Intermediate Copepod Host Research Articles

Life cycle of Amblyospora dyxenoides sp. nov. in the mosquito Culex annulirostris and the copepod Mesocyclops albicans

A new species of Microspora, Amblyospora dyxenoides, is described. This parasite has three sporulation sequences: two in Culex annulirostris, the mosquito host, and one in Mesocyclops albicans, the intermediate copepod host. Diplokaryotic meronts in larval oenocytes persist to the adult stage and form binucleate spores in females which are responsible for transovarial transmission to larval progeny. Unlike other described species of Amblyospora, binucleate spores may also form in adult male mosquitoes. Diplokaryotic cells infect the oenocytes of some male and female larvae which hatch from transovarially infected egg batches. These larvae survive to the adult stage after which binucleate spores develop in the females to initiate another transovarially transmitted cycle. In other male and female larvae which hatch from infected egg batches the parasite invades fat body tissue where it undergoes meiosis during a complex sporulation sequence resulting in the formation of eight haploid meiospores within a sporophorous vesicle. Fat body infected larvae usually die in the 4th instar. Larval meiospores are responsible for horizontal transmission to M. albicans copepods in which the parasite develops in ovarian tissue to form another kind of uninucleate spore. These infections ultimately lead to death of the copepods and the spores are infectious per os to C. annulirostris larvae. The first mosquito stages resulting from these infections are small cells with a single large nucleus relative to the cytoplasm. It appears that the parasite then returns to the diploid state by cytoplasmic fusion (plasmogamy) of uninucleate gametes to form binucleate cells which later adopt the diplokaryotic arrangement and invade larval oenocytes to complete the life cycle.

A scanning electron microscope study of the life cycle of Bothriocephalus acheilognathi Yamaguti, 1934

The stages in the life cycle of Bothriocephalus acheilognathi have been studied with the aid of scanning electron microscopy. Emergence of the coracidium occurred after 3–5 days at 20°C. Soon after hatching the coracidium began to swell and the cilia became coiled and lost their locomotory function. The surface of the coracidium was covered in protuberances of unknown function. After consumption by the copepod intermediate host, the coracidium developed into a procercoid. Upon development of a cercomer the procercoid could infect the fish definitive host. Identification of adult B. acheilognathi should be made on specimens relaxed in cold water for 10 min, and be based on the heart shaped scolex and prominent square apical disc.

Evidence for lack of sclerotization in a microsporidian spore wall

Horizontal transmission testing with anAmblyosporaspecies from the mosquitoCulex salinariushas documented the involvement of a copepod intermediate host. Meiospores (one type of uninucleate spore) of theAmblyosporasp. were infectiousper osto femaleMacrocyclops albidusadults. All developmental stages in the copepod had unpaired nuclei (were haplophasic), starting with the sporoplasms from the meiospore, continuing as a succession of schizonts undergoing binary division and ending with sporulation, producing a second type of uninucleate spore. These spores, formed in the ovaries ofM. albidus,were lanceolate, slightly curved and measured 13.23 × 3.85 μm. They infectedC. salinariuslarvae, both male and female, when ingested. In addition, cross-infectivity testing was conducted and demonstrated that whileA. californicafromC. tarsaliswill infectC. salinarius,it does not complete its life cycle in this host. Based on these findings, we conclude thatAmblyosporasp. fromCulex salinariusis a distinct species and assign it the nameAmblyospora salinarian. sp.

Elaphoidella taroi: The intermediate copepod host in Fiji for the mosquito pathogenic fungus Coelomomyces

Five species of copepods were screened for their ability to transmit Coelomomyces sp. in Fiji. Only one, a common treehole copepod, Elaphoidella taroi, was found to be the intermediate host. When E. taroi was used, the mosquitoes Aedes aegypti, A. pseudoscutellaris, and A. polynesiensis were susceptible to Coelomomyces sp. infection.

Production of the mosquito-parasitic fungus,Coelomomyces dodgei, through synchronized infection and growth of the intermediate copepod host,Cyclops vernalis

High yields of the copepodCyclops vernalis infected with the mosquito-parasitic fungusCoelomomyces dodgeiCouch & Dodge were obtained by infecting nauplii in large synchronously developing populations. Exposure of 2000 48 or 72 h old nauplii to 6×103 sporangia at the time of meiospore release yielded ca. 1500 infected copepods. Based on yields of infected copepods, susceptibility ofC. vernalis toC. dodgei decreased as copepods developed. Infection rates were 75% for copepods exposed as 48 or 72 h old nauplii but declined to 32 and 9.6%, respectively, for those exposed as copepodids or adults. The relevance of these results for domestication of other species ofCoelomomyces and studies on non-target organisms is discussed, and improved procedures for routine production ofC. dodgei are described.

Coelomomyces opifexiPillai & Smith (Coelomomycetaceae: Blastocladiales) VI. Observations on the mode of entry intoAedes australislarvae

Abstract A study was undertaken to elucidate the mode of entry of Coelomomyces opifexi into Aedes australis larvae and the copepod intermediate host, Tigriopus sp. cf. angulatus, using the fluorescent antibody technique coupled with direct examination of whole mounted specimens under the light microscope. Zygotes and zoospores of C. opifexi attached and encysted on the cuticle of mosquito larvae and copepods respectively; their overall distribution on the cuticle is described. Penetration by zygotes and zoospores appears to be mainly confined to the intersegmental membranes. The zygote protoplasm is injected through the cuticle, and forms a hyphal body which may either be released to circulate in the haemolymph or remain attached to the epidermal layer. The development of the hyphal body in the mosquito coelom is discussed.

Population interactions between a parasitic castrator,Probopyrus pandalicola(Isopoda: Bopyridae), and one of its freshwater shrimp hosts,Palaemonetes paludosus(Decapoda: Caridea)

SUMMARYFreshwater shrimp,Palaemonetes paludosus, infected by the bopyrid isopod,Probopyrus pandalicola, occurred as far as 33 km upstream in many coastal rivers and canals throughout Florida. Free-swimming isopod larvae and the intermediate copepod host,Acartia tonsa, were collected in the plankton of the Wakulla River, and it appeared that cryptoniscus larvae swam at least as far as 13 km upstream to infect the definitive shrimp host after leaving the copepod in brackish water. In the Wakulla River infection levels ranged from 87·5 to 100%. In contrast, at McBride's Slough infection levels fluctuated from 0·9 to 93·2%. In the St Marks River the frequency of infected shrimp gradually increased from 0% upstream to 96%, 6 km further downstream. A significantly greater percentage of female than male hosts were infected, but only females of size classes less than 31 mm long had a greater frequency of infection. FemaleP. pandalicolawere greatly under-dispersed (coefficient of dispersion (s2/x¯) less than 1) throughout the host population; 99·6% of the infected hosts carried only 1 female parasite. Control ofP. pandalicolaat the infrapopulation level is probably accomplished by some mode of intraspecific competition, and control at the suprapopulation level occurs through an upstream limitation of the transmission range of the cryptoniscus larval stage. Host–parasite interactions appear to be unstable.

Experimental hybridization of Coelomomyces dodgei and Coelomomyces punctatus

Two closely related fungi, Coelomomyces dodgei and C. punctatus (Chytridiomycetes; Blastocladiales), showing considerable potential for mosquito control, have been hybridized. Both species have life cycles involving an obligate alteration of sexual and asexual generations between an intermediate copepod host and a definitive mosquito host, respectively. Hybridization was accomplished by making reciprocal crosses of gametes derived from infected copepods. In both cases, C. dodgei [unk] x C. punctatus [unk] and C. punctatus [unk] x C. dodgei [unk], zygotes infective for mosquito larvae were formed. Most sporangia produced by the hybrids in infected larvae were not typical of either parental species but resembled C. dodgei more than C. punctatus. Additionally, the majority of the sporangia formed in several larvae exhibited surface structures similar to C. lativittatus, indicating this species may be a naturally occurring hybrid of C. dodgei and C. punctatus. The experimental methods described provide a system to aid in the study of taxonomic relationships among closely related species of Coelomomyces, and furthermore they may contribute to the development of strains efficacious for mosquito control.

Differential pigmentation in the sexual phase of Coelomomyces

THE fungal mosquito parasite, Coelomomyces dodgei (Chytridiomycetes: Blastocladiales), produces gametophytes and gametangia of two different colours, light amber and bright orange, in the intermediate copepod host, Cyclops vernalis. Each gametartgium produces gametes of a corresponding colour. Experimental evidence is presented here which indicates that these differentially pigmented gametes are of opposite mating types, the light amber being female and the bright orange being male, and that zygotes capable of infecting mosquitoes, are produced by their fusion. This differential pigmentation provides a valuable marker for identifying gametes of opposite mating type for experimental purposes, and additionally provides further evidence for a phylogenetic relationship between Coelomomyces and certain other genera of the order Blastocladiales.

Larval metabolism of the epicaridian isopod parasite Probopyrus pandalicola and metabolic effects of P. pandalicola on its copepod intermediate host Acartia tonsa

1. 1. Larval isopods of the parasitic species Probopyrus pandalicola do not consume oxygen at a rate which is a direct function of their body size. Their metabolic rate is dependent mainly on “mode of existence” as well as category of metabolism taking place for a given larval stage. 2. 2. A comparison of the mean metabolic rates between infected and uninfected copepod intermediate hosts Acartia tonsa indicates that oxygen consumption in the host decreases as a result of infection.

A New Species of Proteocephalus Weinland, 1858, (Cestoda), with Notes on Its Life History

From the spring of 1948 to the present time, the author has had the opportunity to examine for parasites more than 100 cut-throat trout, Salmo clarkii Richardson, taken from three small private lakes located near Stevenson, Washington. A total of five species of helminths have been collected from the trout thus far examined. Approximately 90 per cent of the fish were infected with Proteocephalus (P.) primaverus n.sp., and a parasitic copepod, probably of the genus Salmincola Wilson. Parasites encountered only rarely were the following: a trematode, Crepidostomum sp. (?), about twenty specimens from five fish; a cestode, Cyathocephalus sp. (?), one specimen; and an acanthocephalan, Neoechinorhynchus rutili (Mueller, 1780), eleven specimens from three fish. Since the proteocephalid is evidently an unreported species, its description is presented in the following section. The results of preliminary observations on the life history of this parasite are also included. All the helminths were fixed while still alive in either corrosive acetic or formalinalcohol-acetic solutions. If the worms were overly active, they were first allowed to relax in cold tap-water. The greater part of the anatomy of the new species was determined from studies of whole mounts stained in Kornhauser's hematin, while the arrangement of the interovarial organs was reconstructed from serial crosssections stained with Galigher's hematoxylin and eosin. All measurements are given in millimeters, unless otherwise stated, with average values included in parentheses. The drawings were prepared with the aid of a camera lucida. I take this opportunity to thank Dr. Ralph W. Macy for the many helpful suggestions he offered during the course of this study. I would also like to express my appreciation to Mr. Ernest Olson, for supplying the fish from which the parasites were collected, and to Mrs. Mildred S. Wilson, at the Arctic Health Research Center, Anchorage, Alaska, for identifying the copepod intermediate host of the new species. Proteocephalus (P.) primaverus n.sp. (Figs. 1-6) The strobila reaches a maximum length of about 93 and a breadth of 1.0. The scolex is unarmed and may or may not be expanded to form a definite head; it measures 0.68 long by 0.27 broad. The suckers are spherical and directed slightly forward; they measure 0.090-0.135 in diameter. A fifth sucker, apical organ, or rostellum are not present. The neck is not well differentiated from the rest of the strobila, except that it is not segmented; it is 0.15-0.23 broad by about 5 long. The surface of the strobila is non-spinous. There may be as many as 200 proglottids in a gravid specimen. The immature proglottids are approximately twice as broad as long and measure 0.080-0.28 long by 0.26-0.54 broad; the mature proglottids are quadrate and measure 0.43-0.84 long by 0.50-1.0 broad; the ripe proglottids may be square to twice as long as broad and are 0.70-1.75 long by 0.88-0.99 broad; the terminal segment is rounded posteriorly. The genital organs are similar to those of the other members of the genus and subgenus. The genital pores are marginal, from three-eights to five-elevenths of the segment's length from

Experimental Human Infection with the Sparganum Larva of Spirometra Mansonoides (Mueller, 1935) 1

Summary 1. The authors experimentally infected themselves with the sparganum larva of Spirometra mansonoides on November 26, 1938, by introducing the heads of three larvae beneath the skin of the left arm over the biceps muscle, two into Mueller, one into Coulston. These heads measured at most 2 mm. in length. 2. On February 2, 1939 a sparganum 50 mm. in length, representing a growth of 48 mm., was removed from Coulston's arm after it had migrated from the site of injection to the region of the axilla, a distance of about 12 cm., where it was found under the deep fascia. 3. On February 3, 1939 a sparganum 60 mm. long, representing a growth of about 58 mm., was removed from the biceps muscle of Mueller under local anesthetic. Only a fragment of the tail end of the other worm, about 10 mm. long, could be found at this time. 4. On March 4, 1939, a second sparganum about 60 mm. long was removed from Mueller. 5. This last sparganum was fed to an ova-free, known unin-fected cat, and produced a normal adult worm 50 inches in length. Ova of this worm were cultured and the procercoids found infective for rhesus monkeys demonstrating that the worm had not suffered any loss of vigor by human passage. 6. Symptoms associated with infection were local induration at the site of the worm, periodic giant urticaria, edema, and erythema. These periodic symptoms appeared to coincide with movements of the worm which from time to time broke out of the surrounding reaction zone, presumably liberating into the circulation walled off toxins. These periodic local reactions were attended by chills and fever and feelings of profound depression and malaise. 7. Eosinophilia appeared, rising to 10 per cent in Mueller on the 32nd day, and to 9 per cent in Coulston on the 23rd to the 27th day. 8. A positive skin reaction was elicited to scratch tests or intradermal tests with antigens prepared from Spirometra mansonoides adult and sparganum, T. crassicollis adult and cysticercus, T. pisiformis adult and cysticercus, and T. serrata. Also with the substance of a plerocercoid found in Great Lakes ciscoes. Antigens for intradermal use were prepared by Dr. J. T. Culbertson of Columbia University. They were not lipid free. 9. While the subjects were still infected skin testing did not elicit any immediate reaction, only delayed reaction after about 10 or 12 hours. 10. After removal of the worms the subjects developed an immediate reaction to skin tests, while retaining the delayed reaction. The delayed reaction in the case of the scratch tests is recurrent several times at 10 to 12 hour intervals. 11. In over 60 control skin tests on volunteers only one “false positive” was obtained, and that in the case of a student who gave a history suggesting that he may at one time have been infected with a sparganum. 12. The two authors still show strongly positive reactions to skin tests at the present writing (January 8, 1941), almost 20 months after removal of the worms. 13. Complement fixation tests were unsatisfactory on the two experimentally infected humans, possibly because of the employment of too weak an antigen, or more probably because the serum was kept for too long a time before performing the tests. 14. Pathological changes were extensive and in the nature of chronic inflammatory reaction, with local necrotic areas surrounding the worm. 15. In both subjects the spargana exhibited migration, in one case penetrating and forming a gallery in the biceps muscle, in the other passing to the region of the axilla. Encapsulation though extensive was not sufficient to wall off the spargana. 16. With the establishment of Spirometra mansonoides as a potential human parasite physicians throughout the geographic range of the worm should be informed of its nature and educated to watch out for it. The use of antigens of tapeworm substance for diagnosis is recommended. 17. It further appears that this parasite may constitute another potential waterborn disease throughout its range in the eastern United States, and render swimming in certain natural bodies of water carrying the copepod intermediate host, or the use of shallow well or spring water, etc., dangerous. 18. Such antigens as we used are not specific, since they retain the lipid fraction. Spirometra antigens elicited positive reactions in hydatid disease patients. It is probable that a more specific antigen can be prepared by preliminary removal of the lipids before extraction.