我国内陆水体单殖吸虫的宿主特异性分析

报道我国内陆水体单殖吸虫的宿主特异性的研究。研究表明单殖吸虫有很强的宿主特异性,但不同种类的特异的有很大的判别。从目前已有的记录来看,６０％以上的单殖吸虫中只有１种宿主,约７５％的单殖吸虫的宿主仅为１属,超过９７％的单殖吸虫的宿主在１科之内。没有１种单殖吸虫可生于超过３个料的宿主中,但大钩指环虫可在２３属３３种宿主中寄生。在科和发放持异性水平,以锚首虫科和指环虫科单殖吸虫的特异性较强,三代虫科次之     

Monogeneans in introduced and native cichlids in México: evidence for transfer

We examined 2 cichlid fish species native to México, Cichlasoma callolepis and C. fenestratum, and 2 introduced African cichlids, Oreochromis aureus and O. niloticus, from 3 localities in southeastern México for monogeneans. Six monogenean species infected the African cichlids: Cichlidogyrus haplochromii, C. dossoui, C. longicornis longicornis, C. sclerosus, C. tilapiae, and Enterogyrus malmbergi. We found all these parasite species, except C. haplochromii and C. dossoui, on the native C. fenestratum and C. callolepis. Prevalences of Cichlidogyrus spp. were 3-10% and abundances ranged from 0.03 +/- 0.2 to 0.1 +/- 0.3 for native cichlids. We only recovered a single E. malmbergi from 1 C. callolepis. We found Sciadicleithrum bravohollisae, a monogenean of native Cichlasoma spp., on the gills of the introduced O. aureus from Lake Catemaco (prevalence 3%, abundance 0.03 +/- 0.2). Although prevalence and abundance in atypical hosts were fairly low, the present findings provide evidence of monogenean transfer from African to American cichlids and vice versa. This is the first record of exotic monogeneans in the genus Cichlidogyrus and Enterogyrus infecting native American cichlid fish. It is also the first record from southeastern México of a native American monogenean infecting introduced African cichlids.     

A list of monogeneans from Chinese marine fishes

This paper contains a brief history of studies on monogeneans of Chinese marine fishes and a list of 337 monogenean species, together with their marine hosts and notes on the sea in which they were found. An additional 139 species have been added to the 198 species recorded in `Monogeneans of Chinese Marine Fishes' published by Zhang, Yang and Liu in 2001.     

Phylogenetic study of nine species of freshwater monogeneans using secondary structure and motif prediction from India

The present study was performed to identify and validate monogenean species from different piscine hosts using molecular tools. Nine species of freshwater monogeneans were collected from gills and skin of freshwater fishes at Hastinapur, Meerut, India. After microscopic examination, molecular analysis was performed utilizing 28S gene marker. Phylogenetic analysis indicated the validation and systematic position of these nine different monogeneans belongs to the Dactylogyridae and Gyrodactylidae families. The findings also confirm that the 28S rDNA sequence is highly conserved and may prove to be useful in taxonomic studies of parasitic platyhelminthes. Besides this, the study is also supplemented by molecular morphometrics that is based on 28S secondary structure homologies of nine monogenean species. The data indicate that 28S motifs i.e., ≤ 50bp in size can also be considered a promising tool for monogenean species identification and their validation.     

Are all species of Pseudorhabdosynochus strictly host specific? — A molecular study

Species of the diplectanid monogenean genus Pseudorhabdosynochus are strictly host-specific (specialist), with the exception of P. cyanopodus, which was reported in New Caledonia, South Pacific, from two host species, Epinephelus cyanopodus and E. chlorostigma. We sequenced the COI gene of both host fish species and of their monogeneans. Morphological identification and pairwise distances showed that the two fish species were distinct (difference 6.1-6.6%), but that their monogeneans were not (difference 0-1.5%). A morphological study of sclerotised parts showed that specimens of P. cyanopodus are similar in both fish. Most species of groupers and their associated Pseudorhabdosynochus species are from warm surface waters, but the two groupers E. cyanopodus and E. chlorostigma are usually caught in deep-sea on the outer slope of the coral reef. This suggests that acquisition of a less strict host specificity is an adaptation of P. cyanopodus to deep-sea hosts.     

Kuhnia sprostonae Price, 1961 and K. scombercolias Nasir & Fuentes Zambrano, 1983 (Monogenea: Mazocraeidae) and their microhabitats on the gills of Scomber australasicus (Teleostei: Scombridae), and the geographical distribution of seven species of gill Monogenea of Scomber spp.

As a result of an extensive survey of monogeneans on the gills of scombrid fishes of the genus Scomber, especially S. australasicus in Australia, it has been shown that Kuhnia sprostonae as previously defined by Rohde & Watson is, in fact, two distinct species, namely K. sprostonae Price, 1961 and K. scombercolias Nasir & Fuentes Zambrano, 1983. K. sprostonae inhabits the pseudobranchs of Scomber scombrus in the North Sea, S. japonicus off Madeira and S. australasicus in Australian waters, and shows considerable variability in the lengths of the hamuli and the genital hooks. K. scombercolias occurs on the main gills of S. japonicus and S. australasicus in many regions of the Atlantic and Indo-Pacific. Other species of gill monogeneans on Scomber spp. are Kuhnia scombri, Pseudokuhnia minor, Grubea cochlear and G. australis. A damaged juvenile monogenean of unknown status was recovered only once in the Mediterranean. The geographical distribution of gill monogeneans of Scomber spp. is discussed.     

Mating rendezvous in monogenean gill parasites of the humbug Dascyllus aruanus (Pisces: Pomacentridae)

The gills of the humbug, Dascyllus aruanus (Pomacentridae), were infected by a monogenean genus Haliotrema at a high prevalence (83%) but with a low mean intensity (5.6 worms/fish). All the gill arches of 365 fish, caught on the fringing reef of Moorea Island (French Polynesia), were examined for parasites. Each hemibranch was divided into 12 subequal sections. Monogeneans showing microhabitat overlap were defined as couples. Hosts with low intensity of infection (fewer than 5 monogeneans per gill) were selected and couples were recorded. Among the 37 hosts harboring 2 worms on their gills, 18 fish were infected with these 2 monogeneans on the same gill side of the body; 50% (n = 9) of these harbored monogeneans within the same gill arch and 55% (n = 5) of these last fish showed individual parasites within the same section of the gill. In the case of hosts with few monogeneans (3 and 4 individuals; n = 37) on the same arch, more than 40% (n = 16) harbored worms in couples. There may be some chemical communication that allowed these monogeneans to migrate toward each other and thus enhance mating success. Mating rendezvous appears to be a more important factor than site location for these gill monogeneans.     

A new species of Polystomoides ward, 1917 (Monogenea: polystomatidae) from freshwater chelonians (Testudines: chelidae) in Brazil

This report describes the first occurrence of Polystomoides brasiliensis n. sp. (Monogenea: Polystomatidae), a new monogenean species in the buccal and pharyngeal cavities of the freshwater turtles in Brazil. Live monogeneans were collected from Hydromedusa maximiliani and Phrynops geoffroanus at the Mariano Procópio Museum's lake, in Juiz de Fora, Minas Gerais, Brazil. Polystomoides brasiliensis differs from all other species of this genus in having 8-9 genital spines, except for Polystomoides uruguayensis, which has 8-10 genital spines. However, the new species differs morphometrically from P. uruguayensis in the greater size of the outer and inner hamuli, as well as having a testis that is proportionally greater than the pharynx and oral sucker. The current study is the first report of monogeneans in chelonians of Brazil, and the first record of helminths in H. maximiliani.     

Spatial distribution and coexistence of monogenean gill parasites inhabiting two damselfishes from Moorea island in French Polynesia

The ectoparasite fauna of two damselfishes, Stegastes nigricans and Dascyllus aruanus, from Moorea Island in French Polynesia was investigated. Gills of these damselfishes were infected with congeneric Monopisthocotylea Monogenea belonging to the genus Haliotrema. Stegastes nigricans were found to harbour a guild of three Haliotrema species whereas only one species inhabited D. aruanus. Microhabitat distribution, inter- and intraspecific competition and interspecific associations on the gill were studied. Observations on site preference revealed no spatial segregation between the three congeneric species inhabiting the gills of S. nigricans. Juvenile and adult monogeneans of that guild occurred on the same microhabitat. The dominant species Haliotrema sp. 1 did not expand on the microhabitat when the intensity of infection increased. Interspecific association tests revealed positive and negative associations. Haliotrema sp. 4 expanded its distribution on the gills of Dascyllus aruanus when the intensity of infection increased suggesting the likelihood of intraspecific competition. Juvenile and adult monogeneans of Haliotrema sp. 4 appeared to segregate as a result of intraspecific competition. This competition may exist to enhance resource availability when the gill habitat is limited. Overlaps between niche breadth and species microhabitat were revealed for monogenean species inhabiting S. nigricans. Interspecific competition did not appear to play an important role in the distribution of S. nigricans congeneric ectoparasites. Reinforcement of reproductive barriers may have led to the avoidance of hybridization.     

Introduction of Alien Host–parasite Complexes in a Natural Environment and the Symbiota Concept

When a species is introduced in a new territory its parasites may also follow, thus forming a sort of biotic unit. We propose the term symbiota to indicate this host–parasite complex. This concept is at the basis of the present research in which 11 species of alien and native freshwater fish were collected by electrofishing in the Po river area (Northern Italy). The alien host fish Ictalurus melas and Silurus glanis were parasitized by only one monogenean species each. Lepomis gibbosus, of North American origin, hosted four monogeneans and Carassius carassius three. All these parasites should be considered as alien species, except those collected from C. carassius that should be considered in part natives and in part aliens.     

Parasites in marine protected areas: success and specificity of monogeneans

The effect of a marine protected area on the Lamellodiscus spp. monogenean community was tested by comparing the communities of parasites of Diplodus sargus inside and outside of the area. A total of 104 D. sargus were dissected harbouring 1280 monogeneans from the genus Lamellodiscus and belonging to 11 species. No modification in the global parasite community linked with the protection of the host populations was revealed. The most abundant and less specific parasite species, Lamellodiscus elegans , however, increased its abundance in the protected area. A significant relationship was found between parasite host range and the percentage of infected hosts. A significant relationship also occurred between epidemiological and genetic distances for the parasite species found. The results are discussed in term of parasite success and specificity and the importance of taking into account parasitism in the biological conservation of hosts.     

New species of the Monocotylidae (Monogenea) from the stingray Dasyatis tortonesi Capapé (Euselachii,Dasyatidae) off the Tunisian coast,with comments on host-specificity and the specific identities of Mediterranean stingrays

Heterocotyle capapei n. sp. and Thaumatocotyle tunisiensis n. sp. are described from the gills and the nasal cavity, respectively, of Dasyatis tortonesicollected from the Tunisian coast. H. capapei is distinguished from other species in the genus by the morphology of the penis, which is conical and has a long narrow distal point. T. tunisiensis differs from all known species of Thaumatocotyle by the shape and size of the penis. The host Dasyatis tortonesi has long been confused with D. pastinaca. Our study shows that their monogeneans are oioxenic, suggesting that D. pastinaca and D. tortonesi are distinct species. These results suggest that the monogenean parasite fauna could be used as a diagnostic tool for species identification: these parasites may, therefore, represent good biological indicators. The host-specificity of the Heterocotylinae and Merizocotylinae is discussed.     

Mosaic or melting pot: The use of monogeneans as a biological tag and magnifying glass to discriminate introduced populations of Nile tilapia in sub-Saharan Africa

The origin of introduced Nile tilapia stocks in sub-Saharan Africa is largely unknown. In this study, the potential of monogeneans as a biological tag and magnifying glass is tested to reveal their hosts' stocking history. The monogenean gill community of different Nile tilapia populations in sub-Saharan Africa was explored, and a phylogeographic analysis was performed based on the mitogenomes of four dactylogyrid species (Cichlidogyrus halli, C. sclerosus, C. thurstonae, and Scutogyrus longicornis). Our results encourage the use of dactylogyrids as biological tags. The magnifying glass hypothesis is only confirmed for C. thurstonae, highlighting the importance of the absence of other potential hosts as prerequisites for a parasite to act as a magnifying glass. With the data generated here, we are the first to extract mitogenomes from individual monogeneans and to perform an upscaled survey of the comparative phylogeography of several monogenean species with unprecedented diagnostic resolution.     

New monogeneans from the bathydemersal southern African endemic catshark,Holohalaelurus regani (Gilchrist, 1922)

The catshark genus Holohalaelurus Fowler is currently represented by five species distributed off the southern and eastern parts of the African coast. Very few parasitological records exist for any of these five species, representing a significant knowledge gap. We report the first monogenean species from the bathydemersal species Holohalaelurus regani (Gilchrist): a new species of Microbothriidae Price, 1936, Leptomicrobothrium holohalaelure n. sp. from the dorsal skin surface, and a new species of Hexabothriidae Price, 1942 representing a new genus, Scyliorhinocotyle narvaezae n. gen., n. sp., from the gill lamellae. Both monogenean records represent the first for any member of the catshark genus Holohalaelurus. Previously we focused on the identification of monogenean taxa of emerging veterinary importance for public aquaria. We now begin a focused effort to document a generally unexplored monogenean biodiversity from diverse marine habitats off South Africa.

     

Gill monogeneans of the chub mackerel, Scomber japonicus from Madeiran waters of the Atlantic Ocean, Portugal

Five species of monogeneans were recovered from the gill filaments of 181 chub mackerel, Scomber japonicus, from the Madeiran waters of the Atlantic Ocean, Portugal, during 2004/2005. The monogenean Pseudokuhnia minor showed the highest prevalence (98.68%) and a mean intensity of 28.23, followed by Kuhnia scombri (prevalence of 43.71% and mean intensity of 2.69) and K. scombercolias (prevalence of 39.1% and a mean intensity of 1.81). Kuhnia sprostonae and Grubea cochlear were rare, occurring in only one and five fish hosts respectively. No correlation between fish host length and mean intensity of infection with the three most abundant monogeneans was found. However, significant differences in prevalence and abundance were found in relation to date of sampling for P. minor, and all parasites were aggregated in their distribution.     

Can host body size explain the parasite species richness in tropical freshwater fishes?

Summary The variability of monogenean gill ectoparasite species richness in 19 West African cyprinid species was analyzed using the following seven predictor variables: host size, number of drainage basins, number of sympatric cyprinid species, host diversity, association with mainland forest, host ecology, and monogenean biological labelling. The size of the host species accounted for 77% of the variation in the number of parasite species per host, and host ecology an additional 8%. Together the effects of host size and host ecology accounted for 85% of the variation in monogenean species richness. This study shows that the deciding factors for explaining monogenean species richness in West African cyprinid fishes are host species size and host ecology. These results were compared with main factors responsible for parasite species richness in fish communities. Other possible explanations of monogenean community structure in west African cyprinids are discussed.     

Ultrastructural Observations on Fertilization in Dionchus remorae (Platyhelminthes,Monogenea, Dionchidae)

Ultrastructural observations are presented for some of the stages occurring during fertilization in Dionchus remorae (a gill parasite of Echeneis naucrates) and are believed to be the first published concerning a monogenean. Fertilized female germ cells were found in the ovary. Several loops of the spermatozoon were present within the oocyte cytoplasm; the sperm nucleus became electron lucent and the parallel peripheral doublets of the axonemes became increasingly divergent. The cortical granules in the oocyte were not released immediately after penetration by the spermatozoon. The homogeneity apparently found in the oocyte ultrastructure and process of fertilization in the monogeneans and digeneans contrasts with the variety that exists in their sperm ultrastructure.