Lysosomal responses to experimentally injected anthracene in the digestive cells of Mytilus edulis

Experimentally injected anthracene (10 to 100 g mussel^-1) has been shown to induce dose-dependent lysosomal destabilisation and release of hexosaminidase in the digestive cells of Mytilus edulis after 24 h. This destabilisation was accompanied by cytological evidence of cytolysis of the digestive cells. The destabilising effect of 100 g of injected anthracene persisted for 96 h with a return to the control condition by 168 h. These results are discussed in the context of environmental contamination by polycyclic aromatic hydrocarbons.     

Experimental studies on the relationship between natural copper complexes and their toxicity to phytoplankton

Toxicity of copper to phytoplankton depends on the physicochemical form of the metal. Organic substances liberated into the culture medium by the phytoplankton species Cricosphaera elongata are able to detoxify and complex copper. The molecular weight range of these organic substances has been determined by ultrafiltration.     

Dispersal,population structure and burrow shape of Ocypode cursor

The distribution of the sand crab Ocypode cursor (L.), as indicated by the number of burrows, was studied for 2 years in a 50×50 m sand beach area in northern Israel. A definite relationship was established between the distribution pattern from the seashore inwards towards the sand dunes, and the degree of sand moisture as it changed seasonally. During autumn, more crabs were found at a distance of 15 to 25 m from the sea where sand moisture was about 14%. At the beginning of winter crabs dispersed evely, disappearing with advancing winter. Crabs reappeared in spring, although in smaller numbers, dispersing in a pattern similar to that in autumn. At the beginning of summer and later on, more crabs appeared and concentrated closer to the sea (5 to 10 m). The population structure was analysed directly by measuring the crab's dimensions, and indirectly by counting burrows and measuring the diameter of their openings. Direct analysis revealed two distinct sizeage groups: smaller crabs 0.5 to 3 cm long, and larger ones over 4 cm long. The smaller burrows were inhabited by the first group and were mostly found closer to the sea; the second group was found more landwards. Three main types of burrow shapes are described.     

Morphological variation and life history in cylindrical forms of Scytosiphon lomentaria (Scytosiphonaceae: Phaeophyta) from southern Australia

Variation amongst wild populations of Scytosiphon lomentaria (Lyngbye) Link is shown to be of a continuous nature, and the species cannot be readily segregated into distinct subspecific taxa on the basis of morphological characteristics. Zoospores derived from plurilocular sporangia developed asexually into cylindrical thalli under long and short days at 16°C. The progeny of some cylindrical thalli included microthalli bearing plurilocular sporangia or unilocular sporangia. Cylindrical forms of S. lomentaria were obtained in culture from wild microthalli of two kinds, bearing either plurilocular or unilocular sporangia. The microthalli differ morphologically from the ralfsioid stages commonly known to be plethysmothalli and sporophytes of S. lomentaria, but closely resemble the microthalli derived from cultures of wild S. lomentaria.     

Cephalodiscus sp. (Hemichordata: Pterobranchia): observations of functional morphology,behavior and occurrence in shallow water around Bermuda

A pterobranch hemichordate, Cephalodiscus sp., was collected from Bermuda just below the low-tide mark in July 1983 and again in October through December 1983. This is the third report of this genus in shallow water and the second for the Western Hemisphere. Specimens were observed alive in the laboratory. Colonies consist of zooids at various stages of development arranged in clusters inside a translucent, collagenous coenecium. Cilia-driven currents of the zooids are used in a method of filter-feeding similar to phylactolaemate bryozoans.     

Autoradiographic study of feeding and the colonial transport of metabolites in the marine bryozoan Membranipora membranacea

Standard autoradiographic techniques were adapted to study the transport of carbon compounds in colonies of Membranipora membranacea (L.). The results indicate that there is transport of carbon-14 between polypides within a colony. Metabolite movement is generally in the direction of the rapidly growing colony edge. Estimates of metabolite transport rates are given.     

Adaptation and equivalence in open-ocean phytoplankton

Two marine phytoplankton species of the North Atlantic Ocean have inherently differt growth responses to changing nutrient conditions. Yet they co-occur. Thus, they can be compared under the same conditions via equivalence, provided that their adaptedness is linked to their responsiveness as follows. If Species x is adapted to nutrient changes, then it is responsive to these conditions and, certainly, if it is responsive to these conditions, then it is adapted to them. There is another expression that is equivalent to this one (that says the same thing): either Species x is adapted and responsive to these conditions or it is neither adapted nor responsive to them. The option just mentioned is resolved so that Emiliania huxleyi as Species x is adapted and responsive and Cyclococcolithus leptoporus as Species x is not adapted and not responsive. All the frequently observed species in the winter half of the year, November to April, from 1961 to 1972 are like E. huxleyi in being adapted and responsive or like C. leptoporus in being unadapted and unresponsive.Contribution No. 5806 from the Woods Hole Oceanographic Institution     

New development in the MOCNESS,an apparatus for sampling zooplankton and micronekton

Four variants of the Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) have been constructed to sample a broad size spectrum of oceanic animals from microzooplankton to micronekton. The systems differ in mouth opening dimensions (ranging from 1/4 to 20 m²), the number of nets carried (from 5 to 20), and the mesh size of the netting (from 64 m to 3.0 mm). A new electronics package enables an operator to send commands down a single conductor, armored cable to open/close the nets and provides 12-bit resolution for the environmental (temperature, depth, conductivity) and net operation data (flow, net-frame angle, net-bar release), which are transmitted up the cable to the deck unit at 2-s intervals. A microcomputer system, interfaced to the deck unit, calculates salinity, volume filtered by a net, net trajectory velocity, and vertical velocity. The data are printed out and stored on disc, and profiles of temperature and salinity versus depth are plotted during the course of the tow. Analysis of the relationship between the geometry of the MOCNESS under tow and the past and present methods used to estimate the water filtered by a net revealed that significant bias is introduced when the ascent or descent angle of a net is disregarded. The bias is a function of the ratio of vertical velocity to net trajectory velocity and results in an underestimate of volume filtered while shooting a net and an overestimate while hauling.