Thermosbaenaceans: Thermosbaenacea

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NO COMMON NAME (Thermosbaena mirabilis): SPECIES ACCOUNT


Adult thermosbaenaceans (ther-mohs-bee-NAY-cee-ans) are small, blind, and have slender bodies measuring up to 0.20 inches (5.2 millimeters). Their short head does not have a beaklike projection, or rostrum. They may or may not have eyestalks, but they never have eyes. The first pair of antennae (antennules) is branched, or biramous (BY-ray-mus). The second pair of antennae are uniramous (YU-neh-RAY-mus) or not branched. A short, shieldlike carapace covers the head and segmented thorax. The carapace of adult females has a large, bulging area that forms a brood chamber inside for storing eggs until they hatch. The first thoracic segment of both males and females is tightly joined, or fused, to the head.

The thorax has five to seven pairs of leglike biramous limbs called pereopods (PAIR-ee-oh-pawds). The pereopods are usually used for walking and sometimes swimming. The abdomen has six segments, but only the first two have appendages. The abdominal appendages, called pleopods (PLEE-oh-pawds), are well developed, narrow and rounded, or very small. At the end of the abdomen is a pair of slender biramous appendages, the uropods (YUR-oh-pawds). In between the uropods is a taillike segment called the telson. The telson in this species is not tightly joined with, or fused to, the last abdominal segment. The telson and uropods do not join together to form a fanlike tail.


Thermosbaenaceans are found in the North Atlantic Ocean, the Mediterranean Sea, and the southeastern Indian Ocean.


Most thermosbaenaceans live in underground springs or in caves with brackish waters. Brackish water is less salty than seawater. Others live along the seashore or in underground caves filled with seawater. A few species live in hot springs at temperatures of 111 to 118°F (44 to 48°C).


Thermosbaenaceans living in hot springs eat blue-green algae and other organisms growing underwater on rocks. Other species are thought to use their brushlike mouthparts to sweep up small plant particles off the bottom and into their mouths.


Thermosbaenaceans usually walk, but sometimes use their legs for swimming. Males and females are known, but mating has never been recorded. Thermosbaenaceans are unique among their crustacean relatives in that the eggs are kept in a brood pouch on their back formed by the swollen carapace. The young resemble the adults when they hatch. In one species, they hatch before the sixth and seventh pairs of legs are fully developed.


Thermosbaenaceans do not impact people or their activities.


Thermosbaena mirabilis only lives in two baths fed by hot springs at the oasis of El Hamma in southern Tunisia. They thrive in warm, slightly salty water at temperatures between 98.6 to 116.6°F (37 to 47°C). These heat-loving animals stop moving when the temperature dips down to a relatively "chilly" 95°F (35°C) and die at around 86°F (30°C).


No species of thermosbaenaceans is considered endangered or threatened.

NO COMMON NAME (Thermosbaena mirabilis): SPECIES ACCOUNT

Physical characteristics: The adult body is sort of cylinder-shaped and measures up to 0.14 inches (3.5 millimeters). The thorax has five pairs of biramous pereopods. The telson is large and is about as long as the last three abdominal segments combined.

Geographic range: This species is known to live in just a few hot springs in Tunisia.

Habitat: This species lives in hot springs with lots of dissolved minerals, at temperatures usually higher than 111°F (44°C).

Diet: Thermosbaena mirabilis eats several species of bacteria known as blue-green algae. Bacteria are one-celled organisms that break down wastes and tissues of other organisms.

Behavior and reproduction: They walk over the surfaces of rock in search of food. Hatching young resemble the adults and have five pairs of pereopods.

Thermosbaena mirabilis and people: This species is not known to impact people or their activities.

Conservation status: Thermosbaena mirabilis is not considered endangered or threatened. ∎



Schram, F. R. Crustacea. Oxford, U.K.: Oxford University Press, 1986.


Wagner, H. P. "A Monographic Review of the Thermosbaenacea (Crustacea: Peracarida)." Zoologische Verhandelingen 291 (1994): 1-338.

Web sites:

Thermosbaenaceans. (accessed on March 14, 2005).