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.     

Quantitative observations on the population ecology of Branchiura sowerbyi (Oligochaeta,Tubificidae)

Cohorts of Branchiura sowerbyi were reared at different temperatures and initial population densities in order to obtain data suitable for the interpretation of population dynamics in field populations. Percent hatching from cocoons reaches its maximum at 25 °C and decreases towards lower and higher temperatures. Embryonic development time, T_E, was measured and the relative threshold temperature, 10 °C, calculated by extrapolation. The degree day requirement for embryo development is 195 °C d. The time of first cocoon laying (T_gm) was observed and the ratio T_E/T_gm was seen to fit with that of other tubificid species cultured so far. Embryo mortality is rather high, while worm mortality is low or very low. Fecundity increases from 15 to 20 °C but decreases at 25 °C. A mathematical model for the simulation of population densities with four size-stage compartments is suggested. It could be used for the optimization of worm uptake (simulated as stage specific mortality) in mass cultures reared for the production of Branchiura, to be used as food for fish fingerlings.     

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.     

The effect of temperature on the life cycle, growth and fecundity of Branchiura sowerbyi (Oligochaeta: Tubificidae)

Branchiura sowerbyi Beddard was probably introduced to Britain with exotic plants consigned to botanic gardens. The British populations occur mainly in artificially warmed habitats such as lily ponds in botanic gardens and power station effluents but a few are found at natural temperatures.
Branchiura completed its life cycle in about a year both in the river Avon, Wiltshire, at natural temperatures and in the warm effluent from a power station discharging into the river Thames. In a worm culture maintained at natural temperatures the rate of cocoon production reached a peak in summer and was closely related to temperature.
In the laboratory it was found that the optimum temperature for cocoon laying in mature worms, also growth in sexually immature worms, was near 25°C. The optimum temperature for growth in sexually mature worms, however, was lower (10°C in the Avon population and 15°C in the Thames population). It followed that at 20°–25°C the growth of sexually mature worms was probably depressed by the high rate of cocoon production.     

Long-term experiment on Branchiura sowerbyi Beddard (Oligochaeta,Tubificidae) using sediment treated with LAS (Linear Alkylbenzene Sulphonate)

A long-term experiment was performed with Branchiura sowerbyi in order to assess possible effects of LAS sorbed to sediment on its reproductive cycle, using concentrations in sediment 2–5 times higher than those calculated for the LC50 values of LAS dissolved in water. No significant effects were observed during the whole experiment, so that we can confirm that LAS adsorbed on sediment has a much lower influence on the examined animals than LAS dissolved in water.     

Olavius cornuatus sp.n. (Oligochaeta, Tubificidae) from Georges Bank (NW Atlantic)

Olavius cornuatus sp.n. is described from Georges Bank off Massachusetts. It is distinguished from other species of Olavius Erséus, 1984 by its curved, horn-shaped atria ending in large, protrusible penes and up to six ectally hooked penial setae per bundle.     

微孢子虫系统进化研究的变迁与展望

微孢子虫(Microsporidia)是一类专性细胞内寄生的单细胞真核生物,在科研、医疗、农业、商业等领域具有重要影响。由于其不具有某些典型的真核生物细胞结构,如线粒体、过氧化物酶体、高尔基体、鞭毛,曾将其归属于古真核生物谱系,认为其进化历程先于这些细胞器的起源,该假说也得到了一些生物化学和分子生物学研究证据的支持。然而,在最近十年里,通过更深入的研究,尤其是基于分子序列的系统进化分析,表明微孢子虫和真菌具有一定亲缘关系,并认为其结构的简约性恰好体现了微孢子虫营寄生生活的高度退化现象。目前对微孢子虫的系统进化仍存在各种不同意见,对其进化研究历史进行探讨有着重要意义。本文将按照时间顺序回顾微孢子虫进化分类研究过程中的各种研究成果,并讨论为什么微孢子虫独特的细胞和基因组特性会导致众多的学者在其进化分类问题上争执这么久。     

Potamothrix scleropenis sp. nov. (Oligochaeta: Tubificidae) from Fuxian Lake, the deepest lake in southwest China

Potamothrix scleropenis sp. nov. (Tubificidae: Tubificinae) is described from the profundal zone (74 m) of Fuxian Lake, the deepest lake (up to 155 m) on the Yunnan-Guizhou Plateau in China. The new species is assigned to Potamothrix because of its short vasa deferentia and its tubular atria without ejaculatory ducts and prostate glands. It differs from congeners by its cuticularized penis sheaths; bifurcated, strongly curved spermathecal chaetae; bifurcated lower prongs of bifids; and feathered hairs. P. scleropenis appears closely related to P. cekanovskajae Finogenova, 1972 and P. tudoranceai Sporka, 1994, since all the three species have homogeneous atria without prostate glands.     

A new isolate of Nosema sp. (Microsporidia, Nosematidae) from Phyllobrotica armata Baly (Coleoptera, Chrysomelidae) from China

We studied the spore morphology and molecular systematics of a novel microsporidian isolate from Phyllobrotica armata Baly collected in China. The spores were long-oval and measured 4.7 × 2.6 μm on fresh smears. Ultrastructure of the spores was characteristic for the genus Nosema: 13-14 polar filament coils, posterior vacuole, and a diplokaryon. The complete rRNA gene sequence of the isolate was 4308 bp long. The organization of the rRNA gene was 5′-LSU rRNA-ITS-SSU rRNA-IGS-5S-3′, which corresponds to that of the Nosema species. Phylogenetic analysis based on the rRNA gene sequence indicated that this isolate, designated as Nosema sp. PA, is closely related to Nosemabombycis and is correctly assigned to the “true” Nosema group.     

Rhododrilus sexpapillatus n.sp. (Oligochaeta: Megascolecidae) from New Zealand

Abstract

A new earthworm species belonging to the acanthodriline genus Rhododrilus is described from the North Island of New Zealand, elevating the generic total (excluding Australian forms) to 30 species. The new taxon forms part of the species-group with incomplete fusion of the male and prostatic terminalia. Its most closely related congener is the geographically proximate R. papaensis. Though exhibiting great heterogeneity, suggestive of polyphyly, the genus remains taxonomically convenient. It probably encompasses convergent forms, the ancestral affinities of which may never be ascertained.     

Transfer of Nosema locustae (Microsporidia) to Antonospora locustae n. comb. based on molecular and ultrastructural data

Nosema locustae is a microsporidian parasite of grasshopper pests that is used as a biological control agent, and is one of the emerging model systems for microsporidia. Due largely to its diplokaryotic nuclei, N. locustae has been classified in the genus Nosema, a large genus with members that infect a wide variety of insects. However, some molecular studies have cast doubt on the validity of certain Nosema species, and on the taxonomic position of N. locustae. To clarify the affinities of this important insect parasite we sequenced part of the rRNA operon of N. locustae and conducted a phylogenetic analysis using the complete small subunit rRNA gene. Nosema locustae is only distantly related to the nominotypic N. bombycis, and is instead closely related to Antonospora scoticae, a recently described parasite of bees. We examined the ultrastructure of mature N. locustae spores, and found the spore wall to differ from true Nosema species in having a multi-layered exospore resembling that of Antonospora (one of the distinguishing features of that genus). Based on both molecular and morphological evidence, therefore, we propose transferring N. locustae to the genus Antonospora, as Antonospora locustae n. comb.     

Ultrastructure and phylogeny of Glugea arabica n. sp. (Microsporidia), infecting the marine fish Epinephelus polyphekadion from the Red Sea

A new microsporidian species, Glugea arabica n. sp., is reported infecting the intestinal wall of the marine teleost Epinephelus polyphekadion (=microdon) collected from the Red Sea coast off Saudi Arabia, and described on the basis of microscopic and molecular procedures. Spherical blackish xenomas formed parasitophorous vacuoles completely packed with several parasitic developmental stages, including spores. The nuclei were monokaryotic in all developmental stages. Spores were ellipsoidal to pyriform and measured 6.3 ± 0.3 (5.9–6.6) μm in length and 3.3 ± 0.4 (2.9–3.7) μm in width. A lamellar polaroplast surrounded the uncoiled portion of the polar filament, which extended into the spore's posterior pole and formed 27–29 coils organized in three or four rows. The posterior vacuole, located at the spore's posterior pole, appeared surrounded by the polar filament coils and displayed an irregular matrix composed of light material, in which was located the posterosome. Molecular analysis of the rRNA genes, including the ITS region, was performed using maximum parsimony, neighbor-joining and maximum likelihood methodologies. The ultrastructural features observed, in combination with the molecular data analysed, suggests the parasite to be a new species of the genus Glugea.     

Ameson hybomitrae sp. n. (Microsporidia, Pereziidae) from gadflies of Karelia

Microsporidia of the genus Ameson were recorded from larvae of horseflies of the genus Hybomitra in Karelia. Earlier these Microsporidia were recorded from crustaceans. The infection extensiveness ranges from 5.1 to 10.5%. The parasites develop in musculature, fat body and salivary glands of the host. The new species has uninucleate, single-located egg- and pear-shaped spores. The ultrafine structure of developmental stages and spores is studied.     

Two aberrant Tubificidae (Oligochaeta) from Pearl River in the People's Republic of China

The enigmaticIlyodrilus mastix Brinkhurst, 1978, andTectidrilus achaetus sp.nov. are described from the Guangzhou Reach of Pearl River, southern China. The first species is characterized by its greatly enlarged, eversible, feeding apparatus, and was previously known only from British Columbia, Canada.Tectidrilus achaetus is unique within the Tubificidae by lacking setae. A slightly modified definition of the, otherwise marine, genusTectidrilus Erséus, 1982 is provided.     

Horizontal and vertical transmission of a Nosema sp. (Microsporidia) from Lymantria dispar (L.) (Lepidoptera: Lymantriidae)

The gypsy moth, Lymantria dispar L. (Lepidoptera, Lymantriidae), a serious defoliator of deciduous trees, is an economically important pest when population densities are high. Outbreaking populations are, however, subject to some moderating influences in the form of entomopathogens, including several species of microsporidia. In this study, we conducted laboratory experiments to investigate the transmission of an unusual Nosema sp. isolated from L. dispar in Schweinfurt, Germany; this isolate infects only the silk glands and, to a lesser extent, Malpighian tubules of the larval host. The latent period ended between 8 and 15 days after oral inoculation and spores were continuously released in the feces of infected larvae until pupation. Exclusion of feces from the rearing cages resulted in a 58% decrease in horizontal transmission. The silk of only 2 of 25 infected larvae contained microsporidian spores. When larvae were exposed to silk that was artificially contaminated with Nosema sp., 5% became infected. No evidence was found for venereal or transovum (including transovarial) transmission of this parasite.     

Cryptosporidium apodemi sp. n. and Cryptosporidium ditrichi sp. n. (Apicomplexa: Cryptosporidiidae) in Apodemus spp.

Faecal samples from striped field mice (n = 72) and yellow-necked mice (n = 246) were screened for Cryptosporidium by microscopy and PCR/sequencing. Phylogenetic analysis of small-subunit rRNA, Cryptosporidium oocyst wall protein and actin gene sequences revealed the presence of C. parvum, C. hominis, C. muris and two new species, C. apodemi and C. ditrichi. Oocysts of C. apodemi are smaller than C. ditrichi and both are experimentally infectious for yellow-necked mice but not for common voles. Additionally, infection by C. ditrichi was established in one of three BALB/c mice. The prepatent period was 7–9 and 5–6 days post infection for C. apodemi and C. ditrichi, respectively. The patent period was greater than 30 days for both species. Infection intensity of C. ditrichi ranged from 4000–50,000 oocyst per gram of faeces and developmental stages of C. ditrichi were detected in the jejunum and ileum. In contrast, neither oocysts nor endogenous developmental stages of C. apodemi were detected in faecal or tissue samples, although C. apodemi DNA was detected in contents from the small and large intestine. Morphological, genetic, and biological data support the establishment of C. apodemi and C. ditrichi as a separate species of the genus Cryptosporidium.     

Argulus izintwala n. sp. (Crustacea: Branchiura) from Lake St Lucia,South Africa

During surveys of the fish parasites of Lake St Lucia on the coast of northern KwaZulu-Natal, specimens of an hitherto undescribed argulid were found on the skin of the kelee shad Hilsa kelee (Cuvier). This, only the fourth argulid species to be found in South African coastal waters, is here described as Argulus izintwala n. sp.     

Myospora metanephrops (n. g., n. sp.) from marine lobsters and a proposal for erection of a new order and family (Crustaceacida; Myosporidae) in the Class Marinosporidia (Phylum Microsporidia)

In this study we describe, the first microsporidian parasite from nephropid lobsters. Metanephrops challengeri were captured from an important marine fishery situated off the south coast of New Zealand. Infected lobsters displayed an unusual external appearance and were lethargic. Histology was used to demonstrate replacement of skeletal and other muscles by merogonic and sporogonic stages of the parasite, while transmission electron microscopy revealed the presence of diplokaryotic meronts, sporonts, sporoblasts and spore stages, all in direct contact with the host sarcoplasm. Analysis of the ssrDNA gene sequence from the lobster microsporidian suggested a close affinity with Thelohania butleri, a morphologically dissimilar microsporidian from marine shrimps. Whilst morphological features of the lobster parasite are consistent with members of the family Nosematidae, molecular data place the parasite closer to members of the family Thelohanidae. Due to the contradiction between morphological and molecular taxonomic data, we propose the erection of a new genus in which the lobster parasite is the type species (Myospora metanephrops). Furthermore, we recommend the erection of a new family (Myosporidae) and a new order (Crustaceacida) to contain this genus. The taxonomic framework presented could be further applied to the re-classification of existing members of the Phylum Microsporidia.     

Eimeria melogale n. sp. (Apicomplexa: Eimeriidae) in the Javan ferret-badger (Melogale orientalis)

The Javan ferret-badger Melogale orientalis (Carnivora: Mustelidae: Helictidinae) is a small carnivore endemic to Indonesia. In the family Mustelidae, 10 Eimeria, 12 Cystoisopora, one Isospora, and one Hammondia species are known, but no eimeriid coccidia has been yet described in the subfamily Helictinidae (ferret badgers). Coproscopic examination of Javan ferret-badgers imported into the Czech Republic revealed the presence of coccidian oocysts. Sporulated oocysts differ from other Eimeria known in the family Mustelidae by their small size (12.4–16.1 × 10.4–13.4 μm) and ovoidal shape. Morphological data and phylogenetic analyses of 18S rRNA and COI genes indicated a new species of Eimeria found in faecal samples of Javan ferret badgers. The species is described as E. melogale n. sp.     

Two new species of freshwater Oligochaeta from the North-west Iberian Peninsula: Krenedrilus realis sp. nov. (Tubificidae) and Cernosvitoviella bulboducta sp. nov. (Enchytraeidae)

Two new species of aquatic Oligochaeta are described from the North-west Iberian Peninsula: Krenedrilus realis sp. nov. (Tubificidae) and Cernosvitoviella bulboducta sp. nov. (Enchytraeidae). Krenedrilus realis is the fourth species in a genus of small and presumably plesiomorphic Tubificinae. It is closely related to K. sergei Giani, Erséus & Martínez-Ansemil, 1990. Cernosvitoviella bulboducta belongs to a genus of small amphibiotic enchytraeids. It is close to C. ampullax Klungland & Abrahamsen, 1981 and C. tatrensis (Kowalewski, 1916). Supplementary data to the diagnosis of C. tatrensis are given. The presence of two small glands attached to the gut immediately behind the pharyngeal bulb is noticed in C. bulboducta and C. tatrensis . This previously unknown character is probably more common in the genus than has been supposed.