Academic literature on the topic 'Ornithorhynchus anatinus'

A reconstruction of the skull, dentary and dentition of the middle Miocene ornithorhynchid Obdurodon dicksoni has been made possible by acquisition of nearly complete cranial and dental material. Access to new anatomical work on the living platypus, Ornithorhynchus anatinus , and the present comparative study of the cranial foramina of Ob. dicksoni and Or. anatinus have provided new insights into the evolution of the ornithorhynchid skull. The hypertrophied bill in Ob. dicksoni is seen here as possibly apomorphic, although evidence from ontogenetic studies of Or. anatinus suggests that the basic form of the bill in Ob. dicksoni (where the rostral crura meet at the midline) may be ancestral to the form of the bill in Or. anatinus (where the rostral crura meet at the midline in the embryonic platypus but diverge in the adult). Differences in the relative positions of cranial structures, and in the relationships of certain cranial foramina, indicate that the cranium may have become secondarily shortened in Or. anatinus , possibly evolving from a more elongate skull type such as that of Ob. dicksoni . The plesiomorphic dentary of Ob. dicksoni , with well–developed coronoid and angular processes, contrasts with the dentary of Or. anatinus , in which the processes are almost vestigial, as well as with the dentary of the late Oligocene, congeneric Ob. insignis , in which the angular process appears to be reduced (the coronoid process is missing). In this regard the dentary of Ob. insignis seems to be morphologically closer to Or. anatinus than is the dentary of the younger Ob. dicksoni . Phylogenetic conclusions differ from previous analyses in viewing the northern Australian Ob. dicksoni as possibly derived in possessing a hypertrophied bill and dorsoventrally flattened skull and dentary, perhaps being a specialized branch of the Obdurodon line rather than ancestral to species of Ornithorhynchus . The presence of functional teeth and the robust, flattened skull and dentary in Ob. dicksoni argue for differences in diet and lifestyle between this extinct ornithorhynchid and the living Ornithorhynchus .

Ixodes ornithorhynchi is one of Australia’s most cryptic tick species and is found only on the platypus (Ornithorhynchus anatinus). The first cytochrome c oxidase subunit 1 (CO1) sequences for this species are presented to facilitate molecular identification and conservation of both this tick species and its host.

This paper reviews present understanding of the evolution of the ornithorhynchids. An ancient family within the mammalian order Monotremata. Ornithorhynchidae today is represented only by the living platypus Ornithorhynchus analinus but has a history that probably predates the Tertiary and a past distribution that spanned at least three continents. Analysis of the palaeontological record has focused on the distinctive ornithorhynchid dentition, which in species of Monotrematum and Obdurodon was probably functional throughout life. The retention of functional dentition in concert with the great age of Ornithorhynchidae gives the platypus family a much larger role in analysis of the biogeographic and phylogenetic history of the monotremes than is given to the more specialised, edentate tachyglossids, or echidnas. A complete ornithorhynchid skull, recovered from Miocene deposits at Riversleigh in north-western Queensland, has allowed comparison between the cranium of a generally more plesiomorphic platypus and that of the living Or. anatinus, a study that answers some of the morphological questions posed by this enigmatic group while raising others. This review concludes with a discussion of the biogeography and palaeoecology of the family.

Platypuses (Ornithorhynchus anatinus) and other monotremes occupy an important position as an early offshoot from the evolutionary lineage leading from reptiles to mammals. One of the most intriguing characteristics of these mammals is that the males produce venom during the mating season. O. anatinus venom contains defensin-like peptide, C-type natriuretic peptide and nerve growth factor, as well as other unidentified fractions. These components of O. anatinus venom display similarity to components of the venom of other species such as sea anemones, snakes and shrews. Here we review available literature on O. anatinus venom and venom in other species. Further research into O. anatinus venom will offer some insight into the evolution and functions of venom components.

Maternal care in platypuses has never been rigorously studied due to the difficulty in locating and accessing nesting burrows. Here we describe the maternal behaviour of a captive female platypus and the growth and development of her offspring over 11 breeding seasons. We located a nesting burrow and inserted a camera to record the activity and behaviour of the female and her offspring. We also measured the female’s food intake during lactation. The ages of the offspring were assigned to developmental milestones including opening of the eyes and development of pelage. Twins (n=4) were left alone for periods longer than 24h by the mother at an earlier age than single nestlings (n=2). The dietary energy intake of the breeding female was more than double that of non-lactating females in the last month of lactation, indicating the large energy requirements of milk production. The mean age of young at emergence from the burrow was 128±1 days and in 60% of nestlings emergence occurred after weaning. This suggests a rapid transition from a completely milk-based diet to a diet of aquatic macroinvertebrates. The techniques we developed have allowed us to study maternal care in platypuses and the development of nestlings, both of which were previously only poorly understood.

Body lengths and bill dimensions were recorded from 26 nestling platypuses from various museum collections and from published records. In nestling platypuses less than 3 months old bill width was greater than length, but this was reversed in older nestlings and in juveniles of both sexes. Nestlings grew from a body length of approximately 5 cm (~ 1 week of age) to 34 cm (14-17 weeks). Comparative data on growth of captive nestlings while sparse, supported the general trends seen in nestlings collected for this study. Body lengths and weights were also recorded from 219 (113 female; 106 male) platypuses which had been captured initially as juveniles in the upper Shoalhaven River. New South Wales. Recaptures resulted in 358 separate (215 female; 143 male) records from these animals. At emergence from the breeding burrow in January/February, juvenile males were significantly larger than females. Juvenile males had a mean body length of 41.2 (S.D.± 2.8) and females 37.5 (S.D.± 2.0) cm respectively (p<O.OOI) and mean body weights of recently emerged juvenile males and females were 779 (S.D.± 127) and 588 (S.D.± 88) g (p<O.OOI). Mean lengths and weights of the emerged juveniles were significantly smaller (p<O.OOI) than those sampled as adults (weight 65-70%; length 83-87%). The wide variation in weights and lengths of juvenile individuals of both sexes at first capture may be due to different times of emergence and/or the effects of different litter sizes.

In this work, behavioural field studies and metabolic studies in the laboratory were conducted to elucidate the extent of adaptation of the platypus Ornithorhynchus anatinus to its highly specialised semiaquatic lifestyle. Energy requirements of platypuses foraging, resting and walking were measured in a swim tank and on a conventional treadmill using flow-through respirometry. Foraging behaviour and activity pattern of platypuses in the wild were investigated at a sub-alpine Tasmanian lake where individuals were equipped with combined data-logger-transmitter packages measuring foraging activity or dive depth and ambient temperature. Energy requirements while foraging in the laboratory were found to depend on water temperature, body mass and dive duration and averaged 8.48 W kg-1. Mean rate for subsurface swimming was 6.71 W kg-1. Minimum cost of transport for subsurface swimming platypuses was 1.85 J N-1m-1 at a speed of 0.4 m s-1. The metabolic rate of platypuses resting on the water surface was 3.91 W kg-1 while minimal RMR on land was 2.08 W kg-1. The metabolic rate for walking was 8.80 and 10.56 W kg-1 at speeds of 0.2 and 0.3 m s-1, respectively. Minimal cost of transport for walking was predicted to be 2.13 J N-1m-1 at a speed of 1.7 m s-1. A formula was derived, which allows prediction of power requirements of platypuses in the wild from measurements of body mass, dive duration and water temperature. Activity patterns of platypuses in the wild were highly variable. Forty percent of the platypuses studied showed patterns, which deviated considerably from the nocturnal pattern generally reported for the species. Some animals showed diurnal rhythms while others temporarily followed the lunar cycle. Foraging trips lasted for an average of 12.4 h of continuous foraging activity per day (maximum: 29.8 hours). There were significant differences in diving behaviour between sexes and seasons. Activity levels were highest between August and November and lowest in January. While foraging, platypuses followed a model of optimised recovery time, the optimal breathing theory. Mean dive duration was 31.3 seconds with 72 % Energetics and foraging behaviour of the platypus 6 of all dives lasting between 18 and 40 seconds. Mean surface duration was 10.1 seconds. Mean dive depth was 1.28 m with a maximum of 8.77 m. Up to 1600 dives per foraging trip with a mean of 75 dives per hour were performed. Only 15 % of all dives were found to exceed the estimated aerobic dive limit of 40 seconds indicating mainly aerobic diving in the species. Total bottom duration per day was proposed as a useful indicator of foraging efficiency and hence habitat quality in the species. In contrast to observations made earlier in rivers, temporal separation was found to play a vital role for social organisation of platypuses in the lake system that was investigated. It is suggested that high intra-specific competition as well as limited burrow sites and a limited number of at the same time highly productive foraging locations were responsible for this observation. Mean burrow temperature in the wild was 17.5 and 14.2ºC in summer and winter, respectively, and was fairly constant over the platypus's resting period. In the cooler months, burrow temperature was up to 18ºC higher than ambient air temperature. By combining both field and laboratory data, a time-energy budget for the platypus was created. Mean field metabolic rate was 684 kJ kg-1 day-1 and was significantly higher in the winter months. Mean food requirement was 132 g fresh matter kg-1 day-1. Feeding rates were 68 % higher in winter than in summer. While platypuses in the swim tank were found to expend energy at only half the rate of semiaquatic eutherians of comparable body size, cost of transport at optimal speed as well as field metabolic rates were in line with findings for eutherians. These patterns suggest that locomotor efficiency of semiaquatic mammals might have reached a limit for energetic optimisation. The semiaquatic lifestyle seems to pose comparable energetic hurdles for mammals regardless of their phylogenetic origin.

The evolutionary history of mammals, when including extinct taxa, is mainly reconstructed using tooth morphology and employs terminology based on non-monotreme mammals. Although adult monotremes are edentulous, juvenile platypuses have teeth that can be compared with extinct monotremes, but terminology can be a barrier to efficient comparison to non-monotreme mammals. Deciduous teeth and thickened epithelial plates of the extant platypus, Ornithorhynchus anatinus, are sparsely figured in the literature. New imagery of those teeth and plates from high-resolution x-ray computed tomography and scanning electron microscopy contribute to the understanding of mammal evolution and the unique morphology of platypus teeth. The teeth of the juveniles are highly variable, but early-forming features (major cusps and transverse valleys) are stable enough for comparison. Transverse lophs on monotreme teeth contain complexity not reflected in cusps alone, unlike therian mammals. These differences reinforce the need for caution when applying dental terminology that originally was produced for therian mammals. New imagery highlights potential phylogenetically informative morphology in the pulp cavity and roots. As the roots of the juvenile teeth degenerate, the epithelium below the teeth thickens into epithelial plates. Structures in the epithelial plates are broadly similar to those found in the keratin plates. New images of the epithelial plates offer insight into a series of tubes concentrated under the juvenile teeth. The tubes are a continuous conduit to the plate surface and may serve a sensory function or result from the ever-growing nature of the epithelial plate.
text