Kurt W. Ockelmann

The biology, ecology and behaviour of the Bivalve Mysella bidentata (Montagu)

Abstract Mysella bidentata is a euryvalent species. Its distribution in the N. Oresund 3-4 months after settling is positively correlated with the density of adult Amphiura filiformis. In the laboratory, Mysella prefers to live in the oxydized layers around the burrow of Amphiura. Dense Amphiura populations enlarge the water-sediment interface and thereby the oxydized layers and the microbial activity. This benefits Mysella which obtains protection from surface-hunting predators and additional supply of food. In their second year the bivalves are functional males, and when three years old and 3 mm long they are hermaphrodites. Males produce fertile and oligopyrene sperm simultaneously. Sperm transfer involves sperm bags and receptacula seminis, and is thus time-independent of egg-spawning. Mysella reacts to gravitation by positive or negative taxes, and to direction of water flow by positive tropo-taxis or compass reactions. Chemical stimuli from a predator (Astropecten) evoke direct orthokinesis. Stimuli...

On the biology of the polychaete Glycera alba, especially its burrowing and feeding

Asbtract Immature individuals of G. alba are predators waiting for prey while resting in their burrows. These are constructed of tubes serving different purposes. The species performs two types of burrowing movements, viz. proboscideal and parapodial-peristaltic burrowing. Chemical stimuli were found to be insufficient to evoke feeding behaviour in the worm. Observations show that receptors in the prostomial-peristomial region perceive pressure waves emitted by the prey and thus aid in prey detection and finding. Whether or not feeding behaviour can be induced in Glycera depends on the state of stimulation of other receptor systems. The spectrum of prey species is very broad predominantly consisting of unprotected invertebrates which move on or in the surface layer of the sediment. Feeding rate in nature seems to be half of maximum feeding, or less. Experimental data on growth indicate that G. alba has a potential for fast growth and very high growth efficiency, combined with very low maintenance requirem...

An improved detritus-sledge for collecting meiobenthos

Abstract A simple detritus-sledge for collecting animals of the meio- and small macrobenthos from level sea-bottoms is described and figured. Its high degree of efficiency - due to a chain which stirs up the surface of the bottom ahead of the net-opening - is exemplified.

Turtonia minuta (fabricius), a neotenous veneracean bivalve

Abstract The systematic position of Turtonia minuta has till now remained uncertain. However, as demonstrated in a series of comparisons, it exhibits strong affinities with the Veneracea. Similarity is particularly close with the spat of Venerupis, so that Turtonia may be said to resemble a juvenile of Venerupis which has become sexually mature just before formation of the inhalant siphon and outer demibranchs. It is concluded, therefore, that Turtonia should be included in the Veneracea and given a systematic position close to Venerupis. Specialized features in Turtonia are related largely to its attached mode of life in the intertidal zone and very shallow water, and also to its mode of reproduction. The main steps in the formation of its egg-capsules, which were found to be attached to modified byssus threads, are deduced from preserved material. An account of relevant information provides evidence that, in contrast to current views, the typical bivalve mantle inner fold has become duplicated in the Ve...

Life on wood – the carnivorous deep-sea mussel Idas argenteus (Bathymodiolinae, Mytilidae, Bivalvia)

Abstract Deep-sea mussels associated with sunken wood are less well known in terms of anatomy, biology and evolution than their bathymodioline allies from cold seeps and hydrothermal vents. During the Danish ‘Ingolf Expedition’ (1895–96) to the Northeast Atlantic, two pieces of pinewood were collected from a depth of 1836 m. The wood was inhabited by several hundred individuals of the deep-sea mussel Idas argenteus and the wood-boring pholadid Xyloredo ingolfia. Idas argenteus is the type species of its genus and differs from some of the species until now referred to Idas by having gill filaments like those of suspension-feeding mytilids, with no abfrontal tissue adaptation for symbiotic chemo-autotrophic bacteria. The adaptations in I. argenteus to capture prey as well as the reproductive pattern of the prey, Xyloredo, and its functional dwarf males are described. The population dynamics and adaptation to an ephemeral habitat in the deep sea of both species are described herein. Although larviphagi is known to occur in some filter-feeding bivalves, Idas argenteus is the first mytilid known to be specifically adapted to a carnivorous life. Further, it is argued that the modifications of I. argenteus with regard to its shell development, alimentary system, gill anatomy and life habits provide important clues to the evolution of the Bathymodiolinae.

Beat frequency of lateral cilia in intact filter feeding bivalves : effect of temperature

Abstract The beat frequency of the lateral cilia was measured stroboscopically in young transparent specimens of the bivalves Abra nitida, Abra alba, Spisula subtruncata, Corbula gibba, Mytilus edulis and Cultellus pellucidus. The beat frequency was uniform among the species, amounting to about 10 Hz at 14°C, which was about the temperature they were adapted to in nature. Frequencies were higher at 20–21°C, corresponding to a Q10 value of 2 to 3. Beating stopped abruptly at valve closure. Abrupt stoppage of beating also occurred at closure of the aperture of the exhalant siphon in the absence of valve closure. At relaxation of the sphincter the cilia resumed beating equally abruptly.

Descriptions of mytilid species and definition of the Dacrydiinae n. subfam. (Mytilacea-Bivalvia)

Abstract Ten mytilid species are described as new, viz. Modiolus (Modiolus?) nicklesi (tropical W. Africa), M. (M.) pseudobarbatus (tropical W. Africa), M. (M.) thorsoni (tropical W. Africa), Musculus (Musculus) koreanus (Sea of Japan), Rhomboidella obesa (tropical W. Africa), R. malaccana (W. coast of Thailand), Xenostrobus mangle (W. coast of Malaysia), X. balani (W. coast of Thailand), Dacrydium angulare (S. Atlantic), and D. viviparum (Reykjanes Ridge). The latter species has suprabranchial protection of embryos as does the Mediterranean D. hyalinum (Monterosato). Modiolus lulat (Dautzenberg, 1891) is regarded synonymous with M. martorelli (Hidalgo, 1877), and Vignadula Kuroda & Habe, 1971, with Xenostrobus Wilson, 1967. — The descriptions include anatomical and biological notes for several of the species. — The so-called ‘periostracal’ hairs of mytilids are concluded to be secretions of byssus glands, shaped and applied to the shell exterior by the foot of these bivalves. — It is pointed out that the...

Ophryotrocha socialis n. sp., a link between two groups of simultaneous hermaphrodites within the genus (Polychaeta, dorvilleidae)

Abstract Ophryotrocha socialis n. sp. is described from laboratory cultures. Its requirements are those of a boreal and opportunistic species which does not survive at salinities below 20-25‰. It is a simultaneous hermaphrodite combining traits which otherwise are restricted to two different species groups of Ophryotrocha with the same type of sexuality. The new species lives gregariously in tube systems and is capable of homing. Its eggs are not shed in a matrix. Connected with this are specialized brood care, facultative external self-fertilization and a high level of inbreeding. Feeding and spawning in the species are inhibited by light.

Taxonomy of and biological notes on the bivalve genus Microgloma, with comments on protobranch nomenclature

Abstract The protobranch bivalve genus Microgloma Sanders & Allen, 1973 includes 3 or 4 minute species, shell length 0.85–1.1 mm. They are progenetic and their systematic position proposed herein, in the Nuculanidae (Nuculanoidea), is concluded from their similarity to young specimens of that family and sperm morphology. The genus was hitherto classified in Pristiglomidae (Nuculoidea). Microgloma pusilla (Jeffreys, 1879) occurs on the European continental shelf and slope from Iceland and Norway to the Mediterranean Sea at depths between 200 and 1200 m. Microgloma lumidula (Monterosato, 1880) (new synonym: M. lumerae Sanders & Allen, 1973) occurs from the Bay of Biscay and the Mediterranean Sea to the Canary Islands at depths between 200 and 2351 m. Phaseolus guilonardi Hoeksema, 1993 from the Netherlands and Atlantic France, is tentatively included in Microgloma (new combination). A few live M. pusilla were kept in the laboratory for nearly four years and the development of five young born there, was foll...

On the biology of the prosobranch Lacuna Parva in the Øresund

Abstract The habitats of 2 sparse populations of Lacuna parva in the northern Oresund are described. The species was cultured throughout its life cycle. It feeds on the red algae Phyllophora, Delesseria and Phycodrys. Phyllophora is the main substratum for spawn deposition. Egg masses contain up to 16 eggs, most often 6–10 eggs. Development is direct and takes ca. 2 months at 10–11 °C. Potential reproductive effort resembles that of L. pallidula and parity between spawn production and body size (measured in terms of dry organic matter) is reached after 24–39 days. After copulation females may produce fertilized eggs for 2–3 months. The species has an annual life cycle with copulation prior to the production of spawn in March–June, death of adults in May–June and main hatching of young in June–July. Differences in morphology, food plants and life cycle between populations from the Oresund and Roscoff are pointed out.