Unicorn Leatherjacket Research Articles

Diploproctodaeum spp. (Digenea, Lepocreadiidae) in Australian and New Caledonian waters including two new species from Tetraodontiformes and new records of related species

AbstractDiploproctodaeum monstrosum sp. nov. is described from Arothron stellatus and A. mappa from off Lizard Island, northern Great Barrier Reef. It differs from its congeners in having a body-length ventral scoop. Diploproctodaeum triodoni sp. nov. is described from Triodon macropterus off New Caledonia. It is distinguished by the extensive vitelline fields usually reaching to the ventral sucker and the folded scoop margins. Other related species are reported from new hosts or localities and dimensions are supplied for: Diploproctodaeum haustrum from Aluterus monoceros off New Caledonia; Diploproctodaeum arothroni from Arothron hispidus off Lizard Island and Ningaloo Reef, northern Western Australia, A. nigropunctatus off Lizard Island and Arothron manilensis off New Caledonia; Diploproctodaeum macracetabulum from Abalistes stellatus on the Swain Reefs, southern Great Barrier Reef and off New Caledonia; Diploproctodaeum momoaafata from Ostracion cubicus off Lizard Island; Diploproctodaeum rutellum from Platax teira off Heron Island, southern Great Barrier Reef; Diploproctodaeoides longipygum from Abalistes stellatus on the Swain Reefs and off New Caledonia; Diplocreadium tsontso from Balistoides conspicillum off Heron Island; Bianium arabicum from Lagocephalus sceleratus off New Caledonia. Attention is drawn to apparent convergent evolution in the body form of several families of trematodes infecting tetraodontids and especially species of Arothron.

Extraction and characterisation of pepsin-solubilised collagen from the skin of unicorn leatherjacket ( Aluterus monocerous)

Pepsin-solubilised collagen (PSC) was extracted from the skin of unicorn leatherjacket ( Aluterus monocerous), using 0.5 M acetic acid in the presence of pepsin from albacore tuna, yellowfin tuna or porcine pepsin at a level of 20 units/g of defatted skin. Yields of 8.48 ± 0.3%, 8.40 ± 0.3% and 7.56 ± 0.4% (wet weight basis) were obtained for PSC extracted with the aid of albacore tuna pepsin (APSC), yellowfin tuna pepsin (YPSC) and porcine pepsin (PPSC), respectively. All PSCs were classified as Type I collagen containing two α 1-chains and one α 2-chain with no disulphide bond. The peptide maps of different PSCs hydrolysed by V8 protease and lysyl endopeptidase were different. ATR-FTIR spectra analysis revealed that PSC molecules had the compact triple helical structure stabilised mainly by the hydrogen bond. T max of all PSCs (31.68–31.98 °C) shifted to lower values (29.33–29.40 °C) when dispersed in 0.05 M acetic acid, indicating the conformational changes in the collagen structure induced by acid. Relative viscosity of 0.03% PSC in 0.1 M acetic acid solution decreased progressively as the temperature increased from 4 to 52 °C, indicating thermal destabilisation or denaturation of PSC molecules. All PSCs were soluble in the pH range of 1–6 and sharply decreased at neutral pH. Decreases in solubility were observed in the presence of NaCl, especially at concentrations above 2% (w/v). Therefore, the skin of unicorn leatherjacket could serve as a potential source of collagen.

Spermatozoon ultrastructure of Aponurus laguncula (Digenea: Lecithasteridae), a parasite of Aluterus monoceros (Pisces: Teleostei)

The mature spermatozoon of Aponurus laguncula, a parasite of the unicorn leatherjacket Aluterus monoceros, was studied by transmission electron microscopy. The spermatozoon possesses 2 axonemes of the 9 + “1” trepaxonematan pattern, attachment zones, a nucleus, a mitochondrion, external ornamentation of the plasma membrane and cortical microtubules. The major features are the presence of: 1) external ornamentation in the anterior part of the spermatozoon not associated with cortical microtubules; 2) one mitochondrion; and 3) cortical microtubules arranged as a single field in the ventral side. The maximum number of microtubules is in the nuclear region. The extremities of the axonemes are characterized by the disappearance of the central core and the presence of microtubule doublets or singlets. This study is the first undertaken with a member of the Lecithasteridae and exemplifies the sperm ultrastructure for the superfamily Hemiuroidea.

First record of the unicorn leatherjacket Aluterus monoceros (Pisces: Monacanthidae) from the Mediterranean Sea

In March 2000 a 384 mm SL adult male specimen of the unicorn leatherjacket Aluterus monoceros was captured off the Chafarinas Islands (south-western Mediterranean). This report increases the list of fish species recently found for the first time in the Mediterranean Sea.

한국 거문도연안 세라믹어초어장에서의 홑자망과 삼중자망에 의한 어획성능

홑자망과 삼중자망에 의한 어획성능을 파악하기 위하여 한국 남해안의 거문도연안에 시설된 세라믹 어초어장에서 어구 성능시험과 수중 비디오 카메라로 어군 위집상을 조사로 하였다. 흩자망에 의한 폭당 어획량은 삼중자망에 비해 49.2% 많았으나, 어종수는 34.5% 적었는데, 이를 ANOVA로 분석한 결과 5% 유의수준에서 차이가 없었다. 어구별 우점종은 홑자망에서 참돔 1종, 삼중자망에서 참돔, 말쥐치, 홍어 등 3종이었으며, 홑자망에의해 어획된 참돔의 체장범위와 평균체장은 삼중자망에 어획된 참돔보다 다소 적게 나타났다. 홑자망에 의한 어획성능이 삼중자망보다 높았던 원인은 홑자망에 어획되기 쉬운 어종이 군을 형성하고 있었고, 개체의 크기도 홑자망에 적합하였기 때문이라고 판단된다. It has been, in general, known that the catching efficiency of a trammel net is better than that of a gill net because of the variability of catch species and size. In this stidy, A fishing gear test was carried out to analyze the catching efficiency of the gill net and the trammel net on the coast of Geomun-do of southern Korean waters and fish school aggregation was also investigated using a underwater video camera. CPUE of the gill net was 49.2% higher than the trammel net but fish species was 34.5% lower where there was no difference on the significance level of 5% by ANOVA test. Main catch species caught by the gill net were red seabream(Pagrus major) and triggerfish(Aluterus monoceros), skate ray(Raja Kenojei) and red seabream for the trammel net, and the average body length of red seabream was shorter than the trammel net. It was thought that the reason of higher catch in the gill net than the trammel net was a fish school which can be caught easily by gill net and the size of population was suitable for the gill net.

Changes in the Euro‐Atlantic fish species composition resulting from fishing and ocean warming

Studies of actual ichtyological biodiversity in the European Atlantic Ocean and estimation of changes in the relative abundance of fish species in catches off Arcachon, on the shelf and in the Bassin d'Arcachon, from 1727 to the present day are made. These show that some previously dominant species are now rare. Several disappeared to the south of the Bay of Biscay, such as the bottom‐living elasmobranchs with low reproduction rates (Echinorhinus brucus, Squatina squatina, Raja batis, R. brachyura, R. clavata, Dasyatis pastinaca, Myliobatis aquila, Galeorhinus galeus, Mustelus asterias), and teleostean fishes Trigla lyra and Eutrigla gurnardus. Overfishing with most fishing gears, but especially bottom trawls is responsible for their reduction. An additional study was made on tropical species which were not recorded before 1950 to the north of Portugal. The species include Zenopsis conchifer, Cyttopsis roseus, Chaunax spp., Sphoeroides pacbygaster. Tarpon atlanticus, Seriola rivoliana, S. dumerili, S. carpenteri, Lichia amia, Pomatomus saltator, Aluterus monoceros, Pisodonophis semicinctus, Lamprogrammus niger. Northward extensions in the distribution in Euro‐Atlantic sea waters of tropical fish are compared with results obtained in other regions of the South French Atlantic continental shelf. Ichthyological observations support previous results: 68.3% of the new records were fished on upper slope (200 to 600 m); 19.5% from the continental shelf (0 to 200 m). Among them, some 66.7% of captures from the south of the Bay of Biscay; 12.2% of the new records were found in the middle slope (900 to 1100 m). These results confirm the following: (1) a northern extension of tropical fishes on the upper slope in the south of Portugal has increased since 1963, and while it began in 1969 on the continental shelf, only increased from 1981; (2) the rate of colonisation of new‐comers was low for several species. About 30 years have passed between the record of Zenopsis conchifer and that of Cyttopsis roseus from off Portugal and northwestern Ireland, but only 5 years in the case of Sphoeroides pacbygaster, and (3) the northward expansion is evident to 52°00'N for continental shelf species, to 55°30'N for upper slope, and to 60°00'N for mid‐slope species.