Mass Transfer Performance of a Marine Zooplankton Olfactometer

By adopting different methods to the inlet of a zooplankton olfactometer, the current study investigates the effect of the energy of chemical flow on the Gnathiid isopod crustaceans predicted behavior. These are mobile external parasites of fishes that have a significant impact on the health of their hosts. They rely at least in part on olfactory cues to find the host fish. To better understand host-finding dynamics in these parasites, a study was conducted with the simulations as a blueprint for developing a 3-dimensional test apparatus similar to what has been used for studying olfactory orientation in insects. The simulated olfactometer has four legs, each leg forming an inlet where fluids are introduced into the flow domain. There is one outlet at the center of the device. A mixture of water and chemicals is presented by applying a multi-component system. The shear and chemical concentration distribution were conducted to see how fluid physics plays a role in creating a chemical landscape. Computational results show distinct regions separated by high chemical concentration gradients when introducing chemicals from one leg. Changing the fluid inflow from one common inlet to three inlets shows that the chemical distribution exhibits steeper gradients than the typical inlet case, depicting that the gradual chemical concentrations can drive the animal toward the target faster. The best behavior that gives higher chemical gradients is obtained through the study when using three sub-inlets and Schmidt number between 3 and 10.

New gnathiid isopod crustaceans (Cymothoida) from Heron Island and Wistari Reef, southern Great Barrier Reef

Eleven species including six new species of Gnathiidae (Crustacea, Isopoda, Cymothoida) are reported from the Heron Island and Wistari Reef, Capricorn Group, southern Great Barrier Reef: Elaphognathia queenslandica sp. nov., Gnathia acrorudus sp. nov., Gnathia capricornica sp. nov., Gnathia carinodenta sp. nov., Gnathia formosa sp. nov. and Gnathia glaucostega sp. nov. Gnathia cornuta Holdich & Harrison, 1980 and Gnathia grutterae Ferreira, Smit & Davies, 2010 are for the first time reported from Heron Island and new records from Heron Island are provided for Gnathia biorbis Holdich & Harrison, 1980, Gnathia variobranchia Holdich & Harrison, 1980, and Gnathia wistari Svavarsson & Bruce, 2012.

Occurrence of praniza larvae of a gnathiid (Isopoda, Gnathiidae) on wild-caught orange-spotted grouper, Epinephelus coioides (Hamilton, 1822) (Perciformes, Serranidae), in Lingayen Gulf, Philippines

Praniza larvae of a gnathiid isopod were retrieved from the gills and branchial cavity of wild-caught orange-spotted grouper, Epinephelus coioides (Hamilton, 1822) (Perciformes, Serranidae) in Lingayen Gulf, Philippines. The prevalence and mean intensity of the praniza larvae were 82.3% and 2.2 on the gill filaments and 23.5% and 2.5 in the branchial cavity, respectively. The praniza larva is described and illustrated as there has been no work on the morphology of the parasite in the country where it was collected, to date. This report involves a new record for larval gnathiid infection on E. coioides in the Philippines.

An experimental field test of susceptibility to ectoparasitic gnathiid isopods among Caribbean reef fishes

SUMMARYSusceptibility to infestation by a gnathiid isopod (Gnathia marleyi:Crustacea: Isopoda) was examined among 16 species from 9 families and 3 orders of common Caribbean reef fishes off St. John, United States Virgin Islands. Fish were placed in cages during times of peak gnathiid activity. Individuals from most (n=14) species were compared against a single species (French Grunt,Haemulon flavolineatum) that served as a standard and effectively controlled for the effects of habitat and variation in gnathiid abundance on exposure to and the likelihood and intensity of host infestation by gnathiids. All species were susceptible to infestation by gnathiids, with individual hosts harbouring up to 368 gnathiids. However, there was significant variation in levels of infestation among the 14 comparison species. Controlling for body size, nocturnal species from the families Haemulidae and Lutjanidae had the highest gnathiid infestation. Our finding that haemulids and lutjanids are particularly susceptible has important implications for the role of gnathiids in Caribbean reef food webs, given the role members of these families play in trophic connectivity between reefs and associated habitats. To our knowledge this is the first manipulative field study to examine variation among potential hosts in susceptibility to an ectoparasite in any terrestrial or aquatic system and is the greatest number of teleost hosts documented for any gnathiid species.