Phagocytosis of Loma salmonae (Microsporidia) spores in Atlantic salmon (Salmo salar), a resistant host, and chinook salmon (Oncorhynchus tshawytscha), a susceptible host.

The in vitro phagocytosis of Loma salmonae spores by macrophages of Atlantic salmon and two strains of chinook salmon were investigated. Opsonisation of L. salmonae with plasma factors increased uptake by head kidney macrophages. Macrophages of Atlantic salmon, which are resistant to the parasite, had a significantly higher phagocytic index (PI) than those of chinook salmon, a susceptible species. This may indicate a possible mechanism contributing to resistance in Atlantic salmon or that L. salmonae is able to evade or suppress initial binding by macrophages of chinook. Non-specific binding or lectinophagocytosis was also suggested by significantly higher PI of spores from EDTA treated plasma when compared with no plasma or heat treated plasma. In comparison, uptake of Baker's yeast Saccharomyces cerevisiae by phagocytes was not significantly different between fish species and strains for all treatments.

Innate susceptibility differences in chinook salmon Oncorhynchus tshawytscha to Loma salmonae (Microsporidia).

Loma salmonae (Putz, Hoffman and Dunbar, 1965) Morrison & Sprague, 1981 (Microsporidia) is an important gill pathogen of Pacific salmon Oncorhynchus spp. in the Pacific Northwest. Three strains of chinook salmon O. tshawytscha were infected in 2 trials with L. salmonae by feeding of macerated infected gill tissue or per os as a gill tissue slurry. Intensity of infection was significantly higher in the Northern stream (NS) strain as compared to the Southern coastal (SC) and a hybrid (H) strain derived from these 2 strains. Both wet mount and histological enumeration of intensity of infection demonstrated strain differences. Survival in the NS strain was significantly lower than the other strains. The NS strain may represent a naive strain and be less able to mount an effective immune response against the parasite.

Experimental and natural host specificity of Loma salmonae (Microsporidia).

The microsporidian Loma salmonae (Putz, Hoffman & Dunbar, 1965) Morrison & Sprague, 1981 has caused significant gill disease in Pacific salmon Oncorhynchus spp. Host specificity of the parasite was examined experimentally by per os challenge of selected salmonids and non-salmonids with infective chinook salmon O. tshawytscha gill material. Pink Oncorhynchus gorbuscha and chum salmon O. keta, brown Salmo trutta and brook trout Salvelinus fontinalis, and chinook salmon (controls) were positive, whereas Atlantic salmon Salmo salar and Arctic char Salvelinus alpinus were negative. In addition, no non-salmonids were susceptible to experimental exposure. Wild Pacific salmon species in British Columbia, Canada, were examined for L. salmonae during their freshwater life history stages (smolts, prespawning, spawning). All stages were infected, although infections in smolts were only detectable using a L. salmonae-specific PCR test. Many previous Loma spp. described from Oncorhychus spp. are likely L. salmonae based on host, parasite morphology, and site of infection.

Viability of Loma salmonae (Microsporidia) under laboratory conditions.

The viability of the fish-infecting microsporidian Loma salmonae Morrison and Sprague, 1981 was determined under laboratory conditions by polar filament extrusion and infectivity to chinook salmon (Oncorhynchus tshawytscha). Extrusion rates of isolated spores decreased from 51.0% to 0.0% by 100 days after storage in fresh or sea water at 4 degrees C. Spores stored up to 95 days in either solution infected 80.0-100.0% of exposed chinook, although no spores infected fish at 100 days in one trial. Viability in Earl's balanced salt solution was tested up to 50 days, with 23.7% of spores extruding filaments and 80.0% of exposed chinook becoming infected. Spores frozen to -20 degrees C or -70 degrees C were unable to infect fish.

Modes of transmission of Loma salmonae (Microsporidia).

Loma salmonae (Putz, Hoffman and Dunbar, 1965) Morrison and Sprague, 1981 (Microsporidia) causes prominent gill disease in pen-reared chinook salmon Oncorhynchus tshawytscha in the Pacific Northwest. Transmission of the parasite was examined by exposing Pacific salmon Oncorhynchus spp. to infectious spores by various routes: per os, intraperitoneal, intramuscular, and intravascular injection, by cohabitation with infected fish, and by placement of spores directly on the gill. All exposure methods led to infections except placement of spores on the gill. Putative sporoplasms were visible in epithelial cells of the alimentary canal within 24 h of per os exposure. L. salmonae may initially infect alimentary epithelial cells and then migrate into the lamina propia to access the blood stream. Positive results obtained by intravascular injection suggest that autoinfection from spores of ruptured xenomas in the endothelium may also occur. The cohabitation experiment demonstrates that fish may become infected by spores released from live fish.

Camallanus carangis Olsen, 1954 (Nematoda: Camallanidae) reported from French Polynesia and Hawai'i with a redescription of the species.

The marine fish parasite Camallanus carangis Olsen, 1954 (Nematoda: Camallanidae) is redescribed from the honeycomb grouper Epinephelus merra (Serranidae) in the Tuamotu Islands of French Polynesia and the glasseye Heteropriacanthus cruentatus (Priacanthidae) in Hawai'i, both coral reef fishes. Camallanus carangis is reported for the first time from French Polynesia and Hawai'i. Camallanus marinus Schmidt and Kuntz, 1969 is designated a synonym of C. carangis and Camallanus paracarangis Velasquez, 1980 is regarded as a species inquirenda. Additionally, the genus Oncophora may need to be redefined to accommodate Camallanus aotea Slankis and Korotaeva, 1974, which bears more resemblance to Oncophora than Camallanus.

Infection of Aulorhynchus flavidus (Gill) (Osteichthyes: Gasterosteiformes) by Kudoa thyrsites (Gilchrist) (Myxosporea: Multivalvulida).

The myxosporean parasite Kudoa thyrsites is reported from a new host, Aulorhynchus flavidus, the tube-snout, collected near Vancouver, British Columbia, Canada. Prevalence reached 100% and intensity 1,535 pseudocysts per 2 cm length of fish. Polymerase chain reaction primers specific for K. thyrsites amplified a fragment of the small subunit rDNA and confirmed identification. These primers also allowed detection of K. thyrsites in young (< 4-mo-old) fish with no other apparent sign of infection. No inflammatory response or liquefaction of host tissue was associated with the infection. The number of pseudocysts per infected fish was not correlated with fish size or condition, although larger fish (total length) had larger pseudocysts (rs = 0.437, P < 0.001). This finding brings to 28 the number of potential hosts for the species. Kudoa thyrsites is a well recognized cause of soft flesh in netpen-reared Atlantic salmon in coastal waters of British Columbia. Tube-snouts are common in and around these netpens, and thus may be a significant host reservoir for K. thyrsites.

A new species of Loma (Microsporea) in shiner perch (Cymatogaster aggregata).

Loma embiotocia n. sp. is described from the gills of shiner perch (Cymatogaster aggregata) from waters off Vancouver Island, British Columbia, Canada. Highest prevalence at a site was 15% and greatest intensity was 583 xenomas per fish. Xenomas averaged 0.13 mm in diameter (0.06-0.16 mm) and contained ovoid spores 4.8 x 2.6 (4.0-5.0 x 2.0-3.0) microns. Sporogonic stages were dispersed throughout the xenomas. The xenoma wall was smooth lacking invaginations into the cyto plasm: sporoblasts were not highly vacuolated, and the sporophorous vesicle formed before sporogony. In addition to differences in host and geographic location the new species is distinguished from Loma salmonae, the only other species in the genus known from British Columbia, by its internal transcribed spacer (ITS) ribosomal DNA sequence.

ITS2 ribosomal RNA indicates Schistosoma hippopotami is a distinct species.

The internal transcribed spacer region of the ribosomal RNA, ITS2, was sequenced from a single specimen of S. hippopotami collected from a pulmonary artery of the hippopotamus, Hippopotamus amphibius in South Africa. The nucleotide sequence was aligned with those of S. mansoni, S. rodhaini, S. haematobium, S. intercalatum, S. curassoni, S. bovis and S. japonicum. Both maximum parsimony and genetic distance analyses were performed on these data sets. Using S. japonicum as outgroup to the African schistosomes, a single most-parasmonious tree was obtained of length 64 steps with a consistency index of 1-S. hippopotami was the sister-group to the remaining African species. This species has lateral-spined eggs and its basal position in the tree suggests that this condition is primitive and that terminal-spined eggs developed secondarily. Molecular data clearly show that S. hippopotami cannot be considered synonymous with S. mansoni. Assuming the hippopotamus is the normal host of S. hippopotami, phylogenetic analysis is consistent with an ancient association between schistosomes and ungulates.

Evolutionary factors influencing the nature of parasite specificity.

This article considers how specificity patterns are shaped during the course of parasite evolution. Parasites are first and foremost specific to site, or microhabitat; host ranges are far more subject to change than is microhabitat. Specificity results from a number of convergent phenomena starting with habits (microhabitat and feeding styles) of free-living progenitors and the way in which the parasitic association arises (e.g., passive oral contamination as opposed to intrusive entry). These bias the types of interaction parasites have with the host, and, through this, the way specificity develops. Host ecology acts as an external factor affecting specificity and predominates in parasites that interact minimally with the hosts physiological and immune systems. Coevolutionary factors are more important in parasites that feed on host tissues or occur in extraintestinal sites. Here, parasites must present the right cues, and respond appropriately to the host defense system. The ability to generalize these cues and responses across host boundaries may act as a constraint on host range. The functional role of the host in the parasite life history also affects the degree of specificity; thus, parasites may act as host generalists in hosts that act as trophic channels to the final host. The role of competition in determining specificity is difficult to assess. However, competition has been reported to influence microhabitat and host distribution through interactive site selection and/or competitive seclusion.

Structure of the pinworm (Oxyurida: Nematoda) guild in the hindgut of the American cockroach, Periplaneta americana.

The pinworm (Oxyurida: Nematoda) guild in a laboratory colony of Periplaneta americana was investigated to answer the following questions. (1) Is guild structure stable with time? (2) Is there evidence of interaction among the species? (3) Is there evidence for niche diversification with respect to spatial distribution or developmental stage of host? Four species were found: Thelastoma periplaneticola, Thelastoma bulhoesi, Hammerschmidtiella diesingi and Leidynema appendiculatum; females of the first two could not be distinguished and they were lumped and referred to as Thelastoma sp.; 328 mid-instar hosts were dissected between September 1987 and February 1990, and the number of adult females of each pinworm species was recorded to investigate changes in guild structure through time. Seventy-five percent of hosts had Thelastoma sp., 62% had H. diesingi and 40% had L. appendiculatum; mean intensities were 6.5 (Thelastoma), 2.9 (H. diesingi) and 1.9 (L. appendiculatum). Relative numbers were stable with time and intensities of the species were similar whether they occurred alone in the host or in conjunction with other species. Thelastoma sp. and L. appendiculatum occurred together less often than expected and their numbers in individual hosts were negatively correlated. Both species occurred alone more often than expected. Surprisingly, H. diesingi and L. appendiculatum occurred together more often than expected. Intestines of 44 roaches were frozen in liquid nitrogen and divided into 5 equal sections to study longitudinal distributions of the species in the gut. Most L. appendiculatum and H. diesingi were found in the first, whereas most Thelastoma sp. occurred in the second segment. However, Thelastoma sp. dominated all segments of the gut. Worms were counted in 192 hosts belonging to 4 categories (early instar, late instar, adult male and adult female). Single species infections were more common in early instar hosts but there was no evidence that different species preferred different host stages. Modal distributions in male L. appendiculatum and T. bulhoesi suggest that these species may exhibit intraspecific interference competition similar to that observed in other pinworms. Such effects may be more important than interspecific effects in maintaining guild stability.

Transmission pattern and intraspecific competition as determinants of population structure in pinworms (Oxyurida: Nematoda).

The transmission pattern of Zonothrix columbianus (Nematoda: Oxyurida) in its host Tropisternus columbianus (Coleoptera: Hydrophilidae), an aquatic beetle, was studied to determine whether parasites were dispersed with their hosts and to examine the possible role of intraspecific competition in limiting population size. Beetles were sampled at regular intervals from fall 1986 through fall 1989 and examined for worms. Worms, absent in larval stages of the host, were uncommon in newly metamorphosed beetles and therefore probably do not infect adult stages until after they have dispersed; worms are not dispersed with the host. Prevalence reached its lowest points in spring and fall when newly metamorphosed beetles were most common, but it was near 100% for most of the year. Worms were uniformly distributed in the host population. Many hosts had exactly 1 male and 1 female worm; the high prevalence suggests that this infrahost population results from interference competition between males on the one hand and females on the other. Only 3 of 285 beetles contained more than 1 male. Females shared the host with members of the same sex more commonly than males, but females from hosts harboring more than 1 female had significantly fewer eggs than lone females in hosts. Numbers of adult stages of beetles were estimated during spring, summer, and fall of 1989 and were lower in early spring and late fall. Because worms do not disperse with hosts, the panmictic unit could be estimated from the number of infected beetles; this probably was about 50 individuals during the winter bottleneck.

Lockenloia sanguinis n. gen., n. sp. (Nematoda: Dracunculoidea) from the heart of a nurse shark, Ginglymostoma cirratum, in Florida.

Lockenloia sanguinis n. gen., n. sp. (Nematoda: Dracunculoidea) is described from fragments collected in the atrium of the heart of a male nurse shark, Ginglymostoma cirratum (Bonnaterre). The new genus is distinguished by its reduced buccal capsule; body that expands abruptly just behind the cephalic extremity; long and undivided esophagus; and subconical, pointed tail. Until the systematics of the superfamily are revised, the familial placement of the taxon is unclear.

Prevalence and intensity of Pseudodelphis oligocotti n. gen., n. sp. (Dracunculoidea; Guyanemidae) in the tidepool sculpin, Oligocottus maculosus (Scorpaeniformes; Cottidae).

Pseudodelphis oligocotti n. gen., n. sp. (Dracunculoidea; Guyanemidae) is described from the tidepool sculpin, Oligocottus maculosus (Scorpaeniformes; Cottidae), from various localities in coastal British Columbia. The species is placed in Guyanemidae because of its reduced buccal capsule, divided esophagus, functional vulva, and single ovary. It is distinguished from Guyanema, the only other genus in the family, by the absence of caudal alae and the arrangement of caudal papillae in the male. Females of the new genus are distinguished from those of Guyanema by the presence of a blind uterine diverticulum, without associated oviduct and ovary, extending anteriorly from the junction of the posterior uterus and vagina, and a more posteriorly positioned vulva. Fish were sampled every 2 wk throughout 1988. Worms were overdispersed in the host population. Prevalence and mean intensity of infection were highest from February to March.

Haplodiploidy in the Oxyurida: decoupling the evolutionary processes of adaptation and speciation.

Host distribution and life history variation in the Oxyurida are discussed in the context of haplodiploidy. The Oxyurida have the broadest host distribution of any zooparasitic nematode group but have retained a virtually unchanged life cycle. Like other haplodiploids, oxyuridians have life histories that maintain viscous population structures. It is postulated that this has facilitated speciation but may have discouraged major evolutionary innovation in the group.

Anatomical adaptation to haplodiploidy in the Oxyuroid (Nematoda) Desmicola skrjabini n. sp. from a diplopod in Gabon.

Desmicola skrjabini n. sp. (Oxyuroidea; Nematoda) is described on the basis of female morphology from the hind-gut of Pachybolus sp. ( Pachybolidae ; Spirobolida ; Diplopoda ) from Gabon. The new species differs from the type and only other species in lacking interlabial formations and obvious cephalic papillae, and in having what appear in apical view as finger-like cuticular ornamentations on the anterior surface of the lips. D. skrjabini is didelphic and a seminal receptacle is present in only one branch of the reproductive tract. In oxyuroids , males develop from unfertilized eggs whereas females develop from fertilized eggs. It is suggested that the curious reproductive anatomy of Desmicola ensures production of eggs of both types and therefore offspring of both sexes.

[Haplodiploidy of Oxyurida. Effects of this phenomenon in the life cycle]. / L'haplodiploidie des oxyurida. Incidence de ce phénomène dans le cycle évolutif.

Chromosome behavior during gametogenesis and early cleavage is studied in two species of Thelastomatidae (Oxyurida), Hammerschmidtiella sp. and Thelastoma sp., parasites of diplopods. Both species are shown to be haplodiploid: male with 4 Thelastoma) or 5 (Hammerschmidtiella) chromosomes and double this number in the corresponding female. Haplodiploidy is now known in the 4 families of the Oxyurida and the author concludes that this form of reproduction is characteristic of the entire order. The Oxyuridan life cycle seems simple: 2 moults in the egg, no intermediate host, no extra-intestinal migration. However, several findings (some quite recent) indicate that this life cycle is often complicated by phenomena very closely adapted to host biology. The following particularities are analysed: 1) male progenesis; 2) laying of eggs in agglomerated packets; 3) peri-anal egg deposition; 4) poecilogony; 5) spanandry; 6) traumatic extra-genital insemination; 7) thelytoky. In a final chapter the author relates these adaptations to host biology and attempts to explain how they may have come to be favoured by natural selection during the course of evolution.