THE COURTSHIP OF EUGLANDINA ROSEA FERUSSAC

Courtship of Euglandina rosea commences with trail followingculminating in the pursuing snail mounting the shell of thepursued from the rear. A vigorous head waving display then occursand is terminated after about 15 min by a short quiescent periodduring which the lower animal turns its head to face its ownshell. Copulation takes place whilst one snail is still mountedon the shell of the other, but in a head to head position broughtabout by the twisting of the neck of the lower animal. It lastsup to four hours. (Received 24 April 1984;     

FACTORS AFFECTING TRANSMISSION AND RECOVERY IN THE PASSIVE IRON NERVE MODEL

1. The speed of transmission of the activation wave along passive iron wires enclosed in glass tubes containing dilute (70 per cent) nitric acid increases with the conductivity (sectional area) of the column of electrolyte but at a slower rate. The speed is closely proportional to the square root of the conductivity See PDF for Equation. The reasons for this relationship are discussed and an explanation is proposed. 2. The recovery of transmissivity after the passage of an activation wave is gradual and follows a characteristic course. After an interval of partial or decremental transmission (having a high temperature coefficient and lasting several minutes at 20°), the wire recovers its power of transmitting an activation wave for an indefinite distance. In such a recovered wire the speed of transmission is at first slow and increases by degrees up to a maximum, the increase following a curve apparently of the type v_t = v ₀ (1 – e^_kt). The approximate time required to attain this maximum (corresponding to complete recovery) at the different temperatures is 15 to 20 minutes at 20°, 30 to 45 minutes at 15°, ca. 60 minutes at 10°, and 90 minutes or more at 5°. 3. The character of the curve of recovery (the curve relating speed of transmission to interval since previous activation) agrees with the assumption that the increase in speed depends on a progressive chemical change in the molecules forming the passivating film, this change involving the transformation of (relatively) nonreactive into reactive molecules and following the course of a monomolecular reaction. 4. The temperature coefficient of the speed of transmission (between 5° and 20°) is low, of the order Q ₁₀ = 1.3 to 1.6. That of the rate of recovery, on the contrary, is high (Q ₁₀ = ca. 3). The parallel to the conditions in nerve and other transmitting protoplasmic systems is pointed out and discussed. 5. Passive wires enclosed in acid-containing continuous and interrupted glass tubes immersed in a large volume of acid exhibit characteristic phenomena of distance action; under appropriate conditions the velocity of transmission of the activating influence between different areas may thus be greatly increased. Characteristic instances are cited and some possible physiological parallels are pointed out.     

PREY SPECIFICITY AND FEEDING OF THE THECATE MIXOTROPHIC DINOFLAGELLATE FRAGILIDIUM DUPLOCAMPANAEFORME1

In summer to autumn of 2008, a recently described thecate mixotrophic dinoflagellate, Fragilidium duplocampanaeforme Nézan et Chomérat, occurred in Masan Bay, Korea, where it frequently contained bright‐orange fluorescent inclusions. Using cultures of F. duplocampanaeforme isolated from Masan Bay, we investigated feeding, digestion, and prey specificity of this mixotroph. F. duplocampanaeforme fed exclusively on Dinophysis spp. when offered a variety of prey including dinoflagellates, a raphidophyte, a cryptophyte, a ciliate, and diatoms separately. In addition, F. duplocampanaeforme had allelopathic effects on other organisms, including cell immobilization/motility decrease (in Dinophysis acuminata, D. caudata, D. fortii, D. infundibulus, Gonyaulax polygramma, Heterocapsa triquetra, and Prorocentrum triestinum), breaking of cell chains (in Cochlodinium polykrikoides), cell death (in Prorocentrum minimum), and temporary cyst formation (in Scrippsiella trochoidea). F. duplocampanaeforme engulfed whole Dinophysis cells through the sulcus. About 1 h after ingestion, F. duplocampanaeforme became immobile and shed all thecal plates. The ecdysal cyst persisted for ～7 h, during which the ingested prey was gradually digested. These observations suggest that F. duplocampanaeforme may play an important role in the Dinophysis population dynamics in the field.     

FACTORS AFFECTING THE TURNOVER OF CEREBRAL GLYCOGEN AND LIMIT DEXTRIN IN VIVO

The turnover of cerebral glycogen in mice has been investigated by using [U-¹⁴C]glucose as a precursor. The time required for turnover of total glycogen and limit dextrin has been determined in normal animals and animals given phenobarbital or hydrocortisone. In all 3 groups, the turnover time for limit dextrin was twice that of total glycogen. Phenobarbital increased the time for turnover of total glycogen and limit dextrin approximately 2-fold, whereas hydrocortisone diminished the turnover time of both fractions to one-half. The accumulation of glycogen during phenobarbital anesthesia (2·5-fold) is attributed to the decrease in rate of phosphorolysis rather than elevated glycogenesis. The ratio of phosphorylase a to total phosphorylase was significantly decreased in the brains of phenobarbital-treated mice, while the ratio of glycogen synthetase I to total synthetase activity was not affected. The administration of hydrocortisone had no effect on either the phosphorylase or synthetase of mouse brain. A mathematical model was devised to determine the rate constants for incorporation of labelled glucose into brain glycogen and the subsequent loss of radioactivity. Metabolite levels and enzyme activities have been correlated with the observed changes in glycogen turnover.     

THE EVOLUTION OF TETRAPOD FEEDING BEHAVIOR: KINEMATIC HOMOLOGIES IN PREY TRANSPORT

One of the major features of the aquatic-to-terrestrial transition in vertebrate evolution was the change in the mechanism used to transport prey from the jaws to the throat. Primarily, vertebrates use hydraulic transport, but the transition to terrestrial life was accompanied by modifications of the hyobranchial apparatus that permit tongue-based transport. Despite an extensive data base on amniote feeding systems and mechanisms of intraoral prey transport, few data are available on the mechanism of prey transport in anamniote tetrapods. Transport cycles of four Ambystoma tigrinum (Amphibia) feeding on worms and crickets were filmed at 150 flames per second to produce quantitative profiles of the intraoral transport cycles for the two prey types. During the transport cycle the head and body remain stationary relative to the background: transport in Ambystoma tigrinum thus does not involve inertial movements of the head or body. Prey type had little effect on the kinematics of prey transport. The process of prey transport may be divided into four phases: preparatory, fast opening, closing, and recovery. The preparatory phase itself is divided into two parts: an extended segment that may include slight slow opening and a static phase prior to mouth opening where no change in gape occurs. The kinematic profile of transport in terrestrial salamanders is extremely similar to that used by fishes during hydraulic (aquatic) prey transport. We hypothesize that the distinct recovery and preparatory phases in the transport cycle of anamniote tetrapods are together homologous to the slow opening phases of the amniote cycle, and that during the evolution of terrestrial prey processing systems the primitive extended preparatory phase has become greatly compressed and incorporated into the amniote gape cycle.     

HUMAN ACTIVITIES AND FACTORS AFFECTING THE DISTRIBUTION OF MACROBENTHIC FAUNA IN SALDANHA BAY

Summary

The most recent trends in the economic development of Saldanha Bay are towards the tourist and mariculture industries, both of which are dependent on a high quality of water. Yet this water quality is now under threat. In this study, the extent of human induced changes to the characteristics of the water body are assessed in terms of their effects on the macrobenthic communities of the bay. Such effects are evaluated on the basis of changes in biomass, community structure and species composition using data from recent surveys as well as a limited quantity of historical data.

Whilst gross effects are essentially confined to an area adjacent to the major fish factory outfall, the data do suggest a broader impact. There are substantial differences between the communities of ‘Big Bay’ and ‘Small Bay’, with an apparent increase in deposit feeding species and decline in suspension feeders in the latter. These changes are attributed to the organic loading from the fish factories and mariculture industries together with restrictions imposed on water circulation by harbour constructions. This combination of anthropogenic factors may be leading to significant enrichment of certain areas of the bay.     

FACTORS AFFECTING THE SECRETION OF LUTEINIZING HORMONE IN THE EWE

(1) Luteinizing hormone (LH) is secreted as discrete pulses throughout all stages of the reproductive cycle of the ewe, including pre-pubertal, seasonal and lactational anoestrus, and the luteal and follicular phases of the oestrous cycle. Secretion is probably also pulsatile during the preovulatory surge of LH. (2) The secretion of LH is affected by the ovarian steroids, oestradiol and progesterone, both of which act principally to reduce the frequency of the pulses. During the luteal phase the two steroids act synergistically to exert this effect, and during anoestrus oestradiol acts independently of progesterone. Androstenedione secreted by the ovary apparently has no role in the control of LH secretion. (3) The amplitude of the pulses may also be affected by the steroids but there are conflicting reports on these effects, some showing that amplitude is lowered by the presence of oestrogen and others showing increases in amplitude in the presence of oestrogen and progesterone. (4) The secretion of LH pulses is affected by photoperiod, social environment and nutrition. Under the influence of decreasing day-length, oestradiol alone cannot reduce the frequency of pulses and the ewe experiences oestrous cycles. When day-length is increasing, the hypothalamus becomes more responsive to oestradiol which reduces the frequency of the pulses. (5) A hypothetical pheromone secreted by rams can increase the frequency of the LH pulses in anoestrous ewes and thereby induce ovulation, possibly by inhibiting the negative feedback exerted by oestradiol. (6) The relationships between nutrition and reproduction are poorly understood, but it seems likely that the effects of nutrition are mediated partly through the hypothalamus and its control of the secretion of LH pulses. (7) The pulses of LH secreted by the anterior pituitary gland are evoked by pulses of GnRH secreted by the hypothalamus. The location of the centre controlling the GnRH pulses and the neurotransmitter involved are not known.     

粟长蠕孢菌的异核现象及异核体核型比影响因素的研究

本试验通过23株带有遗传标记的粟长蠕孢菌突变菌株,获得生理性状及生长势不同于亲本的异核体。利用营养缺陷型标记菌株研究的结果表明,粟长蠕孢菌异核体的形成及核型成分的变化受选择压力的影响。原生质体检测结果表明,在异核菌丝体中,异核细胞占46.7%,同核细胞占53.3%。分生孢子检测结果表明,只有0.06%的分生孢子保持异核状态。     

PREY CAPTURE AND FACTORS CONTROLLING TRAP NARROWING IN DIONAEA (DROSERACEAE)

Traps of Dionaea which have captured prey by a rapid closure mechanism continue to close with the lobes of the trap assuming a tightly appressed condition called the narrowed phase. Traps fed ants, which make up about one-third of the prey captured in the field, assumed the narrowed condition within about 7 h of feeding. Ants were alive and capable of delivering mechanical stimulation to the trigger hairs until about 8 h after feeding when they were apparently killed by acid fluid (pH 2–3) secreted by the trap at that time. That stimulation of trigger hairs delivered by the insect during this period is sufficient to cause both the narrowing and acid secretion was demonstrated by laboratory experiments in which both of these responses were initiated within 5 h by stroking the trigger hairs with clean, dry nylon bristles. Such purely mechanical stimuli, delivered to the trigger hairs, produced action potentials in the trap throughout the period of stimulation. Chemicals such as Na⁺, NH₄⁺, urea, and amino acids were capable of producing the narrowing response within one or two days. There was a 50% response to NaCl and NH₄Cl solutions of about 6 mM and a 90% response to 34 mm solutions. Urea, L-lysine, and glycine produce a significant response at 50 mm but can cause necrosis of the trap tissue at concentrations above 50 mm . Salt-free ovalbumen (0.5 and 5.0 g/l) and KCl, CaCl₂, and D-glucose were ineffective in initiating the narrowing response. The level of Na⁺, NH₄⁺, and amino acids necessary to elicit the narrowing response is within the range of concentrations previously demonstrated to exist in the haemolymph and tissues of prey known to be captured by Dionaea in the field. The data is consistent with the hypothesis that narrowing and secretion are initiated by mechanical stimulation and maintained by chemical stimulation after the death of the prey.     

建兰根状茎增殖条件的研究

研究了建兰两个栽培品种的根状茎在固体及液体两种培养方式,以及培养基中有无激素和不同激素浓度配比对增殖及分化的影响。根状茎在液体培养基上的生长量都大于固体培养基上的生长量。根状茎在无激素的培养基上也能增殖。加入激素有促进作用。合适的激素浓度及配比因品种而异。     

HUNTING METHODS AND CHOICE OF PREY OF GYRFALCONS FALCO RUSTICOLUS AT MVTN IN NORTHEAST ICELAND

Gyrfalcons breeding near Myvatn in northeast Iceland were studied from 1960 until 1970. Hunting methods and successful attacks are described. The Gyrfalcon usually hunts low over the ground and tries to surprise and flush its victim and then stoop upon it. If this fails, it may pursue. The choice of prey was studied by observations from mid-May to September of Gyrfalcons carrying prey, and by examining food-remains at eyries. Ducks and Ptarmigan comprised about 49% and 41 % respectively by number of individuals, and 62% and 35 % by estimated fresh weight. One pair utilised some 88 kg of food to raise foui young. The proportion of Ptarmigan in the diet increased during the study, reflecting the increase of the Ptarmigan population and suggesting that Ptarmigan are the preferred prey since waterfowl were abundant all the time.     

影响漠斑牙鲆稚鱼的自残因子的研究

漠斑牙鲆(Paralichthys lethostigma)稚鱼阶段,自残现象比较严重。本文以漠斑牙鲆稚鱼为实验对象,选取全长10.1—40.9mm的漠斑牙鲆进行试验观察。研究了密度、浑浊度、饥饿、个体大小差异对该幼鱼自残的影响程度。(1)密度、投饲量、个体大小差异对漠斑牙鲆稚鱼的自残行为影响极显著;高密度组的比低密度组自残现象严重;饱食组的自残率较1/3饱食投饲量组别的轻;个体大小差异是引起自残最重要的因子,当投喂不充足时,(10.1±0.4)—(20.3±0.3)mm组的自残现象最为严重自残死亡率为53%。(2)饥饿对自残行为影响显著,饥饿24h后自残死亡率为20%((15.0±0.4)mm组)。(3)浑浊度、饵料种类对自残行为影响不显著,在密度为20尾/L时,无浑浊度组稚鱼自残死亡率为8%,浑浊度组5%。