18S rDNA phylogeny of the Tubificidae (Clitellata) and its constituent taxa: dismissal of the Naididae

The phylogeny of the Tubificidae, and of most of its subfamilies and some of its genera, is revisited, on the basis of sequences of 18S ribosomal DNA in a selection of species. Forty-six new 18S sequences of Naididae (6), Tubificidae (37), Phreodrilidae (1), Lumbriculidae (1), and Enchytraeidae (1) are reported and aligned together with corresponding sequences of 21 previously studied taxa. The 18S gene of Insulodrilus bifidus provides the first molecular evidence that phreodrilids are closely related to tubificids, corroborating previous conclusions based on morphology. The data further support the monophyletic status of Tubificidae, provided that the "Naididae" is regarded a part of this family; "naidids" may not even constitute a monophyletic group. It is thus suggested that the family name Naididae is formally suppressed as a junior synonym of the Tubificidae. The 18S gene also resolves a number of relationships within the tubificids. Among the subfamilies, Tubificinae is supported, Rhyacodrilinae and Phallodrilinae are revealed as nonmonophyletic, and Limnodriloidinae remains unresolved. Most tubificid genera tested for monophyly are corroborated by the data, only one (Tubifex) is refuted, and two (Tubificoides and Limnodriloides) are unresolved from other taxa. It is concluded that it will be valuable to expand the taxonomic sampling for 18S rDNA in clitellates, and in annelids in general, as this is likely to improve the resolution at many levels. However, it will be equally important to combine the annelid 18S data with other gene sequences and nonmolecular characters, to estimate the phylogeny of these common and diverse worms with greater precision.     

A new species of Ainudrilus (Tubificidae) from South Georgia,and other subantarctic freshwater oligochaetes

The freshwater oligochaetes of the subantarctic islands are reviewed and new records are given. Ainudrilus dartnalli sp.n. (subfamily Rhyacodrilinae) is described from freshwater sites on South Georgia (South Atlantic Ocean). It differs from the closely related, southwest Australian, A. nharna Pinder & Brinkhurst, by its longer clitellum, the longer upper teeth of its ventral somatic chaetae, its straighter and fewer penial chaetae, and by the proportions of its spermathecae. Range extensions are given for two widespread naidids, Nais variabilis Piguet and N. communis Piguet, from the Falkland Islands (S. Atlantic). Moreover, new material of N. elinguis Müller is recorded from Macquarie Island (Southern Ocean, SW of New Zealand).     

Development of the genital ducts in Telmatodrilinae (Tubificidae, Clitellata)

In Tubificidae, the male genital duct comprises a funnel in the testes segment, followed by a vas deferens, an atrium, and, frequently, a copulatory structure in the adjacent ovarian segment. There may also be a diffuse or compact prostate gland in association with the duct. The morphology and position of the genital ducts are important for the classification of the oligochaetous Clitellata. Different parts of the male duct, however, have been named without regard to whether they are homologous or not. One way to establish better hypotheses of homology is to study the detailed morphology and/or the development of the genital ducts. The morphogenesis of the genital ducts in Alexandrovia onegensis (Telmatodrilinae) is described. The male funnel originates by multiplication of peritoneal (mesodermal) cells in the posterior septum in the testes segment. A cord of these cells breaks through the septum and grows backwards into the next segment, where it connects to the epidermis. This cord gives rise to the vas deferens, and is therefore mesodermal in origin. The atrium in A. onegensis develops from a primary epidermal (ectodermal) invagination. The vas deferens and atrium connect and a continuous duct from the testes segment to the exterior is formed. Several compact prostate glands develop along the atrium, each being formed from cells in the atrial epithelium. The spermatheca develops from an invagination of the epidermis in the testes segment. The female duct is formed from peritoneal (mesodermal) cells in the posterior septum in the ovarian segment. These developmental findings strengthen the hypothesis about a closer relationship between the Telmatodrilinae and Tubificinae (both Tubificidae).     

Phylogenetic status of the family Naididae (Oligochaeta, Annelida) as inferred from DNA analyses

Phylogenetic analyses based upon the D3 domain of the nuclear 23S rRNA gene and part of the mitochondrial COI gene indicate that the family Naididae is a subordinate group within the family Tubificidae and most closely related to the subfamily Rhyacodrilinae. Based upon relative genetic distances we hypothesize that the origin of Naididae occurred relatively early in the evolution of Tubificidae, but this was a fairly late event compared to the basic radiation among Annelida.     

A new species of Macquaridrilus (Annelida: Clitellata: Naididae) from subantarctic Campbell Island

Macquaridrilus mcmurtrieae n. sp. is described from Campbell Island. This resembles the only other species in the genus, Macquaridrilus bennettae Jamieson, 1968, in most aspects, but shows significant differences in the anatomy of its genitalia. In particular, the spermathecal pores are dorsal rather than lateral, the spermathecae lack diverticulae, the ejaculatory duct is more stout and muscular, the vas deferens is shorter relative to other organs and the anterior prostate is compact rather than elongate. The presence of a cuticular sperm canal appears to be an apomorphy for the genus. The new species was collected from streams and tarns across the island.

http://zoobank.org/urn:lsid:zoobank.org:pub:652AF61D-CFB2-4D07-94C8-59E6FB549D5F

http://zoobank.org/urn:lsid:zoobank.org:act:984F2456-768D-48A1-87AD-4453768BAB8A     

Genetic and chaetal variation in Nais worms (Annelida,Clitellata, Naididae)

The genus Nais is a group of oligochaetous clitellates, common in eutrophic freshwater habitats. About 30 species are described. Species identification is based primarily on chaetal characters, which are often subtle, inconsistent, and even overlapping between nominal species. We investigated the correlation between genetic variation and chaetal morphology in this genus. Eighty‐one individuals from Europe, North America, and China were included in the study. Seventy‐five of these were preserved as vouchers. They were scrutinized with regard to chaetal morphology, and ten different morphotypes were identified. Three molecular markers, two mitochondrial (the COI gene and 16S rDNA) and one nuclear (the ITS region), were used to establish the genetic lineages in the material. Genetic variation was found to be largely congruent with chaetal character patterns. However, at least nine separately evolving lineages (all supported by mitochondrial as well as nuclear data) correspond to at most six nominal species. Four morphotypes/lineages are recognized as Nais barbata, Nais christinae, Nais elinguis, and Nais stolci, respectively, whereas five, or possibly more, lineages represent a morphological continuum covering the variation of the Nais communis/variabilis complex. Thus, cryptic speciation is revealed. Our results indicate that a taxonomic revision of the genus will be needed in the future.     

Diversity and zoogeography of marine Tubificidae (Annelida,Oligochaeta) with notes on variation in widespread species

The specific and generic diversities of the marine Tubificidae (Annelida, Oligochaeta) of the NE Pacific are compared to those of the NE and NW Atlantic as well as to those of Heron Island, Australia. Diversity in the NE Pacific is relatively high when compared to that of the NE Atlantic. The Tubificidae of the NW Atlantic (limited to the eastern coast of the USA) show two distinct zoogeographic regions: Florida to Cape Hatteras; Cape Hatteras to Massachusetts. Diversity, both in terms of the number of species and number of genera, is approximately the same in these two regions, and is similar to that of both the NE Pacific and Heron Island. Evidence suggests that the widespread marine species, in particular Tubificoides pseudogaster, have a range of morphotypes across their distributions. The apparent wide distributions of these species may be due to a taxonomy unable to resolve the differences between the morphotypes. The tubificid oligochaete fauna of the NE Atlantic appears impoverished compared to the other regions examined. The NE Pacific, NW Atlantic, and Heron Island regions are not dominated by one group of species while the NE Atlantic fauna is dominated by Tubificoides benedeni and Clitellio arenarius.     

Comparative study of the cuticle in some aquatic oligochaetes (Annelida: Clitellata)

An examination of the cuticle of six aquatic oligochaete species using transmission electron microscopy revealed a larger morphological variation than previously known. Three freshwater species, Aulodrilus pluriseta, Spirosperma ferox (both Tubificidae), and Pristina breviseta (Naididae), and three marine species, Clitellio arenarius, Heterochaeta costata (both Tubificidae), and Paranais litoralis (Naididae), were investigated. The arrangement of the collagen fibers in the cuticle differs among the studied species. Only S. ferox shows an "orthogonal grid," i.e., layers of parallel fibers perpendicular to each other, as earlier described for lumbricids and enchytraeids. Clitellio arenarius and H. costata have fibers arranged in layers, while A. pluriseta and P. litoralis have irregularly distributed fibers. Pristina breviseta lacks cuticular fibers. The matrix surrounding the collagen fibers (when present) continues outside the fiber layer, making up a thin epicuticle, which has a unique banding in each of the studied species. The external surface of the epicuticle is covered with epicuticular projections. Their number, shape, and attachment to the epicuticle vary among the studied species. Furthermore, a distinctive internal substructure of the projections was observed in H. costata, A. pluriseta, S. ferox, and P. breviseta. Microvilli, extensions from the epidermal cells, penetrate the cuticle and terminate at its outer surface. In three species microvilli were observed to pinch off the epicuticular projections. The size, number, and shape of the latter vary; no typical microvilli were observed in S. ferox.     

Aquatic Oligochaeta in Italy, with special reference to Naididae

We present a list of Italian freshwater and marine Oligochaeta in the families Lumbriculidae, Haplotaxidae, Tubificidae, Naididae, Propappidae, Criodrilidae, and Lumbricidae, representing 57 genera and 130 species. Published data reflect the incomplete knowledge of the Italian oligochaete fauna, restricted to certain geographical areas. Subterranean aquatic and marine fauna are of particular interest as these have been studied the least. We provide a comprehensive review of the Naididae including, for the first time, southern Italy and the islands of Sicily and Sardinia. The distribution of species is discussed and taxonomic problems arising from the morphological variability of Italian material are examined.     

Distribution and habitat characteristics of Naididae and Tubificidae in the inland waters of Israel and the Sinai Peninsula

Nineteen species of Naididae and fourteen species of Tubificidae were found in collections from inland waters in Israel and Sinai. The local distribution patterns of the majority of these species were determined. The ranges of several physical and chemical variables characterizing the habitats of each species were defined. A correlation was found between the distribution patterns of some species and the following variables: salinity, temperature, dissolved oxygen, current velocities and stability of the habitats.     

Contributions towards the taxonomy of the African Naididae (Oligochaeta). IV. Zoogeographical and taxonomical considerations on African Naididae

A systematic revision of African Naididae confirmed the presence of 16 genera and 48 species. Allonais ranauana Boldt, 1932 is confirmed as a distinct species, Nais raviensis Stephenson, 1914 has very short gills and is a species of Dero, and Rhopalonais has equally obscure gills and is attributable to Dero. Pristina proboscidea Beddard, 1896 is synonymous with P. longiseta Ehrenberg, 1828.African naidids are primarily tropical, the most widespread genus is Pristina, followed by Aulophorus, Nais and Dero. Nais is dominant in South Africa, whereas the other genera predominate in the tropics along with Rhopalonais. The most widespread species are A. furcatus, N. variabilis, P. longiseta and P. menoni.Serrations on hair setae and intermediate teeth in bifid needles are universally present as seen under SEM, their reported absence under light microscopes is attributable to lack of resolution power. SEM is also useful in determining gills in Dero. Size of setae within and between individuals is more constant than the literature would suggest as the standard deviation is usually less than 10% of the mean. There is a constant relationship between setal length and size of worm, and between median ventral setae and needles in this material.Setal size is a diagnostic character in taxonomy. The standard deviation of the mean number of segments in front of the budding zone averages 9.9%, the highest value (25.7%) was for Stylaria fossularis. Differences of more than 10% may usually be considered diagnostic. The total number of segments is exceedingly variable and cannot be used as a taxonomical characteristic. The same applies to segment length or diameter.     

Growth of Stylaria lacustris (L.) (Oligochaeta,Naididae)

The peculiarities of the growth in weight and length of Stylaria lacustris (L.) on the basis of observations in experimental vessels are considered. The growth of this species fits a parabolic curve. The equations relating weight to absolute growth rate as well as weight to duration of life are given.     

Earthworms (Clitellata, Acanthodrilidae) of the mountains of Eastern Jamaica

Fourteen species new to science are described from material collected at several sites in the Blue Mountains and the John Crow Mountains of eastern Jamaica, doubling the known endemic Jamaican earthworm fauna. New data on Dichogaster montecyanensis (Sims) are provided. All species are placed in the genus Dichogaster Beddard, which is here treated sensu lato, i.e. including Eutrigaster Cognetti. Eight of the new species have lost the posterior pair of prostates and the seminal grooves of the male field. These are D. bromeliocola, D. crossleyi, D. davidi, D. garciai, D. harperi, D. haruvi, D. hendrixi, and D. johnsoni. D. sydneyi n. sp. has independently lost the posterior prostates but not the seminal grooves. The new species D. altissima and D. manleyi have the conventional dichogastrine prostatic battery and male field characteristics. Three species described here, D. farri, D. garrawayi, and D. marleyi, all have a third pair of prostates in the 20th segment, no seminal grooves, dorsal paired intestinal caeca in segment lxv, and lack penial setae.     

Life-cycle and karyology of Branchiura sowerbyi Beddard (Oligochaeta,Tubificidae)

Data on the life-cycle of a population of Branchiura sowerbyi Beddard in a water-lily tank at the Botanical Garden in Padua are reported. The breeding period is from April to July, after which the reproductive system is partially resorbed (August–September) and reformed later in the autumn. The karyology of the species was also studied, and revealed 38 mitotic chromosomes in the gonia, and 19 bivalents in the primary spermatocytes and in the primary oocytes.     

Preliminary study of the aquatic Oligochaeta of the Changjiang (Yangtze) River

The aquatic oligochaetes in mainstream of the Changjiang River have not been studied previously. Since 1983, benthic samples have been collected mainly from mid-upper reach of the river. Altogether 19 species belonging to 4 families of the Oligochaeta were found. Among them, Nais inflata is the commonest species throughout the river, whereas Nais sp., Arcteonais lomondi, Limnodrilus silvani, Rhyacodrilus riabuschinskii and Telmatodrilus sp. ae recorded from China for the first time.Quantitatively, the aquatic oligochaetes constitute the majority of zoobenthos in the mainstream. In 1984, the standing crop of the Tubificidae was 231–343 ind·m^-2 in density and 0.73–0.97 g·m^-2 (wet weight) in biomass, and that of the Naididae was 21–4982 ind·m^-2 and 0.003–1.75 g·m^-2 (wet weight) respectively.     

Ultrastructural features of gametogenesis during the life cycle in Branchiura sowerbyi Beddard (Oligochaeta,Tubificidae)

An ultrastructural analysis of the gametogenetic phases in Branchiura sowerbyi, a tubificid oligochaete, has been accomplished. These phases mostly conform to the usual pattern for the family, however, some interesting peculiarities are pointed out. The regression of sexual apparatus after reproductive period and its regeneration up to a new period of sexual maturity, has been followed throughout the year.     

Ecological survey of the aquatic oligochaetes in the Lower Pearl River (People's Republic of China)

The species composition, distribution and abundance of the Tubificidae (8 spp.) and Naididae (at least 4 spp.) in the Guangzhou reach of the Lower Pearl River were investigated. Limnodrilus spp. (particularly L. hoffmeisteri) constitutes the greatest part in nearly all samples, which were taken in both clean and polluted parts of the reach. In the polluted sites, total oligochaete densities reach values of up to 700 000 ind. m^–2. The importance and problems of using oligochaetes as indicators of organic pollution are discussed.     

A taxonomic and faunistic survey of the marine Tubificidae and Enchytraeidae (Oligochaeta) of Italy. Introduction and preliminary results

On the basis of material collected along the Ligurian, Tyrrhenian, Ionic and Adriatic coasts of Italy, a tentative list of 26 species (18 tubificids, 8 enchytraeids) of marine Oligochaeta is presented. Most of the species are new to science, and it can therefore be concluded that there is a very high diversity of oligochaetes in the Mediterranean Sea.