young, 2.8 mm
with egg masses
Chelidonura hirundinina (Quoy &
|Maximum size: about 20 mm
variably decorated with orange and blue/green
lines. Portions of the blue/green lines may be replaced by white in
some animals. The most consistent characteristic is the ring of
blue/green surrounding an orange bar on the top of the head with a
central extension onto the notum. The width of the lines is variable.
The "tails" are also highly variable ranging from short and symmetrical
to long and asymmetrical. In asymmetrical animals, either the right or
left hand "tail" may be longer in contrast to most Chelidonura spp (perhaps reflecting
loss to predators and regeneration?). Some "tails" may also have
rounded rather than acute
tips. (Note 1) (Note 2)
is a common diurnal species found in protected to highly exposed
locations. It occurs in rocky habitats and Halimeda kanaloana beds from < 1
m (3 ft) to at least 30 m (100 ft). It can also be found in tide pools.
Kay (1979) reports it as occurring on Spyridia and Padina but we haven't noticed any substrate preference. It probably feeds on small
flatworms. (Note 3). A fringe of sensory hairs
at the front of the head is used to detect prey and it secretes a
yellowish fluid when disturbed. In dishes, its egg
masses are small, irregular white clumps composed
of an irregular string. However, when laid in the field, they are
"spun" around the body from the head backwards and probably retain a
sack-like form (presumably because their sticky surfaces collect
detritus for reinforcement). (Note 4)
Occasionally, they may form mating aggregations (see photo).
occurs in about four days
in the laboratory. (Note 5)
Big Island, Maui, Oahu, Kauai, French Frigate Shoals, Laysan, (Note 6) Lisianski, and Midway (also Johnston Atoll):
the "blue swallowtail slug" in Hoover, 1998 &
2006. The right hand drawing labeled C.
hirundinina in Kay, 1979 is actually Chelidonura
Mala Wharf, Maui; May 2, 2006
Observations and comments:
Note 1: Animals from
highly exposed habitats such as north shore tide pools tend to have
short symmetrical "tails," fine lines and extensive white pigment.
Animals from protected sites such as off-shore Halimeda kanaloana beds tend to
have long asymmetrical "tails," wide lines and no white pigment.
from intermediate sites show intergrading. Perhaps, the
habitat-correlated differences are due to differences in diet and/or a
response to surge?
Note 2: Animals that have short symmetrical "tails," fine
lines and extensive white pigment have been observed copulating with
animals that have long asymmetrical "tails," wide lines and no white
pigment. That supports the suggestion that they're the same species.
Note 3: Several times in
1998 animals were placed in dishes with 1.5-2 mm specimens of Convolutriloba longifissura (tentatively listed by Poulter as Convoluta sp. in section two of
Reef and Shore Fauna of Hawaii, 1987). Most of the time, the Chelidonura ignored the worm. A
couple of times, however, the worm was partially engulfed or "tasted"
before being rejected. Once, it was completely "inhaled" with a speed
comparable to that shown by Biuve cf. fulvipunctata, then immediately "spat out", apparently unharmed.
Perhaps, evolving an early rejection response to Convoluta sp. would make sense for C. hirundinina if the worm is toxic
or distasteful? In contrast, larger animals
ate and retained very small worms in 2003 and 2006. Perhaps, there is a
threshold in the response based on relative size? Or, multiple species
of small, red worms?
Note 4: A 19 mm animal
(measurement probably included "tail") was found in the field on Sept
27, 1994 with only the tip of its "tail" protruding from what appeared
to be a "clump of detritus/algal fragments." When the "clump" and animal were brought in and examined, it proved to be a
sack-like egg mass "spun" around the animal's body. It was about 20 mm
in diameter. Algal fragments and detritus were interwoven with the egg
strings and adhered to them strongly. The mass retained its sack-like
structure after laying, unlike masses laid in the laboratory that do
not incorporate any detritus into their structure. Perhaps, the
detritus provides camouflage in addition to reinforcement?
Note 5: In video shot by Pam Madden in the field, a mating pair took a little over three minutes to go from first contact to separation.
Note 6: There's some chance that the animal described from Laysan by Bergh, 1900 as C. hirundinina var. elegans might turn out to be Chelidonura alisonae, instead (if I could read German...).