Gloria S. Moreira

Osmoregulation and respiratory metabolism in brazilian Macrobrachium (Decapoda, palaemonidae)

Abstract 1. 1. The effect of salinity (0, 7, 14, 21, 28 and 35‰) on osmoregulatory capability and metabolic rate in adult Macrobrachium acanthurus, M. heterochirus, M. olfersii and M. potiuna , was investigated at 20°C using a microcryoscope and Warburg respirometer. 2. 2. All species are strong hyperosomotic regulators in freshwater or low salinities (0–14‰) while at high salinities (21–35‰), with the exception of M. olfersii , they are hypoconformers; M. olfersii exhibits a fair degree of hypo-osmotic regulatory capability. 3. 3. Isosmotic points decrease in the sequence M. heterochirus > M. acanthurus > M. olfersii > M. potiuna . 4. 4. For M. acanthurus and M. olfersii , the metabolism-salinity curves assume a dome shape with a high peak at 21‰ S, close to the isosmotic point. For M. heterochirus and M. potiuna , metabolic rates tended to decline with salinity increase. 5. 5. These results are discussed in relation to the distribution patterns of the adult shrimps and to physiological modifications occurring during development.

Effect of dietary cellulose on digestion in the prawn Macrobrachium rosenbergii

The effects of dietary cellulose on digestion and absorption in Macrobrachium rosenbergii were studied by inclusion of α-cellulose at the expense of starch into four purified diets. The results showed that increasing α-cellulose reduced the apparent digestibility of both dry matter and protein, but also showed that cellulose itself is digestible, with an apparent digestibility of 80%. Increasing dietary levels of cellulose caused an increase in cellulase levels in the gastric fluid, and a decrease in amylase levels in gastric fluid and hepatopancreas. The activity of cellulase was highest between 60 and 180 min after feeding. Increased levels of dietary cellulose were associated with lowered levels of protein in the gastric fluid, and increased levels of protein in the hepatopancreas. Total reducing sugars in the hepatopancreas and glucose in the hemolymph also increased with higher levels of dietary cellulose. Increasing dietary cellulose caused no increase in volatile fatty acids (VFA) in either the gastric fluid or the hemolymph, or in total lipids in the hepatopancreas. It was concluded that the digestion of cellulose in M. rosenbergii was not due to fermentation by endosymbionts producing volatile fatty acids, but to the presence of cellulase which released glucose that was apparently absorbed into the hemolymph, and therefore, dietary cellulose can be a source of both digestible and metabolizable energy for this organism.

The effect of salinity on respiratory metabolism, survival and moulting in the first zoea of Macrobrachium amazonicum (Heller) (Crustacea, Palaemonidae)

Survival, duration of intermoult cycle and respiratory metabolism were evaluated as a function of salinity (0–35‰; 25° C) in early zoeae of the cinnamon shrimp, Macrobrachium amazonicum. Zoeae are extremely resistant to salinity, mortality occurring only in fresh and sea-water after several days. Moulting occurs in all salinities, longer cycles being recorded in 0 and 35‰ S. The metabolism-salinity curve is broadly U-shaped between 0 and 28‰ S but declines sharply in sea-water. Such physiological responses characterise the early zoeae as strongly euryhaline and typically estuarine. Data are discussed in relation to the degree of adaptation of the organism to the freshwater biotope and the position of the species within the generic pattern of adaptive radiation.

Comparative size, biomass, elemental composition (C, N, H), and energy concentration of caridean shrimp eggs

Summary In the evolution of decapod crustaceans, interspecific variation in egg size is considered as an important life-history trait that is linked with the duration of embryonic and larval development, the number and type of larval stages, and with juvenile size. Aiming to provide a quantitative characterization of reproductive traits in related decapod taxa differing in lifestyle (freshwater, estuarine, marine) and geographic-climatic distribution (tropical-temperate), we compared size, biomass, and elemental composition of eggs of caridean shrimps from three families: seven species of Palaemonidae (three congeners of Macrobrachium: M. olfersii, M. carcinus, M. acanthurus; four species of Palaemon: P. northropi, P. pandaliformis, P. elegans, P. adspersus), two Atyidae (Potimirim potimirim, Atya scabra), and one Pandalid (Pandalus montagui). Egg size was measured as larger and smaller diameter (D1 D2), volume was calculated from D1 and D2, and biomass was measured as dry mass (W), carbon (C), nitrogen (N), hydrogen (H), and energy (E, estimated from C) contents. The smallest size and lowest biomass were found in the eggs of two freshwater atyids (both originating from Brazil); the largest size occurred in a marine species, P. montagui (from the North Sea); and intermediate values in freshwater, estuarine, and marine palaemonid species (from Brazil and the Baltic Sea, respectively). Among the Palaemon species, the most limnic (P. pandaliformis) showed a significantly larger egg size and volume (P<0.001) than the estuarine and marine congeners, P. elegans, P. adspersus and P. northropi. This suggests that the generally postulated relationship between egg size and lifestyle (freshwater vs. estuarine or marine) may appear at a generic but not at the family level. On the other hand, individual biomass (in μg or Joules per egg) of early eggs was significantly higher in P. elegans and P. adspersus, indicating interspecific variability in biomass and energy concentration (in μg or Joules per unit volume, mm3). Generally lower biomass concentrations in early eggs of freshwater shrimps may be caused by a higher average water content. Eggs in late embryonic stages were generally larger than earlier eggs of the same species, reflecting an increase in the water content, while an increasing D1:D2 quotient indicated an increasingly elongated egg shape. The biomass per egg decreased during embryonic development due to metabolic degradation of organic reserves. As a consequence of inverse ontogenetic changes in size and organic biomass of developing eggs, the mass-specific biomass values (C, N, H in percent of W; E in Joules per mg W) and volume-specific concentrations (μg or Joules per unit volume) decreased. This change was consistently stronger in the C, H, and E contents than in other measures of biomass (W, N). In consequence, the C:N mass ratio also decreased, suggesting that lipid degradation rather than protein utilization was the principal fuel for embryonic development. Our results indicate high intra- (mainly developmental) and interspecific variation in reproductive traits of closely related species. While volume-specific biomass and energy concentrations of early eggs appear to be associated with variation in habitat salinity (freshwater, brackish, marine), individual egg size and biomass may be related more with the climatic-geographic distribution (temperate, tropical) of different taxa.

RESPIRATORY METABOLISM OF MACROBRACHIUM OLFERSII (WIEGMANN) ZOEAE DURING THE MOULTING CYCLE FROM ECLOSION TO FIRST ECDYSIS

The respiratory metabolism of first stage Macrobrachium olfersii (Wiegmann) zoeae was measured at 12 hr intervals with Cartesian diver microrespirometers throughout the 120 hr period from eclosion to first ecdysis. Weight-specific oxygen consumption rates, although slightly higher immediately after hatching, remained constant and did not differ significantly during the first moulting cycle. Larval dry weight decreased from 21.8 to 18.9 µg during this period. There was no evidence of a diurnal metabolic pattern. The moulting cycle was subdivided according to morphological characteristics, based on the degree of cytoplasmic homogeneity, epidermal retraction, and stage of setal development in the telson. Larval metabolism is suggested to be uniform throughout the eclosion—first ecdysis period, in spite of a distinct and divisible moulting cycle.

The effect of salinity on respiratory metabolism in selected ontogenetic stages of the freshwater shrimp Macrobrachium olfersii (Decapoda, palaemonidae)

Abstract 1. 1. The effect of acute salinity exposure (0, 7, 14, 21, 28 and 35%.S) on the respiratory metabolism of selected ontogenetic stages (zoeae, postlarvae and adults) of the freshwater shrimp Macrobrachium olfersiiwas examined. 2. 2. Metabolic rates are salinity independent from 14 to 28%. S in zoeae 1–4, but tend to increase with increasing salinity in zoeae 5 and 8. Postlarvae exhibit maximal rates in midrange salinities while in adult shrimps, oxygen consumption rates decrease with salinity increase. 3. 3. Salinity has little effect on the metabolism-weight relationship, regression analysis indicating that b varies from 0.69 in 0%. S to 0.62 in 35%. S. 4. 4. Data are discussed as to whether larval responses reflect adaptation to the adult biotope and whether development of the larval neurosecretory system might affect metabolic response to salinity exposure.

Specific dynamic action and the metabolism of the brachyuran land crabs Ocypode quadrata (Fabricius, 1787), Goniopsis cruentata (Latreille, 1803) and Cardisoma guanhumi Latreille, 1825

Oxygen uptake (MO2) was measured in the terrestrial crabs Ocypode quadrata (Fabricius, 1787), Goniopsis cruentata (Latreille, 1803) and Cardisoma guanhumi Latreille, 1825 as a function of digestive state to determine the magnitude and time course of specific dynamic action (SDA). Following 5 days of feeding ad libitum on fish flesh, “steady-state” MO2 was about 2.8, 1.0 and 1.6 μm·g−1·h−1 in Ocypode(29–31 °C), Goniopsis (23–25°C) and Cardisoma (29–31 °C), respectively. After 5 days of fasting, “steady-state” MO2 was decreased greatly to 1.0 and 0.5 μm·g−1·h−1 in Ocypode and Cardisoma, respectively, but was not significantly changed from feeding values in Goniopsis. Time-course experiments indicated that the peak in MO2 following a single large meal occurred within 8 h in both Ocypode and Cardisoma. The apparent SDA persisted for longer than 50 h in Cardisoma, but less than 42 h in Ocypode. These data show that an apparent SDA of large magnitude and variable time course can occur in land crabs. However, the absence of any apparent SDA effect in Goniopsis indicates that it is not a necessary accompaniment to feeding in all terrestrial brachyurans, and must be verified on a species-by-species basis.

The effect of salinity on the metabolic rates of some palaemonid shrimp larvae

Abstract The effect of salinity on the metabolic rates (QO 2 ) of the first zoeal stages of the palaemonid shrimps Macrobrachium acanthurus, M. carcinus, M. heterochirus, M. olfersii and Palaemon northropi was measured at 20°C, using Cartesian diver microrespirometers. Salinities of 0, 7, 14, 21, 28 and 35‰ were used for the species of Macrobrachium , 0‰ being excluded for P. northropi . The metabolic rate-salinity (M-S) response curves for M. acanthurus and M. olfersii zoeae I are both broadly U-shaped, showing a marked elevation of the freshwater end of the curve. Macrobrachium acanthurus zoeae have higher metabolic rates than M. olfersii zoeae in all salinities and show a higher range of M-S independence (14–35‰, cf., 7–28‰). Macrobrachium heterochirus and M. carcinus zoeae I exhibit inverted U-shaped M-S curves between 0–35 and 7–35‰, respectively. The metabolic rate of P. northropi zoea I appears to increase with decreasing salinity, reaching a maximum at 14‰ S. These results are discussed in relation to the general distribution patterns of the adult shrimps.

Temperature and salinity effects on the respiratory metabolism of the first zoeal stage of Macrobrachium holthuisi Genofre & Lobão (decapoda: Palaemonidae)

Abstract Oxygen consumption rates of stage I Macrobrachium holthuisi Genofre & Lobao zoeae were measured in 24 different temperature and salinity combinations using Cartesian diver microrespirometers. Metabolic rates varied little with salinity at 15°C while at 20°C a marked elevation occurred in 0 and 35‰ At 25°C, a slight elevation occurred in 0‰; rates remained constant, however, in the other salinities. At 30°C, respiratory rates were similar to those recorded at 25°C except for decreases at 0 and 28‰ salinity. Q 10 values in the different salinities were usually highest between 15 and 20°C. Statistical analyses showed that while both temperature, salinity and their interaction significantly influenced larval respiratory rates, temperature had the more pronouced effect. Larval metabolism is salinity independent over the salinity range encountered in the larval biotope (7–21‰) at temperatures of 15–30°C.

Metabolic-temperature responses of the copepod Euterpina acutifrons (dana) from Brazil☆

Abstract 1. 1. Thermal metabolic acclimation patterns have been determined for cold- and warm-acclimated male and female Euterpina acutifrons from Sao Sebastiao, Sao Paulo, Brazil, although only one of the dimorphic males, the “small” one, was used in these experiments. The copepods were acclimated to 15 or 25°C and metabolic measurements were made at these temperatures. 2. 2. Females showed less acclimation to cold temperatures than did small males. 3. 3. A comparison of results of this study with similar studies on populations of E. acutifrons from the east coast of the United States suggest that physiological races have evolved.