Hannelore Paxton

Redescription of Ophryotrocha puerilis and O. labronica (Annelida, Dorvilleidae)

Abstract For more than a century, it has been pointed out that most features of the original description of Ophryotrocha puerilis Claparède & Mecznikow, 1869, probably based on a mixed population of two sympatric species, agree better with the subsequently described O. labronica La Greca & Bacci, 1962. Although O. labronica was described as a protandrous hermaphrodite that could self-fertilize, the widely distributed species is mainly gonochoristic. We will designate neotypes, redescribe these two polychaetes and review their reproduction and development to remove any confusion and uncertainty surrounding the identity of these two well-known polychaetes. We will also discuss the growth and replacement of the maxillary apparatus and the morphology and distribution of the rosette glands, providing support for the molecular phylogeny of selected Ophryotrocha species.

The Diopatra chiliensis confusion—redescription of D. chiliensis (Polychaeta, Onuphidae) and implicated species

Diopatra chiliensis Quatrefages, 1865 is redescribed based on the presumed holotype and numerous specimens from Coronel, Chile north to Callao, Peru. The species displays a high degree of variability with respect to prostomial appendages, parapodial structures and setae. Diopatra rhizoicola Hartmann‐Schroder, 1960 and D. heterodentata Hartmann‐Schröder, 1965 from Peru and Chile are considered junior synonyms of D. chiliensis. All available specimens of previous records of D. chiliensis have been re‐examined, most of which are referred to the following species: D. gesae, sp. n., D. kristiani, sp. n., D. obliqua Hartman, 1944 D. rhizophorae Grube, 1856, and D. sugokai Izuka, 1907. Diopatra bilobata Imajima, 1967 was found to be a junior synonym of D. sugokai, widely distributed Indo‐Pacific species. The six species are described and illustrated, and their characteristics are compared in tabular form. A revised onuphid terminology of prostomial and parapodial features is also provided.

Diopatra marocensis, a new brooding species of Onuphidae (Annelida:Polychaeta)

A new species, Diopatra marocensis , is described from the fine sand Abra alba community, Sidi Boulbra, south Moroccan Atlantic coast. The new species is a member of the D. cuprea complex and is characterized by having crescentic nuchal grooves, short ceratophores, a short branchiate region, four pairs of modified parapodia with bidentate pseudocompound hooks, pectinate setae with 11–20 teeth, limbate setae with conspicuously serrated shelf, and subacicular hooks from setiger 13–15. Eggs of Diopatra marocensis sp. nov. are deposited in the parental tube, where they undergo direct development and remain until the young consist of 32–34 setigers.

Ordovician and Silurian polychaete diversity and biogeography

Abstract Eunicidan polychaetes formed a significant part of Early Palaeozoic marine invertebrate communities, as shown by the abundance and diversity of scolecodonts (polychaete jaws) in the fossil record. In this study we summarize the early radiation and biodiversity trends and discuss the palaeobiogeography of these fossils. The oldest (latest Cambrian–Early Ordovician) representatives had primitive, usually symmetrical, placognath/ctenognath type jaw apparatuses. The first more advanced taxa, possessing labidognath-type jaw apparatuses or placognath apparatuses with compound maxillae, are first recorded in the Middle Ordovician. The most significant increase in generic diversity occurred in the Darriwilian, when many common taxa appeared and diversified. The Ordovician and Silurian scolecodont occurrences allow some palaeobiogeographical units and distribution patterns to be explored and outlined. The most robust data presently at hand derive from successions in Baltica and Laurentia. That information, together with new records from other palaeocontinents, reveals a wide distribution for the most frequent and species-rich genera and families, similar to the biogeographical patterns of extant polychaetes. Like many other benthic and pelagic fossil groups, scolecodont-bearing polychaetes show an increased cosmopolitan character in the Silurian as compared with the Ordovician. Species-level endemism appears to be relatively common, inferring a potential for scolecodonts as biogeographical tools in the future.

Molting polychaete jaws--ecdysozoans are not the only molting animals.

Summary Jaw shedding and replacement of Diopatra aciculata (Onuphidae, Eunicida), by the same process as arthropod molting, involving apolysis and ecdysis, is described here. These observations suggest that molting has either evolved convergently in eunicidan polychaetes and ecdysozoans or it was present in the last ecdysozoan/lophotrochozoan common ancestor and thus may not represent a synapomorphy of the ecdysozoans.

Jaw growth and replacement in Polychaeta

Summary Mandibles and maxillae of Australonuphis teres (family Onuphidae) continue to grow throughout life without replacement. Mandibles are solid structures that grow by external depositions, leaving a series of growth rings. Maxillae are hollow without any growth rings. New teeth are added to a maxilla by the division of its most distal tooth. Overall growth of the maxillae is thought to occur from the inner epidermal layer of the cavity. The same mode of growth is expected in all extant Eunicoidea with exception of Dorvilleidae, where maxillae are periodically replaced.

Biogeography and incipient speciation in Ophryotrocha labronica (Polychaeta, Dorvilleidae)

Crossing experiments were conducted between the Naples I (NI) strain of Ophryotrocha labronica labronica, three strains of O. l. pacifica from Japan (M3), Hawaii (WH) and Los Angeles (LA), two strains of O. labronica from Australia and one from an unknown origin, discovered in a Moscow aquarium, to determine the relationships between the European and Pacific subspecies, and the newly discovered strains. Previously published data combined with new results revealed several stages in the process of speciation within the sibling group. Interpopulation crosses yielded an increased sex ratio that appears to be positively related to genetic distance and to the sex ratio of the parent strains. Fecundity data demonstrated that the three northern Pacific strains are more closely related to each other than to any other strain, confirming that they are a valid subspecies, and indicate that they are the result of natural distribution. The strain of unknown origin as well as the Australian strains clearly belong to O. l. labronica. Its isolated presence in the South Pacific may be a remnant of an earlier wider distribution or an introduction of the Mediterranean population, as the life histories of Ophryotrocha species have made them prime candidates for anthropogenic dispersals.

Ghosts from the past - ancestral features reflected in the jaw ontogeny of the polychaetous annelids Marphysa fauchaldi (Eunicidae) and Diopatra aciculata (Onuphidae)

Species of Eunicida (polychaetous annelids) have complex jaw apparatuses with ventral mandibles growing throughout life, but dorsal maxillae undergoing successive moulting episodes. Jaw ontogeny was studied in the eunicid Marphysa fauchaldi, from the appearance of the mandibles and larval maxillae through two moults during the transformation to juvenile and sub-adult maxillae. Although larval maxillae have been previously known, this is the first description of the juvenile stage for Eunicidae. The immature maxillary stages of M. fauchaldi were compared with those of Diopatra aciculata of the sister family Onuphidae, and, in a novel approach, extended deep into the fossil record by searching among adult stages of extinct eunicidans. Although neither the larval nor the juvenile stage resembles any complete fossil apparatus, each stage has features of separate maxillae known from different geological times. The larval maxilla II of both species is similar to the jaws of the Early Ordovician xanioprinids, the juvenile maxilla I of D. aciculata strikingly resembles those of the adult Palaeozoic Atraktoprion, whereas that of M. fauchaldi resembles those of Brochosogenys and allies. Thus, the extant taxa analysed represent cases in which ontogeny recapitulates phylogeny. It may also suggest that onuphid jaws are closer to the ancestral state than those of eunicids. This study opens a new perspective on evolutionary patterns, discusses asymmetry in jaw apparatuses relating to the basal plate concept, the apparent absence of early ontogenetic stages from the fossil record and cautions the use of architectural types in the interpretation of fossil maxillary apparatuses.

A New Species of Palpiphitime (Annelida: Dorvilleidae) from Western Canada

Abstract Palpiphitime lipovskyae, new species, is described on the basis of specimens collected near an Atlantic salmon farm in Hecate Strait, British Columbia, Canada. The new species differs from P. lobifera (Oug, 1978), the only other described species in the genus, by having lamella-like dorsal and digitate ventral lateral lobes, its parapodia lacking ventral chaetal lobes, mandibles with fewer teeth, and P-forceps having serrated ridges with alternating large and small teeth. The definition of Palpiphitime Orensanz, 1990 is expanded to include the characteristic jaws.

Evidence of simultaneous hermaphroditism in the brooding Diopatra marocensis (Annelida: Onuphidae) from northern Spain

A one-year study of the reproductive biology of a population of Diopatra marocensis at the Villaviciosa estuary, northern Spain, was undertaken with emphasis on brooding behaviour, larval development and gametogenesis. Field observations together with a histological study of monthly collected individuals revealed that the population was iteroparous, reproducing annually during a short breeding season extending fromMarch to June. The study demonstrated that all individuals of the population at Villaviciosa estuary were producing at the same time eggs and sperm providing for the first time evidence for the occurrence of simultaneous hermaphroditism in D. marocensis. Mature sperm was of the ent-aquasperm type and was stored in modified nephridial chambers in brooding individuals. In the latter, eggs in advanced cleavage phases were also observed inside the coelom suggesting that fertilization was internal. Eggs in late vitellogenesis presented micronucleoli in the periphery of the nucleus, a phenomenon reported previously for few polychaete species. Pure males and females were never found. It is here suggested that inD. marocensis population size may influence sex allocation and that under conditions of low population densities simultaneous hermaphrodites may be favoured. The study of the larval development confirmed the direct development reported previously for populations of Morocco and Portugal. Further results suggest consumption of nurse eggs and adelphophagy by developing larvae.