Study Guide on Larval Stages of Shrimp, Salmon, and Molluscs

Shrimp Larval Stages

  • Stages in Order: Protozoea → Mysis → Postlarva

    • Protozoea

    • Description: Early larval stage of shrimp.

    • Characteristics: Planktonic, meaning they drift with water currents.

    • Mysis

    • Description: Planktonic stage that leads to the later larval development.

    • Characteristics: Drifts towards coastal areas, where they can find suitable habitats.

    • Postlarva

    • Description: Stage produced after the metamorphosis of the Mysis.

    • Characteristics: Begins developing features typical of adult shrimp form.

    • Memory Trick: "Proto Makes Post-shrimp" to remember the sequence of stages.

Salmon Development

  • Stages in Order: Alevin → Fry → Parr → Smolt

    • Alevin

    • Description: First larval stage of salmon.

    • Characteristics: Contains yolk sac, remains in gravel redd (nest).

    • Fry

    • Description: Small early fish stage.

    • Characteristics: Begins swimming and feeding actively.

    • Parr

    • Description: Stage where young salmon live in rivers.

    • Characteristics: Notable for camouflage markings that help them blend into their environment.

    • Smolt

    • Description: Transition stage before entering the ocean.

    • Characteristics: Loses markings, becomes silvery in color, and adapts physiologically for life in the ocean.

    • Memory Trick: "A F P S" to help remember the sequence of salmon development stages.

Mollusc Larval Stages

  • Stages in Order: Trochophore → Veliger → Spat

    • Trochophore

    • Description: First larval stage of molluscs.

    • Characteristics: Exhibits cilia movement, allowing it to be planktonic and float in water.

    • Veliger

    • Description: Second larval stage of molluscs.

    • Characteristics: Has a velum organ that is significant for movement and feeding; beginning of shell formation.

    • Spat

    • Description: Stage where the larva settles on a substrate, transitioning towards becoming a juvenile mollusc.

    • Memory Trick: "Trocho Veliger Spat" to recall the order of mollusc larval stages.