Biochemical investigation of two responses involved in the feeding behaviour of Acanthaster planci (L.). III. Food preferences

The arm-withdrawal and settlement responses associated with feeding in Acanthaster planet (L.) are elicited at differing intensities by various species of coral and by extracts of these corals. There is no clear correlation between the strengths of the two responses. The preferences shown by A. planci for certain species of whole coral depend on the previous dietary experience of the starfish, and repeated presentation of an unfamiliar coral may increase its acceptability as food.     

Biochemical investigation of two responses involved in the feeding behaviour of Acanthaster planci (L.). II. Isolation and characterization of chemical stimuli

Feeding behaviour is induced in the crown-of-thorns starfish, Acanthaster planet (L.), by two kinds of chemical stimulus originating in coral. One is macromolecular, and the other of low molecular weight, largely accounted for by small peptides and amino acids.It is found that, under experimental conditions, starfish rapidly habituate to a chemical stimulus which at first strongly induces feeding behaviour.The pronounced withdrawal response which occurs when a crude extract of coral is applied to the starfish (a response apparently identical with that evoked by contact with live coral) is caused by a component which corresponds closely in chromatographie behaviour with proline. Proline itself produces the response, but is present at too low a concentration in coral to account for the observed activity.     

Biochemical stimuli for feeding in Acanthaster planci (L.)

The typical feeding response of the Crown of Thorns Starfish Acanthaster planci (L.) can be induced by mucoproteins of molecular weight greater than 200,000 daltons found in mucus obtained from corals of the genera Acropora and Fungia.     

Parental behaviour in the Mongolian gerbil (Meriones unguiculatus). I. Retrieval

Twelve pairs of Mongolian gerbils rearing 15 litters were tested for their responses to their own pups placed outside the nest area. All females and 3 of 12 males retrieved pups. Fewer pups were retrieved and more returned to the nest by themselves as the pups matured. The female's latency to retrieve pups also increased as the pups grew older. Due to retrieval by both parents and the spontaneous return of pups, few pups were left outside the nest after scattering. The possible mechanisms by which parental retrieval is elicited are discussed.     

The feeding biology of Hydrobia ventrosa (Montagu). I. The assimilation of different components of the food

The assimilation efficiencies for 7 species of diatoms, two of blue-green algae, and one bacterium have been measured in the deposit-feeding prosobranch Hydrobia ventrosa (Montagu). Two methods have been used, a chemical and a radiotracer one.The results of the first method were difficult to evaluate due to the fact that the time taken to clear the gut is ill-defined. The second method gave more consistent results.All diatoms are assimilated efficiently (60–71 %) as is the bacterium (about 75 %). The blue-green algae are less efficiently utilized; an Oscillatoria sp. was assimilated with an efficiency of about 50 % whereas a Chroococcus sp. was only assimilated with an efficiency of 8 %. It is concluded that resource partitioning based on differential utilization of micro-organisms cannot play an important rôle in the co-existence of Hydrobia ventrosa with other deposit-feeders.     

Purification and preliminary characterization of two asclepains from the latex of Asclepias syriaca L. (milkweed).

Two groups of asclepains have been isolated from Asclepias syriaca L. (milk-weed) latex and a representative of each has been purified. Asclepains A3 and B5 are homogeneous proteins with molecular weights of 23 000 and 21 000, respectively. Both require a reducing and chelating agent for maximum activity and hydrolyze ester, amide and peptide bonds. The optimum pH for hydrolysis of casein is 7.5 to 8.5 for asclepain A3 and 7.0 to 7.5 for asclepain B5. Both enzymes are autolytic when active and are inhibited by p-chloromercuribenzoate, iodoacetic acid and sodium tetrathionate. Asclepains A3 and B5 each contain one titratable SH group per molecule and no bound carbohydrate. Each of the two enzymes has leucine as the N-terminal amino acid. There are notable differences in their amino acid compositions.     

Parental behaviour in Mongolian gerbils (Meriones unguiculatus). II. Parental interactions

Twelve pairs of Mongolian gerbils were observed raising 15 litters. Both parents performed parental activities. Within pairs, associations were found between the behaviours of the parents. If one parent was active outside the nest, the other was likely to be relatively inactive in the nest. These non-random behavioural associations existed even though overall activity tendencies of members of pairs were similar. As a consequence of these patterns of behaviour, the pups were seldom left unattended, and the adaptive significance of parental presence is discussed.     

Saponins in eggs and larvae of A canthaster planci (L.) (Asteroidea) as chemical defences against planktivorous fish

The suggestion that saponins in eggs and larvae of Acanthaster planci (L.) serve as chemical defences was tested by feeding groups of planktivorous pomacentrid fish with random series of gelatin food particles, some with and some without crude saponin extract from A. planci. The four fish species discriminated at statistically significant levels against food particles with crude saponin extract at 1× 10^?3 and 1× 10^?5 parts of wet weight. Three species also discriminated at significant levels against particles with 1× 10^?7 parts crude saponin extract per wet weight. Degree of discrimination was strongly influenced by the state of hunger of the fish. Tastiness of particles containing saponins also influenced acceptability. The lower two concentrations of saponins used in these feeding trials were respectively two and four magnitudes less than in A. planci eggs and larvae. Thus, the saponins in eggs and larvae of A. planci are at levels detectable by, and unpalatable to, planktivorous fish and they account, at least in part, for the observed rejection of these early developmental stages by planktivorous fish.     

Territoriality and reproductive behaviour in the goldsinny, Ctenolabrus rupestris L.

Territoriality and reproductive behaviour of the Goldsinny, Ctenolabrus rupestris, was studied in the waters around Tjärnö on the Swedish west coast. Observations were made by SCUBA-diving and from an observation raft and in aquaria.Patrolling, foraging, courtship and aggression were defined and quantified throughout the reproductive season and after. Spawning activity was also examined and it has been found that one male spawns with several females. During spawning accesory males may be present at fertilisation and their role is discussed. Both sinking and floating eggs were recorded, which are discussed.After spawning some females became territorial as well as some subadults. The territories showed a consistency according to their boundaries and occupants from year to year.     

Inhibition of mating behaviour before feeding in the tick Aponomma hydrosauri

When on their host, both male and female adults of the reptile tick Aponomma hydrosauri require at least five days of feeding before normal mating behaviour will start. In off-host trials, fed females attract significantly more male contact than do unfed females, but unfed males show normal mating behaviour. All aspects of female mating behaviour are inhibited before feeding. Male mating behaviour has two stages: one comprises detachment and searching, the other, courtship behaviour. Only the former is inhibited before male feeding. This suggests the female signal has two components: one initiating searching, and the other initiating courtship. Males will always respond to the second component, but only after feeding will they respond to the first.     

Flock feeding and time budgets in the house sparrow (Passer domesticus L.)

A winter population of house sparrows at a farm fed on barley seed in two distinct types of habitat: cattlesheds and open fields. The risk of predation was apparently higher in the fields where birds scanned more frequently than in the cattlesheds and where scanning was negatively influenced by flock size but positively influenced by distance from cover. Individual time budgets were more influenced by flock size than by seed density in the fields but more influenced by seed density than by flock size in the cattlesheds. Higher rates of scanning resulted in greater flock vigilance and longer flight distances in the fields but flight distance was negatively influenced by the density of seeds on which birds were feeding.     

Effects of food availability on the valve movements and feeding behavior of juvenile Crassostrea Virginica (Gmelin). I. Valve movements and periodic activity

The effects of changes in the availability of algal food on the valve movements of juvenile Crassostrea virginica (Gmelin) were investigated. Individual oysters were subjected to different conditions: (1) unfed in filtered sea water; (2) continuously fed, in which oysters were given an algal suspension maintained at a constant level (50 000 cells/ml) by an automatic turbidostat; (3) discontinuously fed, where oysters were alternately fed with the turbidostat for 12 h and unfed for 12 h; and (4) batch fed, in which oysters were given specific daily rations at two ration levels (maximum and 40%). Valve movements were concurrently recorded and periods of activity (valves open) and quiescence (valves closed) measured.Oysters fed continuously remained open an average of 94.3% of the time, whereas unfed oysters were open 35.1% of the time. Discontinuously fed animals were open 95.7% of the time during the times of feeding, but 60.6% of the time during the unfed periods. Activity in the batch-fed oysters was related to the ambient algal concentration in that both the percentage time open/hour and the duration of valve openness decreased with decreasing concentration. Time series analysis of valve movements showed that oysters exhibited a 24-h periodicity of activity when subjected to a 24-h feeding schedule (discontinuous and batch groups) but exhibited no consistent periodicity under the continuous feeding or unfed conditions.     

Behavioural components of prey-selection by dogwhelks, Nucella lapillus (L.), feeding on barnacles, Semibalanusbalanoides (L.), in the laboratory

Adult dogwhelks, maintained on mussels for 60 days before experimentation to reduce prior effects of ingestive conditioning and handling skills appropriate to barnacles, and thence deemed “inexperienced”, preferred the largest barnacles presented to them. Juvenile and adult dogwhelks, maintained on barnacles and deemed experienced, preferred barnacles of intermediate sizes that were correlated with the sizes of the dogwhelks. “Inexperienced” dogwhelks penetrated barnacles significantly more often by drilling than by prising, whereas experienced dogwhelks did the reverse. A predominant tendency to prise open barnacles was developed by previously “inexperienced” dogwhelks after they had eaten six to eight consecutive prey. Larger dogwhelks prised open greater proportions of larger barnacles than did smaller dogwhelks. Experienced adult dogwhelks prised open all barnacles of ≈2-mm opercular diameter but only 20% of those ≈ 6 mm in diameter. The preferred barnacles, 4–5 mm in opercular diameter, were of a size that the experienced adult dogwhelks could prise open in 50% of attacks.Dogwhelks inspected barnacles by crawling over them for ≈20 min when the prey were subsequently rejected and ≈30 min when subsequently eaten. Penetration time and ingestion time were linear functions of barnacle diameter, total handling time ranging from 4–26 h for barnacles of 2.5–2.7 mm opercular diameter. Experienced dogwhelks handled barnacles faster than “inexperienced” dogwhelks, largely because they used the quicker method of penetration by prising whenever possible. The yield of flesh per unit handling time was an accelerating function of barnacle size and, with experience, could be increased by a factor of ≈1.2 for barnacles of 7 mm opercular diameter to ≈2.0 for barnacles of 2 mm opercular diameter. The preference of experienced dogwhelks for barnacles somewhat smaller than the largest available, may have reflected the greater frequency with which these prey could be penetrated by the quicker method of prising. Minimizing handling time could be important in nature if there is a risk to feeding dogwhelks of being displaced by competitors. In the laboratory, 12% of dogwhelks where thus displaced.Barnacles of ≈5 mm opercular diameter were estimated to be slightly more profitable than mussels of ≈17.5-mm shell length to a dogwhelk experienced with barnacles, but less profitable to a dogwhelk that has recently fed extensively on mussels. Dogwhelks, therefore, might switch between diets predominately of barnacles or of mussels if prey of comparable profitabilities change drastically in their relative abundance on the shore.     

Effects of juvenile hormone on sense organs involved in mating behaviour of Blattella germanica (L.) (Dictyoptera: Blattellidae)

Possible causes of the suppression of mating in juvenile hormone-treated Blattella germanica females, including the roles of the compound eyes and antennal, labial and maxillary palp sensilla in mating, were studied.Either antennectomy or labial palpectomy, but not maxillary palpectomy, leads to complete suppression of mating in females. Vision plays no role in mating. These results show that all the head appendages (antennae and labial and maxillary palps) are important in precopulatory behaviour, individually and collectively. Juvenile hormone treatment of the sixth (last) instar female nymphs leads to retention of nymphal sensillar characteristics on both the antennae and the palps of the resulting adults, with a reduced electroantennogram response. Thus the animal behaves like a nymph and does not mate in spite of its ability to produce pheromone.     

The control of mating behaviour in Helix pomatia L. (Gastropoda: Pulmonata)

I examined how extirpations of various parts of the reproductive system affected the mating behaviour of Helix pomatia. The integration of the sequence of activities in the mating behaviour was not affected by any of the extirpations performed. It is concluded that the sequence is mainly controlled centrally. The simultaneousness of the performance of dart shooting behaviour and the initiation of a new bout of mating activity was found to be independent of the presence of the dart. The mating activity was decreased by mechanical stimulation of the duct of the bursa copulatrix and increased by extirpation of the digitiform glands. It is concluded that the mating behaviour cycle is caused partly by mechanical effects of dart shooting and copulation.     

The effects of simultaneous variation in protein, digestible carbohydrate and tannic acid on the feeding behaviour of larval Locusta migratoria (L.) and Schistocerca gregaria (Forskal). I. Short-term studies

ABSTRACT The influence of simultaneously varying the levels in artificial diets of protein, digestible carbohydrate (14% or 28%) and tannic acid (absent or 10%) on the feeding behaviour of the oligophagous Locusta migratoria (L.) and the polyphagous Schistocerca gregaria (Forskal) (Acrididae) was investigated. Total consumption and detailed feeding behaviour were recorded over a 12 h period in choice and no-choice experiments. In addition, amounts eaten by Schistocerca of the 14% protein, 14% carbohydrate diet with and without tannic acid were measured at regular intervals throughout the fifth stadium, and insect growth over this period was recorded. There were no interactive effects of nutrient levels and tannic acid, despite the fact that both species compensated for dilution of dietary protein by increasing consumption. Only male Locusta compensated for dilution of dietary carbohydrates, and this compensation was much less marked than for protein. Tannic acid did influence feeding as a main effect, however. It caused an increase in amounts eaten by Schistocerca in both choice and no-choice experiments. This increased consumption was due to an increase in the number of meals taken. A shorter latency period before and a longer duration of the first meal by naive insects suggested a phagostimulatory rather than a post-ingestive effect of tannic acid. The stimulatory effect was only apparent for the first 24 h of continuous exposure, but this temporary enhancement none the less resulted in the insects being heavier at adult ecdysis. Stadium duration was also somewhat reduced. In a no-choice situation, no effect of tannic acid on the feeding behaviour of Locusta was observed. When given a choice, however, this species took significantly more meals on the tannic acid-free diet, these being of similar average size to meals taken on the tannic acid diet. Significantly more insects took their first meals on the tannic acid-free diet in the choice test, indicating a deterrent effect of tannic acid in Locusta.     

Ozone fumigation results in accelerated growth and persistent changes in the antioxidant system of Brassica oleracea L. var. capitata f. alba

The growth response and antioxidant capacity of Brassica oleracea var. capitata f. alba plants treated with 70 ppb of ozone was examined. Four week old cabbage seedlings were fumigated with O₃ for 3 days before being transplanted into the growing field. The effect of O₃ treatment was determined directly after fumigation and over the course of field cultivation. Plants subjected to O₃ treatment had an increased diameter of rosettes and number of leaves after 3 and 7 weeks in agriculture, respectively. In addition, the vast majority of fumigated plants reached marketable quality faster than control plants, indicating a positive role of episodes of increased O₃ concentrations during vegetation on growth and yielding.