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1.
Histological changes of the digestive tract were studied in shi drum (Umbrina cirrosa) from hatching until 41 days post hatching (dph), when the fry had a mean (±S.D.) total length (TL) of 32 ± 2 mm and wet weight (WW) of 0.42 ± 0.07 g. Larvae were reared using the mesocosm technique, the most natural among commercially employed rearing methods for marine larvae. Shi drum opened their mouth at 2 dph (2.78 ± 0.09 mm TL), at which time 90% of the larvae already had an inflated swim bladder. The differentiation of the digestive tract into buccopharynx, esophagus, and anterior and posterior intestine was completed by 3 dph (2.82 ± 0.07 mm TL), 1 day after the onset of exogenous feeding. The alimentary canal started coiling and formed its first loop at 2 dph, while the pancreas and liver were differentiated at 3 dph. Yolk sac reserves lasted until 7 dph (4.3 ± 0.1 mm TL), suggesting a brief period of endogenous and exogenous feeding. The first esophageal goblet cells appeared at 7 dph containing acid mucins and at 8 dph taste buds appeared on the buccopharyngeal epithelium. The stomach was morphologically differentiated at 9 dph (5.5 ± 0.1 mm TL) when gastric glands became abundant in the cardiac region, and the first pyloric caeca appeared at 14 dph (10.1 ± 0.9 mm TL). Supranuclear eosinophilic vacuoles were observed in the posterior intestine between 3 and 11 dph (6.3 ± 0.9 mm TL). Their number decreased as the stomach differentiated, suggesting a change in the protein digestion mechanism. The results of the study suggest a rapid development of shi drum and its digestive system and underline the possibility of weaning larvae to artificial feed even earlier than the 12 dph employed in the present study.  相似文献   

2.
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3.
Oogenesis of abalone Haliotis discus hannai was examined histologically during a single spawning season using broodstock of various maturation conditions, which were controlled by effective accumulative temperature (EAT). The quality of eggs spawned was determined in relation to oogenesis. For histological examinations, three to five females were sacrificed at 300, 600, 850, 1050, and 1150 °C days EAT, without induction of artificial spawning. Other females were successfully induced to spawn at 700 °C days EAT and were reared following spawning. Three of these females were then sacrificed every 200 °C days EAT until 1300 °C days EAT. Gonad histology showed that two oocyte cohorts matured in H. discus hannai ovaries during a single spawning season. One mature oocyte cohort could be spawned in multiple times. The second oocyte cohort started developing after the first oocyte cohort had been spawned or reabsorbed, and became fully mature 400 °C days EAT after the first cohort was depleted. For egg quality measurements, three to five females were successfully induced to spawn at 850, 1050, 1150, 1900, and 2350 °C days EAT (Experiment 1). Three females were induced to spawn twice, at 700 and 1500 °C days EAT, resulting in two batches of eggs from the same individuals (Experiment 2). Total lipid and protein content of eggs were measured and were greater in eggs from the second cohort than in eggs from the first cohort. No carbohydrates were detected in eggs and there was no difference in cytoplasm volume between the two cohorts. In hatcheries producing H. discus hannai, it is important to increase post-larval starvation tolerance by increasing the quality of eggs, to yield higher and more consistent survival. The results of this study suggest that H. discus hannai hatcheries should use eggs from the second oocyte cohort, which are of higher quality, rather than eggs from the first oocyte cohort.  相似文献   

4.
Cobia Rachycentron canadum is a fast-growing, pelagic marine species that has recently attracted aquaculturists in both the research and commercial sectors. The typical method of grow-out for this species is in outdoor systems where production is limited to locations and seasons conducive for adequate growth and survival. Expanding the culture of cobia to indoor recirculating aquaculture systems (RAS) would allow for the production of fingerlings throughout the year and extend production to cooler regions. Two rearing trials were conducted to examine the growth and survival of cobia from hatching through 4 (trial 1, T1) or 35 (trial 2, T2) g in RAS. Cobia larvae were reared in circular tanks placed in a raceway to control water temperature and quality. During early juvenile grow-out, fish were transferred without grading to a second raceway on 29 dph (T1) or over a period of grading from 29–43 dph (T2). Larval growth (1–22 dph) measured as standard length was similar for both trials ranging from  3.9 to 14.7 mm. However, larval growth measured as wet weight (0.033 g, T1; 0.026 g, T2) or dry weight (5.7 mg, T1; 3.9 mg, T2) was significantly greater on 22 dph during T1 as was the ratio between myotome height and standard length. These differences may have resulted from an increase in initial densities from 8.7 larvae l− 1 (T1) to 14.7 larvae l− 1 (T2) which apparently caused an increase in food competition and overall aggression. During juvenile grow-out, cobia reached 4.0 g on 43 dph in T1 and 35.4 g on 71 dph in T2 matching weights achieved during grow-out in outdoor ponds. Over the course of both trials, survival was similar to that reported in outdoor ponds. Mean survival (± S.D.) during the early rearing phase (hatching through 29 or 43 dph) averaged 13.2 ± 3.2 % and 10.4 ± 3.2 % corresponding to final densities of 0.9 ± 0.2 and 1.2 ± 0.4 fish/l for T1 and T2, respectively. During the first grow-out phase (29–43 dph), survival of fish moved into the open raceway was 64.5% in T1 and 88.7 % in T2. Survival of cobia during the second grow-out phase (43–71 dph) for T2 was 92.5%. The results of this study indicate that cobia can be successfully cultured in indoor systems from hatching through at least 35 g without negatively affecting growth or survival.  相似文献   

5.
This paper provides information on the early life stages of the Moroccan Atlantic sardine, Sardina pilchardus, and two species of Sardinella: Sardinella aurita and S. maderensis, between Cape Blanc (21°N) and Cape Boujdor (26°N), dealing with the spawning grounds, the nursery areas and the optimal spawning temperature and salinity range.

The spawning areas for Sardina are located North of Dakhla (24°30′–25°30′N) and near Cintra Bay (23°N). The larval development area is described together with seasonal and annual characteristics. The nurseries of Sardina are near Dakhla and to the south between 21 and 22°N but precise locations vary with season. The maximum occurrence of eggs was during winter, and was at temperatures from 16 to 18 °C in winter and between 18 and 18.5 °C in summer.

The main spawning area of Sardinella species is between Cape Blanc and Cintra Bay (21–23°N) with a maximum occurrence of eggs and larvae in July. For Sardinella off the southern region of Morocco, the optimal temperature interval for spawning is between 18 and 21.14 °C. No conclusions can be drawn on the relationship between spawning and water salinity.

The area north of Cintra Bay has a broad, but shallow continental shelf. This topography leads to decreasing dispersion effects and the zone constitutes a favorable area for larval retention and development.  相似文献   


6.
Successful natural spawning of Pomacanthus semicirculatus in captivity from 11 September to 18 October, 2006 is described for the first time. Each female laid an average of 230 000 eggs during the spawning period. Fertilized eggs were spherical, transparent and buoyant and had a mean diameter of 0.61 ± 0.03 mm (mean ± SD). Embryonic development lasted 18–21 h at 28.5 °C. Newly hatched larvae were 1.35 ± 0.02 mm in total length (TL) with 27 (12+15) myomeres and had an oil globule in the ventroposterior area of the yolk sac. Larvae completed yolk absorption within 3 days post hatching at 2.37 ± 0.05 mm TL. Larvae were fed either 100% microalgae ( Nannochloropsis sp.), 100% s-type rotifers ( Brachionus rotundiformis ), 100% dinoflagellates ( Gonyaulax sp.) or different combinations of the three (50%:50%:0%, 30%:35%:35%) to determine the effect of live feed on the survival rate. The survival was significantly ( P <0.001) better in larvae fed a combination of diets (30%: 35%: 35%) than others. These results indicate that P. semicirculatus is a potential species for captive-breeding programmes and the use of a combination of diets (microalgae plus s-type rotifers and dinoflagellates) may be a suitable first food for fish larvae.  相似文献   

7.
New Zealand turbot Colistium nudipinnis (Waite 1910) and brill Colistium guntheri (Hutton 1873) were studied to assess their potential for aquaculture development. The reproductive cycle of wild fish showed a long spawning season from winter to summer, during which it is possible to obtain gametes. Both species have a diurnal ovulatory cycle, and gamete collection, by stripping and fertilizing at sea, was most successful within 2–3 h before and after sunset. Male reproductive anatomy suggests that these flatfish spawn in close proximity and that pair formation is highly likely. The eggs of both species have multiple oil droplets, turbot eggs being slightly larger (0.99 mm diameter) with more droplets (18–55) than brill eggs (0.97 mm, 13–26 droplets). Hatching occurred approximately 84 h after fertilization at 14 °C. Newly hatched turbot averaged 2.2 mm in length, and brill averaged 2.1 mm. First feeding began 4 days post-hatch (DPH). During larval rearing, rotifers were replaced by Artemia nauplii at 10 DPH. Metamorphosis commenced at 12–15 DPH and was completed and the larvae settled by 45 DPH. Weaning to inert foods began at 20–22 DPH (50 mg weight) and was completed by 57 DPH. Survival of turbot was 22.8% from fertilized egg to hatching, 7.3% through incubation to 22 DPH and 2.1% through incubation to fully weaned juveniles. Weaning success for turbot from metamorphosis to 57 DPH was 31.5%.  相似文献   

8.
Development of the thyroid gland of the Japanese eel (Anguilla japonica) was studied with the use of tank-reared fish. A single thyroid follicle was first found in larvae at 29 days post hatching (dph), total length (TL) 12 mm. Until reaching 25 mm in TL (100 dph), leptocephali had one or two follicles per individual. The inner colloid of the follicles was weakly immuno-positive against the anti-thyroxine (T4) antibody. The number of thyroid follicles and the immunoreactivity later increased as the larvae grew. Thyroid hormones (TH) T4 and triiodothyronine (T3) were not detected in premetamorphic larvae by radioimmunoassays, but became detectable during metamorphosis. The maximum level of T4 was seen in fish at the end of metamorphosis and in just-metamorphosed juveniles, whereas T3 reached the highest level during metamorphosis and declined toward the end of metamorphosis. The results indicated that the thyroid gland first became active during metamorphosis in the development of eel.  相似文献   

9.
The nutritional response of Litopenaeus schmitti larvae to substitution of Chaetoceros muelleri by Spirulina platensis meal (SPM) was evaluated. The substitution levels (S) were 0%, 25%, 50%, 75% and 100%, dry weight basis. Final larval length (FL) ranged from 1.98 to 3.16 mm for the different substitution levels. There was a significant relationship between S and FL, described by the following quadratic equation: FL = 2.853 + 0.01598S − 0.000233S2. The substitution level (S) yielding maximum FL was 34.2%. Development index (DI) values ranged from 2.84 to 3.93 and were dependent on substitution level. The corresponding equation was DI = 3.799 + 0.00945S − 0.000189S2 (P < 0.01). Maximum DI was obtained at 25.0% substitution. Survival was high (82–87%) and no significant differences were found between treatments. Protein digestibility of either microalgae was high, with 92% for SPM and 94% for C. muelleri, with no significant differences between them. The results in this study indicate that an adequate balance of nutrients in relation to the requirements of the species is critical. To simultaneously improve FL and DI, a 30% substitution of C. muelleri by SPM is suggested. This is equivalent to feeding 0.15 mg larvae− 1 day− 1 dry weight basis of a 70% C. muelleri/30% SPM diet, representing 0.078 mg protein larvae− 1 day− 1, 0.026 mg lipids larvae− 1 day− 1 and 2.732 J larvae− 1 day− 1.  相似文献   

10.
The aim of this study was to develop a protocol for semen storage of piracanjuba (Brycon orbignyanus) by both cool storage at 4 °C and cryopreservation at − 196 °C. Semen was diluted in some fish semen extenders (Exp. 1) or in extenders combined with the antibiotic gentamycin sulfate (Exp. 2) and stored at 4 °C. Sperm motility was estimated every 24 h. Then, the effects of egg yolk (0 and 5%), cryoprotectants (dimethyl sulphoxide — DMSO, methanol, and methylglycol) and extenders (NaCl 154 mM, BTS™ Minitub and M III™ Minitub) on semen cryopreservation were evaluated (Exp. 3). Semen was added to each of eighteen cryosolutions (2 yolk concentrations × 3 cryoprotectants × 3 extenders), aspirated into 0.5-mL straws, frozen in nitrogen vapor (Taylor-Wharton, CP 300, “dry shipper”) and stored at − 196 °C. Sperm motility was evaluated after thawing at 60 °C-water bath for 8 s. The three cryosolutions that produced the highest post-thaw sperm motility were used again to freeze semen. Post-thaw semen quality was then evaluated under three tests: sperm motility, the percentage of live spermatozoa and hatching rate (Exp. 4). Piracanjuba semen diluted (1:10 total volume) in NaCl 200 mM or in Saad solution (NaCl 200 mM, Tris 30 mM) maintained motility above 35% for as long as 7 days, at 4 °C. Motility of only 7% was observed on undiluted semen after 3 days at 4 °C. There was neither beneficial nor detrimental effect of gentamycin on sperm motility at 250 μg/mL. Egg yolk addition to the cryosolution was beneficial in samples cryopreserved in NaCl 154 mM and in M III™, but detrimental for samples cryopreserved in BTS™. Methylglycol was the most effective cryoprotector compared to DMSO and methanol. Motility and percentage of live spermatozoa were similar among semen cryopreserved in NaCl–yolk, M III™–yolk and BTS™, all containing 10% methylglycol, but lower than fresh control. Hatching rates of eggs fertilized with sperm cryopreserved in NaCl–yolk or BTS™ were higher than for eggs fertilized with sperm cryopreserved in M III™–yolk, but lower than control fertilizations. The semen cryopreservation protocols developed here will be used to set up a gene bank for endangered piracanjuba populations.  相似文献   

11.
In coral aquaculture, sexual reproduction increasingly plays an important role for serving trade and reef restoration purposes. However, until coral juveniles reach a semi-stable size which makes them less vulnerable against algal growth and sedimentation, high mortality rates may occur in the first several weeks to months after settlement. In the present study, the influence of several food sources on the growth and survival of newly settled primary polyps was studied under laboratory conditions for 5 months. In order to estimate effects on specimens of both reproductive modes, experiments were carried out with the brooder, Favia fragum, and with the broadcast spawner, Acropora tenuis. Primary polyps kept in 2-liter aquaria were daily fed with freshly hatched Artemia salina, the micro algae Phaeodactylum tricornutum and a commercially available dry food (Nori Micro, Zoolife®), respectively, at various concentrations. Growth rates in both species were significantly higher in the Artemia treatment with maximum rates of 9.4 ± 4.9 mm2 (mean ± S.D.; d = 5 months) for F. fragum and 26.8 ± 10.3 mm2 (d = 5 months) for A. tenuis compared to all other treatments and the control (no additional food). Survival in F. fragum was overall higher than 60% in all treatments with maximum rates of 85.0 ± 12.6% at the highest Artemia concentration. Survival rates in A. tenuis ranged from 28.9 ± 4.7% (lowest Nori concentration) to 86.2 ± 5.9% (medium Artemia concentration). The present study shows that Artemia nauplii may greatly enhance the growth and partly enhance the survival of early sexual recruits which may significantly help to more rapidly overcome the early and most fragile post-settlement stages. As a consequence, the residence time for sexual coral recruits in cost- and labour-intensive hatcheries may be greatly reduced.  相似文献   

12.
This study evaluated the effect of low water temperature (10 ± 1 °C) on viral infection and replication of white spot syndrome virus (WSSV) in crayfish, Procambarus clarkii, under standardized conditions. Crayfish were (i) maintained at 24 ± 1 °C before challenge and 10 ± 1 °C afterwards, or (ii) maintained at 10 ± 1 °C before challenge and 24 ± 1 °C afterwards. No mortality was observed when crayfish were held at 10 ± 1 °C after challenge, but mortality reached 100% when they were transferred to 24 ± 1 °C. Competitive PCR showed that viral levels at 10 ± 1 °C rose from 106 to 108 copies/mg of gill tissues, while at 24 ± 1 °C levels increased from 106 to 1010 copies/mg of gill tissues during the same time interval. These results showed that a low water temperature of 10 ± 1 °C could reduce viral replication when compared to 24 ± 1 °C but could not prevent it.  相似文献   

13.
Argopecten purpuratus can be cultivated using Recirculating Aquaculture Systems (RAS) as a method to increase production. In order to determine physiological response of A. purpuratus under different salinities and temperature conditions, two groups of juvenile scallops (small: h = 6.5 mm and large: h = 25.5 mm) were acclimated and close-cultured at salinities of 34, 38, and 42 g/l, at 16 and 22 °C and fed on Isochrysis galbana and Chaetoceros calcitrans. Survival, shell growth and scope for growth were determined at the end of the trials. Survival showed an inverse relationship with temperature and ammonia levels. In small scallops an increase in salinity at 16 °C increased survival. However, this relationship was not evident at 22 °C. On the other hand, salinity did not affect survival of large juveniles. Small juveniles had a lower survival (approximately 40%) than larger scallops (up to 85%) throughout the trials. Oxygen consumption was not affected by salinity. Small scallops showed similar oxygen consumption at 16 and 22 °C but in large juveniles higher values were registered at 22 °C. In large juveniles routine consumption at 16 °C was higher (up to 35%) than standard consumption. This pattern was not evident at 22 °C, suggesting that oxygen demand is higher regardless of feeding condition. NH4+–N excretion rate is inversely related to salinity. Only small juveniles showed a higher NH4+–N excretion rate at 22 °C. Scope for growth was positive in all treatments, although the upper limit of salinity should not be based only in this index. Higher scope for growth values at 38 and 42 g/l was related with a reduction in ammonia excretion and high absorption efficiency. In addition, an increase in salinity produced a reduction in NH3–N proportion and under hypersaline conditions scallops tended to decrease excretion as a way of osmoconformation. This explains our findings of higher survival rates at higher salinities. Even though the scope for growth is positive at 42 g/l, the osmotic stress reduces the survival chances. The data obtained can be considered useful information for A. purpuratus culture under controlled conditions.  相似文献   

14.
This study analyzed the morphological development and allometric growth patterns of Lota lota L. (burbot) larvae reared under controlled laboratory conditions. From hatching to day 50, twenty larvae were sampled each [between 1 and 14 days post-hatch (DPH)] or every second day (between 14 and 50 DPH) and measured under a stereoscopic microscope using analytic software. Based on the external morphology, the different stages during early development of burbot were identified: yolk sac larva 0–8 DPH [3.92–4.37 mm total length (TL)]; preflexion larva 9–26 DPH (4.57–12.06 mm TL); flexion larva (between notochord degradation and its replacement with rays) 28–34 DPH (14.00–16.34 mm TL) and postflexion larva/juvenile 36–50 DPH (18.20–29.27 mm TL). Allometric growth patterns of some parameters (e.g., total length, head length, body length, tail length, head depth, body depth, eye diameter) were modeled by a power function and described by the growth coefficient. Organogenesis and changes of body proportions in burbot larvae were more rapid and complex during the yolk sac and preflexion phase of development as larvae developed most of their sensorial, feeding, respiratory and swimming systems and after notochord flexion, when most morphological changes were related to the progressive transformation from pelagic larva to demersal larva/juvenile.  相似文献   

15.
Proteases play a key role in yolk formation and degradation during embryogenesis of marine fish. This study presents the first clear data on the involvement of trypsin and chymotrypsin activities in the embryogenesis of Atlantic cod (Gadus morhua). Both enzyme activities were shown to be present in unfertilized eggs followed by a significant decline (P < 0.01) in trypsin activity during the first 4 days post fertilization (dpf). Thereafter, the trypsin- and chymotrypsin activities increased to a maximum around day 9 pf. A decline in trypsin and chymotrypsin activities was observed from day 10 pf with minimal activity just prior to first feeding (day 15 pf). Western blot analysis, using polyclonal antibodies raised to Atlantic cod trypsins I and Y, mostly coincided with the trypsin activity profile. The novel trypsin Y was previously shown to have both trypsin- and chymotrypsin-like activities. Thus, some of the chymotrypsin activity observed in the samples may be originated from trypsin Y. The low trypsin and chymotrypsin activities just prior to first feeding (13–15 dpf) may indicate insufficient digestive function as trypsin has been shown to be a suitable short-term indicator reflecting the nutritional quality of marine fish larvae.  相似文献   

16.
Feeding enriched Artemia induces growth failure in Pacific bluefin tuna (PBT) Thunnus orientalis larvae; however, feeding of yolk-sac larvae of marine fish promotes larval growth. It is considered that this growth failure partly results from dietary docosahexaenoic acid (22:6n-3, DHA) deficiency. Therefore, we examined the effect of DHA contents in enriched Artemia on the growth of PBT larvae. Artemia nauplii were enriched with graded levels of DHA ethyl ester, and fed to PBT larvae for 9 days. Yolk-sac larvae of Japanese parrotfish Oplegnathus fasciatus were used as a reference diet. The DHA contents in Artemia increased with the enrichment from 0 mg g− 1 dry weight basis (DW) to 25 mg g− 1 DW, while the content in the reference diet was 21 mg g− 1 DW. Feeding of enriched Artemia significantly improved the growth of PBT larvae. However, this improvement was negligible when compared with the excellent growth of the larvae that were fed the reference diet. PBT larvae that were fed the reference diet accumulated approximately twice or much higher levels of DHA in the neutral and polar lipids in the body when compared with the larvae that were fed enriched Artemia. These results show that PBT larval growth cannot be promoted by feeding enriched Artemia even if the DHA contents in Artemia are elevated to the same levels as those of yolk-sac larvae. The incorporation of dietary DHA into phospholipids in the fish body may be desirable for the normal growth of PBT larvae.  相似文献   

17.
Incubation of northern snake-necked turtle (Chelodina rugosa) eggs and subsequent sale of hatchlings for the pet industry has the potential to provide culturally suitable employment for indigenous communities in northern Australia. Developmental arrest in response to egg inundation is unique to C. rugosa. Eggs can be stored under water for up to 10 weeks without appreciable impact on egg or embryo survival, allowing the transport and sale of eggs into niche markets without high levels of mortality, and permitting eggs to accumulate in diapause until there are sufficient numbers to incubate as batches. Eggs that are not inundated or inundated for short periods experience similar survival rates to eggs inundated for lengthy periods. Incubation temperature influences embryo survival and development period in C. rugosa. Embryonic survival is greatest at 26 °C, steadily declining as temperature increases to 32 °C. A similar increase in incubation temperature decreases incubation period by approximately 40 days, however almost half of this variation is attributed to the increase in incubation temperature from 26 to 28 °C. Hatchling growth in C. rugosa is characterized by two phases. There is an initial phase of relatively slow growth under the partial influence of initial egg size and incubation duration, followed by a second phase of relatively rapid growth under the partial influence of water temperature and mass at hatching. Post-hatching survival is negatively correlated with duration of egg inundation and water temperature. Evidence suggests that inundation of C. rugosa eggs for 6 weeks, incubation of embryos at 28 °C and raising hatchlings in 28 °C water will yield the best overall outcomes.  相似文献   

18.
This study examined the efficacy of bithionol as an oral treatment for Atlantic salmon Salmo salar affected by amoebic gill disease (AGD). The current commercial management strategy of AGD is a costly 3 h freshwater bath. It is labour intensive and the number of baths needed appears to be increasing; hence, there is an effort to identify alternative treatments. Efficacy was examined by feeding AGD-affected Atlantic salmon twice daily to satiation with bithionol, an antiprotozoal, at 25 mg kg− 1 feed. Three seawater (35‰, 17 °C) re-circulation systems were used each consisting of three tanks containing 32 Atlantic salmon smolts with an average (± SEM) mass of 90.4 g (± 5.2). Three feeds were examined in the trial including bithionol, plain commercial control and oil coated commercial control. Feeding commenced 2 weeks prior to exposure to Neoparamoeba spp. at 300 cells L− 1 and continued for 28 days post-exposure. Efficacy was determined by examining gross gill score and identifying percent lesioned gill filaments twice weekly for 4 weeks post-exposure. Bithionol when fed as a two-week prophylactic treatment at 25 mg kg− 1 feed delayed the onset of AGD pathology and reduced the percent lesioned gill filaments by 53% and halved the gill score from 2 to 1 when compared with both the plain and oil controls during an experimental challenge. There were no palatability problems observed with mean feed intake of bithionol over the trial duration with fish consuming higher levels of the bithionol diet compared to both the oil and plain controls. This study demonstrated that bithionol at 25 mg kg− 1 feed, when fed as a two-week prophylactic treatment for Neoparamoeba spp. exposure, delayed and reduced the intensity of AGD pathology and warrants further investigation as an alternative to the current freshwater bath treatment for AGD-affected Atlantic salmon.  相似文献   

19.
The ability of Loligo opalescens paralarvae to resist and recover from starvation was examined by measuring their survival, growth rate and RNA/DNA ratios during starvation and refeeding. Paralarvae were fed Artemia sp. nauplii, zooplankton and mysid shrimp. Fourteen days after hatching they were separated into five feeding treatments: a control treatment (food was always available) and treatments starved for 2, 3, 4 and 5 days, and then refed. Each day, 5–7 paralarvae from each treatment were anesthetized to measure mantle length and wet weight (WW), and then RNA and DNA were extracted using an ethidium bromide fluorometric technique. Paralarvae did not survive 4 and 5 days of starvation, showing that at 15 days of age and at 16 °C the limit to recovery was 3 days of starvation. Paralarvae starved for 2 and 3 days showed compensatory growth that mitigated the effects of starvation, in that at the end of the experiment (10 days), they attained mean final body weights similar to the control treatment. Differences in the RNA/DNA ratios between control and starved paralarvae were detected within 2 days of food deprivation. For paralarvae starved 2 and 3 days, it took 1 day after refeeding to attain RNA/DNA ratios not significantly different from the control treatment. Additionally, RNA/DNA ratios were highest during the day (0800, 1200, 1600 h) and lowest at night (0000, 0400 h), suggesting daytime feeding activity. Growth rates ranged from − 14% to 21% WW day− 1 and the resulting equation between RNA/DNA ratio and growth rate (GR) of paralarvae was GR = 1.74 RNA/DNA − 11.79 (R2 = 0.70). After starvation, there was a reduction in growth variability in all starved treatments, while growth variability remained high in the control treatment. Findings from the present study indicate that nucleic acids are a valid indicator of nutritional condition and growth in squid paralarvae.  相似文献   

20.
All seahorse species worldwide have been placed under CITES Appendix II since 2004, because they have been over-exploited for traditional Chinese medicine and aquarium trades. Aquaculture has been recognized as a long-term solution for sustaining the seahorse trade while minimizing wild collection. In this study, we evaluated the breeding and juvenile culture of an important aquarium seahorse species, the lined seahorse Hippocampus erectus, Perry 1810. Pairing, mating and copulation behavior were observed. Gestation time and brood size were 17.33 ± 2.94 days and 272.33 ± 66.45 individuals/brood, respectively. Growth rates differed among juveniles from different broods. Effects of temperature on the growth rates and survivorship of the juveniles during the first two weeks were compared. The highest growth rate and survivorship of the juveniles occurred at 28–29 °C among the temperatures tested (24–33 °C). Growth rate and survivorship of the juveniles during the first 9 weeks at 28 °C were investigated. The final standard length and survivorship of the juveniles were 6.32 ± 0.52 cm and 71.11 ± 10.18%, respectively, and the relationship between the wet weight and the standard length of the juvenile seahorses can be expressed as: W = 0.0034 L2.5535 (r2 = 0.9903, n = 12, P < 0.01). These findings suggest that H. erectus is a good candidate for commercial aquaculture.  相似文献   

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