NMFRI Gdynia Aquarium

Akwarium Gdyńskie

Porcupine puffer

Order: Tetraodontiformes

Family: Diodontidae

Diodon holocanthus

This species has a wide range of occurrence concentrated on tropical and subtropical waters. Its range in the Pacific Ocean covers coastal waters from California to Columbia, the Galapagos Islands, Hawaii, Easter Islands and the area from southern Japan to Lord Howe Island. In the Atlantic, it is found from Florida to Brazil, including the Bahamas, and also in the eastern Atlantic between 30 ° N and 23 ° S, including around South Africa. In addition, it occurs in the West Indian Ocean from the Red Sea to Madagascar, in Mauritius and the island of Reunion. Adults are associated with the bottom at a depth of 2 to 100 m. They prefer the bottom covered with vegetation, lagoons, coral and rocky reefs, as well as the dim bottom near the mangrove trees. Juveniles are pelagic. Unlike adults, which are loners, juveniles form large schools. When they reach a length of 7 cm, they change the habitat and descend near the bottom.

The Porcupine puffer is active during the night and hides during the day. It grows up to 50 cm long (usually 35 cm). Its characteristic feature is the presence of scales transformed into spikes that are used for defense and arranged along the body. This fish moves slowly using the pectoral, anal and dorsal fins, the caudal fin acts as a rudder. Her bright body is covered with large, dark spots located on the sides of the body and on the back, which dominate in the coloring of the fish. Between them, small black spots are visible, which, unlike D. hystrix, do not extend to the fins. The vertical brown stripe above and below each eye is characteristic. Juveniles are from olive to brown with dark spots, which is to mask them among the vegetation.

Thanks to its strong jaws and teeth, the Porcupine puffer specializes in eating hard invertebrates such as sea urchins, mussels and snails and crabs. Pocked teeth can catch and crush prey, while large, gummy lips protect against injury from spikes and broken crusts.

Puffers are dioecious (meaning the male and female reproductive organs are always present in separate individuals). Fertilization usually occurs at dawn or dusk. Then the male gently pushes the female towards the water surface. Fertilization is external. The eggs released by the female are immediately fertilized by the semen of even a few males. The larva is planktonic, parents do not take care of the offspring. The body of the larva is yellow with distributed red spots. Just 10 days after hatching, the spikes appear on the body of larvae. After three weeks, larvae transforms into a juvenile with an olive or brown body, characteristic of mature individuals. Despite the presence of spikes on her body, it is consumed by large predatory fish, primarily by tuna and dolphins. Mature individuals fall prey to sharks. Although other representatives of the puffers are used in Asian cuisine, D. holocanthus is not widely consumed. Dried and inflated, they are sold as souvenirs. They are also used in Asian folk medicine.

Defending tactics

When the fish feels threatened, it pumps its body swallowing water. In this way, it gains a larger volume, additionally raises the spikes, which discourage predators from attacking. Its body coating is very flexible, allowing the body to expand by up to 40% from its original size. When the threat passes, excess water is excreted and the fish returns to normal size. In addition, this fish accumulates in its body a toxin – tetrodotoxin, which affects the nervous system.

2020-05-28
Sunflower sea star

Order: Forcipulatida

Family: Asteriidae

Pycnopodia helianthoides

Starfish (Asteroidea), like sea urchins, sea cucumbers, ophiuroids and crinoids belong to the phylum of echinoderms, i.e. animals characterized by a radial body symmetry. The Sunflower sea star is the only representative of the genus Pycnopodia occurring only in the northeastern part of the Pacific. Before 2013, it was commonly found in the area ranging from the Aleutian Islands in Alaska to San Diego, California. It prefers a tidal zone with sandy, muddy, gravel as well as rocky bottoms. It also lives among meadows of underwater vegetation. The body of this starfish is fleshy and requires constant contact with water, so in the event of a high outflow it will move into deeper areas. Most often it occurs up to a depth of 120m, although it was also observed at a depth of 435 m.

It is one of the largest and heaviest starfish in the world. The maximum span of its arms is about 1m (usually 80 cm), and the weight reaches 5 kg. It also has the highest number of arms, ranging from 16 to 24, while most starfishes have 5 to 14. It is also the fastest starfish. It can move at a speed of 3m per min. and cover a distance of at least 3km. Over 15 000 ambulacral feet are used for movement. They are ended with suction cups that allow an animal to stick to the rocks. The body can have different colors, i.a. yellow, light orange and red to brown, and sometimes purple.

This animal leads a solitary life. It is a predator which uses a strong sense of smell and receptors that are very sensitive to light in order to gain prey. Its mouth is at the bottom of the body. It mainly feeds on sea urchins. This diet is supplemented with algae, sponges, mussels, snails, sea cucumbers, other starfish, crustaceans and fish. Diet varies depending on geographical location and food availability. By eating sea urchins, it regulates the structure of the bottom communities.

It is a gonochoric species, but there is no clear sexual dimorphism. Fertilization is external and random, individuals release gametes directly into the water. The larva is planktonic and feeds on phytoplankton. After a few weeks, it settles at the bottom and transforms into a young individual that feeds on plants. The young starfish has 5 arms. With age, more arms grow in pairs on both sides. Each new pair is inserted between the last pair created and the adjacent original arms. Juveniles fall prey to predators such as big fish, king crabs and otters.

When threatened, it may throw away a part of its body and move away from a danger.

It also releases a chemical substance into the water that alerts other individuals of the danger. After some time, the lost arm will grow back. If the detached arm had a fragment of the central body part, a completely new individual will grow out of it. This is a regeneration phenomenon. Regeneration is also a form of asexual reproduction in these animals.

What happened in 2013?

In the years 2013–2015, the number of this species dropped due to the sea star wasting disease and the increased water temperature caused by global climate change. The species disappeared from habitats off the coast of California and Oregon, and its population decreased by 99.2% in waters near Washington State. In 2016, a team of environmentalists studying the area of 3,000 km found a decrease in the population of the Sunflower sea star by 80-100% compared to 2013.

2020-05-25
The exhibition opened once again!
We are pleased to announce that from Friday, May 22, the Gdynia Aquarium can be visited again by external guests.

At May 22, we are coming back to present the beauty of the underwater world. At the same time, we want to ensure the safety of all guests, employees of companies we work with, as well as our team. Therefore, we had to modify the rules of visiting and buying tickets.

Due to the epidemic situation, admission to the exhibition takes place at designated hours: 9:00 am; 9:45; 10:30; 11:15; 24:00; 12:45; 13:30; 14:15; 15:00; 15:45; 16:30; 17:15; 18:00; 18:45. A ticket purchased for one of the above dates authorizes access to the facility within 30 minutes of the selected admission time. Due to the above restrictions, in the event of greater interest in visiting the Gdynia Aquarium, the waiting time for entering the facility may be extended.

The rules for visiting and selling tickets change from July 1.The limit of people staying at the same time is increased to 350, while the limited sale of tickets for specific hours is lifted.
- We recommend buying tickets online. Tickets can be purchased at sklep.akwarium.gdynia.pl 30 days in advance, choosing a specific time to enter the exhibition. Internet tickets are available no later than the day before the scheduled visit. This means that if you would like to visit the aquarium on the day you decide to do so, you will be able to buy tickets only at the ticket office of the Aquarium. In this case, one should be aware of the fact that they may simply be missing.
- If you buy tickets at the Aquarium ticket office, we recommend card payment. Please do not exceed the designated lines when making the purchase.
- A maximum of 200 people can be at the exhibits at one time. Some rooms, elevators and toilets are subject to specific limits that must also be followed.
- For the duration of restrictions related to the threat of coronavirus infection, we suspend the possibility of visiting the Gdynia Aquarium by organized groups. By organized group, we mean persons who jointly participate in an organized trip, e.g. by educational and care facilities, school and care facilities, travel agencies, workplaces, organizations, etc., constituting one entity for the service provider.
- In the entire building of the Gdynia Aquarium, it is mandatory to cover the nose and mouth.It does not apply only to children under 4 years of age. Persons who will not comply with this provision will not be able to enter the AG. By covering your mouth and nose, we protect others. Please show care for your fellow visitors. Exposing the mouth and nose during the tour will result in asking to leave the Aquarium building (not applicable to the food court on the Aquarium terrace).
- After entering the Gdynia Aquarium, you should disinfect your hands with fluid that is available at the entrance gates.
- Please do not touch the display elements, including the tank windows, and refrain from placing your hands in open display tanks
  For the sake of others and ourselves, let’s keep at least a 2-meter social distance.
We encourage you to read the full tour regulations, which are available here (updated on June 04,2020).

VISITING RULES

Thank you for your understanding and see you at the Gdynia Aquarium!
2020-05-21
Sea cucumbers

phylum: Echinodermata

class: Holothuroidea

Sea cucumbers

At first glance, the sea cucumbers are not reminiscent of other representatives of the echinoderms, whose characteristic five-ray symmetry is lost in sea cucumbers to varying degrees. In some species central symmetry is visible through five “rays” extending from the mouth to the anus. In these rays pseudopodia (ambulacral legs) are located, i.e. the endings of the water system, which serve for locomotion, food tracking and attach an animal to the surface.

The appearance of their body also differs from the appearance of other echinoderms, the mouth of which is located on the abdominal side, and the anal on the dorsal side. The body is elongated, bilaterally symmetrical, and their mouth and rectal opening are located at two opposite ends. The body has a ventral side (trivium) with three rows of ambulacral feet and a dorsal side (bivium) with two rows of pseudopodia.

Due to their body shape, they are called sea cucumbers, although the shape may vary depending on the species from almost circular, through a sausage-like or serpentine caterpillar.

They usually measure from 10 to 30 cm, but in extreme cases they are a few mm or over 3 m long. They do not have an outer skeleton, instead they have calcified structures reduced to microscopic cubes connected with connective tissue just under the skin. In some species these structures may have the form of flattened plates forming armor, while in some species the internal skeleton does not occur at all, e.g. in Palagothuria natatrix. Collagen tissues are also built into the body, which can change their mechanical properties, thanks to which the animal, by softening them, can squeeze through a small gap. However, to ensure safety, collagen fibers are shortened, then the body becomes firmer. This process is controlled by the nervous system and coordinated with muscle activity.

These animals are associated with the seabed and are spread all over the world, but most of them occur in the Asia-Pacific region. It is estimated that among the 7 orders, containing 30 families, there are 1717 species of the sea cucumbers. Many of them are collected for human consumption. They play a useful role in the marine ecosystem because they help clean the bottom of decaying organic residues and fertilize bottom sediment. They form flocks that move across the bottom in search of food.

Their mouth is surrounded by a crown of 8-30 tentacles, which can be straight, feathered, branched or branched and are used for feeding. The tentacles are modified ambulacral feet that can be hidden inside the mouth. Their appearance is one of the ways to identify particular orders. Identification of various species is also based on the appearance of limestone cubes embedded in the body walls. A significant part of the skeleton is a ring formed of ten limestone plaques surrounding the larynx. It is the attachment for the muscles that hide the tentacles, as well as for the main muscles of the body wall. Their digestive system is very simple. Many species have the esophagus and stomach, but for some, the throat opens directly into the intestine, which is usually long, curled, and passes through the body three times before it ends in the cloaca or directly as a rectum.

Sea cucumbers do not have distinct sense organs, despite the fact that various nerve endings are scattered on the skin providing sensitivity, also to the presence of light. There are also tree-shaped breathing channels that open into the cloaca. To breathe, an animal draws water with oxygen through the anus and then expels it. Together with the intestines, they also act as excretory organs.

In addition to the water system responsible for the movement of the ambulacral feet, they have a blood circulatory system.

The blood vessels are connected by over 100 small muscle ampoules that act as miniature hearts.

Due to the presence of white blood cells containing hemoglobin, their blood is red. Sea cucumbers are found in large quantities on the deep seabed, where they often make up the majority of animal biomass. They are the best adapted echinoderms to extreme depths. They vary greatly even at depths exceeding 5000 m. Moreover, at depths exceeding 9 km they account for 90% of the total biomass of macrofauna. The body of some deep-sea species, such as Enypniastes eximia, Peniagone leander and Paelopatides confundens, is built of hard, gelatinous tissue with unique properties that allow animals to control their own buoyancy, allowing them to move across the ocean floor, float or swim actively. Additional appendages on the body, e.g. resembling an umbrella, help them in swimming. Only one species, Pelagothuria natatrix, is typically pelagic because it never approaches the bottom. Sea cucumbers are scavengers. Their diet consists of plankton and decaying organic matter. In search of food, they sift the bottom sediment with the help of tentacles surrounding the mouth. 40 animals per square meter can process 19 kg of sludge per year. Some animals expose their tentacles towards sea currents and grab food directly from the water. The shape of the tentacles is adapted to the diet and size of the particles consumed.

Mostly they are gonochoric species, with the reproductive system consisting of a single gonada which opens at the dorsal side of the animal, close to the mouth. Most sea cucumbers reproduce by releasing semen and ova directly into the water. In some species, e.g. Pseudocnella insolens, internal fertilization occurs. The fertilized zygote is transferred with one of the tentacles to a pocket located on the body of an adult, where it develops and eventually hatches as a young sea cucumber. It is known that several species give birth to their young in the body cavity through a small crack in the body wall near the anus.

Many small animals can live in symbiosis with sea cucumbers. Some cleaning shrimps, in particular Periclimenes imperator, live on the body of sea cucumbers. Also, pearlfish is a commensal of cucumbers.

Fry hides in a sea cucumber cloaka, which becomes a shelter from predators, in addition, the nutrients found in the cloaka are the source of nutrtion.

Some species of polychaetes and crabs living inside the sea cucumber protect its mouth or breathing ducts. Not every species hosts free passengers, and so representatives of the Actinopyga genus have anal teeth that prevent visitors from penetrating it. As a rule, these animals have no enemies. They are ignored by predators because of the toxins they contain. Nevertheless, the molluscs of the species Tonna galea and Perdix tonna can paralyze sea cucumbers with a strong poison, and then swallow them. Some sea cucumbers defend themselves by expelling sticky tubules that stick to the predator.

In case of danger, they remove part of their internal organs through the anus, including sticky tubules, which are food for the predator.

Sometimes the removal of internal organs is also accompanied by the release of poison outside, which can kill other animals nearby. Removed internal organs regenerate within a few weeks.

Sea cucumbers play an important commercial role. They are consumed by people in various forms. They are also widely used in folk medicine, as well as in the pharmaceutical industry for the production of cosmetics and medicines, including those for joints. It is suggested that sea cucumbers can be used to treat cancer and malaria. Unfortunately, due to the high use of these animals, they are caught, both legally and illegally. They are also increasingly grown in aquaculture. Their popularity as luxury seafood in East Asian countries poses a serious threat to their population.

2020-05-15
Ocellate river stingray

Order: Myliobatiformes

Family: Potamotrygonidae

Potamotrygon motoro

This is one of seven species of the genus Potamotrygon inhabiting the southern part of South America. It is most commonly found in the Parana Basin, specifically in the midwestern part of Brazil, and can also be found in the Amazon, Uruguay, and Orinoco Basins. It prefers calm waters with a sandy base, especially streams and lagoons, and stays still during the day, buried in sandy sediments. It is closely associated with the base of rivers, so the depth at which it can be found depends on the depth of the river. In the upper Parana River, it occurs at depths of 0.5-2.5 meters, whereas in the Uruguay River, it occurs at depths of 7 to 10 meters. This cartilaginous fish defends its territory and leads a solitary life, undergoing migrations of unknown purpose that can cover more than 100 km. The information about its lifespan in the wild is unavailable, but in captivity it can reach the age of 15 years.

It uses its sense of smell during hunting, and electroreceptors (ampullae of Lorenzini) are also helpful because they detect electric stimuli produced by organisms buried in the sand. The type of food it eats depends on age and habitat, with juveniles eating plankton and later expanding their diet to include mollusks, crustaceans, and aquatic insect larvae. Adults consume mainly fish and crustaceans.

The coloration of the animals also depends on the habitat. The dorsal side is beige, brown, or gray and has yellow-orange spots surrounded by black rings. The ventral side is light in color. Its flattened dorsal-ventral body has an oval shape with a robust tail that bears two venomous spines used for protection. The maximum length is 1 m with the shield being 50 cm wide and weight going up to even 35 kg, although usually they are smaller (60 cm long and 10 kg). The mouth is located on the ventral side, whereas the eyes are on the dorsal side of the head, which gives them a nearly 360° field of vision.

Around the time of mating, the lips of the female’s cloaca become swollen and bloody, presumably from copulation (this may have given rise to the folk notion that female stingrays menstruate).

This species exhibits polygyny, which means that one male can copulate with many females. At the beginning the eggs have the diameter of around 30 mm. During development their nutrition comes not only from gall bladder but also directly from the female’s womb. The secretion from the womb is rich in nutrients and it helps them develop way better compared to receiving nutrition from the gall bladder alone. Gestation lasts approximately 6 months and birthing usually takes place in the rainy season. From 3-21 pups may be born in a brood and the number of young in a brood is always odd. The younger females always have smaller broods. Juveniles are approximately 10 cm long. They will reach their sexual maturity at the age of 3. If the pregnant female gets caught, it will abort its embryos. Reproduction follows a cycle in which one brood is birthed every year for three years in a row, followed by a several-year reproductive inactivity. This fish is caught due to its tasty meat. Juveniles are popular on the market and sold as ornamental fish. It has few predators in its natural habitat. They themselves play an important role in controlling insect populations through their diet.

How does the stingray move?

When the stingray moves in the depth of water, it looks as if it were levitating. It uses its wide and well-developed pectoral fins, which can be found along the fish’s body, for swimming. When it moves along the base of the water it uses its pelvic fins with which it pushes itself of the ground.

Below you can see the birth of stingrays in the Gdynia Aquarium.

2020-05-13
Banded houndshark

order: Carcharhiniformes (ground sharks)

family: Triakidae (houndsharks)

Triakis scyllium

This representative of cartilaginous fish inhabits the northwestern Pacific Ocean from southern Siberia, through Japan, Korea and China, to Taiwan. It is associated with the bottom of continental shelves, from very shallow depths up to 150 m. It tolerates lower salinity, which is why it is often found in estuaries and shallow bays, especially in sandy and vegetated areas, including seagrass medows. This medium-sized shark species grows up to 1.5 m in length. Males live 15 years, females 18. They lead a nocturnal life. During the day they look for hiding places, including in the caves.

The Banded houndshark is a solitary species, but sometimes it rests in groups of several individuals lying on top of each other. Its food preferences change with age. Also, the larger the shark, the more varied its diet. The basis of the diet of young individuals are various fish. Mature sharks feed on benthic invertebrates such as sea bream, crustaceans (e.g. shrimps, crabs and mantis prawns), as well as cephalopods, including octopuses. Less often they eat polychaetes, tunicates and small bottom fish such as flatfish, conger eels and herring.

The body of this species has a gray color on the dorsal part and a bright belly. In juveniles, darker stripes and dots are visible on the back, which fade with age. Its mouth is short, wide and rounded. Horizontally-oval eyes are placed high on the head. The mouth opening forms a short, wide arch and has long furrows in the corners that extend to both jaws. It has two dorsal fins, with the second one being slightly smaller. The caudal fin has a well developed lower lobe and a prominent notch near the top of the upper lobe. In juveniles, the lower lobe of the caudal fin is much less pronounced. Reproduction occurs in late summer.

Courtship is brutal, the male swims parallel to the female and grabs her with teeth by the pectoral fin. Then she twists her body so that copulation is possible.

It is an egg-bearing species, which means that the female produces eggs, but they remain in her body until the juveniles are ready to hatch. The female produces from 9 to 26 eggs, although batches as large as 42 young are also possible. Incubation lasts from 9 to 12 months. Juveniles are 18-20 cm long after hatching. Males reach maturity at the age of 5-6 years at a length of 93-106 cm, while females mature at the age of 6-7 years, when they are 106-107 cm long. The Banded houndshark does not pose a threat to people and adapts well to life in captivity. It is sometimes fished as by-catch (organisms accidentally entering the net), but its meat is not commonly consumed.

Sharks – hope for human health

Triakis is a typical cartilaginous fish. Due to its position in the process of evolution, both Banded houndshark and other shark species are used as genetic model species. Already in the 1970s, several biological substances derived from sharks were used in medicines or food additives. These included shark liver squalene, which was used in medicine and cosmetics, as well as shark cartilage extract, which strengthens bones and joints. For decades, more bioactive substances or biomaterials derived from sharks have been sought after, which is be useful in both medicine and industry.

2020-05-12