Fed Artemia Nauplii Research Articles

Brycon amazonicus larviculture cannibalism is reduced in biofloc systems

This study evaluated matrinxã Brycon amazonicus larviculture performance at different total suspended solid (TSS) concentrations in a biofloc technology (BFT) system, for 5 and 10 days. Larvae 24 h after hatching were used at a stocking density of 10 larvae L−1 for 10 days in four treatments: clear water (CW – control, 100% water renewal per day and no bioflocs), and three TSS concentrations in BFT systems: Low BFT (BFTL) - up to 200 mg L−1, Medium BFT (BFTM) - 200 to 350 mg L−1 and High BFT (BFTH) - 350 to 500 mg L−1. The matrinxã larvae were fed artemia nauplii until the 5th day and artemia nauplii plus mash feed containing 55% crude protein from the 6th to the 10 th day. Water quality, performance, morphology, and type II cannibalism (complete larvae ingestion) (n = 30) were evaluated after 5 and 10 days. Water quality, although altered, remained within the appropriate matrinxã limits in all treatments, with about a 90% water consumption decrease observed in the BFT systems. The BFT treatments resulted in larval survival increases of over 170% compared to the CW group, at 5 (p < 0.05) and 10 (p < 0.05) days of rearing, with CW = 31.4 and 17.9%; BFTL = 81.5 and 39.4%; BFTM = 88.9 and 59.9% and BFTH = 87 and 53.5% respectively. Larvae growth (p < 0.05) and morphological development (p < 0.05) at 5 days were lower in the BFTH treatment, due to the presence of more developed cannibalistic larvae compared to the other treatments, evidencing greater predation capacity. Cannibalism was observed after 5 and 10 days in all treatments, except for the BFTH group at 5 days and BFTM group at 10 days, proving the influence of high TSS levels and, consequently, turbidity, in reducing this behavior. The findings reported herein indicate matrinxã larviculture BFT system efficiency and suggest the use of TSS concentrations between 200 and 350 mg L−1 as an alternative to reduce cannibal behavior and increase matrinxã productivity, in addition to maintaining good quality and reducing water use.

Enhancing survival of ex-situ reared sexual recruits of Acropora palmata for reef rehabilitation

Acropora palmata is one of the major reef-building coral species in the Caribbean. The species has suffered drastic declines in abundance and sexual recruitment over the past decades. One method for active rehabilitation of A. palmata reefs is by assisting the production of sexual recruits under controlled lab conditions. Within this study, the effect of different aquaculture regimes and culturing periods on the survival rates of these recruits was investigated. In August 2016, coral spawn was collected on a reef nearshore New Providence, Bahamas, cross-fertilized, and reared in mobile laboratory facilities from Van Oord Dredging and Marine Contractors. Larvae were settled on pre-conditioned aragonite plugs.Sexual recruits were cultured under four different aquaculture conditions: ambient vs. high Total Alkalinity (TA) (∼2.8 mEq L−1 vs. 4.8 mEq L−1) and with vs. without feeding Artemia nauplii. Recruit size was monitored by tracking living tissue area and the number of polyps of a subset of recruits. Plates with recruits were outplanted to a nursery on the reef after 4, 9 and 14 weeks of aquaculture. Survival was determined during the aquaculture phase (at 4, 9 and 14 weeks after settlement), and after outplanting (at 27 and 44 weeks after settlement).During the aquaculture phase, survival was significantly lower in seawater with increased TA compared to ambient seawater conditions. The average number of polyps per recruit was significantly higher in the treatments with feeding. After outplanting to the reef, both survival and recruit size were highest in the feeding treatments. The most successful aquaculture treatment in this study was a combination of increased TA and feeding during 9 weeks of aquaculture, which resulted in a doubling of survival and recruit size at 10 months after settlement compared to ambient conditions. Ambient conditions did not enhance survivorship nor recruit size at 10 months after settlement, as compared to the other aquaculture treatments. Nevertheless, the success of ambient aquaculture conditions exceeded natural conditions, as no natural recruitment of A. palmata was observed in this study. We conclude that feeding during and ex-situ culture period enhances ex-situ growth rates and in situ recruit survival of A. palmata juveniles. No positive effects of the aquaculture treatment with only increased TA were found. Building on these results, recommendations are provided for future reef rehabilitation efforts using ex-situ rearing of sexually reproduced A. palmata recruits.

An effective method to mass culture a lobate ctenophore (&lt;i&gt;Bolinopsis mikado&lt;/i&gt;)

This paper reports an effective and easy method to culture the ctenophore Bolinopsis mikado. Fifteen adult B. mikado individuals were maintained in a kreisel tank, and fertilized eggs, which were detected in the following days, were all raised together in the same tank. From the early development stage to day 13, the B. mikado cydippid larvae were only fed Artemia nauplii. The cydippid larvae were able to easily catch the Artemia nauplii excreted by adult B. mikado; therefore, they were considered capable of growing on excrement. Adult B. mikado individuals were removed from the tank when the cydippid larvae reached approximately 5 mm in length (day 14). The cydippid larvae were then transferred to a circular tank with a water spray chamber. Approximately 21 days after the early development stage, cydippid larvae had grown to lengths of approximately 20 mm and were then bred in the same manner up to the 5th generation. The greatest advantages of this culture method are that it is less cumbersome and only requires feeding and observation until the cydippid larvae attain a size that enables them to pursue live Artemia nauplii. Thus, damage to the living body due to water exchange and the labor involved are reduced, thereby allowing stable breeding of B. mikado.

Development of an artificial breeding and hatchery technique for exotic ornamental fish &lt;i&gt;Sahyadria denisonii&lt;/i&gt; (Day, 1865)

Sahyadria denisonii is one of the highly demanded exotic ornamental fish species. Development of artificial breeding technique for Sahyadria denisonii is important under local conditions. The captive breeding of this species did not occur under the environmental manipulation method used in the present study. However, breeding was successful, when Ovaprim hormone was injected at 0.5 ml per kg of body weight of the female at 9 h latency period. Average number of eggs laid was 216±33 and average egg size at maturity was 1.6±0.2 mm. Duration of development of eggs to hatchling was 36 h from time of fertilization. Feeding Artemia nauplii as an initial feed resulted a significantly higher growth (P<0.05) while micro-worm fed hatchlings exhibited significantly high survival rate. Therefore, results of this study revealed that a single dose of Ovaprim at 0.5 mL/kg of BW of females and half of that dose for males can be used for breeding of S. denisonii. Artemia nauplii, and micro-worm larval feeds can be used as the starter feeds for S .denisonii post-larvae.

Inter- and intra-individual variability in growth and food consumption in pikeperch,Sander luciopercaL., larvae revealed by individual rearing

We examined short-term, inter- and intra-individual variability in rates of growth and food consumption in fish early life stages to gain a mechanistic understanding of why larvae in the same environments often grow at vastly different rates. We made parallel measurements of growth rate in standard length (GRSL) and food consumption rate (C), and provide estimates of weight growth rate (GRDW) and gross growth efficiency (GGE = 100*GRDW/C) of individually reared larvae of pikeperch, Sander lucioperca L., fed Artemia nauplii at 20°C and a salinity of 2.0 g L−1. Within two trials, GRSL, C and GGE were obtained for 108 larvae over a maximum period of 28 days. Mean (±SD) initial size, GRSL, C and GGE were 19.49 (9.19) mm, 0.68 (0.21) mm day−1, 0.85 (0.44) mg day−1 and 36.5 (10.2)% respectively. The vast majority (91%) of the variability in growth was explained by differences in food consumption. When isolated from conspecifics for 28 days, relatively small larvae grew faster than relatively large ones, partially mitigating initial differences in size-at-age.

Larviculture of two neotropical species with different distributions in the water column in light- and dark-colored tanks

The influence of tank color on the visual perception of fish larvae and the success of their cultivation depends on the characteristics of each species combined with environmental factors. In this study, we determined the effect of light and dark tank colors on the larviculture of pacamã (Lophiosilurusalexandri), a species with a benthonic habit, and curimatá-pioa (Prochilodus costatus), which swims actively in the water column. Larvae of pacamã and curimatá-pioa were cultivated for 10 days in 5-L tanks, at a density of 15 larvae L-1 and luminosity of 141.7 ± 8.95 lux, and fed Artemia nauplii. Four tank colors were used: green, light blue, brown, and black (with four replications). Survival, biomass and Fulton's condition factor for pacamã larvae were similar in the different colored tanks. However, the larvae in the green tanks showed lower weight than those cultivated in black and brown tanks, as well as shorter total length than that of larvae in the brown-colored tanks. These results are probably due to the association between tank color and benthonic habitat of the pacamã. For the curimatá-pioa, survival and biomass were similar for the different colors. The weight and Fulton's condition factor were higher for the larvae cultivated in green and blue tanks. This result could be associated with the adaptation of curimatá-pioa larvae to active swimming in the water column, searching for prey.

Ontogenetic variation of food intake and gut evacuation rate in larvae of the doncellaPseudoplatystoma punctifer, as measured using a non-destructive method

Food intake (FI) and gut evacuation (Rg) were measured in larvae of Pseudoplatystoma punctifer (4.5–18.4 mm SL) fed Artemia nauplii, taking advantage of the translucence of their abdominal region to achieve this in a non-destructive way, using digital photographs and mathematical reconstruction of gut volume content (ellipsoidal and cylindrical models for stomach and intestine respectively). The inaccuracy of the method, with reference to counts of nauplii following fish dissection, was low (2.9 ± 1.5%) and independent of fish size (P = 0.6153). Pigmentation hampered measurement in fish >18–19 mm SL. Anaesthesia was needed in fish >9.5 mm SL, thereby preventing the measurement of Rg in individual fish. The FI increased rapidly during the ontogeny, passing from <7% M at 0.6 mg, to 14% M at 1 mg and 21% M at 15–40 mg, and then decreased slightly in larger fish. At 28.5°C, Rg (% M h−1) was modelled as Rg = −8.22 + 12.11 log FI + 6.30 log M – 12.67 (log M)2 (R2 = 0.904, d.f. = 27, with FI in% M and M in mg). Extrapolations of Rg over 24 h gave estimates of daily food rations that fit well with those measured in cannibalistic P. punctifer.

Effects of weaning age and diets on ontogeny of digestive activities and structures of pikeperch (Sander lucioperca) larvae

Growth and ontogeny of digestive function were studied in pikeperch (Sander lucioperca) larvae weaned on artificial food at different ages. Three weaning treatments initiated respectively on day 9 (W9), day 15 (W15) or day 21 (W21) post-hatching (p.h.) were compared with a control group, fed Artemia nauplii from first feeding until the end of the rearing trial on day 36 p.h. The digestive enzyme activities and the ontogeny of digestive structures were investigated using enzymatic assays and histological methods. Growth of pikeperch larvae was significantly affected by precocious weaning. Pancreatic (trypsin and amylase) and intestinal (leucine-alanine peptidase, leucine aminopeptidase N and alkaline phosphatase) enzyme activities were detected from hatching onwards, increased at the moment of first feeding and then decreased. Pepsin secretion occurred at day 29 p. h. only, concurrently with the stomach development and differentiation of gastric glands. In the early weaning group (W9) the maturation process of intestinal enterocytes seems to be impaired and/or delayed and several signs of malnutrition were recorded. Except for alkaline phosphatase activity, no differences in enzyme activities and development of digestive structures were observed among the control, W21, and W15 groups. Moreover, at the end of the experiment, no differences in proteolytic activities were observed among larvae from the different treatments, indicating that, in surviving individuals, the digestive structures were properly developed and the larvae had acquired an adult mode of digestion. Based on the artificial diet used, our results suggested that pikeperch larvae can be weaned from day 15 p.h. without significant adverse effect on digestive capacities (except for alkaline phosphatase) or development of digestive tract, while earlier weaning impaired the onset of the maturation processes of the digestive system, both in terms of morphological structures and enzymatic activities.

Larval Growth of the Coconut Crab Birgus Latro with a Discussion on the Development Mode of Terrestrial Hermit Crabs

Abstract With intensified harvesting and environment deterioration during the past two decades, a rapid decline in the number of coconut crabs, Birgus latro, which is a protected species listed in the IUCN Invertebrate Red Data Book, has occurred on many islands. Thus, it is important to protect this species by establishing conservation areas and/or replenish natural population by larval cultivation. In this study, the development modes were analyzed and the effect of enriched diet on larval growth and survival were examined. Two types of zoeal development patterns were found. In general, zoeae took 29-33 days to complete five zoeal stages and metamorphose to glaucothoes. However, some zoeae directly metamorphosed from the 3rd zoeal to glaucothoe stage in 25∼28 days. Morphologically, these zoeae with accelerated development had thoracic appendages that appeared like the fifth stage zoeae, but with the telson, antennule, and antenna similar to those of the third stage zoeae. When fed Artemia nauplii enrich...

Sunshine Bass Fingerling Culture

Year-round production is a top priority of hybrid striped bass producers.Most Morone culturists produce sunshine bass (white bass (♀) X striped bass (♂)) that have very tiny fry and require rotifers as their first food. Almost 100 percent of the fingerlings are produced in ponds where high survival rates depend on fry being stocked at the right time—before rotifer concentrations peak and before copepods appear. Pond culture drawbacks include the inability to monitor growth and survival and seasonal limitations due to weather. Tank culture overcomes these problems and is necessary for year-round production. Little tank fingerling production has occurred because costs are higher than for pond culture. Supplying live food is a major expense. Sunshine bass larvae are stocked at 4 to 5 days post hatch (dph) and are fed enriched cultured rotifers. The rotifers require microalgae. Within a few days the fry are weaned to cultured Artemia nauplii. The culture of the larger palmetto bass and striped bass starts with feeding Artemia nauplii. By about 15 dph, weaning to an artificial diet begins and is completed by 26 dph. Grading at that time reduces cannibalism. Live food culture is risky, and requires time, space, costs and expertise. Recent innovations may alleviate some of these problems. High density (up to 16,000 /ml) rotifer production methods are being developed. These systems require constant feeding, oxygen, pH and ammonia control, suspended particle removal, and proper harvesting. Fatty acid enriched algae pastes can replace cultured algae. Ammonia and pH problems can be controlled with products like Chloram-X® and auto-sensing pH controllers. Water is conserved by utilizing recirculation systems for rotifer and fingerling production. Use of commercially available decapsulated brine shrimp eggs further reduces time and physical risk. Increased demand for fingerlings during the winter and reduced culture costs will increase tank fingerling production.

Evaluation of oxytetracycline concentration in shrimp postlarval tissues offered through Artemia nauplii and medicated bath

In Mexico, oxytetracycline is commonly applied to shrimp larval rearing systems to control bacterial problems; however, it is not known how much oxytetracycline is incorporated by the shrimp. The present study aimed to measure the levels of oxytetracycline incorporated by Litopenaeus vannamei shrimp postlarvae offered by two different administration routes: bioencapsulated in Artemia franciscana nauplii and applied directly in the seawater. Five treatments were used: postlarvae medicated through conventional bath (20 ppt) and fed Artemia nauplii (BATH), postlarvae fed Artemia nauplii enriched with oxytetracycline (19 mg meal–1) and Rich®, a commercial lipid mix (R-OTC), postlarvae fed Artemia nauplii enriched with oxytetracycline (19 mg meal–1) (OTC), postlarvae fed Artemia nauplii enriched with Rich® (RICH), and postlarvae fed with Artemia nauplii (control). Treatments were applied for seven days and postlarvae from each treatment were sampled daily to measure the levels of oxytetracycline incorporated through high performance liquid chromatography (HPLC). Higher incorporation of oxytetracycline in the shrimp was found in the BATH treatment. Values did not vary much among days within the treatments. Rich® improved the amount of oxytetracycline incorporated by the shrimp. By day 7, the mean antibiotic determinations were as follows: OTC, 5.77 ± 0.6 ∞g g–1; Rich® + OTC, 18.98 ± 2.8 ∞g g–1; and BATH, 26.3 ± 8.1 ∞g g–1 of shrimp extract. An antibiotic dose of 4 times the minimum inhibitory concentration (MIC) is recommended in order to achieve therapeutic doses in the organisms to be treated. The results from the chromatography analysis on the shrimp body showed that only 0.15 of the MIC (303.98 ∞g mL–1) reported was in fact detected in the shrimp in the highest treatment. Oxytetracycline is water-soluble, and perhaps its bioencapsulation for treatment purposes is not feasible. As for the medicated bath, a higher concentration is required to achieve a therapeutic dose in the shrimp tissues.

Histological changes induced by dietary phospholipids in intestine and liver of common carp ( Cyprinus carpio L.) larvae

Histological observations were made in common carp larvae in order to understand the origin of the phospholipid (PL) requirement of fish during their young stages. Larvae were fed for 6 or 8 days after start-feeding on semi-purified diets containing peanut oil and supplemented with or without different PL fractions enriched in phosphatidylcholine (PC) or phosphatidylinositol (PI). A group of larvae was also fed Artemia nauplii. Dietary PL deficiency was associated with an accumulation of fat droplets in the enterocytes of the anterior intestine, an increase in height of mucosal epithelium, a reduced total liver volume and mean hepatocyte volume. In contrast, diet supplementation with PC from hen egg yolk or from soybean prevented the intestinal steatosis and resulted in larger liver volume and larger hepatocyte volume. Larvae fed Artemia showed the same features as larvae fed PC-enriched diets. Hydrogenated PC also prevented the intestinal steatosis but resulted in small liver and hepatocyte size. Larvae fed PI-enriched diets exhibited intestinal steatosis, although less systematically than larvae fed PL-deficient diets, and reduced liver and hepatocyte size. Results support previous opinions that PL are needed for the absorption of neutral lipids although their beneficial effect appears to be independent of their emulsifying properties. The limiting stage seems to be the synthesis and exportation of chylomicrons or very low density lipoprotein (VLDL) by the enterocytes and not the intraluminal formation of micelles. PC appears to have a specific role for chylomicrons and VLDL synthesis and secretion, as in mammals. The reduced liver and hepatocyte size in the absence of PC could result from a decreased energy supply due to poor lipid absorption.

Amino acid profiles and amino acid utilisation in larval African catfish (Clarias gariepinus): effects of ontogeny and temperature.

The present study investigated the qualitative amino acid (AA) requirements of larval African catfish Clarias gariepinus. Yolk-sac larval AA profiles were measured at different temperatures and also in animals reared at 28 °C fed Artemia nauplii or an experimental dry diet. The AA profile of C. gariepinus larvae changed during ontogeny, especially before the start of exogenous feeding. The AA profiles of the food items (yolk, Artemia and the dry diet) differed considerably from that of the larvae. No selective absorption of yolk AA was detected. Higher temperatures led to increased absorption and depletion rates of AA, and also to a higher retention efficiency of yolk nutrients. However, changes in temperature did not induce preferential absorption or depletion of individual AA, and caused only small variations in the AA profile. Depletion rates of individual AAs varied, possibly due to differences between larval and yolk AA profiles, and also to changes in the larval AA profile during ontogeny. There was little regulation of catabolism of individual AA in yolk-sac and starved larvae, and no sparing of essential AA.

Application of soya phosphatidylcholine in tuna orbital oil enrichment emulsions for Artemia

Oil-seawater emulsions of 12%, 8%, 4% and 2% soya phosphatidylcholine (PC) in tuna orbital oil (TOO) (w:w) were tested with respect to their suitability as Artemia enrichment media. Levels of essential fatty acids (EFA) accumulated by feeding Artemia nauplii were measured after enrichment periods of 0, 14, 18 and 20 h, and the stability of polyunsaturated fatty acids levels in the emulsions were also monitored throughout the enrichment process. Artemia enrichment efficiency in terms of %DHA (docosahexaenoic acid, 22:6w-3) and DHA:EPA (eicosapentaenoic acid, 20:5w-3) ratios were similar for all four types of emulsions (10-12% and 1.7-1.8, respectively). However, 8% and 12% soya PC/TOO emulsions yielded nauplii with slightly higher mean lipid contents than the other two treatments (235-243 and 217-229 mg lipid g-1 dry body weight, respectively). Stability of polyunsaturated fatty acids (PUFA) levels within the emulsions in seawater, and of DHA and EPA levels in particular, correlated with soya PC concentration. In 12% soya PC/TOO emulsions, PUFA levels remained high after 20 h enrichment whilst those in the 2% and 4% soya PC emulsions showed a marked reduction by 18 h enrichment time. It is suggested that soya PC may protect PUFA levels in the emulsions in a dose-dependent manner, probably by acting as an antioxidant. No significant improvement in Artemia total lipid content or DHA:EPA ratio occurred when enrichment was continued for longer than 18 h. When using this enrichment system, it is preferable, therefore, to employ the 12% soya PC/TOO emulsion and to terminate the enrichment process at 18 h, thus preventing the risk of PUFA levels deteriorating in the emulsion.

Occurrence of an alternative pathway in the larval development of the crab Chasmagnathus granulata Dana, 1851 under laboratory conditions

Larvae of the crab Chasmagnathus granulata were collected in a salt marsh located in the Lagoa dos Patos, Brazil and reared from eclosion to metamorphosis under different dietary regimes. Larvae reared individually in beakers of 40 ml and fed Tetraselmis chuii (zoea III and zoea IV), showed a supplementary stage, here designated as zoea V, with morphological characteristics intermediary between zoea IV and megalopa. No zoeae V molted to megalopa stage. To confirm the occurrence of the supplementary stage, mass cultures of larvae of C. granulata were fed Artemia sp. at high densities, we again detected the fifth zoeal instar. However, when zoeae V were individually placed in beakers and fed Artemia nauplii, they succeeded in molting into megalopae. We observed the occurrence of two types of zoeae IV — a smaller type (from which originated the zoeae V) and a larger type (which directly developed into megalopae). We conclude that stressful nutritional/environmental conditions were responsible for the occurrence of this alternative path of development.

The prevalence of ruptured intestine syndrome in African catfish Clarias gariepinus (Burchell 1822) fed different rations when between 3 and 5 weeks old

The influence of feed type and feed quantity during early life stages of Clarias gariepinus on the subsequent occurrence of ruptured intestine syndrome (RIS) was investigated. Feed type related to live and dry feed, whereas feed quantities were set at 1 and 3 times the optimum feeding level of 8.4 g kg −0.8 day −1. Results indicate that feeding Artemia nauplii or low levels of dry feed before week 4 will significantly decrease the subsequent occurrence of RIS.

Acceptance and Consumption of Food by Striped Bass and Hybrid Larvae

AbstractFood acceptance, consumption and weaning times were investigated for striped bass (Morone saxatilis) and hybrid striped bass (M. saxatilis×M. chrysops) larvae. Experimental treatments consisted of: control groups of striped bass (SC) and hybrids (HC) fed Artemia nauplii; hybrids fed formula food (HF); and hybrids weaned from Artemia nauplii to formula food at 11–15 days (HF1), and 18–22 days (HF2) posthatch. The formula diet did not support growth and resulted in total mortality of the HF hybrids by the third week posthatch. HF1 fish had significantly slower growth and lower survival than HF2 of HC. The HF2, HC and SC groups had similar growth and survival, which indicated no heterosis in hybrids. There were no differences in Artemia nauplii consumption by the SC and HC groups. Daily consumption increased exponentially for both groups (0.8 to 50–60 cal/day/larva between 7 and 30 days posthatch). Weight specific consumption (WSC) decreased initially and then increased for both groups. A mean WSC of 58% (range of 24–83%) was found for the combined SC and HC groups. Food conversion ratio, growth efficiency, caloric efficiency, and productive protein values were similar for striped bass and hybrid larvae.

The influence of feeding on the metabolic activity of Antarctic krill (Euphausia superba Dana)

The influence of feeding on the metabolic activity of juvenile krill was assessed from 24h experiments in which krill were incubated with various concentrations of diatoms (Chaetoceros calcitrans, Phaeodactylum tricornutum, Thalassiosira eccentrica, Fragilariopsis vanheurkii), newly hatched Artemia nauplii and latex beads. Krill fed on the larger food more efficiently, with reluctant feeding on latex beads. Feeding of krill expressed as clearance rates was poorly correlated with their oxygen uptake rates. Instead, a positive correlation was found between the oxygen uptake rates and ingestion rate (except for latex beads). The result implies that the specific dynamic action is the major cause of the increased oxygen uptake of krill. Krill fed diatoms increased both ammonia and phosphate excretion with increasing ingestion rate, but only phosphate excretion was increased in parallel with ingestion rate for those fed Artemia nauplii. Assuming the daily ration of krill in the field is 5% of the body weight, and the major food source is phytoplankton, oxygen uptake, ammonia excretion and phosphate excretion rates of wild krill are estimated to be 1.6, 4.5 and 7.8, respectively, times the rates of non-feeding krill in 24h laboratory experiments. Krill offered various kinds of food showed different metabolic quotients (O/N, N/P and O/P ratios). While no functional relationship was seen between the metabolic quotient and the ingestion rate of krill fed Artemia nauplii, those fed Fragilariopsis showed a progressive decrease in O/N, N/P, and O/P ratios as their ingestion rates increased.

Depth regulatory behavior of the first stage zoea larvae of the sand crab Emerita analoga Stimpson (Decapoda: Hippidae)

Laboratory studies of the behavior of first stage zoea larvae of the sand crab Emerita analoga Stimpson have shown that while newly-hatched larvae are strongly photopositive, this response lasts only about four hours, as the larvae rapidly become photonegative. After becoming photonegative, a large proportion of the larvae remain so throughout the first four days of life if they are fed Artemia nauplii; if starved, the larvae become significantly more photopositive than when fed. Both the photopositive response of newly-hatched larvae and the reversal to photopositive behavior in response to starvation are only apparent under horizontal test conditions. Increases in hydrostatic pressure stimulate swimming activity among the larvae; responsiveness to pressure being greatest at hatching and decreasing thereafter. The pressure response is strongly oriented to light; pressure-stimulated larvae will swim towards a light source regardless of whether this involves upward, downward, or horizontal motion. Experiments suggest that the pressure response provides the primary mechanism for depth regulation among young larvae; gravity and light may augment the pressure ‘sense’ by serving as primary orientational cues. The nutritional status of an individual larva may alter its depth-regulatory capabilities, but this effect is not yet clear.

Seasonal changes in the free amino acid composition of the adult barnacle, Balanus Balanoides

1. 1. The total free amino acid (FAA) level in Balanus balanoides varied seasonally with a maximum level in the autumn and a minimum level in the spring. 2. 2. Proline, glycine, taurine, arginine, alanine, glutamic acid and serine were the most prominent free amino acids. The level of glycine showed a marked increase in November at the time of fertilization. Alanine had its highest level during the winter when food is sparse and feeding rates are reduced. 3. 3. Barnacles kept without food at 5° and 15°C from October to December had an increased FAA content compared with animals on the shore. There was a marked increase in the alanine content of animals kept at 15°C. 4. 4. Barnacles kept without food at 5°C from January to June had a lower FAA content than animals on the shore. Animals kept at shore temperatures and fed Artemia nauplii from mid-February onwards had a similar FAA content to the shore animals. 5. 5. A survey of aminotransferase activity in B. balanoides showed strong glutamate-pyruvate transaminase (E.C. 2.6.1.2) activity but no glutamate-oxaloacetate transaminase (E.C. 2.6.1.1) activity. Aminotransferases involving the amination of glyoxylic acid to glycine were found to be active.