Showing papers in "Journal of Zoology in 1973"

The physiology of digestion of blue‐green algae in the cichlid fish, Tilapia nilotica

Abstract: The cells of blue‐green algae are lysed by high concentrations of acid (pH 1.9–1.4) in the stomach of Tilapia nilotica. After lysis, cell contents are digested in the intestine. Acid secretion follows a diurnal cycle related to feeding, and thus there is a cycle from zero to maximum digestion each day. Some of the digestive enzymes have been studied. Blue‐green algae are lysed by a high concentration of acid in the stomach. pH 1.4 is the lowest value recorded in the stomach of T. nilotica; lysis is most effective at this pH. Enzymatic digestion occurs in the intestine, after the algae are lysed. Acid secretion in the stomachs of T. nilotica and H. nigripinnis in Lake George, Uganda, follows a diurnal cycle associated with feeding. Secretion starts when feeding starts in the morning. In T. nilotica, low pH values are not obtained throughout the stomach until feeding ceases in the evening. Thus there is a gradation through the day, from zero to maximum in number of blue‐green algal cells lysed, and therefore digested and assimilated. Colour changes in the ingested phytoplankton can be used as an indicator of gastric acid secretion by fish in the laboratory. Acid is not secreted by stressed fish. Pepsinogen was detected in the stomach wall of T. nilotica. Evidence for the absence of peptic digestion in the stomach of T. nilotica is presented. A pancreatic α‐amylase, pH optimum 7.0 to 8.0, and requiring chloride, is present in the intestinal juice of T. nilotica. Trypsin and chymotrypsin are also present, but carboxypeptidases A and B could not be detected. Esterase activity, but no lipase, was detected in the intestine juice. 1973 The Zoological Society of London

Continental drift, paleoclimatology, and the evolution and biogeography of birds

Abstract: An analysis is presented of the influence that late Mesozoic and Tertiary paleogeography and paleoclimatology may have had on the evolution and biogeography of birds. Many intercontinental connections, especially in the Southern Hemisphere, persisted until the late Cretaceous and/or early Tertiary. Moreover, climates at these times were warmer and more equable than in the late Tertiary, and birds could breed in and disperse through high latitudes. It is concluded that a number of avian orders and families had their origin in Gondwanaland and predrift configurations of the continents were major determinants of their biogeography. Penguins, ratites, galliforms, and suboscines among others are the best examples. Tropical-subtropical Eurasia was probably the centre of origin for the oscines, and primitive stocks entered the New World mostly through Beringia and mostly prior to the Miocene (but also via a North Atlantic land connection prior to the early Eocene). Continental drift and paleoclimatology have clearly influenced the evolution and biogeography of birds, and future advances in the systematics of the higher taxa will undoubtedly provide further confirmation of this.

A mechanical analysis of a hind leg of a frog (Rana temporaria)

Abstract: An attempt is made to relate the structure and properties of the principal extensor muscles and bones of the frog leg, to their performance in jumping and swimming. The following data are presented in turn. First, the muscles are described and their dimensions, and moment arms about the joints, are given. Secondly, the maximum isometric tension of each muscle, measured in tests with excised muscles, is reported. Stresses are calculated from these forces and the dimensions previously given. Thirdly, measurements are presented of the changing angle of each joint as the leg extends in jumping, and of the magnitude and direction of the forces exerted on the ground (measured by means of a force platform). The angles are used, in conjunction with the moment arms, to calculate the range and rate of shortening of each muscle, and hence the strain and rates of strain of their component fibres. The forces are used, with the moment arms, to calculate the forces and stresses exerted by the muscles. Fourthly, measurements taken from film of frogs swimming are used to estimate the force exerted on the water during the propulsive stroke. Muscle performance in swimming and jumping is compared. Finally, measurements of the stiffness and strength in bending of the femur and tibiofibula are presented, and related to the forces which act in jumping. The Discussion section of the paper includes an attempt to define the optimal working conditions for a muscle subjected to inertial loading.

Conception dates in relation to age and condition in two populations of Red deer in Scotland

Abstract: The conception dates of wild Red deer (Cervus elaphus L.) in two parts of Northern Scotland (the Isle of Rhum in the Inner Hebrides, and Glen Feshie in the Central Highlands) were estimated from foetus weights and from the known birth dates of calves. In both localities, the conceptions were spread over periods of about 100 days from late September to late December with a peak in October. The median conception date was seven to ten days earlier on Rhum than at Glen Feshie. The conception data from shot hinds showed distinct patterns in relation to age, whether or not the hinds had current year's calves, and to body condition. Body condition may be the most important “secondary factor” influencing the time of conception; hinds in poor condition tended to conceive later than those in good condition. Body condition could also account for year to year fluctuations in the time of breeding; hinds tended to breed earlier in years when they were in better condition.

Quantitative estimation of the daily ingestion of phytoplankton by Tilapia nilotica and Haplochromis nigripinnis in Lake George, Uganda

Abstract: A direct method has been used to estimate the amount of phytoplankton ingested per day by herbivorous fish in Lake George, Uganda The quantities ingested are linearly related to the weight of the fish, as given by the following regression equations: for Tilapia nilotica: y= 271+133 x and for Haplochromis nigripinnis: y=–296+219 x, where y is the dry weight of phytoplankton (mg) ingested per day and x is the wet weight of the fish (g) Summary Tilapia nilotica and Haplochromis nigripinnis have a diurnal feeding cycle They start feeding shortly before dawn and feed continually until about dusk They do not feed during the night Although there is some individual variation, a linear increase in the average dry weight of stomach contents from dawn to dusk, and a linear decrease from dusk until about midnight is generally observed The dry weight of algae passing into the intestine increases steadily until the first algae eaten in the morning reach the end of the intestine The rates of change in these weights are used to estimate the total amount of food ingested over 24 hours It was found that the rate of passage of algae from the stomach to intestine was greater during feeding than after feeding had stopped The quantities ingested are linearly related to the weight of the fish, as given by the following regression equations: T nilotica y= 271+133 x H nigripinnis y=–296+219 x where y is the dry weight of phytoplankton (mg) ingested per day and x is the wet weight of the fish (g)

The functional significance of the spermatophore and the fate of spermatozoa in the genital tract of Helix pomatia (Gastropoda: Stylommatophora)

Abstract: In the Helicidae and in some other Stylommatophora the sperm are transferred in a spermatophore, even though there appears to be no need for protection of the sperm during the transfer. The function of the spermatophore and related problems concerning the genital organs of Helix pomatia were studied by means of morphological and experimental methods. The spermatophore is necessary to ensure the functioning of the female system at copulation. Its structure allows some of the spermatozoa it contains to escape through its tail canal, pass from the stalk of the bursa and reach the spermatheca by way of the oviduct; but most of the sperm pass into the bursa copulatrix and are destroyed, as is also the fate of the spermatophore. Only foreign sperm are stored in the spermatheca. Spermiogenesis was found to take place throughout the whole summer. At intervals some sperm are released from the hermaphrodite duct and are conducted via the spermoviduct and oviduct to the bursa, where they are digested. The two grooves of the spermoviduct are functionally separated only for a few minutes at actual copulation, when sperm are conducted to the copulatory organs, where the spermatophore is being formed.

The osteology and adaptive features of Rhyacichthys aspro (Teleostei: Gobioidei) and the classification of gobioid fishes

Abstract: The osteology of the gobioid fish Rhyacichthys aspro (Valenciennes, 1837), from tropical hill-streams of the Indo-Australasian archipelago, is described. Adaptive features of external form and skeleton are considered with reference to life in torrential conditions. The systematic position of Rhyacichthys in the suborder Gobioidei is confirmed, and structure of the caudal skeleton in this genus, with other features, is found to support an acanthopterygian rather than paracanthopterygian origin for the gobioid fishes. In lateral-line system (here redescribed) and caudal skeleton, Rhyacichthys is shown to possess primitive features unique among gobioids. Previous systems of internal classification for the Gobioidei, and the inadequate fossil record of the group, are summarized, and the systematic value of certain skeletal criteria discussed. The suborder is now reclassified on a phylogenetic basis into two families, Rhyacichthyidae and Gobiidae, with the latter divided into seven sub-families: Eleotrinae, Pirskeninae, Xenisthminae, Gobionellinae, Tridentigerinae, Gobiinae, and Kraemeriinae.

Arthropod phylogeny—a modern synthesis*

Abstract: Factual evidence provided by the fields of functional morphology and of the newer functional studies of embryology using the concept of fate maps indicates that the Arthropoda are probably polyphyletic and that arthropodization has occurred at least three times, forming the phyla Crustacea, Chelicerata and Uniramia (Onychophora, Myriapoda, Hexapoda). When the latter left the sea they probably possessed a soft body and lobopodial limbs and showed incipient cephalization. Only the muscular haemocoelic mechanism of movement of the lobopodium, but not that of a parapodium, could have given rise to the jointed uniramian limbs. The three subphyla of the Uniramia are differentiated by their jaw mechanisms, associated head structure and limb-bases. The habits associated with the divergence of the four myriapodan classes account for their morphological distinctions. The five hexapod classes differ from one another in leg-base mechanisms and have probably been evolved independently from five groups of multilegged soft bodied ancestors with a head type contrasting with that of the Myriapoda. Reference is made to the great differences between arachnid adaptations of limbs, gaits, etc., to land life compared with those of the Uniramia. No new evidence is given concerning the status of the Trilobita.

Nervous control of the syrinx in White‐throated sparrows (Zonotrichia albicollis)

Abstract: This study reports the results of sectioning of the motor nerves to the syrinx and tongue in 31 North American White-throated sparrows, Zonotrichia albicollis. Unilateral sectioning of the hypoglosso-cervicalis and its branch the cervicalis descendens superior to the syrinx produce maximum qualitative distortions when performed on the left side and none, or hardly any, when performed on the right side. The effective operations eliminated the pure whistles of the songs which were then replaced by shrill patterns with a lower relatively constant fundamental frequency accompanied by two or more strong harmonics. Two individuals sectioned through the left hypoglosso-cervicalis were somewhat exceptional in that one continued to sing the first half of the song normally while the second half deteriorated. The second individual eventually lost its song entirely except for audible clicks apparently where the whistles would otherwise have ended. Unilateral sectioning of the cervicalis ascendens to the tongue as well as sham operations had no noticeable qualitative effects. Bilateral sectioning of the cervicalis descendens superior gave results similar to sectioning on the left side. In addition such birds produced whistles and rasping sounds in association with breathing. Some quantitative differences were noted in whistles and intervals between whistles. The occurrence of these changes were not consistent within a group and occurred widely in most groups without regard to the side operated upon. The results confirm that output of sound from the syrinx in most individuals is primarily from the left side. Membranes on the affected side continue to vibrate under the pressure of air expelled from the lungs, but with strong harmonics and at frequencies determined only by the properties of the membranes and syrinx and in relation to the force of the expelled air. Summary Sectioning of motor nerves to the syrinx of North American White-throated sparrows confirms the lateral output of song primarily by the left side of the syrinx. One individual showed evidence of singing from both sides. There is also evidence that sectioning of motor nerves may have quantitative effects on the durations of whistles and intervals between whistles, particularly at the beginnings of songs. This suggests that singing is controlled dynamically through the interaction of central and peripheral controls.

The dentition and dental tissues of the agamid lizard, Uromastyx

Abstract: The dentition of Uromastyx hardwicki was examined in a series of carefully prepared dry skulls and was found to be very different from that of other agamid lizards. The anatomy of the dentition undergoes great changes from the time of hatching to advanced age, but no evidence of tooth replacement could be found. Extension of the tooth rows by addition of larger teeth posteriorly, together with elongation of the premaxilla, and a characteristic pattern of wear are responsible for the condition seen in aged specimens. The structure of the dental tissues was investigated by means of a variety of histological techniques including scanning electron microscopy and it is established that the enamel has prismatic structure like that of mammalian enamel. The mode of formation of enamel with and without prisms is described and the occurrence and significance of prismatic structure in reptilian dental enamel discussed.

The jump of the click beetle (Coleoptera: Elateridae)—energetics and mechanics

Abstract: Some aspects of the energetics and mechanics of two jumps made by a single specimen of Athous haemorrhoidalis (Fab.) are considered. In the first jump, the 40 mg beetle had a take-off velocity of 2–4 m/s and the jumping action occurred in about 064 ms; in the second jump, the take/off velocity was 2–26 m/s and the jumping action took about 0–53 ms. Energy budgets have been constructed in two different ways for each jump, and the total energy involved in each case was estimated to lie between 1–6 × 10−4 J and 3–8 × 10−4 J. Power output during the jumping action (a “catapult”) lay between 80 × 103 W/kg muscle and 180 × 103 W/kg muscle, whilst power output during the energy storing pre-jump period (of about 0–4 s) was at least 130 W/kg muscle (at over 25°C). Forces and tensile stresses in the jumping muscles and their apodemes have also been calculated. The method of jumping appears to be fairly inefficient in that only about 50–60% of the energy expended in the jumping action is energy of translation, which actually raises the beetle.

The metazoan parasite‐fauna of fish from Hanningfield Reservoir, Essex in relation to features of the habitat and host populations

Abstract: A survey of the metazoan parasite-fauna of eight species of fish from Hanningfield Reservoir, Essex was carried out between January 1968 and March 1969. 56 Brown trout, 89 Rainbow trout, 181 Perch, 165 Ruffe, 31 Roach, 31 Ten-spined Sticklebacks, four Eels and one Stone-loach were examined. In addition, 125 Rainbow trout were examined from adjacent raceways. Thirty-one species of parasites were found, five Monogenea, nine Cestoda, eight Digenea, one Acanthocephala, four Nematoda, one Annelida, one Mollusca and two Crustacea. The possible origins of the parasite fauna are discussed. The relative abundance of different groups of parasites is considered in relation to the physical and biotic features of the habitat. Parasite species with planktonic crustacean intermediate hosts and/or avian final hosts are particularly abundant. The introduction of trout has resulted in an oligotrophic element being added to an otherwise eutrophic parasite fauna. Possible changes in the parasite-fauna which may have occurred since construction of the reservoir are described. The parasite-fauna of Rainbow trout from the raceways was found to be a reduced version of that of fish from the reservoir.

Stabilimenta on the webs of Uloborus diversus (Araneae: Uloboridae) and other spiders

Abstract: Uloborus diversus places extra silk (“stabilimenta”) near the hubs of its webs, preferentially on short radii ending near anchor threads. Spiders probably distinguish these radii from others by their relatively low extensibility. The stabilimentum probably functions as a camouflage device, and the orientation of the stabilimentum lines probably aids disturbed spiders in making quick exits from webs. Turning responses at radius-frame junctions during these exits are influenced by thread angles at the junctions (and possibly by other factors), and also enable disturbed spiders to reach hiding places quickly. The available data on other stabilimentum-building spiders suggests that they also use stabilimenta to provide defence against visually-hunting predators.

Surface area of the respiratory organs of the Climbing perch, Anabas testudineus (Pisces: Anabantidae)

Abstract: Measurements have been made of the surface area of the gills and accessory respiratory organs of Anabas in the weight range 1–120 g, and the data analysed with respect to body weight using logarithmic transformations. The slope of the regression line for total gill area (0–615) is less than that found in most fish, the number of secondary lamellae/mm decreased more rapidly with body weight than for most water-breathing species (h = -0.152). The gill area of Anabas is relatively small but when the area of the accessory organs is added, the total respiratory area is of the same order as inactive water-breathing fish. The regression coefficient for combined areas of labyrinthine organs and lining of the suprabranchial chambers (0.713) exceeds that for the gills and together with other evidence (including estimates of diffusing capacity from morphological measurements), indicates an increasing importance of air-breathing of larger specimens. The average surface area of the accessory organs available for 1 ml of air within the suprabranchial chambers was found to be 2226 mm2.

Nature of the air-breathing organs of the Indian fishes Channa, Amphipnous, Clarias and Saccobranchus as shown by electron microscopy

Abstract: The structure of the air-breathing organs of the Indian fishes Channa punctatus, Channa Striatus, Amphipnous cuchia, Clarias batrachus and Saccobranchus fossilis has been investigated using electron microscopy. In all species the barrier separating the air from the blood consists of three main layers (epithelium, basal lamina and endothelium). The total thickness ranging from 0.78 μm in C. punctatus 1.6 μm in S. fossilis. In Clarias and Saccobranchus the presence of pillar cells characteristic of gill secondary lamellae confirms evidence for the origin of these organs by modification of a typical gill structure. In Amphipnous and two species of Channa, however, the evidence suggests that the accessory organs represent modified gills. The presence of valve-like structures between the afferent and efferent blood spaces of the vascular papillae gave the appearance of pillar cells under the light microscope. The structure of these organs is correlated with physiological studies on the degree of their importance in the life of the animal and the degree of gill development

Observations on the morphology, behaviour and salinity tolerance of downstream migrating River lampreys (Lampetra fluviatitis)

Abstract: Downstream migrating Lampetra fluviatitis were caught at night in elver trawls from the lower reaches of the River Severn during the high spring tides of 1970,1971 and 1972. The length and weight-frequency curves indicated that in 1970 and 1972, the populations consisted mainly of animals of single year class. On the basis of previous estimates of the duration of larval life, they were thus probably five years old, while a small group of larger animals may have been one year older. In 1971, there was a greater proportion of larger animals, several of which differed in their weight/length relationship from others in this sample and from those of 1971 and 1972, possibly reflecting differences in feeding conditions during larval life. Laboratory studies on the activity rhythms of downstream migrants showed that emergence from the substrate and swimming was primarily nocturnal, with an initial large peak in free-swimming activity at the onset of darkness and a smaller peak at the transition from the dark to the light phase. During the light period, these animals showed a significant preference for burrowing or lying in regions of gravel and pebbles. Downstream migrants examined in May/June 1972 were capable of being acclimated to full strength sea water (34–35°/00) and a large proportion (80%) survived for three weeks or more after direct transfer. Parallels are drawn between the biology of this stage in the lamprey life cycle with that of similar stages in salmonid fishes.

The food of the Common frog, Rana temporaria, on high moorland in northern England

Abstract: Analysis of the stomach contents of 427 Common frogs, Rana temporaria L., captured on an area of moorland typical of the northern Pennines, showed that this species is an unspecialized and opportunistic feeder in this habitat. There was a distinct temporal variation in the food eaten which was closely related to its availability. Adult Tipulidae and Lepidoptera larvae each formed a fifth of the diet by volume, while Phalangidae, Coleoptera, and Gastropoda, each formed about a tenth. The diet of the frogs changes as they grow. Small frogs fed almost entirely on small items. The bigger the frog the wider the range of items eaten and the larger the items which were predominantly eaten.

Further observations on the food of seals

Abstract: Studies of the food of seals on Scottish coasts were continued at the Marine Laboratory from 1967 to 1971. In general the results confirmed those of 1958–66 in stressing the supreme importance of fish, particularly species of economic value, in the food of both the Grey and Common seals. Four families of fish–salmonids, gadoids, clupeoids and pleuronectids– were again prominent in the food of both species of seal although the frequencies with which they appeared in the stomachs varied from one period to another. Grey seals preyed more heavily on salmonids and gadoids and Common seals on gadoids and clupeoids. Changes in the diet of seals from one year to another would appear to arise from the sampling of the seals for examination and to the availability of the species offish preyed upon, depending on seasonal movements and natural fluctuations in their age–groups.

Population dynamics of the African elephant (Loxodonta africana)

Abstract: Recent studies on elephant populations from East Africa and from Zambia have suggested that as population density increases, so does the mean age at puberty and the mean calving interval. At the same time there is also an increase in the proportion of old females that are reproductively inactive. By constructing elephant population models, it is possible to investigate the extent to which these “homeostatic mechanisms” will regulate an elephant population. The models indicate that a change in the duration of the calving interval is more important as a population regulating mechanism than a change in the age at puberty, and that the proportion of old reproductively inactive females is of little significance. The importance of neonatal mortality in controlling population growth is emphasised by the models, and they also show that an annual population increase of 4% would be close to the maximum value.

A comparative study of the biology of the Giant wetas Deinacrida heteracantha and D. fallai (Orthoptera : Henicidae) from New Zealand

Abstract: The complete life cycle of Deinacrida fallai Salmon and D. heteracantha White takes a little over two years. In neither species is the cycle tied very rigidly to the seasons. About four months is required for the development of the egg; nymphal stages last 12 to 14 months in D. fallai, and about 18 months in D. heteracantha; adult females of D. fallai live about eight months and males about 11 months; adult females of D. heteracantha live about four and a half months and males about seven months. Nymphs of D. heteracantha have a marked winter diapause. This is much less pronounced in D. fallai. D. fallai become adult in the late autumn, and D. heteracantha in the spring. The sex ratio is uneven with a preponderance of females to males. Maturation of the gonads is more rapid in D. heteracantha than in D. fallai. Mating occurs through most of the year, normally during daylight. Four different body positions have been observed, vertical turning of the male under the female being most common. This position has not previously been recorded in the Gryllacridoidea. Only one spermatophore is produced at a time, but up to six or eight may be produced in a day. Deinacrida possesses four of the seven hypothetical primitive characters for genetalic structure and copulatory behaviour suggested by Alexander & Otte (1967). Oviposition occurs at night and eggs are laid individually in the soil, with a mean of 27 laid at any one time. They are laid over a three months period in D. fallai, and a two months period in D. heteracantha. Nine nymphal instars are passed through in D. fallai, and 10 in D. heteracantha. After the first four instars D. heteracantha is heavier than D. fallai. Before oviposition the female body weight increases up to 200% in D. heteracantha, and up to 100% in D. fallai. Regeneration of portions of appendages occurs in both species. Reduplication may also occur. The process of ecdysis is similar to that in other species of Orthoptera. The exuvia is colourless. It is eaten in D. fallai, and discarded in D. heteracantha. Variations in colour of different instars are recorded. The mortality rate in both species is very high. Favourite habitats for wetas are on kanuka, pohutukawaand fan palms. Both species are primarily vegetarian, but in captivity cannibalism occurs. Both species are nocturnal. Harriers and moreporks are predators of the wetas. A number of potential predators are listed. Protective behaviour consists of burrowing head first into soft earth, or hiding under loose bark or inside holes in rotten wood. In both species males are more aggressive than females, and can display sexual aggression. Two distinctive types of sound producing mechanisms are present in both sexes and are a generic characteristic. Apart from Deinacrida, abdominal stridulation has not been recorded amongst Orthoptera. This is the first detailed study of the biology of species belonging to the Henicidae.

Fine structure of the respiratory organs of the Climbing perch, Anabas testudineus (Pisces: Anabantidae)

Abstract: An electron microscopic study has been made of the three respiratory organs of climbing perch. The gill structure is similar to that of the other telcosts but the thickness of the water/blood barrier is much greater, being as great as 20 μm in some specimens. The increased thickness is due to a multilayered epithelium which is thinner (3.5–7 μm) over the marginal channel of the secondary lamellae. The other two main layers, basement membrane and pillar cell flange, are relatively thin (about 1 μm). The pillar cells have a typical structure, but in certain regions they are contiguous with one another and line well-defined blood channels. Some of the columns of basement membrane material in such regions may be common to adjacent pillar cells. The air-breathing organs are (a) the lining of the suprabranchial chambers, and (b) the labyrinthine plates attached to the dorsal region of branchial arches. Electron microscopy showed that their structure is well adapted for gas exchange, the air/blood barriers being only 0.12–0.3 μm, comprising an epithelial layer, basement membrane, and thin capillary endothelium. The many parallel blood channels of the respiratory islets of both organs are separated by pillar-like structures which differ from the pillar cells of the secondary lamellae. Thus the hypothesis that the air-breathing organs represent modified gills is not supported by this study. The fine structure of the non-respiratory region of the air-breathing organs is similar to that of the skin, and includes chemoreceptor-like cells. Evidence concerning the possible homology of pillar cells with plain muscle cells is discussed.

A comparative histochemical survey of enzymes associated with the processes of digestion in Ostrea edulis and Crassostrea angulata (Mollusca: Bivalvia)

Abstract: No major differences in either concentration or location of enzymes were noted between the two species. An increase in enzyme production was noted in “fed” individuals–this being a direct response to the presence of food material. The gastric shield of both species was found to possess enzymic activity. The epithelium responsible for secretion of the crystalline style was also seen to secrete digestive enzymes which would be incorporated into the matrix of the style. Exopeptidases were identified in the walls of blood vessels and are attributed with the role of continued digestion of food material, prior to transport around the body. The mid-gut contains a number of enzymes in high concentrations and serves a digestive as well as an absorptive role. Lipid is seen to be an important storage product, especially in the connective tissue surrounding the digestive diverticula.

The aggressive behaviour of individual male polecats (Mustela putorius, M. furo and hybrids) towards familiar and unfamiliar opponents

Abstract: Experiments are described which were designed to investigate the significance of individual differences in aggressiveness between polecats and the relation between the familiarity of the opponent and the pattern and outcome of fighting. The behaviour of Mustela putorius, M. furo and hybrids between the two species was investigated in an indoor arena of 16 m2. Two kinds of fighting between male polecats were recorded, “companion fighting” between cage mates, in which biting was inhibited and neither of the opponents became intimidated and “uninhibited fighting” between unfamiliar individuals from which a winner and loser generally emerged and a rank order formed. Individual differences in aggressiveness were assessed by means of a scoring system which statistical analysis showed, generally, to be consistent for any one individual. The rank of an animal, however, was found not to be invariably related to its aggression score. A number of other factors influencing fighting were investigated, the earlier introduction of one individual into the arena increases its chances of winning a fight; when offered a choice, male polecats fight strangers in preference to cage mates; and the separation of a group of cage mates for as little as 48 hours induces them to behave towards one another like strangers with the result that a rank order is formed. Factors which had no apparent effect on fighting between males were the weight of the individual or the presence of females. The attributes of familiar and unfamiliar opponents are discussed in the light of these findings.

Factors influencing the breeding of the rabbit flea (Spilopsyllus cuniculi): A spring‐time accelerator and a kairomone in nestling rabbit urine with notes on Cediopsylla simplex, another “hormone bound” species

Abstract: Accelerated impregnation and maturation of the rabbit flea coincides with the spring peak litter-size of the rabbit, but its breeding performance falls off before that of the domestic host. A kairomone nestling factor, which boosts copulation, impregnation and development of fleas feeding on the newborn young, is also present in relatively feeble amounts in baby rabbit urine. This urine boosts pairing of matured (=“primed”) fleas united in tubes away from a host, but impregnation is increased only if fleas are feeding on newborn young while exposed to the urine. Undeveloped fleas matured on the pregnant doe require a transfer to another host before they will pair, whereas fleas matured on the nestlings copulate without a transfer. A variable time-lag between transfer and copulation of fleas, dependent on the “priming” qualities of the preparatory host, suggests that a chemical intermediary is involved. If the antennae of the females are coated with vaseline, the maturation of these fleas is delayed feeding on nestlings, but not on the prepartum doe. This delay is less marked during the spring acceleration than at other times of the year. The breeding of a North American species of hare flea (Cediopsyllu simplex (Baker)) parasitizing Sylvilagus floridanus (Allen) is also controlled by the sex hormones of the host.

The anatomical basis of function in the buccal mass of prosobranch and amphineuran molluscs

Abstract: A comparative account is given of the muscular anatomy of the buccal mass in chitons and a number of species of prosobranch gastropods. From this can be deduced a basic muscular organization consisting of buccal constrictors and dilators, protractors and retractors of the odontophore, protractors and retractors of the subradular membrane and an approximator muscle of the supporting cartilages. In addition to these many ancillary muscles act as tensors: these are numerous in chitons, monoplacophorans and rhipidoglossan proso-branchs. In the first two groups, which have a poorly developed anterior end covered by a shell, they act in place of the muscles of the mobile wall of the head of gastropods; in the last they are necessary for the fine control of an odontophore brushing the substratum. In prosobranchs which forcibly rasp their food they are lost. The dominating influence in the evolution of the buccal mass in neogastropods is the proboscis. Its narrowness and elongation have had profound effects on the anatomy of the buccal mass.

Observations on the Cladocera of Lake George, Uganda

Abstract: Seven species of Cladocera were recorded from the shallow, equatorial Lake George in Uganda, during the period 1967–72. Of these only three, Moina micrura Kurz, Ceriodaphnia cornuta Sars and Daphnia barbata Weltner, are found in the open water and they form a small proportion of the total zooplankton biomass, which is dominated by a cyclopoid copepod. All three species are found throughout the year and carry parthenogenetic eggs at all times. They are smaller species than those predominating in some other East African lakes and some comparisons are also made between C. cornuta and four other species of that genus studied in Great Britain. The mean body lengths and clutch sizes of ovigerous females of C. cornuta vary little through the year. This is, presumably, a reflection of the relatively constant environment in Lake George. Alona poppei is only found in the open water intermittently and is thought to be swept from the peripheral swamps during heavy rains. The general scarcity of Cladocera in Lake George is thought to be due, either to a shortage of food particles of suitably small size in the phytoplankton, which is dominated by large blue-green algae, or to predation. Although Cladocera are certainly eaten by fish, quantitative data, with which to substantiate either of these hypotheses, is lacking.

The fine structure of the pallial eyes of Laternula truncata (Bivalvia: Anomalodesmata: Pandoracea)

Abstract: The structure of the pallial eyes of Laternula truncata (Lamarck 1818) has been studied using the light and electron microscopes. The eye is complex and can be- considered to be- the most advanced yet described for a bivalve mollusc. The cornea consists of modified flattened epithelial cells with an external border of microvilli. The cornea covers a large, circular, multinucleate lens. The lens comprises (1) centrally located translucent lens cells, (2) laterally located supporting cells from which cell processes interdigitate with processes from the lens cells. The retina is two layered and inverted. The proximal and distal retinae are made up of concentrically arranged laminae derived from the membranes of ciliary basal bodies. The cilia comprise a base and feet, but no root system and have a 9+0 arrangement of filaments. The pigment cup or tapetum is bounded by a sclerotic coat and is three layered, each layer possessing characteristic pigment granules. From the base of the eye arises a large optic nerve. The eye possesses an eye appendage, the epithelium of which is invaginated on its internal border to form a groove within which are found some 28 cilia. The cilia, it is thought, make contact with the microvilli of the epithelium when the appendage is touched. Such an action serves to protect the delicate eye from damage. The structure of the eye is compared with that of other molluscs, particularly members of the Bivalvia.

Chance and change in British Long‐tailed field mice: (Apodemus sylvaticus)

Abstract: The Long-tailed field mouse (Apodemus sylvaticus (L.)) has undergone a marked degree of racial differentiation on the islands of the north-west Atlantic (Iceland, Shetland, and the Hebrides). The differences have arisen as a result of the colonization of these islands after the Pleistocene by small numbers of animals carrying alleles in different proportions to those in the parental population. In contrast, the populations on some islands to the south of Britain (Jersey and Guernsey in the Channel Isles, and St. Mary's in the Isles of Scilly) are similar to A. sylvaticus from the mainland of Britain, and are likely to represent the descendants of mice which survived the Ice Ages (A. sylvaticus populations on the smaller islands–Alderney, Sark, Herm and Tresco–differ markedly from their closest relatives, and probably represent the results of recolonization following extinction in the same way as on the glaciated islands to the north). On the mainland of Britain there is a fairly clear distinction between two groups: western and central populations, and eastern ones (which have closer affinities to French mice than western British ones). It is suggested that the two mainland British “races” may have diverged in Pleistocene refuges. Since no pelage or size genes are involved in the divergence, it would not be expected that they would be taxonomically distinct. The data on which these conclusions are based derive from the incidence of 20 nonmetrical variants in the skulls of 1096 mice from 22 series.

Observations of the comparative anatomy and ultrastructure of mammary glands and on the fatty acids of the triglycerides in platypus and echidna milk fats

Abstract: As far as gross structure is concerned the mammary glands of the monotremes consist of discrete lobules, in effect compound alveolar glands similar to those of the fully lactating marsupial. Ultrastructurally all mammary glands, prototherian, metatherian, and eutherian are identical, the alveoli consisting of a secretory epithelium invested by myoepithelium. The processes of formation and secretion of casein and milk fat are the same in the glands of all three subclasses of the Mammalia. In spite of close structural similarities the fatty acid complements of the milk triglycerides of the two monotremes, platypus and echidna, are different: echidna milk fat contains far more oleic acid than platypus milk does.