L.S. Hydra Model

Quick Answer: The L.S. hydra model is an enlarged longitudinal section (L.S.) of Hydra, a small freshwater cnidarian, cut lengthwise to show its two cell layers and central cavity. The hydra model is used in zoology to teach the diploblastic body plan, feeding with stinging cells and budding.

Reading a Longitudinal Section of Hydra

Hydra is a tube-shaped polyp, from a few millimetres to around a centimetre or more long when extended, attached by a basal disc and crowned with a ring of tentacles round the mouth on a raised hypostome. Cutting it lengthwise reveals the simple body plan that defines cnidarians: an outer ectoderm (epidermis), an inner endoderm (gastrodermis) and between them a thin, jelly-like mesoglea. The single internal space, the gastrovascular cavity, has one opening, the mouth, which both takes in food and expels waste.

An L.S. hydra model shows the cell types in each layer. Stinging cells, the cnidoblasts with their coiled nematocysts, are concentrated on the tentacles; the ectoderm also contains epithelio-muscular and interstitial cells, and the endoderm contains nutritive-muscular cells and gland cells that release digestive enzymes. Many models add a bud growing from the body wall, or gonads, to introduce asexual and sexual reproduction.

Details such as whether a bud, testis or ovary is included, the size and the mounting are not in the title and can be confirmed with LabEquip.

Zoology Topics

• The diploblastic body plan and radial symmetry of cnidarians
• How nematocysts discharge to capture prey
• Extracellular and intracellular digestion in the gastrovascular cavity
• Asexual reproduction by budding and the regeneration experiments of Abraham Trembley

Specifications

Care & Handling

• Stand the L.S. hydra model on a flat surface, or hang it by its fixings if it is board-mounted; slender tentacles are the weak point.
• Remove dust with a soft brush and do not rub the painted cell layers.
• Store it away from sunlight and damp.

Why Choose LabEquip

Zoology classes meet Hydra early as the model cnidarian, and a sectioned model lets the whole group see the cell layers at once. LabEquip lists it within its biology lab products, and the hydra chart shows the same section in labelled form. Order through the LabEquip contact page.

Frequently Asked Questions

What does L.S. mean in the model name?

L.S. stands for longitudinal section, a cut made along the length of the body. For Hydra it shows the tentacles, mouth, body wall layers and the gastrovascular cavity running from the mouth to the base.

Why is Hydra called diploblastic?

Its body wall is built from two cell layers, the ectoderm and the endoderm, with non-cellular mesoglea between them. Most other animals are triploblastic, with a third layer, the mesoderm, that forms muscles and organs.

How do the stinging cells work?

Each cnidoblast contains a capsule, the nematocyst, with a coiled thread. When the trigger bristle, the cnidocil, is touched, the thread shoots out to pierce or entangle prey and may inject a paralysing toxin.

How does Hydra reproduce?

Mostly asexually, by budding: a bulge grows out from the side of the parent, forms its own mouth and ring of tentacles, and finally pinches off to live independently. In unfavourable seasons it also reproduces sexually using testes and ovaries formed on the body wall.

How does Hydra digest its food?

Gland cells release enzymes into the gastrovascular cavity, where digestion begins outside the cells. Nutritive cells of the endoderm then engulf the partly digested particles and finish digestion inside food vacuoles.

Why is Hydra famous for regeneration?

Hydra can regrow a complete body from a small piece because it contains dividing stem cells. In the 1740s Abraham Trembley cut hydras into pieces and watched each piece form a new animal, one of the first experiments on regeneration.

Last Updated: September 2026