Fatty acids of the scleractinian coral Galaxea fascicularis: effect of light and feeding

In order to investigate nutritional interactions in the symbiotic scleractinian coral-zooxanthella association, fatty acids of the coral Galaxea fascicularis were analysed in two groups of cultured microcolonies. The first group was fed with Artemia sp., while the second group was starved. After an initial 1-month period during which both groups were subjected to the same normal light conditions (constant irradiance of 125 E·cm^-2·s^-1 and 14:10 h light:dark), a light cap was used to cover the aquarium and keep all the microcolonies in permanent darkness for 20 days. During the light phase of the experiment it was shown that the nutritional status lead to large variations in the percentage of saturated, mono-unsaturated and polyunsaturated fatty acids. Palmitic acid (C16:0) was the most abundant fatty acid in both groups. Important differences between fed and starved microcolonies occurred during the dark phase of the experiment. In the fed group the dark phase was characterized by a significant increase in polyunsaturated fatty acids. Particularly arachidonic acid (C20:4 n-6) became the most important fatty acid followed by docosatrienoic acid (C22:3 n-3). A slight increase in these two fatty acids was also found in the starved group but the bulk of polyunsaturated fatty acids was significantly decreased. In this group, palmitic acid remained the most important fatty acid while an increased concentration of cis-vaccenic acid (C18:1 n-7) was found at the end of the experiment. The increased concentration of cis-vaccenic acid might indicate that bacteria serve as a source of energy. While the number of zooxanthellae per milligram of protein and the chlorophyll a to protein ratio strongly decreased in the starved microcolonies immediately after the beginning of the dark period, the decrease in fed microcolonies was delayed for about 10 days. Furthermore, after 20 days of dark incubation the chlorophyll a to protein ratio was the same as measured at the beginning of the dark period. This suggests that in the dark the metabolic requirements of the zooxanthellae are in part met from the animal host through a heterotrophic mode of nutrition.Abbreviations CZ cultured zooxanthellae - FAME fatty acid methylester(s) - FDM fed dark microcolonies - FLM fed light microcolonies - MUFA monounsaturated fatty acid(s) - PUFA polyunsaturated fatty acid(s) - SDM starved dark microcolonies - SFA saturated fatty acids - SLM starved-light microcolonies - SW sea water - TFA total fatty acids     

Use of inexpensive pressure transducers for measuring water levels in wells

Frequent measurement of below ground water levels at multiple locations is an important component of many wetland ecosystem studies. These measurements, however, are usually time consuming, labor intensive, and expensive. This paper describes a water-level sensor that is inexpensive and easy to construct. The sensor is placed below the expected low water level in a shallow well and, when connected to a datalogger, uses a pressure transducer to detect groundwater or surface water elevations. Details of pressure transducer theory, sensor construction, calibration, and examples of field installations are presented. Although the transducers must be individually calibrated, the sensors have a linear response to changing water levels (r ² .999). Measurement errors resulting from temperature fluctuations are shown to be about 4 cm over a 35°C temperature range, but are minimal when the sensors are installed in groundwater wells where temperatures are less variable. Greater accuracy may be obtained by incorporating water temperature data into the initial calibration (0.14 cm error over a 35C temperature range). Examples of the utility of these sensors in studies of groundwater/surface water interactions and the effects of water level fluctuations on tree growth are provided.     

Prey capture phase of feeding behavior in the pteropod mollusc,clione limacina: neuronal mechanisms

The prey capture phase of feeding behavior in the pteropod mollusc Clione limacina consists of an explosive extrusion of buccal cones, specialized structures which are used to catch the prey, and acceleration of swimming with frequent turning and looping produced by tail bend. A system of neurons which control different components of prey capture behavior in Clione has been identified in the cerebral ganglia. Cerebral B and L neurons produce retraction of buccal cones and tightening of the lips over them — their spontaneous spike activities maintain buccal cones in the withdrawn position. Cerebral A neurons inhibit B and L cells and produce opening of the lips and extrusion of buccal cones. A pair of cerebral interneurons C-BM activates cerebral A neurons and synchronously initiates the feeding motor program in the buccal ganglia. Cerebral T neurons initiate acceleration of swimming and produce tail bending which underlies turning and looping during the prey capture. Both tactile and chemical inputs from the prey produce activation of cerebral A and T neurons. This reaction appears to be specific, since objects other than alive Limacina or Limacina juice do not initiate activities of A and T neurons.     

Predominant maternal egg care and promiscuous mating system in the Japanese filefish,Rudarius ercodes (Monacanthidae)

Synopsis Reproductive behavior of the Japanese filefish, Rudarius ercodes, was studied at the rocky reef off Koinoura, northern Kyushu, Japan, between June and October 1989. Aggressive display was observed between males, but they were not territorial. Males had four types of courtship behavior: vibrating, tail bending, leaning and nuzzle. Spawning occurred early in the morning. A female and 1–3 male(s) mated together on brown algae. Each female spawned repeatedly with an interval of 6–12 days. Females cared for eggs and embryos from just after spawning until hatching, 2–4 days. Female egg care consisted of tending and guarding. Females tended eggs by blowing water on them and by fanning them with their pectoral fins. Females guarded eggs by driving away fish passing nearby. In some cases, males also guarded eggs by staying near the eggs and driving away conspecific males. Whether a male cares for eggs with a female seems to be affected by the form of mating (pair mating or single female-multiple male mating), and the probability of further reproduction after spawning. Dominant males showed a tendency to pair with a specific female intermittently over a two-month period. Mating, however, did not always occur between members of such pairs, and mates appeared to be inter-changeable with a promiscuous mating system.     

Ecological distinctions between sympatric species of Saguinus and Sciurus

Tamarins are small New World monkeys that have been described as "squirrellike." Squirrels, along with bats and birds, are the taxa most likely to utilize resources similar to those used by primates in the tropical forest canopy. In this paper we compare differences in ecology, diet, locomotion, and habitat utilization between sympatric populations of tamarins (Saguinus oedipus) and tree squirrels (Sciurus granatensis) in Panama. Data presented indicate that although there is some degree of resource overlap, patterns of habitat utilization differ significantly. Rather than being "squirrellike," the Panamanian tamarin exhibits a pattern of locomotor and feeding behavior consistent with that found in other arboreal primates.     

The role of triiodothyronine in the regulation of synthesis rate and translatable mRNA level of fatty acid synthetase in a preadipocyte cell line

Triiodothyronine (T₃) effects on the activity, rate of synthesis and mRNA content of the key lipogenic enzyme, fatty acid synthetase, were studied in differentiating ob₁₇ preadipocytes cloned from ob/ob mouse epididymal adipose tissue. During differentiation in the presence of insulin, a 6–10-fold increase in both fatty acid synthetase specific activity and synthesis rate were reproducibly observed and occurred concomitantly. The relative synthesis rate exhibited a progressive elevation from 0.5% at confluence to a maximum level of 2% in the presence of insulin. The rate of the enzyme degradation determined by pulse-chase experiments was similar in differentiating cells and insulin-untreated cells of the same age ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, 40–42 h). Furthermore, the increase in the enzyme synthesis rate was preceded by a progressively elevating amount of mRNA encoding for this protein as detected by translation in a reticulocyte lysate cell-free system. It is thus suggested that the increment in total and neosynthesized fatty acid synthetase in essentially due to an increased enzyme synthesis, reflecting an increased relative content of its specific mRNA. T₃ included at a physiological concentration (1.5 nM) in the culture medium enhanced significantly both enzyme synthesis and its specific mRNA. The most important T₃ effect was an acceleration of both processes, a stimulation of the mRNA level being detected as early as day 3 post-confluence and maximum at day 5 when the effect on the synthetase synthesis rate and activity began to be enhanced. This suggests that T₃ would mainly affect fatty acid synthetase as a pretranslational level.     

Aspects of the biology of the euryhaline Asian cichlid,Etroplus suratensis

Synopsis Aspects of the biology of the euryhaline Asian cichlid Etroplus suratensis in a coastal lagoon of Sri Lanka were studied for a period of 15 months. Comparisons are made from the catches from the fishery of manmade, inland freshwater reservoirs. Changes in the stock structure in the sublittoral region of the lagoon indicate that recruitment takes place twice a year, during the high rainfall/low salinity periods. The feeding habits of E. suratensis were different in the two habitats. In the lagoon it fed mainly on molluscs and in the freshwater reservoirs on macrophytes. Feeding chronology based on diurnal surveys indicate that it feeds mainly during the daylight hours. The dentition of E. suratensis is adapted for both tearing and crushing (pharyngeal teeth). Distinct differences in the mean relative intestinal length between populations from the coastal lagoon and inland reservoirs were evident and these differences are correlated to their respective feeding habits. Diurnal changes in feeding activity are associated with changes in the stomach pH. The egg-diameter distribution of mature fish indicate that E. suratensis is a single spawner, that it sheds its mature eggs all at once. It is inferred that E. suratensis breeds twice a year but that an individual female is capable of spawning only once a year.     

Resource segregation among iliophagous fish in Lake St. Lucia,Zululand

Synopsis Sarotherodon mossambicus, Chanos chanos and 11 species of Mugilidae occur in Lake St. Lucia, Zululand. All are iliophagous and potential competitors. This investigation shows that although their diets overlap, competition is reduced by different feeding mechanisms which apparently result in the available food items being consumed in differing quantities. The diet of C. chanos consists chiefly of microfauna, that of Mugilidae microflora associated with sand grains and that of S. mossambicus, microflora associated with filamentous algae and benthic floc. Potential competition is also reduced because C. chanos reach peak numbers in summer whereas Mugilidae are more abundant in winter.     

Early hominid feeding mechanisms.

Three predominant influences mark the evolution of human head form: big brain, erect bipedalism, modified oral apparatus. Confusing interplay between different adaptive requirements of each feature has made explanation of skull structure extremely difficult in the past. It now seems possible to isolate each influence in early fossil forms. A model of mammalian modes of feeding adaptation is proposed in the form of a “Natural Experiment” for tighter analysis of fossil forms. Two forms of australopithecines are recognized, “gracile” and “robust.” Both had closely similar brains, both had erect bipedalism, but each had different masticatory construction. Separation of the first two similar influences isolates the adaptive differences in oral mechanics. The gracile form had a projecting oral apparatus, distinct canine and zygomatic buttresses, moderate jaw-lever development, jaw joint not unlike most higher primates, large unusual anterior teeth, moderately sized posterior teeth. The robust form had a retruded, greatly deepened oral apparatus, “dished-in” face with fused canine and zygomatic buttresses, powerful jaw-lever development, distinctively different joint construction, remarkably small anterior teeth, enormous posterior teeth. Striking evidence for extraordinary jaw movements emerges from these features in the robust form. This is strongly supported by remarkably close parallels in Ursidae: grizzly bear and giant panda.     

The influence of zooplankton food resources on the morphology of the estuarine clupeid Gilchristella aestuarius (Gilchrist, 1914)

Synopsis The body shape of the estuarine clupeidGilchristella aestuarius from the St. Lucia system is different from that of the same species in other estuaries. The morphology ofG. aestuarius is discussed in relation to long term food availability in the St. Lucia system.