Daniel C. Huston

Trematodes of fishes of the Indo-west Pacific: told and untold richness

The Indo-west Pacific is a marine bioregion stretching from the east coast of Africa to Hawaii, French Polynesia and Easter Island. An assessment of the literature from the region found reports of 2,582 trematode species infecting 1,485 fish species. Reports are concentrated in larger fishes, undoubtedly reflecting the tendency for larger hosts to be infected by more species of parasites as well as a collecting bias. Many hundreds of fish species, including many from families known to be rich in trematodes, have yet to be reported as hosts. Despite some areas (the Great Barrier Reef, Hawaii and the waters off China, India and Japan) receiving sustained attention, none can be considered to be comprehensively known. Several regions, most importantly in East Africa, French Polynesia and the Coral Triangle, are especially poorly known. The fauna of the Indo-west Pacific has been reported so unevenly that we consider it impossible to predict the true trematode richness for the region. We conclude that the greatest gap in our understanding is of the geographical distribution of species in the Indo-west Pacific. This is highlighted by the fact that 87% of trematodes in the region have been reported no more than five times. The reliable recognition of species is a major problem in this field; molecular approaches offer prospects for resolution of species identification but have been little adopted to date.

Molecular phylogeny of the Haplosplanchnata Olson, Cribb, Tkach, Bray and Littlewood, 2003, with a description of Schikhobalotrema huffmani n. sp.

We describe Schikhobalotrema huffmani n. sp. from Tylosurus crocodilus (Péron and Leseur) (Belonidae) collected off Lizard Island, Great Barrier Reef, Queensland, Australia and Tylosurus gavialoides (Castelnau) collected from Moreton Bay, Queensland. Schikhobalotrema huffmani n. sp., along with Schikhobalotrema ablennis (Abdul-Salam and Khalil, 1987) Madhavi, 2005, Schikhobalotrema acutum (Linton, 1910) Skrjabin and Guschanskaja, 1955 and Schikhobalotrema adacutum (Manter, 1937) Skrjabin and Guschanskaja, 1955 are distinguished from all other species of Schikhobalotrema Skrjabin and Guschanskaja, 1955 in having ventral suckers which bear lateral lobes and have longitudinal apertures. Schikhobalotrema huffmani n. sp. differs from S. ablennis in having an obvious post-vitelline region and a longer forebody. From S. acutum, S. huffmani n. sp. differs in having a prostatic bulb smaller than the pharynx and more anterior testis. From S. adacutum, S. huffmani n. sp. differs in having more prominent ventral sucker lobes, a conspicuous prostatic bulb and a longer forebody. We also report the first Australian record of Haplosplanchnus pachysomus (Eysenhardt, 1829) Looss, 1902, from Mugil cephalus Linnaeus (Mugilidae) collected in Moreton Bay. Molecular sequence data (ITS2, 18S and 28S rDNA) were generated for Schikhobalotrema huffmani n. sp., H. pachysomus and archived specimens of Hymenocotta mulli Manter, 1961. The new 18S and 28S molecular data were combined with published data of five other haplosplanchnid taxa to expand the phylogeny for the Haplosplanchnata. Bayesian inference and Maximum Likelihood analyses recovered identical tree topology and demonstrated the Haplosplanchnata as a well-supported monophyletic group. However, relationships at and below the subfamily level remain poorly resolved.

The phylogenetic position of Choerodonicola Cribb, 2005 (Digenea: Opecoelidae) with a partial life-cycle for a new species from the blue-barred parrotfish Scarus ghobban Forsskål (Scaridae) in Moreton Bay, Australia

Choerodonicola Cribb, 2005 is a minor genus of opecoelid trematodes defined for species with exceptionally small eggs but otherwise generalised morphology. Four species are currently recognised, all from fishes collected in Japanese waters but each from different perciform families: a labrid, a scarid, a sparid and pinguipeds. We report on a new species, Choerodonicola arothokoros n. sp., from the blue-barred parrotfish Scarus ghobban Forsskål (Scaridae) collected in subtropical waters of Moreton Bay, south-east Queensland, Australia. Using genetic sequence data for the ITS2 rDNA marker, we matched adult C. arothokoros to intramollsucan stages discovered in an intertidal gastropod Herpetopoma atratum (Gmelin) (Vetigastropoda: Chilodontidae) collected in close proximity to the fish hosts. Notably, the cercariae lack a penetration stylet and are among the smallest known in the Opecoelidae. We provide the first assessment of the phylogenetic position of Choerodonicola based on sequence data generated for the phylogenetically informative 18S and 28S rRNA coding regions, for C. arothokoros and also C. renko Machida, 2014, which we recollected from the yellowback seabream Dentex hypselosomus Bleeker from the fish market in Minabe, Wakayama Prefecture, Japan. In our analyses, species of Choerodonicola resolved to neither of the major marine Plagioporinae (sensu lato) clades, clustering instead with Trilobovarium parvvatis Martin, Cutmore & Cribb, 2017, Podocotyloides parupenei (Manter, 1963) Pritchard, 1966 and Macvicaria magellanica Laskowski, Jeżewski & Zdzitowiecki, 2013. This clade is phylogenetically distinctive such that it has the potential to be recognised as a new opecoelid subfamily, but further investigation is required to establish the bounds for such a grouping and to determine the morphological and/or life-history patterns reflected by the phylogeny. Finally, we propose C. interruptus (Manter 1954) n. comb. for a species previously recognised in Plagioporus Stafford, 1904 and known only from Pseudolabrus miles (Schneider & Forster), a labrid endemic to New Zealand.

Molecular systematics of the digenean community parasitising the cerithiid gastropod Clypeomorus batillariaeformis Habe & Kusage on the Great Barrier Reef

A rich fauna of digenetic trematodes has been documented from the Great Barrier Reef (GBR), yet little is known of the complex life-cycles of these parasites which occur in this diverse marine ecosystem. At Heron Island, a small coral cay at the southern end of the GBR, the intertidal marine gastropod Clypeomorus batillariaeformis Habe & Kusage (Cerithiidae) is especially abundant. This gastropod serves as an intermediate host for 12 trematode species utilising both fish and avian definitive hosts. However, 11 of these species have been characterised solely with morphological data. Between 2015 and 2018 we collected 4870C. batillariaeformis from Heron Island to recollect these species with the goal of using molecular data to resolve their phylogenetic placement. We found eight of the 12 previously known species and two new forms, bringing the total number of digenean species known to parasitise C. batillariaeformis to 14. The families of this trematode community now include the Atractotrematidae Yamaguti, 1939, Bivesiculidae Yamaguti, 1934, Cyathocotylidae Mühling, 1898, Hemiuridae Looss, 1899, Heterophyidae Leiper, 1909, Himasthlidae Odhner, 1910, Microphallidae Ward, 1901, and Renicolidae Dollfus, 1939. Molecular data (ITS and 28S rDNA) were generated for all trematode species, and the phylogenetic position of each species was determined. The digenean community parasitising C. batillariaeformis includes several common species, as well as multiple species which are uncommon to rare. Although most of those trematodes in the community which exploit fishes as definitive hosts have remained common, the composition of those which utilise birds appears to have shifted over time.

Trigonocephalotrema (Digenea : Haplosplanchnidae), a new genus for trematodes parasitising fishes of two Indo-West Pacific acanthurid genera

Abstract. The Great Barrier Reef is the largest coral reef ecosystem on the planet and supports a diverse community of marine fishes, as well as the organisms that parasitise them. Although the digenetic trematodes that parasitise fishes of the Great Barrier Reef have been studied for over a century, the species richness and diversity of many trematode lineages is yet to be explored. Trigonocephalotrema, gen. nov. is proposed to accommodate three new species, Trigonocephalotrema euclidi, sp. nov., T. hipparchi, sp. nov. and T. sohcahtoa, sp. nov., parasitic in fishes of Naso Lacepède and Zebrasoma Swainson (Acanthuridae) in the tropical Pacific. Species of Trigonocephalotrema are characterised with morphological and molecular data (18S rRNA, ITS2 and 28S rRNA). Species of Trigonocephalotrema are morphologically distinguished from all other haplosplanchnid lineages by having terminal, triangular, plate-like oral suckers. With the inclusion of the new molecular data, Bayesian inference and maximum likelihood analyses of the Haplosplanchnidae Poche, 1926 recovered identical tree topologies and demonstrated Trigonocephalotrema as a well-supported monophyletic group. Although species of Trigonocephalotrema are differentiated from all other haplosplanchnid lineages on the basis of morphology, species within the genus are morphologically cryptic; thus, accurate species identification will require inclusion of host and molecular data. Species of Trigonocephalotrema cannot be assigned to a recognised subfamily within the Haplosplanchnidae using either morphological or molecular data and would require the erection of a new subfamily to accommodate them. However, we find little value in the use of subfamilies within the Haplosplanchnidae, given that there are so few taxa in the family, and herein propose that their use be avoided.

Defoliation of Cultured Creeping Primrose Willow (Ludwigia repens) and Other Aquatic Plants by Parapoynx obscuralis (Lepidoptera: Crambidae)

The aquatic lepidopterans of the genus Parapoynx require aquatic plants to complete the life cycle (Welsh 1922). Adults are terrestrial but lay eggs on plants on or in the water, and the larvae and pupae are aquatic (Welsh 1922, Berg 1950). The larvae feed on submerged plant parts and respire through gills or spiracles (Welsh 1922). Mueller and Dearing (1994) suggested that Parapoynx rugosalis Möschler, 1890 larvae select newly emergent rather than older leaves to construct cases, but Fries and Power (1999) found P. obscuralis Grote, 1881 preferred older leaves. In Florida, Parapoynx spp. feeds on 25 plant species in 17 families (Habeck 1974). Habeck (1974) listed eelgrass (Vallisneria spp.) as the preferred food of P. obscuralis in Florida, but also noted the moth feeding on yellow cow-lily [Nuphar luteue (L.) Sm.], broadleaf arrowhead (Sagittaria latifolia Willd.), and pondweed (Potamogeton spp.). The moths have been used as biological control agents for selected non-native aquatic plants (Spencer and Lekic 1974, Buckingham and Bennett 2001) and have been spread globally by the aquarium industry (Agassiz 1978). In the San Marcos River, Texas (29° 53’ 14.4” N, 97° 56’ 06.7”W), P. obscuralis was documented feeding but with limited impact on Indian swampweed [Hygrophila polysperma (Roxb.) T. Anderson] (Harms and Grodowitz 2010), waterstargrass [Heteranthera dubia (Jacq.) MacMill.] (Harms et al. 2011), and Texas wild rice (Zizania texana Hitchc.) (Fries and Power 1999). Ward and Newman (2006) reported that sunfish (Lepomis spp.) can suppress herbivores such as Parapoynx spp. At the U.S. Fish and Wildlife Service San Marcos Aquatic Resources Center (SMARC) in Central Texas (29° 50’ 22.39” N, 97° 58’ 31.99” W), multiple aquatic plants, including federally endangered Z. texana, are propagated in tanks of various sizes (115 to 3,000 liters) in a greenhouse, outdoor raceways (14,500 liters), and ponds (241,030 liters) for restoration in the San Marcos River. In 1996, Parapoynx obscuralis was documented defoliating Z. texana when plants from the San Marcos River were initially brought into the SMARC to maintain ex situ populations (Fries and Power 1999). Upon further observation, overall damage to Z. texana ex situ populations was minor. P. obscuralis did not again damage aquatic plants being propagated at SMARC until 2012 when additional aquatic plant species were brought in for restoration efforts in the San Marcos River.

Monitoring and Marking Techniques for the Endangered Comal Springs Riffle Beetle, Heterelmis comalensis Bosse, Tuff, and Brown, 1988 (Coleoptera: Elmidae)

Abstract Two monitoring methods for the endangered Comal Springs riffle beetle, Heterelmis comalensis Bosse, Tuff, and Brown, 1988, were evaluated. The first used cotton cloth “lures” lodged within the substrate in close proximity to spring openings. The second evaluated the feasibility of marking H. comalensis with paint. During our evaluation, biofilms grew upon the lures over time, and within two weeks H. comalensis were collected. Numbers of H. comalensis (mean = 23, range = 4–53) collected from lures peaked at 10 weeks and then began to decline as the cotton cloth lures began to decompose. Three other invertebrate species, the riffle beetle Microcylloepus pusillus (LeConte, 1852), the endangered Comal Springs dryopid beetle Stygoparnus comalensis Barr and Spangler, 1992, and the endangered Pecks cave amphipod, Stygobromus pecki (Holsinger, 1967), were also collected from the lures, suggesting that this technique may have broad applicability as a passive monitoring tool for interstitial aquatic endemics and other endangered species. All species, including H. comalensis, were readily quantified, and the technique allowed for specimens to be returned alive to their site of capture.Marking H. comalensis elytra with paint was a feasible technique because marks were retained for up to three months; however, it may be more practical for laboratory experimentation rather than field use because it is timeconsuming and labor intensive. Recapture rates for marked individuals were low in situ, most likely due to unknown factors such as movement, dispersal, and the ratio of individuals marked compared to the population size. Nevertheless, our evaluation suggests that these two techniques in combination may provide a valid means to monitor and evaluate population trends of H. comalensis without negatively affecting the species.

Distribution and occurrence of the exotic digenetic trematode (Centrocestus formosanus), its exotic snail intermediate host (Melanoides tuberculatus), and rates of infection of fish in springs systems in western Texas

Abstract We examined the distribution and co-occurrence of the exotic digenetic trematode Centrocestus formosanus, its exotic intermediate host the red-rim melania snail Melanoides tuberculatus, and rates of infection of fish in 10 spring systems throughout western Texas during 1999 and 2011. Four of the spring systems (East Sandia Springs, Independence Creek, Big Bend National Park Refugium Pond, and Clear Creek) did not contain red-rim melania snails in 1999 and 2011. Four spring systems that were populated with snails (San Felipe Creek, San Solomon Springs, Phantom Lake, and Diamond Y Springs) contained the trematode and were positive for branchial infection in fish except Diamond Y Springs which contained uninfected snails and fish. Since 1999, two additional spring systems, Pinto Creek and Devils River, contained the trematode. We found a high prevalence of branchial infection for fish collected regardless of species. Seventeen of the 21 species of fish collected from the spring systems were positive for infection by trematodes. On average, the most infected genera were Micropterus and Lepomis followed in decreasing order by Etheostoma, Dionda, Astyanax, Cichlasoma, Notropis, Cyprinella, Gambusia, Ictalurus, and Hypostomus. Seven state-listed or federally listed species we collected had a relatively high percentage (mean = 52%) of developing metacercarial cysts except E. grahami (mean = 14%). Our laboratory study suggests that, for Gambusia, rates of infection by trematodes are species–specific with G. affinis having significantly more cysts than did G. nobilis and G. gaigei. Our work extended the documented range of red-rim melania snails and C. formosanus in Texas.

Epicauta polingi (Coleóptera: Meloidae) Feeding on Mountain Laurel (Sophora secundiflora) and Guajillo (Acacia berlandieri) in West Texas

Abstract. On 17 June 2014, large aggregations of Epicauta polingi Werner 1943 (Coleóptera: Meloidae) were observed feeding on the leaves and stems of mountain laurel, Sophora secundiflora (Ortega) Lag. ex DC.; and guajillo, Acacia berlandieri Benth. (Fabaceae). After examination of the existing literature it was determined that these two plants represented new host records for E. polingi.