Communications: Agglutination of Salmonid Spermatozoa by Renibacterium salmoninarum

Abstract

Renibacterium salmoninarum (American Type Culture Collection: ATCC 33209) agglutinated spermatozoa of brook trout Salvelinus fontinalis, rainbow trout Oncorhynchus mykiss, chinook salmon O. tshawytscha, white sucker Catostomus commersoni, and goldfish Carassius auratus, but not that of walleye Stizostedion vitreum or bulls Bos taurus. When examined microscopically, the bacteria were seen to be binding to the tails but not the heads of the sperm. The sperm agglutinin may be the previously reported renibacterial hemagglutinin.     

A Digenean Metacercaria (Apophallus sp.) and a Myxozoan (Myxobolus sp.) Associated with Vertebral Deformities in Cyprinid Fishes from the Willamette River,Oregon

Abstract

A high prevalence of vertebral deformities has been observed in various fishes, especially cyprinids, from certain regions of the Willamette River for many years. One proposed source of these deformities is exposure to toxicants. Histological evaluation of affected chiselmouth Acrocheilus alutaceus revealed that all lesions associated with vertebrae were associated with metacercariae of digenean trematodes. Approximately half of the northern pikeminnow Ptychocheilus oregonensis had infections in which metacercariae were associated with these lesions. Metacercariae were also associated with vertebral lesions in three of four affected peamouth Mylocheilus caurinus. Many metacercariae that were present within the vertebral bodies were associated with bony dysplasia and bony proliferation in all three species. We also evaluated the association of the metacercariae with the vertebral deformities, using intact fish that had been cleared with trypsin. Fish from the affected regions had a much higher prevalence of metacercariae and deformities and a greater abundance of metacercariae than those in the reference site. Chiselmouths had more deformities and metacercariae than northern pikeminnow. In all fish species, 77% of deformities were directly associated with metacercariae; in chiselmouths, about 95% of the deformities exhibited this relationship. Two types of metacercariae were identified in affected fish: Apophallus sp. (Heterophyidae) and a neascus type (Strigeidida). The Apophallus sp. appeared to be more closely associated with the skeleton deformities. A Myxobolus sp. morphologically similar to M. cyprini was also associated with the vertebral lesions in about 50% of the northern pikeminnow and 5% of the chiselmouths. Intact plasmodia were found in somatic muscle, and lesions containing free spores were often located at bone surfaces. This survey demonstrates that metacercariae (probably Apophallus sp.) and a Myxobolus sp. are major causes of the vertebral deformities seen in cyprinid fishes from certain regions of the Willamette River.     

Some Copepod and Isopod Parasites of Bermuda Marine Fishes

Abstract

Three species are added to the depauperate parasite fauna of Bermuda: Caligus balistae, Lernanthropus talipes, and Alcirona insularis. The latter, normally a rare associate, seems to thrive on groupers (Serranidae) in captivity. An offshore record for Nerocila lanceolata on ocean triggerfish Canthidermis sufflamen contrasts with its known nearshore occurrence. A new host record is noted for each of four parasites occurring in Bermuda: Caligus balistae, A. insularis, Cymothoa oestrum, and N. lanceolata     

Pseudorhabdosynochus kritskyi n. sp. (Monogenea: Diplectanidae) on Gag from the Gulf of Mexico

Abstract

Pseudorhabdosynochus kritskyi n. sp. from gag Mycteroperca microlepis (Perciformes: Serranidae) of the Gulf of Mexico is described and differs from all known species of the genus by the shape of the vagina. It may be further differentiated from P. americanum, P. amplidiscatum, P. caballeroi, P. epinepheli, P. latesi, P. monaensis, and Cycloplectanum magnisquamodiscum in having fewer rows of scales in each squamodisc. This new species is most similar to P. beverleyburtonae, P. bocquetae, P. cupatum, P. lantauensis, P. melanesiensis, P. querni, P. serrani, P. summanae, P. vagampullum, and Cycloplectanum riouxi in having 15 or fewer squamodisc rows, but it may be separated by differences in either squamodisc morphology or differently shaped hamuli or bars.     

Serological Analysis of Thermolabile Antigens of Vibrio anguillarum

Abstract

Serological analysis of thermolabile antigens of representative strains belonging to the J-O-1, J-O-2, and J-O-3 serotypes of Vibrio anguillarum, which are the major serotypes of thermostable antigens (O-antigens) in Japan, showed that the strains belonging to each O-serotype possessed a common thermolabile antigen designated as k-1. In addition to the k-1 antigen, strains of the J-O-1 serotype of biovar II V. anguillarum possessed another antigen designated as k-2. These findings were confirmed by examining additional strains belonging to each O-serotype. The k-1 antigen was found in all the strains of J-O-4, J-O-5, J-O-6, J-O-7, and J-O-8 serotypes, which are minor serotypes in Japan. The same antigen was also found in some strains of V. metschnikovii, Aeromonas hydrophila, and A. salmonicida.     

The effect of defoliation and competition on the regrowth of Themeda triandra and Aristida junciformis subsp. junciformis

Abstract

The effects of a cutting trial, conducted to study the combined influence of defoliation and competition from surrounding vegetation on the vigour of Themeda triandra and Aristida junciformis, were evident after the single season of treatment implementation. Aristida junciformis was more sensitive to defoliation than T. triandra, whereas competition reduced yield to a greater extent in T. triandra than in A. junciformis. The two species differed in their ability to tolerate defoliation under competition. Defoliation reduced the yield of A. junciformis, at all levels of competition, to a greater extent than T. triandra. Aristida junciformis was particularly sensitive to a combination of severe defoliation and full competition. It is suggested that manipulation of grazing patterns may shift the competitive balance between palatable (e.g. T. triandra) and unpalatable (e.g. A. junciformis) components of the sward.     

Fish-Eating Birds as Potential Vectors of Edwardsiella ictaluri

Abstract

Intestinal and rectal smears from 137 birds (4 snowy egrets Egretta thula, 22 great egrets Casmerodius albus, 30 great blue herons Ardea herodias, and 81 double-crested cormorants Phalacrocorax auritus) were examined by indirect fluorescent antibody test for the presence of Edwardsiella ictaluri. Edwardsiella ictaluri was detected in 53% of the birds sampled. Rectal samples from eight birds were placed in a special antibiotic broth for isolation of viable E. ictaluri. Two of these samples produced colonies of viable E. ictaluri, and the identity of these colonies was confirmed biochemically and serologically.     

Communications: Viability of Bacterial Pathogens in Frozen Fish

Abstract

Channel catfish Ictalurus punctatus injected with Aeromonas hydrophila, Pseudomonas fluorescens, Edwardsiella tarda, or E. ictraluri were frozen at ?20°C after death. Bacterial isolation at 2-d intervals after freezing indicated that A. hydrophila could be recovered for 20 d, P. fuorescens for 60 d, E. tarda for 50 d, and E. ictaluri for 30 d in frozen fish.     

Behavior of Rocinela angustata (Isopoda,Aegidae), an Ectoparasite of Alaskan Marine Fishes

Abstract

Observations were made on the feeding and host selection behavior of the aegid isopod Rocinela angustata. Host susceptibility was assessed by placing isopods into laboratory tanks containing 14 common species of Alaska marine fishes. Five species of Sebastes and Blepsias bilobus were attacked within a few minutes of the introduction. Five species—Enophrys bison, Eumicrotremus orbis, Hexagrammos lagocephalus, Pleuronectes asper, and Pholis laeta—were attacked 10–24 h after introduction of the isopods. Three species—Podothecus acipenserinus, Liparis gibbus, and Lycodes brevipes—were not successfully attacked, even when held in isolation with an isopod for 14 d. Starved isopods isolated with B. bilobus attached to fish within 1 h and remained attached 4–14 d. The isopods reattached 1–4 d after detachment. Isopod digestive tracts cleared within 24 h after detachment.     

Role of Low-Molecular-Weight Ciliostatic Toxins in Vibriosis of Bivalve Mollusks

Abstract

Toxins play a major role in bacillary necrosis of hatchery-reared bivalve larvae. Two principal types of toxin of Vibrio spp. have been identified: A proteinase (molecular weight = 40,000) that degrades connective tissue and at least one ciliostatic toxin (molecular weight = 500–1,000). The ciliostatic toxin is stable at 100°C for 10 min and probably accounts for the cessation of feeding and swimming in the early stages of bacillary necrosis. Ciliostatic toxins were produced by 17 of 20 Vibrio spp. that are pathogenic to fish or that were isolated from diseased mollusks and included Vibrio tubiashii, V. anguillarum, and V. alginolyticus. Of 53 Vibrio and Aeromonas isolates not associated with bivalve infections, only 15 produced a ciliostatic toxin.     

Development of Immunity by the Tomato Clownfish Amphiprion frenatus to the Dinoflagellate Parasite Amyloodinium ocellatum

Abstract

The dinoflagellate Amyloodinium ocellatum, which causes amyloodiniosis or “marine velvet disease,” is one of the most serious ectoparasitic diseases affecting warmwater marine fish culture worldwide. We demonstrated that tomato clownfish Amphiprion frenatus can develop strong immunity to infection following repeated nonlethal parasitic challenges. The protective response is long-lived and directed against the trophont stage of the parasite.     

Nucleotide Sequences Homologous to Mammalian Proto-oncogenes and Their Expression in Fish Cell Lines

Abstract

It has been shown that mammalian proto-oncogenes may be centrally involved in cell transformation in vitro and the formation of tumors in vivo. As part of a study on the evolutionary aspects of tumor formation, we have screened cell lines derived from brown bullhead Ictalurus nebulosus (BB), rainbow trout Oncorhynchus mykiss (RTG-2), common carp Cyprinus carpio (EPC), and chinook salmon Oncorhynchus tshawytscha (CHSE-214) for the presence or expression of sequences homologous to the mammalian proto-oncogenes. Southern blotting of DNA isolated from the fish cell lines showed multiple fragments having homology to v-src, v-raf, v-ras ^h, and v-erb-b DNA probes. In addition, monoclonal antibodies against the viral or cellular oncogenes of mammalian cells were able to recognize fish proteins that may be related to the myc, abl, fos, ras ^k, and p53 gene products. This study shows that proto-oncogenes are well conserved evolutionarily in vertebrates and may be factors involved in the acquisition of the transformed phenotype in fish.     

Communications: Isolation of Several Mycobacterium Species from Fish

Abstract

Several species of marine fish caught in the wild and of freshwater ornamental fish were used in this study. Infected organs (liver, spleen, and kidney) were sampled for mycobacteria. Decontaminated tissue samples were plated onto selective media for mycobacterial recovery. After initial isolation, fluorescent and acid-fast staining techniques identified bacterial colonies to genus. Profiles of biochemical growth characteristics were used to further identify the isolates to species. Five species of Mycobacterium were identified: M. simiae, M. scrofulaceum, M. marinum, M. chelonae, and M. fortuitum. Of these, M. simiae and M. scrofulaceum have not been previously reported from fish. Tissue samples containing focal granulomatous lesions were prepared for electron microscopic examination.     

Mitochondrial DNA sequence analyses in Bornean sucker fishes (Balitoridae: Teleostei: Gastromyzontinae)

Phylogenetic relationships among Bornean sucker fishes (Teleostei: Balitoridae: Gastromyzontinae) were investigated by comparing cytochrome b gene sequences from eight species. The results were in general agreement with previous morphology‐based studies. It was found that the genera Gastromyzon and Neogastromyzon are both monophyletic and that the Chinese homalopterid Crossostoma lacustre (Homalopterinae) is not related to the Bornean species. This molecular‐level study of cytochrome b gene variation in Bornean gastromyzontins will undoubtedly help to shed light on the molecular systematics of this unique freshwater fish.     

Susceptibility of Six Bacterial Pathogens of Channel Catfish to Six Antibiotics

Abstract

Two hundred eight bacterial isolates from diseased channel catfish Ictalurus punctatus were screened for susceptibility to apramycin, enrofloxacin, cephalothin, oxytetracycline, sulfadimethoxine-ormetoprim, and tilmicosin by the Kirby-Bauer disk diffusion method. Bacteria evaluated were Edwardsiella ictaluri, E. tarda, Aeromonas sp., A. hydrophila, A. sobria, and Pseudomonas sp. All bacteria were most susceptible to enrofloxacin (99.0%) and apramycin (97.6%), but only 86.5% were susceptible to sulfadimethoxine-ormetoprim, 84.1%o to oxytetracycline, and 75.5% to cephalothin. Edwardsiella ictaluri, E. tarda, A. hydrophila, and A. sobria were 100% susceptible to enrofloxacin. Aeromonas sp., E. ictaluri and E. tarda were 100% susceptible to apramycin. Resistance was detected in all bacterial species to cephalothin, oxytetracycline, sulfadimethoxine-ormetoprim, and tilmicosin. Testing E. ictaluri against sulfadimethoxine-ormetoprim gave larger zones of inhibition on Mueller-Hinton medium than on brain-heart infusion agar.     

Small Subunit rRNA Gene Comparisons of Four Actinosporean Species to Establish a Polymerase Chain Reaction Test for the Causative Agent of Proliferative Gill Disease in Channel Catfish

Abstract

Proliferative gill disease (PGD) causes high morbidity and mortality in cultured channel catfish Ictalurus punctatus. The presence of the myxozoan Aurantiactinomyxon ictaluri (class Actinosporea) is strongly associated with PGD. This parasite, shed as an actinospore from the aquatic oligochaete Dero digitata, infects channel catfish by an undetermined route. Several other actinosporeans have been identified that are shed from D. digitata isolated from catfish ponds, including those designated A. mississippiensis, Helioactinomyxon sp., and the actinospore stage of Henneguya exilis. By the use of multiple sequence alignment of polymerase chain reaction (PCR)-amplified small subunit ribosomal RNA (SSU rRNA) genes of A. ictaluri, A. mississippiensis, and H. exilis, we identified two variable regions. The largest variable region was PCR amplified, sequenced from the Helioactinomyxon sp., and used in addition to the other three sequences in multiple-sequence alignment comparison to develop PCR primers specific for A. ictaluri. This PCR specific for A. ictaluri produced 104-base-pair products from a plasmid clone containing the SSU rRNA gene of A. ictaluri, spore DNA of A. ictaluri, and DNA prepared from channel catfish gill and D. digitata infected with A. ictaluri. The PCR assay was able to detect as few as 100 copies of the cloned gene. There was no detectable product from the genomic DNA of H. exilis, A. mississippiensis, or Helioactinomyxon sp., specific pathogen-free channel catfish gill, and noninfected D. digitata. The PCR assay will be useful as a diagnostic tool for PGD in channel catfish and will aid in the elucidation of the life cycle of A. ictaluri.     

Morphology and histology of the adult Paramphistomum gracile Fischoeder, 1901

In the present study, we evaluated the histological morphology of the adult Paramphistomum (P.) gracile. Adult flukes with bodies 5~15 mm in length and 2~7 mm in width were subjected to histological analysis. Longitudinal and transversal serial-sections were stained with hematoxylin and eosin, and examined. The body surface and longitudinal section of P. gracile were also assessed using scanning electron microscopy. In this species, the anterior sucker and posterior sucker (acetabulum) were present on an anterior and posterior part of the body, respectively. The major folds were located in the areas of the anterior sucker, genital canal, and posterior sucker. The fluke membrane was spineless at the tegument surface and in the tegument tissue. Histological data showed structural-systematic characteristics of the digestive tract, reproductive tract, excretory tract, copulatory organs, connective tissues, and muscle tissues. We attempted to elucidate the histological characteristics of P. gracile that might increase the knowledge and understanding of rumen fluke morphology.     

A comparison of the methods for determination of the rennet coagulation properties of milk

Abstract

The objective of the present study was to compare two methods for measuring the rennet coagulation properties of milk: the Formagraph, and the Optigraph. The parameters used to describe rennet coagulation of 81 milk samples were rennet coagulation time (RCT, Formagraph, and R, Optigraph) and curd firmness 30 min after the addition of rennet (E₃₀, Formagraph, and A₃₀, Optigraph).

New Optigraph system recipes were found: R slope?=?1.784 and R offset?=???2.303. Using the above Optigraph system recipes, no statistically significant differences were found in rennet coagulation time measurements in either of the studied methods. Regarding curd firmness, the best approximation to describe the relationship between the methods was polynomial: E₃₀=???0.0357*A₃₀ ²+2.8795*A₃₀ ?5.2991 (R ² =0.925). Such strong correlations indicate that the two techniques for detecting milk coagulation properties are comparable and that the data obtained by these methods allow for data interpretation in studies using either method.