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Shark Tales from the Mediterranean

January 1 2018
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Scientist within the National Geographic Society (Andrej, Adla and their team) working on the better understanding of the shark diseases across the Mediterranean sea, and beyond.


Learn with us which shark diseases are caused by different sort of pollution and how we can prevent them?!

January 1 2018

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Preparation Stage

Are there plastic in sharks ?!


I the last two years, our team put a lot of efforts in order to investigate the negative impact of microplastics and persistent organic pollutants (POPs) and heavy metals which often binds to the microplastic particles.

Microplastic comprise a very heterogeneous assemble of pieces that very in size, shape, color, specific density, polymer type, and other characteristics. For meaningful comparisons, it is important to define methodological criteria to quantity metrics like the abundance, distribution and composition of microplastics and to ensure sampling effort is sufficient to detect the effects of interest.

Its both disturbing and sorrowfully that we found over 120 different particles of the microplastics within the guts of adult fish no longer than 30 cm in total lenght. It truly time to stop this pollution ! if we ca not stop, lets mitigate it together, person by person - do not use plastic if you do not need to.

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Such an amazing structures


Finally, we have got our slides and we are ready to do some microscopy. Observed under light microscope with high magnification we can observe the fine structure of electric organ (up left), eye structure (up right) and spinal nerve roots which out of the spinal column (down left and right).

It is poorly known that many species of rays and skates have electric organs in the tail - but electric rays within the order Torpediniformes F. de Buen, 1926 has two large, kidney-alike, electric organs on each side of the head. In such case the current passes from the lower to the upper surface. Fascinating is that the organ is governed by specialized (electric) brain lobe, which is different color from the rest of the brain ! Besides, there are four central nerves on each side of the electric lobes. Plates are composed of hexagonal columns in a honeycomb formation. Each of those columns consist of 150.000 to 500.000 gelatinous plates. Which such organs, electric rays are capable to produce up to 30 amperes and a voltafe up to 220 volts.

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Dig even deeper


Have you ever wondered how does the electric organs look under the microscope ?! We do ! Not only the electric organs, but many other structures of the marbled electric ray, such as spinal nerves, eye, etc.

During the the classic pathological studies performed on the dead by-catch samples, this time sent from Mario Lovrić in Neum, we have decided to dig even deeper in order to understand the tissue structure of various organs.

At the dissection we have cut pieces approx. one square centimeter and were fixed in 10% neutral buffered formalin for 48 hours, then routinely processed and embedded in paraffin for cutting. The samples were sectioned at 4-5 μm, and stained with haematoxylin and eosin (HE).

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Sharkaholic, isn't he ?!


"I hang out with sharks both as my profession and my hobby" said Andrej just after he got out of the water from only God knows how long dive with hes double tanks at the back and two Nitrox stages.

Research diving is far different than the recreational one. We tend to use different equipment and often follow quite different rules, designed in order to achive "no-stress" both for divers and animals in the waters, provided that safety always come first !

It is not easy to carry 100 do 200 pounds of equipment, but it is definitely worth it !

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Lets hit the water again !


This time the Shark Tales team is in the extended edition with the friends from DC Bosna joined us in Žuljana, Peljašac peninsula (Croatia). Those coastal waters are quite famous during the summertime touristic season, but are they inhabited by any species of sharks, skates and/or rays - we are here to find out !

Our team, which consists of over 30 research divers have explored shallow coastal localities, as well as depths up to 50 meters all over the Žuljana. It is always super excited to be in the water and no to simply dive, but to use all our knowledge to track and find animals that we are looking for.

Adla, congratulation on your new obtained diving category !

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Take a look inside


X-rays have various application in the clinical trials. They are a type of radiation called electromagnetic waves which creates pictures of the inside of body. The images show the body parts in different shades of black and white - due to different tissues absorb different amounts of radiation. This shades help us to understand possible diseases.

Up right there is Common stingray, Dasyatis pastinaca (L.), then up left marbled electric ray, Torpedo marmorata Risso, 1810. Lower two images present a brown ray, Rala miraletus Linnaeus, 1758. All of the caught at by-catch within the small-scale fisheries in the Bosnia and Herzegovina.

Those skates and rays look absolutely astonishing on the inverted x-ray scans, dont you think ?!

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These are so beautiful!

Yes they really are ! No matter how much those scans we took, we are always super excited to see a new one and to learn more on those magnificent animals.

What does X-rays hide ?!


Back in the laboratories in Sarajevo, this time with some samples to work on !

Our team have collected some unfortunately already dead by-catch samples of common stingray, Dasyatis pastinaca (L.), brown ray, Raja miraletus L. and marbled electric ray, Torpedo marmorata Risso, 1810 from the Neum bay.

We have wondered about the possibility to use digital x-ray imaging in order to better understand the functional anatomy and possible diseases detection in our samples. So, that is precisely what we have done !

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Meet the electric ray


This fascinating rays prefers shallow waters from 10 to 30 m, although rarely found deeper than 200 m. It inhabits buddy bottom, seagrass beds, rocky reefs and sandy flats. Often survive in tidal pools and other environments with extremely low dissolved oxygen. Typically reach around 35 cm, but might grow over 61 cm in length.

Marbled electric rays posses paired, kidney-like, electric organs located on the ventral surface which are capable of producing 70 to 80 volts of electricity. Delivered electric shock can be severe but it nos directly life-threatening to humans. This species is aplacental viviparous, with the developing embryos sustained by yolk and histotroph produced by the mother.

"I used to play with two large electric rays in the shallow seagrass poll for almost two hours", said Andrej. Suddenly, he was almost lunched from the water, "Surely they got tired of playing", he added before taking this photo.

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Time to go out


Is there anything better to do at Friday night, except going all alone down to 30 m deep and dig the mud to hang out with some stingrays ?! We guess no !

Using technical diving equipment we aim to closely interact with skates and rays, to understand their behavior, interactions and their habitats in order to asset different treats to them. This field expedition combined Shark Tales team and the Rufford project regarding to the conservation of sharks in territorial waters in Neum bay, Bosnia and Herzegovina. The more different efforts we take, the results are more promising.

To conclude, not quite fun when you run out of gas in the engine couple of miles from the coast... oh yes - paddle guys !

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CD markers for leukocytes


Shatk Tales team go even deeper. We have decided to take some CD molecular markers useful for the identification and characterization of leukocytes.

What have we done and how ?!

Formalin-fixed, paraffin-embedded tissue was cut at 5 μm, dried overnight at 60°C and deparaffinized in xylene. Subsequently, the sections were rehydrated through graded alcohols into water. Heat-induced epitope retrieval was achieved by boiling sections in the EDTA buffer at pH 9 in the microwave oven at 1000 W for 20-30 min (4 × 5 min) dependent of antibody. After boiling, the sections were allowed to cool at room temperature for 20 - 30 min dependent of antibody, rinsed thoroughly with water and placed in Tris-buffered saline (TBS) for 5 min. Endogenous peroxidase was blocked with peroxidase block solution provided in the EnVison+® kit for 5 min and slides rinsed/washed with TBS. The visualization was performed using EnVision+® Appropriate positive and negative controls were used.

All five markers were negative, but (!) we have expected to see negative results because the differences of the mammalian and shark cells. Anyway, worth giving a shot and bring some extra details.

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Whats wrong with that liver ?!


Histopathology revelaed severe changes in the liver tissue ! Six observed samples contained several, mostly rounded, lesions located in the inner liver parenchyma around hepatocytes. No similar lesions have been observed within the liver connective tissue capsule of stroma, nor any other studied organ.

Observed multi-focal lesions within the liver parenchyma consist of mostly macrophages and lymphocytes, with some monocytes. Several eosinophils have been observed within the lesions, as well as within the healthy liver parenchyma.

First case report of such hepatitis observed in six specimens of lesser-spotted catsharks, Scyliorhinus canicula (L.), from the Adriatic sea is currently in press and waiting for publication.

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First insight into histology


There is a huge lack of data when it comes to the histology and pathology of sharks, skates and rays. Therefore, Shark Tales team decided to carefully examine over 25 different tissue parts.

At the dissection, the samples of each organ were collected for histopathology, and were fixed in 10% neutral buffered formalin for 48 hours, routinely processed and embedded in paraffin. The samples were sectioned at 4-5 μm, and stained with haematoxylin and eosin (HE) and periodic acid-Schiff (PAS).

We have described histology of brain, spinal cord, teeth and jaws, liver, pancreas, kidneys, esophagus, stomach, duodenum, ileum, rectum, rectal gland, ovary, oviduct, testis, skin and much more. Why dont you get in touch with our team if you are interested to learn more !

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Catsharks from Dubrovnik


The lesser-spotted catshark, Scyliorhinus canicula (L.), is one of the most abundant sharks of the Adriatic Sea. It inhabits the subtropical waters of the northwest Atlantic, including Mediterranean sea, usually between depths of 80 and 100 m, although it has been recorded from 10 do 780 m. Often found in schools segregated by size and sex, at different bottom types such as muddy, sandy, grassy or coraline. Grows up to 100 cm, although the common length is around 50 cm.

Our first sample originate from the trawl by-catch around Sv. Andrija island in Dubrovnik (Croatia) caught at approximately 80 m depth. Sometimes you need to perform the dissection off shore, without proper equipment - in order to preserve samples for further analysis. In the lab, we have conducted macroscopic pathology in order to detect possible changes in tissues. All examined sharks appeared in good body condition and no gross changes were observed. Now lets await for the histology !

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MEET THE TEAM


Shark Tales team primarily consist of National Geographic Explorers and research scientist from the Sharklab ADRIA, as well as many volunteers and contributors from numerous partner institutions. The team is coordinated by Andrej Gajić and Adla Kahrić, with board members Catarina Gennaro, Suvad Lelo and Hajrudin Beširović.

Andrej A. GAJIC is a National Geographic Explorer dedicated to the better understanding of the mechanisms of disease development in sharks, skates and rays, as well as their conservation. Through his so far work, Andrej have published over 70 scientific publications and two books, which are widely recognized, and he have coordinated over 30 research expeditions across the Europe, Middle East and North Africa. He is conducting various research in the fields of ecology, pathology, anatomy, odontology and genetics. Over the last ten years, his research have been funded by the National Geographic Society, Rufford Foundation, PADI Foundation, IDEA WILD and many others. Back in 2008. as a high-school student with a dream he have founded Sharklab International together with friend Greg Nowell (in Hamrun, Malta) - which is nowadays a recognized research institution working with departments across the globe. For his contributions in the fields of marine biology Andrej have been nominated/won numerous honors and awards, including the „Person of the Year 2014“ nomination.

Adla KAHRIĆ is National Geographic Explorer and current Vice president of the Sharklab ADRIA and working mostly on the ecology, pathology and genetics of the elasmobranch fish, with accent on batoid species from the eastern Adriatic sea. She have published over 50 scientific publications and currently is working on two books, while she participated at over 20 regional and international conferences and meetings. Adla have participated in numerous field expeditions in Europe and North Africa, while she lead filed studies across eastern Adriatic sea. As a dedicated scientist and conservationist Adla is currently working on the establishment of the first MPAs in Bosnia and Herzegovina through the protecting the highly endangered habitats and spawning sites of skates and rays in the Neum bay which is founded through ROC grant program by Waitt Foundation.

Catarina Gennaro is By the age 12, Caterina Gennaro was an accomplished gymnast; National Champion & member of U.S. Jr. Olympic Team. At 17, she began an equally impressive career in modeling with Ford Modeling agency in N.Y, appearing in National Commercials, Magazines, and later television, winning the New York Film Festival in 1990. She gained recognition as a Worldwide Research Diver, which led her to work with the National Marine Fisheries, Research Assistant for NOAA, which allowed her to receive a scholarship to University of HI for Marine ScienceWith over 2,000 logged dives to her credit and her affinity for marine life she became the first woman to free dive with Makos, and Great White Sharks. In 2001, Cat and colleague Jeff Kurr formed a company Shark Entertainment, Inc. Cat then had an opportunity to utilize her incredible variety of skills and talent in the production of the amazing Discovery Channel documentaries “Air Jaws” and “Air Jaws 2”. Her White shark experience, along with Makos, Great Hammerheads, Bull Sharks, Tiger Sharks, Lemons, and Cat is one of the first to film and photograph Six Gill Sharks. Cat’s work is featured in over 20 “Shark Week” documentaries and her photographs are displayed across the world in Magazine Covers, Many National News Papers, and over 30 published photojournalist articles to her credit, including Forbes, National Geographic, Ladies Home Journal, New York Times, Popular Photography, Chicago Tribune, LA Times, Scuba Diver magazine and Co-Writer of Field Guide to the Great White Shark:“ Tips for Filming Underwater, specializing in Great White Sharks”.

Suvad Lelo is full professor at the Department for biology, Faculty for scient and mathematics, primarily working on the biosystematics and taxonomy. He is author of over 300 widely recognized publications. As one of the highlight of hes rich career Suvad have published one and the only checklist of animals in Bosnia and Herzegovina, which contain over 11.019 registered species. Suvad has organizes and participated in several hundreds of field expeditions across Bosnia and Herzegovina, including the studies in Neum-Klek bay.

Hajrudin Beširović is full professor at the Department for pathology, Faculty of Veterinary Medicine with main interest in histopathology and immunohistochemistry. Through his numerous scientific papers and books he have learned many generations of veterinary doctors and biologist. He currently serve as a research scientist and adviser within the Shark Tales team. in the eastern Adriatic sea. Beside, Hajrudin have participated in dozen projects funded by Bosnian government, European Union and different non-governmental foundations.

Other team member include Ermina Memišević and Dalila Delić from Sharklab ADRIA, Md Muzammel Hossain from the Sharklab Bangladesh, Hrvoje Gavrančić from DC Bosna, Aleksandar Joksimović from the Institue for marine biology in Kotor (Montenegro), Branko Dragičević from the Institute for marine biology in Split (Croatia), Kenan Baltić and Amer Alić from the Faculty of Veterinary Medicine in Sarajevo (Bosnia and Herzegovina),Gregory Nowell from the Sharklab Malta and many other to name.

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Expedition Background

Back in 2015, a team of enthusiastic scientist from Sharklab ADRIA in Bosnia and Herzegovina and Malta wondered whether sharks in the Mediterranean suffer from a serious diseases. After over two years of their efforts, they found alarming results. Their studies have pointed out numerous pathological changes in the form of neoplasms, necrosis, various inflammations , as well as various parasites.


The SHARK TALES expedition is based on National Geographic project related to the pioneering studies of the pathology and ecology of the elasmobranchs of the Adriatic sea and beyond - with the emphasis on character, ecology and cause of outbreaks of specific diseases. Entire expedition consists of both field and laboratory studies.

While we regularly dive with sharks, skates and rays at the field – in the labs we are using a contemporary approach in pathology, histopathology, immunohistochemistry, axial tomography and digital X-ray imaging. Please notice that animals are NOT killed, harmed or sacrificed for the purposes of the research, pathological studies are conducted on already dead by-catch samples.

Entire expedition address two main questions „Which diseases in elasmobranchs are caused by the pollution and habitat destruction?!“ and „How to base the conservation and revitalization plans for the affected populations?!“. Precisely, this expedition will result in the very first original, adequate and detailed description of any pathological changes caused primary by pollution and habitat loss/destruction, and thus notes for long-term in-situ conservation and revitalization.

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Support for this team! Good job people!