Comparing biochemical changes and energetic costs in gastropods with different developmental modes: <Emphasis Type="Italic">Crepipatella dilatata</Emphasis> and <Emphasis Type="Italic">C. fecunda</Emphasis>

The Chilean gastropods Crepipatella dilatata and C. fecunda have different development modes: brooding and direct development in C. dilatata and brooding and planktotrophic development in C. fecunda. Unlike many other congeneric invertebrate species pairs, recent genetic evidence suggests that C. fecunda may have evolved from C. dilatata. To explore the changes involved in this unusual evolutionary path, this study examined the biochemical, energetic, and morphological characters during early development of both species. Mean egg size was slightly smaller for the direct-developing species C. dilatata, and initial energy content was lower—by about 27%—for eggs of that species. In both species, protein content in the eggs was the principal biochemical component. Although females of C. fecunda produce 180 times more eggs than C. dilatata, females of C. dilatata invest 20 times more energy in each of their offspring, through nurse eggs; their embryos have approximately eight times more energy at hatching and about 5 times more energy when they enter the benthos, despite a long planktonic feeding period in the larvae of C. fecunda. Evolutionary switching between modes of development in these species is reflected in shifts in maternal energy investment.     

Fluctuating asymmetry and nutritional condition of Baltic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) larvae

The level of fluctuating asymmetry (FA), defined as random deviations from perfect bilateral symmetry, is assumed to reflect the developmental instability (DI) of an organism. Because environmental and genetic stress may increase DI, FA has been used to assess the level of stress experienced by, for example, fish. In this study, left–right asymmetry of lapillar otoliths was related to nutritional condition as estimated from RNA/DNA ratios, in order to investigate the utility of FA to detect feeding-related stress in Baltic cod, Gadus morhua L., larvae. Cod larvae in intermediate and good nutritional condition showed similar values of FA, and these were more symmetric than for larvae in poor condition. As increased levels of FA were restricted to larvae in a condition comparable to that of larvae experiencing at least 3 days of starvation in laboratory experiments, it is suggested that FA is an insensitive indicator of short-term feeding success of larval cod. However, FA can be used to reveal severely starved larva populations and probably also populations that have been subjected to prolonged sub-optimal feeding conditions.     

Effect of sexual maturation on the tissue biochemical composition of<Emphasis Type="Italic"> Octopus vulgaris</Emphasis> and<Emphasis Type="Italic"> O</Emphasis>.<Emphasis Type="Italic"> defilippi</Emphasis> (Mollusca: Cephalopoda)

Changes in the protein, lipid, glycogen, cholesterol and energy contents, total amino acid and fatty acid profiles of Octopus vulgaris and O. defilippi tissues (gonad, digestive gland and muscle) during sexual maturation (spermatogenesis and oogenesis) were investigated. Both species showed an increase of amino acids and protein content in the gonad throughout sexual maturation (namely in oogenesis), but allocation of these nitrogen compounds from the digestive gland and muscle was not evident. The major essential amino acids in the three tissues were leucine, lysine and arginine. The major non-essential amino acids were glutamic acid, aspartic acid and alanine. With respect to carbon compounds, a significant increasing trend (P<0.05) in the lipid and fatty acid contents in the three tissues was observed, and, consequently, there was also little evidence of accumulated lipid storage reserves being used for egg production. It seems that for egg production both Octopus species use energy directly from food, rather than from stored products. This direct acquisition model contrasts with the previous model for Octopus vulgaris proposed by ODor and Wells (1978: J Exp Biol 77:15–31). Most of saturated fatty acid content of the three tissues was presented as 16:0 and 18:0, monounsaturated fatty acid content as 18:1 and 20:1 and polyunsaturated fatty acid content as arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3). Though cholesterol is an important precursor of steroid hormones, this sterol content exhibited variations that do not seem to be related with the maturation process. Moreover, significant differences (P<0.05) were obtained between genders, suggesting that perhaps there is a greater physiological demand for cholesterol during spermatogenesis than oogenesis. If the component sterols of octopus are of a dietary origin, considerable variation in the cholesterol content between species might be expected on the basis of the sterol composition of their prey. The glycogen reserves increased significantly in the gonad and decreased significantly (P<0.05) in the digestive gland and muscle of O. vulgaris (these trends were not evident in O. defilippi). Glycogen may play an important role in the maturation process and embryogenesis of these organisms, because carbohydrates are precursors of metabolic intermediates in the production of energy. It was evident that sexual maturation had a significant effect upon the gonad energy content, but the non-significant energy variation (P>0.05) in the digestive gland and muscle revealed no evidence that storage reserves are transferred from tissue to tissue. The biochemical composition of digestive gland and muscle may not be influenced by sexual maturation, but rather by other biotic factors, such as feeding activity, food availability, spawning and brooding.Communicated by S.A. Poulet, Roscoff     

Reproductive strategy of<Emphasis Type="Italic"> Calanoides carinatus</Emphasis> and<Emphasis Type="Italic"> Calanus helgolandicus</Emphasis> during a summer upwelling event off NW Spain

Reproductive activity and production of the calanoid copepods Calanus helgolandicus and Calanoides carinatus were measured during a summer upwelling event off the coast of NW Spain. The upwelling pattern affected the distribution and fecundity of both species in the study area. The demographic composition of both populations and the stage of gonad maturation (e.g. the high abundance of fertilised females with mature ova) indicated active reproduction. C. carinatus, a highly fecund species associated with the African upwelling zones and considered as an upwelling specialist, showed low production rates (overall means of 15 eggs female^–1 day^–1 and 3% body C day^–1), despite the fact that the food conditions (high phytoplankton biomass dominated by diatoms) seemed to be optimal for this species. By contrast, C. helgolandicus, a temperate species that shows a strong link between spring phytoplankton blooms and reproduction time, seems to be flexible enough to take full advantage of shorter-term, enhanced feeding conditions associated with the pulsed nature of the summer coastal upwelling. Both the egg and carbon-specific production rates attained by this species (overall means of 26 eggs female^–1 day^–1 and 12% body C day^–1) were similar to values reported for a spring bloom situation. This high production would imply a long spring–summer recruitment event of C. helgolandicus in these waters. For both species the stage of gonad maturation was significantly correlated with their egg production rates and likely influenced by the food conditions; a species-specific nutritional requirement for final oogenesis is suggested. The carbon condition factor (carbon weight/prosome volume) of C. carinatus females was higher than that of C. helgolandicus, suggesting differential use of the carbon ingested; C. helgolandicus seems to use all ingested carbon to produce eggs at a high rates, whereas C. carinatus seems to store part of the ingested carbon as lipid reserves to ensure female survival and to support production during subsequent unfavourable food conditions.Communicated by S.A. Poulet, Roscoff     

Feeding selectivity in larvae of the European hake (<Emphasis Type="Italic">Merluccius merluccius</Emphasis>) in relation to ontogeny and visual capabilities

Feeding ecology was analysed for the first time in the larvae of the European hake (Merluccius merluccius) to determine whether their diet and selectivity were constrained by environmental conditions and how these feeding characteristics were related to ontogeny, prey availability and visual capabilities. Larvae collected during both day and night were analysed, and it was found that feeding incidence was high, regardless of the time of day. Examination of the visual system corroborated the hypothesis that hake larvae should be able to cope with a wide range of photic conditions and to forage even at low light intensity. A clear preference for adult calanoid copepods and, especially, for Clausocalanus spp. was observed in all sizes analysed. Prey number increased with larval size, but prey size did not. This finding indicates that hake larvae behave as selective and specialist predators that consume an increasing number of prey rather than larger prey during larval growth.     

Lipid and protein utilisation during early development of yellowtail kingfish (<Emphasis Type="Italic">Seriola lalandi</Emphasis>)

The pelagic yellowtail kingfish Seriola lalandi has become a target species for aquaculture in Asia and Australasia. Australasian production is reliant on larviculture from eggs of captive brood stock; however, knowledge regarding the nutritional requirements of larvae of this species is still scarce, particularly in relation to lipids. As a first step in establishing these requirements, eggs and larvae from captive S. lalandi brood stock were examined for differences in total protein, total lipid and lipid classes between individual spawning events, over the spawning season, and during larval development from fertilisation to 15 days post hatch. Results indicate that total protein egg⁻¹ varied significantly between individual spawning events within a season, but neither total lipid nor total protein egg⁻¹ varied significantly across the spawning season. Brood stock egg lipids were made up of approximately 60% phospholipid, 25% wax and/or sterol esters (WE), 15% triacylglycerol (TAG), and small amounts of sterols and free fatty acids. During the early larval period, both WE and TAG were utilised concurrently for energy. The larvae experienced very high mortality around 5–7 days post hatch, which coincided with very low levels of all neutral lipid classes. Although many other factors may also influence larval mortality, these results indicate that lipid provisioning may be an important factor in larval survival during the critical period around first-feeding in this species. Examination of ratios of TAG:ST, often used as a condition index in fish larvae, suggested that some of the larvae were suffering from starvation. However, as egg-derived WE appears to provide a significant source of energy during the early larval period in S. lalandi, it is suggested that WE should be included in any index of larval nutritional state.     

Diet of 0-group stages of capelin (<Emphasis Type="Italic">Mallotus villosus</Emphasis>), herring (<Emphasis Type="Italic">Clupea harengus</Emphasis>) and cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) during spring and summer in the Barents Sea

Recruitment of capelin in the Barents Sea fail when juvenile herring and cod are abundant and the potential for feeding competition of wild sympatric capelin and herring larvae and small cod juveniles were investigated. The frequency of gut evacuation after capture of capelin larvae were also studied in mesocosms. Small capelin larvae (<35 mm length) fed on small prey including phytoplankton, invertebrate eggs and nauplii, bivalves, other invertebrate larvae and small copepods. Calanus copepodites were only observed in large capelin larvae (>26 mm length). Calanus copepodites were the major food sources for contemporary herring larvae (25–35 mm length) and Calanus and euphausiids were the major prey for small juvenile herring (37–60 mm length) and cod (18–40 mm length). Capelin larvae reared in mesocosms evacuated the guts shortly after capture. Capelin larvae had a smaller mouth and fed on smaller prey than herring and cod of the same length. This implies that the small capelin larvae, in contrast to sympatric small herring and cod, are not tightly linked to the food chain involving Calanus and euphausiids. Thus, exploitative competition between capelin larvae and planktivorous fish that rely on Calanus and euphausiids in the Barents Sea may be relaxed.     

Histological investigation of the reproductive cycles of the limpets <Emphasis Type="Italic">Patella </Emphasis><Emphasis Type="Italic">vulgata</Emphasis> and <Emphasis Type="Italic">Patella ulyssiponensis</Emphasis>

This study devised a staging system for, and monitored, the gonad development of the limpet species Patella vulgata and Patella ulyssiponensis on the South West coast of Ireland using histological techniques. Maturation began in the males of both species in January and in the females it began in March. There was no statistical difference in gonad development between sexes and between species. Spawning in the male P. vulgata occurred from September to December 2003 and in September and October 2004. In female P. vulgata spawning occurred from October to December 2003, no spawning of females was observed in 2004. In male P. ulyssiponensis spawning occurred in November and December 2003 and from September 2004 to December 2004. Spawning was observed from November 2003 to January 2004 and in September 2004 in female P. ulyssiponensis. Sex ratios also varied between the species and between months sampled. Nevertheless more males were observed in both species.     

Effect of lipid emulsions on production and fatty acid composition of eggs of the scallop<Emphasis Type="Italic"> Argopecten purpuratus</Emphasis>

The impact of supplementing lipid emulsions rich in eicosapentaenoic acid (EmEPA), docosahexaenoic acid (EmDHA) or saturated fatty acids (EmCOCO) to a standard algal diet [3:1 mixture of Isochrysis galbana (T-iso) and Chaetoceros neogracile, St-diet] on Argopecten purpuratus broodstock was evaluated. Broodstock fecundity was compared as well as the egg quality in terms of lipid content, fatty acid composition and lipid class distribution. Fecundity was defined as the number of eggs released in the spawning process, since spawning was virtually complete. Results indicated that the total lipid content of the eggs of A. purpuratus was diet independent. A greater energy reserve was spent on a larger number of oocytes and not on bigger sized oocytes with a higher lipid content. The lipids supplied through the emulsions were at least partially allocated to the eggs, demonstrating that the fatty acid composition of the eggs could be manipulated, especially the neutral lipid fraction. Levels of EPA changed more rapidly than DHA levels, supporting the observation that they fulfilled an energetic and structural role, respectively. The St-diet supplemented with 50%EmCOCO resulted in a significantly higher fecundity compared to the algal diet supplemented with 25%EmEPA+25%EmDHA and the non-supplemented algal diet. It would seem that saturated fatty acids (SAFA) were more easily or preferentially incorporated in the female gonads of A. purpuratus. The relative content of SAFA and 18:2( n-6) in these eggs rose significantly. The relative content of the highly unsaturated fatty acids, EPA and DHA, on the other hand was substantially lower in the neutral lipid fraction, but hardly affected in the polar lipid fraction. It appeared that the maintenance of an adequate DHA/EPA ratio (approximately 1.2) was more important than the absolute levels of the two fatty acids, as long as a threshold value was reached.     

Fecundity,brood loss and egg development through embryogenesis of <Emphasis Type="Italic">Armases cinereum</Emphasis> (Decapoda: Grapsidae)

The present work is a comprehensive study of reproduction and embryonic development of Armases cinereum. Ovigerous A. cinereum (Bosc, 1802) females from Sebastian Inlet, Florida (9.88–19.4 mm CW) lay 2,000–12,000 eggs per brood, depending on their CW (mm): fecundity = 24.662 CW^1.9432. A. cinereum displayed significant brood loss through development (ca. 500 eggs per brood) independently from their CW (no senescence). However, since smaller females lay fewer eggs than larger ones, the percentage of eggs lost during embryonic development is greater in smaller females. The number of eggs carried on a later stage of development (potential fertility = 5.5593 CW^2.4417) is a more accurate estimate of the reproductive output and subsequent recruitment. Egg volume increased during development (64%, 0.025–0.041 mm³ or 0.36–0.43 mm of diameter, N = 270) and was strongly correlated with egg water content increase (19.21%, r = 0.89). Lipids, particularly fatty acids, seem to be the major energy source for embryonic development, decreasing 56.31 and 37.08% (respectively) during embryonic development; both are negatively correlated with egg volume (r = −0.90). The utilization of fatty acids through the different developmental stages of A. cinereum is presented. The most consumed fatty acids are the monounsatured (43.33 μg mg⁻¹ dw), followed by the saturated (29.91 μg mg⁻¹ dw) and polyunsaturated (24.03 μg mg⁻¹). Palmitic (16:0) and linoleic (18:2n-6) acids are preferentially consumed (19.5 and 17.9 μg mg⁻¹ dw, respectively). The high proportion of essential polyunsaturated fatty acids of C₁₈ and C₂₀ reflects the consumption of primary producers such as mangrove leaves. EPA/DHA ratio (2.85–3.84) and low DHA content indicated that this species appears in a medium-low level of the trophic chain. The low ratio of 18:1n-7/18:1n-9 and high percentage of 18:1n-9 (marker of carnivory) may be a sign of the consumption of juvenile invertebrates. The high percentage of odd-numbered FA indicated the occurrence of detritivores/scavenger behaviours. The fatty acid composition of the eggs reflects adult feeding ecology (omnivorous) and habitat.     

Maternal provisioning for larvae and larval provisioning for juveniles in the toxopneustid sea urchin <Emphasis Type="Italic">Tripneustes gratilla</Emphasis>

Lipid and protein biochemistry of eggs (84 μm in diameter), embryos and early larvae of the tropical echinoid Tripneustes gratilla (Linnaeus 1758) were quantified to determine how maternal provisions are used to fuel development of the echinopluteus. The eggs contained a mean of 30.82 ng lipid and 87.32 ng protein. Energetic lipids were the major lipid component (55.52% of total lipid) with the major class being triglyceride (TG: mean 15.9 ng, 51.58% of total). Structural lipid was dominated by phospholipid (PL: mean 11.18 ng, 36.26% of total). Early embryogenesis was not a major drain on egg energetic lipid and protein. Development of the functional feeding larva used ca. 50% of initial egg energetic lipid and most of this was TG. Maternal TG was still present in the 8-day echinoplutei and it was estimated that this energetic lipid would be depleted in unfed larvae by day 10. There was no change in PL. In a separate experiment lipid biochemistry of rudiment stage larvae and early developing juveniles were quantified to determine how lipids are used during metamorphosis. Fed larvae accumulated lipid (mean 275.49 ng) with TG and PL being the major energetic and structural lipids, respectively. Larval lipid stores were not appreciably depleted by metamorphosis and so were available for the early benthic stage juvenile. Juveniles started their benthic existence with 314 ng total lipid (TG: mean 46.84 ng, 14.9% of total, PL: mean 137.51 ng, 43.67% of total). Nile Red histochemistry and histology showed that the stomach serves as a nutrient storage organ and, that lipid stores accrued by larvae sustain developing juveniles for up to 4 days post settlement. Triglyceride supported both non-feeding stages of development and the prefeeding larval and perimetamorphic benthic stage. In this first study of lipid stores in settlement stage echinoderm larvae, we show that T. gratilla larvae sequester the same major energetic lipid (TG) to support the early juvenile that the female parent provided them to fuel early development.     

Trophic variation with length in two ommastrephid squids, <Emphasis Type="Italic">Ommastrephes bartramii</Emphasis> and <Emphasis Type="Italic">Sthenoteuthis oualaniensis</Emphasis>

From 1998 to 2001 a total of 200 Ommastrephes bartramii (27 paralarvae) and 170 Sthenoteuthis oualaniensis (14 paralarvae) were sampled from the Central North Pacific. One group of non-paralarval O. bartramii (n = 30) was sampled from farther northwest in 1996. The δ¹⁵N of mantle muscle of non-paralarval O. bartramii ( = 12.4‰) was significantly greater than that of non-parlarval S. oualaniensis ( = 8.1‰) (P < 0.001). The δ¹⁵N of whole paralarvae of O. bartramii ( = 6.4‰) was not significantly different than parlarvalae of S. oualaniensis ( = 6.1‰) (P = 0.528). There was no significant difference between the mantle muscle δ¹⁵N values of male (n = 95, = 13.3‰) and female (n = 18, = 12.9 ‰) O. bartramii greater than 300 mm mantle length (ML) (P = 0.15). There was also no significant difference between the mantle muscle δ¹⁵N values of male (n = 15, = 7.2‰) and female (n = 26, = 7.3 ‰) S. oualaniensis in the same size range (P = 0.41). Overall there was a distinct logistic increase in δ¹⁵N with mantle length for O. bartramii, whereas S. oualaniensis showed an exponential increase in δ¹⁵N with mantle length that was stronger within individual years than with all samples combined. In general, adult O. bartramii are more than a trophic level above S. oualaniensis (4.3‰, 1.3 TLs). Because of the nature of the sampling protocol, this study could not separate spatial and temporal effects on the δ¹⁵N signals from each squid species. This study demonstrates the ability of stable isotope analyses to differentiate trophic levels between squid species as well as track trophic changes across size ranges from paralarvae to adults. Additional research is needed to validate these trophic changes across size within individuals.     

Lipid composition of yellowtail flounder (<Emphasis Type="Italic">Limanda ferruginea</Emphasis>) in relation to dietary lipid intake

Condition indices (CI), hepatosomatic indices (HSI) and proximate, lipid and fatty acid composition of wild and laboratory-reared yellowtail flounder (Limanda ferruginea) (Storer, 1839) were compared from data taken throughout spring and summer 1996–1998. Cluster analysis was performed on the fatty acid signatures of these two groups along with a commercial diet and several invertebrate species to determine possible feeding patterns in Conception Bay, Newfoundland. HSI and levels of storage fat were significantly higher in the muscle and liver of laboratory-reared yellowtail flounder, indicating an efficient absorption of dietary lipid and an increase in fat deposition. Fatty acid analysis of the liver showed that wild fish contained significantly higher proportions of the essential fatty acids 20:46, 20:53 and 22:63; whereas proportions of 18:1 and 18:26 were significantly higher in all fractions of lipid examined from laboratory-reared fish than they were from wild fish. Polar fractions of lipid were more similar than the neutral fraction of lipid when comparing wild and laboratory-reared fish. Taken together, the differences in CI, HSI, proximate and fatty acid composition suggest that feeding commercial diets to L. ferruginea can cause changes in patterns of lipid deposition and metabolism. Cluster analysis of marine plankton, sedimenting particulate matter, wild invertebrates, the commercial diet and fish tissues showed that the fatty acid signatures of both wild and laboratory-reared yellowtail flounder closely resembled their respective food items. Fatty acid signatures from wild fish were more closely related to plankton and settling particulate matter, suggesting relatively few steps in the food web leading to yellowtail flounder. In addition to the resemblance between fatty acids in the commercial diet and the tissues of laboratory-reared yellowtail flounder, these fish had similar fatty acid signatures to those of wild invertebrates.Communicated by J.P. Grassle, New Brunswick     

Sand and wave induced mortality in invasive (<Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis>) and indigenous (<Emphasis Type="Italic">Perna perna</Emphasis>) mussels

The ability of an invasive species to spread in a new locality depends on its interaction with the indigenous community and on variation in time and space in the environment. The Mediterranean mussel Mytilus galloprovincialis invaded the South African coast 30 years ago and it now competes and coexists with the indigenous mussel Perna perna. The two species show different tolerances to wave and sand stress, two of the main environmental factors affecting this intertidal community. P. perna is more resistant to hydrodynamic stress than M. galloprovincialis, while the invasive species is less vulnerable to sand action. Our results show that mortality rates of the two species over a period of 6 months had different timing. The indigenous species had higher mortality than M. galloprovincialis during periods of high sand accumulation in mussel beds, while the pattern reversed during winter, when wave action was high. A negative correlation between sand accumulation and attachment strength of the two mussels showed that sand not only affects mussel mortality through scouring and burial, but also weakens their attachment strength, subjecting them to a higher risk of dislodgement. Here we underline the importance of variations in time and space of environmental stress in regulating the interaction between invasive and indigenous species, and how these variations can create new competitive balances.     

Genetic evidence fails to discriminate between <Emphasis Type="Italic">Macroramphosus gracilis</Emphasis> Lowe 1839 and <Emphasis Type="Italic">Macroramphosus</Emphasis><Emphasis Type="Italic">scolopax</Emphasis> Linnaeus 1758 in Portuguese waters

Fish belonging to the genus Macroramphosus are distributed throughout the Atlantic, Indian and Pacific oceans. Some authors consider this genus monotypic, Macroramphosus scolopax being the only valid species. Other authors consider (based on several morphological and ecological characters) that another species (Macroramphosus gracilis) exists and occurs frequently in sympatry with the first one. Intermediate forms are also reported in literature. In this paper, using the mitochondrial control region and the nuclear first S7 intron markers, we failed to find genetic differences between individuals considered to belong to both species as well as the intermediate forms. Our results suggest that in the northeastern Atlantic, Macroramphosus is represented by a single species, M. scolopax, with different morphotypes interbreeding in the sampling areas.     

Lipids and fatty acids of the benthic marine harpacticoid copepod<Emphasis Type="Italic"> Heteropsyllus nunni</Emphasis> Coull during diapause: a contrast to pelagic copepods

Many free-living copepods produce and store lipids prior to entering diapause (long-term dormancy). Heteropsyllus nunni Coull is the only marine harpacticoid copepod known to undergo any form of diapause. This study presents the first information on the types of lipids and fatty acids produced for long-term diapause in this benthic species. Sexually immature adults of H. nunni undergo diapause within a pliable self-made cyst. Prior to entering diapause (which lasts 3–4 months), they produce and store large amounts of orange lipid. The lipids apparently are utilized during diapause. Although some residual lipids remain, chiefly around the gonads, after the copepods emerge from their cysts, the lipid stores are visibly reduced. Typically, the copepods mate and produce eggs within 48 h after diapause is terminated. Light level and confocal laser scanning microscopy revealed that the lipid stores are distributed throughout the body in numerous oil droplets and not as a single oil sac, as seen in many marine calanoid copepods prior to overwintering (winter diapause). Transmission electron microscopy showed lipid spheres within the gut epithelium and large droplets of lipids stored extracellularly. Confocal laser scanning microscopy of copepods in pre-diapause, during diapause (encysted), post-diapause (recently excysted), and in reproductive condition, revealed that lipid stores are reduced following diapause, but are not totally absent. Analysis of lipid classes showed that H. nunni store predominantly wax esters/sterol esters (83% of total lipids) during diapause. The predominant lipid is most likely wax esters, as sterol esters typically are found only in small amounts in copepods. Fatty acid (FA) profiles of the copepods in diapause showed 16:0 to be most abundant followed by 16:1n-7 and 18:0; other FA occurred at concentrations <10% of total FA. Three polyunsaturated fatty acids (PUFA), 20:5n-3, 18:2n-6 and 20:4n-6, were found at concentrations <2% of total FA. These PUFA are "essential fatty acids" in H. nunni, obtained through dietary sources. The lipid classes and fatty acids present in H. nunni during diapause are compared to those of other copepods, some in a state of diapause and others not. It appears that lipid class and FA profiles are indicative of genetic makeup, type of diet or amount of food consumed prior to dormancy. Some classic paradigms of lipids and their association with copepod diapause are re-evaluated.Communicated by P.W. Sammarco, Chauvin     

Heart rate reflects osmostic stress levels in two introduced colonial ascidians <Emphasis Type="Italic">Botryllus schlosseri</Emphasis> and <Emphasis Type="Italic">Botrylloides</Emphasis><Emphasis Type="Italic">violaceus</Emphasis>

The influence of abiotic factors on the establishment and success of invasive species is often difficult to determine for most marine ecosystems. However, examining this relationship is critical for predicting the spread of invasive species and predicting which habitats will be most vulnerable to invasion. Here we examine the mortality and physiological sensitivity to salinity of adult colonies of the colonial ascidians Botryllus schlosseri and Botrylloides violaceus. Adult colonies of each species were exposed to abrupt changes in salinity (5, 10, 15, 20, 25, 30 psu) in the laboratory. Salinity ranges used in the laboratory corresponded with those of the field distributions of B. violaceus and B. schlosseri in the Great Bay Estuary, NH. Heart rate was used as a proxy for health to assess the condition of individual colonies. Heart rates were monitored daily for approximately 2 weeks. Results revealed that both species experienced 100% mortality after 1 day at 5 psu and that their heart rates declined with decreasing salinity. Heart rates of B. schlosseri remained consistent between 15 and 30 psu and slowed at 10 psu. Heart rates of B. violaceus remained constant between 20 and 30 psu, but slowed at 15 psu. These laboratory results corresponded to the distribution of these species in estuaries, indicating salinity is a key factor in the distribution and dominance of B. schlosseri and B. violaceus among coastal and estuarine sites. Furthermore, physiological differences to salinity were found between colonies of B. schlosseri in the Venetian Lagoon and colonies in Portsmouth Harbor, suggesting adaptation to environmental variables.     

Differential feeding of worker larvae affects caste characters in the Cape honeybee,<Emphasis Type="Italic"> Apis mellifera capensis</Emphasis>

Sections of brood from colonies of the Cape honeybee ( Apis mellifera capensis), the African honeybee ( A. m. scutellata), and hybrid bees of the two races were exchanged between colonies to study the effect of different brood-origin/nurse-bee combinations on development of caste characters. When Cape larvae were raised by African workers the amount of food provided almost doubled in comparison with Cape larvae reared by their own workers. In contrast, African larvae raised by Cape workers were provided with only half the amount they received from their own workers. After the bees emerged, we found a large degree of plasticity in characters related to caste differentiation, which corresponded closely to the amount of food provided. Super-fed Cape bees had enlarged spermathecae, were heavier than normal workers and developed more rapidly, and had reduced pollen combs, all typical for a more queen-like condition. Ovariole numbers did not appear to be enhanced by additional feeding. Cape bees that behave as social parasites in African bee colonies were most queen-like in the characters studied, albeit within the range that was found for Cape bees from normal colonies, suggesting within-colony selection for characters that enhance reproduction.Communicated by R. Page     

Ontogeny of space use and diet of two temperate damselfish species, <Emphasis Type="Italic">Parma microlepis</Emphasis> and <Emphasis Type="Italic">Parma unifasciata</Emphasis>

Studies of reef fish herbivory have mainly focused on the impacts and behaviour of adults of tropical species. In this study, the ontogenetic shifts in home range, aggression, feeding rate, diet and gut morphology in juveniles and adults of two temperate territorial damselfishes, Parma microlepis and Parma unifasciata, were determined. Both P. microlepis and P. unifasciata juveniles under 80 mm TL exhibited no aggressive chases towards conspecifics or other species, while above 80 mm TL aggressive chase frequency increased in conjunction with an increase in home range, defended as a territory. Ontogenetic diet shifts, characterised by an increase in herbivory (P. unifasciata: juveniles: 64% plant material, adults: 95% plant material; P. microlepis: juveniles: 43% plant material, adults: 67% plant material) were observed for both species. The ratio of digestive tract length to body length, which often accompanies a switch to herbivory, increased significantly with ontogeny for both species. Compared to tropical confamilial grazers, these temperate damselfish species feeding rates were lower, and they had larger territories which were not as strongly defended (fewer aggressive chases).