Hydra Chart, Zoology, School Education

Quick Answer: A Hydra chart is a zoology wall chart of the freshwater cnidarian Hydra, with labelled diagrams of its tube-shaped body, tentacles, stinging cells and two body layers, and usually its budding and sexual reproduction. It is used to teach the simplest multicellular animal body plan.

Hydra: A Two-Layered Animal in Diagrams

Hydra is a small freshwater animal, rarely more than a centimetre or two long even when stretched out, that hangs from pond weed by its basal disc. The whole-animal drawing on a Hydra chart labels the basal disc, the slender body column, the hypostome (a cone around the mouth) and the ring of hollow tentacles. A longitudinal section shows why Hydra is called diploblastic: an outer ectoderm and an inner endoderm separated by jelly-like mesoglea, surrounding one gastrovascular cavity with a single opening.

Enlarged insets usually show a cnidocyte with its coiled thread, the nematocyst, before and after discharge, since these stinging cells capture water fleas and other small prey. Reproduction panels show a bud growing out of the body wall and detaching as a new individual, and the testes and ovary that appear as swellings on the body during sexual reproduction.

Hydra is also the textbook animal for regeneration, first described by Abraham Trembley in the 1740s: a cut fragment can regrow the missing parts.

Specifications

Applications

• Introducing the phylum Cnidaria and the diploblastic body plan
• Teaching asexual reproduction by budding, alongside budding in yeast
• Comparing the drawing with a live specimen or prepared slide under the microscope
• Regeneration lessons in senior secondary biology

Care & Handling

• Hang the Hydra chart near the microscope bench so students can look up from the slide to the labelled tentacles and hypostome.
• Keep pond-water cultures and aquaria at the other end of the room; damp air and drips ripple the paper.
• Roll the sheet loosely so the fine lines marking the two cell layers do not crack.

Why Choose LabEquip

Zoology teachers often order the Hydra chart with other invertebrate titles such as the Insects Charts. Hydra slides from the prepared slides range let students compare the diagram with a real specimen, and the LabEquip contact page takes orders.

Frequently Asked Questions

Why is Hydra called diploblastic?

Its body wall develops from only two germ layers, the outer ectoderm and the inner endoderm, with non-cellular mesoglea between them. Most animals studied later in school are triploblastic, with a third layer called the mesoderm.

How does Hydra catch its food?

Its tentacles carry cnidocytes, stinging cells that fire a thread into small animals such as water fleas. The tentacles then push the paralysed prey through the mouth into the gastrovascular cavity, where digestion begins.

How does Hydra reproduce asexually?

By budding. A small outgrowth forms on the body wall, develops its own tentacles and mouth, and then separates from the parent as an independent Hydra. Budding is common when food is plentiful.

Can Hydra regenerate lost parts?

Yes. When Hydra is cut into pieces, each piece can grow into a complete animal, because the body keeps a supply of cells able to divide and specialise. That makes it a classic example in regeneration lessons.

How does Hydra move?

It can glide slowly on its basal disc, and it also moves by looping or somersaulting: it bends over, attaches its tentacles to the surface, releases the base and flips it across.

Can live Hydra be observed in school?

Often, yes. Hydra can be found attached to water plants in clean ponds and watched with a hand lens or under low power. Where live material is not available, a prepared slide shows the same structures.

Last Updated: September 2026