The functional significance of multiple nest-building in the Australian Reed Warbler Acrocephalus australis

The vast majority of bird species build a nest in which to breed. Some species build more than one nest, but the function of most multiple nest-building remains unclear. Here we describe the unusual nest-building behaviour of the Australian Reed Warbler Acrocephalus australis , and test experimentally the hypotheses that multiple nest-building is related to individual condition or territory quality, and plays a role in mate assessment. Australian Reed Warblers built two types of nest structures: 'type I' nests, which were used for eggs and nestlings, and 'type II' nests, which were structurally distinct from type I nests, did not support eggs, nestlings or adults and were not essential for successful breeding. The number of type II nests built in each territory varied. Type II nests were only built before breeding had commenced in a territory and females were not observed participating in their construction, supporting a role in female mate choice. Birds provided with supplementary food built significantly more type II nests than control birds. However, supplementary-fed birds did not have greater pairing success, and the addition of further type II nests to territories did not increase the pairing rate or type II nest construction in those territories. There was no relationship between the presence of type II nests and either reproductive success or likelihood of nest predation. We discuss the implications of these results in light of previous suggestions regarding the function of multiple nest-building in birds.     

Phosphorylation regulated ion-binding is a property shared by the acidic subclass dehydrins

Dehydrins are a family of proteins that accumulate in response to abiotic stresses. Little is known about the biochemical functions of these proteins. It is known that the Arabidopsis dehydrin, ERD14, is activated by phosphorylation to bind calcium and other ions. To begin to categorize the Arabidopsis dehydrins into functional families, we determined whether representative members of the dehydrin sub families share the properties of ERD14. When phosphorylated in vitro with casein kinase II; recombinant COR47, and ERD10 (and ERD14) become activated to bind calcium. ERD14 exhibited the highest calcium-binding activity followed by ERD10 and COR47. These dehydrins, when isolated from cold-treated Arabidopsis plants were also shown to have phosphorylation-dependent, calcium-binding activity. RAB18 showed very little calcium binding activity, even though it was phosphorylated by casein kinase II. XERO2 was not phosphorylated with CKII and did not bind calcium. Competition studies suggest that other divalent cations may bind to the dehydrins COR47, ERD10, and ERD14. Utilizing matrix-assisted laser desorption ionization – time of flight mass spectroscopy (MALDI-TOF), we determined that the poly serine region located in all three calcium-binding family members (COR47, ERD10, and ERD14) is the most likely phosphorylation site responsible for the activation of calcium binding. These results are consistent with a distinct biochemical function for the acidic subclass of dehydrins (COR47, ERD10, and ERD14) as ion (calcium)-interacting proteins.     

THE MORPHOLOGY OF HYOLITHIDS AND ITS FUNCTIONAL IMPLICATIONS

Abstract:  The exceptionally preserved hyolithids Gompholites striatulus , Maxilites robustus , Maxilites snajdri and Maxilites sp. are described with particular emphasis on helen and muscle scar morphology. These two aspects of hyolithid morphology have remained controversial. In life position, each helen curved ventrally. When the operculum closed the aperture of the conch, each helen was locked at the commissure slit with its dorsal edge tilted forward. Inside the conch, it was held in the dorsal apertural plane and clear of the inner surface of the operculum. Previously unidentified muscle scars are described from both the operculum and the conch. Dorsal scars on the conch aperture held muscles directed to the operculum. Comparative study of the muscle insertion pattern indicates that hyolithids did not have serially arranged muscles and that all hyolithids may have had a common skeleto-muscular system. The arrangement of the muscle scars with respect to the helens suggests that the latter were capable of relatively complex movements and could have been used to propel the organism over the substrate. The general morphology and orientation of the helens suggests that in addition they functioned to stabilize the organism on the sea-floor.     

Properties of Mg2+-Stimulated and (Na++K+)-Activated Adenosine-5'-Triphosphatase from Sugar Beet Cotyledons

Sugar beet leaf homogenate contains Mg²⁺-stimulated ATPase activity with the highest specific activity in the 25,000–30,000 ×g-fraction. This fraction also has (Na⁺+ K⁺)-activated ATPase activity. Both activities have two pH optima, one stable at pH 7.9 and one variable at lower pH. When optimal conditions of Na⁺ and K⁺ were tested with 64 combinations of these ions, at least two mountains of activity were revealed. The (Na⁺+ K⁺)-ATPase had a high specificity for ATP. It had lost about 50% of its original activity after 56 days of storage at ?85°C. The activity drop was most pronounced at high ionic concentrations in the test medium. The (Na⁺+ K⁺)-ATPase shows four peaks of activity when tested at constant ionic strength. The idea is put forward that the four peaks reflect two ATPases, one in the tonoplast and one in the plasmalemma, which undergo conformational changes in relation to the ionic milieu.     

AQUATIC BIRDS FROM THE UPPER CRETACEOUS (LOWER CAMPANIAN) OF SWEDEN AND THE BIOLOGY AND DISTRIBUTION OF HESPERORNITHIFORMS

Abstract:  Isolated skeletal elements of three hesperornithiform taxa are recorded from marine strata of latest early Campanian ( sensu germanico ) age in the Kristianstad Basin, southern Sweden. The material comprises Hesperornis rossicus Nessov and Yarkov, one of the largest Mesozoic aquatic birds known to date, Hesperornis sp. and Baptornis sp. The holotype (a dorsal vertebra) of Parascaniornis stensioei Lambrecht is re-examined, and the nominal species is here considered as a nomen dubium because no diagnostic features can be found that separate the type from dorsals of Baptornis advenus . The distribution and palaeobiology of hesperornithiforms are reviewed.     

Breeding strategies of Antarctic Petrels Thalassoica antarctica and Southern Fulmars Fulmarus glacialoides in the high Antarctic and implications for reproductive success

Breeding strategies of two closely related fulmarine petrels were studied on Ardery Island, on the continental coast of East Antarctica, where short summers are expected to narrow the time-window for reproduction. Both species had a similar breeding period (97 days from laying to fledging) but Antarctic Petrels Thalassoica antarctica bred up to 16 days earlier than Southern Fulmars. During the pre-laying exodus, all Antarctic Petrels deserted the colony, whereas some Southern Fulmars Fulmarus glacialoides remained. Antarctic Petrels exhibited stronger synchronization in breeding, made longer foraging trips and spent less time guarding their chicks than Southern Fulmars. Overall breeding success of both species was similar but failures of Antarctic Petrels were concentrated in the early egg-phase and after hatching, when parents ceased guarding. Southern Fulmars lost eggs and chicks later in the breeding cycle and so wasted more parental investment in failed breeding attempts. Different breeding strategies may be imposed by flight characteristics; Southern Fulmars are less capable of crossing large expanses of pack ice and need to delay breeding until the sea ice retreats and breaks up. However, due to the short summer they risk chick failure when weather conditions deteriorate late in the season.     

ONTOGENETIC NICHE SHIFT IN THE BRACHIOPOD TEREBRATALIA TRANSVERSA: RELATIONSHIP BETWEEN THE LOSS OF ROTATION ABILITY AND ALLOMETRIC GROWTH

Abstract: Many articulated brachiopods experience marked life habit variations during ontogeny because they experience their fluid environment at successively higher Reynolds numbers, and they can change the configuration of their inhalant and exhalant flows as body size increases. We show that the extant brachiopod Terebratalia transversa undergoes a substantial ontogenetic change in reorientation governed by rotation around the pedicle. T. transversa′s reorientation angle (maximum ability to rotate on the pedicle) decreases during ontogeny, from 180 degrees in juveniles to 10–20 degrees in individuals exceeding 5 mm, to complete cessation of rotation in individuals larger than 10 mm. Rotation ability is substantially reduced after T. transversa achieves the adult lophophore configuration and preferred orientation with respect to ambient water currents at a length of 2.5–5 mm. We hypothesize that the rotation angle of T. transversa is determined mainly by the position of ventral and dorsal points of attachment of dorsal pedicle muscles relative to the pedicle. T. transversa shows a close correlation between the ontogenetic change in reorientation angle and ontogeny of morphological traits that are related to points of attachment of dorsal pedicle muscles, although other morphological features can also limit rotation in the adult stage. The major morphological change in cardinalia shape and the observed reduction of rotation affect individuals 2.5–10 mm in length. The position of ventral insertions of dorsal pedicle muscles remains constant, but contraction of dorsal pedicle muscles is functionally handicapped because dorsal insertions shift away from the valve midline, rise above the dorsal valve floor, and become limited by a wide cardinal process early in ontogeny (<5 mm). The rate of increase of cardinal process width and of distance between dorsal pedicle muscle scars substantially decreases in the subadult stage (5–10 mm), and most of the cardinalia shell traits grow nearly isometrically in the adult stage (>10 mm). T. transversa attains smaller shell length in crevices than on exposed substrates. The proportion of small‐sized individuals and population density is lower on exposed substrates than in crevices, indicating higher juvenile mortality on substrates prone to grazing and physical disturbance. The loss of reorientation ability can be a consequence of morphological changes that strengthen substrate attachment and maximize protection against biotic or physical disturbance (1) by minimizing torques around the pedicle axis and/or (2) by shifting energy investments into attachment strength at the expense of the cost involved in reorientation.