Pterois volitansRed firefish

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Geographic Range

Native Range:

Indo-Pacific: western Australia and Malaysia to the Marquesas Islands and Oeno; north to southern Japan and southern Korea; south to Lord Howe, Kermadec, and Austral Island ( map of the indigenous occurrances of Pterois volitans).

Nonnative Range:

Pterois volitans was introduced to Key Biscayne, Florida when a beachside aquarium broke during Hurricane Andrew in 1992. Furthermore, the intentional release of aquarium pets has contributed to the Florida population (USGS, 1999). It is not know what the biological implications of this introduction might be ( map showing the nonindigenous occurrences of Pterois volitans).

Habitat

Lionfish are primarily reef associated but also found in warm, marine water of the tropics (Grant, 1999). They tend to glide along the rocks and coral during the night and hide out in caves and crevices during the day.

Physical Description

The lionfish has a beautifully banded head and body with reddish or golden brown bands stretching across a yellow background. The dorsal and anal fins possess dark rows of spots on a clear background.

Pterois volitans are differentiated from other scorpionfishes by having 13 rather than 12 poisonous dorsal spines and 14 long, feather-like pectoral rays. The anal fin has 3 spines and 6-7 rays.

Pterois volitans can grow to a maximum length of 38 cm.

Some other noteworthy characteristics of Pterois volitans are the bony ridge across the cheek and the flaps that partially cover both the eyes and nose. They also possess a "tentacle" above both eyes.

Reproduction

Only while courting will Pterois volitans aggregate with other individuals. In this special case, one male will aggregate with several females to form groups of 3-8 fish.

When lionfish are ready to reproduce, the physical differences between the sexes become more obvious. Males turn darker and are more uniformly colored (their stripes are not as apparent). Females with ripening eggs become paler. Their belly, pharyngeal region, and mouth become silvery white. Such females are easy for the males to spot in the darkness.

Courtship begins just before dark and is always initiated by the males. After the male searches out a female, he rests next to her on the substrate and looks toward the water surface while propping himself up on his ventral fins. He then proceeds to circle the female. After circling several times, the male then ascends to the water surface with the female following behind. While ascending the female will tremble her pectoral fins. The couple may descend and ascend several times before spawning. On the final ascent the couple will swim around just under the surface of the water. The female will then release her spawn. These spawn are comprised of two hollow mucus tubes that float just below the surface upon release. After approximately 15 minutes, these tubes fill up with seawater and become oval balls 2 to 5 cm in diameter. Within these mucosal balls lie 1-2 layers of individual eggs. The number of eggs per ball varies from 2,000 to 15,000. As the female spawn are released, the male releases his sperm, which penetrate the mucosal balls and fertilize the eggs inside.

Twelve hours after fertilization the embryo begins to form. Only 18 hours after fertilization, the head and eyes become moderately developed. Eventually, invading microbes deteriorate the mucus walls and 36 hours after fertilization, the larvae hatch. Four days after conception, the larvae are already good swimmers and are able to begin feeding on small ciliates (Fishelson, 1975).

Lifespan/Longevity

Behavior

These nocturnal fishes move about in the darkness by slowly undulating the soft rays of the dorsal and anal fins. Although most of the lionfish's' feeding is completed within the first hour of night, it will remain out in the open until day. When the sun comes up, they retreat to their shadowy homes among the coral and rocks.

Pterois volitans live in small groups as juveniles and while mating. However, for the majority of their adult life they are solitary and will fiercely defend their home range against other individuals of both the same or different species using their poisonous dorsal spines. Male lionfish are more aggressive than females. While courting, males are particularly aggressive. When an invading male lionfish enters the territory of a courting male, the agitated male will approach the invader with widely spread fins. He will then swim back and forth in front of the intruder while pointing his poisonous dorsal spines forward. Next, the breeding male will sit face to face with the intruder and tremble its spines in a way similar to when it is feeding on invertebrates. The agitated male will then shake its head just before charging at the intruder in an attempt to bite the intruder's head. This violent biting can result in the intruder having parts of its mouth torn off. However, it can also result in the aggressor becoming impaled on the spines of the intruder. If the aggressor becomes impaled it is badly stung. Nonetheless, it shakes itself loose and continues to attack the intruder until it retreats (Fishelson, 1975). So the moral of the story is, "Do not mess with a courting male lionfish!"

Communication and Perception

Food Habits

Pterois volitans is one of the top levels of the food web in many coral reef environments. They are known to feed mostly on crustaceans (as well as other invertebrates) and small fishes, which include juveniles of their own species. Pterois volitans consumes an average of 8.2 times its body weight per year (USGS, 1999). As juveniles they consume 5.5-13.5 g per day and 14.6 g a day as adults.

Sunset is an optimal time for Pterois volitans to begin feeding because this is when activity in the coral reef is highest. At sunset, all of the day fish and invertebrates make their way to a resting spot for the night and all of the night fish come out to begin feeding. With all of these creatures around, the lionfish need not invest much energy to find a meal. They simply glide upwards along the rock and coral sneaking up on unexpecting prey from below. While moving slowly towards a small fish, Pterois volitans uses its open pectoral rays to shield the motion of its caudal fin. This shielding along with the cryptic coloration of the predator prevents the prey from becoming alarmed. Although we find the striped colorful pattern of the lionfish obvious and easy to see in an aquarium setting, in the coral reef this colorful pattern allows the fish to blend into the background of coral branches, feather-stars, and spiny sea urchins.

The lionfish attacks with one swift gulping motion that sucks the prey into its mouth. This attack is so quick and smooth that if the victim is among a group of fish, the other fish in the group may not even notice what happened. The lionfish can continue to hunt the other unaware members of the group.

Pterois volitans has also been known to hunt for fish in the open water near the surface with a different technique. Here they wait 20-30 cm below the surface and watch for small schools of fish leaping out of the water in an attempt to escape another predator. When they plunge back into the water the lionfish is waiting just below them ready to attack (Fishelson, 1975)

In addition to fish, Pterois volitans feed on invertebrates such as amphipods, isopods, and other crustaceans. The lionfish glides along the substrate (rocks or sand) and vibrates the rays on its fins in order the rustle the food out of hiding.

In general, the lionfish is stationary and feeds on as many fish as it can when fish are plentiful and then it fasts when food is scarce (Fishelson, 1997). When a lot of food is available for feeding, Pterois volitans becomes satiated or full and may not eat for at least 24 hours (Fishelson, 1997).

Lionfish invest most of their energy in growing to a large body size early in life. This tactic allows them to grow big at a fairly young age so that they are more likely to avoid attack by predators and increase their chances of mating successfully (Stearns and Crandall, 1984).

If a male lionfish meets another male while hunting, the more aggressive male will turn darker in color and point its poisonous, spiny dorsal fins at the other individual who usually folds down its pectoral fins and swims away.

Economic Importance for Humans: Positive

Pterois volitans is a popular aquarium fish. They are stripped from the wild to make money for the popular pet industry.

Economic Importance for Humans: Negative

None

Conservation Status

Pterois volitans is not currently listed as threatened or endangered. However, the increase in pollution in coral reefs is expected to kill many of the fish and crustaceans, which lionfish depend on. If lionfish are unable to adjust to these changes by selecting alternate food sources, it is expected that their populations will also decrease (Fishelson, 1997).

Other Comments

The pain of a lionfish sting delivered to a human can last for days and cause suffering, sweating and respiratory depression (Grant, 1999). Experimental evidence suggests that commercial stonefish antivenom does have some detoxifying affect on lionfish venom (Shiomi et al, 1989).

Contributors

William Fink (editor), University of Michigan-Ann Arbor.

Mahya Wood (author), University of Michigan-Ann Arbor.

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

tactile

uses touch to communicate

References

Fishelson, L. 1997. Experiments and observations on food consumption growth and starvation in Dendrochirus brachypterus and Pterois volitans (Pteroinae, Scorpaenidae). Environmental Biology of Fishes, 50: 391-403.

Fishelson, L. 1975. Ethology and reproduction of the pteroid fishes found in the Gulf of Aqaba (Red Sea) especially Dendrochirus brachypterus (Cuvier) Pteroidae (Teleostei). Publ. Stat. Zool. Napoli, 39: 635-656.

Fuller, P. 1999. "Nonindigenous Aquatic Species" (On-line). Accessed October 10. 2000 at http://nas.er.usgs.gov/fishes/accounts/scorpaen/pt_volit.html.

Grant, E. 1999. Guide to Fishes. Briskane, Queensland: The Department of Harbours and Marine.

Shiomi, K., M. Hosaka, S. Fujita, H. Yamanaka, T. Kikuchi. 1989. Venoms from six species of marine fish lethal and hemolytic activities and their neutralization by commercial stonefish antivenom. Marine Biology, 103(3): 285-290.

Shohei, S. 1986. Marine animals of the Indo-Pacific. Shin Nippon Kyoiku Tosho Co,. Ltd.