Extended Observation Description on Hydra viridissima
Hydra viridissima Pallas, 1766
Hydra viridissima in a Freshwater Aquarium
Hydra viridissima living amongst Java moss (Taxiphyllum barbieri) filaments in a freshwater aquarium.
Fig. 1: Hydra viridissima. Penetrant nematocysts (arrow), ejected sticky thread of a gultinant ptychocyst (double headed arrow). Scale bar indicates 250 µm.
Fig. 2: A closer look at the tentacles. The optical cross section shows three types of their cnidae: some penetrant nematocysts (arrow) showing shaft and coiled hollow tubule for transportation of the toxin into the prey, some more volvent spirocyst (arrowhead) and one glutinous ptychocysts (double headed arrow).
Scale bar indicates 25 µm.
Fig. 3: In the Hydra body. Nucleus of a zoochlorella (arrow), glutinous ptychocyst for attaching the animal to a surface (double headed arrow).
Scale bar indicates 10 µm.
The zoochlorellae
Some species of coccoid green algae live as symbionts (zoochlorellae) in the cells of many single-celled species from groups such as the amoebae, the ciliates or the foraminifera. However, zoochlorellae are also known in animals such as freshwater polyps, other groups of coelenterates, in freshwater sponges, turbellarians, etc. These symbioses are generally mutually beneficial, the hosts benefit from secreted assimilates of the algae, and the algae are better protected from grazing due to the size of the hosts.
When the hosts lack food, part of the zoochlorellae is usually digested.
Fig. 4: Chlorella vulgaris as symbionts in Hydra viridissima. Nucleus (arrow), cup shaped chloroplast (double headed arrow), oil droplet (arrowhead). Scale bars indicate 5 µm.
© Wolfgang Bettighofer,
images under Creative Commons License V 3.0 (CC BY-NC-SA).
For permission to use of (high resolution) images please contact postmaster@protisten.de.
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striolatum
teliferum
pseudopyramidatum
pyramidatum
scabrum
capitulum
forficulatum
oligacanthum
var. incisum
chlamydosporum
arcuatum
var. subavicula
truncata
var. quadrata
rubescens
venustum
var. excavatum
ralfsii
var. montanum
ralfsii
digitus
acerosum
intermedium
dissiliens
kuetzingii
ralfsii
var. hybridum
aureus
botrytis
quadratum
quadrum
crassa
digitus
var. lamellosum
digitus
var. latum
oblongum
interruptum
spec.
spec.
kinahanii
spec.
polymorphum
var. polymorphum
brebissonii
rotata
swartzii
antilopaeum
neosinuosum
thomasiana
var. notata
forficulatum
var. verrucosum
armatum
oblongum
rhomboidale
furcatum
uncinatum
hirsutum
cucurbitinum
minor
borreri
americana
coeseli
apiculata
simplicius
crassum
simonyi
var. sparsiaculeatum
caelatum
crux-melitensis
ehrenbergii
didelta
spongiosum
var. perbifidum
denticulata
dejectus
conspersum
papillifera
komarekii
arboricola
venustum
var. excavatum
pulchellum
tripus
subspicatus
convergens
nostochinearum
arcuata
grevillei
laevis
var. laevis
reticulatum
viridis
cystozygote
reinhardtii
lacustris
speculum
New items
striolatum
teliferum
pseudopyramidatum
pyramidatum
scabrum
capitulum
forficulatum
oligacanthum
var. incisum
chlamydosporum
arcuatum
var. subavicula
truncata
var. quadrata
rubescens
venustum
var. excavatum
ralfsii
var. montanum
ralfsii
digitus
acerosum
intermedium
dissiliens
kuetzingii
ralfsii
var. hybridum
aureus
botrytis
quadratum
quadrum
crassa
digitus
var. lamellosum
digitus
var. latum
oblongum
interruptum
spec.
spec.
kinahanii
spec.
polymorphum
var. polymorphum
brebissonii
rotata
swartzii
antilopaeum
neosinuosum
thomasiana
var. notata
forficulatum
var. verrucosum
armatum
oblongum
rhomboidale
furcatum
uncinatum
hirsutum
cucurbitinum
minor
borreri
americana
coeseli
apiculata
simplicius
crassum
simonyi
var. sparsiaculeatum
caelatum
crux-melitensis
ehrenbergii
didelta
spongiosum
var. perbifidum
denticulata
dejectus
conspersum
papillifera
komarekii
arboricola
venustum
var. excavatum
pulchellum
tripus
subspicatus
convergens
nostochinearum
arcuata
grevillei
laevis
var. laevis
reticulatum
viridis
cystozygote
reinhardtii
lacustris
speculum