Kim B. Sewell

Checklist of Parasites from Heron Island, Great Barrier Reef

The parasites found in 185 host species, including 122 fishes, at Heron Island and adjacent reefs in the Capricorn-Bunker group are listed. Parasites are identified to family or below. Many of the 580 records have not previously been published; the present location of these specimens is given.

Stock discrimination of orange roughy, Hoplostethus atlanticus, by parasite analysis

The parasite fauna of the viscera of 1251 orange roughy,Hoplostethus atlanticus, collected in 1983 to 1986 from eight areas off southern Australia and three areas off New Zealand, was examined for evidence of discrete host populations. Fish from each area were divided into three length groups which averaged close to 28, 37, and 42 cm. Canonical multivariate analysis of data on larval nematodes (Anisakis spp.,Terranova sp., and a spirurid) and larval cestodes (Hepatoxylon trichiuri andCallitetrarhynchus sp.) discriminated five Australian and three New Zealand stocks. These were for Australia: (1) Great Australian Bight (2) South Australia/west Victoria/west and south Tasmania, (3) Cascade Plateau/Tasman Rise, (4) north-east Tasmania, (5) New South Wales; and for New Zealand: (1) north-east New Zealand, (2) south-east New Zealand, (3) west New Zealand. No significant differences in parasite fauna were detected between samples of fish taken within the spawning season and those taken outside the spawning season in the same area. In one southern Australian stock there was a north-south cline in the numbers ofAnisakis spp. This was apparent in both small (immature) and medium-sized (mature) fish. We conclude thatHoplostethus atlanticus is a sedentary species with little movement between fishmanagement zones.

Ultrastructure of spermiogenesis and spermatozoa of Decadidymus gulosus, Temnocephala dendyi, T. minor, Craspedella sp., C. spenceri and Diceratocephala boschmai (Platyhelminthes, Temnocephalida, Temnocephalidae), with emphasis on the intercentriolar body and zone of differentiation

Summary Examination of the ultrastructure of spermiogenesis and mature sperm in six species of Temnocephalidae revealed the origin of the spiral region of microtubules in the sperm shaft. The region is characteristic of many Temnocephalida but absent from other platyhelminth taxa. During spermiogenesis, an electron-dense heel region develops from, or adjacent to, the outer plates of the intercentriolar body in the zone of differentiation. The intercentriolar body splits into two halves, each of which remains attached to one basal body via the dense heel. The entire anchoring apparatus of each flagellum, consisting of the basal body, striated rootlet and the intercentriolar body and dense heel, rotates around the spermatid shaft until the two basal bodies lie parallel to each other. This rotation causes the compression of one of the two semi-circular rows of microtubules which originate on opposite sides of the spermatid shaft. The row is compressed to a tight horseshoe shape with electron-dense material b...

Perkinsus in Australia.

ABSTRACT: Perkinsus spp. are widespread in Australian molluscs. They have been associated with deaths of abalone, Haliotis laevigata , in South Australia and of clams, Tridacna gigas , in Queensland. Infection in H. laevigata is linked to high environmental temperature. The number of Perkinsus species present in Australia is not known although several morphological types of trophozoites occur in different hosts. Experiments on transmission indicate that some Perkinsus species can infect many species of mollusc.

Organisation of the epidermal syncytial mosaic in Diceratocephala boschmai (Temnocephalida: Platyhelminthes)

The epidermis of Diceratocephala boschmai Baer, 1952 (Temnocephalida : Platyhelminthes) was studied using silver-nitrate staining and electron microscopy. The epidermis consists of six syncytia separated by lateral membranes: the frontal, trunk, stalk, adhesive disc syncytia, and a pair of post-tentacular syncytia. Neighbouring syncytia differ in many characters including (1) the presence or absence of locomotory cilia, (2) the degree of the differentiation of the apical cytoplasm layer, (3) the presence or absence of bundles of cytoskeletal filaments, imaginations of basal membrane and other specialised cytoplasmatic structures, (4) the abundance of hemidesmosomes at the basal membrane, and (5) the abundance and nature of gland ducts penetrating the syncytium. These structural differences reflect functional differences between the syncytia. Thus, multisyncytial organisation of the epidermis may be explained by functional differences between the syncytia. Only between the frontal and trunk syncytia has no apparent ultrastructural difference been found.

A light microscope study of the attachments organs and their role in locomotion of Craspedella sp. (Platyhelminthes: Rhabdocoela: Temnocephalidae), an ectosymbiont from the branchial chamber of Cherax quadricarinatus (Crustacea: Parastacidae) in Queenslan

The five anterior tentacles and the single posterior attachment organ of the temnocephalan flatworm Craspedella sp. perform important roles in locomotion and attachment. Craspedella sp. moved using a low ‘looping’ motion by alternately attaching the ventro-distal regions of the central three tentacles and the ventral surface of the posterior attachment organ. Secretion from the tentacles is by rod-shaped rhabdites produced in rhabditogen cells. There are more rhabdites and pores in the region of the distal concavity on each of the central three tentacles. It was not possible to determine the presence or not of suction at the distal concavities. The posterior attachment organ has true suctorial ability, can create a reduced pressure and a marginal valve appears to prevent influx of water. However, the ‘sucker’ is also supplied with a granular secretion from posterior gland cells which can leave a conspicuous, annular footprint on glass surfaces. The posterior secretion enables the worms to attach to surfac...

A scanning electron microscope study of Craspedella sp. from the branchial chamber of redclaw crayfish, Cherax quadricarinatus, from Queensland, Australia

Epidermal topography was examined, including papillate ridges, grooves and ciliated sensory papillae of Craspedella sp. from the branchial chamber of redclaw crayfish, Cherax quadricarinatus, from Queensland, Australia. Rhabdites were observed to discharge from ducts opening mainly in a small distal region of the ventral epidermis of the three central (of five) tentacles. These regions, devoid of ciliated sensory papillae, serve to adhere the anterior end of the worms during locomotion. Secretions from glands associated with the posterior attachment organ were observed to discharge from pores on the outside region of the ventral surface of the disc.

Evidence that blood flukes (Trematoda: Aporocotylidae) of chondrichthyans infect bivalves as intermediate hosts: indications of an ancient diversification of the Schistosomatoidea☆

Blood flukes (Aporocotylidae) of actinopterygians (bony fishes) have been shown to infect freshwater gastropods and marine polychaetes as intermediate hosts. However, no life cycle is known for any aporocotylid of chondrichthyans (cartilaginous fishes) and no adult aporocotylid has been linked to a cercaria infecting a bivalve. Here we report two novel infections that fill these gaps. Cercariae consistent with the family Aporocotylidae were found developing in sporocysts in the gonad of the surf pipi, Donax deltoides Lamarck, 1818 (Bivalvia: Donacidae), from Stockton Beach, central New South Wales, Australia. Adult aporocotylids were found in the heart of the giant shovelnose ray, Glaucostegus typus (Anonymous [Bennett], 1830), from Moreton Bay, southeastern Queensland, Australia. Phylogenetic analyses of the 28S rDNA region generated from the new specimens resulted in phylograms in which the two parasites form a strongly supported clade with Chimaerohemecus trondheimensis van der Land, 1967, the only aporocotylid known from a holocephalan and the only other chondrichthyan-infecting aporocotylid for which sequence data are available. Most marine aporocotylids of actinopterygians also form a strongly supported clade. These findings lead us to hypothesise that the aporocotylids of chondrichthyans are distinct from all other blood flukes in infecting bivalves as intermediate hosts. Putative cophyly between three major blood fluke clades and both definitive and intermediate host groups is consistent with diversification of the Schistosomatoidea over 400million years ago.

Australian spiny mountain crayfish and their temnocephalan ectosymbionts: an ancient association on the edge of coextinction?

Australian spiny mountain crayfish (Euastacus, Parastacidae) and their ecotosymbiotic temnocephalan flatworms (Temnocephalida, Platyhelminthes) may have co-occurred and interacted through deep time, during a period of major environmental change. Therefore, reconstructing the history of their association is of evolutionary, ecological, and conservation significance. Here, time-calibrated Bayesian phylogenies of Euastacus species and their temnocephalans (Temnohaswellia and Temnosewellia) indicate near-synchronous diversifications from the Cretaceous. Statistically significant cophylogeny correlations between associated clades suggest linked evolutionary histories. However, there is a stronger signal of codivergence and greater host specificity in Temnosewellia, which co-occurs with Euastacus across its range. Phylogeography and analyses of evolutionary distinctiveness (ED) suggest that regional differences in the impact of climate warming and drying had major effects both on crayfish and associated temnocephalans. In particular, Euastacus and Temnosewellia show strong latitudinal gradients in ED and, conversely, in geographical range size, with the most distinctive, northern lineages facing the greatest risk of extinction. Therefore, environmental change has, in some cases, strengthened ecological and evolutionary associations, leaving host-specific temnocephalans vulnerable to coextinction with endangered hosts. Consequently, the extinction of all Euastacus species currently endangered (75%) predicts coextinction of approximately 60% of the studied temnocephalans, with greatest loss of the most evolutionarily distinctive lineages.