Nautilus Scientific Papers

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The genetic structure of Nautilus pompilius populations surrounding Australia and the Philippines

Rachel C. Williams, Benjamin C. Jackson, Ludovic Duvaux, Deborah A. Dawson, Terry Burke,
William Sinclair 2015 (subscription)

Abstract
Understanding the distribution of genetic diversity in exploited species is fundamental to successful conservation. Genetic structure and the degree of gene flow among populations must be assessed to design appropriate strategies to prevent the loss of distinct populations. The cephalopod Nautilus pompilius is fished unsustainably in the Philippines for the ornamental shell trade and has limited legislative protection, despite the species’ recent dramatic decline in the region. Here, we use 14 microsatellite markers to evaluate the population structure of N. pompilius around Australia and the Philippines. Despite their relative geographical proximity, Great Barrier Reef individuals are genetically isolated from Osprey Reef and Shark Reef in the Coral Sea (FST=0.312, 0.229, respectively). Conversely, despite the larger geographical distances between the Philippines and west Australian reefs, samples display a small degree of genetic structure (FST=0.015). Demographic scenarios modelled using approximate Bayesian computation analysis indicate that this limited divergence is not due to contemporary gene flow between the Philippines and west Australia. Instead, present-day genetic similarity can be explained by very limited genetic drift that has occurred due to large average effective population sizes that persisted at both locations following their separation. The lack of connectivity among populations suggests that immigrants from west Australia would not facilitate natural recolonization if Philippine populations were fished to extinction. These data help to rectify the paucity of information on the species’ biology currently inhibiting their conservation classification. Understanding population structure can allow us to facilitate sustainable harvesting, thereby preserving the diversity of genetically distinct stocks.
 
A revisited phylogeography of Nautilus pompilius
Lauren E. Vandepas, Frederick D. Dooley, Gregory J. Barord, Billie J. Swalla, Peter D. Ward 2016 (open access full publication)

Abstract
The cephalopod genus Nautilus is considered a “living fossil” with a contested number of extant and extinct species, and a benthic lifestyle that limits movement of animals between isolated seamounts and landmasses in the Indo-Pacific. Nautiluses are fished for their shells, most heavily in the Philippines, and these fisheries have little monitoring or regulation. Here, we evaluate the hypothesis that multiple species of Nautilus (e.g., N. belauensis, N. repertus and N. stenomphalus) are in fact one species with a diverse phenotypic and geologic range. Using mitochondrial markers, we show that nautiluses from the Philippines, eastern Australia (Great Barrier Reef), Vanuatu, American Samoa, and Fiji fall into distinct geographical clades. For phylogenetic analysis of species complexes across the range of nautilus, we included sequences of Nautilus pompilius and other Nautilus species from GenBank from localities sampled in this study and others. We found that specimens from Western Australia cluster with samples from the Philippines, suggesting that interbreeding may be occurring between those locations, or that there is limited genetic drift due to large effective population sizes. Intriguingly, our data also show that nautilus identified in other studies as N. belauensis,N. stenomphalus, or N. repertus are likely N. pompilius displaying a diversity of morphological characters, suggesting that there is significant phenotypic plasticity within N. pompilius.
 
Demographic disequilibrium in living nautiloids (Nautilus and Allonautilus): Canary in the coal mines?
W. Bruce Saunders , Emily Greenfest-Allen, Peter D. Ward 2017 (full article)
Abstract
Averaged demographic data from previously unfished populations of Nautilus and Allonautilus(Cephalopoda) provide a baseline to determine if a population is undisturbed and in “equilibrium” or is in “disequilibrium” as a result of fishery pressure. Data are available for previously undisturbed local nautiloid populations in Papua New Guinea, Australia, Indonesia, Fiji, Palau, American Samoa, New Caledonia and Vanuatu (total n = 2,669 live-caught, tagged and released animals). The data show that unfished populations average ~75% males and ~74% mature animals. By contrast, unpublished, anecdotal and historical records since 1900 from the heavily fished central Philippines have shown a persistent decline in trap yields and a change in demographics of N. pompilius. By 1979, a sample of fished live-caught animals (n = 353) comprised only ~28% males and ~27% mature animals. Continued uncontrolled trapping caused collapse of the fishery and the shell industry has moved elsewhere, including Indonesia. In addition, we show that estimated rates of population decline are offered by unpublished tag-release records in unfished Palau. These data show that patterns of trap yields and demographic differences between fished and unfished populations in relative age class and sex ratios can indicate disequilibria wrought by fisheries pressure that can render local populations inviable. Given adequate samples (n ≥100 live-caught animals), a threshold of <50% males and mature animals in fished populations should signal the need to initiate curative conservation initiatives. The current trajectory of uncontrolled nautiloid fisheries can only mean trouble and possibly extinction of local populations of this ancient, iconic molluscan lineage.
 
Antibiotic Treatment of Mucodegeneration and Positive Buoyancy in a Chambered Nautilus,Nautilus Pompilius
Massimo Morpurgo, Gregory J. Barord 2018 (subscription Journal of Aquatic Animal Health - Wiley Online)

Abstract

The correct diagnosis and treatment of disease in chambered nautiluses is difficult. Their basic morphology and natural behaviors tend to mask the initial onset of a disease or infection and by the time it is observable, mortality usually occurs. Here, a single specimen of Nautilus pompilius at the Museum of Nature South Tyrol exhibited symptoms of an infection which included mucus production, abnormal buoyancy, irregular hood appearance, and inconsistent tentacle movement. Soon after, tetracycline hydrochloride was administered in bath form at 25 mg/l in seawater daily, for 30 minutes, over six consecutive days. The specimen regained normal buoyancy after the fifth day. After the six‐day treatment, the specimen regained all normal behaviors and appearance within two weeks. Today, more than a year after treatment, the specimen is exhibiting normal behaviors with no adverse reactions. Tetracycline, when administered soon after observing symptoms of an infection, was effective at halting the progression of the symptoms and led to the full recovery of the specimen.
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