Cytogenetic analysis of three sea catfish species (Teleostei, Siluriformes, Ariidae) with the first report of Ag-NOR in this fish family

Despite their ecological and economical importance, fishes of the family Ariidae are still genetically and cytogenetically poorly studied. Among the 133 known species of ariids, only eight have been karyotyped. Cytogenetic analyses performed on Genidens barbus and Sciades herzbergii revealed that both species have 2n = 56 chromosomes and Cathorops aff. mapale has 2n = 52 chromosomes: Genidens barbus has 10 Metacentrics (M), 14 Submetacentrics (SM), 26 Subtelocentrics (ST), and 6 Acrocentrics (A), Sciades herzbergii has 14M, 20SM, 18ST and 4A, whereas Cathorops aff. mapale has 14M, 20SM, and 18ST. The nucleolus organizer regions (NORs) were found in a single chromosome pair on the short arm of a large-sized ST pair in Genidens barbus and on the short arm of a middle-size SM pair in Cathorops aff. mapale. Multiple NORs on the short arms of two large-sized ST pairs were found in Sciades herzbergii. The occurrence of diploid numbers ranging from 2n = 52 through 56 chromosomes and the presence of different karyotypic compositions, besides the number and position of NORs suggest that several numeric and structural chromosome rearrangements were fixed during the evolutionary history of this fish family

Population genetic structure of the brown tiger prawn, Penaeus esculentus, in tropical northern Australia

Eight polymorphic microsatellite loci were analysed in six population samples from four locations of the Australian endemic brown tiger prawn, Penaeus esculentus. Tests of Hardy-Weinberg equilibrium were generally in accord with expectations, with only one locus, in two samples, showing significant deviations. Three samples were taken in different years from the Exmouth Gulf. These showed no significant heterogeneity, and it was concluded that they were from a single panmictic population. A sample from Shark Bay, also on the west coast of Australia, showed barely detectable differentiation from Exmouth Gulf (F (ST) = 0 to 0.0014). A northeast sample from the Gulf of Carpentaria showed low (F (ST) = 0.008) but significant differentiation from Moreton Bay, on the east coast. However, Exmouth Gulf/Shark Bay samples were well differentiated from the Gulf of Carpentaria/Moreton Bay (F (ST) = 0.047-0.063). The data do not fit a simple isolation by distance model. It is postulated that the east-west differentiation largely reflects the isolation of east and west coast populations that occurred at the last glacial maximum when there was a land bridge between north-eastern Australia and New Guinea

Effects of autotomy on long-term survival and growth of painted spiny lobster (Panulirus versicolor) on the Great Barrier Reef, Australia

The effects of autotomy (shedding of appendages) on survival and growth rates of painted spiny lobster were investigated at Northwest Island (23° 18′ S, 152° 43′ E) during the period 2003–2006. Adult lobsters were captured, tagged, and classified as either uninjured (n = 68), minimally injured (n = 39) or moderately injured (n = 19) depending on the number and type of appendages that were autotomized during capture and handling. Six to thirty-six months after release, 86 lobsters were recaptured (mean time at large = 305 days). Recapture rates of uninjured (64.7%), minimally injured (71.8%), and moderately injured lobsters (73.7%) were not significantly different. Similarly, mean annualized growth rates of uninjured, minimally injured, and moderately injured lobsters were not significantly different. This suggests that the energetic cost of a single episode of autotomy is either negligible or exists as a trade-off with some other life history trait, such as reduced reproductive performance. These results support the use of certain management tools (e.g., size limits) that prescribe release of non-legal lobsters, regardless of their injury status

Prey ecology and behaviour affect foraging strategies in the Great Cormorant

The Wne link between a particular dive pattern and a speciWc prey item represents a challenging task in the analysis of marine predator\u2013prey relationships. There is growing evidence that prey type aVects diving seabirds\u2019 foraging strategies, dive shapes and underwater activity costs. This study investigates whether a generalist diver, the Great Cormorant Phalacrocorax carbo, modiWes the time budget allocated to prey-capture behaviour and breathing strategies (reactive vs. anticipatory) with respect to the prey type (pelagic vs. benthic). Video recordings of 91 Great Cormorants show how the ecology and behaviour of their main prey, Mullets (Mugilidae) and Flounders Platichthys Xesus, aVect dive/surface durations and the diving pattern. The demersal habit and the low mobility of Flounders leads to an easy access to prey with an anticipatory strategy. Moreover, the patchy distribution of this Wsh species increases prey-capture rates. Conversely, Mullets exploit the whole water column and are highly mobile, and this is reXected in the need of performing two sequential dives to capture a prey, both longer and likely more expensive, with a consequent switch of strategy from reactive in the searching phase to anticipatory breathing during prey-capture events. This study provides evidence that a generalist diver may switch between diVerent foraging strategies, and it shows how each of them may be optimal under particular ecological conditions. These constraints inXuence the dynamics that operate within the marine food chains and have relevant implications in managing lagoon areas, including Wsh ponds