Cnidarian Diversity

1. Cnidarian Diversity

6. Classes of Cnidaria • Anthozoa • Anemones and most corals • Scyphozoa • Jellyfish • Hydrozoa • Hydroids such as Hydra • Cubozoa • Cube jellies

10. Cubozoa Anthozoa Hydrozoa Scyphozoa Cnidarian Classes

11. Class: Hydrozoa

12. Hydrozoans • Large class with about 3,000 species • Life cycle • Has both polyps and medusae • Medusae usually solitary, small • Polyps predominate the life cycle • Polyps usually colonial • Habitat • Mostly marine • A few freshwater

14. egg Sexual Young polyp female sperm Asexual male Budding Hydra

15. Obelia - living

17. Order Siphonophorae Siphonophores

18. Siphonophores • Order of carnivorous colonial hydrozoans • About 175 species known • Most live in deep ocean, so more are being discovered as deep dive capabilities improve • Most are active swimmers • Typically elongate and rope-like, • some reach lengths of 40 meters or more • Gelatinous and most disintegrate when sampled with nets.

20. Siphonophores • Siphonophores have elaborated on coloniality • Unique form of individuality that has led many scientists to call them ‘superorganisms’. • Colonial animals consisting of many multicellular individuals called zooids (zoh – ids) that are each homologous to solitary free-living organisms. • Zooids within a colony are all derived from the same embryo and are genetically identical

21. Siphonophores • Add new zooids through asexual reproduction, such as budding or fission • Not followed by physical separation. • Zooids remain attached and physiologically integrated. • There can be a dozen or more functional classes of zooids in siphonophore colonies • arranged in precise species-specific patterns. • pattern is usually reiterated along a linear stem, • exact same sequence of specialized zooids repeated

22. Siphonophores • Importance of siphonophore colonial structure • The division labor between siphonophore zooids parallels the evolution of functional specialization at other levels of biological organization • Between cells in a multicellular organism • Between casts in eusocial insects. • Wide interest in evolution and developmental mechanisms involved in this division of labor • Recognition of self from non-self • Germ line segregation during development • Selection within organism – selection of cancer cell lines

25. Barrel eye Fish – kleptoparasite of siphonophores Macropinna microstoma

26. Physalia physalis

27. Physalia physalis • Portuguese Man of War • Hydrozoan • Colony of many specialized polyps • Deadly sting even when dead on the beach • Has symbiotic fish • Nomeus gronovii (juveniles) • Feed on Physalia tentacles and gonads , and may feed on other jellyfish

28. Nomeus gronovii

29. Physalia physalis • The PortugueseMan-o’-War consists of four main types of polyp. • A single polyp forms the large gas-filled float that sits on the ocean surface and acts as a sail. • Other polyp types specialise as feeding tentacles (gastrozooids, of which there are three types), • as defensive or prey-capturing tentacles (dactylozooids) and • Hang to a depth of up to 40 meter, • Deliver a powerful sting. • as reproductive organs (gonozooids).

31. The Portuguese man-o’war, Physalia physalis, is one of around 175 species in the order siphonophores, class Hydrozoa. It is not a typical member of the group. While Physalia drifts on the surface, blown by winds and carried by currents, most siphonophores are active swimmers and live beneath the surface. A few – the rhodaliid family – spend their lives tethered by their tentacles to the sea bottom. Because of their habitat and their fragility, siphonophores are extremely difficult to collect, and relatively little is known about them. Feeding Polyp Mouth

34. First Aid for Physalia Stings • Do not rub the sting area. • Remove any adhering tentacles. • Rinse the area well with sea water (not freshwater). • NO VINEGAR – can cause more envenomation by a newly discovered species of Physalia • Place the stung area in hot water - no hotter than can be comfortably tolerated. • If the pain is unrelieved by heat, or if hot water is not available, apply ice packs. • Send for medical aid if symptoms persist or worsen.

36. Glaucus atlanticus

37. Glaucus atlanticus

40. Vellela – By the Wind Sailor Order: Condrophora

41. VellelaNote: pneumatophore divided into multiple chambers. Only one gastrozooid, multiple gonozooids.

43. Commensal Hydrozoan, Hydractinia echinata, on shell of hermit crab. Some zooids modified into spines

44. First Aid for Physalia Stings • Do not rub the sting area. • Remove any adhering tentacles. • Rinse the area well with sea water (not freshwater). • NO VINEGAR – can cause more envenomation by a newly discovered species of Physalia • Place the stung area in hot water - no hotter than can be comfortably tolerated. • If the pain is unrelieved by heat, or if hot water is not available, apply ice packs. • Send for medical aid if symptoms persist or worsen.

45. Scyphozoa • Jellyfish • Medusa is dominant life history stage • Active swimmers • Contract muscles • Causes water to shoot out from bell • Mesoglea deforms • Propels animal forward • When muscles relax mesoglea pops back to normal shape • Pulls animal downward • So net forward movement is due to rapid speed of bell contraction

48. Scyphozoa • Feeding • Food captured by nematocysts • Passed to mouth and through manubrium to the four gastric pouches (coelenteron) • Partial digestion occurs in these pouches • Ciliated canals distribute partly digested food • Particles are phagocytized and rest of digestion is intracellular

49. Aurelia medusa

50. Scyphozoan Anatomy • Coelenteron (central blind sac) = gastrovascular cavity • Body wall composed of two epithelia • outer epidermis • inner gastrodermis • Mesoglea (gelatinous connective layer) lies between the two epithelia.