Unstable processes in the metabolic rate measurements in flow-through systems

Measurements of metabolic rate within a flow-through system generally begin only after the difference between input and output concentration has become constant. This limits the use of such a system to objects with high metabolic rates. The processes in the flow-through system were described mathematically and the differential equations obtained are analytically resolved for different situations. They can be used for the calculation of metabolic rates for any time after the onset of measurements. The flexibility of a flow-through system and its suitability for physiological and ecological measurements are significantly increased.     

Worker population structure and gyne production in the ant Myrmica

Summary Wild colonies of Myrmica rubra L. were sampled and cultured in the laboratory to assess their reproductive capability. Correlation analysis was then used to relate the reproductive performance to a number of worker population characteristics. This revealed an association between the magnitude of gyne production and the proportion of nurses in the population. The absence of big workers also increased gyne production.Artificially composed cultures were then made and used to confirm greater resistance of nurses and small workers to queen domination.It is suggested that rapidly growing colonies will have higher proportions of young nurse workers refractory to queens and able to deliver the food necessary for gyne production. Such colonies could optimise their reproduction in this way.     

Tactics of whelks preying on limpets

Although holes drilled by the whelk Dicathais aegrota Reeve, 1846 in the limpet Patelloida alticostata (Angas, 1865) were not in the areas of thinnest shell, they were away from the margin, over the gonad and digestive gland, and in the segments where the predator fitted evenly onto the prey's shell. This complicated handling of prey provides access to energy-rich tissues and probably prevents dislodgement of the predator.     

Ethologie du stade infestant du copépode ascidicole Notodelphyidae Pachypygus gibber. I. Réactions à la lumière au cours de la vie larvaire pélagique

The phototropic reactions of pelagic larvae of Pachypygus gibber (Thorell) under laboratory conditions change according to their stage and their age. The behaviour of these larvae is described by 4 experimental parameters: threshold of the reaction, orientation towards the light or the opposite, speed and form of motility. Specimens were tested under different conditions of illumination. In the nauplii, the threshold reaction to light is higher than that in Copepodids 1 and 2. In the early planktonic stages (nauplii, Copepodids 1 and young Copepodids 2, from emergence to 3 days), most specimens respond positively to light, however the response is negative in older Copepodids 2 (4 to 10 days). There is a parallel evolution between the development of P. gibber and the change from positive to negative phototropism. The inversion of this response occurs in the developmental period between the 3-day old Copepodids 2 and the Copepodids 2 of 4 to 6 days of age. This reversal in vitro could correspond to the moment of penetration into the host. The average swimming speed is fastest in the positive phase of Copepodids 1, and is very slow in the older Copepodids 2. The form of the motility, rectilinear for most Copepodids 1, becomes increasingly winding as the Copepodids 2 grow. This random exploration of the environment would increase the possibility of finding the host. The evolution of phototropism is apparently related to the search for the host and its infestation.     

Mechanisms of photoadaptation in three strains of the symbiotic dinoflagellate Symbiodinium microadriaticum

Mechanisms of photoadaptation of photosynthesis have been studied in three strains of the symbiotic dinoflagellate Symbiodinium microadriaticum. Algal strains isolated from the clam Tridacna maxima, the sea anemone Aiptasia pulchella, and the scleractinian coral Montipora verrucosa were maintained in the defined medium ASP-8A, and were grown at irradiances ranging from 22 to 248 μE m^-2 s^-1 on a 14 h:10 h (light:dark) photoperiod at 26°C. All algal cultures were analysed during log-phase of growth. At all light levels, rates of cell division and photosynthesis were determined, as were cell volumes, pigmentation (including chlorophyll a, chlorophyll c ₂, peridinin, β-carotene and xanthophylls), and carbon and nitrogen content. Low light-induced changes in pigmentation were evident to varying degrees in all three algal strains, although alterations in the photosynthesis-irradiance relations were distinctly different in each strain. The algae from T. maxima show the least photoadaptive capability, and seem to photoadapt by changing photosynthetic unit (PSU) size. Algae from A. pulchella appear to adapt by changing PSU number, while algae from M. verrucosa appear to photoadapt by changes in the activities of CO₂-fixing enzymes or electron transport systems. These are the first observations that demonstrate functional differences in different strains of S. microadriaticum. The adaptive capabilities of the algae appear to correlate well with the ecological distribution of their respective hosts. The study was made from July 1981 through December 1982.     

Analysis of the mutual attraction in the association of the fish Cryptocentrus cryptocentrus (Gobiidae) and the shrimp Alpheus djiboutensis (Alpheidae)

The mutual attraction between the fish Cryptocentrus cryptocentrus and the shrimp Alpheus djiboutensis has been investigated experimentally. The fish is attracted to its partner visually, the shrimp is attracted chemically. The mutual attraction is reinforced by the strong negative phototactic reaction of both partners, orienting them towards the burrow.     

Variations de quelques facteurs estimatifs de la biomasse,et en particulier de l'ATP,chez plusieurs algues marines planctoniques

ATP, carbon, and nitrogen content, and cell volume have been measured in 7 marine algae in culture. Intraspecific differences are negligible during the phase of exponential growth; interspecific differences in ATP and carbon content are slight during this phase compared with those observed in the same cultures between the exponential and senescent phases. As the interspecific differences agree well with those reported for algae in situ, this leads the authors to believe that the greater part of the biomass in situ is always in a state of physiological youth. ATP content is higher in diatoms, and seems linked with silica shell synthesis. In non-silicified species, there is a significant correlation between the ATP: plasma ratio and the division rate, although the cellular volumes are quite different. In the author's opinion, ATP content allows a good estimation of biomass to be made, as well as, under controlled conditions, a suitable estimation of primary productivity; however, because of their high silica content, diatoms should be considered separately from other phytoplankters.     

Lysozyme,chitinase and exo-N-acetyl-β-D-glucosaminidase (NAGase) in lymphomyeloid tissue of marine fishes

Lymphomyeloid (haemopoietic) tissues produce or store blood cells — among these leucocytes rich in lysosomal enzymes. The thymus, unlike the other lymphomyeloid tissues found in fish, produces exclusively lymphocytes. The carbohydrate-hydrolysing enzymes lysozyme (EC 3.2.1.17), chitinase (EC 3.2.1.14) and exo-N-acetyl--D-glucosaminidase (NAGase; EC 3.2.1.30) were assayed in various lymphomyeloid tissues of the cartilaginous fish Chimaera monstrosa, Squalus acanthias, Etmopterus spinax and Raja radiata, and in the thymus of the marine teleost Lophius piscatorius. Lysozyme activity was high in the cranial lymphomyeloid tissue of C. monstrosa; in Leydig's organ (oesophageal lymphomyeloid tissue) and the spleen from E. spinax; and in Leydig's organ, the epigonal organ and the spleen from R. radiata. Little or no lysozyme activity was found in Leydig's organ and the epigonal organ of S. acanthias, or in the thymus of C. monstrosa, R. radiata and L. piscatorius. The pH optima for lysozyme activities lay between 4.8 and 5.4 when assayed photometrically. Chitinase was most active at pH 1 in Leydig's organ from R. radiata, and at pH 2.7 in the epigonal organ from S. acanthias. The chitinolytic activity in Leydig's organ of E. spinax may be due to lysozyme. The optimum for NAGase activity in Leydig's organ from R. radiata lay at pH 4.0, that from S. acanthias and E. spinax at pH 4.5. The role of the enzymes in the defense against microorganisms and parasites is discussed.