Biogeography of the octocorallian coelenterate fauna of southern Africa

The geographical and bathymetric distribution of southern African octocorals is analysed. Of the over 200 estimated species of regional octocorals, 81 confirmed and adequately described species are studied using a radial sector method. Two primary faunal components are recognized–endemic (53.3% of the fauna by numbers of species) and Indo-Pacific (39.4%). An Atlantic component contributes only minimally (about 1.7%), while the remaining fauna is made up of cosmopolites (2.8%) and scattered species (2.8%). A subantarctic component is not evident for the present-day, although evidence for previous contact is presented. A sister-group analysis using genera as a guide to sister species, shows the biogeographic affinities for the present-day fauna as a whole to be 45% Indo-Pacific, 31% cosmopolitan, 10% endemic, 10% Atlantic and 4% southern oceans (subantarctic). Applying the same method to only those genera with endemic species shows the affinities of the present-day endemic fauna to be 27.5% Indo-Pacific, 27.5% endemic, 24% cosmopolitan, 14% Atlantic and 7% subantarctic. Clearly defined boundaries for west, south, and east coast faunas (as recognized by previous authors in describing various intertidal faunas) are found not be present with regard to the octocoral fauna (largely due to its overwhelmingly subtidal nature). Instead two primary zoogeographic provinces are recognized–the Cape Endemic Province (extending from Liideritz to Inhaca Island) and the south-western fringe of the Indo-Pacific Province from East London north-eastwards. An overlap zone between these two is recognized between East London and Inhaca Island, with the region in the vicinity of Richards Bay having an essentially evenly mixed fauna (roughly 50% Cape Endemic Province and 50% Indo-Pacific). Of the 84 octocoral genera recorded for the region, seven (or 8.3%) are endemic, and of these, five are monotypic while two are ditypic. The fauna is shown to be predominantly sublittoral (about 95% by numbers of species), the shallow sublittoral (< 100 m in depth) being the region with highest species richness. Pennatulaceans are eurybathic (intertidal to 4756 m) and clearly show a high proportion of cosmopolites (20% of presently identified species). Soft corals are stenobathic and restricted to the intertidal, continental shelf and uppermost portion of the continental slope (<500m), while gorgonians are intermediate in depth distributon (intertidal to 1200 m). No cosmopolitan alcyonaceans are presently recorded. The centre of the Cape Endemic Province is the Agulhas Bank–an extensive region of shallow continential shelf (< 200 m in depth) between Cape Town and East London. Two regions of octocoral radiation for southern Africa are postulated–the Agulhas Bank and the western Indian Ocean.     

The zygote and proembryo of alfalfa: quantitative,three-dimensional analysis and implications for biparental plastid inheritance

Summary Genetic studies have demonstrated biparental inheritance of plastids in alfalfa. The ratio of paternal to maternal plastids in the progeny varies according to the genotypes of the parents, which can be classified as strong or weak transmitters of plastids. Previous cytological investigations of generative cells and male gametes have provided no consistent explanation for plastid inheritance patterns among genotypes. However, plastids in the mature egg cells of a strong female genotype (6–4) were found to be more numerous and larger than in mature eggs of a weak female genotype (CUF-B), and the plastids in 6–4 eggs are positioned equally around the nucleus. In CUF-B, the majority of plastids are positioned below (toward the micropyle) the mid level of the nucleus, which is the future division plane of the zygote. Since only the apical portion of the zygote produces the embryo proper, plastids in the basal portion were predicted to become included in the suspensor cells and not be inherited. In the present study, we examined zygotes and a two-celled proembryo from a cross between CUF-B and a strong male genotype (301), a cross that results in over 90% of the progeny possessing paternal plastids only. Our results indicate that the distribution of plastids observed in the CUF-B egg cell is maintained through the first division of the zygote. Further, paternal plastids are similarly distributed; however, within the apical portion of the zygote and in the apical cell of the two-celled proembryo, the number of paternal plastids is typically much greater than the number of maternal plastids. These findings suggest that maternal and paternal plastid distribution within the zygote is a significant factor determining the inheritance of maternal and paternal plastids in alfalfa.     

Review of Colombian Conchostraca (Crustacea) — ecological aspects and life cycles — families Lynceidae,Limnadiidae, Leptestheriidae and Metalimnadiidae

This study gives an overview of our current knowledge of the ecology and distribution patterns of Colombian conchostracans. Colombian euphyllopods are generally restricted to the warm tropical lowlands. OnlyCyclestheria hislopi can be found year-round in larger semipermanent waters and living sympatrically with abundant predators, such as planktivorous fish. The other conchostracans are restricted to the typical habitat of temporary waters.Eulimnadia magadalenensis is especially adapted to very short-term temporary ponds in relatively arid zones andE. colombiensis prefers somewhat cooler ponds of a longer duration. The two species can be found sympatrically in intermediate climatic conditions. A third form,Eulimnadia cf. geayi cohabits with the two other species in the lower Magdalena Valley, its ecological role is not clear.Limnadia orinoquiensis is the selvatic substitute of the open savannah conchostracan fauna (mainlyEulimnadia forms) living in pools in forest clearings in the vicinity of the Upper Orinoco.Four species of Lynceidae were found, twoLynceus and twoParalimnetis. Their distribution patterns are not yet clear, they prefer smaller temporary ponds of moderated temperatures. Two undescribed species ofLeptestheria were found, one restricted to the banks of the Orinoco and the other to one locality in the upper Magdalena Valley, living in ponds with a muddy bottom.Metalimnadia serratura was found in special rock pools of the Guiana Shield in the vicinity of the Orinoco, cohabiting with several other conchostracan species, with differential adaptations to very high water temperatures.     

Redescription ofDiaphanosoma volzi Stingelin, 1905 (Crustacea: Daphniiformes: Sididae) with remarks on comparative morphology,biology and geographical distribution

The rareDiaphanosoma volzi Stingelin, long confused withD. sarsi Richard andD. celebensis Stingelin, is redescribed, based on extensive material of parthenogenetic and gamogenetic females and males from Thailand. Indonesia, Malaysia, Philippines, India, Australia and Sudan, and a study of intra- and interpopulation morphological variability. Compared with otherDiaphanosoma species, it shows the greatest degree of oligomerization and specialization. It is widely distributed in the tropics and subtropics of the Eastern hemisphere, and mostly occurs in shallow, vegetated habitats.     

Habitat and distribution of perforatella rubiginosa (Gastropoda,Pulmonata) in the freshwater tidal region of the Scheldt estuary,Belgium

The amphibious land-molluse,Perforatella rubiginosa, is a common, wide-spread and characteristic inhabitant of the freshwater tidal region of the river Scheldt and its tributaries in NW Belgium. The species occupies a rather narrow zone in the uppermost intertidal area, which is characterized by large amounts of tidal drift covering the bottom, and usually by a luxuriant vegetation of tall, nitrophilous herbs, often withUrtica dioica dominant. Other characteristic molluscs of this zone areCarychium minimum, Oxyloma pfeifferi, O. sarsi, Deroceras laeve, Vitrea crystallina andZonitoides nitidus, locally alsoNesovitrea hammonis. Communication nr. 143 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands     

Influence of soil gas contamination on tree root growth

Summary Rooted-cuttings and saplings of green ash (Fraxinus lanceolata) and hybrid poplar (Populus spp) were planted on a former municipal refuse landfill and on a nearby nonlandfill control plot. The root systems of four trees of each species and size were excavated on the landfill plot-two growing in an area where the concentrations of anaerobic landfill gases were relatively high and two in a relatively low-gas area. Two trees of each species and size were also excavated on the control. The root systems of both species were significantly shallower on the landfill plot than on the control. Green ash appeared to avoid the adverse gas environment of the deeper soil layers on the landfill by producing adventitious roots. Hybrid poplar became adapted in a different manner, by redirecting root growth from the deepter soil layers to the soil surface.     

Clustering of fatty acids in phospholipid bilayers

From electrophoresis experiments it is concluded that acidic phospholipids incorporated in liquid crystalline phosphatidylcholine bilayers at neutral pH are randomly distributed. The same is true for spin-labelled fatty acids. In contrast, long chain fatty acids are not fully ionized at neutral pH and appear to be clustered, i.e. they segregate out into patches. Only at $\text{pH}\text{>11}$ is the fatty acid-COOH group fully ionized and charge repulsion leads to a random distribution of the fatty acid within the plane of the bilayer.     

Transbilayer distribution of phospholipids in photoreceptor membrane studied with trinitrobenzenesulfonate alone and in combination with phospholipase D

In a further study of the transbilayer distribution of phospholipids in rod disk membranes, the amino group reagent, trinitrobenzenesulfonate, and the phospholipid-hydrolyzing enzyme, phospholipase D, have been used alone and in combination.Under carefully defined conditions (1 mM trinitrobenzenesulfonate, pH 7.4, 20°C, darkness), trinitrobenzenesulfonate yields limited final levels of modification of phosphatidylethanolamine and phosphatidylserine, suggesting only minor reagent penetration and membrane disturbance under these conditions.Treatment of stacked disks with trinitrobenzenesulfonate under these conditions leads to a biphasic modification of the a aminophospholipids. Relatively fast (less than 1 h) modification of 50% phosphatidylethanolamine and 40% phosphatidylserine occurs, slowly rising (approx. 3 h) to 60 and 50%, respectively.Extensive treatment of stacked disks with phospholipase D leads to the hydrolysis of 55% phosphatidylcholine and 50% phosphatidylethanolamine, while phosphatidylserine is hardly attacked by this enzyme.Treatment of stacked disks with trinitrobenzenesulfonate after prior treatment with phospholipase D leads to no further modification than that maximally obtained with either reagent alone: about one-half of the three major phospholipid classes is accessible. Although both reagents differ greatly in molecular size, mode of action and other properties, they apparently see the same pool of phosphatidylethanolamine, their joint substrate. Considering that we start with the original right-side-out configuration, that all phospholipids can in principle be modified (no shielding) and that the membrane remains essentially intact, we conclude that the accessible lipid pool represents the outer face of the disk membranes.These results confirm our earlier conclusions from treatment with three phospholipases that the three major phospholipids are nearly symmetrically distributed over the two faces of the disk membrane.The divergence with the conclusions of other investigators is most likely explained by their use of disk membranes (disk vesicles) in which the original phospholipid distribution had not been maintained and/or of conditions under which trinitrobenzenesulfonate markedly penetrates the membrane.