THE CHROMATOPHORAL NEUROHUMORS OF THE DOGFISH

Area of Science:

• Ichthyology
• Neuroendocrinology
• Pigmentary effectors

Background:

• The common dogfish (Mustelus canis) displays dynamic color changes, with dark phases induced by pituitary secretions (hydroneurohumors) and light phases controlled neurally.
• Previous observations noted temporary light and dark color extremes in Mustelus canis.

Purpose of the Study:

• To investigate the biochemical basis of the light phase in Mustelus canis coloration.
• To identify the substance responsible for inducing light spots in dark dogfish.

Main Methods:

• Extraction of substances from light dogfish fins using olive oil or ether.
• Injection of these extracts into dark dogfish to observe color changes.
• Testing the stability of the active substance to heat and its solubility.
• Observing the effect of pituitrin on induced light spots.

Main Results:

• Injection of oil/ether extracts from light fins induced secondary light spots in dark dogfish within 1-2 days.
• These secondary light spots were reversible with pituitrin, indicating a viable biological mechanism.
• The active substance was oil-soluble (liponeurohumor), heat-stable up to 110°C, and not water-soluble.
• The substance is hypothesized to originate from nerve terminals regulating melanophore pigment.

Conclusions:

• A liponeurohumor, extracted from light dogfish fins, is responsible for inducing temporary light spots.
• This liponeurohumor likely originates from nerve terminals and influences pigment concentration within integumentary cells.
• The findings differentiate between neurologically controlled light phases and hormonally controlled dark phases in dogfish coloration.