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     

Die Spermiohistogenese des Süßwasser-Ostracoden Notodromas monacha O. F. Müller

Zusammenfassung Die Frühstadien der Spermiohistogenese des Süßwasser-Ostracoden Notodromas monacha, ovale und spindelförmige Spermatiden, werden phasen- und elektronenoptisch untersucht. Die ovalen Spermatiden sind gekennzeichnet durch das Auftreten von Caryomeren, die zu einem einheitlichen Nucleus verschmelzen, und durch die Zusammenlagerung aller Mitochondrien zu einem Nebenkern, aus dem sich zwei Derivate differenzieren. Die spindelförmigen Spermatiden gehen aus den ovalen hervor, indem Kern und Nebenkern-Derivate sowie die Zelle selbst Spindelform annehmen. Der Kern ist durch drei hinsichtlich ihrer Größe und Lage unterschiedliche granuläre Körperchen und einen von einer Doppelmembran umgebenen Bezirk ausgezeichnet. Ein Centriol konnte bisher nicht nachgewiesen werden.

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The spermiogenesis of the fresh-water ostracod Notodromas monacha O.F. Müller

Summary In Notodromas monacha the early stages of the spermiohistogenesis (oval and spindle-like spermatids) have been studied by means of phase contrast and electron microscopy. Oval spermatids are marked by the presence of caryomeres, which during development fuse to form a single nucleus. All mitochondria are accumulated in a Nebenkern which is differentiated into two derivatives. The nucleus, the Nebenkern-derivatives and the cell body become spindle-shaped and thereby the oval spermatids are transformed to spindleshaped spermatids. The nucleus of the spindle-shaped forms is characterized by three granulated particles (different in size and position) and by a double-membrane bounded region. No centriole has been found in this study.

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Für die Anregung zu diesen Untersuchungen sowie für Förderung und Diskussion danke ich meinem Lehrer, Herrn Professor Dr. Dr. h. c. W. E. Ankel.     

Die Spermiohistogenese des Süßwasser-Ostracoden Notodromas monacha O. F. Müller

Zusammenfassung Bei Notodromas monacha (Ostracoda) wird die Entwicklung der Spermatiden von der Spindelbis zur Schlauchform mit Phasenkontrast und elektronenmikroskopisch untersucht. Am Kern der spindelförmigen Spermatiden sind an zwei gegenüberliegenden Seiten jeweils zwei Ausstülpungen der Membran zu beobachten. Aus ihnen werden offenbar unter Beteiligung von Vesikeln des endoplasmatischen Reticulum zwei Flügelstrukturen aufgebaut. Jede Flügelstruktur besteht aus zwei Lamellen, die mit tubulären Elementen besetzt sind. An den schlauchförmigen Spermatiden läßt sich ein dicker Körper und ein dünner Faden unterscheiden. Kern, Nebenkern-Derivate und Flügelstrukturen durchziehen den Körper der Länge nach. Der Faden enthält nur noch den Kern und die Ausläufer der Flügelstrukturen. Im Bereich des freien Körperendes liegt im Kern ein als Chromatin gedeuteter Kolben. Diesem folgt in Richtung zum Fadenende ein dichter Achsenstab, der von einer Doppelmembran umhüllt ist. Im dorso-lateralen Kernraum finden sich elektronendichte Brocken unbekannter Bedeutung. Nach Beendigung des Aufbaues der Flügelstrukturen wird das endoplasmatische Reticulum samt Mikrotubuli weitgehend abgebaut. Gleichzeitig verschwindet die den Achsenstab umhüllende Doppelmembran. Die Flügelstrukturen werden als das für die Motilität der Spermien verantwortliche Organell gedeutet.

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The spermiogenesis of the fresh-water ostracod Notodromas monacha O. F. Müller

Summary The transformation of spindle-like spermatids into tubular forms in Notodromas monacha (Ostracoda) has been studied by means of phase contrast and electron microscopy. At each of two opposite sides of the nucleus of spindle-like spermatids, two extensions of the nuclear membrane arise. These extensions form two Flügelstrukturen (wing-like structures) obviously by participation of vesicles of the endoplasmic reticulum. Each Flügelstruktur consists of two lamellae, each bearing numerous tubules. The tube-like spermatids consist of a large body and a small thread. The nucleus, the Nebenkern-derivatives and the Flügelstrukturen extend through the whole body. Within the thread only the nucleus and the outermost parts of the Flügelstrukturen are found. A columnar body, supposed to be chromatin, is located within that part of the nucleus which is situated in the free end of the body. A dense axial rod extends between the columnar body and the free end of the thread. The dorso-lateral sphere of the nucleus contains electron dense particles of unknown function. As soon as the construction of the Flügelstrukturen is finished, the endoplasmic reticulum and the microtubules are reduced. Simultaneously the double-membrane surrounding the axial rod disappears. The Flügelstrukturen are interpreted as organelles responsible for the motility of the sperm.

     

Preservation of resting eggs of the euryhaline rotifer Brachionus plicatilis O. F. Müller by canning

Recent research has indicated that the hatchability of mass-producedrotifer (Brachionus plicatilis) resting eggs (stored in sea water in thedark at 4°C) gradually decreases due to bacterialinfection of the porous egg surface. We investigated whether lyophilizationas well as a canning treatment could solve the problem of bacterialinfection of resting eggs. The canning method preserves eggs in a dry form,after lyophilization at –40°C. The resting eggs werepacked in cans under various pressures: 21, 34, 48, 61, 75, 88 and 101 kPa.The viability of the canned resting eggs was tested by hatching experimentsdone 6 and 12 months after canning and storage at 5°C.When partial pressures were less than 88 kPa, percent hatching after 6months ranged between 16 and 20%, similar to that of uncanned eggs(19% hatching), but significantly lower (9 and 11%, P <0.01) at 88 and 101 kpa. Even after 12 months, percent hatching remained at35% when canning was at 61 kpa. Lyophilization and canning at partialpressure lower than 88 kPa could therefore preserve resting eggs, andhatchability was maintained. Canned eggs that were treated with NaClO (1 mgl^–1) or NFS-Na (5 mg l^–1) showed a significantlyhigher percent hatching (68% and 80%, respectively, each P<0.05) than untreated eggs.     

Observations on the clypeasteroid Echinocyamus pusillus (O. F. Müller)

The tiny echinoid Echinocyamus pusillus (O. F. Müller) is equipped with specialized external structures that suit it for a wide variety of environments. Special features include the ability to burrow in sediments of fine sand to shell gravel and to climb vertically.Specimens dredged off the west coast of Scotland were observed in aquaria and with the SEM. E. pusillus is characterized by three kinds of spines, and by two of pedicellariae. In contrast to sand dollars, the spines play a passive rôle in the feeding and burrowing operation, probably retaining a defensive nature as in the regular urchins. It is the podia that are chiefly involved in climbing, burrowing, righting, and probably feeding. Surface ciliary currents transport particles, but not to the mouth; they may have a respiratory or cleansing function. Experimental animals did not burrow in either very fine or very coarse sand, probably because a certain relationship exists between particle weight and podia size.E. pusillus shares behavioural and structural characteristics with regular and irregular urchins. It is not a true sand dollar, but may illustrate an evolutionary stage towards such a form.     

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.     

Effect of water temperature on the excystment of the dinoflagellate Ceratium hirundinella (O. F. Müller) Bergh

The effect of water temperature on the excystment of the dinoflagellate Ceratium hirundinella (O. F. Müller) Bergh was studied in the laboratory. Excystment was observed between 15–30 °C and was 2% at an optimum water temperature of 20 °C–25°C. Little excystment occurred between 5 and 10 °C. The results at low temperatures are not in accordance with those obtained in an English lake. This disagreement suggests an adaptability of excystment to the temperature regime of the lake.     

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.     

Physiological adaptations in the survival of rotifers (Brachionus plicatilis,O. F. Müller) at low temperatures

The biology of the rotifer Brachionus plicatilis has been studied extensively in recent years, due to its importance in aquaculture. Today, the culture of several marine fish species relies completely on the daily production of live rotifers.In the present paper we explore the conditions that facilitate maintaining live rotifers for extensive periods at low temperatures. In addition to its possible contribution in providing reserve stocks for commercial application, these studies may be of ecological importance. They could explain some of the physiological adaptive mechanisms that are involved in the survival of rotifers under adverse environmental conditions.Experimental results showed relatively high survival rates (82–85%) in rotifers that were cultured at 25 °C and exposed later to -1 °C for 12–14 days. During this period, rotifers were kept without food and their media were not changed. The survival was found to depend on the rotifer culture conditions, prior to exposure to -1 °C. These included the type of food fed to rotifers (yeast or algae), the salinity in which they were cultured, and an essential acclimation period of 2–6 day at 4 °C or 10 °C. The acclimation period was associated with the synthesis of at least one specific protein and accumulation of lipids. Profiles of protein synthesis in rotifers incubated at 10 °C revealed a 94 kD protein, which did not appear in rotifers cultured at 25 or 37 °C. Immunoisolation, using a polyclonal antibody that was prepared against HSP60, revealed that this protein was synthesized in rotifers kept at 10, 25 or 37 °C. However, this antibody did not react with the 94 kD peptide.In addition, rotifers kept at 10 °C accumulated substantial amounts of lipids, including eicosapentaenoic acid (EPA), which is found in the algae fed to them. These results support the hypothesis of specific adaptations to survival at low temperatures during an acclimation period.     

Analysis of the emergence of the Scarce Chaser Libellula fulva O.F. Müller, 1764 (Odonata: Libellulidae)

The Scarce Chaser (Libellula fulva) is widespread in Europe and in many regions is relatively common. It is also abundant in the lake districts of western and northern Poland. Although the species frequently occurs in large numbers its biology is poorly known. Emergence of L. fulva was investigated in this study as a contribution to the life history of the species. Studies were carried out in the vicinity of Chojno (52°41′ N, 16°12′ E) on the edge of the Notecka Forest in 2003 and 2004. The stem habitat of the population is a stream with the adjacent swamps. Libellula fulva belongs to the spring species sensu Corbet (1999). The emergence of the studied population lasted 19 days (between 18 May and 5 June) and 31 days (between 13 May and 12 June) in 2003 and 2004, respectively. It was characterised by synchronous and, especially in the first phase, mass emergence. The high synchronisation is reflected in the fact that 50% of the population had emerged by the seventh (in 2003) and the fifth (in 2004) days of the process. This is vital to the imagines, which mature and return to the water body as soon as possible to reproduce. Timing of the end of emergence depends on atmospheric conditions during its duration and the conditions preceding the start of emergence on a given day. In the daily course there is a tendency for emergence to finish as soon as possible. Extension of the emergence is synonymous with increased mortality in the dragonfly population caused by predators.     

Temperature conditions enhancing resting egg production of the euryhaline rotifer Brachionus plicatilis O. F. Müller (Kamiura strain)

We examined the effect of low temperature treatment(12°C), followed by transfer to highertemperature (25°C), on resting egg formation ofthe rotifer Brachionus plicatilis, Kamiurastrain. This strain has been mass cultured as livefeed at Kamiura Station (Japan Sea FarmingAssociation) for 9 years at 20°C without theappearance of sexual reproductive stages.After preculture in 20 l of 27 seawater at 12°C for 0, 10, 20, and 30 days,rotifers were inoculated into 0.5 l mass cultures andcultured at 25°C for 7–9 days. The inoculationdensities were changed from 20 to 400 ind. ml^–1,depending on mixis rate. Condensed and frozen Nannochloropsis oculata was fed to rotifers at thefeeding rate of 0.14 µg (dry weight)rotifer^–1day^–1. The control was cultured at12°C for the entire 36 day experiment. No mixisappeared and no resting eggs were produced when thelow temperature treatment was 0 or 10 days. However,mixis rates reached 50-60% after 20 or 30 days ofexposure to 12°C. The number of resting eggsproduced in these treatments reached 25,500 about 13 times higher than the control. Our resultssuggest that low temperature stimulated mictic femaleproduction and the transfer to the high temperatureaccelerated resting egg formation. This method may beuseful for producing resting eggs of rotifer strainsthat lack sexual reproduction in the common culturecondition at larval rearing facilities.     

Immunohistochemical demonstration of a CCK-like peptide in the nervous system of a marine annelid worm,Nereis diversicolor O.F. Müller

Summary Perikarya and nerve fibers containing a substance immunologically related to CCK-8 were detected in the nervous system of Nereis, a marine annelid worm. The most noteworthy immunostaining was seen in cell bodies, localized at the periphery of the brain, within nuclei 5, 6, 7, 9, 10, 13, 14, 15, 17, 20, 23–24. Immunoreactive fibers were also found in the neuropile without any particular grouping. Numerous other positive perikarya occur in the medio-ventral portion of the ventral nerve cord, and in the ventral and dorsal parts of the suboesophageal ganglion. In addition to the cell bodies in the cerebral external layer, immunoreactive axons were abundantly observed in the connectives between the ganglia. Moreover, our results demonstrate CCK-like staining in neurons showing variations in size and shape, and in affinity for paraldehyde fuchsin. The present results support the hypothesis that this peptide may exert a role as neurotransmitter or neuromodulator in annelids.     

Occurrence and coexistence in Nereis diversicolor O.F. Müller (Annelida Polychaeta) of substances immunologically related to vertebrate neuropeptides

Summary Numerous immunochemical and immunohistochemical studies have shown a wide distribution of several families of neuropeptides in invertebrates as well as vertebrates. There are relatively few data available for Annelida: Polychaeta. Therefore, we undertook an immunohistochemical investigation in the marine worm Nereis.Among the vertebrate type antibodies tested, those against met-enkephalin, LH-RH, vasopressin, oxytocin and ACTH had negative or only very slight effects. Slight to moderate reactions were obtained for VIP, SRIF, CRF, GRF, and leu-enkephalin. Moderate to very strong responses were found with anti-CCK/gastrin, -substance P, and --MSH sera. Immunopositive reactions were usually observed in the entire CNS (except, until now, in neurosecretory cells, type II, in nuclei 20, and in nerve fibres located in the infracerebral neurohemal area). The immunoreactivity was, however, more or less abundant according to different CNS regions. For example, it appeared that the immunostaining for CRF is more important in the VNC while the leu-enkephalin family is more abundant in the brain (particularly in fuchsinophilic neurosecretory cells, type I, in nuclei 20). Moreover, several vertebrate type peptides (such as CRF/GRF and CCK/gastrin) may coexist in a single neurone. Several antisera may elicit a positive reaction in some specific area (for example, substance P in the nuchal organ; SRIF in oocytes; CCK/gastrin in the gastrointestinal tract).Nothing is known about the role of the different substances immunologically detected in Nereis. It is suggested that CCK/gastrin-, -MSHand substance P-like materials transmit external stimuli to neurosecretory centres located in the caudal part of the brain.Principal Abbreviations used ACTH adrenocorticotropic hormone - CCK cholecystokinin - CRF corticotropin-releasing factor - GRF growth hormone-releasing factor - LH-RH luteinizing hormone-releasing factor - MSH melanocyte-stimulating hormone - sP substance P - SRIF somatotropin release-inhibitory factor - VIP vasoactive intestinal peptide - AE anterior eye - AG anterior group - CA corpora allata - CC corpora cardiaca - CNS central nervous system - CP corpora pedunculata - EP epidermis - ICR infracerebral region - MG medial group - n nerve - NO nuchal organ - NP neuropile - OC optic commissure - Oo oocyte - PE posterior eye - PF paraldehyde fuchsin - PF⁺ fuchsinophilic - PF^- not fuchsinophilic - Pn palpal nerve - S septum - VNC ventral nerve cord The roman and arabic numerals respectively refer to different nerves and nuclei     

Mechanisms of Müller glial cell morphogenesis

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Influence of the age of algae fed to rotifers (Brachionus plicatilis O.F. Müller) on the expression of mixis in their progenies

Summary The sequence of the appearance of mixis in the rotifer Brachionus plicatilis was followed among the descendents of amictic rotifers transferred from a high salinity media (40 S) to a low one (9 S). All the neonates that hatched from the amictic eggs, after being transferred to a low salinity, were amictic. Each one of these neonates was cultured individually and its offspring removed periodically every 8–10 h. It was observed that throughout their reproductive phase, these parental females retained their potential to produce either mictic or amictic offspring. All the first produced neonates developed into amictic females, but among those produced later, three patterns were prevalent. The prevalent pattern (type A) was one in which the probability of a neonate being mictic increased towards the middle of the parents' reproductive phase and was followed by a slow decline. In the second pattern (type B), the probability of a daughter being mictic was constant throughout the parents' reproductive phase. It is suspected that the quality of food supplied to the rotifers determines the appearance of patterns, A, B or C. It is postulated that the innate capacity of rotifers to undergo mixis is genetically controlled, while its expression is modulated by environmental conditions.     

The general biology of Verruca stroemia (O. F. Müller). III. Seasonal changes in body weight and biochemical composition

The seasonal changes in body weight, DNA, total carbohydrate, total lipid, and two nitrogen fractions are described for Verruca stroemia (O. F. Müller). Events are dominated by the fact that the spring brood is virtually synchronous throughout the population. Values for all the above rise during the autumn and early winter and fall at copulation during February as the animals are fertilized. Subsequently there may be some storage of nutrients which is later utilized. In general, there are only small changes in all these constituents during the summer. Although this species has escaped from the limitation of a single annual brood the seasonal changes in weight and composition closely resemble those in Balanus balanoides and B. balanus although their phasing is different.