Andreas Bick

History and Success of an Invasion into the Baltic Sea: The Polychaete Marenzelleria cf. Viridis, Development and Strategies

In the mid 1980s, a new polychaete appeared in coastal waters of the Baltic Sea and rapidly became an important faunistic element. The identification of this spionid as Marenzelleria cf. viridis indicated North America as the most likely area of origin. The history of invasion into the Baltic Sea is outlined. Sound taxonomic experience and competence was and is necessary to elucidate the background when dealing with bioinvasions. A review of taxonomic problems of the genus Marenzelleria is given. Based on long time series we could draw a picture on the species strategy in stressed habitats. Three coastal areas were selected to demonstrate the role of environmental factors facilitating Marenzelleria invasion in the Baltic Sea in the last decade. This review deals with the expansion and niching of an allochthonous species and its influence on the indigenous macrozoobenthos. Both the life history and physiology of Marenzelleria make it well adapted to life in brackish water conditions, occupying a niche in an environment with low species diversity.

COMPONENT COMMUNITY OF LARVAL TREMATODES IN THE MUDSNAIL HYDROBIA VENTROSA: TEMPORAL VARIATIONS IN PREVALENCE IN RELATION TO HOST LIFE HISTORY

Temporal variations in the prevalence of larval trematodes in the short-lived prosobranch mudsnail Hydrobia ventrosa (Montagu) were investigated in relation to host life history and season for 4 successive years in temperate windflats of the southern Baltic Sea. The component community of trematode larvae in H. ventrosa comprises at least 10 species; families (and species) represented include Notocotylidae (1), Echinostomatidae (1 or 2), Heterophyidae (2), Monorchidae (1), Microphallidae (3 or 4), Psilostomatidae (1), and Hemiuridae (1). The notocotylid Paramonostomum alveatum was the most prevalent species, followed by the microphallids Maritrema subdolum and Microphallus sp. Trematode prevalence in H. ventrosa fluctuated seasonally. Prevalence usually peaked in summer between July and September–October and decreased in late winter–early spring. This seasonal change is chiefly explained by the life history patterns of the semelparous snail host. Hydrobia ventrosa has a maximum life span of about 2 yr and reproduces between June and November of its second calendar year. The first trematode infections appeared annually in May when the most abundant cohort of H. ventrosa, the second-calendar-year snails, mature. The prevalence continued to increase until August–September, throughout the reproductive period of the second-calendar-year snails. Prevalence decreased during winter, when most of the second-calendar-year snails died after reproduction. On the basis of long-term laboratory experiments, it has been shown that the late autumn–winter mortality was not the result of trematode infections. Seasonal patterns of prevalence were similar among the trematode species except for the monorchid Asymphylodora demeli, the only one using fish definitive hosts. Species-specific differences in the seasonal occurrence of prepatent infections and the predominance of certain larval stages in winter are interpreted as different strategies of the trematode species to survive the harsh winter conditions, or to survive the death of the first intermediate host in autumn–winter, or both.

On the identity and distribution of two species of Marenzelleria (Polychaeta, Spionidae) in Europe and North America

Discrepancies are known to exist between the reproduction biology and population genetic of various Marenzelleria spp. populations in North American regions and in the North Sea and Baltic Sea. Species identification is difficult, and their geographical distributions are far from clear. As the diagnostic features of the species are known to vary with growth, it was necessary to find some reference frame within which morphological differences could be understood. The total number of setigers of intact specimens and the total number of branchiate setigers of anterior fragments proved to be suitable parameters permitting morphological differentiation between previously genetically distinguished forms. The forms corresponded in several features to literature diagnoses of M. wireni and M. viridis. Additional features were found to facilitate reliable morphological differentiation between the two species. It was shown that the range of distribution of M. cf. wireni is restricted primarily to mesohaline to polyhaline regions (including the North Sea), whereas M. cf. viridis is found predominantly in oligohaline to mesohaline areas (including the Baltic Sea). This applies also to North American and, possibly, polar waters. The discovery of M. cf. viridis in an oligohaline reach of the Elbe estuary shows that the two species can exist parapatrically, at least in North Sea estuaries. Besides these two species, a third was found to occur sympatrically with M. cf. viridis in a North American estuary (Currituck Sound). No description of this species has been given as the specimen consisted only of an anterior fragment.

A loss of fecundity in a population of mudsnails Hydrobia ventrosa caused by larval trematodes does not measurably affect host population equilibrium level

Host snail demography and trematode parasitism were followed for one host generation in a shallow brackish lagoon of the western Baltic Sea. In addition, a laboratory experiment was simultaneously conducted to quantify the effects of parasitic infection on host fecundity. Hydrobia ventrosa of the cohort of 1996 had a maximum life-span of up to 2 years and reproduced between May and November of their second calendar year in 1997. Snails died after reproduction. The first trematode infections appeared in May 1997 when the snails started to mature. Total trematode prevalence peaked in summer and declined during winter to the lowest level in early spring 1998. Eight taxa of larval trematodes were found. Egg production of females with trematode infections was significantly reduced. Among females with pre-patent infections, about 20% were still able to produce eggs. Among females with patent infections merely 9% could lay eggs, compared to an average of about 51% in uninfected females. Taking into account a summer prevalence of about 25%, parasitic infections caused an overall reduction in egg production of the snail host population of about 15%. The reduction in host fecundity as a result of larval trematode infection did not measurably affect the population dynamics of H. ventrosa, because other environmental factors, especially winter severity and available food supply, were concluded to be much more relevant.

Spionidae (Polychaeta: Canalipalpata: Spionida) from seamounts in the NE Atlantic.

Spionidae (Polychaeta) collected from seamounts in the Atlantic Ocean were studied. Altogether six species were found of which two are new to science and one belongs to a new genus. Aonidella cf. dayi Maciolek in López-Jamar, 1989 and Glandulospio orestes gen. et sp. nov. were the most common species and occurred on both the Great and Little Meteor Seamount, the Irving Seamount and the Hyeres Seamount. Laonice norgensis Sikorski, 2003 and Malacoceros jirkovi Sikorski, 1992 have a wider distribution in the North Atlantic, including the Mediterranean Sea in case of L. norgensis. Aonides selvagensis Brito, Núñez and Riera, 2006 is only known from the Macaronesian Region. Dipolydora paracaulleryi sp. nov. has been collected from both the Great and Little Meteor Seamounts. All species are compared with morphological similar species and their taxonomy is discussed. Detailed descriptions are provided for the species new to science and descriptions of the previously known species are amended. Accompanying histological studies revealed the presence of very strong dorsoventral musculature in A. cf. dayi and for G. orestes gen. et sp. nov. the presence of glandular organs in the middle body region. Laonice maciolekae Aguirrezabalaga & Ceberio, 2005 was found to be a junior synonym of L. appellöfi Söderström, 1920 and is formally synonymised. Molecular data suggest gene flow between seamounts and autochthonous as well as allochthonous larval recruitment for different species. The results of previous studies by other authors, that polychaete communities of the North Atlantic Seamounts are characterized by low diversity, low rates of endemism, and the predominance of widely distributed (and cosmopolitan) species is not corroborated by our results.xa0

Polychaete communities associated with gastropod shells inhabited by the hermit crabs Clibanarius erythropus and Calcinus tubularis from Ibiza, Mediterranean Sea

Shells inhabited by hermit crabs are unique microhabitats with an abundant epi- and endofauna. Using polychaetes as an example, communities associated with the whelk Stramonita haemastoma , the hermit crabs Clibanarius erythropus and Calcinus tubularis , as well as empty, damaged shells were investigated. No polychaete community was associated with live S. haemastoma : only 30% of the investigated gastropods harboured polychaetes. Hermit crab-occupied shells supported polychaete communities dominated by Spirorbidae in the case of Clibanarius erythropus and by small Sabellidae, Spirobranchus polytrema and Dipolydora armata in Calcinus tubularis . The polychaete fauna associated with empty shells was similar to that on shells previously inhabited by one of the hermit crab species but different from those of the surrounding hard bottom. The reproductive strategy of the some polychaetes species is adapted to life on this small-sized habitat.

Histological and ultrastructural reconstruction of ventral epidermal glands of Spio (Polychaeta, Spionidae, Annelida)

With present study, we confirm that the ventral structures on anterior and middle chaetigers of two species of Spio are special kind of intraepidermal multicellular glands. The general anatomy and coherence morphology of these ventral epidermal glands (VEGs) were 3D-reconstructed based on semithin section series. Specific anatomical characters were explored using electron microscopy, such as scanning electron microscopy for characterization of gland pores and transmission electron microscopy for investigation into cytoanatomical details. The VEGs are tubular or acinar; their pores are spherical or lens-shaped. The glands consist of three cell types: secretory cells, sheath cells and canal cells, forming and strengthening the short gland duct and the pore region. The secretory cells are tightly packed into a single-layered, curved glandular epithelium. Secretory cells are separated from each other by thin projections of interstitial sheath cells. The apices of the secretory and sheath cells surround a tubular or vase-shaped extracellular space, the reservoir. The reservoir is traversed by microvilli of the secretory and sheath cells. Two sorts of microvilli characterize the apex of secretory cells: slender, elongated ones located at the periphery (outer microvilli), and shorter but thicker ones, arranged in a distinct collar in the centre (inner microvilli). Secretion, encased in regular secretory granules and discharged only at the apex’ centre, is guided through the space enclosed by the collar of inner microvilli. Though also consisting of numerous cells, the VEGs of Spio spp. are not comparable to parapodial glands described in other spionid taxa since they remain in a strictly intraepidermal position, are distant from parapodia and contain sheath cells. Nonetheless, the VEGs are very helpful for taxonomic work on representatives of the genus Spio and closely related genera.

A contribution to the taxonomy of Spio (Spionidae, Polychaeta, Annelida) occurring in the North and Baltic Seas, with a key to species recorded in this area

In order to resolve taxonomic problems known from literature and diagnostic practices, Spio species currently recognised in the North Sea and the Baltic Sea have been re-examined. Spio species recorded in the area of interest are S. decoratus, Spio cf. filicornis, S. goniocephala, S. martinensis, and S. armata. Spio decoratus is restricted to the North Sea, whereas S. armata occurs only in the Baltic Sea. Revised descriptions with illustrations and notes on the distributions, as well as remarks on size-dependent differences of characters, are presented for all species. Specimens of Spio from the North and Baltic Seas, which are assigned to S. filicornis based on current taxonomic literature, exhibit significant morphological differences, and are here regarded as two different species. A definite assignment of specimens from the two morphological distinct groups to one of the known Spio species was impossible based on the material available. The significance of diagnostic characters used for the identification of Spio spp. is discussed. An identification key to Spio species found in the investigation area is provided.

Redescription of P. dorsipapillatus (von Marenzeller, 1893) and additional comments on the other species in the genus Pholoides Pruvot, 1895 (Polychaeta: Sigalionidae)

Pholoides Pruvot, 1895 is a species-poor genus of small scale-bearing polychaetes. Pholoides species are restricted to the continental shelf, living in sandy and muddy substrates, or on hard bottoms. During the DIVA 3 expedition grab samples were taken on four seamounts of the Meteor Seamount complex. One of the most common polychaetes in these samples was P. dorsipapillatus (von Marenzeller, 1893). Based on this material a comparison with the type material is undertaken leading to a re-description of P. dorsipapillatus. Diagnostic characters of all accepted Pholoides species were evaluated using light, scanning electron and confocal laser scanning microscopy. CLSM in particular proved to be an excellent tool for investigating these small species, and especially the type material. Blossom-like sensory buds, found at certain appendages of P. dorsipapillatus, could be an important diagnostic character to distinguish P. dorsipapillatus from other Pholoides species. Sequence information on three different gene fragments, the mitochondrial COI and 16S and the nuclear H3a, were obtained, and could serve for future phylogenetic and phylogeographic studies.

Description of a new species of Sabellidae (Polychaeta, Annelida) from fresh and brackish waters in Europe, with some remarks on the branchial crown of Laonome

In 2009, a hitherto unknown Laonome species was found in the Canal Ghent-Terneuzen in the Netherlands and subsequently in other Dutch rivers, canals and estuaries. A few years later, more unknown Laonome specimens were found in the eastern part of the Baltic Sea and in the Don River estuary, Sea of Azov. Initially, it was assumed that these specimens could represent Laonome calida Capa, 2007, originally described from Australia. In the present study we examine all these unknown European Laonome specimens and compare these specimens with the type material of L. calida from Australia. This lead to two main results: First, all specimens from Europe have the same diagnostic characters and therefore belong to one species. This finding was also supported by the results of a correspondence analysis, and genetic analyses using four different DNA sequences (COI, 16S, 28S). Second, it turned out that the type material of L. calida contains two morphologically distinct groups of specimens. The holotype and 7 paratypes are similar to each other but differ significantly from the other also similar 16 paratypes, and from all European specimens. On the basis of these observations, the Laonome specimens from European waters are described here as L. xeprovala sp. nov. We also provide the characters of the branchial crown of three Laonome species for a prospective revision of this genus.