Bonellia viridis
ORDER
Bonellioinea
FAMILY
Bonellidae
TAXONOMY
Bonellia viridis Rolando, 1821, Naples, Italy.
OTHER COMMON NAMES
English: Weenie worm; French: Bonnellie, bonnelie verte; Spanish: Gusano marino verde; Danish: Igelwurm.
PHYSICAL CHARACTERISTICS
Female's trunk ovoid to sausage shaped, and about 5.9 in (15 cm) long. Proboscis long and bifurcate at the end. When completely extended it can reach 4.9 ft (1.5 m). Trunk and proboscis pale to dark green, caused by presence of a dermal pigment, bonellin. One pair of ventral chaetae. Males 0.039–0.11 in (1–3 mm) long with a ciliated and planariform-like body, without pigment, proboscis, month, anus, or blood vascular system. Male's body occupied mainly by reproductive structures, and the male is often found living within the nephridia (genital sac) of the female.
DISTRIBUTION
Northeastern Atlantic Ocean, Mediterranean, Red Sea, and Indopacific.
HABITAT
Female does not make its own burrow, but inhabits burrows excavated in gravelly bottoms or burrows with multiple exits in rocky substrata or in clefts in rocks. It can be found in depths from 33 to 328 ft (10–100 m). A number of commensals inhabit the burrow. Male lives in the genital sac or on the body of the large female.
BEHAVIOR
Contraction of proboscis stem permits animal to move, and its bifurcate end has powerful cilia that help in locomotion and feeding. Moves back and forth inside burrow, as well as out of it. Contractions of the female's body wall renew the oxygen supply in the burrow.
FEEDING ECOLOGY AND DIET
Detritus feeder; food consists of detritus, small animals, organic material located at the root of vegetation and patches of sand between small rocks. Extends the proboscis from the burrow and grazes on the surrounding substratum with its bifid terminal lobes. Cilia on the ventral side of the proboscis move small particles and muscles pick up the larger ones. Cilia and muscles transfer the bolus mixed with mucus to the mouth. All metabolic needs of male are supplied by exchange with the female's body, indicating male has a parasitic mode of life.
REPRODUCTIVE BIOLOGY
Sexes are separate and fertilization occurs in the genital sac, where male often lives. Larva is free swimming. Bonellin has an important role in the determination of sex; it is considered
to be a masculinizing factor. If the larva settles on ocean floor, it develops into a 3.9-in (10-cm) long female. If the larva settles on a female's body (particularly its proboscis), it develops into a 0.039–0.078-in (1–2-mm) long adult male in 1–2 weeks. Male lives as a parasite and produces a ready supply of sperm.
CONSERVATION STATUS
Not listed by the IUCN.
SIGNIFICANCE TO HUMANS
Specimens are commonly used as laboratory animals. The pigment bonellin has been studied as an important antibiotic. The substance has powerful and lethal effects on a number of organisms.
