The mutant strain multi-headed-1 (mh-1) is a sexual inbreed generation of the wildtype (wt 105) of Hydra magnipapillata. It is able to produce several ectopic heads along its body axis (see figure, arrows).
chimeras of various cell types we could show that the cause for the
ability to form extra heads is located in the ectodermal epithelial
cells of mh-1. The interstitial cells are not involved in this
S. Zeretzke and S. Berking (1996) Analysis of a hydra mutant which produces extra heads along the body axis. Int. J. Dev. Biol. Suppl.1:271S
S. Zeretzke and S. Berking (2001) Pattern regulation of a Hydra strain which produces additional heads along the body axis. Int. J. Dev. Biol. 45: 431-439 (2001) (PDF_File)
S. Zeretzke and
S. Berking (2002) In the multiheaded strain (mh-1) of Hydra
magnipapillata the ectodermal cells are
|Budding of polyps
In Hydra sp. (Hydrozoa) and in Cassiopea sp. (Scyphozoa) a bud develops at the gastral region of the parent animal. The tissue of the bud does not originate from a meristem but from the gastral tissue of the parent animal. An important difference to note is that in hydrozoa the tip of the bud develops into the head of the polyp while in (many) scyphozoa the tip develops into the opposite part, namely the foot. Therefore, the central question is whether the systems which are controlling pattern formation in these animals are fundamentally different.
A summary of the latest experimental results and of the disscusion about models of control mechanisms of bud development in hydra can be found under Berking, 1998. There is a recent paper addressing bud development in Cassiopea sp. We offer a theoretical model of pattern formation which allows to understand bud development in hydrozoa and scyphozoa.
(1977). Bud formation in Hydra: Inhibition by an endogenous morphogen.
Roux's Arch. Dev. Biol. 181, 215-225.
Kehls, N.E., K.
Herrmann and S. Berking (1999) The protein phosphatase inhibitor
cantharidin induces head and foot formation in buds of Cassiopea
andromeda (Rhizostomae, Scyphozoa) Int. J. Dev. Biol. 43:51-58
of metamorphosis of Hydractinia echinata (Cnidaria), Cassiopea
andromeda (Cnidaria) and Ciona interstinalis
Most of the experiments were done with H. echinata
During the whole
year the colonies of Hydractinia echinata are fertile in the
laboratory. Within three days after fertilisation a larva
that is able to metamorphose. The larvae consists of 10. 000 cells, are
spindle shaped and covered by cilia. They neitehr have any organs, nor
can they eat but they have nerve cells with which they can find a place
can be induced by application of agents like CsCl, or by incubating the
larvae in Mg2+-free seawater or by incubation with dioctanoylglycerol.
There are around 20 agents known to induce metamorphosis. More than 500
substances have been tested until now. Most of these substances are not
found in the animal in sufficient concentrations (for example Li+, Cs+,
Rb+, amiloride and the phorbolester TPA), but help us to identify
the natural way for induction of metamorphosis. Most interesting are
substances that naturally exist in the animals like diacylglycerol,
various neuropeptides (LWamides) and NH4+.
Other endogenous substances like the neurotransmitter serotonin are necessary for induction of metamorphosis. Some endogenous substances are acting antagonistically by stabilising the larval state. N-methylpicolinicacid, N-methylnicotinicacid and, N-trimethylglycin belong to these substances. They influence transmethylation and the synthesis of polyamines.
Cassiopea andromeda (Scyphozoa) produce buds which are able to swim and look like planula larvae. Those buds can be induced to transform into a polyp. This process is also called metamorphosis. Most of the substances that lead to the transformation from larvae to polyps in H. echinata are ineffective in C. andromeda, for example the LWamides, dicapryloylglycerol (PKC-activator) and CsCl. Effective substances are the following ones: the phorbolester TPA, several peptides with characteristic composition (AG Prof. Hofmann, Bochum), which are inefective in Hydractinia ,NH4+ and cantharidin, a serine/threonine protein phosphatase inhibitor. Metamorphosis can be inhibited by endogenous substances. Substances, that are also effective in Hydractinia like homarine, trigonelline and methionine are suspected to work as a methyldonor in the process of transmethylation.
intestinalis (Chordata, Tunicata). It is possible to induce
metamorphosis from the larvae to the adult animal, like in Hydractinia
echinata and Cassiopea andromeda, with low concentrations
(1984). Metamorphosis of Hydractinia echinata. Insights into
pattern formation in hydroids. Roux's Arch. Dev. Biol. 193, 370-378.
and strobilation in Aurelia aurita
Larvae of cnidarians need an external cue for metamorphosis to start. The larvae of various hydrozoa, in particular of Hydractinia echinata respond to Cs+, Li+, NH4+ and seawater in which the concentration of Mg2+-ions is reduced. They further respond to the phorbolester Tetradecanoyl-phorbol-13-acetat (TPA) and the diacylglycerol (DAG) diC8 which both are argued to stimulate a proteinkinase C. The only well studied scyphozoa, Cassiopea spp., respond differently, i.e. to TPA and diC8 only. We found that larvae of the scyphozoa Aurelia aurita, Chrysaora hysoscella and Cyanea lamarckii respond to all compounds mentioned. Trigonelline (N-methylnicotinic acid) a metamorphosis inhibitor found in Hydractinia larvae which is assumed to act by delivering a methyl group for transmethylation processes antagonises metamorphosis induction in Chrysaora hysoscella and Cyanea lamarckii. The three species tested are scyphozoa belonging to the subgroup of semaeostomeae, while Cassiopea spp. belong to the rhizostomeae. The results obtained may contribute to the discussion concerning the evolution of cnidarians and may help to clarify if the way metamorphosis can be induced in rhizostomeae as a whole is different from that in hydrozoa and those scyphozoa belonging to the subgroup semaeostomeae.
Polyps of Aurelia
aurita can transform into several medusae (jellyfish) in a process
of sequential subdivision. During this transformation, two processes
take place which are well known to play a key role in the formation of
various higher metazoa: segmentation and metamorphosis. In order to
compare these processes in bilaterians and cnidarians we studied the
control and the kinetics of these processes in Aurelia aurita.
Segmentation and metamorphosis visibly start at the polyp’s head and
proceed down the body column but do not reach the basal disc. The small
piece of polyp which remains will develop into a new polyp. The
commitment to the medusa stage moves down the body column and precedes
the visible onset of segmentation by about one day. Segmentation and
metamorphosis can start at the cut surface of transversely cut body
columns, leading to a mirror-image pattern of sequentially developing
Strobilation of Aurelia aurita
B Siefker, M Kroiher, S Berking (2000) Induction of metamorphosis from the larval to the polyp stage is similar in Hydrozoa and a subgroup of Scyphozoa (Cnidaria, Semaeostomeae). Helgoland Marine Research 54, pp 230-236
M Kroiher, B
Siefker, S Berking (2000) Induction of segmentation in polyps of Aurelia
aurita (Scyphozoa, Cnidaria) into medusae and formation of
mirror-image medusa anlagen. Int. J. Dev. Biol. 44, pp
K, Siefker B, Berking S (2003) Sterile poystyrene culture dishes induce
transformation of polyps into medusae in Aurelia aurita (Scyphozoa,
Cnidaria). Methods in Cell Science 25, 135-136
Berking S, Czech N,
Gerharz M, Herrmann K, Hoffmann U, Raifer H, Sekul G, Siefker B,
Sommerei A, Vedder F (2005)
(1979). Control of nerve cell formation from multipotent stem cells in
Hydra. J. Cell Sci. 40, 193-205.
of control of pattern formation
To formulate theoretical models for control of pattern formation it is forst necessary to arrange a lot of experimental data with possible rare assumptions. We wish to understand the mechanisms of the control processes. We are aware that theoretical models are incomplete and preliminary. It is the function of such models to point the way for further experimental work and to help to establish the precise nature of the molecular and biochemical basis of control of pattern formation.
From our point of
view pattern formation in cnidaria is hierarchically organized. The
primary system controls the positional value of the tissue, while the
secondary systems become active at distinct positional values and
determine the local differentiation, for example the formation of
tentacles or the formation of the basal plate. As we take it, there are
two types of dominance in the primary system. The type 1 dominance is
identical to that autocatalysis proposed by Gierer and Meinhardt (1972,
Kybernetik) and therewith the coupled inhibition of this autocatalysis
in the surrounding of autocatalytically active cells. In the area of
autocatalysis the positional value of the tissue increases, if not the
type 2 dominance is effective. The type 2 dominance is based on the
assumption that in the area of autocatalysis a further long range
is generated, which decreases the positional value of the surrounding
(1979b). Analysis of head and foot formation in Hydra by means of an
endogenous inhibitor. Roux's Arch. Dev. Biol. 186, 189-210.
preferently asexually through budding The buds were build in a distinct
region of the body colomn the so called budding region. The first
visible tip of the bud developes into the hypostom of the animal.
Then the gastric region of the bud grows untill the bud forms foot
tissue, builds a constriction and separates from the parent animal. We
can show that signaltransduction pathways are involved in the pattern
forming process at the bud´s base. Especially modulators of
protein kinases interfere with this process. (F. Pérez and S.
Berking, 1994, Roux´s Arch. Dev. Biol. 203: 284-289.).
Abstract: The fresh water polyp Hydra can reproduce asexually by forming buds. These buds separate from the parent animal due to the developement of foot tissue in a belt-like region and the formation of a constriction basal to that region. A single pulse treatment with activators of protein kinase C , including 1,2-dioctanoyl-rac-glycerol and 1,2-o-tetradecanoylphorbol-13-acetate, and inhibitors of various protein kinases, including staurosporine, H-7 and genistein, interferred with foot and constriction formation. The buds did not separate. Therewith branched animals were formed some of which bore a lateral foot patch. Simultaneous treatments with an activator and a inhibitor led to a higher amount of branched animals than treatments with one of these agents alone. Based on the different specifities of the activators and the inhibitors used we propose that activation of a protein kinase C and/or inhibition of a probably non-C-type protein kinase interfere with the decrease of positional value at the bud´s base, a process necessary to initiate the pattern forming system leading to foot formation.
Furthermore there exists a link that a serine / threonine protein phosphatase (Typ 2A) is involved in pattern formation at the bud´s base. Incubating the animals with cantharidin (inhibitor of the PP2A) leads to the inhibition of foot formation at the bud´s base. It is out of question that protein kinases and phosphatases, which have an important function as a part of signal cascades during developmental processes in various organisms, are also involved in pattern formation in Hydra, which is an very old organism.
Besides serine /
threonine and tyrosin kinases and phosphatases we are interested in
which are directly or indirectly connected with those kinases /
phosphatases and play a role in the foot formation at the bud´s
base. We focus especially calcium and lithium. We can show that a
dcrease of the calcium concentration in the culturemedium to the
intracellular level leads to the formation of branched animals (s.
Hassel, M., and
Berking, S. (1990). Lithium ions interfere with pattern control in Hydra
vulgaris. Roux's Arch. Dev. Biol. 198, 382-388.
Zeretzke, Fernando Pérez, Kirsten Velden and Stefan Berking
(2002) Ca2+-ions and pattern
of spacing of polyps
In Eirene viridula new polyps are formed on adult stolons in a distance of 1,6mm to the last developed polyp. The endogenous substance homarine (N-methypicolinicacid) applied to seawater in concentrations of about 0,1 µM enhanced the distance. The antibiotic sinefungin, a competitor of S-adenosylmethionin (SAM), shortens this distance. It is possible that homarine is used as a donor of a methylgroup in the process of transmethylation for the formation of SAM. Therefore we assume that transmethylation plays an important role in the control of keeping a distance between polyps in a colony.
(1986). Transmethylation and control of pattern formation in Hydrozoa.
Differentiation 32, 10-16.
|Control of polyp polymorphism
Thecocodium quadratum (Werner, Jber. Biol. Anst. Helgoland,
1965) is a colonial hydroid which produces 2 different types of polyps:
gastrogonozooids and dactylozooids. The mouthless dactylozooids bear
tentacles and catch the prey, which is then taken over and swallowed by
the gastrogonozooids which have no tentacles. It is obvious that for a
colony to survive both polyps must exist simultaneously arranged in a
certain spatial pattern. Our experiments indicate that the formation of
polyps in a growing culture is governed by at least 3 principles: (1)
short range inhibition between polyps irrespective of their
differentiation; (2) long range specific inhibition between
gastrogonozooids; and (3) long range supporting influence (lateral
Meinhardt, H., Models of Biological Pattern Formation, 1982) between
gastrogonozooids and dactylozooids.
Pfeifer, R., and
Berking, S. (1995). Control of formation of the two types of polyps in Thecocodium
quadratum (Hydrozoa, Cnidaria). Int. J. Dev. Biol. 39, 395-400.
Schematic drawing of a colony of Laomedea flexuosa
The colonies of thecate hydroids are covered with a chitinous tubelike outer skeleton, the perisarc. The perisarc shows a species-specific pattern of annuli, curvatures, and smooth parts. This pattern is exclusively formed at the growing tips at which the soft perisarc material is expelled by the underlying epithelium. Just behind the apex of the tip, this material hardens. We treated growing cultures of Laomedea flexuosa with substances we suspected would interfere with the hardening of the perisarc (L-cysteine, phenylthiourea) and those we expected would stimulate it (dopamine, N-acetyldopamine). We found that the former caused a widening of and the latter a reduction in the diameter of the perisarc tube. At the same time, the length of the structure elements changed so that the volume remained almost constant. We propose that normal development involves a spatial and temporal regulation of the hardening process. When the hardening occurs close to the apex, the diameter of the tube decreases. When it takes place farther from the apex, the innate tendency of the tip tissue to expand causes a widening of the skeleton tube. An oscillation of the position at which hardening takes place causes the formation of annuli.
Kossevitch IA, Herrmann K,
Berking S. (2001) Shaping of Colony Elements in Laomedea flexuosa Hinks
(Hydrozoa, Thecaphora) Includes a Temporal and Spatial Control of
Skeleton Hardening. Biol Bull. 201(3):417-23.