Electric pulses during mating in Clarias macrocephalus

[bekateen]

Olshanskiy, V. M., Kasumyan, A. O., & Moller, P. (2019). On mating and function of associated electric pulses in Clarias macrocephalus (Günther 1864): probing an old puzzle, first posed by Charles Darwin. Environmental Biology of Fishes, 1-16. https://doi.org/10.1007/s10641-019-00936-w

https://link.springer.com/article/10.10 ... 19-00936-w

Abstract
The Asian broadhead walking catfish (

Clarias macrocephalus

) generates weak electric monopolar pulses during spawning. Males emit a single pulse when attracting a female, and while in amplexus, only females emit a single burst of similar pulses. This burst is a necessary component in the mating ritual of C. macrocephalus. Release of milt occurs about 5 s prior to the onset of a burst, which is immediately followed by the release of eggs. Following sperm release, the male remains in tight embrace with the female. Though both male and female could perceive each other’s electric pulses via ampullary receptors (communication mode), we postulate that egg release can be facilitated by direct action of the female’s burst on the male’s neuromuscular system (contraction mode). Shedding light on the function of weak episodic electric emission, we propose that the modification of electrogenic structures evolved towards increasing the efficiency of direct bodily impact. As extant clariids exhibit intermediate features between non-electric and strongly electric catfishes, Clarias should be considered a “serviceable transition,” which Charles Darwin deemed a possible intermediate form between these two groups.

• Keywords: Clarias macrocephalus, Spawning behavior, Electric fish, Episodic electric pulses, Mating ritual, Pulse-induced muscle contraction

Figure 2

Fig. 2. Sequence of fish positions before and during courtship and mating. a, Before first courtship attempts, male and female lying motionless and separated on the bottom of the tank. The female is easily identified by her large bloated stomach; b, male attracted to female, but fish have not come into close contact; c, male is slightly bending his body in front of the female’s head; d, male bending his body in a U-shaped posture and female entering into the male’s U-shaped body bend; e, position of fish entered into amplexus; f, female turns to the front part of his body in the opposite direction from the head of the male; g, position of fish at the moment of egg release; h, position of fish at the end of amplexus