mg) and lipid (35 mg) during 14 days of starvation. Digestive gland, although containing the largest percentage wet wt of lipid, accounted for only 8.3% of the total lipid in the prawn, and contributed only 18 mg of lipid in 14 days of starvation. Lipid concentration in the digestive gland increased during early premoult (stage D 4 ) and dropped in late premoult (stage D 4 ). Resting oxygen consumption rate remained constant at ≈0.1 ml · g −1 · h −1 at 25°C during 21 days of starvation.

Osmoregulatory ability and juvenile habitat preference in some penaeid prawns

Abstract An investigation was made of the osmoregulation, over a salinity (S) range 3–50‰, of early juvenile and adult penaeid prawns, whose nursery-ground preferences range from rivers of widely fluctuating salinity (banana prawn Penaeus merguiensis de Man; greasyback prawn Metapenaeus bennettae Racek & Dall) through open estuaries with very occasional low salinities (tiger prawn Penaeus esculentus Haswell) to open bays and lower estuaries with fairly stable high salinities (king prawn, P. plebejus Hesse). Adult banana prawns osmoregulated well between S 15–40‰ with isosmotic point ≈ S 27‰, but could not adapt below S 7 ‰, whereas adult greasyback prawns osmoregulated extensively from S 3–50 ‰ with isosmotic point ≈ S 23 ‰. Adult tiger and king prawns had limited osmoregulatory abilities with isosmotic points ≈ S 30 ‰ and lower lethal limits of ≈ S 10 and 7‰, respectively. Early juveniles of all four species were, however, all highly efficient osmoregulators and the curves of the three Penaeus spp. were almost identical below their isosmotic points, which were appreciably lower than those of the adults. Lower lethal limits were S 3‰ or below. It is concluded that nursery-ground selection by the species is unlikely to be determined by osmoregulatory ability. Possible factors determining nursery-ground selection are discussed.

Estimation of routine metabolic rate in a penaeid prawn, Penaeus esculentus Haswell

Abstract Metabolic rates in the juvenile tiger prawn, Penaeus esculentus Haswell were related to decreasing oxygen tensions, 24-h activity, size, temperature and the moulting cycle, using automated, microprocessorcontrolled apparatus. Routine metabolic rate was redefined as the mean 24-h rate, with the animal behaving as it would naturally. While resting, the prawn was oxygen-independent down to ≈25% saturation, but when swimming was oxygen-dependent almost up to full saturation. Oxygen consumption at night was markedly higher than by day, so that for comparative purposes measurements had to be made over at least 24 h. Metabolic rate during the moulting cycle did not change until late premoult, when it increased by 55% 3 days prior to ecdysis and fell to previous levels 1 day afterwards. Using red light, a red-sensitive camera and time-lapse video recorder, metabolic rates were related to nocturnal levels of activity, and these in turn to natural 24-h behaviour. Mean routine metabolic rate, as redefined, was estimated as 8–12% above the resting rate. There was a log-log relationship between metabolic rate and temperature, so that on a In metabolic rate/ln size plot, the displacement due to temperature was linear. Equations were derived relating whole animal metabolic rate, or weight-specific metabolic rate to size, temperature and 24-h normal activity.

Lipid absorption and utilization in the Norwegian lobster, Nephrops norvegicus (L.)

Abstract The role of the digestive (mid-gut) gland in absorption, distribution, and utilization of lipids was investigated in Norwegian lobsters, Nephrops norvegicus (L.) during summer. Glycerol tri[1- 14 C]palmitate was incorporated into food pellets and the subsequent distribution of label followed throughout the body. Digestion and absorption from the foregut was completed 8–12 h after ingestion, but label began leaving the digestive gland after only 4 h and became distributed in tissues and organs in direct proportion to their lipid content, there being no evidence that lipid was accumulated in the digestive gland in preference to other tissues. 75% of the lipid ingested appeared to have been oxidized within 24 h of feeding. Analysis of organs and tissues showed that the digestive gland was the only potential fat depot in males (lipids 8.89 ± 1.36% of body wet wt), the levels in the rest of the body being only ≈ 1% wet wt). No significant decrease in any lipid concentrations occurred during 18 days starvation of males or 35 days starvation of females, but in males the non-lipid dry matter decreased 6% of the total wet wt (other solids were not measured in the females). It was concluded that this was due mainly to loss of muscle protein and it is suggested that the large abdominal muscle mass of macrurous Reptantia, used principally for emergency escape swimming, could provide a reserve that may be partly metabolized without serious detriment to the animal. The concept that the decapod digestive gland has a key role in general lipid metabolism is critically reviewed. In many Decapoda, digestive gland lipid could provide for only a short period of total starvation, but the lipid may have a principal role in the moulting cycle, with perhaps a secondary function in oogenesis.

Ionic regulation of four species of penaeid prawn

Abstract The regulation of sodium, potassium, calcium, magnesium, chloride, and sulphate in adults of the Australian penaeid prawns, Penaeus plebejus Hesse (king prawn), P. esculentus Haswell (tiger prawn), P. merguiensis de Man (banana prawn), and Metapenaeus bennettae Racek & Dall (greasyback prawn) was investigated over the salinity range ( S ) 10–50‰. Results for chloride, sodium, total anions, and total cations showed that the king prawn was overall a poor regulator; the tiger prawn was a poor regulator at lower salinities but showed evidence of ability to regulate above S 45‰; the banana prawn regulated well between S 15–40‰; the greasyback prawn regulated efficiently throughout the range tested. This order of regulatory ability was reflected in the other ions. Potassium levels were regulated to some extent in all species, with a tendency towards accumulation. Calcium was accumulated in all species, while magnesium levels were strongly reduced at low salinities, but in the tiger and banana prawn there was a sharp peak at ≈ S 40‰ which returned to previous levels at higher salinities. In the banana prawn there was a depression in sodium levels of almost the same magnitude as this peak. It is suggested that ≈ S 40‰ represents a zone of ionic instability, corresponding to the transition from high rainfall coastlines, where inshore salinities rarely exceed normal, to arid coastlines where inshore salinities rarely fall below S 36‰. The complex nature of the penaeid antennal gland bladder is briefly discussed in relation to these changes. Sulphate was maintained at very low levels at lower salinities, but paralleled the iso-ionic line at higher salinities.

Blood protein, blood volume and extracellular space relationships in two Penaeus spp. (decapoda: crustacea)

Abstract The blood volume and extracellular space in two species of penaeid prawn were investigated using five different radioisotope labelled tracers and by the analysis of haemocyanin copper. Haemocyanin copper analysis gave a measure of the actual blood volume while the tracers gave estimates of extracellular fluid space, [ 14 C]thiocyanate giving the largest estimate. Different tracers gave different estimates of blood volume and this has been related to the molecular weight of the tracer. The results support the concept that the extracellular space in decapod Crustacea consists of at least two functionally separate compart- ments. The total amount of protein in the blood of well-fed Penaeus esculentus Haswell did not vary significantly throughout the moulting cycle. Protein concentration decreased significantly immediately after moulting and increased to a maximum prior to moulting again. These changes were mainly due to blood volume changes. With starvation the total amount of blood protein decreased with time but with a concomitant increase in blood volume so that there was a far greater decrease in blood protein concen- tration. A linear relationship has been found between the reciprocal of blood volume (ml · 100 g animal −1 ) and the blood protein concentration in P. esculentus and P. plebejus Hess. With the construction of an appropriate calibration curve, this relationship may be used to predict the blood or extracellular fluid volume from the blood protein concentration. Previous work with other Decapoda has been discussed with particular reference to the role of changes in blood volume on reported variations in blood protein concentration.

Osmotic and ionic regulation in the western rock lobster Panulirus longipes (Milne-Edwards)☆

The western rock lobster, Panulirus longipes (Milne-Edwards) is poikilosmotic over its tolerated salinity range, 25–45 ‰. Blood sodium is accumulated while chloride concentration is reduced. Sodium and chloride vary directly with the external salinity, although maintaining their differences in the same proportions as at normal salinity (36.0 ‰). Calcium is accumulated, ranging from over 150% at salinity 20 ‰ to about 117% at salinity 45 ‰. Potassium concentration is equivalent to the external at normal salinity, but is increased with lowered and decreased with raised salinity. Magnesium is reduced to about one-third that of the external concentration over the salinity range 20–40 ‰, but regulation begins to break down at 45 ‰. Individual ions exhibit, therefore, a range of regulation types, from poikilosmotic to homoiosmotic. Equilibrium for sodium, chloride, and calcium is attained in 10 h at salinities of 25, 30, 40 and 45 ‰ respectively. Rate constants for this exchange are linearly related to salinity differential, and rapid osmotic adjustment is by high permeability, equal in both directions, probably mainly via the gills. Muscle appears to act as a salt pool for sodium, chloride, and potassium but not for magnesium and calcium. Salt-loading causes a slight salt diuresis, the salts being excreted, probably via the gills. Except for calcium, there is no excretion of salt into the gut, but there is evidence of an exchange of chloride with another anion. Magnesium excretion is slow, and in the absence of osmotic stress possibly occurs via the antennal glands. All the ions examined appear to be regulated independently.

Water uptake at ecdysis in the western rock lobster

Water ingestion at ecdysis by the western rock lobster. Panulirus longipes (Milne Edwards) was investigated using the reference markers 51Cr-EDTA and 58Co-EDTA. Two possible mechanisms controlling water absorption were examined: first, changes in osmolarity of blood and muscle and secondly, the effects of extracts of central nervous system. Water ingestion was 16.071 ± 2.365 ml kg−1 h−1 during swelling just before ecdysis (stage D4(S)) and 23.099 ± 1.238 ml kg−1 h−1 during stage A. There was no significant absorption in the foregut or hindgut and the digestive gland appeared to be the site of major absorption. Total water ingested during stages D4(S) and A was 13.7% of the proecdysis weight. Calculating total water uptake by wet weight differences plus wet weight of exuviae gave a value that was too high and instead weight increases were calculated from a carapace length-weight formula. Allowing for postecdysis increase in weight the net increase at ecdysis was 18.4–21.4% which was 4.7–7.7% more than the water ingested. It was concluded from this that water enters the body at ecdysis both by ingestion and by absorption through the external surface. It is suggested that water ingestion provides the main source of swelling of the cephalothorax in stage D4(S) and after ecdysis both ingested water and external absorption enables the flaccid abdomen and appendages to swell rapidly. Statistically significant differences were found in the concentrations of total cations and chloride in leg muscle during the transition from stage C4 to late D4 but the trends were not consistent and probably have no functional significance. There were no changes in the concentration of osmotically active organic constituents. The freezing-point depression of the blood in stage D4 was significantly higher than that in stage C4(P < 0.02) but the mean difference was only 1.8%. It was concluded that osmoticchanges were unlikely to be an important mechanism of water uptake. Water-soluble extract (WSE) and acetone-soluble extract (ASE) of brains and first ventral ganglia were without significant effect when compared together with controls. There was a barely significant decrease, however, in water in the proventriculus of WSE-treated animals compared with that of controls (P < 0.05). and further investigation on the effects of such extracts on water uptake at ecdysis is warranted.

The rôle of ninhydrin-positive substances in osmoregulatton in the western rock lobster, Panuliris longipes (Milne Edwards)☆

Abstract Free leucine, valine, proline, tyrosine, alanine, taurine, glutamic acid, and glycine are present in both blood and muscle of Panulirus longipes (Milne Edw.). Arginine is present in muscle only. Five unidentified ninhydrin-positive spots appeared in thin-layer chromatograms of blood, and four in chromatograms of muscle. Non-protein, ninhydrin-positive substances (NPS) in muscle do not appear to function in the moulting process. Concentrations averaged 278 mM/kg wet weight of muscle and NPS were the most abundant of organic osmotically active substances (total ions were 325 mM/kg). Trimethylamine oxide and glycine betaine together amounted to a further 121 mM. With lowered salinity, NPS concentrations in muscle were sharply reduced within 24 h, but with increased salinity, concentrations rose slowly over 7 days suggesting that NPS are produced by intracellular processes. When rock lobsters were fully adapted to salinities ranging from 25 to 45‰ concentrations of muscle NPS were linearly related to external salinity. When the salinity was lowered the blood was initially flooded with NPS, concentrations reaching a maximum at 12 h, and returning to normal after 72 h. Gastric fluid concentrations also rose, and evidence indicates that a large part of the NPS lost from muscle is excreted into the external water via the gastric fluid. At a salinity of 30‰, 56 % of the NPS lost from muscle appears in the external water, the remainder being excreted as ammonia; at 27‰, 82 % of NPS was excreted into the water, the remainder as ammonia. It is concluded that a changing external salinity would cause a continual loss of NPS from the body of a decapod crustacean. Although wasteful of nitrogenous compounds, such a process is of high survival value in permitting osmotic adjustment in the absence of more efficient mechanisms, such as those present in teleost fishes.

Measurement of water drinking rates in marine Crustacea

Tests were made of γ-emitting compounds as potential non-absorbed reference markers for estimating water ingestion in the western rock lobster Panulirus longipus cygnus (George) and the penaeid prawn Penaeus latisulcatus (Kishinouye). The extent of any marker absorption into the tissues was measured in animals totally immersed and in rock lobsters with only the gills perfused. Distribution of marker within the body, transport into the gut, and excretion were examined following injection of the label into the blood of the rock lobster. 125I-sodium iothalamate, 58Co-EDTA, and 51Cr-EDTA were all satisfactory reference markers with very low absorption, 51Cr-EDTA being the best. Most injected sodium iothalamate was excreted from the body over 24 h, probably via the urine, which suggests its further use in studies of antennal gland function. 46ScCl3, 51CrCl3, 58CoCl2, and 110AgCl were of some value for estimating drinking in penaeid prawns, although 110AgCl probably gave levels that were too high. 110AgCl was useless for the rock lobster, which absorbed much more marker than was retained in the gut. 125I-rose bengal was not practicable because it slowly precipitated in sea water. Requirements for reference markers appear to be more critical for animals with high permeability to major sea-water ions than those which extensively regulate all major ions.