Lecture Notes: Cubozoa - Box Jellyfish

Introduction

• Fourth class of Cnidaria: Cubozoa (Box Jellyfish)
• Previously categorized as Scyphozoa (true jellyfish)
• Notable for morphological distinctions

Morphological Characteristics

• Dominant Medusa Stage
  • Unlike Hydrozoans and Anthozoans
  • Similar to Scyphozoans and Staurozoans
• Box-like structure
  • Square appearance in cross-section
  • Four pedalia, one at each corner
  • Tentacles with nematocysts
• Velarium
  • Increases swimming efficiency
  • Allows rapid movement

Anatomy

• Manubrium and Mouth
  • Leads to gastrovascular cavity
  • Central stomach and four gastric pouches
• Developed Nervous System
  • Nerve ring coordinates pulsing
  • Human-like eyes with retinas, corneas, lenses
  • Unique among non-bilateria animals

Sensory Structures

• Rhopalia
  • Four clusters containing eyes
  • Two lensed eyes per cluster
  • Simple pigment-cup ocelli
  • Total of 24 eyes (4 types)
• Statoliths for balance
• Complex visual guidance and decision-making
• Ongoing research on vision and image processing

Life Cycle

• Largely unknown for most species
• General cycle:
  • Zygote -> Planula-larva -> Creeping polyp
  • Asexual reproduction via budding in some species
  • Transformation into medusa buds and mature adults

Venom and Human Interaction

• Known for painful and potentially deadly stings
• Notable Species:
  • Chironex fleckeri (Sea Wasp)
  • Irukandji Jellyfish
  • Viper Jellyfish
• Treatment:
  • Vinegar to disable nematocysts
  • Hospitalization for severe cases
• Statistics:
  • 225 envenomations (1991-2004, Australia)
  • Majority report mild irritation; few severe

Conclusion

• Box jellyfish are less deadly in reality than portrayed
• Next topic: Class Anthozoa (corals, anemones, sea pens)