Food and feeding habits of four species of juvenile mullet (Mugilidae) in a tidal lagoon in Ghana

Juvenile mugilid fishes, Liza falcipinnis, L. dumerilii, Mugil bananensis and M. curema , which enter the Elmina Lagoon in the Cape Coast District of Ghana, have a similar diet comprising mainly bacteria, diatoms, blue-green/green algae, protozoans, detritus and particulate organic matter. No seasonal changes in the diet and feeding activity were observed. The relative gut length (intestine to standard length ratio) and diet showed no significant changes with size of fish in all the species. All four species were diurnal feeders, but their peak feeding times differed. Interspecific competition for food was possibly limited by species preferences for substrate particles of particular size range and differences in feeding chronology.     

The food and feeding habits of greenback grey mullet, Liza subviridis (Valenciennes), from different habitats and at various stages of growth

An analysis of the stomach contents of Liza subviridis at various stages of growth and from different habitat types is given. Transitions in diet with respect to size were observed. Postlarval stages of less than 12 mm standard length fed only on zooplankton. The transition to bottom feeding occurred in specimens 16–20 mm, with food items consisting of zooplankton, diatoms, detrital material and inorganic sediment. The transition was complete on attaining a length of 24 mm whereby food items comprised diatoms, detrital material, filamentous algae and inorganic sediment. The relevance of this information in aquaculture is discussed. The stomach contents of adult Liza subviridis taken from different habitat types were consistent, comprising diatoms, detrital material and inorganic sediment. Filamentous algae was also consumed where available.     

Genetic Divergence and Phylogenetic Relationships in Grey Mullets (Teleostei: Mugilidae) Using Allozyme Data

Genetic divergence and phylogenetic relationships among five species of the Mugilidae family (Liza saliens, Liza aurata, Liza ramada, Chelon labrosus, and Mugil cephalus) were investigated, in the present study, on samples taken from Messolongi lagoon in Greece, using allozyme electrophoresis. Ten enzymic systems corresponding to 22 genetic loci were assayed, among which, four were found to be polymorphic in Liza saliens, Liza aurata, and Chelon labrosus, seven in Liza ramada, while only two were polymorphic in Mugil cephalus. Several loci showed different electrophoretic patterns among the species and thus, they can be useful in species taxonomy as diagnostic markers, as well as for further evolutionary studies. It must be underlined that among them the aGPD-2* locus proved to be species-specific, while the other ones can be also used in various combinations for the same purpose. The observed heterozygosity was found to range from 0.020 to 0.051. Allele frequencies of all loci were used to estimate Nei's (1972) genetic distance, which was found to range between 0.249 and 1.171 among the five species studied. UPGMA and NJ trees, obtained by genetic distance matrix methods, as well as, a tree based on the discrete character parsimony analysis were found to exhibit the same topology. Our result show that the three species of the genus Liza are clustered together, Chelon labrosus being closer to the previous clade, while Mugil cephalus being more distinct.     

Genetic relationships of four Taiwan mullets (Pisces: Perciformes: Mugilidae)

Electrophoretic data for 19 presumptive gene loci separated Mugil cephalus from Liza spp. with Nei's genetic distance of 0.863, and from Valamugil formosae with 0.703, and from both Liza and Valamugil with 0.783. Within the genus Liza , Nei's genetic distance was only 0.237 between L. affinis and L. macrolepis.     

A key to the species of Mugilidae (Pisces) in the Northeastern Atlantic and Mediterranean, with explanatory notes

A key is given for identifying the eight species of Mugilidae of the Northeast Atlantic and Mediterranean. The use of Risso's names for four species is justified and explained and recognition is given to Tortonese's discovery that Mugil capurrii (Perugia) is a senior synonym of M. monodi Chabanaud. The relationship of Liza saliens to certain species of West and southern Africa is held to be additional support for the recognition of Protomugil Popov as a subgenus of Liza including these species. Chelon Röse, with type-species Mugil chelo Cuvier (= Chelon labrosus (Risso)), is recognized, following Jordan & Evermann (1917) and Schultz (1946), but its limits are differently conceived so as to include Crenimugil Schultz rather than Liza Jordan & Swain. The latter is held to comprise about 30 Old World species. The status of Chelon bispinosus (Bowdich) is discussed, with its bearing on possible population-differences in C. labrosus and the relationship of this species with C. crenilabis. The identity of Liza seheli (Forskål) is discussed and reasons are given for disagreeing with Wimpenny and others in applying this name to the species found at both ends of the Suez Canal zone. The latter is L. carinata (Ehrenberg in Cuvier & Valenciennes). Myxus maroccensis Mohr is believed to be a young Liza ramada.     

EFFECT OF LYSOZYME (MURAMIDASE) ON MARINE AND FRESHWATER BLUE-GREEN ALGAE1

Marine blue-green algae, Lyngbya Lagerheimii, Microcoleus chthonoplastes, Plectonema terebrans, Agmenellum quadruplicatum, and freshwater blue-green algae, Anacystis nidulans, Anabaena variabilis, Nostoc muscorura, and Oscillatoria sp. treated with lysozyme (muramidase) formed spheroplasts but not protoplasts. The time needed for spheroplast induction varied with the species. Approximate internal osmotic pressures of the blue-green algae were determined. Marine algae generally had a higher osmotic pressure than freshwater algae.     

Grazing on filamentous algae by herbivorous zooplankton

SUMMARY. 1. Feeding experiments were conducted to examine filtering rates and selectivity of a variety of zooplankton taxa (including cladocerans, copepods and a rotifer) for filamentous diatoms, green and blue-green algae.
2. Most herbivores were capable of consuming some filamentous algae at rates similar to or higher than those on unicellular algae. Only feeding of Diaphanosoma brachyurum Liéven and Moina micrura Kurz seemed to be primarily limited by the filamentous morphology.
3. Filtering rates and selectivities of most herbivores were much higher for the diatom Melosira granulata angustissima Müller than for similarly sized blue-green algal filaments, indicating that chemical factors strongly influence consumption of filamentous algae.
4. The toxic blue-green algal filament Anabaena flos-aquae De Brébisson NRC 44–1 had a much strong inhibitory effect on zooplankton feeding than other filaments. The only herbivores that were not inhibited by this strain have been shown to be resistant to blue-green algal toxins, or strongly avoided consuming the blue-green alga. These results indicate that the inhibitory effect of filamentous algae is due more to toxic or noxious chemicals than to the filamentous morphology.
5. Selectivities of zooplankton for filamentous algae were largely independent of herbivore body size. The small-bodied cladoceran Bosmina longirostris Müller had the highest selectivities for filamentous algae.     

THE ALGAE OF WAIMANGU CAULDRON (NEW ZEALAND): DISTRIBUTION IN RELATION TO pH1

The pH of the main body of thermal water and of the outlet of Waimangu Cauldron (Frying Pan Lake) is 3.8, whereas hot springs flowing into this lake are alkaline, pH 8.2–8.7. Where these waters meet there are pH gradients, and it is possible to find a series of habitats differing in pH but having approximately the same temperature (54–56 C). Where the pH is above 4.8 the blue-green alga Mastigocladus laminosus is present, and where the pH is below this value the eucaryotic alga Cyanidium caldarium is the sole photosynthetic microorganism at temperatures less than 55 C. Rocks resting on the bottom of Waimangu Cauldron surrounded by water of pH 3.8 have Mastigocladus laminosus growing on them, but measurements of pH directly in these algal mats showed that the microenvironment of the alga was actually above pH 4.8. A simple experiment showed that it is probably the rock, per se, that initiates a tiny island of alkalinity in the acid lake, permitting M. laminosus to become established. The outlet of Waimangu Cauldron is a hot acid stream which becomes progressively alkaline as it descends through Waimangu Valley, due to inflow of alkaline water from springs and a cold stream. Blue-green algae were found in this stream when the pH was greater than 5.0 and C. caldarium when the pH was less than 4.0. In one region where the pH was between 4.0 and 5.0, both blue-green algae and C. caldarium were seen, although in moribund state. These data, provide further information on the lowest pH values at which blue-green algae are able to grow.     

Phylogenetic relationships of nine mullet species (Mugilidae) in the Mediterranean Sea

Phylogenetic relationships among four genera and nine species (Mugil cephalus, Mugil soiuy, Liza ramada, Liza aurata, Liza abu, Liza saliens, Liza carinata, Chelon labrosus, Oedalechilus labeo) of the Mediterranean mullets (Mugilidae) were investigated by means of allozyme electrophoresis using a seven-enzyme system (CK*, GAPDH*, G3PDH*, IDHP*, ME*, MDH*, PGM*) comprising eleven putative loci. The highest genetic divergence was 1.299, detected between M. cephalus and L. aurata and the lowest (0.280) was found between L. carinata and L. saliens. The amount of genetic divergence between the genera Chelon and Oedalechilus did not appear to be high (0.285). In a UPGMA tree, all nine species were grouped in two main branchings. In the first branch, C. labrosus and O. labeo clustered as closest taxa and were sister group to L. ramada. The other four Liza species produced two sub-branching in this group; L. carinata branched together with L. saliens, and L. aurata branched together with L. abu. In the second branch the two species of the genus Mugil, M. cephalus and M. soiuy, clustered together and were clearly isolated from the other three genera.     

A quantitative study of calcareous stream and Tintenstriche algae from the Malham district,Northern England

The algal floras of two limestone streams and two calcareous Tintenstrichen are described and compared. The most important factor governing the distribution and abundance of species was the availability of water. Permanently wet stands, dominated by filamentous blue-green algae (Schizothrix calcicola and Phormidium incrustatum) had a greater species diversity than stands subject to frequent drying which were dominated by coccoid blue-green algae (Gloeocapsa spp.).

Significant correlations were found between S. calcicola and water pH (+ve), total species numbers and pH (+ve), filamentous blue-green algae and aufwuchs thickness (+ve) and Calothrix numbers and rock mass colonized (+ve).

The algal flora of the Tintenstrichen and the streams differed, although both developed upon the same limestone formation. The results are discussed with reference to previous work, substratum stability, aufwuchs structure, water chemistry, light and temperature.     

Pseudomonas aeruginosa Chemotaxis Associated with Blooms of N(2)-Fixing Blue-Green Algae (Cyanobacteria)

Pseudomonas aeruginosa (Schroeter) Migula, a numerically significant bacterium found during N(2)-fixing blooms of the blue-green algae (cyanobacteria) Anabaena sp. in the Chowan River, North Carolina, was chemotactically attracted to amino acids when tested in a radioassay. The bacterium was labeled with P(i), and the disintegrations per minute determined by liquid scintillation counting were proportional to the number of cells accumulating in microcapillaries containing amino acids. Positive chemotaxis was observed toward all of the amino acids tested, although the degrees of response varied. Since many nitrogen-fixing blue-green algae secrete nitrogenous compounds, this attraction may be instrumental in establishing a symbiotic relationship between this bacterium and blue-green algae in freshwater.     

Blue-green algae (cyanobacteria): prospects and perspectives

Summary Photosynthetic, prokaryotic blue-green algae (cyanobacteria) occur in a wide range of natural habitats of diverse ionic composition and as such, represent an important source of biological material for biosolar energy conversion programs using saline water. The gasvacuolate, filamentous Spirulina is grown in seminatural culture in Lake Texcoco, Mexico, as a major source of single-cell protein for animal nutrition. Pilot-scale trials in other areas of the world have also demonstrated the suitability of blue-green algae, including Spirulina, for growth under brackish conditions. The carbohydrate accumulation profiles of blue-green algae differ in isolates from freshwater, marine and hypersaline habitats, with a trend towards sucrose or trehalose accumulation in stenohaline freshwater strains grown in media containing NaCl, while euryhaline and marine forms frequently accumulate glucosylglycerol. Many halotolerant isolates from hypersaline habitats accumulate glycinebetaine in response to osmotic stress. This knowledge may provide scope for future improvement in the N₂ fixation rates of blue-green algae in saline media, using betaine-accumulating N₂-fixing strains in preference to other, saltsensitive isolates.     

Switches between zoophagy, phytophagy and detritivory of Sarotherodon mossambicus (Peters) populations in twelve man-made Sri Lankan lakes

The diet of 1200 adult Sarotherodon mossambicus [16–37 cm total length ( t.l .)] in 12 man-made Sri Lankan lakes, belonging to five different irrigational systems were studied over four climatic seasons using volumetric analysis. Food differed between seasons and reservoirs but overall, the diet consisted of 2, 2, 6 and 15 genera of diatoms, blue-green algae, green algae and animal material respectively. However, none of the S. mossambicus populations maintained either a detritivorous, phytoplanktivorous or a zooplanktivorous habit through the year. Detritivory was most common during the rainy season while phytoplanktivory predominated in the dry season. Blue-green algae were not an important constituent of the diet. Out of the 12 reservoir populations, five were predominantly detritivorous, six phytoplanktivorous and one zooplanktivorous. Detritus was completely absent in the ingested material in certain populations when they devoured animal or plant material, indicating the ability of S. mossambicus to switch from deposit to suspension feeding. The mean relative intestinal length (m.r.i.l.) of S. mossambicus ranged between 5–1 and 15–2. The m.r.i.l. decreased significantly with increasing body length: m.r.i.l. = 14–1 –0.018 T.L. ( r =–0.89; P <0.001).     

The Effect of Available Nitrate and Ammonium-Nitrogen on the Growth of Two Nitrogen-Fixing Blue-Green Algae

The effect of combined nitrogen supplied as nitrate or ammonium-nitrogenon the growth of two nitrogen-fixing blue-green algae, Nostocentophytum and Calothrix scopulorum, has been studied. Thesespecies have been isolated from marine environments. Both algaegrew as vigorously on elemental nitrogen as in the presenceof combined nitrogen. Growth was equal at all levels of nitrate-nitrogenemployed but high levels of ammonium-nitrogen proved inhibitoryor even toxic to the algae. Nostoc was slightly more susceptibleto high ammonium-nitrogen levels than was Calothrix. Increasein pH of the medium from 7.2 to 8.4 increased the toxic effectof ammonium-nitrogen although relative growth at the variouslevels of nitrate-nitrogen was not affected. The results suggestthat the different effects of ammonium-nitrogen on the growthof freshwater and marine blue-green algae may be due in partat least to the different pH levels of freshwater and marineenvironments in which the algae grow, rather than to any inherentdifference between the two groups.     

Observations of Toxic Blue-Green Algae (Cyanobacteria) in Some Scandinavian Lakes

Blooms of blue-green algae from 51 eutrophic Scandinavian lakes were investigated during the period 1978–1984, to ascertain the occurrence of toxinogenic species. Toxicity assays were performed by intraperitoneal injection of suspensions of freeze-dried algal material in mice. Toxin-producing blue-green algae were found in 30 lakes. They belonged to 11 different species of the six genera Anabaena, Aphanizomenon, Gomphosphaeria, Microcystis, Nodularia and Oscillatoria. The presence of toxinogenic strains of blue-green algae seemed quite constant in several of the localities studied. In some lakes, more than one toxic species were found to develop simultaneously. The level of toxicity showed large variation (MLD100, 6 to > 2500 mg/kg), but clinical and pathological changes were quite uniform. The results indicate that water-blooms of toxin-producing blue-green algae, in the geographical area in question, are regionally widespread. In some localities, blooms of blue-green algae are apparently always toxic. Several aspects of the toxic blue-green algae problem are discussed.     

Pseudomonas aeruginosa Chemotaxis Associated with Blooms of N2-Fixing Blue-Green Algae (Cyanobacteria)

Pseudomonas aeruginosa (Schroeter) Migula, a numerically significant bacterium found during N₂-fixing blooms of the blue-green algae (cyanobacteria) Anabaena sp. in the Chowan River, North Carolina, was chemotactically attracted to amino acids when tested in a radioassay. The bacterium was labeled with ³²P_i, and the disintegrations per minute determined by liquid scintillation counting were proportional to the number of cells accumulating in microcapillaries containing amino acids. Positive chemotaxis was observed toward all of the amino acids tested, although the degrees of response varied. Since many nitrogen-fixing blue-green algae secrete nitrogenous compounds, this attraction may be instrumental in establishing a symbiotic relationship between this bacterium and blue-green algae in freshwater.     

Effect of Temperature on Blue-Green Algae (Cyanobacteria) in Lake Mendota

The temperature optimum for photosynthesis of natural populations of blue-green algae (cyanobacteria) from Lake Mendota was determined during the period of June to November 1976. In the spring, when temperatures ranged from 0 to 20°C, there were insignificant amounts of blue-green algae in the lake (less than 1% of the biomass). During the summer and fall, when the dominant phytoplankton was blue-green algae, the optimum temperature for photosynthesis was usually between 20 and 30°C, whereas the environmental temperatures during this period ranged from 24°C in August to 12°C in November. In general, the optimum temperature for photosynthesis was higher than the environmental temperature. More importantly, significant photosynthesis also occurred at low temperature in these samples, which suggests that the low temperature alone is not responsible for the absence of blue-green algae in Lake Mendota during the spring. Temperature optima for growth and photosynthesis of laboratory cultures of the three dominant blue-green algae in Lake Mendota were determined. The responses of the two parameters to changes in temperature were similar; thus, photosynthesis appears to be a valid index of growth. However, there was little photosynthesis by laboratory cultures at low temperatures, in contrast to the natural samples. Evidence for an interaction between temperature and low light intensities in their effect on photosynthesis of natural samples is presented.     

Measurement of photorespiration in algae

The rates of true and apparent photosynthesis of two unicellular green algae, one diatom and four blue-green algae were measured in buffer at pH 8.0 at subsaturating concentrations of dissolved inorganic carbon (13-27 micromolar). Initial rates of depletion from the medium of inorganic carbon and ¹⁴C activity caused by the algae in a closed system were measured by gas chromatography and by liquid scintillation counting, respectively. The rate of photorespiration was calculated as the difference between the rates of apparent and true photosynthesis. The three eucaryotic algae and two blue-green algae had photorespiratory rates of 10 to 28% that of true photosynthesis at air levels of O₂. Reduction of the O₂ level to 2% caused a 52 to 91% reduction in photorespiratory rate. Two other blue-green algae displayed low photorespiratory rates, 2.4 to 6.2% that of true photosynthesis at air levels of O₂, and reduction of the O₂ concentration had no effect on these rates.     

Dactylosoma hannesi n. sp. (Dactylosomatidae,Piroplasmia) Found in the Blood of Grey Mullets (Mugilidae) from South Africa1

ABSTRACT. A new species of Dactylosoma (Dactylosomatidae, Piroplasmia), for which the name Dactylosoma hannesi n. sp. is proposed, was discovered in blood erythrocytes of Mugil cephalus, Liza richardsoni, and L. dumerili (Mugilidae) from Swartkops estuary, located east of Port Elizabeth, South Africa. The life cycle of this species differs in some respects from that described for all other known species of Dactylosoma and Babesiosoma. Mature schizonts contain eight nuclei but undergo division only to two to four daughter cells. During cytoplasmic cleavage, schizonts assume triad, rosette, or cruciform shapes. Merozoites are finally produced through a series of binary fissions of these daughter cells which may also be involved in additional nuclear divisions.     

Antimicrobial effects of Cellvibrio on blue-green algae

Summary The culture fluids from two Cellvibrio strains, in the stationary phase of growth, are shown to contain heat-resistant, low molecular weight substances with antibiotic-like effects on blue-green algae. Morphological changes and lysis of cells were observed in various species of blue-green algae; ultrastructural changes were noted in the cell walls of growing vegetative cells of Anabaena inaequalis. The viability of resting cells, including heterocysts and akinetes was not affected.