Two new and one newly recorded gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) parasitising marine fishes in Iraq.

Specimens of two undescribed and one known gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) were collected in some marine fishes from off the southern coast of Iraq. Based on light and scanning electron microscopy, the following new species are described: Philometra tayeni n. sp. (males and nongravid females) from ovaries of the purple-spotted bigeye Priacanthus tayenus Richardson (Priacanthidae, Acanthuriformes), and Philometra nibeae n. sp. (males and gravid female) from the ovary of the blotched croaker Nibea maculata (Bloch et Schneider) (Sciaenidae, Acanthuriformes). Philometra tayeni is mainly characterised by a pair of postanal papillae and a V-shaped caudal mound in males and by their body lengths (2.42-2.99 mm), whereas P. nibeae differs from its gonad-infecting congeners parasitising scienids mainly based on the body length of males (2.29-2.49 mm) and their spicules (96-117 µm), absence of a pair of postanal papillae and shape of caudal mound consisting of two parts. Philometra piscaria Moravec & Justine, 2014 (males and nongravid females), a parasite of the orange-spotted grouper Epinephelus coioides (Hamilton) (Epinephelidae, Perciformes), is recorded from the Arabian (= Persian) Gulf for the first time; previously unknown females of this species are described.

Strigea robusta (Digenea: Strigeidae) infection effects on the gonadal structure and limb malformation in toad early development.

The anomaly P is a mass morphological anomaly reported in some water frog populations across Europe. It was found that polydactyly is only a mild attenuated form of heavy cases of the anomaly P syndrome, which have strong deformations of the hindlimbs and, partly, forelimbs. It was shown that the anomaly P is caused by the trematode Strigea robusta and this syndrome can be considered as a special case of strigeosis in amphibians. The anomaly P for a long time considered to be specific for water frogs of the genus Pelophylax. Herein, we describe polydactyly and heavy forms of the anomaly P syndrome in toads of the genera Bufo and Bufotes, as a result of exposure to S. robusta cercariae. A total of 150 tadpoles of Bufo bufo, 60 tadpoles of Bufotes viridis, and 60 tadpoles of Bufotes baturae were divided into five experimental and four control groups (30 tadpoles in each group). All anomalies in the toads were similar to those observed in water frogs. The survival of tadpoles in the experimental groups was 76%. The anomaly P was observed in 57.9% of toad tadpoles (51.8% of mild forms and 6.1% of heavy forms). The occurrence of the anomaly P varied among groups from 19% to 78%. Heavy forms of the anomaly P were found in all experimental groups. We described rare asymmetrical cases of the anomaly P. According to severe modification of limb morphology, we supposed changes of gonadal morphology (any modifications of the germ and somatic cells). The gonadal development of infected tadpoles was however the same as in uninfected toad tadpoles, and heterochromatin distribution within gonocytes had no differences as well. It seems like the parasite doesn't have any effect on the gonadal development of the toads. The lack of heavy forms in natural populations of toads, as well as a development of gonads were discussed.

An efficient photograph-based quantitative method for assessing castrating trematode parasites in bivalve molluscs.

Parasitic castration of bivalves by trematodes is common, and may significantly reduce the reproductive capacity of ecologically important species. Understanding the intensity of infection is desirable, as it can indicate the time that has passed since infection, and influence the host's physiological and reproductive response. In addition, it is useful to know the developmental stage of the trematode, to understand trematode population trends and reproductive success. However, most existing methods (e.g. visually estimating the degree of infection) to assess intensity are approximate only and not reproducible. Here, we present a method to accurately quantify the percentage of bivalve gonad filled with digenean trematode tissue, based on small squashes of gonad tissue rapidly photographed under light microscopy. A maximum of 15 photographs is required to determine the percentage of the whole gonad occupied by trematodes with a minimum of 90% confidence, with smaller mussels requiring fewer. In addition, the stage of trematode infection can be assessed because full sporocysts, spent sporocysts and free cercariae are clearly distinguishable. Although variation exists in the distribution of trematodes in gonad tissue, and thus in the estimate of percentage of the gonad filled with trematodes, this method represents a marked improvement on current coarse assessments of infection which typically focus on binary presence/absence measures. This technique can be used to facilitate a more sophisticated understanding of host-parasite interactions in bivalves, and can inform the conservation and reproductive biology of environmentally crucial species.

Biochemical and apoptotic changes in the nervous and ovotestis tissues of Biomphalaria alexandrina following infection with Schistosoma mansoni.

Infection with trematodes produces physiological and behavioural changes in intermediate snail hosts. One response to infection is parasitic castration, in which energy required for reproduction of the host is thought to be redirected to promote development and multiplication of the parasite. This study investigated some reproductive and biochemical parameters in the nervous (CNS) and ovotestis (OT) tissues of Biomphalaria alexandrina during the course of Schistosoma mansoni infection. Antioxidant and oxidative stress parameters including catalase (CAT), nitric oxide (NO) and lipid peroxidation (MDA) were measured. Levels of steroid hormones, including testosterone, progesterone and estradiol, were also assessed. Finally, flow cytometry was used to compare measures of apoptosis between control snails and those shedding cercariae by examining mitochondrial membrane potential with the stain 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimi-dazolylcarbocyanine iodide (JC-1) and poly(ADP-ribose) polymerase (PARP). Infection with S. mansoni caused a 47.7% reduction in the net reproductive rate (Ro) of B. alexandrina. CAT activity was increased in the CNS at 21 days post infection (dpi) but by 28 dpi it was reduced below control values. Also, CAT activity increased significantly in the OT at 14, 21 and 28 dpi. In CNS tissues, NO levels were reduced at 7 dpi, increased at 14 and 21 dpi, and reduced again at 28 dpi. The overall level of lipid peroxidation gradually increased during the course of infection to reach its highest levels at 28 dpi. Steroid hormone measurements showed that concentrations of testosterone and estradiol were reduced in the CNS tissues at 28 dpi, while those of progesterone were slightly increased in the CNS and OT tissues. The percentage of cells that positively stained with JC-1was significantly increased in CNS and OT tissues of infected snails while the percentage of cells positively stained with PARP was decreased compared to controls. Together, these findings indicate that infection initiates diverse biochemical and hormonal changes leading to loss of cells responsible for egg laying and reproduction in B. alexandrina.

Krill Nyctiphanes simplex gonad affection associated with acute-intensity phyllobothriid plerocercoid infection.

This is the first acute-intensity record of helminths parasitizing the subtropical krill Nyctiphanes simplex Hansen, 1911. We briefly describe the pathology of infection of Phyllobothriidae gen. sp. plerocercoids parasitizing N. simplex in the Gulf of California. Infection occurred with a very low prevalence (P = 0.06%, n = 1563 specimens), although acute-intensity exceeded several hundred plerocercoids crowding the hemocoel in one female host. Nyctiphanes simplex showed inflammatory response of hemocyte-based infiltration, nodule formation, and presumptive melanization. Remarkably, cestodes invade and supplant the gonad, causing atretic oocytes and severe tissue destruction in the gonad likely leading to castration and cell death in connective tissue of the infected organs suggesting that acute-intensity infection exceeds the krill's reaction capacity. Thus, Phyllobothriidae gen. sp. negatively affects the host by depleting its fitness, leading to total castration to prevent/block host reproduction.

First record of the nematode Echinocephalus pseudouncinatus (Gnathostomatidae, Spirurida) in an edible, commercial host, the pen shell Atrina maura (Bivalvia: Pinnidae).

We describe a nematode infestation of the Atrina maura, the most valuable pen shell fished in Mexico, for the first time. Observations by Mexican authorities indicated that parasites were found encysted in pen shell gonads. The aims of this study included: (i) to identify the parasite morphologically; (ii) to quantify the infestation in different tissues of the pen shell; and (iii) to establish the seasonal variation in gonadal development. During 2015, 10 to 40 pen shells were randomly collected each month from the same commercial bed, and gonads were preserved and processed histologically to establish the seasonal and monthly frequency of infested gonads. A subsample of 35 pen shells was used to identify the parasite and to characterize the infestation of the muscle, mantle, gonad, and digestive gland tissue components. All tissues were dissected, and parasites were collected, photographed, quantified, and adequately preserved for species identification using scanning electron microscopy. Prevalence, intensity of infestation, abundance and crowding data were analyzed by Quantitative Parasitology software and compared monthly and seasonally using a chi test and analysis of means. Results indicated that all parasites were juvenile (second stage) nematodes, Echinocephalus pseudouncinatus. Parasites were found only in muscle and gonad tissues in both male and female pen shells. Hyperpigmentation was observed in the muscle and atretic oocytes with phagocytosis in the gonads. The frequency of infested gonads was significantly higher during winter but was not related to shell size or sex (p > 0.05). A greater number of pen shells were observed to be infested during December and August and during pen shell spawning and development stages. The highest frequency of infested gonads (40%) occurred in December when the lowest temperature and chlorophyll a concentration were recorded. The effects of the biotic and abiotic parameters on this host-pathogen relationship need further research. This nematode species is related to species that are causal agents of gnathostomiasis, which may constitute a health hazard for raw muscle consumers and could affect the reproductive activity of pen shell.

First description of the male and subgravid female of Philometra serranellicabrillae Janiszewska, 1949 (Nematoda: Philometridae), a gonad-infecting parasite of the comber Serranus cabrilla (Linnaeus) (Serranidae) off Tunisia.

The male and subgravid female of Philometra serranellicabrillae Janiszewska, 1949 (Philometridae) collected from the gonads of Serranus cabrilla (Linnaeus) (Serranidae) off Tunisia are described for the first time based on light and scanning electron microscopical studies. The male of this nematode can be separated from other congeneric gonad-infecting nominal species in the structure and shape of the gubernaculum (e.g. absence of a dorsal protuberance and a median smooth field). The shape of the male posterior region is unique in that it bears a pair of big circular papillae posterior to the cloacal opening, which is also present in other Philometra spp. from serranids, i.e. P. indica Moravec & Manoharan, 2014, P. inexpectata Moravec, Chaabane, Justine & Neifar, 2016 and P. jordanoi (López-Neyra, 1951) Yamaguti, 1961. Moreover, P. serranellicabrillae differs from its congeners in other fish families from the Mediterranean Sea, in the length of spicules and gubernaculum.

Light and Scanning Electron Microscopic Studies of Unionicola tetrafurcatus (Acari: Unionicolidae) Infecting Four Freshwater Bivalve Species and Histopathological Effect On Its Hosts.

Water mites of the genus Unionicola are the most common symbionts of freshwater bivalves. During the current investigation, a total of 120 live freshwater mussels representing 5 species, Corbicula fluminea (Veneroida), Coelatura aegyptiaca (Unionoidea), Mutela rostrata, and Chambardia rubens (Mutelidae), were collected from 2 localities in Tura (Helwan Governorate) and El Kanater (Qaluobiya Governorate), Egypt. Only 3 of the 4 bivalve species listed are considered freshwater bivalves (members of Unionoidea). Corbicula fluminea belong to the family Cyrenidae within Veneroida. Collected mussels were dissected and examined for the presence of unionicolid mites. It was found that 30.83% (37/120) were infected with a single mite species, Unionicola tetrafurcatus (Unionicolidae). The highest prevalence was observed during the summer with 83.33% (25/30) whereas the least was observed in autumn, i.e., 33.33% (10/30). Mites were recovered from the gills, gonads, and visceral mass of mussel hosts. Gills of host mussels were the primary site of oviposition for Unionicola mites. Smaller bivalves in size had significantly greater numbers of mites than did larger ones in size. Numbers of mites per host species was variable and the highest prevalence level of 83.33% (25/30) was recorded in Cor. fluminea while the lowest one of 16.66% (5/30) was found in Ch. rubens. Morphological and morphometric characterizations of mites revealed some differences between the present species and other related Unionicola. Histopathological responses of host mussels to the eggs, larvae, and cuticular remnants of U. tetrafurcatus were also studied. Therefore, the present study demonstrated that freshwater bivalves have a new host and locality records for infection with U. tetrafurcatus. Future studies are recommended to include advanced molecular characteristics for these mites.

Two new gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) from Trachinus spp. (Osteichthyes: Trachinidae) in the Gulf of Hammamet, Tunisia.

Based on light and scanning electron microscopical studies, two new gonad-infecting species of Philometra Costa, 1845, P. draco n. sp. and P. radiata n. sp. (Nematoda: Philometridae), are described from the marine perciform fishes Trachinus draco (Linnaeus) and T. radiatus (Linnaeus) (both Trachinidae), respectively, in the Gulf of Hammamet, off the northeastern coast of Tunisia. Philometra draco n. sp. and P. radiata n. sp. can be separated from other gonad-infecting species of this genus by the structures associated to the gubernaculum (e.g. dorsal protuberance, smooth field separating the dorsolateral longitudinal parts), as well as by the length of the body, spicules and gubernaculum. Philometra radiata n. sp. can be distinguished from P. draco n. sp. in having the dorsal side of the gubernaculum distal end provided with a median longitudinal smooth field demarcated by two dorsolateral lamellate parts. These two new species are the first philometrid species described from fishes of the family Trachinidae.

A new species of Proctoeces and reinstatement of Proctoeces humboldti George-Nascimento and Quiroga 1983 (Digenea: Fellodistomidae) based on molecular and morphological evidence.

The most studied digenean of marine organisms in Chile is by far Proctoeces humboldti, a parasite of the intestine of the clingfish Sicyases sanguineus and gonad of the keyhole limpet Fissurella spp. (progenetic metacercariae). The mussel Perumytilus purpuratus has been suggested as the first intermediate host for this digenean. In a study examining the parasites of S. sanguineus from central Chile, we found specimens of Proctoeces showing significant morphological differences with P. humboldti. To assist in the resolution of the taxonomic identification of these specimens, as well sporocysts obtained from the mussel P. purpuratus from central and northern Chile, phylogenetic studies using DNA sequences from the SSU rRNA, as well the LSU rRNA and Cox 1 gene were performed. Results showed that the clingfish S. sanguineus is a host for two species of Proctoeces (P. humboldti and P. syciases n. sp.) along the northern and central Chilean coast, without geographic separation; the mussel P. purpuratus is the first intermediate host for P. syciases n. sp. but not for P. humboldti in central and northern Chile. Fissurellids (Archaeogastropoda) along the Chilean coast harbor only progenetic stages of P. humboldti, but there is no evidence of progenesis for P. syciases. The reinstatement of Proctoeces humboldti is strongly suggested.

Redescription of Philometra margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995 (Nematoda: Philometridae), a gonad-infecting parasite of the red grouper Epinephelus morio (Serranidae) in the Gulf of Mexico.

The insufficiently known nematode species Philometra margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995 (Philometridae) is redescribed based on light and scanning electron microscopical (SEM) examinations of specimens collected from the gonad of the type host, the red grouper Epinephelus morio (Valenciennes) (Serranidae, Perciformes), in the northern Gulf of Mexico off Florida, USA. Also, new prevalence data for females of P. margolisi were derived from 188 fish, and a subset of these (n = 38) were used to determine prevalence and intensity of male nematodes. The male of this species was studied with SEM for the first time, which revealed some new, taxonomically important morphological features. The male posterior end had a V-shaped caudal mound, four pairs of minute adanal papillae, a pair of large papillae located posterior to the cloacal aperture and a pair of very small phasmids. The distal end of the gubernaculum is unique among all gonad-infecting species of Philometra parasitizing serranids in that its ventral surface is flat, smooth, without the usual two longitudinal grooves; the dorsal lamellate structures on the gubernaculum are also different in this species. In contrast to data in the original species description, the body length of gravid females of P. margolisi was 132-280 mm. Overall prevalence for male nematodes (76.3%) was much higher than for females (15.4%), and female nematode prevalence was higher in samples collected during host spawing season than out of season (27.1% and 3.3%, respectively).

Descriptions of Philometra aenei n. sp. and P. tunisiensis n. sp. (Nematoda: Philometridae) from Epinephelus spp. off Tunisia confirm a high degree of host specificity of gonad-infecting species of Philometra Costa, 1845 in groupers (Serranidae).

Based on light and electron microscopical studies of males and mature females, two new gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) are described from the ovary of groupers, Epinephelus spp. (Perciformes; Serranidae), in the Mediterranean Sea off Tunisia (near Sfax): Philometra aenei n. sp. from the white grouper E. aeneus (Geoffroy Saint-Hilaire) and P. tunisiensis n. sp. from the goldblotch grouper E. costae (Steindachner). Identification of both fish hosts was confirmed by barcoding of the infected fish specimens. Philometra aenei is mainly characterised by the length of conspicuously distended spicules (108-123 µm), the presence of a distinct dorsal barb at the middle region of the gubernaculum and a distinct protuberance consisting of two dorsolateral lamellar parts separated from each other by a smooth median field at its distal tip, a V-shaped mound on the male caudal extremity and by the body length of the males (2.34-3.05 mm). The male of this species was found to possess minute deirids in the cervical region, which is quite exceptional within the Philometridae. Philometra tunisiensis is distinguished from other gonad-infecting congeneric species parasitising serranids by the length of the needle-like spicules and gubernaculum (201-219 and 78-87 µm, respectively), spicule length representing 9-11% of body length, the gubernaculum/spicules length ratio of 1:2.52-2.77, the length of oesophagus in the male comprising 15-16% of the body length, the absence of a dorsal protuberance on the distal lamellar part of the gubernaculum and a pair of large papillae posterior to the cloaca, a dorsally interrupted mound on the male caudal extremity and the body length of the male (2.01-2.42 mm). The presence of three morphologically very different species of Philometra in congeneric hosts in the Mediterranean Sea confirms a high degree of host specificity of these gonad-infecting nematodes parasitising groupers.

Trypanosoma brucei gambiense Infections in Mice Lead to Tropism to the Reproductive Organs, and Horizontal and Vertical Transmission.

Trypanosoma brucei gambiense, transmitted by the tsetse fly, is the main causative agent of Human African trypanosomosis in West Africa and poses a significant health risk to 70 million people. Disease progression varies depending on host immunity, but usually begins with a haemo-lymphatic phase, followed by parasite invasion of the central nervous system. In the current study, the tropism of T. b. gambiense 1135, causing a low level chronic 'silent' infection, was monitored in a murine model using bioluminescence imaging and PCR. A tropism to the reproductive organs, in addition to the central nervous system, after 12-18 months of infection was observed. Bioluminescent analysis of healthy females crossed with infected males showed that 50%, 62.5% and 37.5% of the female mice were subsequently positive for parasites in their ovaries, uteri and brain respectively. Although PCR confirmed the presence of parasites in the uterus of one of these mice, the blood of all mice was negative by PCR and LAMP. Subsequently, bioluminescent imaging of the offspring of infected female mice crossed with healthy males indicated parasites were present in the reproductive organs of both male (80%) and female (60%) offspring. These findings imply that transmission of T. b. gambiense 1135 occurs horizontally, most probably via sexual contact, and vertically in a murine model, which raises the possibility of a similar transmission in humans. This has wide reaching implications. Firstly, the observations made in this study are likely to be valid for wild animals acting as a reservoir for T. b. gambiense. Also, the reproductive organs may act as a refuge for parasites during drug treatment in a similar manner to the central nervous system. This could leave patients at risk of a relapse, ultimately allowing them to act as a reservoir for subsequent transmission by tsetse and possibly, horizontally and vertically.

Sexual transmission of Trypanosoma cruzi in murine model.

Trypanosoma cruzi is mainly transmitted by blood-sucking triatomines, but other routes also have epidemiological importance, such as blood transfusion and congenital transmission. Although the possibility of sexual transmission of T. cruzi has been suggested since its discovery, few studies have been published on this subject. We investigated acquisition of T. cruzi by sexual intercourse in an experimental murine model. Male and female mice in the chronic phase of Chagas disease were mated with naive partners. Parasitological, serological and molecular tests demonstrated the parasites in tissues and blood of partners. These results confirm the sexual transmission of T. cruzi in mice.

Is an Apicomplexan Parasite Responsible for the Collapse of the Iceland Scallop (Chlamys islandica) Stock?

Due to the total and unexpected collapse of the Iceland scallop, Chlamys islandica, stocks around Iceland during the 2000s, a commercial fishing ban has been imposed on this valuable resource since 2003. Following the initial identification of an apicomplexan parasite in the scallops, a long-term surveillance program was established to evaluate the effect of the parasite on the population. The infections were highly prevalent in all shell sizes throughout the study. However, the parasite only impacts mature scallops where they cause severe macroscopic changes, characterized by an extensively diminished and abnormally coloured adductor muscle. A highly significant relationship was observed between infection intensity and gonad and adductor muscle indices. The first four years of the study, were characterized by high infection intensity and very poor condition of the adductor muscle and gonads, whilst during subsequent years, infections gradually decreased and the condition of the scallops improved. Histopathological changes were restricted to the presence of apicomplexan zoites which were widely distributed, causing varying degrees of pathology in all organs. In heavy infections, muscular and connective tissues were totally necrotized, destroying significant parts of numerous organs, especially the adductor muscle, digestive gland and gonads. The progression of the disease was in good synchrony with the mortality rates and the subsequent decline observed in the scallop stock and recruitment indices. Our findings strongly suggest that the apicomplexan parasite played a major role in the collapse of the Iceland scallop stock in Breidafjordur. In addition to causing mortality, the infections significantly impact gonad development which contributes further to the collapse of the stock in the form of lower larval recruitment. Furthermore, compelling evidence exists that this apicomplexan pathogen is causing serious disease outbreaks in other scallop populations. Similar abnormal adductor muscles and the parasite itself have been identified or observed in association with other mass mortality events in several different scallop species and commercial stocks in the northern hemisphere.

First molecular identification of Ascocotyle (Phagicola) longa in its first intermediate host the mud snail Heleobia australis.

This is the first study that used species-specific DNA primers to confirm the presence of the heterophyid Ascocotyle (Phagicola) longa Ransom, 1920 in its first intermediate host. The larval stages (rediae and cercariae) of this parasite were morphologically and genetically identified in the gonad of the intertidal mud snail Heleobia australis (d'Orbigny, 1835) (Cochliopidae) in the Bahía Blanca estuary, Argentina. In addition, we asked whether the prevalence in H. australis varied between seasons. Mullets - the second intermediate host of this heterophyid - migrate in estuaries during the warmer seasons and it is expected that piscivorous birds and mammals - the definitive hosts - prey more intensively on this species at those times. Thus, the number of parasite eggs released into the tidal flat within their feces should be higher, thereby increasing the ingestion of the parasite by H. australis.We therefore expected a higher prevalence of A. (P.) longa in H. australis in the Bahía Blanca estuary during spring and summer than autumn and winter. We found that 16 out of 2,744 specimens of H. australis had been infected with A. (P.) longa (total prevalence of 0.58%). Nonetheless, the prevalence showed no significant variation between seasons. Hence, we discuss an alternative scenario where the lack of seasonal changes might be mostly related to the permanent residence of definitive hosts in the estuary and not to the seasonal recruitment of mullets. Finally, we highlight the need for more experimental and comparative approaches in order to understand the diagnosis and geographical distribution of this worldwide heterophyid.

Redescription of Philometra globiceps (Rudolphi, 1819) (Nematoda: Philometridae), the type species of Philometra Costa, 1845, including the first data obtained by SEM.

A redescription of Philometra globiceps (Rudolphi 1819), the type species of Philometra Costa 1845 (Philometridae), is provided on the basis of specimens collected from the gonads, stomach, pyloric caeca, intestine and gallbladder of the marine fish Uranoscopus scaber Linnaeus (Uranoscopidae, Perciformes) caught in the Ionian Sea off Ugento, southern Italy. Light microscopical and scanning electron microscopical examinations (latter used for the first time in this species) of the specimens revealed some previously unreported morphological features, such as the location of submedian pairs of cephalic papillae of external circle on four elevated cuticular lobes in gravid females, the presence of amphids, genital papillae and phasmids in males, the lamellate structure of the distal end of gubernaculum appearing as a dorsal protuberance in lateral view and the structure of the male caudal end. A taxonomically important feature of P. globiceps is the details in the dorsal transverse lamella-like structures on the distal end of the gubernaculum, by which this species can be separated from other gonad-infecting species of this genus. Apparently, P. globiceps is a specific parasite of U. scaber and all previous records of this species from hosts belonging to other fish families are evidently based on misidentifications.

A new gonad-infecting species of Philometra, P. barnesi sp. n. (Nematoda: Philometridae), from the marine fish Pomadasys argenteus (Haemulidae) off the northern coast of Australia.

A new nematode species, Philometra barnesi sp. n. (Philometridae), is described from the ovary of the marine teleost Pomadasys argenteus (Fosskål) (Haemulidae) off the northern coast of Australia (near Darwin). The new species is characterized by short subequal spicules (84 and 87 µm long), a gubernaculum without a dorsal protuberance at its distal tip, the structure of male anterior and posterior body ends, the body lengths of males (1.67 mm) and gravid females (320-597 mm) and the structure of the oesophagus and caudal end of gravid females. Philometra barnesi is the sixth nominal gonad-infecting species of this genus recorded from marine fishes in Australian waters and the third species of philometrids described from fishes of the family Haemulidae.

Host specificity of a parasitic fluke: is Posthodiplostomum minimum a centrarchid-infecting generalist or specialist?

Parasite host specificity has important implications for species diversity estimates, food web dynamics, and host shifts. "White grub" is the metacercaria stage of a fluke ( Posthodiplostomum minimum ) that occurs in many fish species, but no attempt has been made to quantify variation in host use by this worm. Here we used 2 approaches to evaluate host specificity within the strain that infects centrarchids ( P. minimum centrarchi). First, we measured parasite loads in 2 centrarchid hosts, bluegill ( Lepomis macrochirus ) and white crappie ( Pomoxis annularis ), from Spring Lake in McDonough County, Illinois. We found that infection levels differed significantly between these hosts. Prevalence in bluegill was 100% and the median intensity was 940 metacercariae, but only 57% of white crappie were infected (median intensity = 4). Site specificity of white grub also differed significantly between the 2 hosts. In bluegills, kidneys were most heavily infected, whereas in white crappies, livers harbored the most worms. We also performed a literature survey of P. minimum prevalence estimates from 14 centrarchid species from other localities. We calculated the mean white grub prevalence for each host species and used this to calculate STD*, a quantitative index of host specificity. STD* was 1.33, significantly closer to the value for a specialist (STD* = 1.00) than a generalist (STD* = 2.00). This reflects the fact that P. minimum prevalence is higher in Lepomis species than it is in centrarchids outside this genus. These data show that P. minimum centrarchi specializes on Lepomis species, but the causes of this specialization are unknown. This worm may be a single species that differs in host use due to ecological or physiological host differences, or it may be a complex of species that vary in host use for similar reasons. Genetic data are required to evaluate these possibilities.

Two new gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) from marine fishes off the northern coast of Australia.

Based on light and electron microscopical studies, two new gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) are described from the ovary of marine perciform fishes off the northern coast of Australia (near Darwin): Philometra carangis n. sp. from the bluespotted trevally Caranx bucculentus Alleyne & Macleay (Carangidae) and P. carponotati n. sp. from the Spanish flag snapper Lutjanus carponotatus (Richardson) (Lutjanidae). Philometra carangis is mainly characterised by the length of the spicules (153-189 µm), the presence of a distinct dorsal protuberance consisting of two dorsolateral lamellar parts separated from each other by a smooth median field, a V-shaped mound on the male caudal extremity, a pair of large post-cloacal papillae and the body length of the males (3.22-4.15 mm). Philometra carponotati is distinguished from other congeneric species parasitising lutjanids by the length of the spicules and gubernaculum (225-252 and 99-117 µm, respectively), the absence of a dorsal protuberance on the distal lamellar part of the gubernaculum, the presence of a U-shaped mound on the male caudal extremity, a pair of large post-cloacal papillae and the body length of the male (3.74-4.31 mm). Besides the recently established Philometra zabidii Moravec & Diggles, 2014 (based on a single female), these two newly described nematodes are the only nominal gonad-infecting species of Philometra known to parasitise marine fishes in Australian waters.