L. J. Newman

Sex and violence in hermaphrodites

Differences in objectives between males and females are a driving force in the evolution of copulatory mechanisms. Hermaphrodites can also have sexual conflicts, but caused by opposing sexual interests within rather than between individuals. One consequence seems to be that physically damaging sex, as occurs with the marine flatworm Pseudoceros bifurcus, might be favoured more in hermaphrodites than in species with separate sexes.

Stylochus (Imogene) matatasi n. sp. (Platyhelminthes, Polycladida): pest of cultured giant clams and pearl oysters from Solomon Islands.

A large polyclad flatworm has been consistently found associated with mortalities of the cultured giant clam,Tridacna gigas (L.) and the fouling pearl oysterPinctada maculata (Gould) in Solomon Islands.Stylochus (Imogene) matatasi n. sp. is described and a brief account of its biology is given.

Warning colouration in pseudocerotid flatworms (Platyhelminthes, Polycladida). A preliminary study

Many species of tropical and subtropical pseudocerotid flatworms are noted for their brilliant colour patterns and conspicuous behaviour and are suitable candidates for the investigation of aposematic colouration. This study gives the first experimental evidence of aposematic colouration in pseudocerotid flatworms. Coloured and uncoloured agar models of flatworms were used to determine whether a fish predator, the moon wrasse Thalassoma lunare, could learn to avoid colourful flatworms on the basis of their colour pattern. The results showed that uncoloured models were more significantly attacked than coloured models (1% significance) and that there was no significant difference between attacks made to live flatworms and their respective models. These results clearly indicate the operation of aposematism in brightly coloured flatworms and demonstrate the operation of mimicry as the agar models were essentially non-living mimics of the flatworms.

Halotolerance of the oyster predator, Imogine mcgrathi, a stylochid flatworm from Port Stephens, New South Wales, Australia

The stylochid flatworm, Imogine mcgrathi was confirmed as a predator of the pteriid oyster Pinctada imbricata. Occurring at an average of 3.2 per oyster spat collector bag, the flatworms were found to consume oysters at a rate of 0.035–0.057 d−1 in laboratory trials. Predation was affected by flatworm size with larger worms capable of consuming larger oysters and of consuming greater dry weights of oyster flesh. Irrespective of flatworm size, predation was generally confined to oysters less than 40 mm in shell height. Although all predation occurred at night, shading flatworms during the day did not significantly increase the rate of predation, but there were significant increases in the dry weight of oyster meat consumed. As a means of controlling flatworm infestations, salt, brine baths (250 g kg−1) and freshwater baths were effective in killing I. mcgrathi. The ease of use of hyper- or hyposaline baths then encouraged assessments of I. mcgrathi halotolerance. The flatworms were exposed to solutions ranging in salinity from 0 to 250 g kg−1for periods of from 5 min to 3 h. Despite showing both behavioural and physiological signs of stress, I. mcgrathi survived the maximum exposure time of 3 h at salinities in the range 7.5–60 g kg−1, inclusive. Beyond this range, the duration of exposure tolerated by flatworms decreased until 0 and 250 g kg−1, at which the flatworms no longer survived the minimum tested exposure of 5 min. Thus, despite the significant impact of other stylochids on commercial bivalves, at their current prevalence, I. mcgrathi can be controlled by exposing them to hyper- and hyposaline baths for the culture of P. imbricata in Port Stephens, NSW, Australia.

A molecular framework for the phylogeny of the Pseudocerotidae (Platyhelminthes, Polycladida)

Systematic relationships within the cotylean family Pseudocerotidae were examined using nucleotide sequences of the D3 expansion segment of the 28S rDNA gene. A previously suggested separation of Pseudoceros and Pseudobiceros based on the number of male reproductive systems was confirmed. Regardless of the algorithm employed, Pseudoceros always formed a monophyletic clade. Pseudobiceros appeared to be paraphyletic; however, a constrained maximum parsimony tree was not significantly longer (2 steps, α = 0.05). Additionally, the genera Maiazoon, Phrikoceros and Tytthosoceros were validated as taxonomic entities, and their relationships to other genera within the family were determined. Molecular data also supported species separations based on colour patterns. An intraspecific genetic distance of 1.14% was found for Pseudoceros bifurcus, whereas the intrageneric distance was 3.58%. Genetic distances among genera varied, with the closest distance being 2.048% between Pseudobiceros and Maiazoon, and the largest distance (8.345%) between Pseudoceros and Tytthosoceros.

The importance of the fixation of colour, pattern and form in tropical Pseudocerotidae (Platyhelminthes, Polycladida)

At last a fixation method that ensures tropical pseudocerotid polyclads are fixed flat, preserved for histological preparation and which also retains their colour pattern has been developed. FCA-PGPP (Formaldehyde Calcium Acetate-Propylene Glycol, Propylene Phenoxetol) fixative is frozen and worms are coaxed onto filter paper which is then laid on the frozen fixative. As a consequence, over 230 species have been documented from the southern Great Barrier Reef and eastern Papua New Guinea (Newman & Cannon, 1994; in press). It was determined that species diagnoses need to be based on colour pattern, general morphology of living animals and serial reconstructions of the male anatomy.

Taxonomic and biological observations on the tiger flatworm, Maritigrella crozieri (Hyman, 1939), new combination (Platyhelminthes, Polycladida, Euryleptidae) from Florida waters

The tiger flatworm, Maritigrella crozieri (Hyman, 1939) (Platyhelminthes, Polycladida, Cotylea) new combination, is redescribed from eastern Florida and the Florida Keys. This marine flatworm is one of the most common polyclads within warm temperate to tropical west Atlantic, yet it has been misidentified consistently as a pseudocerotid. Animals were kept alive in the laboratory for 3 weeks for biological observations. Findings indicated that these euryleptids employ hypodermic insemination, with multiple copulations occurring over several days. Sperm was transferred in sperm bundles bilaterally with little apparent damage to the epidermis of the copulating worms. Copulation sessions were variable and lasted an average of 15.4 min. In situ and laboratory observations indicated that M. crozieri fed exclusively on the mangrove ascidian Ecteinascidia turbinata Herdman, 1880, an individual consuming one prey zooid in an average of 17 min and an average of 19 zooids over 24h.

New genera of pseudocerotid flatworms (Platyhelminthes; Polycladida) from Australian and Papua New Guinean coral reefs

Two new genera, Maiazoon nov. gen. and Phrikoceros nov. gen. are described respectively from Madang, eastern Papua New Guinea and the Great Barrier Reef, Australia. The monotypic genus Maiazoon resembles Nymphozoon Hyman, 1959 since it possesses multiple male reproductive systems and multiple female pores although the latter genus lacks a penial stylet and sucker. Phrikoceros, with five new species, morphologically resembles Pseudobiceros although it possesses only one male reproductive system as found in Pseudoceros.

Light and Electron Microscope Study of Urosporidium cannoni N. Sp., a Haplosporidian Parasite of the Polyclad Turbellarian Stylochus sp.

ABSTRACT. Urosporidium cannoni n. sp. was found in most tissues of a polyclad turbellarian associated with commercial oyster farms from eastern Moreton Bay, Australia. Mature spores had 11 to 13 episporal tails at irregular intervals around the spore wall. The spherule, prominent in development, dispersed as the spores matured. Spores were found within cysts that contained up to a few hundred spores at the same stage of development. Mature cysts occurred in groups and their masses of dark, golden spores resulted in black patches on the otherwise red‐brown turbellarian. The infection may have commercial importance.

A new stylochid flatworm (Platyhelminthes, Polycladida) from Victoria, Australia and observations on its biology

There are only four polyclad flatworms currently known from temperate waters of Victoria, Australia, although these turbellarians are common inhabitants of rocky shores. A new stylochid flatworm, Stylochus pygmaeus sp. nov. (Platyhelminthes, Polycladida) or oyster leech is described here from Port Philip Bay, Victoria. This flatworm was observed feeding on three species of barnacles by extending its pharynx over its prey and extruding copious amounts of mucus. Worms also preferred to prey on larger‐sized barnacles regardless of the species. Further observations indicated that these worms deposited eggs at night inside empty barnacle shells. Each eggmass was brooded for several days with the worms only moving off to feed. Each egg capsule contained multiple embryos and after 5 or 6 days, positively photo‐tactic, four‐lobed Göttes larvae emerged. Larvae metamorphosed to juvenile flatworms 1–2 weeks post‐hatching but failed to settle and survive.