Question

Problem 3:

a. In which of the worm phyla: Plathymelminthes, Nemertea, Nematoda and Anellida are there parasitic worms? What morphological (form), physiological and reproductive adaptations do parasitic organisms (from the phyla Plathymelminthes, Nemertea, Nematoda and Anellida)must have in order to be successful?

b. Briefly describe the method of reproduction of earthworms and how is it well adapted to the environment they inhabit (do eartworms must have in order to be successful?)

Answer 1

A)

Parasitic worms belong to nematodes.

Parasitic worm resides in the gut,gastrointestinal tract , small intestine etc.

Their adaptations are

They respire anaerobically as there is lack of oxygen in the intestine

Platyhelminthes has both male and female sexes in the same animal. That is they are hermaphrodite. So they can fertilize itself.

They lack sensory organs such as

Flame cells help in osmoregulation and excretion.

They have many mechanism that increase their reproductive potential

Their epidermis is absent and they have developed adhesive organs.

Degeneration of muscular and nervous system

B)

Method of reproduction in earthworms

Earthworms are simultaneous hermaphrodites, meaning worms have both male and female reproductive organs. During sexual intercourse among earthworms, both sets of sex organs are used by both worms. If all goes well, the eggs of both of the mates become fertilized. You can imagine this is a highly efficient way of ensuring the survival of the species. Vermicomposters, people who raise worms and other organisms to compost, report that their earthworm populations typically double every 60 to 90 days

To copulate, two worms line up against one another facing opposite directions. In this position, both worms excrete so much mucous, that what is called a slime tube forms around their bodies. Each worm ejaculates sperm from its sex organs into this slime tube and it is then deposited in the other worm's sperm receptacle. The act of mating is completed, but the process of reproduction still continues as each worm goes its separate way .

Clitellum is responsible for producing another tube of mucus. This band is passed forward toward the mouth end of the worm. As it travels forward, the mucus passes over the sacs containing the worm's own eggs, which stick to the slime. Attached to the slime tube, the eggs then pass over the seminal receptacle, where the other worm's sperm is kept. The eggs and sperm come in contact in the slime tube and if all goes well, the eggs are then fertilized.

The band of slime is wriggled off the head of the worm and forms a cocoon in the shape of a lemon for the anywhere from four to 20 worm eggs that the common European earthworm typically lays. In about two to three weeks, the newborn worms will hatch and emerge from the cocoon into the soil. This cycle of reproduction can happen every week to 10 days, another reason earthworm populations can grow so quickly

Earthworms can also reproduce themselves if need be. They can regenerate new segments if they lose a few. Most earthworms are better at regenerating tails than heads, but some can. They don't reproduce asexually, however; only half (and likely the head half) of an earthworm split in two will regenerate into a full worm once again

adaptations of earthworm

Physical adaptations for life underground

Although earthworms are classified as animals, their bodies are quite different to animals that live above the ground. This video highlights some of the interesting physical characteristics common to earthworms.

Adaptation is also a common term to describe these helpful or adaptive traits. In other words, an adaptation is a feature of an organism that enables it to live in a particular habitat.

Most species of earthworms share some common traits or adaptations, such as their streamlined body shape. However, different species of earthworms have adapted to different habitats and occupy different niches within the ecosystem. As a result, earthworm adaptations are many and varied. In all animals, types of adaptations can be grouped into three main categories: structural, physiological and behavioural.

Structural adaptations

Structural (or morphological) adaptations are the physical features of the organism. These include things you can see, like its shape or body covering, as well as its internal organisation.

structural adaptations of earthworms:

• Each segment on an earthworm’s body has a number of bristly hairs, called setae (sometimes written as chaetae). These hairs provide some grip to help the earthworm move through the soil.
• An earthworm has a streamlined body with no antennae or fins or arms or legs! This streamlined shape is an adaptation to living in narrow burrows underground and the need to move easily through the soil.
• An earthworm has circular muscles that surround each body segment. It also has longitudinal muscles that run the length of its body. These two groups of muscles work together to help the earthworm move.
• In order to get food into its mouth, an earthworm pushes its pharynx out of its mouth to grasp hold of its food. It then pulls the food back into its mouth and wets it with saliva

physiological adaptations of earthworms:

• Many earthworms secrete a mucus (coelomic fluid) that helps them to move more easily through the soil. In some burrowing species, this fluid forms a cement-like substance that lines their burrows to help keep the walls from collapsing. In the New Zealand native species Octochaetus multiporus, the mucus may also be part of its defence system as it is toxic to soil bacteria O. multiporus has another special adaptation – its mucus is bioluminescent! When it is disturbed, the O. multiporus earthworm squirts mucus from its mouth and dorsal (underside) pores, and the fluid emits a bright orange-yellow light that glows in the dark.
• When the environmental conditions in an earthworm’s habitat change, for example, the soil becomes too hot or too dry, many earthworms become inactive in a process called aestivation. They move deeper into the soil, coil into a tight ball, excrete a protective mucus and lower their metabolic rate in order to reduce water loss. They will remain like this until conditions become favourable again.

behavioural adaptations of earthworms are

• Earthworms cannot see or hear but they are sensitive to vibrations. Birds looking for food or humans collecting earthworms for bait stamp on or vibrate the ground in some manner, causing earthworms to move to the surface. Perhaps this is to escape from moles, whose primary food is earthworms. We don’t have moles in New Zealand, but some people think that earthworms carry a ‘memory’ of this predator and still respond by leaving the ground.
• Earthworms are sensitive to light. Most species spend their days in their burrows or in the soil or leaf litter. In general, you usually find them on the surface at night.
• Earthworms lose moisture through their skin. They move out of their burrows to migrate or reproduce when the ground is wet with dew – one reason why we may see them in the early morning.