Palp morphology in two species of Prionospio (Polychaeta: Spionidae)

The palp morphology of Prionospio fallax Söderström, 1920 from Sweden and Prionospio cf. saldanha Day, 1961 from Thailand was examined with a scanning electron microscope. Prionospio fallax was also studied in vivo using light-microscopy. Both species have grooved feeding palps, adorned with up to five ciliary characters: frontal cilia, transverse ciliary bands (or bandlets), latero-frontal cirri, lateral cilia and randomly distributed non-motile cirri. All, except the frontal cilia and non-motile cirri, are asymmetrically arranged relative to the long axis of the palps. Prionospio fallax possesses transverse bandlets and the other four groups, while P. cf. saldanha has transverse bands (consisting of several contiguous bandlets), frontal cilia and some randomly scattered cirri. Asymmetrical palp ciliation was previously only known in Marenzelleria viridis (Verril, 1873) and the genus Scolelepis Blainville, 1828. The newly recognised transverse ciliary bands and bandlets are considered to be homologous with the transverse ciliary rows found basally on the palps of Paraprionospio pinnata (Ehlers, 1901). This multistate character (named transverse cilia) may prove useful in elucidating the phylogeny of the Prionospio-complex of genera.     

Multivariate analysis of morphometric differentiation within the Laonice cirrata-group (Polychaeta, Spionidae)

Principal component, and canonical variate analysis based on six characters show that there are morphological differences between three Laonice forms (L. bahusiensis, L. sarsi, and Laonice sp.). This supports Söderström's division of L. cirrata into four species; a decision often questioned by other taxonomists. We cannot exclude the possibility that the morphological differences are caused by polymorphism or seasonal variation within a single species. There is, however, no information to vindicate this and we conclude that the three forms should be regarded as separate species until this hypothesis can be rejected.     

Ultrastructural studies of dorsal ciliated organs in Spionidae (Annelida: Polychaeta)

The distribution and structural components of dorsal ciliated organs (dco) in 15 species of the Spionidae were studied by scanning- and transmission electron microscopy. Based on the distribution patterns of dco, the investigated species are divided into four non-systematic groups: (I) paired anterior dco, (II) paired dco extending posteriorly for several chaetigers, (III) paired anterior dco in combination with unpaired, sexually dimorphic, metameric dco, and (IV) paired anterior dco in combination with paired, metameric dco. Previous ultrastructural studies have only included species possessing organs of groups I and III. In the present investigation the ultrastructure of dco found in Laonice bahusiensis and Spio cf. filicornis (species with dco of groups II and IV) is studied in an attempt to consider their homology. Apart from the metameric dco of group III, similarities of the cellular components of the dco indicate a homology to nuchal organs.     

Marenzelleria viridis (Polychaeta: Spionidae): a review of its reproduction

The features of the reproductive biology such as morphology of gametes, larval morphology, larval development and development of gametes of Marenzelleria viridis Type II from the Baltic were summarized. Further reproductive features of Baltic Sea populations are given and the purpose of the review is to account for the successful immigration of M. viridis into the oligohaline areas of the Baltic considered against a background of such variables as population density and structure, salinity, temperature, food availability, oxygen and sulphide levels. Gametogenesis started in spring. Fecundity of animals depended on salinity, temperature, age and size of worms. Mature oocytes contained large cortical alveoli not yet known for polychaetes. Animals spawned in autumn in all years of investigation. The pelagic larvae of M. viridis Type II were found mainly from September to November. Larval development depended on water temperature and lasted about 4 to 12 weeks. Successful larval development from egg to juvenile was not possible below salinities of 5, but colonization of oligohaline regions took place by larvae with more than 4 setigers or by swimming juveniles. Reproductive features of M. viridis Type II from the Baltic were compared and discussed with the results of M. viridis Type I populations from the North Sea and North America. The two M. viridis types reproduced at different time, M. viridis Type I reproduced in spring and M. viridis Type II in autumn. Both types showed also differences in larval development, gametal development and sex ratio of mature worms.     

Cladistic analysis and classification of Prionospio and related general (Polychaeta, Spionidae)

The phylogenetic relationships of Prionospio Malnigren, 1867 are estimated in two parsimony analyses. The first analysis includes type and other species of Prionospio (Prionospio) Malmgren. 1867. P. (Mitiuspio) Foster, 1971, P. (Aqiriluspio) Foster, 1971, Apopriotiospio Foster, 1969, Aitrospio Maciolek. 1981, Paraprionospio Caullery, 19 14. Streblospio Webster, 1897, Laubieriellus Maciolek, 1981, and Orthoprionospio Blake & Kudenov, 1978; all members of a group of closely related taxa. Prionospio banyulensis Laubier, 1966 is included as a separate taxon since its relationship to Priotiospio has been questioned. The single most parsimonious tree supports monophyly of a group containing P. (Prionospio), P. (Minuspio), P. (Aqirilaspio) , and Apopriotiospio.
Based on the tree topology from the first analysis, 14 species belonging to different subgenera of Priotiospio and Apopriotiospio are included in a more restricted analysis, with Orthoprionospio cirrformia Blake & Kudenov, 1978 as outgroup. Three equally parsimonious trees were obtained, differing only in the positions of Prionospio ehlersi Fauvel, 1928, Prionospio henriki Hylleberg & Nateewathana, 1990, and Prionospio rugosa Sigvaldadóttir, 1997.
The results of the two analyses are compared to earlier classifications. As support is lacking for monophyly of both subgenera P. (Minuspio) and P. (Aquilaspio) , they are synonymized with P. (Prionospio). Apoprionospio cannot be justified as a separate genus without making Priotiospio paraphyletic, and is synonymized with Prionospio. Two species, P. banyulensis and P. pilkena Wilson, 1990, are transferred to Aurospio. A checklist of species belonging to Prionospio sesu lato , together with information on type locality and location of type specimens, is included.     

Phylogeny of the mud worm genus Marenzelleria (Polychaeta, Spionidae) inferred from mitochondrial DNA sequences

The taxonomy of the cryptic morphospecies of the mud worm genus Marenzelleria is particularly difficult and the phylogenetic relationship within the genus is unknown. Herein we reconstructed the phylogeny of all five species of this genus using sequence data of three mitochondrial genes (16SrDNA, cytochrome b, cytochrome oxidase subunit I) from 104 specimens out of 26 populations. For the three invasive species of the genus, Marenzelleria neglecta, M. viridis and M. arctia , individuals from native populations as well as from recently invaded populations were included. Nuclear 18S rDNA sequences were used to evaluate the appropriate outgroup taxon among several spionid polychaete species. The results supported the monophyly of Marenzelleria , and Malacoceros fuliginosus was found to be a suitable outgroup for the analysis of the mitochondrial gene segments. All phylogenetic reconstructions revealed a basal position of M. arctia and M. wireni , which have primarily Arctic distribution, with M. arctia obtaining the most basal position. Together with the present-day distribution of the species, this indicates an origin of the genus in the Arctic region. The relationship of the species M. neglecta , M. viridis and M. bastropi could not be resolved sufficiently due to genealogical discordance that might reflect relatively young cladogenetic events.     

Fine Structure of the Phaosomous Photoreceptor in the Larvae of Polydora ligni Webster (Polychaeta: Spionidae)

Niilonen, T. 1980. Fine structure of the phaosomous photoreceptor in the larvae of Polydora ligni Webster (Polychaeta: Spionidae). (Institute of Comparative Anatomy, Copenhagen, Denmark.) — Acta zool. (Stockh.) 61(3): 183–190. Phaosomes are described in detail for the first time from the Polychaeta. They were only found in the larvae, whereas serial sections of one sexually mature adult did not reveal any. The photoreceptors of the phaosomous type are placed between the medial and lateral pigmentcup eyes. The distal part of the cell is in direct contact with the epidermal surface, whereas the proximal part rests on a basement membrane. The largest diameter of the spherical cell is 10 μm. In the area immediately around the phaosome very few pigment-granules are found. The body of the phaosome is dominated by the visual vacuole, which is totally occluded by numerous intertwining microvilli. The length of the microvilli is at least 5 μm. The cytoplasm around the visual vacuole is restricted to a narrow bordering zone. A presumed chemoreceptor is found in close association with the phaosome.     

A New Species of Lumbrineris (Polychaeta) and a New Subspecies of Lumbrineris scopa Fauchald from the Coast of Norway

Lumbrineris magnidentata sp.n. was found along the coast north to Moldø. The species is characterized by black acicula, simple hooded hooks starting on parapod 1–9, and maxillary formula 1–4–2–1. Lumbrineris scopa aequilobata subsp.n. was found along the coast north to Namsenfjord. Its main distribution is in the SE of Norway. The subspecies is characterized by prolonged presetal and postsetal lobes in posterior segments. Only the postsetal lobe is elongated in the main species. No intermediate forms were found. The joint occurrence of both subspecies in two localities in Western Norway indicates that they are not totally separated geographically.     

An Electron Microscopic Study of Spermatogenesis in Marenzelleria viridis (Verrill, 1873) (Polychaeta; Spionidae)

Abstract Spermatogenesis in Marenzelleria viridis was studied by ultrastructural investigation. The testes are formed on the greatly ramified nephridial blood vessel and are enveloped by a thin layer of peritoneal cells. The spermatogonia vary in shape, are about 10 μm in diameter and are not linked by intercellular bridges. Pairs or tetrads of spermatocytes connected by intercellular bridges float freely in the coelomic cavity. A complex acrosome is produced by a Golgi complex. The acrosome consists of four to five different structures, forms cisternae and, in the mature spermatozoon, lies deep in an invagination of the nucleus. Two centrioles are also situated in a deep centriolar fossa, the proximal centriole being perpendicular to the distal one. The mature spermatozoon is an ect-aquasperm measuring about 5 μm in length and 2.5 μm in width. The midpiece consists of five spherical mitochondria arranged around the axoneme behind the nucleus. The axoneme is connected to the plasma membrane by a satellite complex. The microtubules of the flagellum are arranged in a typical 9 × 2 + 2 configuration. The spermatogenesis and the sperm morphology of M. viridis were compared with those of other members of the family Spionidae. Copyright © 1996 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.     

Ultrastructural investigations on the cephalic and metameric nuchal organs of Spio cf. filicornis (Polychaeta, Spionidae)

The nuchal organs of Spio cf. filicornis from northern Europe have been studied by scanning and transmission electron microscopy. Spio cf. filicornis is the first species in which metameric nuchal organs are described. The nuchal organs consist of a distinct cephalic nuchal complex followed by metameric structures for a variable number of chaetigers. Their microanatomy corresponds to the general structural plan of nuchal organs: these are ciliated supporting cells and bipolar sensory cells with sensory cilia traversing an olfactory chamber. The organs are overlaid by a secondary paving-stone-like cover and innervated by longitudinally elongated paired nuchal nerves. The findings clearly favour the hypothesis that the paired metameric ciliated structures found in some Spionidae are in fact homologous with the prostomial nuchal organs characteristic of Polychaeta.     

Three New Species of Cyphellophora (Chaetothyriales) Associated with Sooty Blotch and Flyspeck

The genus Cyphellophora includes human- and plant-related species from mammal skin and nails, plant materials, and food. On the basis of analysis of ITS, LSU, TUB2 and RPB1 data and morphological characters, three new species, Cyphellophora phyllostachysdis, C. artocarpi and C. musae, associated with sooty blotch and flyspeck disease, were added to this genus. The 2D structure of ITS1 and ITS2 confirmed this taxonomic status. Pathogenicity tests on apple fruit indicated that C. artocarpi could be a sooty blotch and flyspeck pathogen of apple.     

Inhibition of larval recruitment of ARmandia sp. (Polychaeta: Opheliidae) by established adults of Pseudopolydora paucibranchiata (Okuda) (Polychaeta : Spionidae) on an intertidal sand flat

Inhibition of larval settlement by a dense assemblage of established adults was examined by observing natural and experimental abundance patterns of two polychaete species on an intertidal sand flat in west Kyushu, Japan. A cage left for 43 days in the field in spring-summer brought about a remarkable increase in the within-cage density of adults of the tube-building spionid polychaete Pseudopolydorapaucibranchiata (Okuda) as compared with the density in an uncaged plot (× 52). In contrast, the densities of juveniles of the burrowing opheliid polychaete Armandia sp. showed an inverse trend (× $\text{1}\text{22}$). The attractiveness of the within-cage sediment for settling larvae of Armandia (cage-induced artifact) was assessed in a laboratory experiment: given an alternative choice between the sediments from the cage and the uncaged plot, Armandia larvae produced by artificial fertilization showed no substratum-preference. In another laboratory experiment, it was confirmed that Pseudopolydora paucibranchiata adults at a density of only $\text{1}\text{30}$ of that in the cage exerted a great lethal effect (probably ingestion) on Armandia larvae. These two results strongly support the hypothesis that the low density of Armandia juveniles in the cage was induced not through avoidance of the cage sediment by the larvae themselves but through inhibition of recruitment by the dense assemblage of established Pseudopolydora paucibranchiata adults in the cage. Moreover, the natural abundance pattern of Armandia juveniles in summer could partly be explained in relation to spatial and temporal changes in the density of Pseudopolydora paucibranchiata adults.     

Spermatogenesis and sperm ultrastructure in three species of polydora and in streblospio benedicti (Polychaeta: Spionidae)

Summary Spermatogenesis was studied at the ultrastructural level in Polydora ligni, P. websteri, P. socialis and Streblospio benedicti. Spermatogonia, spermatocytes, spermatids and mature sperm are described. In all four species, meiosis occurs in the coelom following release of spermatogonia from the gonad. In Polydora spp., chromatin condensation is lamellar with no microtubules present during nuclear elongation. In S. benedicti, chromatin condensation is fibrous with a manchette of microtubules present around the nucleus. In all four species, the acrosome forms from a Golgi-derived vesicle situated at the base of spermatids. The acrosome in Polydora spp. is conical with a distinctive substructure whereas the S. benedicti acrosome is long and spiral. The implantation fossa is short in all species except P. ligni. All four species have elongated sperm heads. The middlepiece as well as the nucleus is elongated in Polydora spp. whereas S. benedicti has a long nucleus but a short middlepiece. Platelet-shaped electron-dense bodies are present throughout the nuclear region and middlepiece of Polydora spp. and the nuclear region of S. benedicti. These membrane-bounded bodies may be energy storage organelles. The use of ultrastructural data in analysis of sibling species complexes is discussed.Contribution Number 203 from Harbor Branch Foundation, Inc.     

Growth rates of arctic juvenile Scolelepis squamata (Polychaeta: Spionidae) isolated from Chukchi Sea fast ice

In spring, Arctic coastal fast ice is inhabited by high densities of sea ice algae and, among other fauna, juveniles of benthic polychaetes. This paper investigates the hypothesis that growth rates of juveniles of the common sympagic polychaete, Scolelepis squamata (Polychaeta: Spionidae), are significantly faster at sea ice algal bloom concentrations compared to concurrent phytoplankton concentrations. Juvenile S. squamata from fast ice off Barrow, Alaska, were fed with different algal concentrations at 0 and 5?°C, simulating ambient high sea ice algal concentrations, concurrent low phytoplankton concentrations, and an intermediate concentration. Growth rates, calculated using a simple linear regression equation, were significantly higher (up to 115?times) at the highest algal concentration compared to the lowest. At the highest algal concentration, juveniles grew faster at 5?°C compared to those feeding at 0?°C with a Q ₁₀ of 2.0. We conclude that highly concentrated sea ice algae can sustain faster growth rates of polychaete juveniles compared to the less dense spring phytoplankton concentrations. The earlier melt of Arctic sea ice predicted with climate change might cause a mismatch between occurrence of polychaete juveniles and food availability in the near future. Our data indicate that this reduction in food availability might counteract any faster growth of a pelagic juvenile stage based on forecasted increased water temperatures.     

Laboratory studies on larval growth ofPolydora ligni,Polydora ciliata,andPygospio elegans (Polychaeta,Spionidae)

The spionid polychaete speciesPolydora ligni, P. ciliata, andPygospio elegans were cultivated in the laboratory over several successive generations. A flow-through cultivation system forPolydora spp. is described. Duration of life cycles (time from hatching of the larva to first reproduction) and life spans (hatching to death) of these species were not significantly influenced by the degree of inbreeding nor by individual age of the parents. Minimum time from metamorphosis (15-setiger stage) to first hatching of offspring larvae (in the 3-setiger stage) at 18°C was 33 days inPolydora spp. and 81 days inPygospio elegans. Larval growth patterns are described in terms of number of setigers, body length, and biomass (dry weight, carbon, nitrogen, hydrogen), in relation to time after hatching. Regression models are proposed which link these measures of larval growth and, thus, may be used for conversions. Rates of development and growth show a high degree of variability in all three species, not only caused by variation in environmental factors such as temperature or food, but also among and within single hatches of larvae reared under identical conditions. Larvae were reared at constant temperatures (6°, 12°, and 18°C). Temperature affected larval growth inPolydora ligni more than inP. ciliata, and least of all inPygospio elegans. Only the latter species was able to develop at 6°C from hatching to metamorphosis. This differential response may be explained by differences in the natural spawning season of these species. Eleven phytoplankton species were tested as to their food values. A relative index of growth is proposed which compares the slopes of two growth curves (one standard and one test condition). The flagellateDunaliella tertiolecta was used as a standard food in these experiments. Most algal species were less suitable, and only the diatomThalassiosira rotula was consistently better food for spionid larvae thanD. tertiolecta.