Parasitology lec 22: Final Exam

How many crustacean species are listed in the lecture?

There are 42,000 crustacean species.

How many pairs of appendages does the crustacean head bear, and how many are antennae?

Head bears five pairs of appendages including two pairs of antennae.

What larval form occurs in crustacean development, and what are its characteristics?

Development includes a triangular larval form (the nauplius) bearing three pairs of appendages and a single medial eye.

Which crustacean species go through the nauplius stage?

All crustacean species go through the nauplius stage.

Do crustaceans that hatch at a later developmental stage still go through a naupliar stage?

Even those species that hatch at a later stage of development go through this naupliar stage.

Where is crustacean food ground and strained, and what are the two stomach regions?

Food is ground and strained in a muscular foregut consisting of a large cardiac stomach and a smaller pyloric stomach.

What does the cardiac stomach contain, and what does it do?

The cardiac stomach contains the gastric mill — chitinous teeth that grind food into a liquefied mush.

What is the pyloric stomach, and what occurs there?

Pyloric stomach is a thin walled chamber where the chemical digestion of food occurs.

How are nitrogenous wastes generally removed in crustaceans?

In crustaceans, nitrogenous wastes are generally removed by diffusion across the gills.

What nitrogenous waste do most crustaceans release?

Most crustaceans release ammonia.

What role do specialized cells on crustacean gills have in salt regulation?

Specialized cells on the gills also selectively expel and absorb salts.

What may crustacean excretory organs be more involved with than discharging nitrogenous wastes?

In most species, the so-called excretory organs may be more involved with the elimination of water than with the discharge of nitrogenous wastes.

How are crustacean excretory organs arranged, and where do they collect fluid from?

These organs are paired and collect fluid within tubules from the surrounding blood of the hemocoel.

Why are antennal glands also called green glands, and where are they located?

Antennal (green) glands — named because of their location near the base of the antennae and their color.

Where are maxillary glands found?

Maxillary glands — Found near the maxillary segments.

What is the crustacean cuticle composed of?

The cuticle that covers crustaceans is composed of chitin, protein and calcium carbonate (calcareous).

How does calcium carbonate content differ in harder, heavier cuticular plates?

The harder, heavier plates contain higher levels of calcium carbonate.

How does the cuticle at joints allow flexibility of movement?

The normally hard protective covering of cuticle is soft and thin at the joints between segments, allowing for flexibility of movement.

What is molting?

The process of making a larger cuticle.

What does molting allow?

Allows for growth.

What is ecdysis?

The actual shedding of the cuticle.

How many thoracic segments do members of Class Malacostraca have?

Thorax with eight segments.

How many abdominal segments do members of Class Malacostraca have?

Abdomen with six to seven segments plus a telson.

What forms the uropods in Malacostraca?

Appendages on the sixth abdominal segment are flattened to form uropods.

What proportion of crustacean species belongs to Malacostraca?

Contains nearly 60% of all crustacean species.

What groups are included in Malacostraca?

Includes decapods, isopods, amphipods, etc.

What regions make up the basic malacostracan body plan?

Basic body plan consists of a head, thorax and abdomen.

How are the head and thorax joined in Malacostraca?

The head and thorax are rigidly fused.

What does the carapace cover, and how does it extend?

Carapace: Covers the head and thorax, and extends posteriorly from the head functioning as a single unit (cephalothorax).

What is the rostrum?

Rostrum: In some species, the carapace bears a prominent anterior projection.

What cells cover Malacostraca species?

Malacostraca species are covered with chromatophores.

What are chromatophores?

Highly branched cells containing pigment granules.

What pigment colors are listed for chromatophores?

Pigments include red, black, yellow and blue.

Can a single chromatophore contain more than one pigment?

More than one pigment may be found within a single chromatophore.

How can malacostracans considerably alter their body color?

By varying the pigment distribution in the different chromatophores over time, the animal can alter its body color considerably.

What controls the migration of pigment granules within chromatophores?

The migration of pigment granules within chromatophores is under hormonal control.

Where are the hormones controlling pigment migration produced and stored?

The hormones are produced in the X-gland and stored in the sinus gland.

Where are the X-gland and sinus gland located?

The X-gland and sinus gland are located in the eye stalks.

How are the hormones transported to the chromatophores?

The hormones are transported in the bloodstream to the chromatophores.

Why is malacostracan color change slower than in some other invertebrates?

Because chromatophore operation is under hormonal control rather than direct nervous control, malacostraca color change is not as rapid as in some other invertebrates.

What familiar crustaceans belong to Order Decapoda?

Best known of the crustaceans and include lobsters, crayfish, hermit crabs, true crabs and shrimp.

Which order is best described by the general description of Malacostraca?

The description of the malacostraca best describes the members of decapoda.

How many thoracic legs do decapods have?

Decapods have only 10 thoracic legs (5 pairs).

What are the first three pairs of thoracic appendages called, and what are they modified for?

The first three pairs of thoracic appendages (maxillipeds) are modified for feeding.

How many pairs of leg-like appendages do decapods have on the abdomen?

They also have 5 pairs of leg-like appendages on the abdomen.

What is stated about the terms used for decapod development?

The terms vary with different species.

How widely does the listed decapod life cycle apply?

Most go through the following life cycle.

Where do decapod embryos develop through the nauplius larval stage?

Embryos develop through the nauplius larval stage (externally, beneath the abdomen of the mother).

Is the nauplius stage free-living in the listed decapod life cycle?

Thus the nauplius stage is not free-living.

What does the nauplius develop into, and when is it released from the mother?

The nauplius develops into a zoea larva which is released from the mother.

What characterizes zoea larvae?

Zoea larvae are characterized by a pair of large compound eyes and a spiny carapace.

What happens to the zoea larva before it reaches the megalopa stage?

The zoea larva goes through several molts and then transforms into the megalopa stage.

What does the megalopa stage usually resemble?

The megalopa stage usually looks similar to the adult stage.

Which animals are an exception to the usual similarity between the megalopa and adult stages?

Crabs are an exception.

How does the abdomen of a crab megalopa differ from that of an adult crab?

In a crab, the abdomen of the megalopa is not tucked up under the thorax as it is in the adult crab.