The immune system of juvenile thick-lipped grey mullet, Chelon labrosus Risso: antibody responses to soluble protein antigens

Juvenile thick-lipped grey mullet, Chelon labrosus , believed to be about 6–7 months old, possessed well developed lymphoid organs including a clearly differentiated thymus with distinct cortical and medullary zones. However, unlike older fish, the juvenile mullet usually failed to produce antibody in response to a single injection of classical thymus-dependent antigen (using the soluble proteins human gamma globulin or keyhole limpet haemocyanin). Prior priming of the juvenile fish with antigen was found to potentiate antibody production following challenge with a second dose of the antigen in adjuvant, priming by oral administration being equally as effective as priming by injection. Neither juvenile nor adult mullet produced any significant level of antibody against ovalbumin.
The results suggest that, despite their apparently well differentiated lymphoid organs, juvenile mullet still show a certain level of immaturity in their antibody responses to soluble proteins; also that immunization can improve their ability to respond.     

The immune response of the thick-lipped grey mullet, Chelon labrosus (Risso, 1826), to metacercarial infections of Cryptocotyle lingua (Creplin, 1825)

Grey mullet, Chelon labrosus , (60–100 g) have been found to respond immunologically to Cryptocotyle lingua , following a single exposure to 20000 cercariae, by the production of humoral antibody, sensitized pronephric leucocytes and cytotoxic serum factors. Antibody titres measured by passive haemagglutination reached a peak at week 4 with a -log₂ titre of 16±S.E. 1.0, and titres of 10.7±S.E. 1.0 were still recorded after 10 weeks at the termination of the experiment. Cercarial agglutination was found unreliable as a rapid test. Pronephric leucocytes, sensitive to cercarial antigen when measured by the under-agarose migration method, were detected between weeks 1 and 6, peaking at week 2. In vitro polarization was increased when cells were incubated with the antigen, but this increase was not significantly different between control and infected fish. Heat-labile cytotoxic factors of immune sera have been demonstrated to whole cercariae in vitro , these factors being associated with structural damage to the tegument. Pronephros cells isolated from immune fish during each week of infection showed no evidence of adherence to cercariae or metacercariae in vitro. The results are discussed in relation to both host response and course of infection of the parasite.     

Association of an acoustic signal with operant conditioned feeding responses in thicklipped mullet, Crenimugil labrosus (Risso) and common carp, Cyprinus carpio (L.)

Groups of both carp, Cyprinus carpio , and mullet, Crenimugil labrosus , learned to associate a 250 Hz sine wave generated acoustic singnal with a previously conditioned trigger pressing operant response for food. Within 48 h, a programmed signal of 5 min duration in every 1 h period was stimulating trigger responses for food reward, whilst during other periods not associated with sound there were few responses.     

Operant conditioning of feeding behaviour and patterns of feeding in thick lipped mullet, Crenimugil labrosus (Risso) and common carp, Cyprinus carpio (L.)

Groups of carp and thick lipped mullet quickly learned to operate an underwater trigger for food reward. Single mullet also learned this operant response but single carp did not. Groups of mullet exhibited a higher rate of responding than groups of carp. Mullet appeared to feed in bouts, whereas carp fed randomly during the learning trials. Both species adapted well to six days continuous demand feeding. Grouped and single mullet decreased their feeding at night but carp did not show a diurnal feeding pattern. Feeding responses were found not to be sequences of random events and response rates over the six days were higher in carp than in mullet. In both species, individual fish within a group operated the trigger significantly more often than other fish but all fish took food and gained weight.     

Fine structure of hepatocytes in juvenile grey mullets: Liza saliens Risso, L. ramada Risso and L. aurata Risso (Teleostei, Mugilidae)

Livers of 45 fingerling grey mullets ( Liza sp. 5-15 cm long) were subjected to light microscopy, transmission electron microscopy and enzyme cytochemical examination. The hepatic structure was found to be comparable in all three Liza species. As in other fish species, Liza liver parenchyma is arranged in cords (or dual-plated laminae, in sections parallel to the sinusoidal axis). Hepatocytes showed numerous microvilli in their perisinusoidal and canalicular areas. They contained a centrally located nucleus, fairly large areas of rough endoplasmic reticulum, consisting mainly of parallel cisternae, and pools of glycogen. A few small lipid droplets were evenly distributed in the cytoplasm. The Golgi fields, between the canaliculus and the nucleus, consist mainly of dictyosomes, lysosomes and autophagic vacuoles. Acid phosphatase activity was cytochemically localized to reaction products in secondary lysosomes and lipofuscin granules. A comparison between grey mullet liver and that of other teleosts was made.     

Hemoglobin system of golden mullet (Liza aurata,Risso) at adaptation to conditions of outer hypoxia

Under conditions of experiment, effect of outer hypoxia on the hemoglobin heterogeneous system and respiratory blood characteristics were studied in the golden mullet Lisa aurata R. The control fish group was maintained at oxygen pressure of 158–162 gPa, the experimental group at 54–55 gPa. The exposure was 15 days, the water temperature—15°C. Under conditions of oxygen deficit in the mullet body there is noted development of a complex of compensatory reactions directed to maintenance of the oxygen blood capacity. Initially (the 1st–2nd day), the release of erythrocytes from spleen is noted, which increases the number of red blood cells and the hemoglobin concentration in blood (the emergency adaptation). Subsequently (the 10–15th day), there occur quantitative readjustments at the level of the hemoglobin system, which lead to an increase in the blood affinity to oxygen and to a decrease in its sensitivity to pH (the long-term adaptation). The revealed changes take place on the background of a decrease in volume of circulating erythrocytes, which reflects the character of change of erythrocytic parameters (MCV, MCHC) and seems to be a consequence of partial dehydration of blood plasma.     

An energy budget for Simocephalus vetulus (O. F. Muller) (Crustacea : Cladocera)

We discuss the energetics of a cladoceran, Simocephalus vetulus at different temperatures (8.0 ± 1.0, 15.0 ± 1.0, 21.0 ± 1.0 and 28.0 ± 1.0 °C) and food (Chlamydomonas sp.) concentrations (25 × 10³, 50 × 10³, 75 × 10³ and 100 × 10³ cells ml⁻¹). Increase in temperature accelerated ingestion and, to some extent, oxygen consumption. The study revealed a high reproduction efficiency in S. vetulus. Net growth efficiency (ECI) was higher (13.17–41.18%) in pre-adults than in adults (2.71–8.40%). The assimilated energy (A) increased with increasing food concentration at all temperatures. Assimilation efficiency (AD) decreased with increasing food concentrations. The energy used for growth (P) was nearly constant at all food levels because the egested energy increased and assimilation efficiency decreased as food concentration increased.     

Maturity and fecundity of golden grey mullet (Liza aurata Risso, 1810) in Iranian waters of the Caspian Sea

The objective of the study was to determine some reproductive parameters in the golden grey mullet (Liza aurata Risso, 1810) during two periods half a decade apart while also trying from limited data to identify changes in fecundity over the past half century. Maturity and fecundity of golden grey mullet caught in Iranian waters of the Caspian Sea is not well documented and were thus studied during several seasonal cycles during 2002–2004 to establish basic data on reproduction in the area. The fork length (FL) of 462 sampled fish was between 22.1 and 51.9 cm. The fork length–weight relationship derived from all fish was W = 0.0118FL^2.964. Overall male to female ratio was 1 : 1.42. The reproductive season extended from October to December. Fifty percent of sexual maturity was at FL 26.0 cm. Mature gonads were present in 20% of fish at age 3, 63% at age 4, 88% at age 5, and 97% at age 6. Individual absolute fecundity of the golden grey mullet ranged from 113 386 to 1.47 million eggs, with a mean (±SD) of 451 963 (±274,114.2). An overlap exists between the spawning and fishing seasons. Therefore, the start of the fishing season should be delayed for 1 month in order for stocks to complete their spawning.     

An energy budget for an omnivorous cyprinid: Rutilus rutilus (L.)

Two to three year old roach (9–15 g body weight) were fed ad libitum with grass or with meal worms. After three weeks, both groups of fish showed a positive energy budget. However, with a grass diet, production was low (only 7% of that of meal worm feeding fish) with an increased of lipids, whereas the protein content of the body decreased. Non-crude fiber organic matter of grass was utilized to 47.6%, that of meal worms to 82.4%.     

饥饿对牙鲆幼鱼补偿生长、生化组成及能量收支的影响

在水温(23.0±1.0)℃条件下,以鲜杂鱼(x)和配合饲料(P)为饵料,采用室内循环流水的试验方法研究饥饿后再投喂对牙鲆幼鱼补偿生长、生化组成及能量收支模式的影响.结果表明:试验组S1F5、S5F25均表现出完全补偿生长现象,且S1F5组主要通过提高摄食率(FR)来实现补偿生长,而S5F25组主要通过提高食物转化率(FCE)来实现补偿生长;经补偿生长后,各试验组鱼体的生化组成与对照组均无显著差异(P>0.05);经饥饿处理后牙鲆幼鱼生长能占摄食能的比例增加,用于排泄和代谢的比重有所下降.     

An energy budget for Porites porites (Scleractinia), growing in a stressed environment

An energy budget was determined for the coral Porites porites living in a stressed environment for comparison of the energy inputs and expenditure with those of the same species living in an adjacent clear water fore reef environment. The stressed site was characterised by higher sedimentation and lower irradiances than at the fore reef site. Zooplankton ingestion was found to be an insignificant component of the energy intake: the coral is fully autotrophic under stress conditions. The integrated 24 h rate of photosynthetic energy production on a clear sunny day was 20% higher for stressed corals compared to fore reef corals. This was largely the result of photoadaptation which resulted in increased values for and decreased values for I_k in the hyperbolic tangent function equation for the photosynthesis versus irradiance curve. The energy investment in growth of animal tissue was lower in stressed corals. The percentage translocation of photosynthase to the animal tissue remained at about 78%, but the respiration rate of the animal tissue was reduced by 3 fold. These data combined with the high rate of photosynthetic production predict a net daily energy surplus of 67% in stressed corals compared with the 45% surplus in unstressed corals. Scope for growth is reduced under stress conditions.     

An energy and water budget for a population of the arid zone scorpion Urodacus yaschenkoi (Birula 1903)

A population energy budget and water relations of the arid zone scorpion Urodacus yaschenkoi (Birula 1903) is described. The standing crop varied between 1945 and 4043 kJ in 2240 m². The annual population respiration was 191 l of oxygen or 3562 kJ. Ecological efficiencies using laboratory and field measurements of energy flow were calculated for each instar. Water loss was extrapolated from laboratory studies and was shown to be more critical to the survival of the population than energy demand.     

Monoaminergic Systems in the Hypothalamus of the Acanthopterygian Chelon labrosus (Risso, 1826), with Special Reference to the Organon Vasculosum Hypothalami

Distribution of biogenic amines in the diencephalon of the advanced teleost Chelon labrosus was investigated by formaldehyde-induced fluorescence. We have found three closely interrelated bright yellow-green fluorescent monoaminergic cell groups having numerous cerebrospinal fluid-contacting cells with dendritic processes that protrude into the lumen of the third ventricle. The most rostral of them, the organon vasculosum hypothalami, located dorsally at the mid and caudal hypothalamus level, showed under electron microscopy some monoaminergic cells and others with an abundant smooth endoplasmic reticulum. The cerebrospinal fluid-contacting processes of both cell types, in association with numerous fibres, terminal buttons and some capillaries, constitute a thick and complex intraventricular mat. The other two fluorescent regions, nucleus recessi lateralis and nucleus recessi posterioris, border the lateral and posterior recesses of the hypothalamus. The ultrastructural characteristics of the organon vasculosum hypothalami and its intraventricular mat suggest a function in the regulation of chemical changes in the cerebrospinal fluid. These monoaminergic regions probably represent three cell masses originated from a single region in primitive fish.     

Thermal responses of juvenile squaretail mullet (Liza vaigiensis) and juvenile crescent terapon (Terapon jarbua) acclimated at near-lethal temperatures, and the implications for climate change

The negative effects of climate alteration on coral reef fishes receive ever increasing attention; however, implications of rising sea temperatures on fishes inhabiting marine nursery environments are poorly understood. We used critical thermal methodology to quantify critical thermal maxima (CTmaxima) of juvenile squaretail mullet (Liza vaigiensis) and juvenile crescent terapon (Terapon jarbua) captured from shallow seagrass nursery areas around Hoga Island, southeast Sulawesi, Indonesia. We tested the hypothesis that these distantly related fishes, when acclimated to cycling temperatures, would display higher CTmaxima than groups acclimated at constant temperatures. Groups of mullet acclimated to a constant temperature of 37 °C and temperature cycles of 35 to 39 °C or 37 to 41 °C displayed statistically similar mean CTmaxima of 44.7, 44.4 and 44.8 °C, respectively. Likewise, terapon acclimated at temperature cycles of 37 to 40 °C did not display a higher CTmaxima than fish acclimated at a constant temperature of 37 °C, with both acclimation groups' mean CTmaxima equal to 43.8 °C. Acclimation to higher cycling temperatures did not result in significant upper temperature tolerance acquisition for either species; however, mullet values were significantly higher than those seen in terapon (P < 0.0001). These data suggest that mullet and terapon will not suffer direct thermal effects should shallow nursery temperature increases be marginally higher than 1-2 °C above ~ 27 °C, and they provide evidence that the upper thermal tolerance of fishes inhabiting shallow seagrass and mangrove areas can approach the biokinetic limits for vertebrate life. Tropical marine fishes inhabiting fringing nursery environments may have the upper thermal tolerance necessary to endure substantial increases in sea temperatures.