Annual,semilunar, and diel reproductive rhythms in the Hawaiian labrid Thalassoma duperrey

In September 1978, 5 034 juvenile western rock (spiny) lobsters (Panulirus cygnus George) were tagged on a shallow coastal reef near Cliff Head in Western Australia. Of these, 26% were recaptured and removed from the population during the subsequent commercial fishery between 15 November 1978 and 30 June 1979. A resurvey of the tagging site in September 1979 found that size structure of the population was similar to the tagged population in September 1978 but that the 1979 population was composed of almost completely different individuals and only 2% of the rock lobsters tagged in September 1978 were recaught at this time. A wide range of movement was indicated by the recapture positions of 354 rock lobsters caught off the tagging site. Most travelled almost directly offshore but some also travelled offshore in a northwesterly direction. Both trends were shown in the data from the recaptures of 18 rock lobster released farther offshore from Cliff Head in September 1981, and of 19 released at a close inshore site in earlier years. Maximum offshore rates of movement of up to 622 m d^-1 were recorded for distances up to 37 nautical miles (ca. 68 km). Growth rates for the tagged individuals which moved off, and those that were caught on, the tagging site were similar and close to growth rate under optimal conditions for this species. Under the present high levels of exploitation few, if any, of the rock lobsters remain to become permanent residents in the coastal reefs. It is believed that the north-westerly movements of some of the pre-adult rock lobsters, on their way to the breeding grounds on the outer edge of the continental shelf, are due to the upstream movement of these rock lobsters in a current from the north. The north-westerly movements allow the rock lobster population increased utilization of the food supplies of the coastal area.     

Daily otolith increments and recruitment in two coral-reef wrasses,Thalassoma bifasciatum and Halichoeres bivittatus

Increments on the otoliths of two common coral reef fishes, the bluehead wrasse Thalassoma bifasciatum and the slippery dick Halichoeres bivittatus, were demonstrated by mark-recapture experiments to be daily. Otoliths were marked in two ways; by depriving fish of light, food, and temperature cycles and also by supplemental feeding in the field. Both experiments were performed in late 1980 in the San Blas Islands of Panamá. A mark corresponding to settlement of the planktonic larva onto the reef was found on the otoliths of the bluehead wrasse. This settlement mark was used to calculate the dates of settlement of a collection of juveniles of this species taken from a patch reef in the San Blas Islands of Panamá in 1981. Settlement occurred in short and irregular bursts. The number of daily increments before the settlement mark indicates a planktonic larval life of 40 to 72 d.     

Ein neuer „Meiofaunastecher” zur quantitativen Probennahme in Weichböden

During 1972 and 1973, quantitative meiofauna samples were taken by subsampling out of a bottom sampler from some parts of the Kiel Bight. A new method has been developed to operate in very soft and muddy sediments with high organic and water contents. The construction of the new instrument is described. It consists of a bottomless plexiglass box, the cover and front of which may easily be removed. It does not cause compression of the sampled sediment, and hardly disturbs it. The semi-liquid surface of the sediment is kept in place by the use of a “sledge” and a strip of cellophane tape inside the sampler. Some preliminary results from one station show a meiofauna maximum (mainly nematodes) in the subsurface layer of the sediment, but this varied from one month to the next. The water content of the sediment at another station was as high as 300%.     

Earlier sex change in infected individuals of the protogynous reef fish<Emphasis Type="Italic"> Thalassoma bifasciatum</Emphasis>

Sex allocation theory for sequential hermaphrodites predicts the size at which an individual should change sex, given the different relationships between individual size and reproductive success in the two sexes. We studied a host-parasite system where the myxozoan Kudoa ovivora infects the ovaries of the reef fish Thalassoma bifasciatum, a protogynous sequential hermaphrodite. The parasite sporulates in the hosts eggs and renders them infertile. It is thus expected to reduce the females reproductive success, and could thereby influence host sex change. We present data from marked fish we observed in the field over 4 months. The data suggest that females infected with Kudoa ovivora have a lower reproductive success, change sex earlier and at a smaller size than uninfected females. These results are in agreement with predictions from sex allocation theory, and provide the first example of a possible parasitic influence on the sex allocation of its host.Communicated by P. Heeb     

Ist der polychaet Ophryotrocha labronica ein proterandrischer hermaphrodit?

The larvae of an egg-mass of Ophryotrocha labronica differentiate into 60 to 70% males and 15 to 40% females. In the coelom of males, freely floating spermatozoa are visible at a length of 10.5 segments. Oocytes of 5 to 7 m in diameter are released into the coelom of females at 10.7 segments. Males develop the k-jaw (k=complicated) much earlier (at 12.2 segments) than females (at 16.5 segments). As described for O. notoglandulata, O. labronica bears star-shaped glands on the dorsal side of the youngest segments. Males always have more glands (4.4) than females (2.7). These glands and the different appearance of the k-jaw may be considered as sexual characters. At 13.5 segments, 60 to 70% of the males start to proliferate oocytes, thus displaying protandry. The remaining males do not undergo sex reversal and are thus categorised as stable males. The developing oocytes in the so-called secondary females are not shed but ultimately resorbed. Resorption also occurs in isolated females, which display female differentiation from the beginning. The number of glands in secondary females decreases during sex reversal to values as low as those observed in stable females. Rearing experiments revealed the secondary females to be completely infertile. Inhibition of oocyte release in secondary females is permanent, and such release cannot be induced, even by the presence of males. Self-fertilization was not observed.

---

---

Dankenswerterweise unterstützte die DFG die Untersuchung durch eine Reisebeihilfe.     

„Kochsalz verbieten?“ – ein nachdenkliches Vorwort zur Beitragsserie Regulatorische Ökotoxikologie

This series of articles titled “Regulatory Ecotoxicology” is intended to (i) elucidate the legal background, general principles and instruments of ecotoxicological risk assessment of chemicals, (ii) exemplify the thinking and functioning of regulatory decision making, (iii) illustrate the consulting and decision making processes in risk assessment of chemicals, (iv) communicate different positions on controversial regulatory topics and (v) highlight recent trends in regulatory ecotoxicology. Both discussion papers and scientific articles are contributed by authors representing all stakeholders involved (administrative bodies, industry, academia, environmental associations). The issues addressed cover all relevant substance groups, methods and regulatory instruments (biocides, plant protection products, pharmaceuticals, wastewater treatment, REACH, Water Framework Directive).     

Loxomespilon perezi — ein entoproctenfund im mittelatlantik. Überlegungen zur benthosbesiedlung der Großen Meteorbank

In dredge-hauls on the Great Meteor Seamont (Canary Basin), the loxosomatid entoproct Loxomespilon perezi Robin et Prénant has been found growing under the elytra of the aphroditid polychaete Sigalion squamatum; L. perezi was attached to the dorsal surface of the polychaete. This is the third find of Loxomespilon, a genus first described from the coastal waters of Bretagne (France) and later from the Plymouth region (England); in all 3 places Loxomespilon was associated only with sigalionid polychaetes as hosts. The question of specificity in the host relationship of Loxosomatidae in general, and this genus in particular, is discussed. Because the Meteor Seamount has little primary production and a very poor fauna, which spreads sporadically over its plateau, there is believed to be little chance for the associated species of Sigalion and Loxomespilon to exist permanently on that bank. It is assumed that there must be a faunal reservoir in the surrounding deep sea. The possible pathways of benthos settlement on the Great Meteor Seamount are discussed.     

Domorganus oligochaetophilus n. sp., ein endoparasitischer Vertreter der Nematoda Adenophorea im darm von oligochaeten aus dem litoral der Kieler Bucht

Domorganus oligochaetophilus n.sp., a new representative of the Cylindrolaiminae Micoletzky (1922) sensu De Coninck (1965) is described. The adults live as endo-parasites in the intestine of littoral oligochaetes (Lumbricillus lineatus O. F. Müller 1774) from the Kieler Bucht (western Baltic Sea). This is the first endo-parasitic record in marine invertebrates of the Nematoda Adenophorea. The new species is characterized morphologically by: 4 cephalic setae, a very small buccalcavity without any sclerotized structures, an esophagus, with 2 bulbs, an excretory pore located posterior to the esophagus, reflexed diorchic ovaria, outstretched diochic testes, and 1 vesicular pre-anal organ in the male. Observations on living specimens show that the parasites live free in the intestinal lumen or are fixed by their spinneret glands at the intestinal wall of their hosts. Their food consists apparently of particulate intestinal contents.     

Heimfindevermögen von Aalen Anguilla anguilla nach Beeinträchtigung des Geruchssinnes,nach Adaptation oder nach Verpflanzung in ein Nachbar-Ästuar

Homing has been studied in 1,057 tagged eels Anguilla anguilla L. In a number of these eels the olfactory sense was obstructed by means of plugs inserted into all olfactory orifices. After transplantation over a distance of about 8 km, 12% of the 1968 released eels and 3% of the 1967 liberated specimens were recaptured. More than 80% of these eels homed, and no significant difference occurred between normal eels and those with obstructed olfactory system. Similar homing results, with a lower recapture rate of 2.6%, were observed in eels transplanted over a distance of about 70 km. As a control, eels were released within the original area of capture, and they did not leave their home distinct; of these, 12.1% of olfactorily impaired specimens and 22.2% of untreated eels were recaptured when fyke nets prepared with bait were used; however, when fyke nets without bait were used, 14.9% impaired, and 17.0% untreated, eels were recaptured. This result suggests the eel's dependence upon its olfactory sense in its search for food. In a further experiment, 105 eels were transplanted over a distance of about 70 km from salinities of about 15‰ to more than 30‰, and allowed to adapt for a period of 4 weeks; 3 specimens homed. This fact probably indicates that, provided the adaptation time is long enough, eels do not use salinity or other environmental factors (e.g. temperature or light) of their home area as orientation clues. Transplantation of 172 untreated eels from the Elbe estuary to the Weser estuary resulted in a recapture rate of 12.8%, 55% of these eels were recaptured in their home estuary. This result supports the information obtained via olfactory occlusion; that, because of the out-flowing residual current of the Weser estuary, the oduur of the River Elbe could not reach the eels released in the Weser estuary.