Growth and elemental composition (C,N, H) in Inachus dorsettensis (Decapoda: Majidae) larvae reared in the laboratory

Larvae of the spider crab Inachus dorsettensis were reared in the laboratory at constant 12 °C. Development lasted 8 to 10 d in the Zoea I, 10 to 12 d in the Zoea II and 14 to 20 d in the megalopa stage. During this time, larval growth was measured in samples taken every 2 to 4 d as dry wt (W), carbon (C), nitrogen (N), and hydrogen (H); energy content (E) was calculated from C. Biomass and energy (per individual) increased in each larval stage as a parabola-shaped function of age, which could be fitted by a power equation. C, H, and E show a higher percentage gain (relative to the initial values at hatching) than W or N, suggesting that proportionally more lipid than protein is accumulated during larval development. There are cyclical changes in the relative (per unit of W) biomass and energy figures, corresponding to the larval moult cycles: immediately after each ecdysis all these values decrease, presumably due to rapid uptake of water and minerals, then they increase again due to tissue growth and remain high until the next moulting occurs. Cyclical changes in the C/N ratio suggest that proportionally more lipid than protein is accumulated during the initial (postmoult) phase of the moult cycle, followed by a period of balanced or protein-dominated gain during the intermoult and premoult phases. These patterns of growth and elemental composition observed during the complete larval development and in single moult cycles of I. dorsettensis are compared with those described in the literature for other decapod species. This comparison suggests a high degree of similarity in biochemical composition and growth characteristics of larval decapod crustaceans.     

Effect of the insect growth regulator diflubenzuron (Dimilin®) on the uptake of glucose and N-acetylglucosamine into the cuticle of crab larvae

Incorporation of ³H-labelled glucose and ³H-labelled N-acetylglucosamine (NAGA) — both precursors to chitin —into the cuticle of Rhithropanopeus harrisii (Gould) larvae (Crustacea: Brachyura) has been examined at different stages of the moult cycle in control larvae as well as in larvae treated with the insect growth regulator diflubenzuron (Dimilin^®). As far as the control larvae were concerned, the incorporation of both precursors was high at the postmoult stage when endocuticle was secreted. NAGA appeared to be a more specific precursor of cuticular material than glucose during the premoult stage when exocuticle was produced. Incorporation of both precursors was low immediately before ecdysis and during the intermoult stage when secretion of the cuticle is complete. The results show that incorporation of glucose into chitin was greatly inhibited by the pollutant during the postmoult stage when endocuticle is produced, while incorporation of NAGA was reduced to a lesser extent at this stage. Diflubenzuron treatment markedly affected the incorporation of both NAGA and glucose in the premoult stage during secretion of exocuticle.     

Patterns of larval and early juvenile growth in a semiterrestrial crab, Armases angustipes (Decapoda: Sesarmidae): comparison with a congener with abbreviated development

In a semiterrestrial and estuarine tropical crab, Armases angustipes Dana (Grapsoidea: Sesarmidae), changes in biomass (measured as dry mass, W; carbon, C; nitrogen, N; and hydrogen, H; per individual) and relative elemental composition (C, N, H, in percent of W; C:N mass ratio) were studied during development from an early egg stage through hatching, the complete larval phase, metamorphosis and the first juvenile crab stage (CI). In the megalopa and CI, growth was measured also within the moulting cycle, and biomass and elemental composition were determined in cast exuviae. From an early egg stage to the freshly hatched larva, A. angustipes lost about 20% of W, 29% of C, 5% of N and 32% of H. Proportionally higher losses in C than in N were reflected also in a significantly decreasing C:N mass ratio (from 5.02 to 3.74). These results indicate that lipids mobilised from yolk reserves represented the principal metabolic substrate for embryonic energy production, while proteins were catabolised at a much lower rate. The present data of growth and exuviation are compared with previously published data from a congener, A. miersii Rathbun, which has an abbreviated and facultatively lecithotrophic mode of larval development (with three instead of four zoeal stages; stages I and II in principle independent of food). When growth is measured as an increase in the final (premoult) biomass of successive developmental stages, both species show an exponential pattern. Within the moulting cycles of the megalopa and the first juvenile, both species show parabola-shaped growth curves, with a rapid biomass increase in postmoult and intermoult stages, and losses in the premoult phase. Thus, the two Armases species show, in general, similar patterns of larval and early juvenile growth. However, the initial size of eggs and larvae is about four times larger in A. miersii, and its biomass remains higher throughout the period of larval and early juvenile development. A. angustipes is able to partially make up for this difference, as it has an additional zoeal stage, and its megalopa and CI stages show higher relative biomass increments (in percent of initial values). Due to this compensatory growth pattern, A. angustipes reaches in its CI stage about half the biomass of a juvenile A. miersii. When exuvial losses of megalopae and juveniles are compared between these two species, A. miersii shows higher biomass losses per individual (corresponding with its larger size), but lower relative losses (C, N, H, in percent of late premoult body mass or in percent of previously achieved growth increments). Differences in larval and early juvenile growth and in the exuvial losses of megalopae and juveniles of these two congeners are discussed in relation to their differential ecology, life history and reproductive strategy.     

Endocrine regulation of carbohydrate metabolism during the moult cycle in crustaceans I. Effect of eyestalk removal in Ocypoda platytarsis

The endocrine regulation of carbohydrate metabolism in the decapod Ocypoda platytarsis was investigated by eyestalk ablation at all stages of the moult cycle. Eyestalk removal (and hence removal of a substance probably produced by it) profoundly influences the carbohydrate level of the major storage organ, the hepatopancreas. The changes taking place storage organ, the hepatopancreas. The changes taking place in hepatopancreatic glycogen are reflected in the blood sugar (glycemic) level. The blood-sugar level is also related to dynamic events taking place in the cuticle during the moult cycle. At the intermoult and postmoult stages, the eyestalk factor directs the sugar supply for energy metabolism, and prevents sugar deposition as glycogen in the hepatopancreas. At the premoult stage, the activity of the eyestalk is suppressed by the moulting gland (the Y organ), as eyestalk ablation does not alter the blood-sugar value or the hepatopancreatic glycogen-level. After the increase at the freshmoult stage due to eyestalk ablation, the blood-sugar level tends to re-attain its previous low level at the postmoult stage.     

Copper and zinc handling during the moult cycle of male and female shore crabs Carcinus maenas

Tissue concentrations and contents of copper and zinc were determined at 11 different stages of the moult cycle in male and female shore crabs Carcinus maenas. Metal concentrations in haemolymph, gills, midgut gland, muscle, and exoskeleton of males and haemolymph, gills, and midgut gland of females were determined, as were haemocyanin concentrations and haemolymph volumes (using ¹⁴C-inulin) in males. The changes in tissue Cu and Zn concentrations and contents that occur throughout the moult cycle can be attributed to muscle breakdown in late premoult, the period of starvation in late premoult and early postmoult, the resorption from and shedding of the old exoskeleton, and the dilution of the haemolymph caused by water uptake around the time of ecdysis. The present study demonstrates that whole-body Cu and Zn contents remain constant during a large part of the moult cycle of male and female C. maenas. This state of whole-body trace metal homeostasis is maintained in spite of major changes in tissue proportions and tissue Cu and Zn concentrations and contents. Previous studies have not carried out the necessary analysis to move from theoretical estimates to quantitative determination of the changes in tissue metal distribution associated with moulting in crustaceans; the data presented illustrate the necessity of measuring both tissue concentrations and contents of metals to avoid misinterpretation of either.     

Cadmium accumulation in the female shore crab Carcinus maenas during the moult cycle and ovarian maturation

 The influence of moulting and ovarian maturation on cadmium accumulation in the tissues of female shore crabs Carcinus maenas exposed to 1 mg Cd l⁻¹ in the water was investigated. Cadmium accumulation in all tissues examined was markedly increased in crabs in the postmoult stages (A and B) compared to crabs in all other moult stages. During the moult cycle, average cadmium accumulation in the midgut gland ranged from 29 μg Cd g⁻¹ dw at premoult stage (D₂) to 589 μg Cd g⁻¹ dw at postmoult stage (A). Average cadmium concentrations in the haemolymph ranged from 0.56 μg Cd ml⁻¹ at intermoult stage (C₄) to 4.6 μg Cd ml⁻¹ at postmoult stage (A), while the gills accumulated from 103 μg Cd g⁻¹ dw in intermoult stage (C₃) to 352 μg Cd g⁻¹ dw in postmoult stage (A). Cadmium concentration in gills and haemolymph was also significantly higher in crabs in late premoult stage (D₃) compared to C₄-crabs, while midgut gland cadmium concentration remained elevated in C₁- and C₃- intermoult stages relative to C₄. During ovarian maturation the cadmium accumulation in midgut gland, gills, ovaries and haemolymph decreased. Average cadmium concentration in the midgut gland decreased from 63 μg g⁻¹ dw in ovarian Stage I to 19 μg g⁻¹ dw in ovarian Stage VI. The same pattern was observed for gills, haemolymph and ovaries. The present study demonstrates that cadmium accumulation in the female shore crab strongly depends on the physiological status of the animal. A possible association between physiological calcium requirements and cadmium accumulation during moulting is discussed. Received: 20 January 2000 / Accepted: 20 July 2000     

Energetics,moult cycle and ecdysteroid titers in spider crab (Hyas araneus) larvae starved after the D0 threshold

Zoea I larvae of Hyas araneus L. (Decapoda: Brachyura: Majidae) were dredged in January 1986 from the German Bight and reared in the laboratory at constant 12°C, until they reached the transition of stages C/D₀ of the moult cycle (4 d after hatching). This developmental stage had previously been found to correspond with the point of reserve saturation (PRS) which allows autonomous (food-independent) development through the rest of the moult cycle and hence, was termed the D₀ threshold. One part of the larvae was continually fed (control), another group was starved from the D₀ threshold until moulting to the zoea II instar. In these two experimental groups, as well as in the two groups of zoea II larvae obtained from the different feeding conditions, the course of the moult cycle, biomass (dry weight, W; carbon, C; nitrogen, N; hydrogen, H; energy, E; the latter estimated from C), and ecdysteroid titers (measured with a radio-immuno-assay as ecdysone equivalents) were investigated. When the larvae reached the PRS, they had gained 90% in W, 72% in C, 32% in N, 53% in H, and 65% in E, since hatching, corresponding to an accumulation of 87% of final W and 62 to 69% of C, N, and H reached later, at the end of the mould cycle in the control. The period of starvation caused a 2.5-d delay of the moult cycle, mainly in late premoult, and significant losses of biomass and energy. Starved and fed larvae secreted similar amounts of moulting hormone per individual, but with a reduced rate in the starved group, thus causing developmental delay. Zoea II larvae moulting after starvation contained less than half of the control biomass and energy, and even less than a freshly hatched zoea I. Growth rate was only slightly enhanced in these zoea II larvae as compared to the fed control, but losses of biomass, mainly of lipids, were partly compensated by a 4-d prolongation of their moult cycle, chiefly (3 d) in stage C. Biomass curves were almost parallel in the two experimental groups of zoea II larvae, with significantly higher values in the control during all stages of the moult cycle. However, similar relative proportions (74 to 89%) of late premoult biomass and energy were reached at the D₀ threshold, regardless of different feeding history and initial or final values in a given group. The ecdysteroid titer curve of the zoea II which had moulted from starved zoea I was very similar to that in control larvae, but with a 3-d delay in the occurrence of premoult peak concentration (in both groups in stage D₁). Regulation and coordination of moult cycle, ecdysteroid titers, and growth in the larval development of decapod crustaceans are discussed, with special reference to the D₀ threshold.     

Interactions between haemolymph chemistry and condition in the southern rock lobster, Jasus edwardsii

A haemolymph colour index is developed in an attempt to improve the resolution of serum protein data in the characterisation of temporal and spatial changes in the condition and growth of a wild population of Jasus edwardsii. The index can be used as an indicator of nutritional condition if combined with conventional moult staging techniques. Lobsters and haemolymph samples were collected from two high- and two low-growth sites over two fishing seasons. Haemolymph samples were analysed for serum protein and astaxanthin level and categorised according to colour, that is, "pigment stage" (PS). Moult stage data were collected and abdominal and hepatopancreatic tissue analysed for percent dry weight. Haemolymph colour changes from light blue-grey, through beige, to deep orange during the moult cycle. These changes were explained with reference to the major pigment, astaxanthin, which increased from 0.135 mg/l (ǂ.054, n=38) at PS 1 (early intermoult) to 2.670 mg/l (ǂ.599, n=12) at PS 4.5 (late premoult). There were significant increases in percent abdominal and hepatopancreatic dry tissue weight over the moult cycle (Kruskal-Wallis non-parametric ANOVA, P<0.05), especially during intermoult. Serum protein levels increased concomitantly and were significantly correlated with percent dry weight of both tissues (abdomen: r²=0.78, n=871, P<0.001; hepatopancreas: r²=0.64, n=864, P<0.001) There were also significant differences between sites in both PS-specific serum protein and percent dry tissue. Lobster condition differed significantly between sites, probably as a result of temperature-mediated effects on growth rate. The addition of haemolymph pigment to the serum protein index allows the differentiation of lobsters at the beginning, middle and end of intermoult.     

Larval growth in the estuarine crab Chasmagnathus granulata: the importance of salinity experienced during embryonic development, and the initial larval biomass

The importance of salinity experienced during embryonic development and initial larval biomass on larval growth was studied in the South American estuarine crab Chasmagnathus granulata. Ovigerous females were maintained at three salinities (15, 20, and 32‰) from egg laying to hatching of zoea l. Larvae from all treatments were reared under constant conditions of photoperiod (12∶12), temperature (18°C), and salinity (first instar at 20‰, subsequent instars at 32‰). Biomass was measured as dry weight, carbon, and nitrogen content per individual at egg laying, hatching of zoea l, premoult zoea l, and zoea 4, and in 8-day-old megalopa. From hatching to premoult zoea 4, biomass was higher for larvae from prehatching salinities of 15 and 32‰. There was a significant positive correlation between biomass at hatching and at premoult zoea l and zoea 4. Accumulated biomass during zoeal stages tended to be higher for larvae from broods with higher biomass at hatching, although this trend was not always significant. Zoea 4 either directly metamorphosed to megalopa or moulted to zoea 5, following, respectively, a short or long developmental pathway. The proportion of zoea 4 that followed the long pathway was negatively correlated with biomass of zoeal stages. Biomass at hatching was correlated with biomass of megalopae developed through the short pathway, although it was not correlated with the accumulated biomass at this stage. Megalopae developed through the long pathway (i.e. metamorphosed from zoeae 5) had higher biomass than those from the short pathway. The present results suggest that prehatching salinity and initial egg and larval biomass can be very important for larval growth. Published online: 9 August 2002     

Ovarian development and spawning in relation to the moult cycle in Northern krill, Meganyctiphanes norvegica (Crustacea: Euphausiacea), along a climatic gradient

Adaptive processes linked to reproduction were studied comparatively for three populations of Northern krill, Meganyctiphanes norvegica (M. Sars, 1857), sampled during winter and summer cruises in the Clyde Sea (W Scotland), the Kattegat (E Denmark), and the Ligurian Sea (NW Mediterranean). The aim was to investigate the functional relationship between egg production and moulting under contrasted climatic and environmental conditions. A staging system for female sexual development established for live krill was complemented by a histological study of the ovary at various developmental steps. During the reproductive season, all adult female krill were engaged in cyclical egg production. During experiments, female krill released one batch of mature oocytes in one or two spawning events. The ovary of postspawn female krill still contained developing oocytes for another egg batch. In the non-reproductive period, all female krill had a resting ovary. Ovarian structure and pattern of egg production were identical in the three populations, but seasonal timing of egg production was different. The model proposed for the Ligurian population of the annual cycle of ovarian development can be extended to the other two populations, taking into account the seasonal characteristics of each site. Random field samples were staged simultaneously for moult cycle and for sexual development. Moult stages and the seasonal variation of the intermoult period were studied for the Kattegat population using multi-year data and compared to data obtained during summer/winter cruises in the Clyde and the Ligurian Sea. At the three sites, intermoult period was shorter and temperature-dependent during the reproductive period, concurrent with the season of greatest food availability. During most of the year and the period of sexual rest, moulting activity was reduced. The relationship between spawning and the moult cycle was studied comparatively for the three populations. Eggs were released during the premoult phase of a “spawning moult cycle”, in one or two spawnings associated with apolysis and Moult Stage D1, respectively. Yolk accumulation for the next egg batch was completed during an alternating “vitellogenic moult cycle”. A model for the timing of cyclical egg production in relation to moulting, as proposed for the Kattegat, can be extended to the other populations, taking into account intermoult period variation with temperature. Temperature appeared to be the principal environmental factor controlling growth (through moulting) and egg production during the reproductive season, in connection with favourable trophic conditions. Received: 22 December 1997 / Accepted: 29 August 1998     

Haemocyanin concentration of juvenile lobsters (Homarus gammarus) in relation to moulting cycle and feeding conditions

Groups of laboratory-reared, juvenile lobsters (Homarus gammarus, 40–50 g wet weight) were given different types of food (shrimp, mixed invertebrates and pellets, bivalves, starved) for a period of 22 wk. Haemocyanin concentration was measured weekly, moult stage and moultings noted. Haemocyanin concentration decreased rapidly in the starved group (from 0.8–0.6 to 0.2 mM). The group fed with bivalves showed a small decline with time, to 0.5–0.3 mM at the end of the period, indicating a deficient diet. The haemocyanin in the other groups did not change significantly during the experiment. Moultings decreased in frequency and the intermoult period was prolonged when the quality of food was decreased, and in the starved group moulting ceased completely after 1.5 months. Haemocyanin concentration was lowest immediately after moult and increased gradually through stages C and D. Lobsters that were starved or maintained on the bivalve diet did not reach the same premoult haemocyanin levels as those fed with shrimps and mixed food.     

Setal development,moult-staging and ecdysis in the banana prawn Penaeus merguiensis

Specimens of juvenile Penaeus merguiensis de Man (1888) were captured by seine netting from the shores of Cleveland Bay, Townsville, Queensland Australia between February 1980 and November 1981. Accurate determination of moult cycle stage can be achieved rapidly by microsopical examination of setal development in an excised whole pleopod. Four major stages and 5 substages within premoult were clearly defined. The rate of setogenesis varies along the length of a pleopod, precluding the examination of only one specific location on the pleopod for accurate moult cycle staging. The process of ecdysis lasts for no more than 40 s.     

The Hiatt growth diagram for crustacea

The Hiatt growth diagram relates post-moult to pre-moult size in crustaceans. Size in this context is most frequently defined by a linear measurement of length or width. Linear regression analysis of data on the Hiatt growth diagram is used to define growth constants. This assumes that growth factors (percentage increase in body size) at successive moults remain constant over the length of the line. Growth factors, however, decrease logarithmically at successive moults. Consequently, points on a Hiatt growth diagram are fitted better by a hyperbola than a straight line. The method of fitting an equation for a hyperbola is given. The best growth constant is the moult slope factor which is the factor by which the growth factor decreases at each successive moult. This is comparable with the intermoult period slope factor, the factor by which the intermoult period increases at each successive moult. These constants can be used to determine the moulting and growth sequences throughout the life of a crustacean.     

Use of nucleic acids as indicators of growth in juvenile white shrimp,Penaeus vannamei

The use of nucleic acids to estimate crustacean growth is not well documented, and may be complicated by biochemical changes associated with their molt cycle. The objectives of this study were to assess the effects of molt stage on nucleic acid concentrations in abdominal muscle tissue of juvenile white shrimp,Penaeus vannamei, and to examine the relationship between nucleic acid concentrations and growth rates of shrimp exposed to different feeding regimes throughout a 12 d feeding experiment. RNA and DNA concentrations and RNA:DNA ratios were not significantly different among the five major molt stages early postmolt, late postmolt, intermolt, early premolt, and late premolt. In the feeding experiment, RNA concentrations and RNA:DNA ratios accounted for >70% of the variation in shrimp growth on three different sampling days. In addition, RNA concentrations and RNA:DNA ratios were used successfully to discriminate between unfed, moderately-fed, and well-fed shrimp. These variables exhibited significant treatment differences in <24 h after the initiation of the different feeding regimes, whereas significant changes in whole-body weight took longer to detect. Rapid detection of significant treatment effects can be useful in ecological studes, especially those concerned with food-web interactions.     

Blood sugar metabolism during moulting in the isopod crustacean Ligia exotica

Blood sugar metabolism of the isopod Ligia exotica Roux was studied in relation to chitin synthesis during the moult cycle. The blood sugars were found to occur free, as well as bound with blood proteins, during all moult stages, as in Emerita asiatica. The variety of free blood sugars is smaller in L. exotica; it comprises only glucose and glucose-6-phosphate. The protein-bound blood sugars are glucose and glucosamine. The blood-volume values do not differ markedly during the moult cycle. Estimations of blood sugars showed a marked rise of sugar levels in the blood during the premoult phase, and a subsequent fall during the freshmoult phase, when chitin is actively synthesised. The chitin values also showed a definite correlation with the blood-sugar values. The increased resorption of chitin during the premoult stage, and its liberation into the blood stream as glucosamine, is indicative of its reutilisation in chitin synthesis as in E. asiatica and the genus Cecropia. As more immediate precursors of chitin, such as uridine diphosphate and uridine diphophate acetylglucosamine compounds, were absent in the blood, a thorough biochemical study of the epidermis is suggested to locate the intermediate precursors of chitin which are possibly derived from blood sugars.     

Respiratory metabolism of Pagurus bernhardus (Decapoda: Paguridae) megalopa

Individual oxygen consumption was determined during the megalopa development of Pagurus bernhardus at 18°C in 1983. The maximum observed range was from 0.101 to 0.343 l O₂ h^-1 ind^-1. Individual respiration rate dropped by about 33% during the first two days and continued to remain at that level throughout the moult cycle. The results are discussed together with data on biomass and the fact that P. bernhardus megalopa do not feed.     

Moult in relation to some aspects of reproduction and growth in swarms of Antarctic krill,Euphausia superba

In a 14-d period 38 swarms of Antarctic krill,Euphausia superba Dana, were sampled in an area 55.5 x 55.5 km to the southwest of Elephant Island, at the north of the South Shetland Islands. Moult stage, maturity stage, and size of ca. 100 krill from each swarm were measured. Each of the characteristics varied greatly between swarms. Moulting krill were found in most swarms, but in one swarm all of the krill were just about to moult. Ways in which moulting may act as a possible sorting mechanism are discussed. Data for all the analysed krill (ca. 3000 specimens) were used to investigate the interdependence of moult rate, sexual maturation and growth. While all immature krill moulted at approximately the saine rate in the study, there were significant differences in the moulting rates of mature male and female krill. Gravid female krill continued to moult, although less frequently than mature males. As a consequence males had to attach spermatophores to females after each moult. It is likely that variation in moult rate of females and males was related to the energy expenditure required for ovary development in females and spermatophore production and searching behaviour in males. Spawning and moulting were only partly coupled in gravid females. Spawning appeared to take place predominantly during Moult Stage D₂. There was no evidence of intermoult growth by intersegmental dilation.     

Changes of respiration and biomass of spider crab (Hyas araneus) larvae during starvation

The influence of starvation on respiration (R), dry weight (W), carbon (C), nitrogen (N), hydrogen (H), and energy content (E; calculated fromC) of spider crab (Hyas araneus L.) larvae was studied in the laboratory. In all larval stages (zoea I and II, megalopa)W increased during postmoult, independent of food, and decreased subsequently. The final reduction inW after continued starvation increased from stage to stage (9, 13, and 20% respectively), but it was always much lower than the decrease inC (44 to 52%),N (42 to 46%),H (50 to 58%), andE (53 to 62%). Individual (R) and weight-specific respiration rates (QO ₂) were reduced by 83 to 88%. The time-dependence of these reductions in metabolism and biomass as well as the rates of change in all parameters studied were described with non-linear regression models and differential equations, respectively. Rates and total amounts of energy lost during starvation were independently calculated fromC andR values, and similar results were mostly obtained. Only in the megalopa stage was there a conspicuous difference between the two estimates: higher losses were calculated fromR. This shows that further (biochemical) data are required for a more complete understanding of the energetics of this stage. Estimates of total protein (fromN) and lipid (fromC) suggest that both constituents serve as metabolic substrates during starvation, but most of the energy originates from the breakdown of protein.Supported by the Deutsche Forschungsgemeinschaft (An 145/1-1)     

Patterns of growth and triacylglycerol content in snow crab Chionoecetes opilio (Brachyura: Majidae) zoeal stages reared in the laboratory

Snow carb Chionoecetes opilio zoea I and zoea II larvae, hatched from females in a controlled mating experiment, were reared in the laboratory at 10.1 °C and 28.0 salinity, to resolve the patterns of growth (dry weight [DW]) and change in energy reserves (triacylglycerols [TAG]) within a given moult cycle. The patterns of growth and change in TAG reserves were similar in each zoeal stage. Following hatching or a moult, the zoeae entered a phase of rapid size increase, i.e. high daily growth rates (5.5 to 12.8% DWd^-1), for 1/3 to 2/5 of the duration of the moult cycle. During the same period, the zoeae accumulated TAG reserves until a maximum (TAG DW^-1) was reached at the end of the phase of rapid growth. The period of high growth rates and of TAG accumulation is interpreted as the required time for the zoeae to reach a point in development [i.e. point of reserves saturation (PRS); Anger and Dawirs (1981)] where sufficient growth and energy reserves allow moulting to the next stage. Following the phase of rapid growth and TAG accumulation, the zoeae entered a phase of low daily growth rates (0 to 1% DWd^-1) during which the TAG reserves decreased to a minimum at the end of the phase. Prior to, and during the moult to zoea II, a phase of negative growth was observed in the zoea I larvae. We conclude that measurement of zoeal size and TAG content, along with morphometric criteria (e.g. epidermal retraction), can be used to assess growth and nutritional condition of C. opilio zoeal stages from the sea.