A comparative study of the blood of four Tilapia species (Pisces)

The blood of 4 species of Tilapia has been examined. Mean erythrocyte count and size, hemoglobin content, and hematocrit value varied markedly among the species examined. A tendency towards a reciprocal relationship between the number of erythrocytes and their size was observed. In general, their is a correlation between the erythrocyte counts, hemoglobin content, and hematocrit value among the species examined.     

Method of estimating the standing stock of Trochus niloticus incorporating Landsat satellite data,with application to the trochus resources of the Bourke Isles,Torres Strait,Australia

The habitat of Trochus niloticus in the Bourke Isles, Torres Strait, was classified into areas of a Landsat image, using high-ratio values of green (Band 2) to red (Band 3) light, along the windward reef margins. These shallow-water (< 15 m) areas have a coral and rubble/algal pavement cover, which constitutes the optimal habitat for this gastropod. The habitat was sampled to estimate the abundance of T. niloticus. The proportion of commercial-sized individuals was estimated by measuring the basal width of all individuals in a sample. A multistage sample design incorporating three spatial scales -100 m² (transect), 1500 m² (site) and 1 km² (reef) — was used to provide variance estimates for sample-design optimisation and to provide data on the spatial variation of abundance. Most variation (68%) in abundance was within reefs and was attributable to differences in reef cover. Variations in abundance and time costs for sampling 2 and 4 m transects were compared; the 2 m transect was more efficient than the 4 m transect. The abundance estimates were combined with habitat-area estimates and the proportion of commerical-sized individuals was estimated at a standing stock of 186000 (24% precision), or 14 t of commerical-sized T. niloticus.     

Morphologie,Entwicklung und Ökologie digener Trematoden-Larven der StrandschneckeLittorina littorea

More than 6000 individuals of the snailLittorina littorea L., from 6 different localities on the coast of the German Bay (North Sea), were examined for larval trematodes by crushing their shells, an additional 6000 by isolation in small quantities of sea water. Six species of larval trematodes were found inL. littorea and described: Notocotylid larva —Cercaria lebouri Stunkard, 1932; Cercaria ofHimasthla elongata (Mehlis, 1831); Cercaria ofPodocotyle atomon (Rudolphi, 1802); Cercaria ofRenicola roscovita (Stunkard, 1932) n. comb.; Metacercaria ofMicrophallus pygmaeus (Levinsen, 1881); Cercaria ofCryptocotyle lingua (Creplin, 1825). Considering the large number of investigated snails, the trematode fauna ofL. littorea in this area is assumed to be completely known. The life cycles ofHimasthla elongata andRenicola roscovita are described. Larvae of the different trematode species show differential preferences for distinct size groups of snail hosts. Juvenile snails are not infected. No correlation exists between infection rates and sex of the hosts. Quantitative aspects of multiple infections are calculated and discussed. The incidence of larval trematodes in the investigated localities differs. Information is presented on seasonal variations of infestations and their possible causes.     

Types of larval development in marine bottom invertebrates,their distribution and ecological significance: a re-evaluation

The distribution of various types of larval development among marine bottom invertebrates has been discussed on the basis of ecological evidence by Thorson (1936, 1946, 1950, 1952) and Mileikovsky (1961b, 1965). The information at hand is reviewed anew in this paper and is re-evaluated in the light of modern pertinent literature. The interrelationships between certain larval types and their distribution are not as rigid and direct as originally assumed. This can be proved even by the copy book example of the distribution of the various forms of development among species of the coastal gastropod genus Littorina. Especially among species with wide distributional areas, local populations may exhibit greater diversity in larval types than has previously been thought. Different types of larval development have now become known to exist in different populations of opisthobranch gastropods and lamellibranchs, i.e., in invertebrate groups in which such variability had been ruled out by Thorson. Variability in the type of larval development within given species — as a function of geographical, seasonal and other environmental parameters —is also more common in other marine bottom invertebrates than formerly considered. Marine bottom invertebrates are characterized not only by the 3 main different types of larval development proposed by Thorson (pelagic, direct, viviparous), but also by a fourth type: demersal (free non-pelagic) development. This fourth type occurs at all water depths and in all geographic zones of the oceans. The most important of the 4 types is pelagic (planktotrophic) development. Thorson's rule (decrease in numbers of species possessing pelagic development from the Equator towards the Poles, and from shallow-shelf waters to greater oceanic depths) is well substantiated by new data. However, one correction is necessary: pelagic development is not completely absent in the abyssal zone, as was proposed by Thorson (1950, and later), but is represented in it by at least several species belonging to various groups of invertebrates, and is also fairly common in the bathyal zone. A detailed analysis of the distributional pattern of the different types of development of marine bottom invertebrates must further take into consideration asexual reproduction with all its different modifications. Asexual reproduction in benthonic invertebrates is ecologically significant because of its common occurrence in nature; in numerous species it is also important as a biological supplement to sexual reproduction. The vast majority of species inhabiting the shallow-shelf zone and, partly, the higher levels of the slope zone of ocean areas located roughly between the polar circles, reveals development by means of planktotrophic larval stages. In the highest latitudes and on the slopes to abyssal depths—characterized by low water temperatures, scarcity of food, increasing hydrostatic pressure and other environmental peculiarities—other types of larval development prevail and, progressively, replace pelagic development with increasing latitude or depth. The distributional patterns of the various types of development among marine bottom invertebrates form one of the most important factors determining the basic distributional dynamics of the whole benthos in all oceans, both in the geological past and at the present time.Dedicated to the memory of Professor G. Thorson —founder of modern reproductive and larval ecology of marine bottom invertebrates.     

Electrophoretic studies of serum proteins of four Tilapia species (Pisces)

The blood serum of 4 Tilapia species were analyzed electrophoretically for protein components, and the percentage of proteins in each fraction was determined. Sera from Tilapia nilotica Linnaeus, T. zillii Gervais, T. galilaea Artedi, and T. aurea (Steindachner) were studied. Characteristic protein fractions for each species were obtained. The species differed in the number of protein fractions and in the final mobilities; T. nilotica sera migrate 120 mm, T. zillii sera 95 mm, T. galilaea sera 90 mm, and T. aurea sera 118 mm. The mobilities for fractions 1 and 2 were similar for the 4 species' sera. Inter-specific differences in the amount of protein occurred. Diet may be a major contributing factor to the variations observed in the amount of total protein.     

Population genetics of Trochus niloticus and Tectus coerulescens,topshells with short-lived larvae

Trochus niloticus L. and Tectus coerulescens Lmk., two coral reef trochid gastropods that have similar life-histories including a lecithotrophic larval stage, were sampled from reefs in the northern, central and southern sections of the Great Barrier Reef (GBR) in 1991. Significant sex-ratio biases were noted, and these varied among reefs, apparently with latitude. Demographic data suggested that highly discontinuous and localized recruitment occurs. Surveys of allozyme frequencies at 12 loci revealed no significant genetic differences among populations of Trochus niloticus at any geographical scale. High gene flow between zones of the GBR was inferred, with the number of migrants per generation (N _m ) of the order of 100. Directional selection was thought to occur at one locus (GDH ^*). Genetic variability in T. niloticus (H=0.069 to 0.110, and only three loci polymorphic) was low compared with other trochids. This was thought to be due to smaller effective population size, resulting from an unbalanced sexratio, aggregative spatial distribution of adults, high variance in reproductive success, and/or the occurrence of population extinctions and recolonisations. In contrast, Tectus coerulescens exhibited significant genetic differences between zones, indicating a much lower rate of migration between populations (N _m 1 to 10), and displayed high genetic diversity (H=0.225 to 0.279). A trend for increasing genetic diversity from the northern to southern GBR was found in both species. It is not clear whether the occurrence of two contrasted population genetic structures in species with apparently similar life-histories is due to ecological or historical factors.     

The annual reproductive cycles of Uca annulipes,Portunus pelagicus and Metapenaeus affinis (Decapoda: Crustacea) from the South-west coast of India

Employing the gonad index method, the reproductive cycles of three decapod crustaceans, Uca annulipes (Latreille), Portunus pelagicus (Linnaeus) and Metapenaeus affinis (Milne-Edwards) have been studied. In these crustaceans breeding is not continuous all the year round, but extends over several months of the year with distinct peak periods of gonadal activity. The male and female reproductive cycles are not concurrent. The peak of the reproductive cycle of males occurs slightly earlier in the breeding season than that of females. These studies indicate the possibility of production of successive broods of eggs during the same breeding season. In these species, the low saline conditions of the monsoon period are unfavourable for breeding. The medium and high saline conditions during the post-monsoon and pre-monsoon months, respectively, with plenty of planktonic food for the larvae, seem to be the favourable periods for breeding activity.     

Feeding habits and food requirements of some amphipods in the Black Sea

Food composition and food requirements of four amphipod species of the Black Sea — Dexamine spinosa (Mont.), Amphithoe vaillanti Lucas, Gammarellus carinatus (Rathke), Gammarus locusta L. — were studied and an attempt made to assess the quantitative composition of the food, daily rhythms of feeding, and daily food rations. The composition of the food of the above-named amphipods is similar and consists primarily of seaweeds. Daily feeding intensity is characterized by a distinct increase during the dark period (D. spinosa, A. vaillanti); however, in G. locusta feeding intensity increases in the morning. The daily food rations of amphipods vary greatly (from 1.7 to 360% of the specimens' body weight), depending upon factors such as the kind of food, age, sex, the physiology of specimens, and the water temperature. The total quantity of food eaten by the populations of these amphipods in the coastal zone of the Black Sea amounts to 4000 g organic matter per square metre within 1 year.     

Metabolic characteristics of midwater zooplankton: Ammonia excretion,O:N rations,and the effect of starvation

The nature of protein catabolism in a wide range of species of midwater zooplankton was investigated. The weight-specific ammonia excretion rates (g NH₃–N g^–1 dry wt h^–1, y) decline exponentially with minimum depth of occurreece (MDO, x), y=163.4 x^{–0.479±0.212} (95%ci) (CI=confidence interval), when temperature is held constant. The change in ammonia excretion can be partially explained by the decrease in percent protein (%P) with MDO, %P=80.17 MDO^{–0.148±0.122 (95%ci)} The atomic O:N ratio of freshly caught zooplankters ranged from 9.1 to 91, with most measurements between 9 and 25. Detailed studies were carried out on the response of one of the species studied (Gnathophausia ingens) to starvation (28 d). After 14 d of starvation the average ammonia excretion rate declined by more than 75% to less than 1 g NH₃–N g^–1 wet wt h^–1, although the average oxygen consumption declined by only 13% within the first 7 d of starvation and then remained stable. This differential response of oxygen consumption and ammonia excretion to starvation resulted in an increase in the average O:N ratio of starved animals from an initial 33 to 165 after 21 d. The average O:N ratios of fed mysids remained below 38 during the experiment. G. ingens maintains a relatively uniform metabolic rate during starvation by relying more heavily on its large lipid stores than when being fed.     

Food composition and feeding behavior of shallow-water crinoids at Eilat (Red Sea)

The food of 3 feather-stars, Lamprometra klunzingeri Hartlaub, 1890), Heterometra savignii (J. Müller, 1841) and Capillaster multiradiatus (Linnaeus, 1758), from the shallow water of Eilat (Red Sea) was found to be composed of planktonic and semi-benthalic organisms with a strong dominance of zooplankton. Monthly analyses of stomach contents showed seasonal changes in the participation of various systematic units in the diet. Food-comprising organisms were found to be selected according to size, and those measuring up to 400 formed 90% of the diet.This research has been sponsored partly by the Oceanic Biology Branch, Office of Naval Research, U.S.A. under contract N 62558-4556 and contract F 671052 67C 0043 between the Office of N.R. and the Tel-Aviv University. It represents part of the M.Sc. thesis of the first named author (in the framework of Red Sea investigations headed by Dr. L. Fishelson).     

Ecological aspects of ophiuroids from the phytal of S. W. Atlantic Ocean warm waters

Nine species of ophiuroids — Amphipholis januarii, Axiognathus squamatus, Hemipholis clongata, Ophiocnida scabriuscula, Ophiactis lymani, Ophiactis savignyi, Ophionereis reticulata, Ophioderma appressum and Ophiothrix angulata —were collected in various habitats from the mid-littoral and upper infralittoral on the northern coast of the State of São Paulo, Brazil. The abundance of 6 species occurring in 28 species of algae was investigated. A total of 220 samples was collected at monthly intervals from April, 1969 to May, 1970. The distributional pattern of the populations, as determined by Mobisita's index, shows aggregation of the ophiuroids. No ophiuroid species was limited to one algal species. Each species prefers certain algal species and/or a different level on the shore. The most abundant species on algae was Ophiactis lymani, with a maximum density of 1,510 individuals/100 ml of algae. Four species of ophiuroids occurred inside sponges. The most abundant species in sponges was O. savignyi, with a maximum density of 1,892 individuals/100 g of dry sponge. Two species of ophiuroids occurred inside the bryozoan Schizoporella unicornis. Feeding observations have shown Axiognathus squamatus to capture its food by mucous nets. Decapod crustaceans fed on ophiuroids in aquaria. The copepod Thespesiopsyllus sp. was found in the body cavity of the 2 Ophiactis species. Simultaneous sexual and asexual reproduction were abserved in O. savignyi.     

Responses of the Indian major carp Labeo rohita to deltamethrin at acute and sublethal concentrations

The effects of deltamethrin at acute and sublethal concentrations on some hematological and biochemical profiles in the Indian major carp Labeo rohita have been examined. The lethal concentrations (LC₅₀) of deltamethrin for 24 and 96 h were found to be 0.44 and 0.38 mg L^?1, respectively. During acute treatment (24 h), hemoglobin (Hb), hematocrit (Hct), red blood cell (RBC), white blood cell (WBC), mean cellular volume (MCV), mean cellular hemoglobin (MCH), and mean cellular hemoglobin concentration (MCHC) values were significantly increased compared to control group. Plasma glucose, protein, cholesterol, albumin, globulin, triglyceride, and glycogen in gill and muscle were significantly decreased. Upon sublethal treatment (0.044 mg L^?1, 10th of 24 h LC₅₀), RBC and the biochemical parameters, except glucose and cholesterol, decreased significantly, while MCV, MCH, and MCHC values increased up to the 28th day and then declined. Cholesterol level was significantly increased throughout the study period. A biphasic response in the levels of Hb, Hct, WBC, and glucose were observed during sublethal treatment.     

On the chemical composition of the red crab Portunus pelagicus

Data are presented on yield of meat and waste from whole red crabs Portunus pelagicus (Linnaeus). The chemical composition (protein, oil, moisture, and ash) of the meat and waste portions and the amount of protein and non-protein nitrogen in the meat together with the amount of sarcoplasmic, fibrillar, and stroma protein in the protein fraction have also been investigated.     

Importance of predation by infaunal polychaetes in controlling the structure of a soft-bottom community in Maine,USA

Field manipulations in a Maine, USA intertidal mud flat showed that Nereis virens adults were an important factor in regulating the abundance of Corophium volutator, an amphipod which comprised 63% of the total number of individuals in the benthic community. Removal of N. virens adults resulted in an increase in C. volutator abundance, while addition of N. virens adults led to a decrease. There was a significant negative correlation between the abundance of N. virens adults and that of C. volutator. C. volutator was also negatively correlated with the density of all the other infaunal species combined. These results suggest that there is at least a 3-level interactive system (N. virens —C. volutator — other infaunal species) within the infauna in Maine; N. virens is a factor in controlling the abundance of C. volutator, and C. volutator may play a role in regulating the densities of other infaunal species. Models of generalized cropping in soft-bottom systems may be too simple if they ignore complex trophic relationships within the infauna.     

The influence of storage on antibacterial activity of sea water. I. Experiments with sea water stored at 18°C

Three sea-water samples of about 25 l each, stored at 18°C in the dark, were examined for antibacterial activity and bacterial content. Serratia marinorubra mainly was used as test bacterium. During storage for 197 to 454 days, bactericidal capacity varied considerably. In raw sea water, extreme log (N ₃–N ₀) values (N: number of colony-forming test bacteria/ml after 0 and 3 days of any test) were higher than-1 and lower than-4. Antibacterial activity of filtersterilized and autoclaved, stored, sea water likewise varied, but to a lesser degree. The number of colony-forming marine bacteria fluctuated about 3 orders of magnitude. Variations in bacterial content and in bactericidal action of stored sea water were positively correlated during the first months of storage; later, this correlation became negative. From these results it is concluded that variations in nutrient concentration — due to successive periods of growth and autolysis of marine bacteria — were the primary reason for the changes observed in antibacterial activity of stored sea-water samples.     

A comparative study of the toxicity of lead and its impact on the carbohydrate metabolism and some haematological parameters of cichlid fish,oreochromis niloticus and catfish,clarius gariepinus from saudi arabia

Fresh and healthy specimens of Oreochromis niloticus (mean weight 70.5± 1.23 g and mean length, 12.3± 1.5cm) and Clarias gariepinus (mean weight, 41.8±2.3 g and mean length 13.78 ± 1.2 cm) were exposed to heavy metal lead, ranging in concentration from 10 to 18 mg L^‐1 for O. niloticus and 20 to 28 mg L^‐1 for C. gariepinus respectively. The 96 h LC₅₀ for both the species was computed as 12.45 mg L^‐1 (O. niloticus) and 22.65 mg L^‐1 (C. gariepinus). The cichlid fish was exposed to sublethal concentration of lead (2, 4 and 6 mgL^‐1) and catfish (4, 8 and 12 mgL^‐1). The erythrocytes count, haemoglobin concentration, haematocrit and the value of serum glucose increased significantly (P < 0.01), whereas leucocytes count, serum protein and serum triglyceride after intoxication declined in both the species with the same pattern but in different quantity. After 96 h of time a significant depletion of muscle and liver glycogen was noted, being greater in muscle (16.7% in O. niloticus) and in liver (15.9% in C. gariepinus). The response of fish to lead was dose dependent.     

Utilisation of mangroves and seagrasses by fishes in the Negombo Estuary,Sri Lanka

In two years of sampling, 10 287 fishes belonging to 62 species (39 families) were collected from mangroves and seagrasses of the Negombo Estuary. Of the species collected, 70% were marine, 27% estuarine and 3% freshwater. Aplocheilus melastigma, Ambassis dayi, Etroplus suratensis, E. maculatus, Bathygobius fuscus and Arothron immaculatus constituted 90% of the catch. Sixteen species were caught only from mangroves, 6 only from seagrasses, and 40 from both. The number of species, individuals, biomass and diversity were higher in seagrasses than in mangroves. Gobies and some siganids moved to the mangrove habitat as they grew, but cichlids, triacanthids, some eleotrids and tetraodontids preferred seagrasses. The number of species and individuals caught increased at the beginning of the north-east monsoon when the rainfall was low. The number of species and individual numbers were positively correlated with salinity and dissolved oxygen and negatively correlated with water temperature. Of the 33 species examined, seagrasses formed >25% of the gut content in juvenile Lates calcarifer, Apogon thermalis, E. suratensis, E. maculatus, Siganus javus, Butis butis and Bathygobius fuscus. Mangrove litter was the main gut content of the family Syngnathidae. E. suratensis, E. maculatus and S. javus from seagrasses contained more filamentous algae than seagrasses in their stomachs. S. javus collected from mangroves also contained more seagrasses in their stomachs than mangrove litter, indicating that the association of juvenile fishes with mangroves or seagrasses may not be obligate in estuaries subject to low tidal fluctuations.     

Vertical distribution of euthecosomatous pteropods in the upper 100m of the Hilutangan Channel,Cebu, The Philippines

The vertical distribution of euthecosomatous pteropods in the upper 100 m of the Hilutangan Channel, Cebu, The Philippines was studied, based on 126 samples, comprising 47, 282 individuals. Thirty-min horizontal plankton tows were performed at depths of 1, 20, 50, 70 and 100 m in January and February 1972. Thirteen species —including 3 subspecies — of juvenile and adult euthecosomes were identified. In decreasing order of abundance the species are: Creseis acicula (20.4%), Limacina trochiformis (19.9%), Creseis virgula constricta (14.6%), L. inflata (10.5%), Clio pyramidata (9.9%), Creseis virgula conica (8.9%), L. bulimoides (7.3%), Diacria quadridentata (5.3%), Cavolinia longirostris (1.9%), Creseis virgula virgula (1.0%), Hyalocylix striata (0.1%), Cuvierina columella (0.08%), Cavolinia uncinata (0.002%). In 3 species, a large percentage were juveniles; for 1 species, Clio pyramidata, only juveniles were caught. The Vertical species distribution was similar to the distribution of the respective species in Caribbean and Bermuda waters. Temperature, salinity and dissolved oxygen influence vertical distribution little, if at all.     

Biomarkers of oxidative stress as indicators of water pollution in Nile tilapia (Oreochromis niloticus) from a water reservoir in Riyadh,Saudi Arabia

Antioxidant enzyme activities of fish (Oreochromis niloticus) were determined in order to assess the status of pollution in the Wadi Namar (WN), near Riyadh, Saudi Arabia. Activities of four antioxidant enzymes as superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and concentrations of glutathione (GSH) and oxidant malondialdehyde (MDA) were selected as bioindicators. Fish (n = 14) were sampled in the month of April 2013 from WN and a control site (CS). SOD activity was increased by 37.9%, 47%, and 29% in kidney, liver, and heart, respectively, while a significant decrease (36.4%) was observed in gills of O. niloticus from WN as compared to fish from CS. CAT activity was reduced by 51%, 55%, 47%, and 35% in kidney, liver, heart, and gills of O. niloticus from WN. The GST activities in kidney, liver, and heart of O. niloticus from WN were elevated by 34%, 48%, and 32%, respectively. However, significant fall (49%) in gills of fish was noted from WN compared to fish from CS. GSH levels were increased by 44%, 36%, and 38% in kidney, liver, and heart, respectively, but decreased by 30% in gills. MDA levels of O. niloticus were significantly increased in kidney, liver, and heart in fish from WN. Data indicated that WN is polluted mainly by industrial and urban discharge of liquid waste products.     

Mangrove fish-communities in tropical Queensland,Australia: Spatial and temporal patterns in densities,biomass and community structure

Regular daylight sampling over 13 mo (February 1985–February 1986) in and adjacent to intertidal forested areas, in small creeks and over accreting mudbanks in the mainstream of a small mangrove-lined estuary in tropical northeastern Queensland, Australia, yielded 112 481 fish from 128 species and 43 families. Species of the families Engraulidae, Ambassidae, Leiognathidae, Clupeidae and Atherinidae were numerically dominant in the community. The same species, with the addition ofLates calcarifer (Latidae).Acanthopagrus berda (Sparidae) andLutjanus agentimaculatus (Lutjanidae) dominated total community biomass. During high-tide periods, intertidal forested areas were important habitats for juvenile and adult fish, with grand mean (±1 SE) density and biomass of 3.5±2.4 fish m^–3 and 10.9±4.5 g m^–3, respectively. There was evidence of lower densities and less fish species using intertidal forests in the dry season (August, October), but high variances in catches masked any significant seasonality in mean fish biomass in this habitat. On ebb tides, most fish species (major families; Ambassidae, Leiognathidae, Atherinidae, Melanotaeniidae) moved to small shallow creeks, where mean (±1 SE) low-tide density and biomass were 31.3±12.4 fish m^–2 and 29.0±12.1 g m^–2, respectively. Large variances in catch data masked any seasonality in densities and biomasses, but the mean number of species captured per netting in small creeks was lowest in the dry season (July, August). Species of Engraulidae and Clupeidae, which dominated high-tide catches in the forested areas during the wet season, appeared to move into the mainstream of the estuary on ebbing tides and were captured over accreting banks at low tide. Accreting banks supported a mean (±1 SE) density and biomass of 0.4±0.1 fish m^–2 and 1.7±0.3 g m^–2, respectively, at low tide. There were marked seasonal shifts in fish community composition in the estuary, and catches in succeeding wet seasons were highly dissimilar. Comparison of fish species composition in this and three other mangrove estuaries in the region revealed significant geographic and temporal (seasonal) variation in fish-community structure. Modifications and removal of wetlands proposed for north Queensland may have a devastating effect on the valuable inshore fisheries of this region, because mangrove forests and creeks support high densities of fish, many of which are linked directly, or indirectly (via food chains) to existing commercial fisheries.Contribution No. 493 from the Australian Institute of Marine Science