Immune response of sea bass <Emphasis Type="Italic">Dicentrarchus labrax</Emphasis> to <Emphasis Type="Italic">Tenacibaculum maritimum</Emphasis> antigens

ABSTRACT:   Seawater fishes are affected by a pathology commonly called 'myxobacteriosis', caused by Tenacibaculum maritimum (formerly Flexibacter maritimus ). The disease is characterized by fin erosion and necrotic ulcers of skin and muscle, and by low but constant mortality in cultured marine fish; in Italy is one of the most important and widely spread diseases affecting sea bass Dicentrarchus labrax , gilthead seabream Sparus aurata , sharp-snouted bream Diplodus puntazzo , white bream Diplodus sargus , and six-tooted bream Dentex dentex . In order to obtain an effective vaccine against the disease, formalin killed cells (FKC), extracellular products (ECPs) and crude lipopolysaccharide (LPS) preparations were obtained from the T. maritimum strain SPVId and injected intraperitoneally twice into the sea bass. The fish immune response to the preparations was studied: agglutinating antibody titer and in vitro phagocytosis were determined after the first and second injection in order to evaluate whether the preparations are immunogenic or not and if the booster effect took place. The results show that FKC and LPS preparations increased the antibody titer after the first injection when compared to the control sea bass. Moreover, all the preparations stimulated a secondary (booster) response. In vitro phagocytosis of the total blood was significantly higher for all the preparations when compared to the controls, but the crude LPS immunized sea bass showed the highest activity.     

Influence of larval co-feeding with live and inert diets on weaning the tongue sole Cynoglossus semilaevis

The tongue sole Cynoglossus semilaevis, an inshore fish in China, has showed great potential in aquaculture recently. However, poor survival was recorded during the period of weaning from live Artemia to artificial diets. In this paper, the influence of co‐feeding larvae with live and inert diet on weaning performance was described. The C. semilaevis larvae were reared at 21 ± 1 °C and fed four different feeding regimes from 6 days post‐hatching (dph): A, Artemia (10 individuals mL^?1); B, Artemia (5 individuals mL^?1); C, mixed diet (10 Artemia individuals mL^?1 and 12 mg L^?1 inert diet); and D, mixed diet (5 Artemia individuals mL^?1 and 12 mg L^?1 inert diet). Rotifers were also supplied in all cases during the first days of feeding. Mixed diets of commercial formulated feed and live prey (rotifers and Artemia) allowed larvae to complete metamorphosis, achieving similar specific growth rate (SGR) (18.5 ± 1.4% and 18.7 ± 1.6%) and survival (40 ± 7.6% and 48.5 ± 6.8%) compared with larvae fed on live feed alone (SGR of 18.3 ± 1.2%, 19.3 ± 1.9% and survival of 41.2 ± 11.3%, 38 ± 4.9%). However, in metamorphosed fish, when live feed was withdrawn on 31 dph, there was significant difference (P < 0.05) in survival and growth among treatments. Metamorphosed fish, previously fed mixture diets during larval stages, had similar survival (62.1 ± 7.6% and 62.8 ± 3.9% for regimes C and D, respectively) but higher than that obtained for fish that previously fed on live feed (49.3 ± 2% and 42.1 ± 3.9% for regimes A and B, respectively) after weaning (day 60). The SGR of weaned fish previously fed live feed was similar (3.1 ± 0.6% and 2.92 ± 0.6% for regimes A and B, respectively) but lower than that recorded for fish that was fed from day 6 to day 30 on the mixed diet (4.5 ± 1.1% and 4.9 ± 0.3% for regimes C and D, respectively). It is suggested that weaning of C. semilaevis from early development would appear to be feasible and larval co‐feeding improves growth and survival.     

Early weaning of winter flounder (Pseudopleuronectes americanus Walbaum) larvae on a commercial microencapsulated diet

Like most small marine fish larvae, the stomachs of winter flounder Pseudopleuronectes americanus are undeveloped at first feeding and have relatively reduced digestive capacity. This work was undertaken to test whether larvae at the onset of stomach differentiation (larval size about 5.5 mm) could be early weaned onto a commercial microencapsulated diet. We assessed the effect of early weaning by first comparing growth performance (standard length, total protein content and age at metamorphosis) of larvae fed enriched live prey from first feeding to a size of 5.5 mm and then reared on three different feeding regimes until metamorphosis: (1) live prey (LP) as a control group; (2) mixed feeding of live prey and microencapsulated diet (LP‐ME); (3) exclusively microencapsulated diet (ME) after fast weaning over 4 days (to a larval size of 6.2 mm). No differences were observed between larval development in the two first groups, which began metamorphosis at 40 days old. The larvae of the third group showed significantly slower growth that resulted in a delay of 4 days in the onset of metamorphosis. Differences in live prey availability between the treatments and the short transition period to allow the larvae to adapt to the new diet were identified as possible contributing factors to the slower growth and to the delay in metamorphosis of early weaned larvae. In a second experiment, the transitional weaning period was increased until the larvae were 6.6 mm in length. Weaning at that size resulted in no slowing of growth or delay in metamorphosis, suggesting that the feeding schedule was adequate.     

Seed production of Charybdis feriatus (Linnaeus)

Some aspects of the reproductive biology of Charybdis feriatus (Linnaeus) were investigated to identify suitable techniques for broodstock management and seed production. Likewise, factors such as ablation, water depth and light requirements affecting survival or reproductive performance were tested. Production of megalops in tanks and juveniles in net cages installed in earthen ponds was conducted. Wild‐caught berried females produced a significantly higher number of zoeae per gram body weight (BW) of the female (3300±600) than captive spawners (867±58). Ablated and unablated crabs spawned after a month and ovaries of both had oocytes in all developmental stages after spawning, indicating that ablation was not necessary. Broodstock survived higher when stocked in 1 m‐deep water and kept in dark conditions compared with shallow (0.5 m depth) water or ambient lighting. There were six zoea and one megalopa stage. Megalops were produced (survival of 2–22% in 1 tonne or 23–55% in 3 L tanks) when methods for the mud crab Scylla serrata (Forsskål) were used, but feeding with Artemia started only at the Z4 stage. Survival of megalops after 1 month was higher when stocked in net cages installed in an earthen pond (32–82%) than when reared continuously in land‐based tanks (5–11%).     

Dietary spermine supplementation induces intestinal maturation in sea bass (Dicentrarchus labrax) larvae

Sea bass (Dicentrarchus labrax) larvae were fed microparticulated compound diet containing 0 (FP0), 0.10 (FP10) and 0.33% (FP33) of a polyamine, spermine, from day 20 to day 38. LP group was fed live prey. This group exhibited the highest growth and survival. The addition of spermine did not lead to growth enhancement. A 33% survival improvement was obtained in FP33 group compared to FP0 group. The spermine addition affected the activity of pancreatic enzymes, trypsin, chymotrypsin and amylase, during larvae development. This non specific effect suggested that the action of spermine would be mediated by hormones. In the intestine, the FP33 group exhibited from day 31 higher activities of brush border membrane enzymes (leucine aminopeptidase and alkaline phosphatase) and lower level in a cytosolic enzyme (leucine-alanine peptidase) compared to FP10 and FP0 group. The diet containing the highest spermine level induced an enzymatic profile similar to that obtained in LP group and characteristic of a mature enterocyte. The initiation of enterocyte maturation at a proper development stage was associated to the survival improvement observed in FP33 group.     

Pigmentation and eye migration in Atlantic halibut (Hippoglossus hippoglossus L.) larvae: new findings and hypotheses

Atlantic halibut juveniles, which have been fed Artemia during larval development, frequently demonstrate malpigmentation and impaired eye migration. This is in contrast to the high percentage of normally developed larvae fed copepods, reared under similar conditions. Nutrition is therefore an important component influencing larval development. Analyses of the nutrient composition of Artemia and copepods show that Atlantic halibut larvae fed Artemia probably receive sufficient amounts of vitamin A by converting canthaxanthin, while iodine may be deficient, possibly leading to interrupted thyroid hormone synthesis. An unbalanced fatty acid composition, such as high levels of arachidonic acid and low levels of docosahexaenoic acid, can be another limiting factor in Artemia. Vitamin A, fatty acids and thyroid hormones have all been shown to affect pigmentation in flatfish. They are ligands to nuclear receptors, thyroid hormone receptors, retinoic acid receptors, retinoic X receptors and peroxisomal proliferator‐activated receptors, which are members of the superfamily of steroid hormone receptors. The receptors interact with each other to promote gene expression that modulates proliferation and differentiation of cells. Our hypothesis is that these interactions are important for development during flatfish metamorphosis. Very little data exist on the topic of impaired eye migration. However, energy limitation, iodine deficiency and an unbalanced fatty acid composition have been proposed as possible explanations. Here, we review the literature on development of pigment cells and the possible mechanisms behind the effects of vitamin A, fatty acids and thyroid hormone on pigmentation and eye migration during development of Atlantic halibut larvae.     

Effects of addition of a bird repellent to fish diets on their growth and bioaccumulation

The effects of adding the nonlethal bird repellent methyl anthranilate (MA), at levels of 100 and 1000 mg kg^?1, to fish feed on the bioaccumulation and growth of juvenile (10 g) hybrid striped bass (Morone chrysops×M. saxatilis) and juvenile (1 g) African cichlid fish Aulonocara jacobfreibergi were investigated under laboratory conditions. The bird repellent did not have any effect on the fish growth or survival over a period of 6 weeks. MA residues at low levels of 11.2±2.6 μg g^?1 were found in lipophilic tissues (liver) of MA‐fed fish. Control fish, which had no MA added to their diet, had a much lower level of 0.6±0.3 μg g^?1 MA in their liver. Fish muscle was found to contain negligible MA residues, while the outer body surface mucus did not contain any MA. Following a 6‐week depuration period, during which the previously MA‐fed hybrid striped bass were fed a feed to which no MA was added, the levels of MA residues detected were reduced by one order of magnitude.     

Influences of El Niño on assemblages of mesopelagic fish larvae along the Pacific coast of Baja California Sur

Seasonal assemblages of mesopelagic fish larvae and changes related with environmental factors (plankton biomass, sea surface temperature anomaly, upwelling, and the multivariate El Niño index) were investigated. From 1982 to 1987, 16 oceanographic cruises were carried out along the Pacific coast of Baja California Sur, Mexico. Larvae of 42 mesopelagic fish taxa were collected. Larval abundance was highly variable during the studied period, but summer months coincided with higher abundance (>200 larvae under 10 m²). Larval assemblages were dominated by three of the most common species of tropical (Vinciguerria lucetia, Diogenichthys laternatus) and subtropical affinity (Triphoturus mexicanus). A group of species of tropical affinity (Diplophos proximus, Diaphus pacificus, Benthosema panamense) was useful for distinguishing the 1982–84 El Niño event, and an assemblage of larvae of temperate affinity (Symbolophorus californiensis, Melamphaes lugubris, Bathylagus ochotensis, Leuroglossus stilbius, Protomyctophum crockeri) characterized ‘normal’ years (mid‐1984 to mid‐1987).     

Effects of four egg desticking procedures on hatching rate and further survival and growth of larvae in the tench (Tinca tinca L.)

Four desticking procedures for tench eggs (A: tannic acid solution (1 g L⁻¹) for 15 s; B: alcalase enzyme solution (8 mL L⁻¹) for 60 s; C: alcalase enzyme solution (15 mL L⁻¹) for 120 s; D: Woynarovich and Woynarovich (1980) solution for 58 min followed by tannic acid solution (1 g L⁻¹) for 15 s) were tested to obtain data about influence on embryo survival to hatching stage and further survival and growth of the larvae. In the tannic acid and Woynarovich and Woynarovich (1980) treatment (A and D) few eggs stuck together and some were adhered to the incubator walls, whereas in the alcalase treatments (B and C) eggs neither stuck together nor adhered to the incubator walls. Percentages of hatched larvae did not show significant differences (mean values ranged between 47.4% in treatment A to 37.0% in treatment C). Larvae deformities observed were <0.5% in all cases. There were no significant differences among survival and growth rates of the larvae from different egg desticking origin, reaching, after 30 days, mean survival values around 90% and total length and weight of 12.5 mm and 19 mg respectively.     

盐度对真鲷受精卵发育及仔稚鱼生长的影响

在室内水池以溢水法收集真鲷 (Pagrosomusmajor)受精卵 ,并置于不同盐度海水中静水孵化 ,孵出仔鱼以流水培育。设置盐度梯度为 17.0、2 2 .0、2 7.0及自然盐度 3 3 .0 ,水温分别为 19.5～ 2 1.5℃ (孵化 )、2 0 .5～ 2 3 .5℃(培育 )。结果表明∶①真鲷受精卵在自然盐度海水中发育很好 ,孵化率较高 ( 85 .0 %～ 97.0 % ) ,畸形率较低 ( 3 .2 %～ 2 3 .7% ) ;在低盐度条件下静水孵化 ,发育不好 ,孵化率为 4 8.0 %～ 1.0 % ,且盐度越低 ,孵化率也越低。充气孵化时 ,盐度低至 17.0 ,孵化率有时也可达 97.1% ,但畸形率高达 85 .7%～ 10 0 %。②孵化仔鱼中有 2类畸形 ,第 1类畸形表现为身体或尾部弯曲 ,油球位于卵黄囊中部或前部 ,油球数多于 1个 ,盐度越低 ,畸形率越高 ;第 2类畸形表现为仔鱼膜膨大、围心腔扩大 ,这类畸形只出现于低盐度条件下 ,盐度越低 ,畸形率越高 ,且往往与第 1类畸形症状并发。③不同盐度对真鲷仔稚鱼的生长速度没有显著影响 ,各盐度条件仔稚鱼经 3 1d的培养 ,其平均全长为 19.6～ 2 0 .7mm( P >0 .0 5 ) ,没有显著的差别。④海水盐度越低 ,仔稚鱼的存活率越高 ,各组的平均存活率为 ,盐度17.0时 ,3 6.3 % ;盐度 2 2 .0时 ,3 6.2 % ;盐度 2 7.0时 ,2 7.1% ;盐度 3 3 .0时 ,16.3 %。