1. Evolution of dynamic signaling Philip Stoddard & Michael Markham Dept. Biological Sciences Florida International University Dr. Michael Markham

2. Other contributors from the lab Dr. Cheryl Franchina Susan Allee Our Sponsors National Institutes of Health National Institutes of Health NIGMS MBRS, NINDS, NIMH, NHLBI NIGMS MBRS, NINDS, NIMH, NHLBI Justin Tackney Anya Goldina Vicky Salazar

3. Evolution of a new communication system

4. lust anger fear ennui hunger What evolutionary changes allows a signal to communicate state, motivation, & emotion? sex size condition endurance strength

5. Part 1 Constraints and historic response to sensory drive

6. Classic model restraint elaboration Predation & Physiological costs SexualSelection

7. Sexual Selection Multiplicative costs of natural selection (e.g., predator density or energetic cost) Cost gradient model showy or costly cryptic or low cost compromise

8. Sexual Selection Predator density Cost gradient model Photos by K. Hughes, K. McGhee, and C. Gibson Compromise line

9. Sexual Selection Multiplicative costs of natural selection (e.g., predator density or energetic cost) Dynamic signaling can escape constraints showy or costly cryptic or low cost dynamic compromise

10. Fixed signals structural colors & pigments expensive ornaments weapons Dynamic signals active displays transient signals (calls & songs) Dynamics: on / off variable magnitude variable spectrum Can also convey transient states of motivation or emotion. Convey genetic or developmental quality, and condition.

11. Why most fish make electricity 1.Seeing in the dark (they are nocturnal)

12. Why most fish make electricity Electric courtship songs 1.Seeing in the dark 2.Communicating in the dark

13. Electric Organ Discharge = EOD EOD fixed by physiology of excitable membranes in the electrocyte. electrocyteEOD waveformelectric field

14. Development of electrocytes Myocytes fuse in development to form electrocytes Shape changes, 2nd phase appears C. Franchina & P. Stoddard

15. The EOD MACHINE Recording calibrated electric signals around the clock

16. Recording EODs in free-swimming fish Stoddard, Markham, Salazar 2003 J. Exp. Biol www

17. Salazar & Stoddard subm Signal costs: EOD energetics Pharmacological partitioning of the energy budget

18. O 2 consumption ≈ energetic cost Salazar & Stoddard subm

19. Male EOD energy expense (VO 2 ) is condition-dependent Salazar & Stoddard subm

20. Physiology adapted from Dunning 1973 Shumway & Zelick 1988 The classic sensory dilemma: Ampullary electroreceptor system is used by females in mate choice & by predators for finding prey

21. Tuberous Ampullary Yes No Yes

22. Low frequency (ampullary) content of synthetic courtship signals is critical for spawning based on Hagedorn (1986) no spawning elicits spawning

23. Problem predators - catfish & electric eel electrogenic too electroreceptive phylogeny after Lauder & Leim 1983

24. ~12 million years before Star Trek electric fish evolved active cloaking to conceal their signals from predators “In several science fiction universes, a cloaking device is an advanced stealth system which causes a spaceship or individual to be invisible and extremely difficult to detect with normal sensors. However, the idea of a cloaking device could be extended to any object and is not restricted simply to spacecraft.” Wikipedia

25. compensatory pulse 2 ways to cloak an EOD DC offset current 0 v

26. Power Spectra EOD Waveforms EOD symmetry suppresses low frequency energy Biphasic EOD 1st phase alone 1 ms

27. Ask a predator Does electric cloaking really work?

28. Power Spectra EOD Waveforms Playback to Sparky the electric eel an electroreceptive predator Approach Frequency Biphasic EOD 1st phase alone 1 ms 0.25 0.67 (p=0.01, Fisher exact test) Stoddard 1999 Nature

29. Phylogeny from Albert et al. 1998 Cloaking evolved 4X in gymnotiforms

30. Brachyhypopomus pinnicaudatus waveform symmetry develops for cloaking then is lost in males 1 ms 17 days 17 days 30 days 30 days 50 days 50 days 110 days sexualmaturity

31. Spectral consequences of asymmetry

32. Sexy signals make happy catfish Thursday eveningFriday morning p = 0.067

33. Attractive to catfishNOT attractive to catfish adapted from Hanika & Kramer 2000 “eat me”

34. Part 2: dynamic control of the EOD Social signaling Cloaking & energy conservation Cryptic electrolocation Enhancement

35. Only these taxa modulate their EOD waveforms Markham, Goldina, Stoddard in prep Consensus phylogeny from Albert et al. 1998

36. Dynamic regulation of the EOD 0% 500% 1000% 2000% 1500% 2500% % incr.

37. Male B. pinnicaudatus cloaks his signal by day and uncloaks it at night EOD waveformEOD spectrum Stoddard 2002 Adv Study Behav

38. amplitude duration of 2nd phase time constant = tau P2 Tau P2, a useful metric

39. Male circadian rhythms are stronger (males reveal more, cloak less) Stoddard, Markham, Salazar, Allee in press. males females days tau P2

40. Enhancement of male EOD depends on his relative status smaller EOD male, strong enhancement male w/ larger EOD, no enhancement 0.1 ms Salazar & Stoddard in prep tau P2 Fish added to tank: 24 h

41. EOD enhanced in minutes by social stress tau-P2 (ms) time of day 2nd fish placed in tube 2nd fish removed Stoddard, Markham, Salazar 2003 J. Exp. Biol

42. Handling stress enhances the EOD Markham & Stoddard 2005 J Neurosci tau P2

43. What evolutionary change connected the EOD to so much information? Body condition Circadian state Relative social status Social stress Physiological stress

44. At night all fish are gray

45. Our hypothesis: Dynamic EOD control adapted from the skin pigmentation control system. Logan et al. 2006 Cebra-Thomas 2001 Melanocortin peptide hormones (  -MSH & ACTH) darken melanophores by dispersing melanosomes.

46. B. pinnicaudatus electrocytes express mRNA of melanocortin receptors (MCRs) Touchdown gradient RT-PCR with degenerate primers for MCR family Tackney & Stoddard unpubl electrocytesbrain 580 base pair product

47. 1000x bootstrap of nearest-neighbor joining tree of all published melanocortin receptor sequences. Cloned products indicated by dots. Tackney & Stoddard unpubl MC5RMC3RMC4RMC1RMC2R

48. MCR5 amino acid sequences Tackney & Stoddard unpubl Sequence homology > 80%

49. baseline ACTH injected Markham, Goldina, Stoddard in prep Consensus phylogeny from Albert et al. 1998 Melanocortins do it

50. Markham, Goldina, Stoddard in prep MC ?? CR

51. Melanocortins work directly on electrocytes EOD from a single cell in a dish Markham & Stoddard 2005 J Neurosci baseline ACTH

52. Androgen potentiates melanocortin action Allee, Markham, Stoddard in prep.

53. The rest of the pathway (for another talk) Serotonin (5-HT) 5HT1AR & 5HT2AR CRF & TRH [CRFxR] ACTH &  MSH MCR5 Adenylyl cyclase cAMP Protein Kinase A Na+, K+ channels hypothalamus pituitary periphery (electrocytes)

54. MSH melanocortins are body fat signals in vertebrates - work with leptin & NPY MC5R EOD   MSH &  MSH MC4R Appetite  Lipolysis  MC3R

55. Neuroendocrine cascade of dynamic EOD enhancement & cloaking Social environment Brain Serotonin GnRH CRF / TSH LH ACTH /  -MSH Brain Serotonin GnRH CRF / TSH LH ACTH /  -MSH Electrocytes Melanocortin receptor 5 Cyclic AMP (cAMP) Protein kinase A (PKA) Phosphorylatable ion channels Electrocytes Melanocortin receptor 5 Cyclic AMP (cAMP) Protein kinase A (PKA) Phosphorylatable ion channels Testes Androgens Testes Androgens

56. Components shared with the vertebrate skin pigmentation control system Social environment Brain Serotonin GnRH CRF / TSH LH ACTH /  -MSH Brain Serotonin GnRH CRF / TSH LH ACTH /  -MSH Electrocytes Melanocortin receptor 5 Cyclic AMP (cAMP) Protein kinase A (PKA) Phosphorylatable ion channels Electrocytes Melanocortin receptor 5 Cyclic AMP (cAMP) Protein kinase A (PKA) Phosphorylatable ion channels Testes Androgens Testes Androgens

57. Components shared with the mammalian preputial aggression/sex pheromone system Social environment Brain Serotonin GnRH CRF / TSH LH ACTH /  -MSH Brain Serotonin GnRH CRF / TSH LH ACTH /  -MSH Electrocytes Melanocortin receptor 5 Cyclic AMP (cAMP) Protein kinase A (PKA) Phosphorylatable ion channels Electrocytes Melanocortin receptor 5 Cyclic AMP (cAMP) Protein kinase A (PKA) Phosphorylatable ion channels Testes Androgens Testes Androgens

58. Sexual Selection Multiplicative costs of natural selection (e.g., predator density or energetic cost) 1.What happened: Sensory conflicts were partially resolved by dynamic regulation of fixed-trait signals showy or costly cryptic or low cost dynamic compromise

59. 2. Favored hypothesis of how dynamic communication evolved: Expression of ancient MC5R gene allows EOD to communicate state, motivation, & emotion

60. Postdoc and graduate study opportunities available.