The population biology ofPlanaria torva (Müller) (Turbellaria,Tricladida)

Summary 1. A quantitative study of the population biology ofPlanaria torva (Müller) living in a productive lake, based on monthly samples over a period of 20 months, is presented. 2. Samples of triclads, their cocoons and other organisms were taken from bricks placed at a shallow depth in the lake. They provided relative information on changes in population size structure and demonstrated the temporal breeding of this triclad. 3. Cocoon production byP. torva began in January and reached a peak in March–April. This was followed by a peak in recently-hatched young during May–June. Adults reached a maximal proportion of the total population in January and most had died by July. 4. Changes in size structure suggest that intra-specific competition occurred during June–July following the recruitment of young. This hypothesis is supported by other independent evidence. 5. Attempts to measure fecundity based on cocoons and young gave very different results attributed to the sampling technique.     

The reproductive morphology of Dumontia incrassata (O. F. Müller) Lamouroux

The reproductive morphology of Dumontia incrassata (O. F. Müller) Lamouroux is described from New Hampshire, U.S.A. populations. Mature carpogonial and auxiliary branches are usually 5 and 6 celled, respectively, but both may range from 4 to 9 cells. Auxiliary branches are more numerous than carpogonial branches; however, the ratio of carpogonial to auxiliary branches increases towards the apex of the frond. A linear relationship exists between the position of the generative auxiliary cell and the number of cells in the auxiliary branches. In most cases the third cell from the top of the auxiliary branch becomes the generative auxiliary cell. The probabilities for different positions of the generative auxiliary cells are summarized. During spermatangial development, four mother cells are initially produced per cortical cell initial; subsequently, successive spermatangia are cut off obliquely and on opposite sides of each mother cell. Monoecious asexual plants of D. incrassata are described, as well as an irregular tetraspore development.Scientific Contribution Number from the New Hampshire Agriculture Experiment Station; also issued as contribution No. 81 of the Jackson Estuarine LaboratoryScientific Contribution Number from the New Hampshire Agriculture Experiment Station; also issued as contribution No. 81 of the Jackson Estuarine Laboratory     

Distribution pattern of the dinoflagellateCeratium hirundinella (O. F. Müller) Bergh in a reservoir

Horizontal distribution of the dinoflagellateCeratium hirundinella (O. F. Müller) Bergh in the Ishitegawa Reservoir, Ehime Prefecture, Japan, was investigated. Water quality was also surveyed. It was observed that the population ofC. hirundinella exponentially decreased in number from the head of the reservoir to the dam site. Further investigation proved thatC. hirundinella initiated growth at the head of the reservoir, and later gradually expanded downstream. It was found during the period of increase in water temperature that the cell density ofC. hirundinella at the uppermost station exponentially increased.     

The life-history of Haementeria costata (Fr. Müller) (Glossiphoniidae: Hirudinea)

The frequency of occurrence of Haementeria costata in the waters of north-eastern Poland is 66.5%. This leech is usually found in shallow water zones frequented by water fowl and mammals.The different numbers of individuals taking food and different amounts of food consumed at one meal during successive feedings resulted in individuals of a cohort reaching sexual maturity at the age of 1, 2, and 3 years and surviving for 1.5, 2.5 and 3.5 years, respectively. The differences in weight and age of individuals of populations in their natural environment and in the laboratory depend on the accessibility of food.     

Flatworms like it round: nematode consumption by <Emphasis Type="Italic">Planaria torva</Emphasis> (Müller 1774) and <Emphasis Type="Italic">Polycelis tenuis</Emphasis> (Ijima 1884)

To identify the mechanisms whereby substrate embeddedness and water velocity influence Nooksack dace (Rhinichthys cataractae subsp. cataractae) prey capture efficiency, we stocked dace in foraging arenas with varying substrate types over a range of velocities (0, 25, 35 cm s^?1) and measured their efficiency of prey capture. We stocked a known number of mayfly (Ephemeroptera), black fly (Simuliidae), and chironomid (Chironomidae) larvae in each foraging arena and measured the number of invertebrates remaining after 12 h. Foraging efficiency for mayflies was significantly reduced over unembedded substrate, and capture efficiency for all taxa decreased at higher velocities in all substrate treatments. Decreased foraging efficiency indicates that higher velocities may degrade the accuracy of prey strikes, that dace may alter their foraging behavior to reduce energy expenditures at higher velocities, that there is less available foraging habitat within their velocity tolerances, or that invertebrates become more interstitial at higher velocities. Although it is difficult to unambiguously discriminate among these mechanisms with our experimental design, our results suggest that dace are adapted to foraging in low-velocity micro-habitats within the boundary layer, and that their foraging efficiency may be sensitive to both the refuging ability of their prey and velocity and turbulence at their focal point.     

Effects of tissue extract of adults on metamorphosis in Ascidia mentula O.F. Müller and Ascidiella scabra (O.F. Müller)

Unhatched, but fully developed larvae of two solitary ascidians Ascidia mentula O.F. Müller and Ascidiella scabra (O.F. Müller) were incubated in a variety of adult tissue extracts, which an earlier study had shown to accelerate metamorphosis. Our study confirmed this observation and showed, furthermore, that tissue extracts induce tail resorption in unhatched larvae of Ascidiella. For both species, the most active induction of metamorphosis was obtained with tunic tissue extracts. The results indicate that chemical stimulation without the presence of tactile cues may initiate metamorphosis. We suggest that the ability of tunic extracts to induce metamorphosis may explain juvenile establishment on adult ascidians and their aggregated distribution found in nature.     

The localization of inorganic elements,particularly vanadium and sulphur,in haemolymph from the ascidians Ascidia mentula (Müller) and Ascidiella aspersa (Müller)

Vanadium and sulphur were found by X-ray microanalysis in three different cell types, morula cells, signet-ring cells, and granular amoebocytes, from each of the ascidians Ascidia mentula (Müller) and Ascidiella aspersa (Müller). In addition to the cells containing vanadium and sulphur a few vacuolar cells containing high concentrations of iron, magnesium and calcium were also found. After fixation in the presence of strontium or barium chlorides another cell type containing large amounts of precipitated sulphur was also found, confirming our previous findings that many haemolymph cells in these species contain large amounts of sulphate only. The presence of these various cell types is discussed in relation to the question of the acidity of ascidian blood cells.     

The morphology and fine structure of the colourless colonial flagellate Anthophysa vegetans (O. F. Müller) Stein

A strain of Anthophysa vegetans (O. F. Müller) Stein (Chrysophyceae or Chrysomonadida) was grown in culture and examined in detail by light and electron microscopy. It was shown to be a typical, though apochlorotic, member of its class; features of interest include a well-developed leucoplast and a starch-like reserve product. Aspects of the largely inorganic stalk are also discussed.     

The general biology of Verruca stroemia (O. F. Müller). I. Geographical and regional distribution; Cirral activity and feeding

As an introduction to a series of papers on Verruca stroemia (O. F. Müller) the geographical and regional distribution is given: it is characteristically an eastern Atlantic shallow-water species but is not uncommon in parts of the Mediterranean Sea.The cirri and mouth parts are described and also the opercular membrane which in some ways resembles that of Lithotrya.In still water the cirri may be slowly extruded and withdrawn with relatively little forward movement on the down-stroke. The cirri are held close to the ‘velum’ and no internal mantle cavity current could be detected: cirral movements cause small external currents as in a balanid. In the presence of water currents the cirri show a typical extension reaction: when particles strike the cirri they are withdrawn and the food passed to the mouth. The cirri respond only partly to the current direction. Verruca stroemia has no muscles other than the adductor scutorum attached to the shell and cannot change the volume of the mantle cavity by movement of the operculum. Cirral activity closely resembles that of Pollicipes.During pre-copulatory movements the penis makes searching movements but the area searched is relatively restricted.Nauplii are expelled behind the cirri as the latter are extruded, the caudal appendages seeming to play a part in dispersing the nauplii.An examination of the gut contents reveals few whole organisms, rather a mass of fine unrecognizable particulate matter.     

General morphology and ultrastructure of the radula of Testudinalia testudinalis (O. F. Müller, 1776) (Patellogastropoda,Gastropoda)

The radular morphology of the patellid species Testudinalia testudinalis (O. F. Müller, 1776) from the White Sea was studied using light, electron, and confocal microscopy. The radula is of the docoglossan type with four teeth per row and consisting of six zones. We characterize teeth formation in T. testidinalis as follows: one tooth is formed by numerous and extremely narrow odontoblasts through apocrine secretion; this initially formed tooth consists of numerous vesicles; the synthetic apparatus of the odontoblasts is localized in the apical and central parts of the cells throughout the cytoplasm and is penetrated by microtubules which are involved in the transport of the synthesized products to the apical part of the odontoblast; the newly formed teeth consist of unpolymerized chitin. Mitotic activity is located in the lateral parts of the formation zone. The first four rows contain an irregular arrangement of teeth, but the radular teeth are regularly arranged after the fifth row. The irregularly arranged teeth early on could be a consequence of the asynchronous formation of teeth and the distance between the odontoblasts and the membranoblasts. The morphological data obtained significantly expands our knowledge of the morphological diversity of the radula formation in Gastropoda.     

Multifunctions of the upper lip and a ventral reflecting organ in a bioluminescent ostracod Vargula hilgendorfii (Müller, 1890)

Multifunctions of the upper lip in a bioluminescent myodocopid Vargula hilgendorfii were studied by video observation and histological method. The localization of luciferin and luciferase gland cells within the upper lip was partly successful. Two long protrusions of the upper lip, both of V. hilgendorfii and a non-luminescent species of the same family, immediately anterior to the mouth, were found to show very flexible movement especially while eating, as if smearing on the food surface a secretion from the protrusions (glands), which may support the hypothesized secretion of digestive enzymes from the upper lip. This hypothesis is further supported by the new finding of a pair of ducts which connect the basal part of the upper lip with the posterior digestive duct (stomach). Comparative studies of V. hilgendorfii with several sympatric non-luminescent species of the same family have also revealed that it has a characteristic reflecting organ immediately posterior to the anus. It is a conical small protrusion, as if dangling from the ventral edge of the abdomen at the apex of the cone. It is observable only in live specimens, when the furca, which is located outwardly to the organ, is sufficiently transparent. When illuminated, the reflecting organ reflects the distinct light. The diameter of the mirror (chemical composition provisionally analyzed) is about 6–8% of the carapace length. The organ develops from the very first stage of its ontogeny without reference to sex, which suggests that the function may be related to intraspecific signaling or predatory deterrence.     

The influence of various temperature regimes on the abundance dynamics and thermal tolerance of cladoceran Ceriodaphnia quadrangula (O.F. Müller, 1785)

Experimental studies on the abundance dynamics and thermal tolerance of cladoceran Ceriodaphnia quadrangula (O.F. Müller, 1785) as they depend on the value and action pattern of a thermal factor, as well as field observations and mathematical calculations were carried out. Based upon the results of these studies, the values of the temperature zone of normal vital functions (17.0–25.0°C) and of the zones of temperature “static” optimum (21.4–25.0°C) were determined for C. quadrangula. It was shown using experimental populations of C. quadrangula as an example that it is necessary not only to keep the range of the factor optimal values within the tolerance scale (i.e., the static optimum) but also to maintain the optimal parameters of dynamic factor changes (or “dynamic optimum”) in order to form optimal conditions for their growth and development. For C. quadrangula this dynamic temperature optimum is 24.0 ± 1.1°C, with non-periodical (graded) warming to 24.7–25.3°C over five to eight days.     

Purification and characterisation of glutathione S-transferases from the freshwater clam Corbicula fluminea (Müller)

Glutathione S-transferases (GSTs) are involved in the phase II detoxification metabolism. To provide a molecular basis for their use as biomarkers of pollution, cytosolic GSTs from the freshwater clam Corbicula fluminea have been purified by glutathione-Sepharose affinity chromatography, anion-exchange chromatography (AEC) and reversed-phase (RP) HPLC. SDS-PAGE of visceral mass (VM) affinity-purified extracts revealed four subunits with apparent molecular masses (MW) of 30.2, 29.2, 28.5 and 27.2 kDa. Analysis by non-denaturing PAGE revealed three acidic dimeric proteins with apparent MW of 64, 55 and 45 kDa, named GSTc1, GSTc2 and GSTc3, respectively, based on their elution order by AEC. Only GSTc2 and GSTc3 exhibited GST activity towards 1-chloro-2,4-dinitrobenzene. A tissue-specific subunit pattern was obtained by RP-HPLC of affinity-purified extracts from VM and gills (GI): three major peaks were resolved, one of which was common to both tissues. MW of each VM subunit was determined by electrospray ionisation-mass spectrometry: 23602+/-1 Da for the major subunit and 23289+/-1 Da for the minor ones. Immunoblot analysis revealed all subunits from both tissues were related to the Pi-class GSTs. In addition, minor VM subunits were slightly related to the Mu-class ones. The interest of such molecular studies in biomonitoring programs is discussed.     

Competition between Brachionus calyciflorus Pallas and Brachionus patulus (Müller) (Rotifera) in relation to algal food concentration and initial population density

Competitive laboratory experiments between Brachionus calyciflorus and B. patulus were conducted at low (1×10⁶ cells ml^–1) and high (3×10⁶ cells ml^–1) densities of Chlorella vulgaris and four initial inoculation densities (numerically, 100% B. calyciflorus; 75% B. calyciflorus + 25% B. patulus; 50% each of the two species; 25% B. calyciflorus + 75% B. patulus and 100% B. patulus). Population densities were enumerated and the medium was changed daily for 20 days. B. patulus was a superior competitor in low food density regardless of inoculation density. At high food density, B. calyciflorus showed higher population growth in the first week but thereafter was outcompeted by B. patulus regardless of initial density. When grown alone, B. calyciflorus reached peak abundances (mean ± standard error) of 31±3 and 81±7 individuals ml^–1 at low and high food densities, respectively. The corresponding values for B. patulus were 130±2 and 306±13. The adverse effects of B. patulus on the peak abundances of B. calyciflorus were higher at low food concentration. Data on egg ratios (eggs female^–1) revealed an inverse relation with population abundance of both tested rotifer species. Our results indicated that the rate of population increase of a species was not a good indicator of its competitive ability. Instead, the ability to reproduce under continuously diminishing food resources (until a threshold level) was responsible for the competitive edge of B. patulus over B. calyciflorus. This was further influenced by the relative inoculation densities of the tested rotifer species and the offered food densities.     

Allozyme variation in the camaenid tree snails Amphidromus atricallosus (Gould, 1843) and A. inversus (Müller, 1774)

We examined allozyme variation in two camaenid tree snails, Amphidromus atricallosus and A. inversus, across two principal regions of Thailand and from Singapore, plus for A. inversus, one site in peninsular Malaysia. Using horizontal starch gel electrophoresis, 13 allozyme loci (11 polymorphic) were screened for A. atricallosus and 18 (5 polymorphic) for A. inversus. Heterozygosity was higher in A. atricallosus (Hexp=0.018-0.201, mean=0.085) than in A. inversus (Hexp=0-0.023, mean= 0.002). Genetic heterogeneity among samples was higher in A. inversus (Fst=0.965) than in A. atricallosus (Fst=0.781). Within A. atricallosus, populations were more differentiated in southern Thailand (Fst=0.551) than in eastern Thailand (Fst=0.144). The high Fst and low Hexp in populations of A. inversus suggest that this species is likely to have experienced a series of strong bottlenecks, perhaps occurring chiefly on offshore continental-shelf islands. The low Fst values of A. atricallosus in eastern Thailand suggest frequent gene flows among populations in this region. The southern and eastern samples of A. atricallosus exhibited fixed allele differences at four loci and great genetic distance (Nei's D=0.485-0.946), suggesting that these two samples may actually represent, or else be evolving into, separate species.