We describe a new octoploid species of African clawed frog (Xenopus) from the Lendu Plateau in the northern Albertine Rift of eastern Democratic Republic of the Congo. This species is the sister taxon of Xenopus vestitus (another octoploid), but is distinguished by a unique morphology, vocalization and molecular divergence in mitochondrial and autosomal DNA. Using a comprehensive genetic sample, we provide new information on the species ranges and intra-specific diversity of African clawed frogs from the Albertine Rift, including the details of a small range extension for the critically endangered Xenopus itombwensis and previously uncharacterized variation in Xenopus laevis. We also detail a new method for generating cytogenetic preparations in the field that can be stored at room temperature for up to 3 weeks. While extending our understanding of the extant diversity in the Albertine Rift, this new species highlights components of species diversity in ancestral African clawed frogs that are not represented by known extant descendants.
We use the term 'aggressive mimic' for predators that communicate with their prey by making signals to indirectly manipulate prey behaviour. For understanding why the aggressive mimic's signals work, it is important to appreciate that these signals interface with the prey's perceptual system, and that the aggressive mimic can be envisaged as playing mind games with its prey. Examples of aggressive mimicry vary from instances in which specifying a model is straight forward to instances where a concise characterisation of the model is difficult. However, the less straightforward examples of aggressive mimicry may be the more interesting examples in the context of animal cognition. In particular, there are spiders that prey on other spiders by entering their prey's web and making signals. Web invasion brings about especially intimate contact with their prey's perceptual system because the prey spider's web is an important component of the prey spider's sensory apparatus. For the web-invading spider, often there is also a large element of risk when practising aggressive mimicry because the intended prey is also a potential predator. This element of risk, combined with exceptionally intimate interfacing with prey perceptual systems, may have favoured the web-invading aggressive mimic's strategy becoming strikingly cognitive in character. Yet a high level of flexibility may be widespread among aggressive mimics in general and, on the whole, we propose that research on aggressive mimicry holds exceptional potential for advancing our understanding of animal cognition.
Pigmentation disorders such as albinism are occasionally associated with hearing impairments in mammals. Therefore, we wanted to investigate whether such a phenomenon also exists in non-mammalian vertebrates. We measured the hearing abilities of normally pigmented and albinotic specimens of two catfish species, the European wels Silurus glanis (Siluridae) and the South American bronze catfish Corydoras aeneus (Callichthyidae). The non-invasive auditory evoked potential (AEP) recording technique was utilized to determine hearing thresholds at 10 frequencies from 0.05 to 5 kHz. Neither auditory sensitivity nor shape of AEP waveforms differed between normally pigmented and albinotic specimens at any frequency tested in both species. Silurus glanis and C. aeneus showed the best hearing between 0.3 and 1 kHz; the lowest thresholds were 78.4 dB at 0.5 kHz in S. glanis (pigmented), 75 dB at 1 kHz in S. glanis (albinotic), 77.6 dB at 0.5 kHz in C. aeneus (pigmented) and 76.9 dB at 1 kHz in C. aeneus (albinotic). This study indicates no association between albinism and hearing ability. Perhaps because of the lack of melanin in the fish inner ear, hearing in fishes is less likely to be affected by albinism than in mammals.
Species that sequester toxins from prey for their own defense against predators may exhibit population-level variation in their chemical arsenal that reflects the availability of chemically defended prey in their habitat. Rhabdophis tigrinus is an Asian snake that possesses defensive glands in the skin of its neck ('nuchal glands'), which typically contain toxic bufadienolide steroids that the snakes sequester from consumed toads. In this study, we compared the chemistry of the nuchal gland fluid of R. tigrinus from toad-rich and toad-free islands in Japan and determined the effect of diet on the nuchal gland constituents. Our findings demonstrate that captive-hatched juveniles from toad-rich Ishima Island that had not been fed toads possess defensive bufadienolides in their nuchal glands, presumably due to maternal provisioning of these sequestered compounds. Wild-caught juveniles from Ishima possess large quantities of bufadienolides, which could result from a combination of maternal provisioning and sequestration of these defensive compounds from consumed toads. Interestingly, juvenile females from Ishima possess larger quantities of bufadienolides than do juvenile males, whereas a small sample of field-collected snakes suggests that adult males contain larger quantities of bufadienolides than do adult females. Captive-born hatchlings from Kinkasan Island lack bufadienolides in their nuchal glands, reflecting the absence of toads on that island, but they can sequester bufadienolides by feeding on toads (Bufo japonicus) in captivity. The presence of large quantities of bufadienolides in the nuchal glands of R. tigrinus from Ishima may reduce the risk of predation by providing an effective chemical defense, whereas snakes on Kinkasan may experience increased predation due to the lack of defensive compounds in their nuchal glands.
IN THEORY, SNAILS CAN COME IN TWO ENANTIOMORPHS: either dextral (coiling clockwise) or sinistral (coiling counter-clockwise). In snail species where both forms are actually present, coiling direction is determined by a single gene with delayed maternal inheritance; there is no predictable relationship between a snail's own coiling genotype and its actual coiling direction. Because of this genetic decoupling, it might be expected that dextral and sinistral individuals would be exact mirror images of one another. However, indications exist that there is a subtle but detectable shape difference between dextral and sinistral individuals that derive from the same gene pool. In this paper, we attempt to detect such differences in 50 dextral and 50 sinistral individuals of Amphidromus inversus, a species of land snail that is consistently chirally dimorphic. Four out of 18 volunteers who measured the shells with Vernier calipers found that sinistrals are stouter to a significant degree. A similar result was found by one out of five volunteers who measured the shells from photographs. These results do not allow distinguishing between real shape differences and a handling bias of sinistral as compared with dextral shells. However, when the same set of shells was subjected to a geometric morphometric analysis, we were able to show that sinistrals indeed exhibit a slight but significant widening and twisting of the shell near the palatal and parietal apertural areas. This result is surprising because species of the subgenus Amphidromus s. str. share a long history of chiral dimorphism, and the species would be expected to have been purged from disadvantageous interactions between direction of coil and general shell shape. We conclude that selection on the shape differences is either very weak or constrained by the fact that the pleiotropic effects of the chirality gene are of importance very early in development only.
ALTHOUGH MANY TOOTHED WHALES (CETACEA: Odontoceti) lactate for 2-3 years or more, it is not known whether milk composition is affected by lactation stage in any odontocete species. We collected 64 pooled milk samples spanning 1-30 months postpartum from three captive bottlenose dolphins Tursiops truncatus. Milks were assayed for water, fat, crude protein (TN × 6.38) and sugar; gross energy was calculated. Ovulation and pregnancy were determined via monitoring of milk progesterone. Based on analysis of changes in milk composition for each individual dolphin, there were significant increases (P<0.05) in fat (in all three dolphins) and crude protein (in two of three), and a decrease (P<0.05) in water (in two of three) over the course of lactation, but the sugar content did not change. In all three animals, the energy content was positively correlated with month of lactation, but the percentage of energy provided by crude protein declined slightly but significantly (P<0.05). At mid-lactation (7-12 months postpartum, n=17), milk averaged 73.0±1.0% water, 12.8±1.0% fat, 8.9±0.5% crude protein, 1.0±0.1% sugar, 1.76±0.09 kcal g(-1) (=7.25 kJ g(-1)) and 30.3±1.3% protein:energy per cent. This protein:energy per cent was surprisingly high compared with other cetaceans and in relation to the growth rates of calves. Milk progesterone indicated that dolphins ovulated and conceived between 413 and 673 days postpartum, following an increase in milk energy density. The significance of these observed compositional changes to calf nutrition will depend on the amounts of milk produced at different stages of lactation, and how milk composition and yield are influenced by sampling procedure, maternal diet and maternal condition, none of which are known.
Body size is an important determinant of resource and mate competition in many species. Competition is often mediated by conspicuous vocal displays, which may help to intimidate rivals and attract mates by providing honest cues to signaler size. Fitch proposed that vocal tract resonances (or formants) should provide particularly good, or honest, acoustic cues to signaler size because they are determined by the length of the vocal tract, which in turn, is hypothesized to scale reliably with overall body size. There is some empirical support for this hypothesis, but to date, many of the effects have been either mixed for males compared with females, weaker than expected in one or the other sex, or complicated by sampling issues. In this paper, we undertake a direct test of Fitch's hypothesis in two canid species using large samples that control for age- and sex-related variation. The samples involved radiographic images of 120 Portuguese water dogs Canis lupus familiaris and 121 Russian silver foxes Vulpes vulpes. Direct measurements were made of vocal tract length from X-ray images and compared against independent measures of body size. In adults of both species, and within both sexes, overall vocal tract length was strongly and significantly correlated with body size. Effects were strongest for the oral component of the vocal tract. By contrast, the length of the pharyngeal component was not as consistently related to body size. These outcomes are some of the clearest evidence to date in support of Fitch's hypothesis. At the same time, they highlight the potential for elements of both honest and deceptive body signaling to occur simultaneously via differential acoustic cues provided by the oral versus pharyngeal components of the vocal tract.
Scat analysis is one of the most frequently used methods to assess carnivoran diets and Global Positioning System (GPS) cluster methods are increasingly being used to locate feeding sites for large carnivorans. However, both methods have inherent biases that limit their use. GPS methods to locate kill sites are biased towards large carcasses, while scat analysis over-estimates the biomass consumed from smaller prey. We combined carcass observations and scats collected along known movement routes, assessed using GPS data from four African lion (Panthera leo) prides in the Kruger National Park, South Africa, to determine how a combination of these two datasets change diet estimates. As expected, using carcasses alone under-estimated the number of feeding events on small species, primarily impala (Aepyceros melampus) and warthog (Phacochoerus africanus), in our case by more than 50% and thus significantly under-estimated the biomass consumed per pride per day in comparison to when the diet was assessed using carcass observations alone. We show that an approach that supplements carcass observations with scats that enables the identification of potentially missed feeding events increases the estimates of food intake rates for large carnivorans, with possible ramifications for predator-prey interaction studies dealing with biomass intake rate.
SUMMARY1The equatorial lizard Agama agama Eionotus possesses a distinct breeding period which occurs during the peak of the seasonal harvest of protein animal food that follows the so-called “long rains”. The males contain bunches of spermatozoa throughout the year.2As the proportion of ingested animal food increases, the sexual condition of the females heightens. There is a concurrent growth of large leaf-shaped abdominal fat bodies. Widespread egg-laying occurs during four months of the year (June-September inclusive), the peak being in July and early in August.3During the height of reproduction three distinct phases of egg development can be seen macroscopically: 1, a layer of colourless ovarian eggs surmounted by 2, a series of yolked eggs and 3, a clutch of ten to twelve shelled oviducal eggs. This device enables quick and repeated ovulation during the period of the maximum insect harvest.4During the period of study one ovulation only was recorded after the so-called “short rains”. This occurred in February and after unusually heavy precipitation during the, previous December.5Any possibility of the photoperiodic control of reproduction was eliminated by the choice of the collecting locality. It is suggested that the sexual cycle of Agama agama is timed not by rainfall but by the seasonal appearance of proteinous insect food. Vegetable food of various kinds seems to be relatively abundant throughout the year. It is not known whether widespread reproduction after the secondary “short rains” is inhibited by a relative lack of protein food or, perhaps more probably, by the comparatively low night temperatures that occur from December to February inclusive.6A. agama is almost omnivorous, feeding on grass, berries, seeds, flowers, caterpillars, beetles, spiders, ants, Hymenoptera and the eggs of smaller reptiles.
In summarising these short surveys, we find the progress of “Jubilee” was assured by the keepers' disciplinary powers over the mother in enforcing her to nurse the baby, plus their additional individual help to the infant. Without this, “Jubilee's” satisfactory development would have been very doubtful.Careful nursing of “June,” owing to her weakness at birth, was of vital importance. “Sally,” in addition to being a good mother, allowed her keepers to attend her baby, and in consequence of this co-operation, “June's” development was very progressive. The very cold spell which intervened was responsible for the decline in the mother's health and the cause of the infant developing broncho-pneumonia. The refusal of “Sally” to allow us to nurse her young one during her illness finally decided her baby's death. The good development of “June,” aided by the co-operative nursing, and her death caused by the cold and lack of nursing, further demonstrated the necessity for human aid.“Jacqueline,” the third of our captive-born Chimpanzees, developed with artificial feeding, under conditions of a modern nursery. Through this individual attention and treatment given to the infant, her rate of progress was in advance, and her final physical condition was better than any of the other apes born in the gardens.Slow and very poor physical development was the result of “Sally” nursing her second infant “Noel.” This seems to prove conclusively that the chances of successfully rearing young captive-born Chimpanzees depends on the sociability and understanding between the mothers and their keepers. It also suggests the similarity to human nursing and the beneficial results of the modern nutritional and anti-deficiency disease diets.
Sarcocysts found in the musculature of necropsied mammals were dried with hexamethyldisilazane and examined by scaning electron microscopy. The object of research in this morphological study was the outer surface configuration of the cyst wall. A smooth cyst wall without villar protrusions (Sarcocystic cf. sebeki European badger, Meles meles) was compared with 10 others each with its distinctly characterized villar protrusinos. In scanning electron microscopy these resembled stumpy nails with angular heads (Sarcocystis sp./serow, Capricornis crispus), tongues (S. sp./sambar, Cervus unicolor), ears (S. sp./ wapiti, Crevus elaphus canadensis), elongated cones or clubs (S. sp./domestic horse, Equus caballus), hairs (S. sp./Mongolian gazelle, Procapra gutturosa), and molar teeth (another S. sp./Mongolian gazelle). This study revealed that what appeared in light microscopy to be finger-like protrusions of Sarcocystis hofamanni in roe deer (Capreolus capreolus), of Sarcocystis hominis in bison (Bison bison), of Sarcocystis hirsuta in cattle (Bos taurus), and of Sarcocystis tenella in sheep (Ovis aries) were more similar to columns (S. hofmanni), straps (S. hominis), stalked polyhedrons (S. hirsuta), or cylinders (S. tenella).
The preoral ciliary organ on the base of the proboscis of Saccoglosstis cam-brensis, sp. n., is described in detail. It is in the form of a continuous band of cells bearing long cilia bounding a U-shaped groove. The surrounding epidermis, and that of the groove itself, is provided with shorter cilia. An account is given of the cytological structure of the component cells. Cells, which from their structure are thought to be sensory, are numerous in the walls of the groove.Similar organs are recorded in Saccoglossus kowaievskyi Agassiz, S. irihacensis Kapelus, Harrimania kupfferi von Willemoes-Suhm, Olossobalanus minutus Kowalevsky, Balanoglossus carnosus Willey, B. capensis Gilchrist, and Ptychodera flava Eschscholtz. The occurrence, possible function, and homology of this organ are discussed. The evidence available supports the suggestion that the preoral ciliary organ of the Enteropneusta is homologous with the preoral pit and wheel-organ of Amphioxus and with the hypophysis of the Craniata.We wish to take this opportunity of expressing our thanks to Professor J. P. Hill, F.R.S., Professor C. J. van der Horst, and Professor W. Garstang for advice and criticism. We are indebted also to Professor C. J. van der Horst for the specimens of S. inhacensis, to Professor J. H. Orton for the opportunity of examining specimens of Ptychodera sp. and Olossobalanus minutus, and to the Director of the British Museum (Natural History) and Miss Hastings for access to the collections at South Kensington. The expenses of this research were defrayed by a grant to one of us (F. W. R. B.) from the Government Grant Committee of the Royal Society, for which we wish to express our thanks.
Animals enclosed in amber often provide a unique insight into their surface structure. Such fossils of reptiles are rare and usually not extremely ancient, the earliest being no more than 40 million years (my). A recently discovered 120 my lizard from the Lower Cretaceous of Lebanon provides direct evidence that several common external features of autarchoglossan lizards had evolved by this time. Ecomorphology indicates that the lizard concerned had considerable climbing ability on open surfaces and perhaps in vegetation, and probably lived in a mesic forested environment, something supported by associated plant and invertebrate remains.
Both bisexual and hermaphrodite reproduction occurs in the Notostraca. The form of the gonads is described and the cytological cycle of ovaries and testes reported briefly.The most successful chromosome counts were made on the early spermatid nuclei, seen abundantly in smears of nearly mature tests. These counts were confirmed by chromosomes found in the testis lobes and ovaries of other animals.An account of copulation is given and methods of fertilization are discussed.
The total and bound concentration quotients (C.Q.s) developed after intraperitoneal administration of globulin preparations are considerably greater than those developed after oral administration in young rats aged 15, 20, 23 and 27 days.
Over this age range the total C.Q.s developed after intraperitoneal administration decline more sharply than those developed after oral administration, suggesting that the mechanism of protein absorption from the peritoneum becomes comparatively less efficient during this period. At 27 days of age, contrasting with earlier stages, considerable degradation of the intraperitoneally administered dose occurs.
The duodenum of unweaned 28 day old rats is capable of transmitting to the circulation large quantities of labelled globulin with apparently little degradation or selection. This ability is virtually lost by 33 days. The jejunum of unweaned 28 day old rats transmits only very small quantities of labelled globulin to the circulation, and there is considerable degradation of the injected dose.
These several factors are discussed in the general context of the postnatal transfer of passive immunity in this species.
SUMMARY1. The occurrence of an Enteropneust in Wales is described, and an account given of the environment.2. Saccoglossus cambrensis, sp. n., is distinguished by the following characters:-Coloration; relative proportion of proboscis and collar; dorsal groove running the whole length of the proboscis, with a well-marked nervous thickening beneath; large number of gill-slits (80–90 pairs); gonads beginning a t the middle of the branchial region; absence of genital ridges; absence of projecting ridges formed by the ventral longitudinal muscle bands of the trunk; four to six concentric rings distinguishable in the arrangement of the longitudinal musculature of the proboscis; large pericardium; absence of a dorsal glomerulus; proboscis skeleton not reaching beyond the middle of the collar, and little more than half-way round the buccal cavity; five epidermal zones in the collar; complete separation of right and left collar cavities; absence of a dorsal pouch of the buccal cavity; discontinuity between the tissues of the nerve cord and the epidermis of the collar, except at the ends; collar-trunk septum deflected forwards to the middle of the collar; marked ciliation of the epidermis covering the ventral nerve cord in the intestinal region; shallow ventral pharynx; broad tongues, projecting more than the septa; histological details of the oesophagus; eight to twelve intestinal pores, of which the first three to five are rudimentary; simple unlobed gonads, large size of ova, and presence of yolk-cells in the ovaries.We are greatly indebted to Professor W. M. Tattersall and to Professor C. J. van der Horst for much advice, and to the former for specimens of S. ruber. We wish to take this opportunity of expressing our thanks also to Professor J. P. Hill, F.R.S., for his advice and interest in the work; to Professor G. W. Robinson for preparing the analyses of soil given in Appendix I.; to Mr. L. H. Jackson for assistance in various ways, and to Mrs. Jackson for the drawing reproduced in PI. I.
The morphology of the mouthparts of Chloeon dipterum L. and Baetis rhodani Pictet is described and the manner of functioning of the mouthparts is interpreted on the basis of their morphology and direct observations of feeding larvae. In C. dipterum the way in which the mouthparts were used depended upon the nature of the food material. The ways in which the mouthparts of B. rhodani differ from those of C. dipterum are shown to be consistent with the overall adaptation of the former species to flowing water.
I suggest that the cuckoo's parasitic adaptations are of two kinds: ‘trickery’, which is how adult cuckoos and cuckoo eggs and chicks evade host defences, and involves adaptations that have co-evolved with host counter-adaptations, and ‘tuning’, which is how, once accepted, cuckoo egg and chick development are then attuned to host incubation and provisioning strategies, and which might not always provoke co-evolution. Cuckoo trickery involves adaptations to counter successive lines of host defence and includes: tricks for gaining access to host nests, egg trickery and chick trickery. In some cases, particular stages of host defences, and hence their corresponding cuckoo tricks, are absent. I discuss three hypotheses for this curious mixture of exquisite adaptation and apparent lack of adaptation: different defences best for different hosts, strategy blocking and time for evolution of defence portfolios. Cuckoo tuning includes adaptations involving: host choice and monitoring of host nests, efficient incubation of the cuckoo egg, efficient provisioning and protection of the cuckoo chick, and adaptations to avoid misimprinting on the wrong species. The twin hurdles of effective trickery in the face of evolving host defences and difficulties of tuning into another species' life history may together explain why obligate brood parasitism is relatively rare.