Ultrastructure,Behavior, and Algal Flagellate Affinities of the Helioflagellate Ciliophrys marina,and the Classification of the Helioflagellates (Protista,Actinopoda, Heliozoea)1

Ciliophrys marina is a small marine helioflagellate, with a central nucleus, which is capable of reversibly transforming from a rapidly swimming flagellate cell with no axopodia to the structure of a heliozoan with a flagellum that beats only a few times a minute. When in the flagellate form, the flagellum acts as a tractellum due to the tubular mastigonemes found along its length. When the rapidly swimming flagellate strikes a piece of debris, the flagellum goes through a very characteristic shock-induced avoidance reaction. Similarly, when a mechanical shock is delivered to the cell in its heliozoan form, the axopodia are contracted in less than 20 msec. Both reactions are inhibited in low calcium seawater. Transformation from the heliozoan to the flagellate form is accomplished by slow retraction and absorbance of the axopodia and activation of the flagellum. Ultrastructurally, each axopodium is found to contain three microtubules which attach to the outer nuclear membrane of the central nucleus at sites that this study characterizes by electron microscopy of thin sections and freeze fracture preparations. The mitochondria have tubular cristae, each containing an intracristal filament. Finally, a taxonomic review of the helioflagellates is presented, and it is suggested that C. marina is derived from the chrysomonads. An argument is also made for classifying C. marina with the heliozoan order Actinophryida, as a recently published classification of the protozoa does.     

AUTECOLOGY AND THE FILLING OF ECOSPACE: KEY METAZOAN RADIATIONS

Abstract:  All possible combinations of six tiering positions in relation to the substratum/water interface, six motility levels and six feeding strategies define a complete theoretical ecospace of 216 potential modes of life for marine animals. The number of modes of life actually utilized specifies realized ecospace. Owing to constraints of effectiveness and efficiency the modern marine fauna utilizes only about half the potential number of modes of life, two-thirds of which (62 of 92) are utilized by animals with readily preserved, mineralized hard parts. Realized ecospace has increased markedly since the early evolution of animal ecosystems. The Ediacaran fauna utilized at most 12 modes of life, with just two practised by skeletal organisms. A total of 30 modes of life are recorded in the Early and Middle Cambrian, 19 of which were utilized by skeletal organisms. The other 11 are documented from soft-bodied animals preserved in the Chengjiang and Burgess Shale Konservat-Lagerstätten. The number of modes of life utilized by skeletal organisms increased by more than 50 per cent during the Ordovician radiation to a Late Ordovician total of 30. Between the Late Ordovician and the Recent the number of utilized modes of life has doubled again. The autecological and taxonomic diversity histories of the marine metazoa appear to be broadly parallel, and future studies of theoretical ecospace utilization should provide more detailed tests of pattern and process in the ecological history of the metazoa.     

Multiple-brooding in birds of prey: South African Black Sparrowhawks Accipiter melanoleucus extend the boundaries

Multiple-brooding (raising more than one brood of young in quick succession) occurs infrequently in raptors and is generally restricted to either smaller species with shorter nesting periods, co-operative breeders or species capable of capitalizing on conditions of prolonged food abundance whenever they occur. This paper presents the first recorded cases of multiple-brooding in the Black Sparrowhawk Accipiter melanoleucus from two distinct locales in South Africa. In the Western Cape (Cape Peninsula), four attempts to multiple-brood were recorded in four different years, involving three distinct pairs of birds, and in KwaZulu–Natal (Eshowe), three distinct pairs of Sparrowhawks successfully multiple-brooded on several occasions over a 5-year study period. These results establish the Black Sparrowhawk as one of only two relatively large, monogamous raptor species, and the only specialist bird-eating raptor, in which multiple-brooding has been recorded with any frequency . The species' capacity to thrive in human-modified environments (i.e. alien plantations) and particularly to exploit associated foraging opportunities (e.g. high densities of doves and pigeons in suburban areas) may, at least partly, account for the instances of multiple-brooding reported here. We suggest that biologists be more vigilant for cases of multiple-brooding in raptors, as it is possible that this trait is more common than originally thought and has previously been overlooked.