Origin of the Regeneration Blastema in Polychaete Annelids

Since the early part of this century, controversy has surroundedthe origin of the cells ot the regeneration blastema in annelids.Cells of the epidermis and reserve mesodermal cells have eachbeen thought to form the entire blastema. With increasing frequency,it is being suggested that in numerous polychaetes each layerof tissue in the regenerate arises from the corresponding oldgerm layer. Evidence presented here from experiments utilizingtechniques of radioautography, histochemistry, X-irradiation,and electron microscopy in addition to histological observationlargely supports the last hypothesis. In the light of recentexperiments, it appears that the new epidermis and gut arisefrom the corresponding old tissue. The formation of the mesodermcannot yet be generalized, but reports indicate that it mayarise from dedifferentiated muscle cells, cells of the peritonealepithelium, and free coelomocytes.     

Inflammatory Responses in Annelids

The cellular inflammatory responses of annelids, which includechemotaxis, phagocytosis, encapsulation, and various phasesof wound healing, are effected by coelomocytes, particularlythe hyaline amoebocytes. Coelomic epithelial cells and specializednephridial cells also participate in phagocytosis. A numberof factors related to inflammation in vertebrates have beenidentified in annelids, i.e., histamine, kallikrein, lysosomalenzymes, agglutinins, lysins and antibacterial substances. However,their precise function in annelid inflammatory responses hasyet to be determined.     

Marine Polychaete Annelids of Easter Island

This study increases the number of species of marine polychaete annelids known to occur at Easter Island from 11 to 60, of which 43 are identified to species. Nearly 90% of these occur in the tropical Indo-West Pacific region, but 60% are of circumtropical distribution. The strong Indo-West Pacific zoogeographic affinity is consistent with other taxa of Easter Island inshore marine animals for which data are available, the fishes, corals, and gastropod molluscs. Polychaete species composition and abundance were determined in substrate samples from two types of microhabitat in a tidepool. A sample of 290 ml of sand and 70 ml of algae contained 1,779 specimens of 41 species of polychaetes (species diversity H′ = 2.57). A basalt boulder of surface area 340 cm² contained a polychaete assemblage of 864 specimens of 35 species (H′ = 2.49). Population density of the latter sample is equivalent to 25,400 polychaetes/m². Of the 49 species present in the two samples, 34 were identified to species. Although 27 species (55%) were common to both samples, similarity as measured by C_λ, which weighs differences in relative abundance, was only 24%. More than half of all polychaetes present in the two samples belonged to the family Syllidae; they comprised 65% of the individuals in the sand-algae sample and 35% in the boulder sample. Spirorbinae predominated numerically in the boulder sample (40%). Chaetopteridae (10%) and Spionidae (8%) were the next most abundant families in the sand-algae sample.     

Annelids in evolutionary developmental biology and comparative genomics

Annelids have had a long history in comparative embryology and morphology, which has helped to establish them in zoology textbooks as an ideal system to understand the evolution of the typical triploblastic, coelomate, protostome condition. In recent years there has been a relative upsurge in embryological data, particularly with regard to the expression and function of developmental control genes. Polychaetes, as well as other annelids such as the parasitic leech, are now also entering the age of comparative genomics. All of this comparative data has had an important impact on our views of the ancestral conditions at various levels of the animal phylogeny, including the bilaterian ancestor and the nature of the annelid ancestor. Here we review some of the recent advances made in annelid comparative development and genomics, revealing a hitherto unsuspected level of complexity in these ancestors. It is also apparent that the transition to a parasitic lifestyle leads to, or requires, extensive modifications and derivations at both the genomic and embryological levels.     

Evolution of the concepts of vitellogenesis in Polychaete Annelids

Summary

In polychaete annelids, two types of vitellogenesis have been described: a heterosynthetic mechanism (in a number of different of worms) and an autosynthetic process (other including Nereis). Recent biochemical results suggest that the heterosynthetic mechanism is more general than previously thought. In Nereis, the vitellogenin (the precursor) is synthesized in coelomocytes and after transfer through coelomic fluid incorporated into oocytes. In germinal cells, a conversion process, involving proteolytic cleavages of vitellogenin, produces mature vitellins which are accumulated in yolk granules.

The neurohormones identified so far are not essential for vitellogenin synthesis. It is possible that these neurohormones regutate enzymatic activities in the oocytes.     

The Palaeobiogeography Of Silurian Ramphoprionid Polychaete Annelids

Silurian palaeobiogeography of the Ramphoprionidae (Annelida; Polychaeta) is outlined. Members of the family are reported from northern Europe (Estonia, Sweden and England), the Russian Arctic (Severnaya Zemlya), and the Canadian Arctic (Baillie–Hamilton Island). These areas were located fairly close to the palaeoequator during the Silurian and a faunal exchange is indicated by the broad, intercontinental distribution of the family. A few taxa may, however, have been endemic. Ramphoprionids had long stratigraphical ranges and were generally fairly rare during the Silurian, infrequently exceeding ten per cent of the jawed polychaete faunas.     

Paleozoic shell-Boring Annelids and their Trace Fossils

Polychaete shell-borings are widespread but not often commonin Paleozoic strata of most continents, occurring in pelecypod,gastropod, cephalopod, coral, stromatoporoid, crinoid, brachiopod,ectoproct, and calcareous algal skeletons of Ordovician to Permianage. Four genera are known: Vermiforichnus (Spionidae), Ordovicianto Permian; Caulostrepsis (Spionidae) , Devonian to Oligocene;Myzoslomites (Myzostomidae), Ordovician to Jurassic: and possiblyConchotrema, Devonian to Permian. The Silurian Citonia siphois a worm-boring, not a calcareous worm tube, referable to Vermiforichnus. An exceedingly well preserved Devonian fossilized polychaete,Vermiforafacta rollhisi, with complex setigerous parapodia,dorsal cirri, peristomial cirri, prostomium, and tentacle-likepalps, occurs entombed in an agglutinated tube-lined worm-boring(Vermiforichnus) . It may have been a shell-borer consideringits many similarities to the spionid, Polydora, which apparentlyecologically replaced it. Like Polydora, Vermiforafacta probably filtered food and sedimentfrom sea water and constructed agglutinated tubes which linedits borings. In bivalves, borings parallel valves and are usuallyperpendicular to commissures; in massive skeletons, they radiateoutward and laterally. Distorted later growth and "blisters"indicate that the host was often alive. Commensal to pathogenicparasitism existed and worms benefited from their hosts's feedingcurrents and protective shells. One polychaete nestler is reported.Life positions of hosts are sometimes indicated.     

The Fate of [3H]Ecdysone in Three Species of Annelids

Summary

The metabolism of [³H]ecdysone was examined in 3 species of annelids: the bloodworm, Tubifex vulgaris (a freshwater oligochaete), the earthworm, Lumbricus terrestris (a terrestrial oligochaete) and the ragworm, Nereis divtrsicolor (a marine polychaete). One of these species, N. diversicolor, metabolised injected [³H]ecdysone into compounds which co-chromatographed on both reversed-phase and adsorption HPLC with authentic 20-hydroxyecdysone, 26-hydroxyecdysone and 20,26-dihydroxyecdysone, thus demonstrating the occurrence of 20-hydroxylation and 26-hydroxylation capability in the Annelida. Furthermore, [³H]ecdysonoic acid was also formed and excreted by N. diversicolor, suggesting that 26-oic acid formation is involved in ecdysteroid inactivation in this species. Other, as yet unidentified, radioactive metabolites were also excreted by N. diversicolor. Several metabolites of [³H]ecdysone were also detected in the other 2 species examined, T. vulgaris and L. terrestris.     

A phenetic and cladistic study of spermatozoal ultrastructure in the Oligochaeta (Annelids)

Spermatozoal ultrastructure of nine oligochaete families has been examined for congruence with phylogenetic and taxonomic systems for the Oligochaeta based on general morphology, particularly the holomorphological hennigian analysis of Jamieson (1978a, 1980, 1983). Estimation of congruence has been made following phenetic and cladistic (phylogenetic) analysis. Correspondence, in phenograms and phylograms, of sperm types with taxonomic and phylogenetic groupings previously recognized is generally good. Departure from this rule in the similarity of the phreodrilid sperm to that of the Lumbricina suggests a corresponding alteration of fertilization biology in the phreodrilids. The results indicate that the Haplotaxidae lie at the base of the opisthopores though they do not unequivocally contraindicate acceptance of a Haplotaxis like form as a stem form of the Haplotaxida (opisthopores and Haplotaxidae) and Tubificida. An even more basal position for prosopores, now represented by the Lumbriculida, cannot yet be dismissed.     

Okadaic Acid, an Apoptogenic Toxin for Symbiotic/Parasitic Annelids in the Demosponge Suberites domuncula

The role of okadaic acid (OA) in the defense system of the marine demosponge Suberites domuncula against symbiotic/parasitic annelids was examined. Bacteria within the mesohyl produced okadaic acid at concentrations between 32 ng/g and 58 ng/g of tissue (wet weight). By immunocytochemical methods and by use of antibodies against OA, we showed that the toxin was intracellularly stored in vesicles. Western blotting experiments demonstrated that OA also existed bound to a protein with a molecular weight of 35,000 which was tentatively identified as a galectin (by application of antigalectin antibodies). Annelids that are found in S. domuncula undergo apoptotic cell death. OA is one candidate inducer molecule of this process, since this toxin accumulated in these symbionts/parasites. Furthermore, we identified the cDNA encoding the multifunctional prosurvival molecule BAG-1 in S. domuncula; it undergoes strong expression in the presence of the annelid. Our data suggest that sponges use toxins (here, OA) produced from bacteria to eliminate metazoan symbionts/parasites by apoptosis.     

Annelids, arthropods or molluscs are suitable as surrogate taxa for selecting conservation reserves in estuaries

The urgent need to conserve aquatic biodiversity and the lack of spatial data on biodiversity has motivated conservation planners and researchers to search for more readily obtainable information that could be used as proxies or surrogates. The surrogate taxon approach shows promise in some aquatic environments (e.g. intertidal) but not others (e.g. coral reefs, temperate rocky reefs). Estuaries are transitional environments at the land–sea junction with a unique biodiversity, but are the most threatened of aquatic environments because of high levels of human use. The comparatively small numbers of conservation reserves means that estuarine biodiversity is poorly protected. Selecting additional conservation reserves within estuaries would be facilitated by the identification of a suitable surrogate that could be used in conservation planning. In one estuary in Southeast Australia, we evaluated separately the effectiveness of annelids, arthropods, and molluscs as surrogates for predicting the species richness, abundance, assemblage variation, and summed irreplaceability of other species and for coincidentally representing other species in networks of conservation reserves selected for each surrogate. Spatial patterns in the species richness and assemblage variation (but not summed irreplaceability) of each surrogate were significantly correlated with the spatial patterns of other species. The total abundance of annelids and the total abundance of arthropods were each significantly correlated with the total abundances of other species. Networks of conservation reserves selected to represent each surrogate performed significantly better than random selection in representing other species. The greatest number of non-surrogate species was coincidentally included in reserves selected for the group of mollusc species. We conclude that annelids and arthropods are effective surrogate taxa for identifying spatial variation in several measures of conservation value (species richness, abundance, assemblage variation) in estuaries. We also conclude that spatial data on annelids, arthropods or molluscs can be used to select networks of conservation reserves in estuaries. The demonstrated effectiveness of these surrogates should facilitate future conservation planning within estuaries.     

Transplantation Immunity in Annelids. III. Effects of Temperature on Xenograft Rejection in Earthworms

Earthworms are capable of destroying body wall xenografts. Xenograftstransplanted Eisenia foetidaLumbricus terrestris at varioustemperatures showed that graft survival time is inversely proportionalto temperature in both cases. Colder temperatures slow graftrejection, but higher temperatures, up to optimal limits, accelerategraft destruction. At 21 C, Eisenia grafts on Lumbricus hostsare rejected faster than at any other experimental temperature;the variability in individual times is lessened. Beginning at23 C sub-optimal conditions are approached. Thus, graft survivaltimes are more prolonged. Lumbricus grafts on Eisenia hostsare rejected most quickly at 23 C; at 27 C all Eisenia are dead.A review of the earthworm's general thermal dependence is presentedand a rationalization for prolonged second-set graft survival(negative memory) at low temperatures is given. Temperatureeffects probably account for the lack of positive memory at15 C from previous studies.     

Population Dynamics of the Polychaetous Annelids of an Intertidal Habitat in Upper Old Tampa Bay,Florida

Following an extensive red-tide induced mass mortality of the benthic macrofauna of a sandy intertidal habitat, the population dynamics of the polychaete species were studied. Detailed studies of the 12 most abundant species are presented. Data concerning total population levels, reproduction, recruitment, distribution within the intertidal zone, and gut content analyses are integrated in order to explain the observed spatial and temporal patterns of distribution and abundance. Potential competive interactions for food are considered to be the most important factor for explaining the observed ecological patterns. The polychaete species studied are divided into three trophic guilds: an omnivorous guild that feeds predaciously and as non-selective deposit feeders, a surface feeding guild consisting of species usually considered to be selective surface deposit feeders, and a subsurface feeding guild usually considered as non-selective infaunal deposit feeders. Within and between guild interactions are discussed.