A creature from outer space or a
hydroid for Liberace's piano?
A
few months back (February, 2003) I was in Atlanta Georgia with Two
Little Fishies, Inc. exhibiting our products at the American Pet
Products Manufacturers Association's annual trade show. Before the
trip I was speaking to Bruce Carlson via e-mail, and he
recommended that I make time to visit the Lovett School when I was
in town. He gave me the contact information for Dan Dalke, who
runs the science program there. Dan's high school marine biology
students have an aquaculture program that includes a lab with
several coral culture aquariums. As Bruce put it, “The
instructor obviously realizes the importance of these aquarium
systems in helping students understand how coral reef ecosystems
work,” and this was “a heavily endowed school with very
‘enlightened’ and enthusiastic students -- the kind you wish
every school had.” I planned to make time for a visit.
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I spent the majority of the
time in Atlanta at the trade show in our Two Little Fishies booth,
but I had also planned to give an evening lecture at a terrific
local shop called The Fish Store and More, and there was time to
fit in a quick stop by the Lovett School in the late afternoon on
my way to the lecture.
Dan Dalke gave me a tour
of his lab and introduced me to a few of his students, who stayed
after school to meet me. Unfortunately some other students were
unable to stay. When they were showing me some of their tank
experiments, Dan pointed out a puzzling problem they had noticed.
The mushroom anemones (Discosoma
sp.) that had
previously thrived in one exhibit were dying back for some reason.
As I was looking at the different tanks I had been noticing what I
at first thought were a large number of a sessile Ctenophore in
the genus Coeloplana,
which have highly contractile fine hair-like tentacles. I was
watching one more closely now as Dan asked the question about the Discosoma die-off. In an instant I realized that the culprit was
these "things" proliferating over the rocks in his
system, and they weren’t Coeloplana
at all. They had bottle-brush tips to their contractile worm-like
bodies, and these bottle-brush tips reminded me of the polyps of
some types of hydroids. They had to be stinging the mushroom
anemones. Seldom am I at a loss for a name for an invertebrate in
a reef aquarium, but here I was calling these things,
"things" and I was beginning to sound like Steve Martin
on Saturday Night Live saying over and over "What the Hell is THAT!?" I asked Dan if he had a dissecting scope so we
could have a closer look at them, and the students gathered some
snail shells and small rocks with several examples of these
creatures. They were literally all over the place in the tanks.
While the dissecting
scope was being set up, I shot a few images of the creatures on
rocks in the tanks. They have an extremely elongate and
contractile body that assures at least part of them will be out of
focus due to the depth of field required to capture the whole
creature in the image. This fact combined with their constant
expanding and contracting in the currents, and hair-thin light
colored bodies makes them very tricky to photograph. When we were
able to isolate a single creature under the scope, I used my Nikon
Coolpix to photograph it. The Coolpix lens fits closely on the
eyepiece of most microscopes, and with some practice, proper
lighting, and a steady hand one can take good images of objects in
the field of view.
When I got home I
forwarded images to several colleagues who specialize in cnidaria,
including Daphne Fautin at the University of Kansas. I got a reply
from Marymegan Daly, at the Dept. of Ecology and Evolutionary
Biology at the University of Kansas, who told me of a discussion
on the cnidaria listserve that had been occurring simultaneously
with my inquiry into the mystery creature. The archive of this
discussion, including images, can be seen at:
Look under the subject
headings for February and March, regarding Myriothela
(in February) and Candelabrum
(in March).
The mystery
hydrozoan now appeared to have a name, a genus at least, as the
photographs showed that the newly described Candelabrum
fritchmanii were quite like the creature in the aquariums at the
Lovett School. So, Candelabrum it is. The name reminds me of a particular episode of
Bugs Bunny cartoon I must have seen a hundred times as a kid. In the
cartoon Bugs does a Liberace impression, telling his foil, slowly, to
“Bring the Candelabrum to muh-ther, … George.” The Candelabrum of
course had been loaded with dynamite and you can imagine what happened
next.
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This Candelabrum
sp. hydroid holds no candles per se, but it is a little
firecracker! It has capitate tentacles that pack a powerful sting,
and it uses them to snare small crustaceans such as copepods and
amphipods. It also can catch brine shrimp or flake-food particles.
The prey is captured both from the water column and from the
adjacent rocky substrate as the polyp often extends out into and
onto them. The powerful nematocysts are used not only for food
capture but also for defense. This was manifest in the
disappearing mushroom anemones. Considering its ability to
proliferate in an aquarium and its stinging capacity, this
creature qualifies as a new pest to be avoided, among the ranks of
Aiptasia or Anemonia manjano anemones, or the zooxanthellate hydroid Myrionema
(Sprung, 2001). However, this creature is so fascinating to
observe and obviously easy to keep that I have to add it would
make a great display on its own in a small aquarium.
Description of
the genus Candelabrum, from
Hewitt and Goddard:
Polyps solitary or
colonial connected in groups of two or three, vermiform; total body
length from 10 to 300 mm. Body with three regions: basal foot or
hydrorhiza region for attachment to substrate, blastostyle-bearing
region, and distal body region (trunk), latter usually tapering, with
small circular mouth at extreme end. Foot shape variable, both between
species and with age; usually flattened and lobed to greater or lesser
extent, or conical, pointed (root shaped); always with anchoring
filaments, latter usually with chitinous discs for substrate attachment.
Whole or part of foot (including anchoring filaments and discs)
sometimes with citinous perisarc sheath, occasionally of considerable
thickness. Blastostylar region only distinguishable in sexually mature
individuals, usually swollen compared with trunk; blastostyles tubular
to conical prolongations of the body wall, either irregularly
distributed or arranged in one or several whorls, bearing cryptomedusoid
gonophores; body cavity may continue into blastostyles. Trunk length
equal to or much longer than blastostylar region, usually with numerous
small, capitate tentacles. Tentacles occasionally continue down to
blastostylar region and on blastostyles. Modified tentacles sometimes
present on blastostyles or foot. Enteron with folds of endoderm. Cnidome
composed of desmonemes (usually two types), haplonemes (usualy atrichous),
heteronemes, and stenoteles.
Modes
of reproduction
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In addition to the
aforementioned asexual reproduction methods, Candelabrum
spp. exhibit the following sexual reproduction characteristics. Larvae
develop into actinulae in the female gonophores, with one or more
larvae per gonophore. Feeding tentacles with claspers attached to
gonophores with developing eggs in some species. Actinulae of Candelabrum
fritchmanii released in a laboratory aquarium were about 1mm long
and had approximately 20 primary tentacles each of up to 1mm in
length. They grew to 2mm in length in four days, and 10mm long in two
weeks, and the posterior end developed into a root-like structure
(Hewitt and Goddard, 2001).
There are approximately 15
species described in the genus Candelabrum,
although five of them may be synonyms, leaving 10 known species. None
are strictly tropical, though one, C.
australe, occurs in New South Wales Australia, a region where both
tropical and temperate species of all kinds of marinelife can be found
living together. Hewitt and Goddard, 2001, furthermore discusses
aspects of the taxonomy of the family Candelabridae and the genus Candelabrum,
which was once known as Myriothela.
The description of the systematics by Hewitt and Goddard includes
emendations to the family, subfamily, and genus descriptions, to
accommodate the fact that the newly described species Candelabrum
fritchmanii occurs in a colonial form of multiple polyps in
addition to solitary polyps. It is of particular importance to note
that the species at the Lovett school also appears to occur in
solitary and multiple polyp forms, thus the character observed to be
unique for C.fritchmanii
may not be. It is possible that having the opportunity to culture Candelabrum
spp. in aquariums may afford greater opportunity to observe their
complete range of form. It may turn out that many or all species in
the genus have the ability to form multiple polyps, and the absence of
this characteristic in the literature describing them merely
represents the limitations of descriptions based on the harvest of a
few specimens. Stepanjants et al. (2002) showed species of Monocoryne,
the other genus of hydroid in the family Candelabridae, exhibit
immature polyps in aggregations attached to the adult polyp at the
pedal disc, and they easily break apart from their point of
attachment, indicating a form of asexual reproduction quite like the
budding observed in anemones. Hewitt and Goddard, 2001 also speculate
that the linked polyps may represent a form of asexual reproduction.
When I observed the numbers of polyps at the Lovett School I had the
impression that they were reproducing asexually by longitudinal
fission, something like the method of reproduction in colonies of the
soft coral genus Xenia. This
idea is supported by Hewitt and Goddard’s observation of one
specimen split into two sections halfway up the distal region that
bears the tentacles.
Table 1
Taxonomic
position of the Family Candelabridae
phylum
Coelenterata
class
Hydrozoa
subclass
Athecatae
order
Capitata
family
Candelabridae
There are 2 genera
within the Family Candelabridae:
genus Candelabrum
genus Monocoryne
Based on the brief
descriptions of the different Candelabrum
species, it appears likely that the one at the Lovett school is
undescribed. It may also be a first known strictly tropical species, or
it may give a range extension for an already known species. It is
unfortunately impossible to say for sure where it comes from, as it was
introduced to the system at the Lovett School from a separate reef
aquarium. I’ll pursue the matter of describing this Candelabrum sp. with researchers who specialize in this group.
Special
thanks to Bruce Carlson, Dan Dalke and his class, Daphne Fautin,
Marymegan Daly, and the staff at The Fish Store and More, who carefully
packed a specimen of Candelabrum for me, among other aquatic goodies.
References
Hewitt, C.L. and
Goddard, J.H.R. 2001. A new species of large and highly contractile
hydroid in the genus Candelabrum (Hydrozoa; Anthoathecatae) from Southern Oregon, U.S.A. Can.
J. Zool. 79: 2280-2288.
Sprung, J. 2001. Invertebrates:
A Quick Reference Guide. Ricordea Publishing.
Stepjants, S.D.,
Christiansen, B.O., Svoboda, A., and Anokhin, A. 2002. The Genus Monocoryne
(Hydrozoa, Capitata): peculiarities of morphology, species composition,
biology and distribution. Sarsia
