Generic interrelationships within the Spionidae (Annelida: Polychaeta)

The phylogenetic relationships of spionid genera are estimated from parsimony analyses of morphological characters, with Trochochaetidae, Poecilochaetidae and Uncispionidae as outgroups. A first analysis of currendy recognised genera proved inconclusive and even exclusion of six of the most polymorphic genera resulted in 13 305 equally parsimonious trees and a fully collapsed consensus tree. A second analysis using only the type species of each genus, yielded four equally parsimonious trees; reduced to two after successive weighting. The topologies of these two trees indicated division of the family into four main groups: (1) Aonidella and Xandaros; (2) Prionospio (sensu fato)-complex, Laonice, Spiophanes and Aonides; (3) a large assemblage of genera, including Polydora-{senm late), Scolelepis, Malacoceros and Spio; (4) Atherospio, Pseudatherospio and Pygospiopsis. Earlier literature classifications of the group are evaluated and compared with die new results.     

Comparative Biology of Zebra Mussels in Europe and North America: An Overview

SYNOPSIS. Since the discovery of the zebra mussel, Dreissenapolymorpha, in the Great Lakes in 1988 comparisons have beenmade with mussel populations in Europe and the former SovietUnion. These comparisons include: Population dynamics, growthand mortality rates, ecological tolerances and requirements,dispersal rates and patterns, and ecological impacts. NorthAmerican studies, mostly on the zebra mussel and a few on asecond introduced species, the quagga mussel, Dreissena bugensis,have revealed some similarities and some differences. To dateit appears that North American populations of zebra musselsare similar to European populations in their basic biologicalcharacteristics, population growth and mortality rates, anddispersal mechanisms and rates. Relative to European populationsdifferences have been demonstrated for: (1) individual growthrates; (2) life spans; (3) calcium and pH tolerances and requirements;(4) potential distribution limits; and (5) population densitiesof veligers and adults. In addition, studies on the occurrenceof the two dreissenid species in the Great Lakes are showingdifferences in their modes of life, depth distributions, andgrowth rates. As both species spread throughout North America,comparisons between species and waterbodies will enhance ourability to more effectively control these troublesome species.     

The role of ultrasonic bat detectors in improving inventory and monitoring surveys in Vietnamese karst bat assemblages

Bats account for 30% of mammal diversity in SE Asia and are potential bioindicators of wider biodiversity impacts resulting from habitat loss and climate change.As existing sampling techniques in the region typically fail to record bats that habitually fly in open areas and at higher altitudes,current inventory efforts are less than comprehensive.Acoustic sampling with bat detectors may help to overcome these limitations for insectivorous bats,but has yet to be tested in mainland SE Asia.To do so,we sampled...     

A review of the genus Johnstonia Quatrefages, 1866 (Polychaeta, Maldanidae), with a description of a new species from Trinidad, West Indies

In the interests of nomenclatural stability it is proposed that Johnstonia Quatrefages. 1866 (Polychaeta, Maldanidae) be conserved relative to its senior homonym Johnstonia Quatrefages, 1849 (Polychaeta, Nereidae) and its coexistent junior homonym Johnstonia Basir, 1956 (Nematoda, Thelastomatidae). Type material of all species previously assigned to Johnstonia Quatrefages, 1866 is re-examined and a new species from Trinidad described. All three valid species ( J. clymenoides Quatrefages, 1866; J. knysna Day. 1955; J. duplicata sp. n.) are described and figured in detail. An unnamed fourth species is known only from fragments collected off West Africa, and Johnstonia gracilis Kinberg, 1867 is newly synonymised with Euclymene oerstedii (Claparède. 1863).     

Zebra Mussel Infestation of Unionid Bivalves (Unionidae) in North America

SYNOPSIS. In 1989, zebra mussels received national attentionin North America when they reached densities exceeding 750,000/m2in a water withdrawal facility along the shore of western LakeErie of the Laurentian Great Lakes. Although water withdrawalproblems caused by zebra mussels have been of immediate concern,ecological impacts attributed to mussels are likely to be themore important long-term issue for surface waters in North America.To date, the epizoic colonization (i.e., infestation) of unionidbivalve mollusks by zebra mussels has caused the most directand severe ecological impact. Infestation of and resulting impactscaused by zebra mussels on unionids in the Great Lakes beganin 1988. By 1990, mortality of unionids was occurring at somelocations; by 1991, extant populations of unionids in westernLake Erie were nearly extirpated; by 1992, unionid populationsin the southern half of Lake St. Clair were extirpated; by 1993,unionids in widely separated geographic areas of the Great Lakesand the Mississippi River showed high mortality due to musselinfestation. All infested unionid species in the Great Lakes(23) have become infested and exhibited mortality within twoto four years after heavy infestation began. Data indicate thatmean zebra mussel densities >5,000–6,000/m² and infestationintensities >100-200/unionid in the presence of heavy zebramussel recruitment results in near total mortality of unionids.At present, all unionid species in rivers, streams, and akesthat sympatrically occur with zebra mussels have been infestedand, in many locations, negatively impacted by zebra mussels.We do not know the potential consequences of infestation onthe 297 unionid species found in North America, but believezebra mussels pose an immediate threat to the abundance anddiversity of unionids.     

Electron microscopic structure and oxygen evolution activity of thylakoids from Avicennia marina prepared under different osmotic and ionic conditions

Abstract Stacking of thylakoid membranes in vitro was assessed using electron microscopy. Grana stacks of spinach thylakoids formed when 5 mol m^?3 MgCl₂ was present, but no stacking of thylakoids from the mangrove Avicennia marina occurred in the presence of 10 mol m^?3? MgCl₂. Isolation of mangrove thylakoids with a high osmotic strength medium did not induce grana formation if the medium consisted only of sorbitol or glycinebetaine. Addition of cations to the high osmotic strength medium did induce some loose-grana formation, with divalent cations being more effective than monovalent cations. Glycinebetaine was a better osmoticum than sorbitol for grana formation provided divalent cations had been added. Oxygen evolution activity of the preparations was influenced by the amount of membrane stacking, with the preparations with the greatest amount of stacked membrane having the highest activity. Isolation with sorbitol or glycinebetaine based media did not alter this pattern, nor did assay in sorbitol or glycinebetaine. Mangrove thylakoids have a requirement for both a high osmotic strength and divalent cations for grana formation in vitro which may be related to the low water potential of the plant environment in vivo.     

Revision of the type species of Sigalion, Thalenessa and Eusigalion (Polychaeta: Sigalionidae)

The type species of Sigalion Audouin & Milne Edwards, 1830 (5. mathildae), Thalenessa Baird, 1866 (S. edwardsi Kinberg, 1856) and Eusigalion Augener, 1918 (E. vazensis) are re-examined. Since they were first described all three genera have been variously misrepresented, but are currently distinguished by the presence (Thalenessa; syn. Eusigalion) or absence (Sigalion) of a median antenna. Material examined in the present study indicates that S. mathildae also possesses a median antenna. Thalenessa and Eusigalion are considered to be junior synonyms of Sigalion and the generic placings of all species attributed to these genera are investigated.     

CONDUCTION IN THE NERVE-FREE EPITHELIA OF SIPHONOPHORES

Optical and election microscopy leave little doubt that nerveand muscle fibers are completey absent from large stretchesof the epithelium covering the swimming bells in siphonophores(Class Hydrozoa). Behavioral experiments show that these regionsmust conduct, and electrophysiological evidence of propagateddepolarizations in the epithelial cells has been obtained. Conductionvelocities are in the order of 20-50 cm/sec, and a refractoryperiod of 2-3 msec has been measured. Conduction is non-decrementaland unpolarized. Non-nervous conduction probably occurs in other siphonophoretissues (two examples are discussed), and it may be importantin the behavior of many Hydrozoa.