Acoustic Behavior and Reproduction in Five Species of Corydoras Catfishes (Callichthyidae).
Individual fishes (n = 122) were obtained through the pet trade as juveniles and raised to sexual maturity. The mean number of individuals per group was 10 (range 3-15). C. paleatus juveniles were born in captivity while others were wild caught. All fishes were similar in length and weight. Five species (10 groups) were kept in 20-gallon aquaria in a soundproof room (Acoustic Systems Inc.). The acoustic behavior of adults was monitored using a hydrophone (BioAcoustics Inc., frequency response 10-3000 Hz, sensitivity at 10 psi of -162 dBv//[micro]Pa [+ or -] 2 2.0 dB) and amplifier-speaker (frequency response 100 Hz-10,000 Hz). The average monitoring time for each species was 10 months (range 6-15 months). Sounds were recorded on videotape with a Panasonic VHS recorder (professional/industrial model AG-180, frequency response 100-8000 Hz).
The behavioral context for each sound produced was determined by observing behavior, beginning with feeding, at night using a red light. The mean number of hours sampled per species was 50 (19-77). Five species (C. aeneus, C. arcuatus, C. leopardus, C. paleatus, C. reticulatus) were stimulated into reproductive activity by simulating a tropical freshwater rainy season (6). For reproductive fishes, the total number of 1-h samples was 81 and the mean number of hours sampled per species was 10 (6-25). Groups were maintained in non-reproductive condition by using a dry-season simulation (6). For non-reproductive fishes, the total number of 1-h samples was 171 and the mean number of hours sampled per species was 34 (5-63). Chi-square was used to test for differences in sound production between reproductive and non-reproductive fishes for all groups and samples. Student's t test was used to compare acoustic activity immediately preceding and following spawning for five groups that each had more than 10 individuals per group.
The software package SIGNAL (Engineering Systems Inc., Belmont, MA) was used to determine total pulse number and frequency range. These acoustic parameters are believed to be of significance to fishes in intraspecific contexts (7, 8). A minimum of 40 courtship sounds per species were analyzed for determining pulse number for C. aeneus, C. leopardus, and C. paleatus (177 sounds total). A minimum of 30 sounds per species for agonistic chase sounds were analyzed for the same three species (90 total). A minimum of 6 agonistic pre-chase sounds were analyzed for C. arcuatus and C. reticulatus (total 18). For startle sounds, a minimum of three sounds were analyzed for C. leopardus and C. aeneus (8 total).
[TABULAR DATA FOR TABLE I OMITTED]
Sounds were grouped as one of four types based on the behavioral context in which they were observed: (1) courtship, (2) agonistic chase, (3) agonistic pre-chase, and (3) startle. Fish activities without sound production included schooling, resting on the substrate, or testing the substrate with barbels. Courtship-associated sounds were high-pitched "creaks" (600-8000 Hz) produced when, prior to spawning, males hovered near females beating pectoral and dorsal fins. All five species produced these sounds when reproductive. The pulse number per sound ranged from 10 to 112. Agonistic chase sounds were high-pitched creaks (600-8000 Hz) produced when males chased both other males or females. These sounds were only observed several days before, during, and after spawning and consisted of 2 to 16 pulses. All five species produced these sounds when reproductive. Agonistic prechase sounds were low-pitched "wooden claps" (430-750 Hz) consisting of 2 to 6 pulses. They were produced when two individuals hovered near each other and a chase ensued. This sound was observed in C. arcuatus and C. reticulatus. Startle sounds were high-pitched "creaks" (600-8000 Hz). They consisted of 26 to 100 pulses and were produced when fishes, reproductive and non-reproductive, were resting on the substrate and suddenly scattered across the bottom or into the water column. The number of 1-h samples that included sound production was higher for reproductive (63% of 81 1-h samples) than non-reproductive (22% of 171 1-h samples) fishes. The range of percentages of 1-h samples in which fishes were acoustically active was 43% to 71% for reproductive animals and 10% to 40% for non-reproductive animals. These differences were significant (Chi-square, P [less than] 0.001). The two 1-h sample periods with the highest number of sounds were from reproductive fishes (120 and 185 sounds). All other reproductive-period samples ranged between 1 and 75 sounds per hour. Non-reproductive samples ranged from a total of 1 to 4 sounds per hour. Significantly more sounds were produced when fishes were reproductive than non-reproductive (Table I).
The results of this study suggest that (1) Corydoras catfishes produce sounds in four behavioral contexts; and (2) acoustic activity is low for non-reproductive fishes and significantly higher for the same individuals when they are reproductive.
1. Pfeiffer, W., and J. F. Eisenberg. 1965. Z. Morph. Oekol. Tiere 54: 669-679.
2. Kaatz, I. M., and D. S. Stewart. 1995. Am. Zool. 35(5): 16a. (abstract).
3. Fine, M. L., J.P. Friel, D. McElroy, C. B. King, K. E. Loesser, and S. Newton. 1997. Copeia: 777-790.
4. Kaatz, I. M., and D. J. Stewart. 1997. J. Morphol. ICVM-5 232(3): 272. (abstract).
5. Ladich, F. 1997. Bioacoustics 8: 185-191.
6. Kaatz, I. M, 1999. Ph.D. Dissertation, State University of New York, College of Environmental Science and Forestry, Syracuse, NY. Pp. 80-112.
7. Myrberg, A. A. 1981. Pp. 395-424 in Hearing and Sound Communication in Fishes, W. N. Tavolga, A. N. Popper, and R. R. Fay, eds. Springer-Verlag, New York.
8. Hawkins, A. D. 1986. Pp. 129-169 in Behavior of Teleost Fishes, T. J. Pitcher, ed. Chapman and Hall, London.
9. Pruzsinsky, I., and F. Ladich. 1998. Environ. Biol. Fishes 53: 183-191.
10. Kroodsma, D. E., and E. H. Miller. 1996. Ecology and Evolution of Acoustic Communication in Birds. Cornell University Press, Ithaca, NY. Pp. 136-177.
|Printer friendly Cite/link Email Feedback|
|Author:||Kaatz, Ingrid M.; Lobel, Phillip S.|
|Publication:||The Biological Bulletin|
|Date:||Oct 1, 1999|
|Previous Article:||Sharpening of Directional Auditory Input in the Descending Octaval Nucleus of the Toadfish, Opsanus tau.|
|Next Article:||Courtship Sounds of the Pacific Damselfish, Abudefduf sordidus (Pomacentridae).|