SHIPBOARD LINE TRANSECT SURVEYS OF CRABEATER SEAL ABUNDANCE IN THE PACK-ICE OFF EAST ANTARCTICA: EVALUATION OF ASSUMPTIONS

We examine the extent to which the assumptions underlying line transect sampling are satisfied in shipboard surveys of crabeater seals ( Lobodon carcinophaga ) hauled out on the Antarctic pack-ice. Measurement of the perpendicular distance of seal groups from the ship with an electronic inclinometer fitted to a rifle stock was unbiased. Crabeater seals showed little movement in response to the approaching ship. Movement away from the ship by seals close to the ship's track was partially responsible for a relative lack of sightings close to the transect-line, but otherwise had little effect on the sighting histogram. Minor deviations from the transect direction to avoid running over seals violated the assumption of uniform distribution of groups, and contributed to a relative lack in sightings close to (<40 m) the transect-line. We estimate that 5%-10% of seal groups close to the transect-line were not sighted by bridge observers prior to passing abeam of the ship, but most of these missed groups were likely to have been sighted some distance behind-abeam. Shipboard transects provided a biased sample of four environmental features known to be related to crabeater seal abundance because of logistical difficulties in the ship traversing along straight transects through thick ice. Calculation of transect length L from successive GPS locations was mildly sensitive to the frequency of locations. We provide analytical recommendations to reduce or eliminate the effect of assumption violation when present and hence minimize bias in abundance estimation.     

Biphasic calcium response of platelet-derived growth factor stimulated glioblastoma cells is a function of cell confluence.

BACKGROUND: Previous reports have linked the spiking or two-phased character of calcium transients evoked by platelet-derived growth factor (PDGF) to the position of cells in the cell cycle without regard to cell-cell contact and communication. Because cell confluence can regulate growth factor receptor expression and dephosphorylation, we investigated the effect of cell culture confluence and cell cycle on calcium responses of PDGF-BB-stimulated A172 glioblastoma cells. METHODS: Digital imaging cytometry was used to correlate the peak and duration of calcium response with bromodeoxyuridine positivity and DNA content and with culture confluence on a cell-by-cell basis. RESULTS: In serum-starved cultures, complete two-phase calcium signals and shorter, lower spikes occurred independent of cell cycle phase. However, the confluence of cell culture seemed essential for inducing a complete response because cells in sparse cultures exhibited mostly short spikes with lower peaks or no transients at all. CONCLUSION: Because cell confluence, by virtue of cell-cell contacts, is assumed to be an important regulator of proliferation, one is tempted to speculate that in transformed cells the ability to produce stronger growth signals upon reaching confluence and facing contact inhibition could provide a proliferative advantage.     

The use of time and space by male and female gerbils exploiting a pulsed resource

Foraging theory postulates that interference is a foraging cost and affects patch exploitation and activity times. One such system contains two species of seed-eating gerbils inhabiting sandy habitats in the Negev Desert of Israel. Low population densities of the dominant species allowed us to examine the interaction between males and females of the subordinate species, Gerbillus andersoni allenbyi , as a function of interference and resource renewal. We used giving-up densities (GUDs; the amount of food left in a resource patch when a forager abandons the patch) in seed trays to quantify patch use by gerbils. By placing 6 trays at each foraging station and either presenting all 6 trays at the start of the night (pulse treatment) or presenting one tray at a station 6 times per night (renewal treatment), we were able to manipulate characteristics of resource renewal. We used radio telemetry to obtain an independent assessment of activity. Male and female G. a. allenbyi differed in their timing of activity, with males beginning earlier than females and remaining active later. This was most pronounced for the pulse treatment. For the renewal treatment, female activity in trays was more intense early in the night, but thereafter male activity was more intense. At the same time, telemetry showed that males and females did not differ in their total activity in or out of trays. This suggests that males begin their activity on the renewal treatment by exploiting the richest natural patches of seeds. Only later when these are depleted do they move to dominate the renewing seed trays. Finally, females exploited stabilized sand habitats more than did males, especially during the renewal treatment. Taken together, these findings suggest that male G. a. allenbyi interfere with foraging in females, causing temporal shifts in their use of space and resources.     

The site of action of pyrethrin I in the nervous system of the cockroach Periplaneta americana

Spontaneous nervous activity in the sixth abdominal ganglia of the cockroach is increased by much smaller concentrations of pyrethrin I than are needed to affect conduction in giant fibre axons, suggesting that the fatal lesions caused by pyrethrin I may be within the ganglia rather than associated with axonic conduction.Pyrethrin I is about 30 times more active than allethrin (Narahashi, 1962, a & b) against conduction in giant fibres.

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Zusammenfassung Neurophysiologische Methoden wurden angewendet, um die Wirkung von Pyrethrin I auf die Leitung von Aktionspotentialen in Riesenfasern und den Umfang der Spontanaktivität im 6. Abdominalganglion erwachsener männlicher Küchenschaben festzustellen. In Versuchen an isolierten Nervenpräparaten hatten Pyrethrin I-Konzentrationen von weniger als 10^-7 M wenig Wirkung auf die Riesenfasern, während so geringe Konzentrationen wie 10^-10 M im Ganglion die Höhe der Aktivität beeinflußten. Riesenfasern von Küchenschaben, die vorher örtlich mit DL95s von Pyrethrin I behandelt worden waren, wurden 1–4 Stunden nach der Vergiftung stark beeinflußt, wenn die Insekten stark angegriffen waren, doch war die Aktivität im 6. Abdominalganglion zu diesem Zeitpunkt stark erhöht. Einige intraganglionäre Neurone sind also gegenüber der Vergiftung mit Pyrethrinen wesentlich empfindlicher als die Riesenfasern, was darauf hindeutet, daß die gefährlichen Schädigungen durch Pyrethrine wahrscheinlich eher innerhalb der Ganglien als in peripheren Nerven auftreten.Die Wirkung von Pyrethrin I an Riesenfasern ähnelt den von Narahashi (1962 a+b) für Allethrin beschriebenen, doch war Pyrethrin I etwa 30mal aktiver.

     

The spread of topically-applied pyrethrin I from the cuticle to the central nervous system of the cockroach Periplaneta americana

Penetration of topically-applied pyrethrin I into adult male American cockroaches (Periplaneta americana L.) and its subsequent distribution within the insects was studied microchemically and biologically. After applying an LD95 (0.5 g per insect), pyrethrin I was lost from the surface of the insects at a rate diminishing with time; 20% of the dose applied penetrated during the first hour, but elimination limited the amount found inside the insects to a maximum of 13%. The amount inside the insects increased for an hour after dosing, when symptoms of poisoning had become severe, but then remained steady until the end of the test, 48 hrs after dosing.Pyrethrin I sorbs strongly but reversibly on insect solids from aqueous solution, and at equilibrium is distributed between solids and solution in the ratio 3 × 10⁴: 1. This ratio would give a concentration of only 4 × 10^–11 M of pyrethrin I in the haemolymph of insects poisoned with an LD95 of the insecticide, but solids in the haemolymph would increase its pyrethrin I content and speed the spread of the insecticide from cuticle to nervous system. Chemical tests able to detect pyrethrin I at concentrations of 2×10^–8 M failed to show its presence in the haemolymph of poisoned cockroaches, but the haemolymph caused symptoms resembling those of pyrethroid poisoning when applied to nerve preparations from normal cockroaches.Although pyrethrin I at 4 × 10^–11 M in the haemolymph of cockroaches treated topically with LD95s of the insecticide seems too dilute to have produced the symptoms observed in their nervous systems, the results of additional tests did not support the alternative suggestion that the insecticide reached the nervous system by spreading over the cuticle and through the tracheal system. Larger concentrations of pyrethrin I occurring locally in the haemolymph near the nervous system during the early stages of poisoning may explain the anomaly.

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Résumé La pénétration d'une application topique de pyrethrine I chez le mâle adulte de Periplaneta americana et sa distribution ultérieure dans l'organisme est étudiée microchimiquement et biologiquement. Après application d'une dose égale à la DL 95 (0,5 g par insecte), la pyrethrine I est absorbée à la surface de l'insecte à un taux décroissant avec le temps; 20% de la dose appliquée pénètre durant la 1ère heure, mais l'élimination limite la quantité trouvée dans l'organisme à un maximum de 13%. La quantité trouvée dans l'organisme s'accroît pendant la 1ère heure après l'intoxication, quand les symptômes de l'intoxication deviennent importants, puis reste stationnaire jusqu'à la fin du test, soit 48 heures après l'intoxication.La pyrethrine I s'absorbe fortement mais réversiblement sur la phase solide de l'insecte, à partir de la solution aqueuse et le coefficient de partition est de 3×10⁴: 1. Ce coefficient donnarait une concentration de pyrethrine I de seulement 4 × 10^–11 M dans l'hémolymphe des insectes intoxiqués à la DL 95, mais la phase solide de l'hémolymphe augmenterait sa teneur en pyrethrine I et accélérerait la vitesse de pénétration de l'insecticide, de la cuticule vers le système nerveux. Des tests chimiques capables de déceler la pyrethrine I à la concentration de 2×10^–8 M n'ont pu établir sa présence dans l'hémolymphe des blattes intoxiquées, mais cette hémolymphe provoque des symptômes analogues à ceux de l'intoxication par les pyrethrines, quand elle est appliquée à des préparations nerveuses de blattes nonintoxiquées.Quoique la pyrethrine I à la concentration de 4 × 10^–11 M dans l'hémolymphe de blattes traitées localement à la DL 95 de cet insecticide, semble trop diluée pour produire les symptômes observés dans le système nerveux, des résultats supplémentaires n'ont pas autorisé une autre hypothèse, à savoir que l'insecticide atteindrait le système nerveux via la cuticule et le système trachéen. Des concentrations plus fortes de pyrethrine I, localisées près du système nerveux pendant les premiers stades de l'intoxication pourraient expliquer cette anomalie.

     

The influence of penetration, distribution, sorption and decomposition on the poisoning of the cockroach Periplaneta americana treated topically with diazoxon

Microchemical techniques were used to assess the rate of penetration of diazoxon into the American cockroach Periplaneta americana L. by measuring loss from the surface of the cuticle after topical application. By similar methods the proportions of the amount entering which were decomposed, absorbed by the tissues, or circulating in the haemolymph were also estimated. About three-quarters of an LD₉₀ of diazoxon (2.6 g) applied to the metathoracic sternum of adult male cockroaches had penetrated the cuticle 2 hr after treatment. The maximum concentration within the cockroach, reached about 1 hour after treatment, was 2.4 M, but two-fifths of this is sorbed on solids, leaving 1.4 M in the total body fluids. The maximum concentration in the haemolymph occurred 1 1/2 hr. after treatment and ranged from 0.9 to 3.4 M, with a median value of 1.8 M. The close relationship between concentration in haemolymph and in total body fluids suggests that they are in approximate equilibrium.An independent estimate of the concentration of diazoxon in the haemolymph of cockroaches treated with an LD₉₀ of the insecticide, made by means of an electrophysiological technique, agreed well with the values obtained from the chemical assay. The maximum concentrations (0.6–1.0 M) was found 1–2 hr. after treatment, when irreversible damage to the nervous system first occurred.The close agreement between the chemical and biological estimates suggests that diazoxon invades the nerve cord from the haemolymph, and that it acts directly, rather than as a metabolite or by the release of a neuroactive material.

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Zusammenfassung Um die Eindringgeschwindigkeit von Diazoxon in die Amerikanische Küchenschabe Periplaneta americana festzustellen, wurden mikrochemische Verfahren benutzt, indem nach örtlicher Aufbringung das Verschwinden von der Oberfläche der Kutikula gemessen wurde. Mit ähnlichen Methoden wurden auch die Anteile der eingedrungenen Menge abgeschätzt, die abgebaut oder von den Geweben absorbiert wurden oder in der Haemolymphe zirkulieren. Das Eindringen von Diazoxon, das auf dem Sternum des Metathorax erwachsener Küchenschaben-Männchen aufgetragen wurde, ist der vergangenen Zeit proportional, und über 3/4 einer LD₉₀ (2,6 g) ist nach 2 Stunden eingedrungen. Die Menge im Insekt wächst eine Stunde nach der Applikation auf etwa 1/5 der angewendeten Dosis und nimmt nach 2 Stunden auf etwa 1/12 ab. Etwa 2/5 der eingedrungenen Menge wird an ungelöste Stoffe gebunden, und in Anbetracht dessen wurde für die maximal erreichte Konzentration in der gesamten Körperflüssigkeit 1,4 M berechnet, was etwa 1/8 der angewandten Dosis entspricht. Die Zeit-Konzentrations-Kurve des Diazoxons in der Haemolymphe einzelner Küchenschaben, die mit einer LD₉₀ behandelt worden waren, hatte einen ähnlichen Verlauf wie die für das gesamte Diazoxon; die Konzentration erreichte ein Maximum 1 1/2 Stunden nach der Behandlung, wobei es von 0,9 bis 3,4 M mit einem Median wert von 1,8 M schwankte. Die enge Beziehung zwischen der Konzentration in der Haemolymphe und in der gesamten Körperflüssigkeit machte es wahrscheinlich, daß sie annähernd im Gleichgewicht miteinander stehen.Bei der Bespülung von Küchenschaben-Ganglien in vitro mit einer Reihe von Diazoxon-Konzentrationen in Kochsalzlösung unter Beobachtung der Vergiftungssymptome in den Metathorax-Ganglien mit elektrophysiologischen Methoden wurde eine Kurve aufgestellt über die Beziehungen der Diazoxon-Konzentration zu der Zeit, die erforderlich ist, um irreversible Schäden der Nervenfunktion hervorzurufen. Unter Anwendung der gleichen Methoden bei der Beobachtung des Verhaltens der Ganglien in Küchenschaben, die zu bekannter Zeit vorher mit LD₉₀s von Diazoxon örtlich behandelt worden waren, konnte von der Kurve die Diazoxon-Konzentration in der Haemolymphe abgeschätzt werden, wann die Ganglien irreversibel geschädigt wurden. Irreversible Schädigung trat erst 1–2 Stunden nach der Anwendung mit einer LD₉₀ auf, und die Konzentration, die zur Erzeugung des gleichen Vergiftungsstadiums in freigelegten Ganglien in vitro in der gleichen Zeit erforderlich war (0,6–1,0 M), ähnelt eher der mittleren Konzentration (1,8 M), die durch chemische Prüfung in der Haemolymphe ähnlich behandelter Schaben gefunden wurde. Daraus folgt, daß Diazoxon von der Haemolymphe aus in die Ganglien eindringt, und daß es eher direkt wirkt statt als Umwandlungsprodukt oder durch die Entbindung eines neuroaktiven Stoffes.

     

蓖麻蚕卵受精的研究

我们从细胞形态上的研究, 证明:蓖麻蚕卵在成熟期分裂的中期(同一横剖面), 基组数染色体是14;分作两圈, 内层4个, 外层10个。成熟卵停止在第一次中期分裂, 纺锤体与卵膜垂直, 待精子入卵后继续向前分裂, 并发现有染色质消散的现象。第二次成熟期分裂结果获得3个极体和1个雌性原核。正常的卵平均能接受2-3条精子, 它们入卵后起收缩、囊化成雄性原核;其中一个与雌性原核合并为“双组核”。剩余的过数精核分裂缓慢, 终于中心体离纺锤体作异形的分裂。     

At‐vessel mortality of skates (Rajidae) taken in coastal fisheries and evidence of longer‐term survival

Data on the vigour and at‐vessel mortality (AVM) of 6798 skates (comprising Raja clavata n = 6295; R. brachyura n = 208; R. undulata n = 185, R. montagui n = 98 and R. microocellata n = 12) captured by commercial fishing vessels in the inshore waters of the southern North Sea and English Channel were recorded. AVM in longline fisheries averaged 0·44% across five vessels (0–1·47%), although skates were usually unhooked manually and did not usually pass through a bait‐stripper. AVM in otter trawls averaged 0·76% (0–2·35%), from four vessels fishing with tow durations of <1·5 h (southern North Sea) or 1–4 h (English Channel). No AVM was noted for skates taken as a by‐catch in drift trammel nets (soak times <4 h). Anchored tangle nets resulted in an overall AVM of 2·0–2·7%, but increased from 1·47% (13–28 h soak time) to 6·16% (42–53 h soak time). There were significant differences in the vigour of skates between gears, with R. clavata caught by longline and tangle nets in better condition than those captured by otter trawl or drift trammel net. Similarly, R. undulata caught by tangle net were in better condition than those caught by otter trawl. The vigour of R. undulata was also found to be higher than other skate species for both trawl and tangle net. In total, 5283 skates were tagged with Petersen discs and released, with recapture rates for the various combinations of vessel and gear ranging up to 24·8% for R. clavata. Whilst confirming a degree of post‐release survival, quantitative estimates of post‐release mortality for skates remain unknown.