Herein we describe a new species of turtle blood fluke (TBF) and propose a new genus to accommodate it, Pitiutrema revelae n. gen., n. sp. This blood fluke infects the heart of six-tubercled Amazon River turtles (Podocnemis sextuberculata [Cornalia, 1849] [Pleurodira: Podocnemididae]) in the headwaters of the Amazon River near Iquitos, Peru. It resembles the other 2 described species of South American freshwater TBFs (Atamatam amazoniensis Bullard and Roberts, 2019, and Paratamatam iquitosiensis Bullard and Roberts, 2019) by having a dorsoventrally flattened and ovoid body, an oral sucker with anteroventral spines, 2 inter-cecal testes arranged in a column, inter-gonadal terminal genitalia, an inter-cecal and post-ovarian Laurer's canal pore, and a Y-shaped excretory bladder. It differs from all other nominal TBFs by having the combination of an aspinose body that lacks mammillae, a tapered (not broadly rounded) posterior body end, a ventral sucker, slightly M-shaped or inverse U-shaped ceca, a deeply-lobed (dendritic) ovary, a transverse uterus, and a dispersed vitellarium. The new genus is further unique among TBF genera by having an anterior to posterior sequence of ventral sucker, anterior testis, ovary, cirrus sac (lateral to posterior half of ovary), and posterior testis. The phylogenetic results and placement of the new taxon (1) were both predicted by our morphological diagnosis and comparisons with related taxa, (2) further indicated monophyly of the nominal South American freshwater TBFs, (3) reaffirmed the marine derived lineage identity of the nominal South American freshwater TBFs, and (4) highlighted that the single cercarial sequence (TBF sp. W-810) from an ampullariid in Brazil does not share a recent common ancestor with any of the nominal South American freshwater TBFs. The new species is the eighth TBF reported from a side-necked turtle (Pleurodira), the first TBF from a member of Podocnemididae, and the third freshwater TBF from South America.

There are multiple Henneguya spp. (Myxozoa: Myxobolidae) endemic to North American catfish aquaculture that affect the gills of channel catfish and their hybrids. These parasites are morphologically similar, and confusion exists regarding the predilection sites and pathologic changes associated with different species. In the spring of 2018, channel (Ictalurus punctatus) female × blue (Ictalurus furcatus) male hybrid catfish from 2 separate commercial operations in northwest Mississippi were submitted for diagnostic assessment in response to observed morbidity and reduced feeding activity. Fish presented with unusually heavy infections of Henneguya spp. plasmodia in the gills. The majority of gill filaments contained widespread, pinpoint, raised, white nodules corresponding microscopically to myxospore-filled plasmodia that obliterated interlamellar spaces. The bipolar myxospores were consistent with Henneguya spp. described from North American ictalurids, possessing slender fusiform spore bodies and elongate bifurcate caudal processes. Associated microscopic lesions included lamellar fusion, epithelial hyperplasia, infrequent, localized, granulomatous branchitis, and rare cartilage lysis, suggesting impaired gill function. Mature plasmodia were excised by laser capture microdissection from ethanol-fixed, hematoxylin and eosin–stained histologic sections for molecular analysis. Fragments (700 bp) of a highly variable region of the 18S rRNA gene, diagnostic for the Myxobolidae, were 100% similar at the nucleotide level to Henneguya exilis. Although mortality was negligible, fish in the affected ponds exhibited signs of respiratory distress similar to proliferative gill disease (PGD) caused by Henneguya ictaluri in channel and hybrid catfish. However, gross and microscopic lesions differed markedly from PGD, known colloquially as “hamburger gill disease.” While H. exilis has been reported from channel catfish, it is not typically associated with morbidity and mortality and has not previously been reported from channel × blue catfish hybrids. This work characterizes lesions and confirms the etiology of gill disease induced by the myxozoan H. exilis. In addition to PGD and other non-parasitic conditions, massive interlamellar H. exilis infection should be a differential consideration in pond-raised channel and hybrid catfish experiencing signs of respiratory distress.

Barn swallows (Hirundo rustica) are the most widespread swallow species in the world. However, little is known about the coccidian parasites of H. rustica. Feces from a single H. rustica nesting in McCurtain County, Oklahoma, were collected in May 2018 and examined for coccidia; the swallow was found to be passing a new species of Eimeria. Oocysts of Eimeria hochatownensis n. sp. are ellipsoidal with a smooth bi-layered wall, measure (L × W) 25.5 × 15.2 µm, and have a length/width (L/W) ratio of 1.7; a micropyle and oocyst residuum are absent, but polar granule(s) are present. Sporocysts are ellipsoidal and measure 12.8 × 6.5 µm, L/W 2.0; a nipple-like Stieda body is present, but sub-Stieda bodies and para-Stieda bodies are absent. The sporocyst residuum is composed of a compact spheroid with a dense, irregular mass of finer granules lying between and dispersed among the sporozoites. This is the first eimerian reported from H. rustica and the family Hirundinidae, and only the fourth Eimeria spp. known from passerine birds of the New World.

Snappers from the southern Gulf of Mexico (SGM) and Mexican Caribbean (CAR) were examined for parasitic nematodes to determine their richness, composition, and infection parameters (prevalence and mean intensity). From February 2016 to March 2018, 431 individuals of 8 snapper species were collected in 6 localities. In all, these fishes were parasitized by 2,275 individual nematodes belonging to 13 taxa: Terranova sp. was found in 7 of 8 host species and showed the highest prevalence (23%), while the rest had lower values (<10%). Lutjanus griseus (Linnaeus) harbored the highest species richness (10 species), followed by Lutjanus apodus (Walbaum) (8 species). Most localities were similar in terms of species richness but differed in the specific composition. Eight nematode taxa represent new host records for the family Lutjanidae (Gill), thus increasing to 22 the nematode taxa in the SGM and CAR. There is a potential risk to public health due to the presence of nematodes with zoonotic potential (as Anisakis sp.) and the habit in the region of eating raw fish (cebiche).

Uvulifer Yamaguti, 1934, is a genus of diplostomoidean digeneans that parasitizes kingfishers worldwide. Species have a Neascus-type metacercaria that encysts in or on fish intermediate hosts, often causing black spot disease. Only 3 prior studies published DNA sequence data for Uvulifer species with only 1 including a single named species (Uvulifer spinatus López-Jiménez, Pérez-Ponce de León, & García-Varela, 2018). Herein we describe 2 new species of Uvulifer from the green-and-rufous kingfisher, Chloroceryle inda (Linnaeus), collected in Peru (Uvulifer batesi n. sp. and Uvulifer pequenae n. sp.). Both new species are readily differentiated from their New World congeners by a combination of morphological characters including distribution of vitelline follicles and prosoma:opisthosoma length ratios. In addition, we used newly generated nuclear 28S rRNA and mitochondrial COI gene sequence data to differentiate among species and examine phylogenetic affinities of Uvulifer. This includes the 2 new species and Uvulifer ambloplitis (Hughes, 1927), as well as Uvulifer elongatusDubois, 1988, Uvulifer prosocotyle (Lutz, 1928), and Uvulifer weberiDubois, 1985, none of which have been part of prior molecular phylogenetic studies. Our data on Uvulifer revealed 0.1–2.2% interspecific divergence in 28S sequences and 9.3–15.3% in COI sequences. Our 28S phylogeny revealed at least 6 well-supported clades within the genus. In contrast, the branch topology in the COI phylogenetic tree was overall less supported, indicating that although COI sequences are a great tool for species differentiation, they should be used with caution for phylogenetic inference at higher taxonomic levels. Our 28S phylogeny did not reveal any clear patterns of host association between Uvulifer and particular species of kingfishers; however, it identified 2 well-supported clades uniting Uvulifer species from distant geographical locations and more than 1 biogeographic realm, indicating at least 2 independent dispersal events in the evolutionary history of the New World Uvulifer. Our results clearly demonstrate that the diversity of Uvulifer in the New World has been underestimated.

During 2017–2018, a survey for the rat lungworm, Angiostrongylus cantonensis (Nematoda: Metastrongyloidea), in rodents from Piedmont and Lower Coastal Plains physiographic regions of Georgia was conducted. On 4 occasions, a single worm was recovered from the pulmonary vessels of a single cotton rat (Sigmodon hispidis). One of these worms was identified as a Physaloptera sp. and the remaining 3 as a Mastophorus sp. by morphology. No A. cantonensis were found. Physaloptera (Nematoda: Physalopteroidea) and Mastophorus species (Nematoda: Spiruroidea) are stomach parasites of many wild and domestic animals. This is the first report of these species in the pulmonary vessels of a definitive host. To better characterize these parasites, representative specimens were collected from cotton rat stomachs and identified morphologically and molecularly. Based on partial cytochrome c oxidase subunit 1 (COI) gene sequences, Physaloptera hispida from stomachs were identical to the Physaloptera sp. from the pulmonary vessels. The COI sequences from the Mastophorus sp. from the stomach exhibited a higher degree of variability but confirmed that the pulmonary worms were the same Mastophorus species. Furthermore, sequences of Mastophorus from a coastal site clustered separately from a clade of Mastophorus sequences from cotton rats from a Piedmont site. Our data show that adult worms recovered from pulmonary vessels of cotton rats could be either Physaloptera or Mastophorus sp., indicating that these parasitic worms are not always restricted to the stomach and that worms from pulmonary vessels must be carefully examined to obtain a definitive diagnosis of A. cantonensis infection.

In an ongoing investigation on the helminths of amphibians in southeastern Mexico, specimens of 2 undescribed species of Haematoloechus were collected from Rana brownorum. Haematoloechus ceciliae n. sp. is morphologically most similar to Haematoloechus meridionalis, but differs in the shape of the oral sucker, in the nature of the acetabulum, and in the distribution of the glandular cells in the pharyngeal region; Haematoloechus celestunensis n. sp. closely resembles Haematoloechus floedae, but differs in the form and size of the testes and measurements of acetabulum. COI and 28S DNA sequences of both new species show high divergence compared to other species of the genus. In the phylogenetic trees, H. ceciliae appears most closely related to Haematoloechus danbrooksi and H. celestunensis to Haematoloechus veracruzanus.

The prevalence of anti–Toxoplasma gondii antibodies was investigated among 104 ratites: 68 rheas (Rhea americana), 16 emus (Dromaius novaehollandiae), and 20 ostriches (Struthio camelus) in 4 Brazilian states. The prevalence in rheas was 26.5% (18 of 68), and titers were 1:100 (n = 8), 1:200 (n = 1), 1:400 (n = 4), 1:800 (n = 4), and 1:1,600 (n = 1). In emus, the prevalence was 50% (8 of 16), and titers were 1:50 (n = 1) and 1:100 (n = 7). The ostriches were slaughtered for human consumption, and 80% (16 of 20) were seropositive with titers of 1:200 (n = 1), 1:400 (n = 9), and 1:800 (n = 6). Sera were tested with a modified agglutination test, and the results confirmed the distribution of the parasite in ratite species from Brazil. The data obtained in this study show that T. gondii is prevalent among ratites from Brazil, and therefore ratite meat should also be considered a potential source of human infection. This is the first report of T. gondii seroprevalence in emus.

Toxoplasma gondii is a zoonotic parasite of worldwide distribution. The consumption of infected pork meat has been suggested to be an important source for human infection in the tropical area of Yucatan, Mexico. We performed a cross-sectional study of 12 farms across the state to investigate the seroprevalence of Toxoplasma gondii infection in domestic pigs. In total, 632 samples were obtained from 2 different environmental zones (tropical deciduous low forest and tropical sub-deciduous medium forest) and 2 abattoirs. The modified agglutination test (MAT) was used to assess the seroprevalence of T. gondii in pigs and to evaluate 2 globally used serological tests, the Dye test (DT) and ID Screen^® ELISA multi-species, and a commercial ELISA kit (Human Toxo IgG, Human-diagnostics), which is widely used locally in this geographical area. The overall prevalence obtained with the MAT (cut-off ≥1:25) among the 632 pigs was 1.4% (95% CI, 0.6–2.7%). The seroprevalence obtained for the different age groups was 0.6%, 0.7%, 1.8%, and 6.8% among 2–3, 3–4, 4–5, and ≥5-mo-old pigs. This increase in the seroprevalence was statistically significant for the 2 older groups (odds ratio [OR] 3.9–7.1, P < 0.05) in comparison with younger groups. DT at >4 IU dilution had a perfect agreement and 100% of sensitivity and specificity when compared with the MAT. Although ID Screen^® had only a fair agreement (κ = 0.389) with the MAT, the McNemar test showed that the results of these tests were comparable (P = 0.29). The Human Toxo ELISA showed no agreement with MAT, ID Screen^®, and DT (κ = 0.000–0.023, McNemar P < 0.05). This ELISA was lacking in specificity, accuracy, and precision; hence, we do not recommend its use for T. gondii diagnosis in pig serum.

Coccidiosis is a common disease of livestock, including water buffaloes. Reports discussing the prevalence and identity of coccidian parasites in water buffaloes from Egypt are few, and nothing is known concerning the most pathogenic species, Eimeria bareillyi. Fresh feces collected from 175 water buffaloes in Dakahlia Governorate, Egypt, were processed using the standard flotation technique. Eimerian oocysts were found in 49 (28%) samples, and 10 species were identified. Eimeria bareillyi oocysts were found in 10 samples (5.7%), and this was the single species in 3 diarrheic calves. Typical oocysts of Eimeria auburnensis with smooth oocyst walls were observed in 4 (2.3%) samples. Closely similar oocysts were found in a single sample (0.6%) together with those of E. auburnensis. These oocysts had a rough granulated or mammillated wall and are referred to as E. auburnensis–like oocysts. A molecular study is needed to clarify whether E. auburnensis and E. auburnensis–like oocysts are from different species. Other identified Eimeria species were: Eimeria alabamensis (0.6%), Eimeria bovis (10.8%), Eimeria canadensis (1.1%), Eimeria cylindrica (4%), Eimeria ellipsoidalis (2.3%), Eimeria subspherica (2.8%), and Eimeria zuernii (9.7%). This is the first report of E. bareillyi oocysts in water buffaloes from Egypt.

Pathoecology studies the environmental and cultural factors that contribute to the maintenance of infections or diseases in populations. Concerning parasites, it requires the evaluation of these factors based on the presence and life cycle of these organisms. For this reason, it is possible to apply this concept in the context of ancient populations in order to understand the parasite–host dynamic or even the health consequences faced by the members of the populations. This study aimed to apply the pathoecology concept in Pedra do Tubarão and Cemitério do Caboclo archaeological sites. Six coprolite samples were analyzed and 1 was positive for Spirometra sp. eggs. Spirometra is a cestode that has copepods as the first intermediate host; amphibians, reptiles, birds, and mammals as the second intermediate hosts; and felines and canines as definitive hosts. Humans can be infected by ingesting the first or second intermediate hosts and can develop sparganosis, which can cause health consequences depending on the location of the spargana. The presence of this parasite, of a water fount near the site, where the first intermediate host can live, and the findings of the bones of some of the second intermediate hosts in these sites, suggesting dietary purposes, indicate that this infection was probably present in this population.

The flow regime of a river is an important driver of many ecosystem components. However, few studies explore how differences in flow rates and water chemistry can influence communities of parasites and their hosts. Here, we investigate the impact of dissolved oxygen, pH, salinity, water temperature, and river flow on the abundance and prevalence of cymothoid isopod parasitism (Lironeca ovalis) of the Bay Anchovy (Anchoa mitchilli) in the Alafia and Hillsborough rivers of Tampa Bay (Florida). We also explore seasonality by comparing monthly samples preserved throughout 2005–2007. Although both the Alafia and Hillsborough rivers had similar average water temperatures and salinity, and similar wet and dry season cycles, the upstream damming of the Hillsborough River had numerous negative effects on water flow rate, dissolved oxygen content, and acidity. This disruption in water quality corresponded with a lower abundance of anchovy hosts, fewer free-swimming cymothoids, and low prevalence of anchovy parasitism. Anchovies were much more abundant in the Alafia River, but flow negatively affected abundance—a negative effect that could be mitigated by positive changes in water temperature, salinity, and pH. Flow rates also negatively affected free-swimming cymothoid abundance; however, water flow was less important in predicting their parasitism of anchovies. In Alafia, fewer anchovies were parasitized when dissolved oxygen was high and water acidity was low, but more were parasitized during the wet season. These findings corroborate predictions that flow can moderate habitat stability and complexity which, in turn, can impact opportunities for parasitism of host communities.

Truttaedacnitis truttae is a cucullanid nematode of primarily salmonine fishes. Brown trout (Salmo trutta) in Europe reportedly become parasitized by ingesting lampreys (Lampetra planeri) carrying infective larvae. However, our field and laboratory observations suggested that North American specimens of T. truttae have an alternative life cycle. High abundances and potential impact of T. truttae in rainbow trout, Oncorhynchus mykiss, in the Colorado River drainage in Grand Canyon, where there are no lampreys, prompted a study on the transmission dynamics of this nematode. Eggs of T. truttae, collected from live gravid females, were incubated in the laboratory. Snails, Physa gyrina and Lymnaea sp., were exposed to T. truttae larvae 3–4 wk later. Active larvae of T. truttae were observed penetrating the intestinal wall of exposed snails, and worm larvae were found in the visceral tissues when examined 1 wk after exposure. Larvae in snails showed little growth and development 2 wk later and corresponded to L3 larvae. Infected snails were fed to hatchery-reared juvenile rainbow trout. Developing stages were subsequently found in the mucosal lining and lumen of trout intestines. Adult male and female (gravid) worms were found in the ceca of trout examined 5–6 mo after consuming infected snails. Larvae found in pepsin/trypsin digests and mucosal scrapings from wild, naturally infected, trout corroborate laboratory findings. Screening of Physa sp. and gammarids collected from Colorado River, Grand Canyon, for natural infections with T. truttae using the ITS1 rDNA marker gave positive results. Truttaedacnitis truttae is the second species, after Truttaedacnitis clitellarius of lake sturgeon, capable of using a snail first intermediate/paratenic host and is similar to several other cucullanids in having a histotropic phase of development in the definitive fish host.

The nematode genus Bidigiticauda has 2 species (Bidigiticauda vivipara and Bidigiticauda embryophilum), which are parasites of bats from the Neotropical region. The present paper describes a new species of Bidigiticauda from a male Artibeus planirostris specimen collected in the Pratigi Environmental Protection Area in Bahia state, Brazil. The new species, Bidigiticauda serrafreirei n. sp., differs from B. embryophilum by having longer spicules, rays 5 and 6 arising from a common trunk and bifurcating in its first third, rays 3 and 4 emerging slightly separated from each other, and dorsal rays reaching the margin of the caudal bursa. The new species also differs from B. vivipara by the dorsal ray bifurcating at the extremity of the trunk. A molecular phylogenetic analysis was conducted to determine the evolutionary affinities of Bidigiticauda serrafreirei n. sp. within the Strongylida, which identified a clade that grouped Bidigiticauda with the other members of the Anoplostrongylinae. However, the molineid subfamilies did not group together, indicating that the family Molineidae is polyphyletic. Further analyses, which include additional taxa and genetic markers, should elucidate the complex relationships within the Molineidae, in particular its subfamilies and the evolution of the traits that define these groups.

Organisms with a parasitic lifestyle comprise a high proportion of biodiversity in aquatic and terrestrial environments. However, there is considerable variation in the ways in which they acquire nutrients. Hematophagy is a common consumption strategy utilized by some terrestrial, aquatic, and marine organisms whereby the parasite removes and digests blood from a host. Gnathiid isopods are marine hematophagous parasites that live in benthic substrates from the intertidal to the abyss. Although ecologically similar to ticks and mosquitoes, they feed only during each of 3 juvenile stages and adults do not feed. They have long been considered as generalist fish parasites and to date, there have been no reports of their successfully feeding on invertebrates. Based on observations of gnathiids attached to soft-bodied invertebrates collected from light traps, we conducted a laboratory experiment in which we collected and individually housed various common Caribbean invertebrates and placed them in containers with gnathiids to see if the gnathiids would feed on them. All fed gnathiids were subsequently removed from containers and given the opportunity to metamorphose to the next developmental stage. In total, 10 out of the 260 gnathiids that were presented with 1 of 4 species of potential invertebrate hosts had fed by the next morning. Specifically, 9 of a possible 120 gnathiids fed on lettuce sea slugs (Elysia crispata), and 1 of a possible 20 fed on a bearded fireworm (Hermodice carunculata). Eight of these 10 fed gnathiids metamorphosed to the next stage (5 to adult male, 2 to adult female, and 1 to third-stage juvenile). Even though feeding rates on invertebrates were considerably lower than observed for laboratory studies on fishes, this study provides the first documented case of gnathiids' feeding on and metamorphosing from invertebrate meals. These findings suggest that when fish hosts are not readily available, gnathiids could switch to soft-bodied invertebrates. They further provide insights into the evolution of feeding on fluids from live hosts in members of this family.

In the present paper, species of the Proteocephalus-aggregate de Chambrier, Zehnder, Vaucher, and Mariaux, 2004 (Cestoda: Proteocephalidae) reported from centrarchid and percid fishes in North America are reviewed, and their taxonomic status is critically assessed based on a study of type specimens and new material from Canada and the United States. The following 3 species, supposedly strictly specific to their fish definitive hosts, are recognized as valid: (1) Proteocephalus fluviatilisBangham, 1925 (new synonyms Proteocephalus osburniBangham, 1925 and Proteocephalus microcephalusHaderlie, 1953; Proteocephalus ‘robustus’ nomen nudum) from the smallmouth and largemouth bass, Micropterus dolomieu (Lacépède) (type host) and Micropterus salmoides (Lacépède) (both Centrarchidae); (2) Proteocephalus luciopercaeWardle, 1932 (new synonym Proteocephalus stizostethiHunter and Bangham, 1933) from the walleye, Sander vitreus (Mitchill) (type host), and sauger, Sander canadensis (Griffith et Smith) (Percidae); and (3) Proteocephalus pearseiLa Rue, 1919, a parasite of the yellow perch, Perca flavescens Mitchill (Percidae). All species are illustrated based on new, properly heat-fixed material. Scanning electron micrographs of the scoleces of percid tapeworms P. luciopercae and P. pearsei, as well as the bass tapeworms P. fluviatilis and Proteocephalus ambloplitis (Leidy, 1887), the latter of which does not belong to this Proteocephalusaggregate, are provided for the first time together with a simple key to species identification of proteocephalids from centrarchiform and perciform teleost fishes.

Members of the genus Sarcocystis are frequently found infecting members of the family Cervidae. Although Sarcocystis species are generally host specific for their intermediate hosts, species in cervids appear to be less host specific. Here, we report fallow deer (Dama dama) as a new host for Sarcocystis morae, originally described from the red deer (Cervus elaphus). Tongues of 69 legally hunted animals in Spain were tested for sarcocysts, and the species were characterized by light microscopy, ultrastructurally and molecularly. Sarcocysts were identified in 66.7% of D. dama. Sarcocysts had thin (<2 µm thick) cyst wall with hair-like villar protrusions bifurcated at their tips resembling type 8a. Genetic sequences obtained for 18S rRNA and COI reached 99.6–100% and 97.9–98.7% similarity, respectively, to those of S. morae from the red deer. The present study provides new data concerning lower level of host specificity within Sarcocystis genus for cervids.

The coccidian species Eimeria is a parasitic protozoan that causes the gastrointestinal disease coccidiosis in numerous vertebrate species. Incidence of the disease in commercial chickens produces drastic economic losses. Traditionally, detection of Eimeria has been performed using classical methods such as observation of oocyst morphology. However, molecular methods to detect and speciate Eimeria are becoming more prevalent. The 18S ribosomal gene, in particular, has been a widely used DNA amplification target for detection of Eimeria. Although the full-length gene is typically used for this purpose, newer research targeting shorter regions of the gene is being performed. This study investigated the suitability of a 120–base pair (bp) DNA bar code within the 18S gene for species differentiation. When comparing sequence variation from the Eimeria species infecting chickens, shortening the 18S gene to the 120-bp highly variable region provided increased species differentiation, while also reducing intraspecies variation. This DNA bar code is useful for distinction of the Eimeria species infecting chickens and should be considered for future molecular detection assays and metagenomic sequencing.

Codonocephalus is a monotypic genus of diplostomid digeneans and is the only genus in the subfamily Codonocephalinae. The type-species Codonocephalus urniger has an unusual progenetic metacercaria that uses frogs as intermediate hosts and can use snakes as paratenic hosts. Adult C. urniger parasitize ardeid wading birds in the Palearctic. Despite the broad distribution of Codonocephalus, no DNA sequence data are currently available for the genus. In this study, we generated sequence data for nuclear ribosomal and mitochondrial DNA from progenetic metacercaria of the type-species C. urniger from marsh frog, Pelophylax ridibundus, collected in Ukraine. We used partial sequences of the nuclear ribosomal 28S gene to examine for the first time the phylogenetic position of Codonocephalus among the Diplostomoidea.