1 / 64

Events in Fish Maturation

Events in Fish Maturation. Syndel International. Canadian owned Private specialist company Fish species only 25 years of service Domestic Vaccines, parasiticides, transport disinfectants, sedatives, anesthetics International Spawning agents, sedatives, transport chemicals.

juliana-ortiz
Download Presentation

Events in Fish Maturation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Events in Fish Maturation

  2. Syndel International • Canadian owned • Private specialist company • Fish species only • 25 years of service • Domestic • Vaccines, parasiticides, transport disinfectants, sedatives, anesthetics • International • Spawning agents, sedatives, transport chemicals

  3. Jim Powell, PhD • Product Development and Tech Support • Doctorate in Neuroendocrinology of Fishes • Former salmon farmer • 18 yrs in aquaculture • S&E trials Internationally

  4. Introduction • Overview of maturation process • Types of spawners • Methods of spawning

  5. Key Points • Two stages to getting quality gametes • Environment is the first step • Healthy animals is the second • Manipulation of spawning is third • There are different types of spawners • Mess with Nature, she’ll mess with you

  6. External Conditions • environmental • social • Internal Conditions • physiology Perception Integration Reaction Genesis of Maturation

  7. Environmental Influences • Temperate climates • Photoperiod • Temperature • Water quality • Equatorial climates • Temperature • Rainfall • Water quality

  8. Social Conditions • Loading density • +ve and –ve • Sex ratios • Nesting behaviour • Proper materials • Colouration • Pheromones • Attraction • Cue

  9. Internal Conditions • Physiology • Puberty • Fat content • Type and amount • Nutrition • Availability and quality • Disease • Size and shape

  10. Perception • Changes detected • Impulse transferred to brain • Signal pathways inform areas of the brain • Outside is now an inside thing • Integration

  11. Integration • Environmental and social cues are perceived and register • Physiological cues are detected and registered • The external and internal environments are integrated into a physiological response

  12. Reaction • Signals are coordinated in the hypothalamus • The hypo sends out messengers to the pituitary • The pit releases hormones into the blood • The hormones effect target organs

  13. HPG Axis • Common to all vertebrates • Hypo coordinates signals • Releases GnRH • Pit releases GtHs • GtHs bind to gonads • Gonads produce steroids • Steroids cause gonad growth

  14. Endocrine Cascade • Brain releases messengers • Pit releases gonadotropins • Gonads release steroids • Gonad forms gametes

  15. GtHs • There are two types: • GtH I causes vitellogenesis – egg building • GtH II causes oocyte maturation • Released consecutively

  16. Vitellogenesis • Ovary produces estradiol E2 • Liver produces yolk platelets or globules • Gonad incorporates yolk into eggs

  17. Steroids • Ovary • Makes estradiol, later progesterone • Egg building, then maturation • Testis • Makes testosterone • Makes the sperm, then capacitates the sperm

  18. Ovarian Cells • Two cell layers • Outside is theca • Inside is granulosa • Change function as egg goes from building to maturing

  19. Maturation • As GtHs change, so do the steroids • E2 turns to progesterone • P helps to mature the egg • Makes fertilization possible

  20. Summary • Conditions permit maturation • Process begins • GnRH – GtH – steroids • Eggs are built • Eggs mature • Correct environment • Spawning proceeds

  21. Stress and Spawning • External influences • Perception • Integration • Reaction

  22. Stress Response • Two stages: • Immediate • Flight or fight • Sustained • Extended energy supply • Change in metabolism • Puts all cell division on hold

  23. Stress and Spawning • Stressor is encountered • Animal becomes stressed • Endocrine cascade begins

  24. Stress Effects • Creates an assured supply of energy • Depletes liver glycogen • Releases sugars form protein wasting • Represses immunity • Inhibits growth

  25. Stress and Reproduction • Cortisol inhibits reproduction • Direct and indirect effects • Stops cell division • Limit or mitigate stressors in breeders

  26. Concept II: Spawning Specifics • Role of the environment is covered • Physiology is covered • Task is to get the things to breed

  27. Classifying Spawners Many ways: • By spawning type • By Linnaean methods • By guilds • By breeding patterns

  28. Groups of Spawners • Synchronous- all oocytes develop synchronously and ovulate at the same time. • Group-synchronous- oocytes ÷ into groups, ovulate over one breeding season. • Asynchronous- oocytes at all developmental stages are present in the ovary. Ex: tropical fish.

  29. Open substrate Nonguarder Brood hiders Substrate choosers Guarders Nesters External Bearers Internal Reproductive Guilds • Proposed by Balon, 1975 • Still in use today • An ecological approach • Non-Linnaean • Overlay with physiology

  30. Fish Evolution

  31. Where Is He Going With This? • An ecological model for breeding won’t work • A Linnaean model won’t work • Is there anything else?

  32. Spawning Fish Checklist • Environment is perfect • Fish health is excellent • Fish are gravid • Spawning them is easy

  33. Remember This? • GnRH has a primary role in reproduction • It is common to all things with a spine • Must be some connection to spawning groups

  34. A GnRH Primer: 1 • 1st called LHRH • Central role in reproduction • Different forms are found in different species • Linked through evolution

  35. A GnRH Primer: 2 • All vertebrates have at least two forms in their brains: • One for nervous function • One for reproduction • Some fish have three forms • The one in the pit is the repro one

  36. Two populations of neurons Hindbrain Midbrain C-II always in the hindbrain Pit form controls the GtH release Locations of GnRH Forms in the Brain

  37. GnRH in Fishes

  38. Percs Lots of Others • Ostariophyseans • Catfish • Tetras • Cyprinids • Characids • Pacu Salmonids Seabream Salmon Catfish Mammalian Boney tongues Eels Sturgeons and Paddlefish GnRH in Spawning Groups

  39. Ostariophysea • Catfish • Tetras • Characids • Silurids • Carps • Pacu • Knifefish

  40. Dopamine: Blocks release of GnRH Inhibits GtH release Released by environmental cues Must be blocked GnRH from the Hypothalamus Dopamine from the Hypothalamus -ve +ve Pituitary release of GtHs Dopamine Inhibition

  41. The Point Is: • Unless the fish is an Ostariophysean, GnRH alone should work • Based on principle

  42. Steroids • Act at the level of the gonad • Augment natural levels to advance gamete release • Overdose to get effect

  43. Steroids • Least desirable • Most dangerous method for you and fish • No control over dose • Wastewater nightmare • Can cause sterility, gynomastia

  44. Gonadotropins • Simulate or augment GtHs • Act at level of gonad • Stimulate ripening and release • Causes increased steroids and PGs

  45. CPE/LSP • Oldest method • Usually works • Not truly reliable • No dose conformation • Quality can vary • Stability issues • HCG is human equivalent

  46. Purity • Fish GtHs have not been synthesized • No recombinants to date • Vary with species • Large molecules mean stereo-conformity

  47. GnRH • Small molecule, decapeptide • 16 known variants • Central to reproduction • Top of the cascade • Robust

  48. Methods: GnRHa • Many forms: powder, liquid, implant • Ovaprim is sterile solution with dopamine inhibitor • Most natural stimulation • Uses full HPG axis

More Related