First published record of the pathogenic monogenean parasite Neobenenenia melleni (Capsalidae) from Australia

The monogenean Neobenedenia melleni (Mac- Callum, 1927) Yamaguti 1963 is a well-known and virulent pathogen in culture conditions recorded from the skin of many teleost fish species worldwide. Until now, N. melleni has not been reported from wild or cultured fish in Australian waters. This study documents a recent outbreak of N. melleni that occurred on Lates calcarifer (barramundi) cultivated in sea cages in Hinchinbrook Channel between Hinchinbrook Island and mainland Queensland, Australia, which resulted in the loss of 200 000 fish (50 tonnes). The origin of this outbreak is unclear because N. melleni has not been recorded from any wild host species in Australia and strict quarantine regulations exclude the possibility of its introduction on imported fish. We propose that N. melleni occurs naturally on wild populations of some teleost species in Australian waters and that the few surveys of wild fish conducted along the eastcoast have failed to report this species. The possibility that uncharacteristically low water temperatures led to the outbreak is discussed.

Heritability estimates for growth in the tropical abalone Haliotis asinina using microsatellites to assign parentage

The tropical abalone Haliotis asinina is a wild-caught and cultured species throughout the Indo-Pacific as well as being an emerging model species for the study of haliotids. H. asinina has the fastest recorded natural growth rate of any abalone and reaches sexual maturity within one year. As such, it is a suitable abalone species for selective breeding for commercially important traits such as rapid growth. Estimating the amount of variation in size that is attributable to heritable genetic differences can assist the development of such a selective breeding program. Here we estimated heritability for growth-related traits at 12 months of age by creating a single cohort of 84 families in a full-factorial mating design consisting of 14 sires and 6 dams. Of 500 progeny sampled, 465 were successfully assigned to their parents based on shared alleles at 5 polymorphic microsatellite loci. Using an animal model, heritability estimates were 0.48 +/- 0.15 for shell length, 0.38 +/- 0.13 for shell width and 0.36 +/- 0.13 for weight. Genetic correlations were > 0.98 between shell parameters and weight, indicating that breeding for weight gains could be successfully achieved by selecting for shell length. (c) 2006 Elsevier B.V. All rights reserved.

A rapidly evolving secretome builds and patterns a sea shell

Background: Instructions to fabricate mineralized structures with distinct nanoscale architectures, such as seashells and coral and vertebrate skeletons, are encoded in the genomes of a wide variety of animals. In mollusks, the mantle is responsible for the extracellular production of the shell, directing the ordered biomineralization of CaCO3 and the deposition of architectural and color patterns. The evolutionary origins of the ability to synthesize calcified structures across various metazoan taxa remain obscure, with only a small number of protein families identified from molluskan shells. The recent sequencing of a wide range of metazoan genomes coupled with the analysis of gene expression in non-model animals has allowed us to investigate the evolution and process of biomineralization in gastropod mollusks. Results: Here we show that over 25% of the genes expressed in the mantle of the vetigastropod Haliotis asinina encode secreted proteins, indicating that hundreds of proteins are likely to be contributing to shell fabrication and patterning. Almost 85% of the secretome encodes novel proteins; remarkably, only 19% of these have identifiable homologues in the full genome of the patellogastropod Lottia scutum. The spatial expression profiles of mantle genes that belong to the secretome is restricted to discrete mantle zones, with each zone responsible for the fabrication of one of the structural layers of the shell. Patterned expression of a subset of genes along the length of the mantle is indicative of roles in shell ornamentation. For example, Has-sometsuke maps precisely to pigmentation patterns in the shell, providing the first case of a gene product to be involved in molluskan shell pigmentation. We also describe the expression of two novel genes involved in nacre (mother of pearl) deposition. Conclusion: The unexpected complexity and evolvability of this secretome and the modular design of the molluskan mantle enables diversification of shell strength and design, and as such must contribute to the variety of adaptive architectures and colors found in mollusk shells. The composition of this novel mantle-specific secretome suggests that there are significant molecular differences in the ways in which gastropods synthesize their shells.

Economic , Educational and Conservation Benefits of Sea Turtle Based Ecotourism: A Study Focused on Mon Repos

The study examines the economic, educational and conservation values of sea turtle-based ecotourism in Australia. The centre-piece of this research is a case study undertaken at the Mon Repos Conservation Park located near the town of Bundaberg, Queensland. Each year from mid-November to end of March, thousands of visitors visit Mon Repos Conservation Park to view sea turtles either nesting on the one km stretch of beach or to see hatchlings emerge from their nests and march on to the sea or both. As a result of this activity there are considerable economic benefits to the Bundaberg region during the sea turtle season. The study examines the economic impact of sea turtle viewing at Mon Repos to the region. The study assesses the recreational value of sea turtle viewing. Furthermore, sea turtle-based ecotourism also provides educational and conservation benefits that are important for the protection and conservation of sea turtles, especially in Australia. The study specifies the extent of the educational impact and conservation appreciation of sea turtle viewing at Mon Repos Conservation Park. As a background to the study, Mon Repos visitors’ profile and socio-economic data of visitors are provided. In order to conduct this study, 1,200 survey forms were distributed, out of which 519 usable responses were obtained.

What are the economic prospects of developing aquaculture in Queensland to supply the low price white fillet market? Lessons from the US channel catfish industry

The farming of channel catfish (Ictalurus punctatus) is the largest (by volume and value) and most successful (in terms of market impact) aquaculture industry in the United States of America. Farmed channel catfish is the most consumed (in terms of volume per capita) fish fillet in the U.S. market. Within Australia, it has long been suggested by researchers and industry that silver perch (Bidyanus bidyanus) and possibly other endemic teraponid species possess similar biological attributes for aquaculture as channel catfish and may have the potential to generate a similar industry. The current teraponid industry in Australia, however, shows very little resemblance to the catfish industry, either in production style or market philosophy. A well established budget framework from the literature on U.S. channel catfish farming has been adapted for cost and climate conditions of the Burdekin region, Queensland, Australia. Breakeven prices for the hypothetical teraponid farms were found to be up to 50% higher than those published for catfish farms however were much lower than those reported for silver perch production in Australia using current, endemic styles of production. The breakeven prices for the hypothetical teraponid farms were most sensitive (in order of significance) to feed prices, production rates, interest rates, fingerling prices and electricity prices. At equivalent feed costs the costs of production between the hypothetical catfish farms in the Mississippi, U.S. and the hypothetical teraponid farms in the Burdekin, Australia were remarkably similar. The cost of feeds suitable for teraponid production in Australia are currently around double that of catfish feeds in the U.S. Issues currently hindering the development of a large scale teraponid industry in Australia are discussed.

The deep-sea teleost cornea: a comparative study of gadiform fishes

The corneal structure of three deep-sea species of teleosts (Gadiformes, Teleostei) from different depths (250-4000 m) and photic zones are examined at the level of the light and electron microscopes. Each species shows a similar but complex arrangement of layers with a cornea split into dermal and scleral components. The dermal cornea comprises an epithelium overlying a basement membrane and a dermal stroma with sutures and occasional keratocytes. Nezumia aequalis is the only species to possess a Bowman's layer, although it is not well-developed. The scleral cornea is separated from the dermal cornea by a mucoid layer and, in contrast to shallow-water species, is divided into three main layers; an anterior scleral stroma, a middle or iridescent layer and a posterior scleral stroma. The iridescent layer of collagen and intercalated cells or cellular processes is bounded by a layer of cells and the posterior scleral stroma overlies a Descemet's membrane and an endothelium. In the relatively shallow-water Microgadus proximus, the keratocytes of the dermal stroma, the cells of the iridescent layer and the endothelial cells all contain aligned endoplasmic reticulum, which may elicit an iridescent reflex. No alignment of the endoplasmic reticulum was found in N. aequalis or Coryphanoides (Nematonurus) armatus. The relative differences between shallow-water and deep-sea corneas are discussed in relation to the constraints of light, depth and temperature.

Amino acid synthesis in the symbiotic sea anemone Aiptasia pulchella

Symbiotic Aiptasia pulchella and freshly isolated zooxanthellae were incubated in (NaHCO3)-C-14 and NH4Cl for 1 to 240 min, and samples were analysed by reverse-phase high-performance liquid chromatography (HPLC) and an online radiochemical detector. NH4+ was first assimilated into C-14-glutamate and C-14-glutamine in the zooxanthellae residing in A. pulchella. The specific activities (dpm nmol(-1)) of C-14-glutamate and C-14-glutamine in vivo, were far greater in the zooxanthellae than in the host tissue, indicating that NH4+ was principally incorporated into the glutamate and glutamine pools of the zooxanthellae. C-14-alpha-ketoglutarate was taken up from the medium by intact A. pulchella and assimilated into a small amount of C-14-glutamate in the host tissue, but no C-14-glutamine was detected in the host fraction. The C-14-glutamate that was synthesized was most likely produced from transamination reactions as opposed to the direct assimilation of NH4+. The free aminoacid composition of the host tissue and zooxanthellae of A. pulchella was also measured. The results presented here demonstrate that NH4+ was initially assimilated by the zooxanthellae of A. pulchella.

Seven retinal specializations in the tubular eye of the deep-sea pearleye, Scopelarchus michaelsarsi: A case study in visual optimization

The deep-sea pearleye, Scopelarchus michaelsarsi (Scopelarchidae) is a mesopelagic teleost with asymmetric or tubular eyes. The main retina subtends a large dorsal binocular field, while the accessory retina subtends a restricted monocular field of lateral visual space. Ocular specializations to increase the lateral visual field include an oblique pupil and a corneal lens pad. A detailed morphological and topographic study of the photoreceptors and retinal ganglion cells reveals seven specializations: a centronasal region of the main retina with ungrouped rod-like photoreceptors overlying a retinal tapetum; a region of high ganglion cell density (area centralis of 56.1x10(3) cells per mm(2)) in the centrolateral region of the main retina; a centrotemporal region of the main retina with grouped rod-like photoreceptors; a region (area giganto cellularis) of large (32.2+/-5.6 mu m(2)), alpha-like ganglion cells arranged in a regular array (nearest neighbour distance 53.5+/-9.3 mu m with a conformity ratio of 5.8) in the temporal main retina; an accessory retina with grouped rod-like photoreceptors; a nasotemporal band of a mixture of rod-and cone-like photoreceptors restricted to the ventral accessory retina; and a retinal diverticulum comprised of a ventral region of differentiated accessory retina located medial to the optic nerve head. Retrograde labelling from the optic nerve with DiI shows that approximately 14% of the cells in the ganglion cell layer of the main retina are displaced amacrine cells at 1.5 mm eccentricity. Cryosectioning of the tubular eye confirms Matthiessen's ratio (2.59), and calculations of the spatial resolving power suggests that the function of the area centralis (7.4 cycles per degree/8.1 minutes of are) and the cohort of temporal alpha-like ganglion cells (0.85 cycles per degree/70.6 minutes of are) in the main retina may be different. Low summation ratios in these various retinal zones suggests that each zone may mediate distinct visual tasks in a certain region of the visual field by optimizing sensitivity and/or resolving power.

The eyes of deep-sea fish I: Lens pigmentation, tapeta and visual pigments

Deep-sea fish, defined as those living below 200 m, inhabit a most unusual photic environment, being exposed to two sources of visible radiation: very dim downwelling sunlight and bioluminescence, both of which are, in most cases. maximal at wavelengths around 450-500 nm. This paper summarises the reflective properties of the ocular tapeta often found in these animals the pigmentation of their lenses and the absorption characteristics of their visual pigments. Deepsea tapeta usually appear blue to the human observer. reflecting mainly shortwave radiation. However, reflection in other parts of the spectrum is not uncommon and uneven tapetal distribution across the retina is widespread. Perhaps surprisingly, given the fact that they live in a photon limited environment, the lenses of some deep-sea teleosts are bright yellow, absorbing much of the shortwave part of the spectrum. Such lenses contain a variety of biochemically distinct pigments which most likely serve to enhance the visibility of bioluminescent signals. Of the 195 different visual pigments characterised by either detergent extract or microspectrophotometry in the retinae of deep-sea fishes, cn. 87% have peak absorbances within the range 468-494 nm. Modelling shows that this is most likely an adaptation for the detection of bioluminescence. Around 13% of deep-sea fish have retinae containing more than one visual pigment. Of these, we highlight three genera of stomiid dragonfishes, which uniquely produce far red bioluminescence from suborbital photophores. Using a combination of longwave-shifted visual pigments and in one species (Malacosteus niger) a chlorophyll-related photosensitizer. these fish have evolved extreme red sensitivity enabling them to see their own bioluminescence and giving them a private spectral waveband invisible to other inhabitants of the deep-ocean. (C) 1998 Elsevier Science Ltd. All rights reserved.

The eyes of deep-sea fish II. Functional morphology of the retina

Three different aspects of the morphological organisation of deep-sea fish retinae are reviewed: First, questions of general cell biological relevance are addressed with respect to the development and proliferation patterns of photoreceptors, and problems associated with the growth of multibank retinae, and with outer segment renewal are discussed in situations where there is no direct contact between the retinal pigment epithelium and the tips of rod outer segments. The second part deals with the neural portion of the deep-sea fish retina. Cell densities are greatly reduced, yet neurohistochemistry demonstrates that all major neurotransmitters and neuropeptides found in other vertebrate retinae are also present in deep-sea fish. Quantitatively, convergence rates in unspecialised parts of the retina are similar to those in nocturnal mammals. The differentiation of horizontal cells makes it unlikely that species with more than a single visual pigment are capable of colour vision. In the third part. the diversity of deep-sea fish retinae is highlighted. Based on the topography of ganglion cells, species are identified with areae or foveae located in various parts of the retina, giving them a greatly improved spatial resolving power in specific parts of their visual fields. The highest degree of specialisation is found in tubular eyes. This is demonstrated in a case study of the scopelarchid retina, where as many as seven regions with different degrees of differentiation can be distinguished, ranging from an area giganto cellularis, regions with grouped rods to retinal diverticulum. (C) 1998 Elsevier Science Ltd. All rights reserved.

Tidal effects on sea water intrusion in unconfined aquifers

A variable-density groundwater model is used to analyse the effects of tidal fluctuations on sea-water intrusion in an unconfined aquifer. It is shown that the tidal activity forces the sea-water to intrude further inland and it also creates a thicker interface than would occur without tidal effects. Moreover, the configuration of the interface is radically changed when the tidal fluctuations are included. This is because of the dramatic changes in the flow pattern and velocity of the groundwater near the shoreline. For aquifer depths much larger than tidal amplitudes, the tidal fluctuation does not have much effect on how far the sea-water intrudes into the aquifer; nevertheless, a significant change in the configuration of concentration contours because of the effect of tidal fluctuations is observed. This change is more noticeable at the top of the aquifer, near the water table, than at the bottom of the aquifer, and is caused by the infiltration of salt water into the top of the aquifer at higher tidal levels. A flatter beach slope, therefore, intensifies this phenomenon. The interface configurations do not change noticeably over the course of a tidal cycle. Neglecting tidal fluctuation effects results in an inaccurate evaluation of the water table elevation at the land end of the aquifer, although no distinguishable difference is seen between the water tables near the shoreline. Where the landward boundary condition is a constant head, the effects of tidal fluctuations on sea-water intrusion are more pronounced than for cases where the landward boundary condition is a specified flux. Also it is shown that the effects of tidal fluctuations are more significant for a sloping beach than for a vertical shoreline and the salt water intrudes further inland for the sloping case. (C) 1999 Elsevier Science B.V. All rights reserved.