Chiropteran tendon locking mechanism

Rather than the usual mammalian scheme in which tendon and sheath surfaces provide as little friction as possible, the tendons and sheaths of many bats have a locking segment on the manual and pedal flexor tendon complex. This tendon locking mechanism (TLM) exists opposite the proximal phalanges of each toe and pollex of many bats. Its structure, similar to a ratchet mechanism, assists bats in hanging with little muscular effort. The third digit of the pelvic limb and the pollex of species representing 15 chiropteran families were studied to determine the presence or absence, morphology, and function of the TLM. Most of the species studied have a TLM consisting of a patch of tubercles on the ventral surface of the flexor tendon associated with the proximal phalanx of each pollex or toe. The sheath adjacent to this portion of the flexor tendon has a series of transverse folds or ridges, which, when engaged with the tubercles on the tendon, lock the tendon in place. The TLM is similar in megachiropterans and microchiropterans possessing it. The TLM is absent, however, in some of the microchiropterans studied, most notably in the phyllostomids. Since many birds have a TLM similar to that of bats, it is an excellent example of the convergent evolution of a feature brought about by similar functional pressures on birds and bats. © 1993 Wiley-Liss, Inc.     

Evolution of the digital tendon locking mechanism in bats and dermopterans: A phylogenetic perspective

A tendon locking mechanism (TLM) in the digits of the feet has been described previously only in bats and birds. In bats, this mechanism typically consists of a patch of tuberculated fibrocartilage cells on the plantar surface of the proximal flexor tendons, and a corresponding plicated portion of the adjacent flexor tendon sheath. The two components mesh together like parts of a ratchet, locking the digit in a flexed position until the mechanism is disengaged. This system apparently allows bats to hang for long periods of time with reduced muscular activity. In this study, we document for the first time the presence of a similar tendon lock in dermopterans, an occurrence that provides additional support for the hypothesis that dermopterans and bats are sister taxa. The present work also includes observations on the morphology of the digital tendon system in chiropteran species not previously examined, including members of the Craseonycteridae, Mystacinidae and Kerivoulinae. Unlike other bats that have a TLM,Craseonycteris andKerivoula have a plicated proximal tendon sheath but lack distinct tubercles on the flexor tendon. This condition may be related to small body size or may represent an evolutionary intermediate between the presence of a well-developed TLM and the complete absence of this structure. Phyllostomids apparently lack the ratchet-like TLM typical of other bats, instead exhibiting modifications of the tendon sheath that may contribute to its function as a friction lock. Consideration of the distribution of TLM structures in the context of previous phylogenetic hypotheses suggests that a ratchet-type tendon lock was lost and reexpressed at least once and perhaps several times within Microchiroptera. The friction lock is an autapomorphy of Phyllostomidae.     

The structure and probable mechanism of evolutionary formation of the foot in piciform birds (Aves: Piciformes)

The foot structure of piciform and coraciiform birds is examined in detail. Certain similarity in foot structure between woodpeckers and woodhoopoes is shown and provides the basis for the model of the evolutionary formation of the zygodactyl foot. It is shown that African mousebirds and the Madagascan Leptosomus discolor are probably the closest relatives of piciforms. A brief review of fossil groups presumably belonging to the piciform stem is provided.     

The automating skeletal and muscular mechanisms of the avian wing (Aves)

The avian wing possesses the ability to synchronize flexion or extension of the elbow and wrist joints automatically. Skeletal and muscular mechanisms are involved in generating this phenomenon. The drawing-parallels action of the radius and ulna coordinates the movements of the forearm with the carpus. Movement of the radius along the length of the forearm isnot dependent on the shape disparity between the dorsal and ventral condyles of the humerus, nor is it generated by the shape of the dorsal condyle itself. Instead, shifting of the radius toward the wrist occurs during humeroulnar flexion when the radius, being pushed by muscles toward the ulna, is deflected off theIncisura radialis toward the wrist. Movement of the radius toward the elbow occurs during the latter stages of humeroulnar extension when, as the dorsal condyle of the humerus and the articular surface of the ulna's dorsal cup roll apart, the radius gets pulled by the humerus and its ligaments away from the wrist. Synchronization of the forearm with the manus is accomplished by twojoint muscles and tendons.M. extensor metacarpi radialis and the propatagial tendons act to extend the manus in unison with the forearm, whileM. extensor metacarpi ulnaris helps these limb segments flex simultaneously.M. flexor carpi ulnaris, in collaboration with the drawing-parallels mechanisms, flexes the carpus automatically when the elbow is flexed, thereby circumducting the manus from the plane of the wing toward the body. In a living bird, these skeletal and muscular coordinating mechanisms may function to automate the internal kinematics of the wing during flapping flight. A mechanized wing may also greatly facilitate the initial flight of fledgling birds. The coordinating mechanisms of the wing can be detected in a bird's osteology, thereby providing researchers with a new avenue by which to gauge the flight capabilities of avian fossil taxa.     

The locking loop tendon suture.

The locking loop tendon suture is suggested as an effective method for suturing tendons where tension is likely during the early post-operative period. The relationship of the intratendinous parts of the suture to each other is critical to the resultant tensile strength. Experimental work has confirmed its strength and its lack of interference with the intrinsic vasculature of the tendons. Our results from this clinical repair of 72 tendons by this method have been better, in general, than we obtained with other currently popular methods.     

Flexibility of the drinking mechanism in adult chickens (Gallus gallus) (Aves)

Summary Drinking was studied in adult chickens by cinematography and radiography. Three subsequent behavioral phases occur. (1) Water is transported from the water box into the oropharynx when the beak is immersed. Then delicately tuned cyclic motion patterns of beaks, tongue, and larynx transport water by capillarity, squeezing, and suction. (2) During the elevation of the head the tongue is elevated and the larynx is depressed to keep the water in the pharynx against the gravitational and centrifugal forces that result from the upward swing of the head. (3) During the tip up phase gravity transports the water to the esophagus, while the adhering water is pushed and squeezed caudad by tongue and larynx movements. Flexibility in the adult drinking mechanism was analyzed by comparing the drinking of normal and beak-trimmed chickens under normal drinking conditions, as well as while drinking small drops. Three modes of behavioral flexibility were discussed: conservative, regressive, and progressive flexibility. Most behavioral elements of the modal action pattern in drinking are so flexible that a chicken can reorganize the movement patterns of jaws, tongue, larynx, and head to adapt the mechanism to external (drop drinking) or internal (beak-trimming) changes. However, in drop drinking, the normal chicken relies upon a regressive takeover by an ontogenetically earlier developed pattern in the craniocervical motion system. Presence of the observed progressive flexibility in lingual and cervical motion patterns is shown to be a precondition for the avian drinking mechanism to keep up with dominant evolutionary changes in feeding mechanisms.     

Construction of the avian skull,as demonstrated by direct magnifying microfocal radiography (Aves)

Summary The new microfocus X-ray technique works with X-ray sources smaller than 10 m in diameter. Thus, in contrast to conventional X-ray systems, it is possible to obtain direct magnifications with high spatial resolution, i.e., well-focused radiographs with better contrast and depth of focus. In this connection, specific construction principles of the avian skull are elucidated, comparing several bird groups. The typical pneumatization effects are demonstrated, as are other biologically important anatomical features, in particular those of the bills/beaks as related to mechanical demands.     

Ancient differentiation in the single-island avian radiation of endemic Hispaniolan chat-tanagers (Aves: Calyptophilus)

The simple geographic structure of island systems often makes them tractable for studies of the patterns and processes of biological diversification. The Calyptophilus chat-tanagers of Hispaniola are of general evolutionary interest because their multiple lineages might have arisen on a single island, of conservation concern because several isolated populations are nearly extinct, and taxonomically ambiguous because they have been variously lumped or split into one to four species. To explore the context of diversification of the seven extant Calyptophilus populations, we conducted a multilocus coalescent analysis based on sequences of mitochondrial ND2 and three nuclear intron loci. We then compared patterns of phylogeographic genetic variation with the morphological differences that distinguish these populations. Mitochondrial haplotypes formed two reciprocally monophyletic groups separated by a large magnitude of nucleotide divergence. Intron structure largely paralleled the geographic grouping pattern of the mitochondrial DNA (mtDNA), but these groups were only reciprocally monophyletic at one of the three introns. Also, the magnitude of between-group divergence was much lower in the introns than mtDNA genealogies. Multilocus coalescent analyses inferred a nonzero divergence time between these two major geographic groups, but suggested that they have experienced a low level of gene flow. All four markers showed substantial allele sharing within each of the two groups, demonstrating that many now separated montane populations do not have long histories of isolation. Considered in concert, our multilocus phylogeographic reconstructions support the recognition of two species within the Calyptophilus complex, and raise the possibility that these taxa differentiated prior to the fusion of the two palaeo-islands that form present-day Hispaniola.     

Evolution and functional significance of tendon ossification in woodcreepers (Aves: Passeriformes: Dendrocolaptinae)

The woodcreepers, a clade of scansorial, neotropical birds, are distinctive among passerines in having extensive tendon ossification. Dissection of 42 of the 50 species indicates that such ossification in the hindlimb is limited almost entirely to tendons of insertion of the crural muscles. Most crural muscles have ossifications, and in all but one the ossified tendons are long and thin. Preliminary dissection revealed a similar pattern among ossified wing tendons. Phylogenetic analysis suggests that extensive tendon ossification is a synapomorphy of the woodcreepers. The species of Dendrocincla, which form a clade, show secondary reduction of ossification in some tendons, which may be correlated with increased intraspecific variation and with an expansion of foraging habits and postures to include nonscansorial behaviors. In contrast, the larger woodcreepers, other than Drymornis bridgesii and Nasica longirostris, form a clade with virtually no loss in ossification or evidence of intraspecific variation, even in large series of two species. Phylogenetic losses do not occur for the primary flexor of the ankle (M. tibialis cranialis), whereas two extensors (Mm. fibularis longus and gastrocnemius pars lateralis) show a complex pattern of derivation and loss. Previous biomechanical studies demonstrate that ossification increases the stiffness of tendons, making them stretch less under a given force. These structural and phylogenetic patterns are consistent with the view that hindlimb tendon ossification in woodcreepers is an adaptation to resist increased forces that act to extend the limb during vertical climbing. © 1993 Wiley-Liss, Inc.     

The species of Ardeicola (Phthiraptera) on Threskiornis (Aves)

The species of Ardeicola parasitic on the Ibis genus Threskiornis are reviewed-clayae Brelih, freemani sp.n., ibis Le Souef & Bullen, indicus Brelih, intermedia sp.n., nippon Hajela & Tandan-and a key for their identification is presented. Notes on the affinities of the species and a discussion on the distribution of Ardeicola on Threskiornis are included.     

The species of Ibidoecus (Phthiraptera) on Threskiornis (Aves)

The species of Ibidoecus parasitic on the Ibis genus Threskiornis are reviewed-clausus (Giebel), dianae Tandan, insularis sp.n., tandani sp.n., threskiornis Bedford-and a key for their identification presented. The host and geographical distribution of the phthirapteran parasites of this genus are discussed.     

Speciation in an avian complex endemic to the mountains of Middle America (Ergaticus, Aves: Parulidae)

The implementation of the phylogeographic approach for the study of biodiversity is critical in poorly sampled regions like the montane systems of Middle America, as complex evolutionary histories often result in the presence of independent lineages not properly considered by traditional taxonomy. Herein we sequenced 2370 bp of mtDNA (ND2, cyt b and ATPase) from 81 individuals of Ergaticus, a complex of birds endemic to the montane forests of Middle America. Although current taxonomy recognizes two species, the results reveal considerable genetic structure with the presence of four mtDNA lineages. Two of these lineages within Ergaticus ruber evidence the need of a revaluation of the species limits for this taxon. The general phylogeographic pattern can be explained as a consequence of relative isolation of the populations in different mountain ranges separated by low elevation barriers. Most population groups did not show signals of demographic expansion with the exception of the one corresponding to clade 1. The divergence time estimates point to the Pleistocene as an important time period for the diversification of this complex.     

A revision of the family Ciconiidae (Aves)

Behavioural and morphological characteristics of all members of the stork family are summarized. References are given to other papers where these subjects are discussed in greater detail for each group of storks. Based on the evidence now available, a revised classification is suggested (Table II) which divides the Ciconiidae into three tribes, six genera, and 17 species. The following genera (of Peters, 1931) are synonymized with other existing genera: Ibis, Sphenorhynchus, Dissoura, Euxenura , and Xenorhynchus. It is further suggested that Scopus should be placed in a suborder of its own and that Balaeniceps be placed in a monotypic family adjacent to the Ciconiidae, pending further study.     

The Phthiraptera (Insecta) parasitic on flamingoes (Phoenicopteridae: Aves)

The phthirapteran parasites occurring on the flamingoes are listed and their distribution discussed. New species of Anaticola and Anatoecus are described.     

The craniofacial air sac system of Mesozoic birds (Aves)

Birds are characterized by pneumatization of their skeletons by epithelial diverticula from larger, air—filled cavities. The diverticula—or 'air sacs'—that invade the postcranium result from outgrowths of the lungs; postcranial pneumaticity has been very well studied. Much more poorly understood are the air sacs that pneumatize the skull. Study of craniofacial pneumaticity in modern birds (Neornithes) indicates the presence of two separate systems: nasal pneumaticity and tympanic pneumaticity. The lacrimal and maxillary bones are pneumatized by diverticula of the main paranasal cavity, the antorbital sinus. There are five tympanic diverticula in neornithines that pneumatic the quadrate, articulare and the bones of the braincase. The pneumatic features of the following six genera of Mesozoic birds are examined: Archaeopteryx, Enaliornis, Baptornis, Parahesperornis, Hesperornis and Ichthyornis. Despite the 'archaic' aspect of most of these birds, many of the pneumatic features of neornithines are found in Mesozoic birds and are considered primitive for Aves. The phylogenetic levels at which most of the avian pneumatic features arose within Archosauria are uncertain. Until the phylogenetic levels at which homologous pneumatic features arose are determined, it is unwise to use most pneumatic characters in the discussion of avian origins. Within avian phylogeny, Ornithurae and Neornithes are well–supported by pneumatic synapomorphies. There is a trend towards reduction of craniofacial pneumaticity within Hesperornithiformes. Within Neornithes, four derived pneumatic characters suggest that the Palaeognathae (ratites and tinamous) is monophyletic.     

Explosive avian radiations and multi-directional dispersal across Wallacea: evidence from the Campephagidae and other Crown Corvida (Aves)

The systematic relationships among avian families within Crown Corvida have been poorly studied so far and as such been of limited use for biogeographic interpretations. The group has its origin in Australia and is thought to have colonized Africa and the New World via Asia beginning some 35 Mya when terranes of Australian origin approached Asian landmasses. Recent detailed tectonic mapping of the origin of land masses in the region around Wallace's line have revealed a particularly complex movement of terranes over the last 20-30 Myr. Thus the biogeographic dispersal pattern of Crown Corvida is a particularly exciting case for linking vicariance and dispersal events with Earth history. Here we examine phylogenetic affinities among 72 taxa covering a broad range of genera in the basal radiations within Crown Corvida with an emphasis on Campephagidae and Pachycephalidae. Bayesian analyses of nuclear DNA sequence data identified the family Campephagidae as monophyletic but the large genus Coracina is not. Within the family Pachycephalidae the genera Pachycephala and Colluricincla are paraphyletic with respect to each other. The resulting phylogeny suggests that patterns of dispersal across Wallace's line are complex and began at least 25 Mya. We find evidence of explosive radiations and multi-directional dispersal within the last 10 Myr, and three independent long distance ocean dispersal events between Wallacea and Africa at 10-15 Mya. Furthermore, the study reveals that in the Campephagidae a complex series of dispersal events rather than vicariance is the most likely explanation for the current biogeographic pattern in the region.     

The anatomy of the middle ear of the tinamiformes (Aves: Tinamidae)

The morphology of the middle ear region including the basicranium and quadrate of tinamous is compared among ratites and flying birds belonging to the Procellariiformes, Sphenisciformes, Pelecaniformes, and Ciconiiforms. The middle ears of tinamous and ratites share a number of important characters including absence of a separate foramen for the glossopharyngeal nerve; eustachian tube, carotid artery, and stapedial artery encased in bone; and a metotic process with vascular canals or notches. Outgroup analysis confirms these characters as synapomorphies. These data support the position that the Tinami and Ratiti form a monophyletic assemblage.     

Global diversity of freshwater birds (Aves)

Among the 10,000 birds species living on earth, 5% (e.g., 560) need imperatively freshwater habitat in order to satisfy at least one of their life history traits. About 11 completed families could even disappear if their wetland habitat left. About 10% (58) of these can be considered as endemic. Africa contains the biggest number of endemic (20) and more precisely Madagascar. Among freshwater species, ducks and geese have a major importance in human activities in northern hemisphere related to food resources (hunting) or birding. Guest editors: E.V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment