Pheromones linked to sexual behaviors excite the appetitive phase of feeding behavior of Aplysia fasciata. I. Modulation and excitation of appetitive behaviors

Pheromones presumably secreted by mating conspecifics – as well as homogenates containing tissue that is homologous with the atrial gland – increase the time that Aplysia fasciata spend feeding. This effect is caused by increasing the number of feeding episodes initiated in response to food, whereas the duration of a feeding bout remains unchanged. The increase in the number of feeding episodes is related to increases in head waving and crawling, i.e., appetitive movements that bring the animal into contact with food, as well as an increase in the responsiveness to food after it is contacted. Releasing a homogenate containing atrial gland tissue, or egg laying hormone, in the water near the animal elicited head lifting similar to that seen when animals are food aroused. The data indicate that the facilitation of Aplysia feeding caused by pheromones arises in part by an excitation of appetitive behaviors. These findings suggest that neurons generating appetitive behaviors will be affected by pheromones. Accepted: 28 November 1997     

Direct enzymatic glucosylation of naringin in grapefruit juice by alpha-D-glucosidase from the marine mollusc Aplysia fasciata

The enzymatic glucosylations of naringin, performed using alpha-D-glucosidase, identified in the Mediterranean mollusc Aplysia fasciata is reported. The enzyme actively operates on maltose and has an interesting transglycosylation potential using this donor. We also investigated the use of this marine alpha-glucosidase for a food-compatible glucosylation of naringin to produce new enzymatically modified carbohydrate possessing naringin derivatives. The regioselective formations of the beta-gluco-C6 alpha-glucosyl derivative and of the corresponding isomaltosyl diglucoside of naringin were obtained in high yield and efficiency of reaction. Suspensions of naringin can be used up to approximately 90 mg/mL initial acceptor concentration. In different experiments it was demonstrated that the enzyme was still active after 48 h in presence of this high amount of acceptor and that one of the diasteromers of the naringin is preferred by the enzyme from A. fasciata during glucosylation/deglucosylation enzymatic steps. Finally, the feasibility of efficient naringin glucosylation in grapefruit juice was also demonstrated at optimal pH of the enzyme and low maltose concentrations.     

Ingestion motor programs of Aplysia are modulated by short-term synaptic enhancement in cerebral-buccal interneuron pathways

In the sea slug Aplysia, buccal synapses of cerebral-buccal interneurons (CBIs) CBI-2 and CBI-12 exhibit short-term synaptic enhancement (STE), including frequency-dependant facilitation and augmentation/post-tetanic potentiation (AUG/PTP). The STE that results from driving CBI-2 or CBI-12 is associated with significantly decreased latency to burst onset in buccal premotor neurons and motor neurons, increased cycle frequency of ingestion buccal motor programs (iBMPs) and increased intraburst firing frequency of buccal neurons during iBMPs. Tests of paired-pulse facilitation during AUG/PTP suggest that the locus for this plasticity is presynaptic. The AUG/PTP is not elicited by heterosynaptic pathways, indicating that its origin is homosynaptic. At low CBI-2 and CBI-12 firing frequencies, STE is likely to contribute to iBMP initiation, while at higher firing frequencies, STE is correlated with increased cycle frequency of iBMPs. Thus, STE is an important component of the mechanisms whereby cerebral neurons regulate cyclic feeding programs and likely contributes to observed variations in behavioral responses, including feeding arousal. Electronic Publication     

Consummatory feeding movements in Aplysia fasciata are facilitated by conspecifics with access to mates, by reproductive tract homogenates and by bag cell peptides

In Aplysia fasciata, pheromones released by conspecifics with access to mates increase the quantity of food eaten. This effect is blocked when the chemosensory rhinophores are ablated, indicating that the rhinophores sense pheromones. The modulation of feeding by pheromones can be monitored by an increase in the amplitude of swallowing movements in the presence of conspecifics with access to mates. Atrial gland homogenates and four bag cell peptides (egg-laying hormone, and α, β, and γ bag cell peptides) amplify the swallow amplitude in a manner similar to that caused by conspecifics with access to mates, suggesting that peptides from the bag cell/atrial gland family that are released from the atrial gland into the surrounding water may be pheromones regulating feeding and reproductive behaviors. Accepted: 14 June 1997     

Patterned jaw movements and the motor neuron activity during rejection of seaweed in Aplysia kurodai

Japanese Aplysia kurodai feeds well on Ulva. In the present experiments we collected several species of seaweed at a location with many animals and initially explored the preference behavior for them. The animals rejected Grateloupia, Pachydictyon, Gelidium and Laurencia with rhythmic jaw and radula movements (active rejection). The animals sometimes bit off a piece of them (biting-off response). Recording activity of muscles contributing to jaw-opening and jaw-closing in freely moving animals showed that the onset of the jaw-closing activity, which always started later than the jaw-opening activity during each cycle of ingestion of Ulva, was advanced toward that of the jaw-opening activity during each cycle of the active rejection. Semi-intact experiments also showed that application of Pachydictyon or Gelidium extract to the lip region advanced the firing onset of the jaw-closing motor neurons at the radula-retraction phase. Video analysis showed that during the Ulva response the jaws opened at the radula-protraction phase and remained half-open at the earlier radula-retraction phase, while the jaws opened similarly at the radula-protraction phase but immediately closed at the radula-retraction phase during the Pachydictyon or Gelidium response. Accepted: 8 October 1997     

Respiratory pumping in Aplysia fasciata as part of an integrated defensive response to increases and decreases in seawater concentration

Much of the neural circuitry controlling respiratory pumping in Aplysia has been well characterized, but the function of this movement is incompletely understood. To gain insight into possible functions of respiratory pumping, responses were examined for a 40 min exposure to two stimuli that modulate the movement: 1) increase and 2) decrease in seawater concentration. Thresholds were present for both stimuli to affect respiratory pumping. Above threshold, there were graded increases in the number of pumps elicited. There were decrements in respiratory pump frequency as a function of time exposed to the stimulus. Increased respiratory pumping did not contribute to volume regulation in response to exposure to altered seawaters, but was associated with increased defensive responses, such as escape locomotion (swimming) and inking. In addition, head shock, a well-established noxious stimulus, elicited temporal patterns of respiratory pumping similar to those elicited by altered seawaters. The data indicate that in our experimental conditions, respiratory pumping is elicited as part of an integrated defensive response to noxious seawaters.     

Mating patterns of a sphragis-bearing butterfly,Luehdorfia japonica leech (Lepidoptera: Papilionidae), with descriptions of mating behavior

Mating frequency of both sexes in a natural population of the papilionid butterfly Luehdorfia japonica was studied with special attention to the role of sphragis in preventing multiple matings by females. Males patrolled continuously within a patchy habitat throughout the warm daylight period in search for females. Mating took place without specialized courtship behavior. Males also attempted to copulate forcibly with previously mated females, but the presence of sphragis and/or the escape reaction of females prevented copulation. There was no specialized mate rejection behavior. Females mated early in their adult life, mainly on the day of emergence, and the frequency of mated females reached 100% within the first two or three weeks of their flight period. Spermatophore counts based on dissections of wild females possessing a sphragis indicated that they had never remated. Males were sexually active throughout their adult life. Male mating frequency was estimated from an index of scale-loss from the claspers and frequencies of males which had not mated, and those which had mated once, twice or three or more times were respectively estimated to be 33.7%, 40.3%, 18.2% and 7.8%.     

Prolonged mating in the melon fly,Dacus cucurbitae (Diptera: Tephritidae): Competition for fertilization by sperm-loading

Summary Males of the melon flyDacus cucurbitae mate with females for 10 hours or more, usually starting at dawn and terminating at dusk. We tested the sperm-loading hypothesis (Dickinson, 1986) that males remaining with females for long periods of time benefit by numerically overwhelming the sperm of their competitors. The amount of sperm transferred to a female increased with time after mounting. The number of feamles which laid eggs at least once during experimental periods was positively correlated with mating duration. Oviposition rate was positively correlated with mating duration, as well. Egg hatchability was not influenced by mating duration. Mating duration was a major determinant of paternity when females were doubly mated with one male for 6 hours and another male for 2 hours. Females whose first matings were longer showed first male sperm predominance, while females whose second matings were longer showed last male sperm predominance. The adaptive significance of prolonged mating by male melon flies is discussed.     

Economy of food utilization in a gregarious sawfly,Arge nigrinodosa Motschulsky (Hymenoptera: Argidae): Relative abundance of food in the natural habitat and behavioral pattern of larval feeding

Summary Relative abundance of natural food resource, leaves of wild rose, ofArge migrinodosa was evaluated by comparing the food quantity which the larvae composing a colony utilized throughout the larval stage with that which is available in the habitat. In this connection, behavioral pattern of larval feeding was also observed under natural conditions, and its ecological significance was discussed. It was quantitatively clarified that the larvae faced the severe shortage of food and had to disperse to other shoots with the expense of probably high risk. Under pressures of such insufficient supply of food, the larvae follow the most efficient pattern of feeding behavior that they move to the tip of shoot at first and feed regularly downward thereafter. Though individual larvae behaved completely independently of each other, the aggregation appeared to be formed and maintained because all the larvae from the same egg mass follow this fixed feeding pattern.     

Specializations and limitations in the utilization of food resources by the carp,Cyprinus carpio: a study of oral food processing

Synopsis The wide variety of aquatic food is considered to be instrumental for the diversification in fish species. Yet their abilities and inabilities of handling food are poorly known. For these reasons the food processing and feeding repertoire of the adult carp, Cyprinus carpio, fed on a variety of food types, were analyzed by light and X-ray cinematography of the head parts and by electromyography of the head and body muscles during feeding. Nine stereotyped movement patterns (particulate intake, gulping, rinsing, spitting, selective retention of food, transport, crushing, grinding and deglutition) compose the feeding process, their sequence and frequency were adjusted to the type of food. Following quantitative morphological analysis at macroscopic, light- and electronmicroscopical level, the relations between the functioning and architecture of the feeding apparatus were established. The structure and dimensions of the mouth opening, the protrusible upper jaw, the slit-shaped pharyngeal cavity, the palatal and postlingual organ, the branchial sieve, the pharyngeal masticatory apparatus and the distribution of taste buds, mucous cells and muscle fibers along the oropharyngeal surface were the directive structural characters used for estimating the abilities in food processing. The specializations for utilizing food items and its limitations, derived from structural and functional data, are compared with diet data found in the literature in order to evaluate the relative position of the carp in competition for food in the aquatic environment. It is established that the ‘omnivorous’ carp is specialized in effective handling of several categories of aquatic food, even when these are mixed with non-food (bottom invertebrates <4% SL in diameter) since the palatal organ enables the carp to separate food from non-food. This includes very hard-skinned food items, processed with the powerful pharyngeal jaws of the fish, and to a lesser extent zooplankton (>250 μm). The carp is at the same time very limited in processing long and struggling prey (e.g. fish) as well as vegetable matter, due to the lack of oral teeth and the specialized morphology of its pharyngeal chewing apparatus. These feeding abilities agree with diet data from literature. The reported herbivorism of carp illustrates its opportunism in feeding behaviour. Specialization in feeding is discussed and the necessity to take into account the total series of post-capture feeding actions for a more complete view on trophic specialization. Food intake and the intra-oral food processing of carp are bound to the structures of its sensory, central processing and effector apparatus and to the plasticity in their functioning. These together determine its feeding efficiency in exploiting the available aquatic food resources. Next to ethological and ecological studies functional morphology is another important tool to explain the trophic interactions of fish.     

Experimentally induced sickness decreases food intake, but not hoarding, in Siberian hamsters (Phodopus sungorus)

A wide range of physiological and behavioral alterations occur in response to sickness. Sickness behaviors, rather than incidental by-products or side-effects of acute illness, serve as adaptive functional responses that allow animals to cope with a pathogenic challenge. Among the more salient sickness behaviors is a reduction in food intake; virtually all sick animals display marked decreases in this behavior. Food intake, however, is only one component of the food-related behavioral repertoire. For many mammalian species, food hoarding represents a substantial portion of the total energetic budget. Here we tested the effects of experimental sickness on food hoarding and food intake in a naturally food hoarding species, Siberian hamsters (Phodopus sungorus). Adult male and female hamsters received injections of lipopolysaccharide (LPS) to induce sickness or control injections. LPS-induced sickness resulted in a marked decrease in food intake in both males and females, but did not decrease hoarding in either sex. These results support previous findings suggesting that food hoarding and food intake appear to be differentially regulated at the physiological level.     

Multiple mating reduces male survivorship but not ejaculate size in the polygamous insect Stenomacra marginella (Heteroptera: Largidae)

In polygamous species, successful males should be able to inseminate multiple females, to defeat sperm from previous males, to avoid sperm displacement by other males, and to induce females to use his sperm during fertilization. Since resources are limited, adaptations to perform any of these functions may conflict with each other (and with other life-history traits) and trade-offs are expected to evolve. We studied if males of the polygamous true bug Stenomacra marginella face a trade-off between multiple mating and survivorship, by comparing the survivorship of virgin and multiply mated males. We also looked for physiological costs of ejaculate production by examining ejaculate production in consecutive matings in multiple mated males. Multiply mated males were able to produce ejaculates of similar size in up to six consecutive copulations but they had decreased survivorship in comparison with virgin males. There was no difference in survivorship between males mated three and six consecutive times, suggesting that the negative relation between survivorship and number of copulations is not linear. The decrease in survivorship seems to be a cost of mating and ejaculate production. This cost could favor the evolution of prudence in the allocation of resources to ejaculate production (e.g., cryptic male choice).     

Characterization of neuronal regeneration in the abdominal ganglion of Aplysia californica

The ability of neurons in the abdominal ganglion of Aplysia to regenerate their axons following branchial nerve crush was studied using retrograde staining and intracellular dye injection. The duration of the gill withdrawal reflex (GWR) was measured prior to and following nerve crush. Three days after crushing the nerve, the duration of the gill withdrawal reflex was reduced to 20% of control levels. There was rapid recovery 19 days after crushing the branchial nerve. The GWR duration returned to control levels by postlesion days 25–27. Some of the behavioral recovery can be attributed to axonal regeneration. Regeneration, as evidenced by retrograde staining, was first observed by postlesion day 15. The number of stained neurons in ganglia with crushes increased until postlesion day 33. The number of stained neurons in experimental animals was always less than that of controls (67 ± 9% at postlesion day 56). More axonal regeneration was seen in the hemiganglion ipsilateral to the branchial nerve. Regeneration after 32 days postlesion was 60 ± 5% of controls in the ipsilateral hemiganglion, as opposed to 29 ± 6% in the contralateral hemiganglion. Regeneration of individual neurons was also demonstrated. Identified neuron R2 was shown by intracellular dye injection and electrical stimulation of antidromic action potentials to have an axon in the branchial nerve in all ganglia allowed to regenerate for longer than 32 days. These results indicate that in Aplysia, despite behavioral recovery, complete axonal regeneration does not occur in a large segment of the neurons in the adult central nervous system. © 1998 John Wiley & Sons, Inc. J Neurobiol 35: 160–172, 1998     

Effects of food nitrogen content and concentration on the forms of nitrogen excreted by the calanoid copepod, Acartia tonsa

Nitrogen excreted as ammonium, urea, and dissolved primary amines (DPA), and nitrogen ingested by the planktonic calanoid copepod, Acartia tonsa, were measured while fed 4 foods with different N/C ratios in high (500 μg C l^− 1) and low (50 μg C l^− 1) concentrations. Adult copepods were fed the ciliate, Uronema marinum (N/C = 0.26), the diatom, Thalassiosira weissflogii, in log-phase growth (N/C = 0.20), and in senescent-phase growth (N/C = 0.12), and detritus derived from the saltmarsh grass, Spartina alterniflora, (N/C = 0.04). Total nitrogen excreted ranged from 0.06 to 0.18 μg N copepod^− 1 d^− 1 whereas nitrogen ingested exhibited considerably more variation (0.01 to 0.39 μg N copepod ^− 1d ^− 1). Ammonium was the dominant form of nitrogen excreted and was influenced by both food concentration and N/C ratio. Copepods fed foods with N/C ratios resembling their own body composition (log-phase diatoms and ciliates) excreted more ammonium when fed higher concentrations of food. In contrast, copepods fed foods with lower N/C ratios than their own body composition excreted more ammonium when fed lower concentrations of food, suggesting that they were catabolizing body protein for survival. Excretion of urea varied with food N/C ratio, with more urea excreted when the copepods were fed higher N/C foods. The excretion of DPA did not vary with either food concentration or food N/C ratio. Homeostasis serves to conserve the N/C ratio of copepods. Thus nitrogen excretion by healthy copepods should be expected to increase with ingestion only when copepods have high quantities of nitrogen-rich foods relative to the body composition of the copepods.     

Pheromones linked to sexual behaviors excite the appetitive phase of feeding behavior of Aplysia fasciata II. Excitation of C-PR, a neuron involved in the generation of appetitive behaviors

Pheromones presumably released by conspecifics amplify both the appetitive and the consummatory components of feeding in Aplysia. These effects can be mimicked by administering homogenate of the large hermaphroditic duct containing atrial gland tissue, as well as peptides from the bag cells. Identified cerebro-pedal regulator (C-PR) neuron is thought to command various behaviors that comprise the appetitive phase of feeding. In a reduced preparation, we investigated the effects on the C-PR of applying these substances to the rhinophores, the sensory organs which detect pheromones. Stimuli that excite feeding in the animal were also found to affect the C-PR. Large hermaphroditic duct homogenate caused a doubling in the firing rate of the C-PR, and amplified the response of the C-PR to other excitatory stimuli, such as touch of food to the rhinophores. Bag cell peptides (α, β and γ bag cell peptide, and egg-laying hormone) caused smaller increases in the firing rate of the C-PR. These data are consistent with the hypothesis that pheromones facilitate appetitive feeding behavior in part via their excitation of C-PR. Accepted: 28 November 1997     

雄性麋鹿的交配机会、社会等级和皮质醇水平

我们在北京麋鹿苑研究了发情期雄性麋鹿的社会行为、社会等级和血清皮质醇水平,并分析了三者间的相互关系。按照雄性麋鹿的行为,将雄性麋鹿分为优势群和从属群。优势群包括群主和挑战者,从属群包括单身汉和被淘汰群主。使用SJ—Ⅰ型事件记录器进行常规行为取样,用放射免疫分析法测定血清皮质醇含量。发现：(1)优势雄鹿的发情行为频次明显高于从属雄鹿;(2)攻击行为的发生频次在两组间无显著差异;(3)血清皮质醇含量在两组间也无显著差异。由此我们认为,发情期雄性麋鹿的社会等级序位影响许多行为的表达,优势雄鹿成功交配的机会比从属雄鹿多。而攻击行为和肾上腺皮质醇的分泌与社群等级无明显相关,可能是麋鹿在圈养状态下的一种适应策略,这将有利于缓解发情期雄鹿的紧张,从而允许更多的能量投放在发情交配上。     

Omnivory and the stability of food webs

The ecological concept of omnivory, feeding at more than a single trophic level, is formulated as an intermediate stage between any two of three classical three-dimensional species interaction systems-tritrophic chain, competition, and polyphagy. It is shown that omnivory may be either stabilizing or destabilizing, depending, in part, on the conditions of the parent systems from which it derives. It is further conjectured that the tritrophic to competition gradient cannot be entirely stable, that there must be an instability at some level of intermediate omnivory.     

Food hoarding,but not food intake,is attenuated by acute diazepam treatment in female Mongolian gerbils (Meriones unguiculatus)

This article is part of a Special Issue “Energy Balance”. Effects of γ-aminobutyric acid (GABA) on food hoarding are unknown in rodents, and the effects of energy balance and GABA have not been evaluated in females. To evaluate the role of food deprivation and GABA on food hoarding, female Mongolian gerbils were given i.p. injection of diazepam (1 mg/kg and 3 mg/kg, respectively), a GABA_A receptor agonist. Among food-deprived females, there was a bimodal pattern in the frequency of gerbils with different levels of food hoarding. High food hoarding (HFH) and low food hoarding (LFH) gerbils were analyzed. Diazepam blocked food deprivation-induced food hoarding in HFH gerbils, but not in LFH gerbils. This blockade was associated with increased cellular activation in selected brain areas, such as the nucleus accumbens (NAcc), caudate putamen (CP) and ventral tegmental area (VTA), which suggested that direct activation of GABA in the brain reward circuitry decreased food hoarding in HFH females. Moreover, diazepam increased Fos expression in field CA₂ and CA₃ of the hippocampus, but had no significant effect on Fos expression in field CA₁ and dentate gyrus (DG) of the hippocampus, indicating that the hippocampus has area-specific effects on food hoarding in HFH gerbils. Diazepam did not alter food intake in both HFH and LFH gerbils. In addition, serum corticosterone concentrations were higher in the HFH than in the LFH ones. Together, these data indicated that food deprivation increased food hoarding in female gerbils, diazepam reduced food deprivation-induced food hoarding in HFH gerbils, and that GABA might influence food hoarding via classical reward circuitry via the mesolimbic dopamine system and specific hippocampal areas.     

Identification of an Acidic Dipeptide, β-Aspartylglycine, in the CNS of Aplysia

Abstract: A novel dipeptide, (β-aspartylglycine (β-DG), has been isolated from tissues of the marine gastropod mollusc Aplysia californica. This compound was detected only in Aplysia and not in other molluscs, such as Helix or Mercenaria , or in lobster or frog. Among the Aplysia tissues, the highest levels of β-DG were in nervous tissue and in the reproductive tract. β-DG was assayed by HPLC as the o -phthaldialdehyde derivative and found to be present in all individual, identified neurons at a concentration of approximately 40 pmol/μg protein. The peptide was identified as β-DG by gas chromatography-mass spectrometry (GCMS) using trimethylsilyl derivatives prepared before and after acid hydrolysis. It was further characterized as the β-isomer by TLC, including R_f, atypical blue-gray color with ninhydrin, and a violet color with Cu²⁺-ninhydrin. A fractionation scheme is described whereby acid-soluble tissue constituents can be divided into acidic, neutral, and basic components using mini ion-exchange columns. This partial purification prior to TLC analysis was necessary to remove compounds that interfered with the isolation of β-DG.     

Aggregate formation and the impairment of long-term synaptic facilitation by ectopic expression of mutant huntingtin in Aplysia neurons

Huntington's disease (HD) is caused by an expansion of a polyglutamine (polyQ) tract within huntingtin (htt) protein. To examine the cytotoxic effects of polyQ-expanded htt, we overexpressed an enhanced green fluorescent protein (EGFP)-tagged N-terminal fragment of htt with 150 glutamine residues (Nhtt150Q-EGFP) in Aplysia neurons. A combined confocal and electron microscopic study showed that Aplysia neurons expressing Nhtt150Q-EGFP displayed numerous abnormal aggregates (diameter 0.5-5 microm) of filamentous structures, which were formed rapidly (approximately 2 h) but which were sustained for at least 18 days in the cytoplasm. Furthermore, the overexpression of Nhtt150Q-EGFP in sensory cells impaired 5-hydroxytryptamine (5-HT)-induced long-term synaptic facilitation in sensori-motor synapses without affecting basal synaptic strength or short-term facilitation. This study demonstrates the stability of polyQ-based aggregates and their specific effects on long-term synaptic plasticity.