NMFRI Gdynia Aquarium

Animals

Soft corals

Phylum: Cnidaria

Class: Anthozoa

Order: Alcyonacea (soft corals)

Alcyonacea are purely marine animals occurring only in the form of polyps. There are approximately 1,290 species of soft corals belonging to 6 suborders and 41 families. Representatives of this order are related to reef-forming (stony) corals, but lack the massive calcified skeleton of calcium carbonate. Instead, they have small limestone sclerites (fine spiky skeletal elements) in their bodies that provide some support and give their flesh a spiky, grainy texture that scares off predators. Several species, incl. blue coral (Heliopora) or pipe coral (Tubipora), have a solid skeleton, seemingly resembling hard corals. Moreover, their polyps always have 8 arms, unlike the stony coral polyps which have 6 or a multiple of 6.

Appearance

Soft corals are one of the most colorful and diverse groups of invertebrates found on coral reefs. They create colonies of various forms, incl. membranous, inlaid, massive, lobed, finger-shaped, woody, fan-shaped, bushy and whip-shaped. In the Caribbean, branching gorgonians and sea fans are the predominant forms of growth, while in the Pacific they are much more diverse, including fleshy corals as well as gorgonians. Although soft coral colonies do not contribute to reef growth, they provide shelter for many reef dwellers. Many animals, such as hydrophilic species, hydrozoans, bryozoans, crinoids, molluscs, crustaceans, and fish, find their shelter among corals, largely only on specific coral colonies. Many species of seahorses look similar to their hosts, thanks to which they perfectly camouflage themselves, eg. Hippocampus bargibanti inhabits only two species of the corals of genus Muricella and Hippocampus denise (fine seahorse) inhabits, i.a., colonies of corals of the genus Muricella, Anella and Echinogorgia.

Longevity

Soft corals include species with different biological characteristics and different ecological requirements. Many species are long-lived with a slow growth rate, while others are fast colonizers with a short life span. Some large colonies of the genus Sinularia (family Alcyoniidae) are probably hundreds of years old. The life expectancy and growth rate of most soft corals is largely unknown as colonies can shrink, due to both biological and physical factors, so there is a poor relationship between colony size and age.

Environment

Most soft corals, unlike stony corals, thrive in nutrient-rich waters with less intense light. Their food consists of small particles caught directly from the water column in the form of phytoplankton, fine particles of detritus, ciliates, flagellates and very small zooplankton. In addition, almost all of them use a symbiotic relationship with photosynthetic zooxanthella (alga) as their primary energy source. In return, the coral provides the algae with nutrients and shelter. This symbiosis depends on the availability of light for photosynthesis. There are taxa that do not bond with algae. Their only food is particles suspended in water, so they are highly dependent on water currents, therefore they occur in habitats with a large flow of water. They can be easily distinguished from those living in symbiosis with algae by their light yellow, orange, red, pink, purple or snow-white color.

Reproduction and colonisation

The dispersal strategies for soft corals vary between species, and include both asexual and sexual reproduction. Rapid colonization of small surfaces of the substrate is mainly related to asexual reproduction. It often involves the formation of stolons, the budding of miniature colonies which then fall off the parent colony and settle nearby, and fragmentation. Larger areas of the bare substrate are usually colonized by settling pelagic larvae formed by sexual reproduction. Then, mature individuals release their gametes into the water column, where fertilization takes place. The resulting pelagic larvae are scattered by currents over long distances. Once they reach the right size, they will settle down to days or weeks after conception. Fertilized eggs of some species remain attached to the mother colony, and the resulting larvae develop on the surface of the colony. After a few days it separates and settles to the bottom near the mother colony.

Diffence strategies

Many species protect themselves from predators, algae or contamination by neighboring organisms by releasing repellants, which are sometimes toxic. Many of these substances have been tested for their bioactivity, and some of them may become useful in the pharmaceutical industry. The main defense products are terpenoid in origin and despite their toxicity to fish, some specialized fish species are able to feed on corals. E.g. corals of the genus Sarcophyton sp. produce toxic sarcophytoxide, which released to aquatic environment causes reduction in the photosynthesis of the algae living in the symbiosis with coral Acropora formosa. Thus, it serves not only as a means of protection against being eaten by predators, but also provides an advantage in competing for living space with other corals. Sarcophytoxide, however, is not an obstacle for the gastropod Ovula ovum, which feeds on those corals and the toxin most probably is metabolised and detoxified in the intestines of the snail. Among the representatives of the gorgonias, such as the species Leptogorgia virgulata, there are substances such as lophotoxin. Their main task is to scare off the fish through stimulating vomits. In addition, they have antimicrobial properties, preventing coral overgrowth. Antarctic corals are protected either exclusively by limestone splinters or by chemicals. Eg., coral Ainigmaptilon antarcticus produces sesquiterpene that prevents starfish from feeding and inhibits development of the bacteria and diatoms. Separate strategy of the chemical defense can be observed in species Plexaura homomalla that produces large quantities of toxic prostaglandines and make the coral flesh untasty for, e.g., fish.

Significance

Soft corals are animals that produce many bioactive compounds with various effects, including antibacterial, antiviral, anticoagulant, antidepressant, antihypertensive, analgesic, anthelmintic, etc. Therefore, they are very commercially important. They are very easy to breed in captivity, much easier than hard corals that are susceptible to infection or damage. Soft corals grow quickly and are easy to divide into new individuals, therefore aquacultured corals are often more durable and cheaper than those imported from nature. Moreover, thanks to such farms it is possible to protect wild reefs. In the past it was believed that soft corals are not able to produce new fundaments for future coral reefs, however, recent discoveries suggest that the colonies of the genus Sinularia have an ability to cement their sclerites and fix them at the base, what makes them reef-building animals.

2020-11-05
Banded archerfish

Order: Perciformes
Rodzina: Toxotidae

Toxotes jaculatrix

This species is found in Indo-Pacific waters, from India, through Southeast Asia, Indonesia, Philippines, New Guinea to Australia. It tolerates changes in salinity, so it can be found in fresh, brackish and salt waters. However, it prefers the brackish waters of the mangrove forests, but also lives in small streams and rivers, as well as near vegetation on coral reefs.

It is a calm fish that lives in small flocks just below or near the surface of the water. If the fish is left without a group, it becomes aggressive towards other fish. The maximum length of the Banded archerfish’s body is 30 cm, however, they usually grow up to 25 cm. In captivity, they reach a smaller body size, about 16 cm and can live from 5 to 8 years, and sometimes even 10. Its body is oblong and raised from the back. The body is generally silver-white, although it may also be yellow. The back is green-olive or brown. The dorsal fin is yellow-green, the caudal fin is earthy green, and the anal fin is silver. On the sides of the body there are wide, black stripes (4 or 5), which shorten as the fish ages. Juveniles have a silver body with a yellow-green or brown back. The archerfish’s eyes are large and set so that he can look forward.

It is omnivorous, the basis of its diet are land insects, molluscs, crustaceans, small fish and plants. Actively hunts its prey by shooting insects on the vegetation above the water surface with a stream of water spewed from the mouth.

It can shoot an insect from a distance of 1.25 meters, and larger specimens are able to hit the victim from a distance of 2-3 meters. It is able to reach the victim within 50 milliseconds after it hits the water. It can also jump above the water and catch an insect on the fly.

It is a dioecious, oviparous animal with external fertilization. The first reproduction occurs when the animal is 10 cm long. During spawning, which takes place in November and December, the female lays between 20,000 and 150,000 eggs, with fertility closely related to the size of the female. They rarely reproduce in captivity. They plays insignificant role in commercial fishing, but are also caught as an aquarium fish.

Indian shooter – sniper fish

The archerfish can see a clear picture despite the different refractive index on the water-air interface. It does this through special adaptations in the eye with an extremely large retina on which the image focuses. This allows the fish to look through the water into the air without having to take into account the distortions in the spatial system, resulting from different refractive indexes, and give an accurate shot. Another possible way how a shooter deals with minimizing refractive indices is to position itself almost directly under its prey before the shot, then it sees the same picture he would see from the air.

The way it shoots its victim is also important, unfortunately it is not known in detail. It is known that a shooter is able to spit water by exerting pressure in the mouth. A stream of water is generated in a tube formed from the tongue hooked on the groove in the palate. Water is thrown out of the mouth by high pressure due to the contraction of the gill chamber. The length of the water stream shot by the fish can reach up to 3 meters.

2020-06-24
Copperband butterflyfish

Order: Perciformes

Family: Chaetodontidae

Chelmon rostratus

This species occurs from the Andaman Sea, through the Indo-Malay region, to Japan and the Great Barrier Reef in the Pacific Ocean. It inhabits coastal reefs, rocky shores and estuaries at depths from 1 to 25 m. The Copperband butterflyfish swims alone or in pairs. Juveniles are loners and inhabit shallow waters. It is an active fish, which swims freely, but also spends time hidden in cracks and crevices where it lies motionless. It is not aggressive, but will defend its territory against other representatives of the genus Chelmon. It reaches small dimensions, the maximum total length is 20 cm, while in captivity it is much smaller. The maximum reported age from the environment was 10 years, while in captivity it lives up to 4 years.

Its body has the shape of a shield with a long protruding muzzle ending with small snout. Its coloration is also characteristic, on the silvery-white body there are 4 vertical stripes in yellow or orange with black and white edges.

At the base of the dorsal fin is a false eye with a bluish-white circle. The dark eye of the fish is much smaller than the false eye.

Young individuals are similar to mature ones, only their false eye is larger in size and the stripes are more intense. It is a carnivore. It uses his long mouth to get food out of the cracks. Its diet is based on polychaetes, representatives of corals such as Aiptasia, molluscs and crustaceans. The Copperband butterflyfish is dioecious and monogamous. During spawning taking place just below the water surface, the female lays eggs, which are fertilized by the male. Fertilized eggs float along with currents in the water column. The larvae lead is planktonic.

Due to its attractive appearance, the pensetnik is a popular aquarium fish. Nevertheless, it is a fish that requires experience, because it is difficult to keep it alive in captivity. Individuals smaller than 14 cm are most often sold, juveniles not exceeding 3 cm in length are very rare. The Copperband butterflyfish is exported from the Philippines, Indonesia and Australia, while individuals caught in Australia are considered more adapted to life in captivity, which is why they achieve a double price. This is due to the methods of obtaining individuals from the natural environment.

Mimicry – a form of defense against predators.

The Copperband butterflyfish due to its small body size can easily fall victim to larger predators. Like other gentle fish, it has developed a false eye to mislead the opponent. The false eye, i.e. a colorful spot located on the dorsal fin, is a form of mimicry, i.e. similar to other dangerous animals. In the Copperband butterflyfish, the false eye, which is much larger than the real eye of the fish, is designed to mislead the predator as to the location of the fish’s head. In most cases, the predator attacks the head so that the victim has no chance of escape. If the predator considers the false eye, and thus the back of the fish’s body, as its head, such a fish has a chance to escape. A similar strategy is used by many species of marine fish, but also freshwater, such as the Oscar.

2020-06-24
Green spot mandarin

Order: Perciformes

Rodzina: Callionymidae

Synchiropus splendidus

This species is found in the tropical waters of the Indo-West Pacific, from the Philippines and Eastern Indonesia to Northern Australia. It is a bottom fish associated with coral reefs. He prefers coastal reefs and shallow lagoons with a sandy base, where he settles on sand or rocks, most often among coral branches, where he finds food and shelter. Occurs to a depth of 20 meters. This slow and shy fish is most often found in small groups or in pairs. It reaches a small body size, with a maximum length of 7 cm. Males are slightly larger than females.

The Green spot mandarin is distinguished by its unusual and intense color. The body is light green or olive and is decorated with a combination of black, orange and blue spots. The first ray of the dorsal fin is elongated in the male. The mandarin skin is covered with a thick layer of mucus, which has an unpleasant smell and a bitter taste. Its task is to inhibit many types of parasitic infections and minimize the risk of infection after physical injury. There is also a layer of cells on the skin that produce and release substances with some toxins. It is suspected that this secretion is used as a repellent to predators and other fish. Also, most likely, its bright coloration is supposed to inform predators that it is poisonous. Mandarin feeds during the day. Its diet consists mainly of copepods. In addition, it feeds on algae, plankton and small benthic invertebrates. It is a dioecious fish. Fertilization occurs when the male and female swim close together. Eggs and larvae are pelagic. When the larva reaches the appropriate developmental stage it settles to the bottom. This species breeds successfully in captivity. Due to its attractive coloration, it is a valuable aquarium fish. Fishing for mandarins as aquarium fish plays an important role in the local economies of the Philippines and Indonesia.

The Green spot mandarin – is this an optical illusion like in the case of the Regal blue tang?

The Green spot mandarin is one of two species of vertebrate whose blue color is due to the presence of cyanophores in the skin. Cyanophores are dye cells containing a blue dye. Cyanophores are also present in another representative of the mandarins – Synchiropus splendidus (magnificent mandarin). In other fish, the blue color is structural in nature and is a light phenomenon in which light-reflecting pigment cells (isidophores) participate.

2020-06-17
Red piranha

Order: Characiformes

Family: Serrasalmidae

Pygocentrus nattereri

This species of freshwater fish is common in South America, where it occurs in the rivers of Argentina, Brazil, Bolivia, Colombia, Ecuador, Guyana, Paraguay, Peru, Uruguay and Venezuela. It lives in the warm waters of several major rivers, such as the Amazon, Paraguay, Parana and Essequibo, as well as in many smaller ones. It prefers rivers rich in mineral substances that give the water a white color, only sporadically seen in rivers with a very low pH and high content of humic and fulvic acids, whose waters are black. The Red piranha inhabits coves, floodplains, lakes, streams and large rivers, up to a depth of 20 meters.

It grows up to a maximum length of 50 cm, but rarely exceeds 35 cm, and a maximum weight of 3.9 kg. It is characterized by a deep, laterally compressed body with long dorsal fins. The coloration varies depending on the geographical location and age of the fish. Mature individuals have a gray-silver body with a reddish-orange belly. The dorsal, anal and caudal fins are black, while the pectoral and abdominal fins are red-orange. Juveniles, on the other hand, have a silver body with dark spots, which disappear gradually as the fish grows.

It lives in groups of about 20-30 fish. Interestingly, they do not group to hunt for large victims collectively, but for protection against larger predators. However, provoked or starving, they can go into a feeding spree, then several groups of piranhas gather around the victim and eat it within a few minutes.

Such attacks are extremely rare. Despite the opinion of a dangerous predator, it is omnivorous. A typical diet of red piranha includes insects, molluscs, crustaceans and other fish, as well as plants and carrion. The feeding time varies depending on the size of the fish. Smaller fish search for food during the day, while larger ones feed at dawn and late afternoon and evening. Usually hunts waiting for prey hidden among the vegetation, but can also actively pursue prey. Its powerful teeth can cause serious bites.

The Red piranha is not a migratory species, but travels in search of conditions favorable for reproduction and spawning during periods of increased rainfall. It is a dioecious animal. The male can be distinguished from the female by the cross-sectional shape of the abdomen. In males it has the shape of the letter “V”, while in females “U”. In addition, the female belly has a slightly deeper shade of red. Piranha has two breeding seasons per year that are associated with water level fluctuations. When the individual is ready for sexual activity, it loses its red color and selects spawning habitat such as vegetation floodplains. This animal shows breeding behavior around nesting sites, then two different sexes swim side by side being in close contact with the abdominal sides. Initially, they were thought to be courtship, but this behavior was to defend the nest. The nests are about 4-5 cm deep, 15 cm in diameter and are dug among grass. The female lays up to 5000 eggs, which she sticks to the vegetation in the nest. After a few days of fertilization, how are young individuals hatching who seek shelter from predators among the vegetation. Juveniles will reach puberty after one year.

The Red piranha is considered one of the more dangerous and aggressive species of piranha, but it has developed a kind of symbiotic relationship with another piranha agent – Serrasalmus marginatus, which cleanses its body of parasites. It can be dangerous to people due to the risk of biting. It is the most commonly caught species of piranha used commercially as aquarium fish. Its fishing and trade as an aquarium animal can locally reduce the number of this species.

Fish and children don’t have a say – do they?

The Red piranhas can communicate with each other. Very often the issuing of sounds manifests itself along with aggressive behaviors, such as biting, racing or fighting. The sounds produced by piranhas are generated by muscle spasms and are associated with a swim bladder that serves as a resonator. When removed from the water, piranha makes a drumming-like sound. Three other types of sounds are made in the aquatic environment and vary in frequency and duration depending on the circumstances. They will be different when two individuals meet, before a fight or during a pursuit or just before a bite. Almost all sounds made by piranhas are produced in the context of social interaction. Low sound is usually produced during moderate attacks, while loud, high sounds are generated during more energetic attacks.

2020-06-17
Spiny lobster

Order: Decapoda
Family: Palinuridae

Palinurus elephas

This crustacean occurs along the northeastern Atlantic coast, from Norway to Morocco and the Azores, and in the Mediterranean, except at its eastern extremities. It prefers a rocky bottom and a coral substrate, where there are many holes and small caves in which it can hide during the day. It lives only in clean waters – the presence of spiny lobsters indicates a low degree of environmental pollution. The depth range at which it can be observed is 5-200 meters, however, it usually stays at a depth of 10 to 70 meters. It can live alone, in pairs or small groups.

The Spiny lobster can reach a maximum length of 50 cm, however, it is usually 25-30 cm, and can reach a weight of up to several kg. The maximum verified age of this animal was 15 years. To increase body size, the animal sheds old armor, in its place a new, larger one is created. During moulting, the animal is vulnerable and may more easily fall prey to predators. The Spiny lobster’s exoskeleton consists of two parts covering the cephalothorax (fused head and body segments) and the body is finished with a telson (tail). It has a red-brown color, additionally there are symmetrical white spots on the abdomen and telson. The abdominal side is white, although sometimes brown, sandy and purple discolorations. The head is covered with spikes pointing forward. The antennas are very long and massive with orange and white stripes. The first of five pairs of legs is equipped with small claws, and the remaining 4 pairs with sharp single claw at each leg. There are also legs under the abdomen, they are much shorter and are used for swimming and supporting eggs by the female.

The Spiny lobster is a night predator. It is omnivorous and its diet changes depending on the number of benthic organisms present in the foraging area. It feeds on macroalgae, bryozoans, polychaetes, crustaceans and carrion, however, molluscs and sea urchins are the most important element of her diet. In addition to the daily feeding cycle, these animals also have a monthly cycle associated with moonlight. One should not go fishing for the lobsters during the full moon, because the most intensive foraging of lobsters is during the new moon.

The Spiny lobster is a dioecious animal. During the mating season, interesting behavior can be observed, when the animals move one after other in a string.

Reproduction occurs once a year from June to October, with larger females breeding first, smaller ones later. The fertilization is internal and immediately after it the female lays eggs, which she sticks under the abdomen and cares for them until the larvae hatch (phyllosoma stage), i.e. for about 6 months. The larvae are leaf-shaped and planktonic. After some time, the larva settles on the rocky bottom and transforms into a juvenile individual, which reaches sexual maturity at a length of about 7-8 cm. The Spiny lobster is commonly caught for consumption and is a culinary delicacy, mainly in the Mediterranean. Traditionally they are trapped or collected manually, but these techniques have been replaced with trammels (fishing gear).

Can a lobster sense a threat?

Yes, a lobster can avoid areas where it senses a threat. An experiment was carried out in which crawfish were admitted into the tank with the octopus Octopus vulgaris. The lobster showed chemosensory behavior in response to the smell of octopus. She was able to detect the predator’s odor among others and avoid the place where the octopus was.

2020-06-16