Connections of brainstem respiratory nuclei studied by the retrograde horseradish peroxidase axon transport method

Intrabulbar connections of respiratory nuclei and the medullary reticular formation and also descending pathways from these structures in the spinal cord were studied by the retrograde horseradish peroxidase axonal transport method in cats. Neurons of the nucleus ambiguus and nucleus retroambigualis (ventral respiratory group) and of the ventrolateral part of the nucleus of the tractus solitarius (dorsal respiratory group) were shown to form direct two-way connections with each other and with the medial region of the medulla. Neurons of the pneumotaxic center send uncrossed axons to the nucleus ambiguus and to the medial medullary reticular formation. Neurons of the contralateral homonymous nucleus and neurons of the nucleus of the tractus solitarius are sources of projections of the locus coeruleus. A well developed system of direct connections was found between neurons of respiratory nuclei of the two halves of the brain. The possible role of these nuclear formations in genesis of the respiratory rhythm and regulation of the respiratory and other motor functions of the reticular formation is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 14, No. 2, pp. 149–157, March–April, 1982.     

The mechanism of acoustic transmission in birds

Neuronal activity of the medullary nuclei in response to acoustic stimuli was studied by electrophysiology. Neuronal activity was recorded from three nuclei: magnocellular, angular, and laminar. Both tonic and phasic neurons of all nuclei demonstrated a strict dependence of their discharge on temporal patterns of acoustic stimuli. The medullary nuclei translated useful information on the duration of individual syllables and intervals. The obtained data are discussed in the context of acoustic transmission mechanisms and the intraspecific, interspecific, and interclass levels.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 2, 2005, pp. 189–200.Original Russian Text Copyright © 2005 by Zvonov.     

Distribution of horseradish peroxidase-labeled neurons giving rise to descending fiber systems in the basal ganglia and hypothalamus in cats

The distribution of neurons giving rise to various descending fiber systems to brain-stem structures in the basal ganglia (including amygdaloid nuclei) and hypothalamus of the cat was studied by the retrograde axonal transport of horseradish peroxidase method. Neurons in the medial part of the central nucleus and of the magnocellular part of the basal nucleus of the amygdaloid group were shown to send axons to the dorsal hippocampus, substantia nigra, lateral part of the central gray matter, and the mesencephalalic reticular formation and also to the region of the locus coeruleus and the lateral medullary reticular formation at the level of the inferior olives. The predominant source of projections to the hypothalamus and brainstem structures is the central amygdaloid nucleus, which also sends projections to the nucleus of the tractus solitarius, the dorsal motor nucleus of the vagus nerve, and the superior cervical segments of the spinal cord. Uncrossed fiber systems descending from the basal ganglia terminate at the level of the pons, whereas uncrossed and crossed fiber systems descending from the dorsal and ventromedial hypothalamus can be traced into the spinal cord. The possible role of nuclei of the amygdaloid group, the hypothalamus, and their efferent projections in the regulation of somatic and vegetative functions and also of complex behavioral reactions is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 1, pp. 14–23, January–February, 1981.     

Neural connections of the lizard septum investigated by HRP axonal transport techniques

Neuronal connections were investigated in the lizard (Ophisaurus apodus) by injecting horseradish peroxidase. Reciprocal connections were found between the septum and the dorsal and mediodorsal cortex, as well as projections from the diagonal bundle nucleus and the anterior dorsolateral and dorsomedial thalamic nuclei to the septum. The most clear-cut bilateral connections were observed between the septum and the preoptic region, the hypothalamic periventricular structures, and the lateral hypothalamic region (containing dopaminergic neurons) as well as nuclei of the mamillary body. Some characteristics and the overall organization pattern of connections between the septum and other limbic system structures are reviewed.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 3, pp. 398–407, May–June, 1988.     

Respiratory rhythm generation in rats: The importance of inhibition

Stimulation-related modifications of activity in the phrenic nerve and external and internal intercostal nerves were studied on urethane-anesthetized rats; the inspiratory medullary structures were stimulated. The activity was recorded either following microinjections of gamma-aminobutyric acid (GABA) or its derivatives into the medial parabrachial nuclei and rostral part of the ventral respiratory group of medullary neurons, or without such microinjections. Gradual dependence of activity in these nerves on the phase of the respiratory cycle was established. It was shown that the higher was the integrated inspiratory activity, the lower became the relative gain in phrenic nerve activity caused by standard stimulation. When stimulation was applied at the postinspiratory phase, the threshold stimulus intensity showed an S-like rise with an increase in integrated inspiratory activity. Microinjections of GABA or its cyclic derivatives into the parabrachial nuclear structures decreased the inhibitory effects of the latter. During the postinspiratory phase, the effect was opposite: an increase in the relative gain of inspiratory activity and drop in the threshold. The resulting data suggest that there is a two-level organization of the respiratory regulatory inhibition and that the whole respiratory neuronal network has a compartmental structure.Neirofiziologiya/Neurophysiology, Vol. 25, No. 6, pp. 420–426, November–December, 1993.     

NADPH-Diaphorase-containing neurons in the medullary structures involved in generation of the respiratory activity in neonatal rats

Using a histochemical technique, we examined distribution of the neurons containing a marker of nitric oxide synthase (NOS), NADPH-diaphorase (NADPH-d), on frontal slices of the medulla and upper cervical spinal segments of 4-day-old rats. It was demonstrated that NADPH-d-positive cells are present within the dorsal and ventral medullary respiratory groups. The highest density of the labeled middle-size multipolar neurons (27.9±2.6 cells per 0.1 mm² of the slice) was observed in the rostral part of the ventral respiratory group, within the reticular lateral paragigantocellular nucleus. Similar NADPH-d-positive neurons were also observed in other reticular formation structures: rostroventrolateral reticular, gigantocellular, and ventral medullary nuclei, and in the ventral part of the paramedial nucleus. There were no labeled neurons in the lateral reticular nucleus. Single small and medium-size labeled neurons were found at all rostro-caudal levels of thenucl. ambiguous (nuclei retrofacialis, ambiguous, andretroam-biguous). Groups of NADPH-d-positive neurons were also revealed within the dorsal respiratory group, along the whole length of thenucl. tractus solitarii (mostly in its ventrolateral parts). Single labeled neurons were also observed in thenucl. n. hypoglossi, and their groups were observed in the dorsal motor part of thenucl. n. vagus. Involvement of the structures containing NADPH-d-positive neurons in the processes related to generation of the respiratory activity is discussed. Our neuroanatomical experiments prove that in early postnatal mammals NO is actively involved in generation and regulation of the medullary respiratory rhythm. Neirofiziologiya/Neurophysiology, Vol. 32, No. 2, pp. 128–136, March–April, 2000.     

Maturation of thalamic inputs in neocortical association areas during postnatal development in cats

Formation of thalamofrontal and thalamoparietal connections in kittens during the first month of life was studied by the retrograde axonal transport of horseradish peroxidase method. In the early stages of postnatal development, association nuclei of the thalamus as well as its specific structures were shown to have cortical projections. Structural formation of the thalamo-parietal system also was shown to take place earlier than that of the thalamo-frontal system. The results indicate differences in location of cortical projections of the ventral lateral and ventral anterior thalamic nuclei and also a difference in the times at which their efferent fibers grow into the cerebral cortex.A. A. Ukhtomskii Physiological Institute, Leningrad State University. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 11–18, January–February, 1984.     

Effects of blockade of noradrenergic and serotonergic transmission in theCM-Pf complex on neuronal activity in the motor thalamus in cats

Effects of injections of blockers of the monoaminergic receptor structures into thecentrum medianum-nucl. parafascicularis (CM-Pf) on the activity of neurons in the motor thalamic nuclei (VA-VL) were studied in chronic experiments on awake cats. The animals were trained to perform an operant placing reflex by the forelimb. Injection of a-adrenoblocker, anapriline, into theCM-Pf resulted in enhancement of background activity of neurons of the motor thalamus and facilitation of their spike responses related to conditioned and unconditioned reflex movements. Application of a blocker of serotonin receptors, lysergoamide, evoked opposite changes in the neuronal activity in theVA-VL nuclei: depression of background activity, facilitation of inhibitory processes, and suppression of evoked activity related to conditioned and unconditioned movements. It is supposed that the monoaminergic system of thelocus coeruleus exerts a suppressing influence on the motor thalamus via theCM-Pf complex, while the system of the raphe nuclei facilitates motor thalamic structures.Neirofiziologiya/Neurophysiology, Vol. 28, No. 6, pp. 305–311, November–December, 1996.     

Morphometric parameters of neurons in reticular nuclei of the brain stem in kittens

Three types of Golgi-stained neurons were discovered in brain stem reticular nuclei of 30-day-old kittens: sparsely branching reticular neurons, those with densely branching dendritic trees, and giant multipolar neurons (Leontovich's classification). Adopting computerized morphometric techniques enabled 23 different parameters to be measured in cells of these types. The measurements taken from the neuronal groups investigated revealed statistically significant differences between them for most parameters. It was concluded from this that each of the neuronal types distinguished has its own morphological identity (or stability). Characteristics of structural differences and properties of differing cell types in reticular nuclei are discussed in relation to their functional properties.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 23, No. 4, pp. 399–409, July–August, 1991.     

Dynamics of potentials evoked in the auditory pathway and reticular formation of the cat. Studies during waking and sleep stages

Averaged evoked potentials in the inferior colliculus (IC), medial geniculate nucleus (MG) and reticular formation (RF) of chronically implanted and freely moving cats were measured using auditory step functions in the form of tone bursts of 2000 Hz. The most prominent components of the AEP of the inferior colliculus were a positive wave of 13 msec and a negative wave of 40–55 msec latency. The AEP of the medial geniculate nucleus was characterized by a large negative wave peaking at 35–40 msec. During spindle sleep and slow wave sleep stages changes in the AEPs of both nuclei occured.Transient evoked responses of the inferior colliculus, medial geniculate nucleus and reticular formation were transformed to the frequency domain using the Laplace transform (one sided Fourier transform) in order to obtain frequency characteristics of the systems under study. The amplitude characteristics of IC, MG. and RF obtained in this way revealed maxima in alpha (8–13 Hz), beta (18–35 Hz) and higher frequency (50–80 Hz) ranges. During spindle sleep stage a maximum in the theta frequency range (3–8 Hz) and during slow wave sleep maximum in the delta (1–3 Hz) frequency range appeared in the amplitude characteristics of these nuclei.The amplitude characteristics of the inferior colliculus and medial geniculate nucleus were compared with the amplitude characteristics of other brain structures. The comparison of AEPs and amplitude frequency characteristics obtained using these AEPs reveals that the existence of a number of peaks (waves) with different latencies in the time course does not necessarily indicate the existence of different functional structures or neural groups giving rise to these waves. The entire time course of evoked potentials and not the number and latencies of the waves, carries, the whole information concerning different activities and frequency selectivities of brain structures.Supported by Turkish Scientific and Technical Research Council Grant TAG-266.Presented in Part at the VIIIth International Congress of Electroencephalography and Clinical Neurophysiology in Marseilles, September 1–7, 1973.     

Effects of hypoxia on the respiratory activity generated by semi-isolated medullo-spinal preparations of early postnatal rats

The effects of short- and long-lasting (2-min-long and up to 30-min-long) hypoxia episodes on the inspiratory activity (IA) recorded from then. phrenicus were tested in experiments on superfusedin situ semi-isolated medullo-spinal preparations (SIMSP) of newborn (the lst day of life) and 4- to 5-day-old rats. Hypoxia was provided by superfusion of the preparations with low-O₂ solution. Short-lasting hypoxia evoked no significant modulation of the IA in preparations of newborn animals, while two-phase responses (an initial, up to 30 sec, increase in the frequency of inspiratory discharges, followed by their longer, up to 4 min, suppression) were observed in 4- to 5-day-old preparations. Long-lasting hypoxia suppressed activity in then. phrenicus of 1-day-old preparations, and this effect was replaced in five cases by the development of sporadic low-amplitude and short-lasting inspiratory discharges. These shortened discharges were qualified as gasps. The responses of 4- to 5-day-old SIMSP to long-lasting hypoxia episodes were more complex. An initial increase in the IA frequency lasted up to 30 sec, and in 4–6 min it was followed by complete suppression of the activity. In some of the SIMSP, permanent tonic activity appeared in then. phrenicus within the period of total absence of inspiratory discharges, which could be followed by generation of short low-amplitude gasping discharges. Against the background of gasping pattern, eupnoe-like discharges appeared in four preparations. Under control conditions, transerve section of the ventrolateral medullary regions (VLMR) at a middle level of then. hypoglossus root abolished respiratory activity in all studied SIMSP. Yet, in some of the SIMSP of both newborn and 4- to 5-day-old animals long-lasting hypoxia testing evoked weak tonic activity in then. phrenicus followed by the appearance of gasping discharges. After the transection of the VLMR at the caudal edge of then. hypoglossus root, long-lasting hypoxia evoked only weak tonic responses in some SIMSP of both age groups, and there were no phasic discharges in this case. The results of our experiments, first, show that the respiratory activity in newborn animals is more resistant to hypoxia than that in 4-to 5-day-old rats, and, second, they allow us to suppose that the gasp-generating medullary structures are localized in more caudal medullary regions. We discuss the questions of how the eupnoe-generating and gasp-generating medullary structures are formed in rats during their initial four to five postnatal days, and what specific features are typical of hypoxia-related respiratory responses in these animals.Neirofiziologiya/Neurophysiology, Vol. 28, No. 2/3, pp. 121–131, March–June, 1996.     

Depression of evoked potentials in rat thalamic ventro-basal complex and somatosensory cortex after reticular stimulation

Experiments on unanesthetized rats immobilized with D-tubocurarine showed that electrical stimulation (100/sec) of the central gray matter and the mesencephalic and medullary reticular formation considerably depressed potentials in the somatic thalamic relay nucleus and somatosensory cortex evoked by stimulation of the forelimb or medial lemniscus. The mean threshold values of the current used for electrical stimulation of these structures did not differ significantly and were 70 (20–100), 100 (20–120), and 120 (50–200) µA, respectively. On comparison of the amplitude-temporal characteristics of inhibition of evoked potentials during electrical stimulation of the above-mentioned structures by a current of twice the threshold strength, no significant differences were found. Immediately after the end of electrical stimulation the amplitude of the cortical evolved potential and the post-synaptic components of the thalamic evoked potential was 50–60% (P<0.01) below the control values. The duration of this depression varied from 0.5 to 1 sec. An increase in the intensity of electrical stimulation of brain-stem structures to between three and five times the threshold led to depression of the presynaptic component of the thalamic evoked potential also. Depression of the evoked potential as described above was found with various ratios between the intensities of conditioning and testing stimuli.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 467–475, September–October, 1976.     

Parasympathetic discharges evoked in the pelvic nerve by stimulation of various structures in the amygdala

Parasympathetic discharges evoked by application of single and paired stimuli to central, corticomedial, and basolateral nuclei of the amygdala were recorded from the pelvic nerve (PN) in anesthetized and immobilized cats. The discharges were found to include three main negative waves (I, II, and III waves, appearing with the latencies of 16.0–17.8, 74–87, and 171–184 msec, respectively). The first two waves were seen most regularly. Sometimes the I wave was preceded by a super-early negative component of a low amplitude appearing with a latency of 8.5–10.7 msec. The discharges evoked by stimulation of various nuclei of the amygdala did not significantly differ from each other in their thresholds, time courses, and amplitudes, which suggests a relatively diffuse distribution of parasympathetic efferent structures in the amygdala. It was shown, using paired stimuli, that a response to the second stimulus needed a long-lasting period (a few tens of milliseconds) to be restored. The origin of the components of the amygdalofugal parasympathetic discharges recorded from the PN, as well as the corresponding pathways they spread through, are discussed. In addition, the possible origin of the positive components of the PN discharges are considered.Neirofiziologiya/Neurophysiology, Vol. 26, No. 5, pp. 326–333, September–October, 1994.     

Age-Related Effect of Cells as Donors of Nuclei: On the Efficiency of the Development of Cloned Rabbit Embryos

We studied the capacity of the nuclei of rabbit fibroblasts taken from various developmental stages for reprogramming in the cytoplasm of mature aging enucleated oocytes and the development of the cloned embryos to the preimplantation stages. A negative correlation was found between the age of an animal donor of fibroblasts and the efficiency of the development of cloned embryos (r _{morula-blastocyst}= –0.826, r _blastocyst= –0.7139). A reliably decreased capacity for reprogramming of the nuclei of donor fibroblasts was shown upon the transition from prenatal development to postnatal development, as well as a trend to a decreased capacity of nuclei for reprogramming during aging. The aging of cells in the culture, at least until the tenth passage, did not affect the capacity of the nuclei of fetal fibroblasts for reprogramming and the development of cloned embryos.     

Developmental potencies of nuclei from cleavage,preblastoderm, and syncytial blastoderm transplanted into unfertilized eggs ofDrosophila melanogaster

Summary Wild-type nuclei from eggs ofDrosophila melanogaster at various developmental stages and from different regions of the egg—cleavage nuclei, pole nuclei from preblastoderm, and lateral nuclei from syncytial blastoderm—were singly implanted into unfertilizedy w sn ³ lz _50e eggs to determine their developmental potencies.All three types of transplanted nuclei were almost equally effective in initiating development of unfertilized eggs. Development was arrested in one of five critieal embryonic stages or in one of the three larval instars. The frequency of individuals reaching a distinct stage was approximately the same for all three types of donor nuclei. The stage-specific pattern of defects was independent of the type of nucleus transplanted.The deviations from normal development were broadly similar to those seen in controls developing from fertilized eggs which had only been punctured or into which cytoplasm had been injected. Many defective embryos also occurred in these control experiments. These and other observations indicate that a large proportion of irregularly developed individuals found after nuclear transfer can be ascribed to loss of egg material, disturbances in the internal organization of the egg during nuclear implantation, and the difficulty the implanted nucleus has in adjusting to the autonomous processes within the egg, such as the formation and migration of cytoplasmic islands.Some of the defective embryos and larvae originating from nuclear transfer were implanted into adult hosts. After culture for 14 days the early embryonic stages had formed several larval structures, and the late embryonic and larval stages had developed all larval organs. The proliferated imaginal primordia of thesein vivo cultured embryos and larvae, as well as the imaginal disks of the third instar larva, were then implanted into larval hosts with which they passed through metamorphosis and differentiated into imaginal structures. All three types of donor nuclei were capable of producing all adult structures derivedin situ from imaginal disks. The phenotype of these structures waswild-type, thus demonstrating their origin from the transplanted nuclei.The problem as to why not all transplanted nuclei initiated development, and why development after nuclear transplantation was arrested at the third larval instar, at the latest, is discussed.This article is dedicated to Professor Friedrich Seidel on the occasion of his 75th birthday.     

Effects of Copper on Root Growth, Cell Division, and Nucleolus of Zea Mays

The effects of different concentrations (10^–5 – 10^–2 M) of copper sulfate on root growth, cell division and nucleoli in root tip cells of Zea mays L. were investigated. 10^–5 M Cu stimulated root growth, but at higher concentrations (10^–4 – 10^–2 M) inhibited it. Cu had toxic effects on chromosomal morphology: c-mitosis, anaphase bridges, and chromosome stickiness were induced. Some nuclei had irregular shape and particles extruded from nucleoli to nuclei and finally from the nuclei into the cytoplasm.     

Antidromic and synaptic potentials evoked in neurons of the lateral vestibular nucleus by stimulation of the interstitial nucleus of Cajal and Darkshevich's nucleus in cats

Effects of stimulation of the interstitial nucleus of Cajal and Darkshevich's nucleus on unit activity in the lateral vestibular nucleus of Dieters were investigated in cats anesthetized with pentobarbital. Stimulation of the above-mentioned structures was shown to lead to antidromic and orthodromic activation of Dieters neurons. Axon collateral of vestibular neurons, ascending to the above-mentioned brain-stem structures were discovered electrophysiologically. Stimulation of the nuclei of Cajal and Darkshevich was shown to evoke mono- and polysynaptic EPSPs and IPSPs in neurons of Deiters nucleus. Convergence of influences from both nuclei on the neurons studied was demonstrated. The particular features and functional role of the influences observed are discussed.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 822–829, November–December, 1984.     

Distribution and quantitative characterization of NADPH-diaphorase-reactive neurons in analgesic zones of the rat midbrain

The distribution of nitric oxide synthase (nicotinamide adenine dinucleotide phosphate diaphorase, NADPH-d)-containing neurons in the rat midbrain was studied. We found that NADPH-d-reactive neurons were predominantly concentrated in the dorsolateral part of the periaqueductal gray (PAG) and the dorsal raphe nucleus, which are implicated in the control of nociceptive transmission. Such neurons were also present in the supraoculomotor cap and laterodorsal tegmental nuclei. In the dorsolateral part ofPAG, the moderately stained small fusiform cells were revealed. In the dorsal raphe nucleus and laterodorsal tegmental nuclei, the densely stained multipolar or oval cells of larger size dominanted. The NADPH-d-reactive cells were not found in the ventrolateral part of central gray, which is considered the main source of antinociceptive descending influences. Quantitative analysis of histochemically revealed neurons showed that their number is somewhat higher in the caudal parts of dorsolateral central gray and considerably higher in the rostral regions of some dorsal raphe subnuclei. This peculiarity was expressed in significant accumulation of the NADPH-d-reactive neurons at the midbrain levels from Fr –7.6 to –8.0. The possible involvement of the NO-synthase-containing class of neurons in the functional organization of analgesic zones and formation ofPAG antinociceptive output signals is discussed.Neirofiziologiya/Neurophysiology, Vol. 28, No. 1, pp. 36–46, January–February, 1996.     

Presynaptic chromosome behavior in Lilium

The orientation and movement of chromosomes throughout premeiotic interphase in Lilium speciosum has been studied through three-dimensional reconstruction of electron micrographs of serial thin sections through microsporocyte nuclei. Anthers were chosen based upon the correlation between their length and the stage of the microsporocytes within, and were fixed for light and electron microscopy. A light microscopic survey of both squash preparations and thick sections was done to select the material for electron microscopic analysis. Microsporocytes from the selected anthers were serially sectioned (200–300 consecutive gold sections), stained for electron microscopy, and alternate sections of entire nuclei were photographed. Prints were traced, and these tracings were compiled to produce a composite of each nucleus in which the locations of the centromeres were indicated. The position of the centromeric structures (CeS) in each nucleus was characterized by the average distance between CeSs, the average distance between CeSs and the nuclear envelope, and the coefficients of variation of these distances. A test was made to determine if CeSs were positioned evenly throughout the nucleus. — The results indicate that centromeres do not exhibit extensive movement during PMI in Lilium speciosum cv. Rosemede and that homologous chromosomes do not undergo a prealignment during PMI which facilitates their pairing during later meiotic stages. A model of centromere movement in the interphase nucleus is proposed.     

Intertidal territoriality and time-budget of the surgeonfish, Acanthurus lineatus, in American Samoa

Synopsis The herbivorous surgeonfish Acanthurus lineatus aggressively maintained feeding territories in the surf zone of the outer reef flat in American Samoa. Intertidal territories were re-established each morning, as well as after displacement by low tides or rough surf. Day-to-day site fidelity of recognizable individuals was high: 99.9% return rate per day for adults (15–20 cm), 99.6% for juveniles (8–13 cm), and 97.2% for recruits (2.5–5 cm). Fish fed on turf algae primarily in the afternoon (80% of available time), and spent 10% of their time on active territorial defense and 2–13% of their time on forays from their territory. On average, a fish defended its territory 1900 times daily and took 17 000 bites (= 7400 bites m^–2 d^–1), but rough surf reduced feeding by 60% and defense by 75%. High territorial defense requirements significantly reduced feeding rates. Although the distribution and behavior of this species in Samoa was in large part similar to that reported for it elsewhere (Australia, Indian Ocean), there were notable differences: in Samoa A. lineatus densities within colonies were greater (0.4 fish m^–2), territory size was smaller (2.3 m²), and defense rate against intruders was greater (2.5 attacks min^–1). These differences in Samoa may be related to their smaller body size, greater abundance or increased food supply caused by hurricane damage to reefs which has enhanced the algal turfs that A. lineatus feeds upon.