Occurrence of new Philometra sp. in mangrove red snapper Lutjanus argentimaculatus from the Karachi coast, Pakistan

A recent examination of Philometra nematodes from mangrove red snapper Lutjanus argentimaculatus (Forsskal, 1775) from the Karachi coast, Kemari was done in the years 2021-2022. The present study reported three new species of genus Philometra (Costa, 1845) (Nematoda: Philometridae) Philometra kolachii, Philometra lutjani and Philometra kemarii. A total of 140 fish samples were examined, and 76 were infected. The intensity of infected fish was 54.28%. In Pakistan, literature on Philometrid nematodes is limited, therefore, this research would be helpful for the documentation and enhancement of nematods in Pakistan.

Review of the parasitic nematodes of marine fishes from off the American continent

The ichthyofauna of the Atlantic and Pacific coasts off the American continent is very rich. Consequently, a high biodiversity of nematodes parasitizing these vertebrates is also expected. Currently, data on nematode parasites of marine fish off the Americas are fragmented. A review of all adult nematode species reported parasitizing marine fish from off the American continent is herein presented, as well as comments on their patterns of diversity, life cycles and advances in the taxonomic and phylogenetic knowledge. A total of 209 valid species, 19 species inquirendae and 6 dubious records have been recorded, the majority from the fish taxa Eupercaria and Perciformes. The families Sciaenidae, Serranidae and Lutjanidae, as well as the tropical and temperate Atlantic waters, exhibited the highest records of parasitic nematodes. The Cucullanidae, Philometridae and Cystidicolidae were the most speciose families of nematodes, which may be related to technological advances and relatively recent efforts of taxonomists, resulting in description of new taxa and the resolution of taxonomic problems. Numerous taxonomic questions still need resolution and, even though genetic data have been important for this process, the database is very scarce. This is the first review on all currently known nematode species parasitizing marine fish off the Americas and may serve as an important basis of reference for future approaches on these organisms.

Phylum Nematoda: trends in species descriptions, the documentation of diversity, systematics, and the species concept

This paper summarizes the trends in nematode species description and systematics emerging from a comparison of the latest comprehensive classification and census of Phylum Nematoda (Hodda 2022a, b) with earlier classifications (listed in Hodda 2007).   It also offers some general observations on trends in nematode systematics emerging from the review of the voluminous literature used to produce the classification.   The trends in nematodes can be compared with developments in the systematics of other organisms to shed light on many of the general issues confronting systematists now and into the future.  

Records of two gonad-infecting species of Philometra (Nematoda: Philometridae) from marine fishes off Iraq, including the description of Philometra parabrevicollis n. sp. from the bigeye snapper Lutjanus lutjanus Bloch (Pisces, Lutjanidae)

Recent examinations of some marine fishes from off the southern coast of Iraq revealed the presence of two species of Philometra Costa, 1845 (Nematoda: Philometridae): P. parabrevicollis n. sp. (males and subgravid and nongravid females) from the ovary of the bigeye snapper Lutjanus lutjanus Bloch (Perciformes, Lutjanidae) and Philometra sp. (subgravid females) from the ovary of the bartail flathead Platycephalus indicus (Linnaeus) (Perciformes, Platycephalidae). Specimens of species are described and illustrated based on light and scanning electron microscopical examinations. Philometra parabrevicollis n. sp. is mainly characterised by the length of spicules (267-285 µm) and gubernaculum (159-168 µm), the gubernaculum/spicule length ratio (1:1.64-1.76), the structure of the gubernaculum distal tip and of the male caudal end, and the body length of males (4.03-4.90 mm). The description of this new species again confirms a high degree of host specificity of gonad-infecting species of Philometra in congeneric lutjanid hosts. Although Philometra sp. parasitising P. indicus in Iraqi waters was previously recorded, its subgravid females are described for the first time. A key to gonad-infecting species of Philometra parasitic in fishes of the family Lutjanidae is provided.

Two species of philometrid nematodes (Philometridae) newly recorded from marine fishes off South Australia, including Philometra inconveniens n. sp. from Hyporhamphus melanochir (Valenciennes) (Hemiramphidae)

Recent examinations of some marine fishes from off the coast of South Australia revealed the presence of two species of Philometra Costa, 1845 (Nematoda: Philometridae): P. inconveniens n. sp. from the ovary (males) and body cavity (subgravid female) of the southern garfish Hyporhamphus melanochir (Valenciennes) (Beloniformes, Hemiramphidae) and Philometra sp. (gravid and subgravid females) from the body cavity of the Australian barracuda Sphyraena novaehollandiae Günther (Perciformes, Sphyraenidae) (new host and geographical records). Specimens of species are described and illustrated based on light and scanning electron microscopical examinations. Philometra inconveniens n. sp. differs from the most similar species P. longa Moravec, Barton & Shamsi, 2021, a parasite of the body cavity of the congeneric host off eastern Australia, mainly by a different structure of the gubernaculum (absence of dorsal barbs and presence of lateral extensions on its distal portion). This indicates a high degree of host specificity of these nematodes in co-occuring congeneric hosts.

Morphological and genetic description of two new species of philometrid nematodes (Philometridae) parasitic in needlefishes (Belonidae) from estuaries of Florida, USA

Two new species of philometrid nematodes (Philometridae) from needlefishes (Belonidae) in Florida are described based on morphological and genetic characteristics: Philometra aequispiculata sp. n. (males and females) collected from the ovary of Strongylura marina (Walbaum) (type host) and Strongylura notata (Poey), and Philometra notatae sp. n. (females) from the swimbladder of S. notata. Both species are described and illustrated based on light and scanning electron microscopical examinations. Morphologically, P. aequispiculata sp. n. differs from all congeners mainly in the unique structure of the distal tip of the gubernaculum, whereas P. notatae sp. n. is mainly characterised by the presence of eight markedly large cephalic papillae of the outer circle in gravid and subgravid females, the body length of the gravid female (54 mm) and by the absence of caudal projections. Molecular characterisation of the new species was assessed from phylogenetic analysis of mitochondrial cytochrome c oxidase I (COI) and SSU rRNA small-subunit ribosomal RNA (SSU) sequences among closely related philometrids by way of Bayesian inference. Phylogenetic reconstructions based on COI and SSU sequences show each of the new species comprise discrete ancestor-descendent lineages.

Hepatobiliary PAHs and prevalence of pathological changes in Red Snapper

Red Snapper (Lutjanus campechanus) were collected throughout the Gulf of Mexico (GoM) from 2011 to 2017 and analyzed for biliary (n = 496) fluorescent aromatic compounds (FACs), hepatic (n = 297) polycyclic aromatic hydrocarbons (PAHs) and microscopic hepatobiliary changes (MHC, n = 152). Gross and histological evaluations were conducted with liver tissues to identify and characterize pathological changes. This is the first report to interrelate hepatobiliary PAH concentrations and MHCs in Red Snapper. Hepatic PAHs measured in GoM Red Snapper ranged from 192 to 8530 ng g^-1 w.w. and biliary FACs ranged from 480 to 1,100,000 ng FAC g^-1 bile. Biliary FACs in Red Snapper collected along the west Florida Shelf and north central region declined after 2011 and were relatively stable until a sharp increase was noted in 2017. Increases in the PAH exposures are likely due to a number of sources including leaking infrastructure, annual spills, riverine input and the resuspension of contaminated sediments. In contrast, hepatic PAH concentrations were relatively stable indicating Red Snapper are able to maintain metabolic clearance however this energetic cost may be manifesting as microscopic hepatic changes (MHCs). Virtually all (99 %) of the evaluated Red Snapper had one to nine MHCs with an average of five coinciding changes in an individual fish. The observed changes were broadly classified as inflammatory responses, metabolic responses, degenerative lesions, nonneoplastic proliferation and neoplastic lesions. Biliary FACs were associated with parasitic infection and intracellular breakdown product accumulation such as intra-macrophage hemosiderin, lipofuscin and ceroid laden prevalence. Whereas, hepatic PAHs were associated with increased myxozoan plasmodia prevalence. This study evaluates relationships between hepatobiliary PAH concentrations and biometrics, somatic indices, condition factors and microscopic hepatic changes in Red Snapper located in the north central GoM. Together, these results may be signaling increased disease progression in Gulf of Mexico Red Snapper more than likely resulting from chronic environmental stressors including elevated PAH exposures and concentrations.

New records of Philometra spp. (Nematoda: Philometridae) from marine perciform fishes off Florida, USA, including descriptions of two new species

Recent examinations of marine perciform fishes from off the Florida coast in the Gulf of Mexico and Straits of Florida, USA, revealed the presence of the following six species of Philometra Costa, 1845 (Nematoda: Philometridae): P. haemulontis sp. n. (males and females) from the ovary of Haemulon plumierii (Lacepède) (type host) and H. aurolineatum Cuvier (both Haemulidae); Philometra synagridis Moravec, Bakenhaster et Fajer-Ávila, 2014 (males and females) from the ovary and testes of Lutjanus synagris (Linnaeus) (Lutjanidae); P. margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995 (male) from the ovary of Hyporthodus nigritus (Holbrook) (Serranidae) (new host record; probably a paradefinitive host); P. andersoni sp. n. (male) from the ovary of H. nigritus; Philometra sp. 1 (male) from the ovary of Rhomboplites aurorubens (Cuvier) (Lutjanidae); and Philometra sp. 2 (females) from the subcutaneous tissue of the anterior-most head sinuses of Hyporthodus niveatus (Valenciennes) (Serranidae). Specimens of species are described and illustrated based on light and (except for Philometra sp. 1) scanning electron microscopical examinations. Philometra haemulontis sp. n. differs from all congeners in the unique structure of the gubernaculum, whereas P. andersoni sp. n. can be differentiated from other gonad-infecting congeners parasitising the Serranidae by a combination of morphological features. Females of P. synagridis are described for the first time. Gravid females of Philometra sp. 2 are similar to those of P. morii Moravec, Bakenhaster et Fajer-Ávila, 2010, a subcutaneous parasite of Epinephelus morio (Valenciennes) (Serranidae) in the Gulf of Mexico.

New records of philometrids (Nematoda: Philometridae) from marine fishes off Japan, including description of Philometra kidakoi sp. n. and Congerinema japonicum gen. et sp. n

Occasional examinations of some marine fishes in Japan revealed, in addition to other parasites, the following eight species of philometrid nematodes (Philometridae) (all females only): Philometra kidakoi sp. n. from the ovary of Gymnothorax kidako (Temminck et Schlegel) (Muraenidae); Philometra pinnicola (Yamaguti, 1935) from the operculum of Epinephelus akaara (Temminck et Schlegel) (Serranidae); Philometra sebastisci Yamaguti, 1941 from the ovary of Sebastes cheni Barsukov (Scorpaenidae) (new host); Philometra madai Quiazon, Yoshinaga et Ogawa, 2008 from the ovary of Acanthopagrus schlegelii (Bleeker) (Sparidae) (new host); Philometra isaki Quiazon, Yoshinaga et Ogawa, 2008 from the ovary of Parapristipoma trilineatum (Thunberg) (Haemulidae); Philometra sp. from the ovary of Synanceia verrucosa Bloch et Schneider (Synanceiidae); Congerinema japonicum gen. et sp. n. from the subcutaneous tissue of Conger myriaster (Brevoort) (Congridae); and Clavinema mariae (Layman, 1930) from the operculum of Acentrogobius pflaumii (Bleeker) (Gobiidae). Specimens of all species are described based on light and scanning electron microscopical examinations. Philometra kidakoi sp. n. is the first gonad-infecting philometrid from the Muraenidae. The new monotypic genus Congerinema gen. n. is characterised by the unique net-like cuticular ornamentation on the female body. Clavinema mariae is considered to be a complex of several cryptic species and a need of the discovery of conspecific males is stressed (this also concerns other philometrid species with unknown males). At present, the fauna of philometrid nematodes parasitising marine fishes in Japanese waters is represented by 22 nominal species belonging to four genera.

Description of Two New Species of Philometra Costa, 1845 (Nematoda: Philometridae) from Marine Fishes off Japan, with Notes on Philometroides seriolae (Yamaguti, 1935)

PURPOSE

Philometrid nematodes (Philometridae) represent a group of more than 200 species parasitic in the body cavity and various body tissues of fishes. Due to morphological and biological peculiarities, the majority of them are known only by their large females. Generally, the fauna of these parasites remains little known.

METHODS

Occasional helminthological examinations of three species of marine fishes in Japan revealed two new and one insufficiently known species of these tissue-dwelling parasites. These were studied with the use of light and scanning electron microscopy.

RESULTS

All three nematode species are described. Philometra ostorhinchi sp. nov. (males and females) from the ovary of Ostorhinchus semilineatus (Temminck et Schlegel) (Apogonidae, Perciformes) is characterized mainly by the lengths and structure of spicules and the gubernaculum (spicules 108-120 µm long, length of the gubernaculum 78-87 µm); it is the only species of philometrids parasitic in a fish belonging to the Apogonidae. The gravid females of Philometra tenuis sp. nov. (only females available) from the head subcutaneous tissues of Conger myriaster (Brevoort) (Congridae, Anguilliformes) differ from congeners mainly in an unusual shape of the anterior oesophageal bulb. Some new data on the morphology of an insufficiently known species Philometroides seriolae (Ishii, 1931), collected from the body musculature of Seriola quinqueradiata Temminck et Schlegel (Carangidae, Perciformes), are provided; the number and arrangement of cephalic papillae in subgravid females of P. seriolae were found to be similar to those in females of the majority of other philometrid species.

CONCLUSIONS

The present study extends the knowledge of the species composition of philometrids parasitizing marine fishes and of the morphology of P. seriolae, the type species of Philometroides Yamaguti, 1935.

Species of Philometra (Nematoda, Philometridae) from fishes off the Mediterranean coast of Africa, with a description of Philometra rara n. sp. from Hyporthodus haifensis and a molecular analysis of Philometra saltatrix from Pomatomus saltatrix

Two gonad-infecting species of Philometra Costa, 1845 (Nematoda, Philometridae) were recorded for the first time from marine perciform fishes off Tunisia and Libya: Philometra rara n. sp. from the rare, deep-water Haifa grouper Hyporthodus haifensis (Serranidae) off Libya and Philometra saltatrix Ramachandran, 1973 from the bluefish Pomatomus saltatrix (Pomatomidae) off Tunisia. Identification of both fish species was confirmed by molecular barcoding. Light and scanning electron microscope studies of Ph. rara n. sp. showed that it is characterized by the length of spicules (216–219 μm) and the gubernaculum (90–93 μm), the gubernaculum/spicules length ratio (1:2.32–2.43), and mainly by the shape and structure of the distal end of the gubernaculum (shovel-shaped with a wide median smooth field in dorsal view), appearing as having a dorsal protuberance in lateral view, and by the structure of the male caudal mound (dorsally interrupted); large subgravid females (70–137 mm long) are characterized by the presence of four oval submedian cephalic elevations, each of them bearing a pair of cephalic papillae of the outer circle. The finding of Ph. saltatrix off Tunisia confirms that this species is widespread throughout the Mediterranean region. A molecular analysis of our Ph. saltatrix specimens and other available philometrid cytochrome c oxidase 1 (COI) sequences showed that most species have robust clades. Sequences of Ph. saltatrix from Tunisia diverge from Ph. saltatrix from Brazil and the USA, suggesting that speciation is currently occurring between populations from both sides of the Atlantic Ocean.

Philometra dissimilis n. sp. from the ovary of Johnius belangerii (Sciaenidae) and other new records of philometrids (Nematoda: Philometridae) from fishes of the Bay of Bengal, India

Based on light and scanning electron microscopical studies, a new gonad-infecting species of Philometra Costa, 1845, P. dissimilis n. sp. (Nematoda: Philometridae), is described from the marine fish (Belanger’s croaker) Johnius belangerii (Cuvier) (Sciaenidae, Perciformes) in the Bay of Bengal, off the eastern coast of India. The species is mainly characterized by the body length of male 2.73 – 3.37 mm and that of gravid female 145 – 171 mm, needle-like, equal spicules 96 – 120 μm long, length of the gubernaculum 75 – 90 μm, distal end of the gubernaculum with lamellar structures forming a simple dorsal protuberance and by the V-shaped male caudal mound. Philometra dissimilis is the seventh known gonad-infecting species of this genus parasitizing sciaenid fishes. Moreover, an additional two species of Philometra (only females) were recorded from fishes in the Bay of Bengal: P. lobotidisMoravec, Walter et Yuniar, 2012 from the abdominal cavity of Lobotis surinamensis (Bloch) (Lobotidae, Perciformes), which is a new geographical record, and Philometra sp. from the ovary of Platycephalus indicus (Linnaeus) (Platycephalidae, Scorpaeniformes), representing probably an undescribed species.

Two gonad-infecting species of Philometra (Nematoda: Philometridae) from groupers (Serranidae) off Tunisia, with a key to Philometra species infecting serranid gonads

Based on light and scanning electron microscopical studies of nematode specimens (males and mature females) collected from the ovary of groupers (Serranidae, Perciformes) in the Mediterranean Sea off Tunisia (near Tunis and Sfax), two gonad-infecting species of Philometra Costa, 1845 (Nematoda, Philometridae) are reported: Philometra inexpectata n. sp. from the mottled grouper Mycteroperca rubra and P. jordanoi (López-Neyra, 1951) from the dusky grouper Epinephelus marginatus. Identification of both fish species was confirmed by molecular barcoding. The new species is mainly characterized by the length of equally long spicules (147–165 μm), the gubernaculum (63–93 μm long) bearing at the tip two dorsolateral lamellar parts separated from each other by a smooth median field, a V-shaped mound on the male caudal extremity, the presence of a pair of large caudal papillae located posterior to the cloaca and by the body length of the males (1.97–2.43 mm). Philometra inexpectata n. sp. is the fifth known gonad-infecting philometrid species parasitizing serranid fishes in the Mediterranean region. The males of P. jordanoi were examined by scanning electron microscopy for the first time; this detailed study revealed some new taxonomically important morphological features, such as the number and arrangement of cephalic and caudal papillae, presence of amphids and phasmids and mainly the lamellate structures at the posterior end of the gubernaculum. A key to gonad-infecting species of Philometra parasitic in serranid fishes is provided.

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

Two different gonad-infecting species of Philometra Costa, 1845 were collected from the ovary of marine perciform fishes, the blackspotted croaker Protonibea diacanthus (Sciaenidae) and the John’s snapper Lutjanus johnii (Lutjanidae), from off the northern coast of Australia. Nematodes (males and females) from P. diacanthus represent a new taxon, Philometra protonibeae n. sp., which is mainly characterized by the body length of the males (3.37–3. 90 mm), broad, equally long spicules (length 126–141 μm) and the shape and structure of the gubernaculum with a dorsally lamellate distal tip. The nematodes (only females) from L. johnii may represent an undescribed species, but, because of the absence of conspecific males, they could not be specifically identified. Philometra protonibeae is the fifth nominal gonad-infecting species of this genus recorded from marine fishes in Australian waters and the seventh species of these parasites described from fishes of the family Sciaenidae.