Influence of sea surface temperature on reproductive period and size at maturity of brown shrimp (<Emphasis Type="Italic">Farfantepenaeus californiensis</Emphasis>) in the Gulf of California

Reproductive period and size at maturity of the brown shrimp Farfantepenaeus californiensis were analyzed for correspondence to sea surface temperature (SST) in three zones of the Gulf of California. Mature females from fishing areas in the north (Puerto Peñasco), center (Guaymas), and south (Mazatlán), and monthly SST were examined. Average SST for 1983–2000 decreased from Mazatlán (26.2±0.2°C) to Puerto Peñasco (22.6±0.3°C). The seasonal variation in SST between coldest and warmest months was 7.8°C in Mazatlán and 11.4°C in Puerto Peñasco. The size of shrimps at maturity was inversely correlated to SST, increasing from Mazatlán (121 mm total length) to Puerto Peñasco (154 mm total length). The reproductive period near Mazatlán is year-round. Guaymas and Puerto Peñasco have one period of high intensity. We conclude that warmer water and low seasonal variability allow brown shrimp to reproduce more frequently, but reach smaller size at maturity.Communicated by P.W. Sammarco, Chauvin     

Population structure and growth in captivity of the spiny lobsterPanulirus penicillatus from Dahab,Gulf of Aqaba,Red Sea

Panulirus penicillatus (Olivier, 1791) (Decapoda: Palinuridae) is the most common spiny lobster in the Red Sea and is widely distributed in the Indian and Pacific Oceans. Lobsters (n=377) were collected on four occasions during 1986 on the coral reef at Dahab, Sinai, Egypt. Average size of the collected individuals was 70.5±24.6 mm carapace length (CL) for males and 63.2±15.9 mm CL for females. The sex ratio was 1:1.64 males to females. Length increment per molt was inversely correlated with size and ranged from 2.1 mm per molt in the 40 to 50 mm CL size class to less than 1 mm in the 60 to 70 mm CL size class. Average intermolt period was ca. 136 d for all size classes. The relationship between carapace length and body weight was expressed by the equation:W _b=6.43 × 10^–4 × (CL)^2.89.P. penicillatus from Dahab differ in size, sex ratio and growth rate compared to other palinurid populations throughout their range. This might represent the effect of isolation and location at the edge of the geographical range for this species. It may also indicate an adaptation to their unique habitat in the coral reef in comparison to other palinurid species.     

Effect of temperature on the molting,growth and maturation of the antarctic krill Euphausia superba (Crustacea: Euphausiacea) under laboratory conditions

The effect of temperature on molting, growth, and maturation rates was studied on laboratory-maintained Euphausia superba. The length of intermolt periods (IMP's) was inversely proportional to temperature (20.10 d, SD=1.60, at 0.12°C; 16.87 d, SD=1.68, at 0.97°C; and 12.48 d, SD=0.90, at 4.48°C), and directly proportional to krill size at 0.12°C and 0.97°C. For individually maintained krill the maximum growth rate at 4.48°C (0.068 mm d^-1) was nearly twice that at 0.68°C (0.037 mm d^-1). There was no observable temperature effect on maturation rates. The maturation changes of juveniles at all temperatures indicated that more than two years are probably required to reach maturity. Mature males and females regressed to immature forms, suggesting that E. superba may reproduce in successive years. These results and previously reported field and laboratory data for E. superba and other euphausiid species suggest a 4+ year life span for this species.This work was supported by NSF grant DPP 76-23437     

Metabolism and body composition of a copepod (<Emphasis Type="Italic">Neocalanus cristatus</Emphasis>: Crustacea) from the bathypelagic zone of the Oyashio region,western subarctic Pacific

Metabolism [respiratory oxygen consumption, electron-transfer-system (ETS) activity] and body composition [water, ash, carbon (C), nitrogen (N), carbon/nitrogen (C/N) ratio] of stage C5/C6 Neocalanus cristatus from 1000 to 2000 m depth of the Oyashio region, western subarctic Pacific, were determined during the period of July 2000 through June 2003. Compared with the C5 specimens from shallow depths (<250 m), those from 1000 to 2000 m were characterized by quiescent behavior, reduced respiration rates (30% of the rates at active feeding), very low water content (61–70% of wet weight), but high C content (56–64% of dry weight) and C/N ratios (7.2–10.6, by weight). Artifacts due to the recovery of live specimens from the bathypelagic zone appeared to be unlikely in this study, as judged by the consistent results between re-compression (100 atm) and non-compression (1 atm) respiration experiments, and between ETS activities and respiration rates directly measured. In addition, the respiration rates of C6 males and females of N. cristatus from the same 1000–2000 m depth were two to three times higher than the rates of C5 individuals, but were similar to the rates of a bathypelagic copepod, Paraeuchaeta rubra. Combining these results with literature data, C budgets of: (1) diapausing C5 specimens, weighing 6–10 mg dry weight; (2) molt to C6 females; and (3) the complete the life span were established, taking into account assorted losses in respiration during diapause at stages C5 and C6, molt production and egg production. Respiratory C losses by C5 and C6 specimens were estimated on the basis of body N as adjusted metabolic rates [AMR; µl O₂ (mg body N)^–0.843 h^–1], then N budgets were also computed subtracting N lost in the form of cast molts and eggs from the initial stock. Calculations revealed that allocation of the C stock was greatest to egg production (34–57%), followed by respiration (27%) and cast molts (3%), leaving residual C of 13–36% in spent C6 females. The present results for N. cristatus from the North Pacific are compared with those of Calanus spp. in the North Atlantic.Communicated by O. Kinne, Oldendorf/Luhe     

Production of glycine betaine and dimethylsulfoniopropionate in marine phytoplankton. II. N-limited chemostat cultures

The influence of salinity on the time elapsed between two successive molts and the size reached after each molt were studied at 30, 21, 12 and 3‰S in juveniles of two co-occurring grapsid species, Cyrtograpsus angulatus and C. altimanus, cultured under identical conditions of temperature, photoperiod and food. Juvenile growth patterns were compared between these species (which differ in size-at-maturity and maximum size). C. angulatus grew faster than C. altimanus, reflecting a higher increment per molt and a shorter intermolt period. A significant difference existed between the number of instars preceding the size of maturity in both species: >11 in C. angulatus, 6 in C. altimanus. There was evidence of a differential effect of low salinity on growth. By the end of the experiment, individuals of both species were smaller at the lowest salinity (3‰) tested; the largest crabs developed at 21‰ (C. angulatus) and 30‰ (C. altimanus). The size difference between the “optimal” and the less suitable salinities in the sixth crab instar was 12.4% in C. angulatus and 35% in C. altimanus. During early juvenile development (Crab Instars 1 to 4), there were slight differences in intermolt period among salinities in C. angulatus, but large differences in C. altimanus. The longest intermolt period of C. altimanus was at 3‰S and the shortest at 30‰S. In the following instars (5 to 10 in C. angulatus and 5 to 6 in C. altimanus), the longest intermolt period occurred at 21‰S, the shortest at 3‰S, in both species. Interspecific differences in response to low salinities may explain why C. angulatus occurs throughout a whole temperate coastal lagoon, whereas C. altimanus is restricted to its mouth. Received: 12 July 1998 / Accepted: 24 February 1999     

Yolk utilization and growth to yolk-sac absorption in summer flounder (Paralichthys dentatus) larvae at constant and cyclic temperatures

Rates of development, growth and yolk conversion efficiency were determined in larvae of the summer flounder Paralichtys dentatus at constant temperatures of 21°, 16°, 12° and 5°C and in temperature cycles of 21°–16°, 16°–11°, and 11°–5°C. In constant incubation temperatures, development rate increased with increasing temperature. Larvae reared in the cyclic temperature regimes exhibited development rates intermediate to those at the temperature extremes of the cycle. All larvae reared at 5°C and in the 11°–5°C cycle regime died prior to total yolk-sac absorption. Although development rates were temperature dependent, no significant differences in notochord length ash-free dry weight or yolk utilization efficiency were found at the time of total yolk-sac absorption. The similarity in growth and yolk utilization efficiency for larvae reared under these various temperature regimes suggests that the physiological mechanisms involved are able to compensate for temperature changes encountered in nature.Contribution No. 195 from EPA, Environmental Research Laboratory, Narragansett, Rhode Island 02882, USA     

Effects of temperature and size on molting of euphausiid crustaceans

The effects of temperature and body size on the intermolt periods (molting frequencies) of the North Pacific euphausíid Euphausia pacifica and the Mediterranean forms of Meganyctiphanes norvegica, Euphausia krohnii, Nematoscelis megalops, and Nyctiphanes couchii were studied under controlled conditions in the laboratory. Mean intermolt periods for E. pacifica and M. norvegica were inversely and linearly related to temperature, over temperature ranges which the euphausiids normally encounter in the sea. At higher temperatures there was a tendency for three size groups of M. norvegica to approach a minimum intermolt period independent of temperature. M. norvegica cycled for different time periods between 13° and 18°C molted regularly at mean frequencies which would be expected if the animals had been held constantly at the timeweighted means of the two experimental temperatures. The increase in mean intermolt period per unit weight was faster in small, fast-growing M. norvegica than in large, slow-growing adults. This relationship was corroborated by following the changes in the intermolt period of an actively growing individual N. couchii over an 11 month period. Neither feeding nor the time of year of collection affected the molting frequency as long as temperature and animal weight were held constant. No tendency was found for euphausiids of the same species and/or size, and from the same collection, to molt on the same night. Molting occurred at night 80 to 90% of the time for all species, over the temperature ranges normally experienced by the euphausiids in the sea, and over all animal weights tested. There appeared to be a weakening of the night-time molting rhythm at low temperatures. Although neither temperature nor anímal weight substantially affected the night-time molting rhythm, both affected the mean intermolt period. Therefore, both temperature and body size apparently act together to adjust the length of the intermolt period of each individual in increments of whole days, but they exert little control over time of molting within any 24h period. No information was obtained regarding the factors which specify night-time molting over daytime molting within any 24 h period; however, regulation of certain hormone activities is probably involved.     

Comparative life-history study on sympatric hyperiid amphipods (<Emphasis Type="Italic">Themisto pacifica</Emphasis> and <Emphasis Type="Italic">T</Emphasis>. <Emphasis Type="Italic">japonica</Emphasis>) in the Oyashio region,western North Pacific

Life-history features of the sympatric amphipods Themisto pacifica and T. japonica in the western North Pacific were analyzed based on seasonal field samples collected from July 1996 through July 1998, and data from laboratory rearing experiments. T. pacfica occurred throughout the year, with populations peaking from spring to summer. In contrast, T. japonica were rare from autumn to early winter, but became abundant in late winter to spring. Mature T. pacifica females and juveniles occurred together throughout the year, indicating year-round reproduction. Mature T. japonica females were observed only in spring, and juveniles occurred irregularly in small numbers, suggesting limited, early-spring reproduction in this study area. Size composition analysis of T. pacifica identified a total of eight cohorts over the 2 years of the study. Due to the smaller sample size and rarity of mature females (>9.6 mm) and males (>7.1 mm), cohort analyses of T. japonica were not comparable. Laboratory rearing of specimens at 2°C, 5°C, 8°C and 12°C revealed that a linear equation best expressed body length growth by T. pacifica, while a logistic equation best expressed body length growth by T. japoncia. Combining these laboratory-derived growth patterns with maturity sizes of wild specimens, the minimum and maximum generation times of females at a temperature range of 2–12°C were computed as 32 days (12°C) and 224 days (2°C), respectively, for T. pacifica, and 66 days (12°C) and 358 days (2°C), respectively, for T. japonica. The numbers of eggs or juveniles in females marsupia increased with female body length and ranged from 23 to 64 for T. pacifica and from 152 to 601 for T. japonica. Taking into account the number of mature female instars, lifetime fecundities were estimated as 342 eggs for T. pacifica and 1195 eggs for T. japonica. Possible mechanisms for the coexistence of these two amphipods in the Oyashio region are also discussed.Communicated by O. Kinne, Oldendorf/Luhe     

Size and temperature-dependent variations in intermolt duration and size increment at molt of Northern Shrimp, Pandalus borealis

Growth of Pandalus borealis post-larval stages was measured in relation to size and temperature. Growth characteristics, including intermolt period (IP), molt increment (MI) in size and mass, and tissue allocation in juvenile, male, and female shrimp, were evaluated at 2, 5, and 8°C, the temperature range where this species is generally found in the Northwest Atlantic. Significant variations in growth were associated with temperature and shrimp size. IP (days) increased significantly with shrimp size and was inversely related to temperature. Size (cephalothorax length in mm) and temperature effects were best described by IP = 10^{(0.67 log(CL) − 0.06 T − 1.34)}. The pronounced effect of temperature on IP while MI_S changed little indicated that the main influence of temperature on growth rate of P. borealis was through IP. Specific growth rate (SGR_S) decreased rapidly with size to near zero values in females. Overall, juveniles were much more sensitive to temperature variations than adults, suggesting that temperatures encountered during the juvenile stage will largely influence the growth trajectory of the population.     

Otolith microstructure and daily increment validation of marbled sole (<Emphasis Type="Italic">Pseudopleuronectes yokohamae</Emphasis>)

We examined the daily deposition of otolith increments of marbled sole (Pseudopleuronectes yokohamae) larvae and juveniles by rearing experiments, and estimated the growth pattern of wild larvae and juveniles in Hakodate Bay (Hokkaido Island, Japan). At 16°C, prominent checks (inner checks; ca. 19.8 µm in diameter) were observed on the centers of sagittae and lapilli extracted from 5-day-old larvae. On both otoliths, distinctive and regular increments were observed outside of the inner checks, and the slopes of regression lines between age and the number of increments (n_i) (for sagittae: n_i=0.98×Day–5.90; for lapillus: n_i=0.96×Day–5.70) did not significantly differ from 1. Inner check formations were delayed at lower temperature, and the inner checks formed 13 days after hatching at 8°C. Over 80% of larvae, just after their yolk-sac has been absorbed completely (stage C), had inner checks on both their otoliths. On the lapilli, other checks (outer check) formed at the beginning of eye migration (stage G). To validate the daily deposition of increments during the juvenile stage, wild captured P. yokohamae juveniles were immersed in alizarin complexone (ALC)-seawater solutions and reared in cages set in their natural habitat. After 6 days, the mean number of rings deposited after the ALC mark was 5.7. The age–body length relationship of wild P. yokohamae larvae and juveniles caught in Hakodate Bay was divided into three phases. In the larval period, the relationship was represented by a quadratic equation (notochord length=–0.010×Age²+0.682×Age–2.480, r²=0.82, P<0.001), and the estimated instantaneous growth was 0.38 mm day^–1 at 15 days, 0 mm day^–1 at 34 days and –0.12 mm day^–1 at 40 days. The age–body length relationship in the early juvenile stage (<50 days) and the late juvenile stage (>50 days) were represented by linear equations (standard length=0.055×Age+5.722 and standard length=0.345×Age–9.908, respectively). These results showed that the growth rates in the late larval periods and the early juvenile stage were lower than those in the early larval stage and late juvenile stage; during the slow growth period, energy appears to be directed towards metamorphosis rather than body growth. This study provided the information needed to use otolith microstructure analysis for wild marbled sole larvae and juveniles.Communicated by T. Ikeda, Hakodate     

Growth and moulting of Neomysis integer (Crustacea: Mysidacea)

The growth and moulting of Neomysis integer (Leach) was investigated in the field and the laboratory. In the Ythan estuary, Aberdeenshire, Scotland, monthly samples taken from November 1976 to October 1978 revealed that the summer generation juveniles and mature individuals grew at a rate of 4 to 5 mm and 1 to 2 mm monthly, respectively. The winter generation had a growth rate of 3 to 4 mm monthly for juveniles and about 1 mm for mature individuals; during the winter there was a period of 3 mo when growth was almost completely stopped. Mysids reared in the laboratory on Artemia sp. nauplii had an average daily growth rate of 0.06 mm at 9°C and 0.09 mm at 16°C. The growth factors of N. integer ranged from 3 to 17% for mature and immature individuals, respectively. Intermoult periods ranged from 3 to 7 d in immature mysids to 12 to 18 d in mature mysids. Average laboratory growth curves calculated from information on growth factors and intermoult periods indicate that at 9°C (winter generation) it takes N. integer 277 d to grow to be a 15 mm mature individual, whereas at 16°C (summer generation) it takes 188 d. N. integer moults 24 times as it grows from a juvenile to a mature individual.     

Changes in nucleic acids over the molt cycle in relation to food availability and temperature in Homarus americanus postlarvae

Postlarval lobsters Homarus americanus Milne Edwards hatched from three females collected in 1989 from Block Island Sound, Rhode Island were reared individually in the laboratory under nine treatment combinations of temperature (15, 18 and 21°C) and feeding (starved, low ration and full ration). Total RNA, DNA (mgind.^-1), RNA:DNA ratios and molt stage were determined for individuals sampled at daily intervals. Postlarval lobsters had high resistance to starvation. A majority of the lobsters survive 12 d of food deprivation, with some surviving up to 24–29 d. During starvation, cell biomass (estimated from protein:DNA) decreased to a minumum size, whereas cell number (based on total DNA) was generally conserved. The molt cycle was arrested at molt stage C in the starved postalrvae. Instar duration was inversely related to temperature. However, the duration of the postlarval instar did not differ between the low and full ration treatments. Uncoupling of cell growth and the molt cycle was evident in the full and low ration treatments. In the full ration treatments, the postmolt through early premolt was characterized by a rapid increase in total RNA and DNA. Maximum cell biomass was attained by molt stage C or D₀. In the low ration treatments, total RNA and DNA were less than those in the full ration treatments and the maximum cell biomass was attained only at molt stage D_2-3. Notably, different feeding regimes resulted in different patterns in RNA:DNA ratios over the molt cycle during the postlarval instar. RNA:DNA ratio was a sensitive indicator of recent (2 to 3 d) food deprivation. However, this ratio was positively related to the level of feeding only at molt stages C to D₁ and was inversely related to temperature regime. These results indicate that the use of RNA:DNA ratios to estimate the relative nutritional state of postlarval tobsters must be qualified with respect to the period of the molt cycle and the temperature regime.     

Egg survival,embryonic development,and larval characteristics of northern shrimp (<Emphasis Type="Italic">Pandalus borealis</Emphasis>) females subject to different temperature and feeding conditions

Laboratory experiments on ovigerous females of northern shrimp (Pandalus borealis) were used to assess the effects of temperature and food ration on female condition during incubation and examine how combined effects of temperature and female condition influenced egg survival, embryonic development, and larval characteristics. Ovigerous females were maintained at 2°C, 5°C, and 8°C and fed on a low (three times/week; 2–2.7% W/W) or high ration (five times/week at satiation). The increase in temperature accelerated the developmental time of the eggs but their survival at 8°C was reduced. Conversion efficiency of yolk reserves in developing embryos was significantly reduced at elevated temperatures and larvae hatching at 2°C and 5°C were significantly larger and heavier than those hatching at 8°C. The experimental design did not result in any effect of food ration on the energetic condition of females or on egg characteristics and their biochemical composition. However, lower energy reserves were observed for females held at 8°C.     

Effect of temperature on laboratory growth,reproduction and life span of Octopus bimaculoides

Laboratory culture of 40 Octopus bimaculoides from April 1982 to August 1983 through the full life cycle at 18°C vs 23°C provided information on the growth, reproductive biology and life span of this California littoral octopus. At 18°C, the cephalopods grew from a hatchling size of 0.07 g to a mean of 619 g in 404 d; the largest individual was 872 g. Octopuses cultured at 23°C reached their highest mean weight of 597 g in 370 d; the largest individual grown at this temperature was 848 g after 404 d. Growth data revealed a two-phase growth pattern: a 5 mo exponential phase followed by a slower logarithmic (power function) phase until spawning. At 5 mo octopuses grown at 23°C were over three times larger than their 18°C siblings. However, beyond 6.5 mo, growth rates were no higher at 23°C than at 18°C. At 13.5 mo, the mean weight of the 18°C group surpassed that of the 23°C group. The slope of the length/weight (L/W) relationship was significantly different for the two temperature regimes, with the 23°C octopuses weighing 18% less than their 18°C siblings at a mantle length of 100 mm. Females weighed more than males at any given mantle length. Males grew slightly larger and matured before females. The L/W relationship indicated isometric body growth throughout the life cycle. Higher temperature accelerated all aspects of reproductive biology and shortened life span by as much as 20% (from approximately 16 to 13 mo). O. bimaculoides has one of the longest life cycles among species with large eggs and benthic hatchlings. Extrapolations to field growth are made, and the possible effects of temperature anomalies such as El Niño are discussed.     

Effects of various temperature cycles on the larval development of the gastropod molluscCrepidula fornicata

Veligers ofCrepidula fornicata (L.) were reared for 12 days at constant temperatures of 15°, 20°, 25°, 30° and 35°C, and at 5 C° daily cycles of equal periodicity (COEP) over the temperature ranges 15° to 20°C, 20° to 25°C, 25° to 30°C and 30° to 35°C. COEP consisted of equal periods (6 h) of maximum temperature, minimum temperature, and uniformly increasing and decreasing temperature each 24 h period. Survival was high and not influenced by cyclic or constant temperature from 15° to 30°C. At 35°C and COEP 30° to 35°C, all larvae died before Day 6. Shell growth rate increased markedly over the range 15° to 25°C, and growth rates at cyclic temperatures in this range were intermediate between growth rates at the corresponding constant temperatures. Larvae reared at COEP 15° to 20°C and COEP 30° to 35°C had discontinuities in their shells due to inhibition of shell secretion during the adverse part of each temperature cycle. Groups ofc. fornicata veligers were exposed for 2 days to daily temperature cycles of equal and unequal periodicity in the critical 30° to 35°C range. [Cycles of unequal periodicity (COUP) consisted of unequal periods (varying between 3 and 15 h) of maximum and minimum temperature and uniformly increasing and decreasing temperature each 24 h period.] These veligers showed shell growth although their body tissue declined, as indicated by decreasing carbon content per larva. Least shell growth and most body tissue loss occurred in those cycles with the longest exposure to higher temperature. Larvae exposed for arious days to the mildest 30° to 35°C COUP (15 h at 30°C, 3 h increasing temperature, 3 h at 35°C and 3 h decreasing temperature) recovered and resumed normal growth when transferred to constant 30°C, but their growth was retarded in proportion to the number of days in the temperature cycle. Rates of shell growth of veligers in temperature cycles show an immediate effect of environmental temperature, while changes in carbon content per larva better reflect the effects of temperature on general metabolism and survival.     

Growth rate of the bathypelagic crustacean Gnathophausia ingens (Mysidacea: Lophogastridae). I. Dimensional growth and population structure

Gnathophausia ingens has 13 instars, each with a distinct range of sizes which does not overlap the sizes of adjacent instars. The intermolt interval, measured in the laboratory at 5.5°, 6.5° and 7.5°C, increases with increasing size and decreases with increasing temperature. At 5.5°C it varies from 166 days for the smallest individuals to 253 days for the oldest. The period of larval development in the marsupium of a female is estimated to be 530 days. The life span of females is estimated to be 2,950 days with the onset of reproduction at 2,400 days. It is sugquested that this species is semelparous. The population structure data suggest that there is low mortality through the first 7 instars, progressively higher mortality from Instar 8 through Instar 11, and slightly lower mortality in the remaining 2 instars. These life-history characteristics appear to be directed toward maximizing absolute fecundity (as opposed to time-specific fecundity) in a stable environment. These characteristics may have been selected for by low available food energy and made possible by the stability of the deep sea.     

Population dynamics and production of the planktonic copepods in a eutrophic inlet of the Inland Sea of Japan. I. Centropages abdominalis

Population dynamics and production of the calanoid copepod Centropages abdominalis were studied from November 1986 to November 1987 in Fukuyama Harbor, in the central part of the Inland Sea of Japan. This species was present in the plankton during a cold-water period from November to June (temperature range: 8.9 to 21.1 °C), with a peak abundance (23 600 ind m^–3) in February. During this period, six generations could be detected, and each generation time agreed well with that predicted from food-satiated laboratory experiments, indicating that the natural population was not food-limited. The population suffered extremely high mortality during the period from egg to naupliar stage (N) II: only 0.02 to 4% of the eggs survived to NII. However, the mortality in stages older than NII was almost negligible. The growth rate of C. abdominalis increased exponentially with increasing temperature. Its biomass and production rate showed marked seasonal variations largely in parallel with numerical abundance. The estimated production between 7 November 1986 and 29 May 1987 was 355 mg C m^–3 or 2.66 g C m^–2, 95% of which occurred during February and March. The daily production rate to biomass ratio increased exponentially with temperature from 0.18 at 8.9°C to 0.37 at 19°C.     

Testing hypotheses of exponential growth and size-dependent molting rate in two copepod species

Individual copepodids from nature of the lipidstoring, monocyclic, diapausing Calanus glacialis, and from nature and laboratory culture of the non-storing, polycyclic Eurytemora herdmani (both collected new Halifax, Nova Scotia in 1987 and 1988) were reared in excess food at ca. 3 and 10 °C. Soon after molts, prosome lengths and weights [total dry wt (TW) of E. herdmani; structural wt (SW) and estimated oil-sac wt (OSW) of C. glacialis] were measured. Stage durations were close to published temperature-dependent predictions; C. glacialis (almost all females) did not enter resting stages. Growth of body length was linear and of body weight (TW or SW) was exponential, with no sexual difference in E. herdmani. There were mixed effects of sizes on stage durations of individuals: weakly positive at 3 °C (but not significant at ca. 10°C) for length and SW of C. glacialis and generally weakly negative for E. herdmani, except for TW at 10 °C. Body condition (residuals of log SW vs log length) of C. glacialis at ca. 10°C, unlike length or SW, was negatively related to stage duration. There was no relationship between length-corrected SW and OSW in C. glacialis. The various results appear to suggest that health was more important than allometric constraints on growth rates of individuals. However, copepods reared at temperatures very different from those previously experienced may show long-term adjustments of size, whereas development rates respond immediately. If so, only the weakly positive effects on stage durations of length of C. glacialis at ca. 3 °C and of TW of E. herdmani at ca. 10 °C may illustrate expectations under stable temperatures and adequate food in nature.     

Energy content at metamorphosis and growth rate of the early juvenile barnacle<Emphasis Type="Italic"> Balanus amphitrite</Emphasis>

The energetic cost of metamorphosis in cyprids of the barnacle Balanus amphitrite Darwin was estimated by quantification of lipid, carbohydrate and protein contents. About 38–58% (4–5 mJ individual^–1) of cypris energy reserves were used during metamorphosis. Lipids accounted for 55–65%, proteins for 34–44% and carbohydrates for <2% of the energy used. Juveniles obtained from larvae fed 10⁶ cells ml^–1 of Chaetoceros gracilis were bigger (carapace length: 560–616 µm) and contained more energy (5.56±0.10 mJ juvenile^–1) than their counterparts (carapace length: 420–462 µm; energy content: 2.49±0.20 mJ juvenile^–1) obtained from larvae fed 10⁴ cells ml^–1. At water temperatures of 30°C and 24°C and food concentrations of 10⁴ and 10² cells ml^–1 (3:1 mixture of C. gracilis and Isochrysis galbana) as well as under field conditions (26.9±3.1°C and 2.2±0.8 µg chlorophyll a l^–1), juveniles obtained from larvae fed the high food concentration grew faster than juveniles obtained from larvae fed low food concentration until 5 days post-metamorphosis. Laboratory experiments revealed a combined effect of early juvenile energy content, temperature and food concentration on growth until 5 days post-metamorphosis. After 10 days post-metamorphosis, the influence of the early juvenile energy content on growth became negligible. Overall, our results indicate that the energy content at metamorphosis is of critical importance for initial growth of juvenile barnacles and emphasize the dependency of the physiological performance of early juvenile barnacles on the larval exposure to food.Communicated by O. Kinne, Oldendorf/LuheAn erratum to this article can be found at     

Population biology of hyperbenthic crustaceans in a cold water environment (Conception Bay,Newfoundland). I.<Emphasis Type="Italic"> Mysis mixta</Emphasis> (Mysidacea)

Seasonal population dynamics of Mysis mixta Lilljeborg were studied from December 1998 to November 2000 at a 240 m deep site in Conception Bay, Newfoundland. At this depth, temperature was <0°C and salinity between 32.0 and 34.0 psu year-round. The spring phytoplankton bloom began in early or late March and reached a maximum in late April to mid-May. M. mixta exhibited a highly synchronised life cycle, with spawning and mating occurring in October to November, embryos brooded for ~5 months, and juveniles released during spring bloom sedimentation in April and May. Females were semelparous and died at age 2.5 years, following release of juveniles in spring, whereas the majority of mature males died at age 2 years, following mating in November. The biennial life cycle of this population resulted in the presence of two cohorts in the hyperbenthos at any given time. Variation in density and biomass was low among cohorts but high within cohorts, the latter probably due to the high motility of mysids. Densities in 1999 and 2000 were 242±379 and 544±987 ind. per 100 m³ (mean±SD), respectively. Although growth rates were similar between years, rates measured from changes in dry mass differed both seasonally and among life-history stages (range from –4 to 7 mg month^–1). Annual secondary production was estimated at 29–73 mg C m^–2 in 1999 and 53–205 mg C m^–2 in 2000. The annual P/B ratios were 1.62 and 1.19 in 1999 and 2000, respectively.Communicated by J.P. Grassle, New Brunswick