Full Description

"We now report that electrical stimulation of the forebrain of the oyster toadfish (Opsanus tau) readily evokes both the agonistic grunt and the courtship boatwhistle."

"Evoked sounds form a continuum from knock grunts, burst grunts, transition boatwhistles to complete boatwhistles; sound pressure level (SPL), fundamental frequency and duration increase consistently within the continuum. For all sound types, SPLs exhibit the smallest variation (coefficients of variation of 2.7 to 5.7% ), fundamental frequency is intermediate (5 to 13%) and durations vary most widely (18 to 60%)."

"Both male and female toadfish are capable of producing the grunt call (Gray and Winn 1961), which is indicative of warning, fear, or aggravation (Fish 1954; Tavolga 1958; Gray and Winn 1961; Fish and Mowbray 1970). The grunt varies from a single short duration pulse to a series of pulses and has a fundamental frequency of 90 to 100 Hz (Fish 1954; Tavolga 1958). Rapid series of grunt pulses are sometimes called a growl. The boatwhistle, which is produced only by nesting males in nature (Gray and Winn 1961), has a higher fundamental frequency (commonly over 200 Hz) and a longer duration than the grunt (Tavolga 1958; Fine 1978). It is unusual for a fish sound because it is tonal instead of pulse-like (Winn 1964, 1972; Fine et al. 1977)."

"Sounds categorized as grunts were divided into two groups, knock grunts (Fig. 3A-D) and burst grunts (Fig. 3E-F) as described by Fine (1979). Knock grunts consist of short pulses and sound like knocks, whereas burst grunts have a longer duration and shorter intervals between pulses and sound more growl-like. Knock grunts had SPLs of 68 to 88 dB (mean of 78 dB), fundamental frequencies of 120 to 180 Hz (mean 153 Hz) and durations of 9 to 30 ms (mean of 17 ms) (Table 1). Although there were minor overlaps between them (Fig. 4), two general modes of knock grunts were identified: 1) short (9-19 ms) with a weak SPL (68-83 dB, mode of 76 dB; Figs. 3A and 4 top), and 2) long (20-30 ms) with a higher SPL (78-88 dB, mode of 84 dB; Figs. 3B and 4 bottom). Weak knock grunts were typically the first sounds in evoked sequences and commonly preceded boatwhistles (Fig. 6B, E), although boatwhistles were also preceded by high SPL knock grunts (Fig. 6C). The high SPL knock grunts typically occurred in a series of 3 to 6 pulses (Fig. 3B), although single knocks were also evoked. Combinations of both types of knock grunts (Fig. 3C-D) were also commonly evoked and were usually produced in series of 2 to 5 pulses with weak knocks preceding high knocks. Grunts were also produced following stimulus termination (after responses). Although their durations were more equally divided between long and short (Fig. 5, right panel), after responses consisted predominantly of individual high knock grunts (Fig. 3G). A train of 22 spontaneous knock grunts (i.e. not electrically stimulated) produced by one fish (Figs. 3I, 5) was used for comparison with evoked grunts. SPL, fundamental frequency and duration (Fig. 5) increased from stimulus bound to after response to spontaneous knock grunts. SPLs and durations of stimulus bound grunts were bimodal with a large population of weak and short (68-83 dB and 9-19 ms) grunts and a smaller mode of more intense and longer ones. Many of the weak grunts in the first mode preceded boatwhistles. After responses included both modes with a greater percent of the high SPL grunts, and the spontaneous grunts were almost completely high level. Burst grunts were rapid series of approximately 5-20 long duration pulses (Fig. 3E-F), which were difficult to distinguish. In fact burst grunts sometimes gave the appearance of a series of knock grunts in which the individual knocks became more (Fig. 3F) or less (Fig. 3E) fused together. Although all fish produced knock grunts, only 8 produced both types of grunts. Burst grunts had SPLs of 80-94 dB (mean of 87 dB), fundamental frequencies of 150 to 180 Hz (mean of 159 Hz), and durations of 39 to 300 ms (mean of 133 ms) (Table 1). Fundamental frequencies of knock and burst grunts overlapped considerably except at the low frequency end. Duration of burst grunts averaged 133 ms or about 8 x longer than knock grunts. The longest knock grunt (30 ms) did not overlap the shortest burst grunt (39 ms). SPLs of burst grunts averaged over 8 dB more than knock grunts and were closer to SPLs for boatwhistles, and like boatwhistles, they were commonly preceded by knock grunts (Fig. 3E, F). Compared to grunts, the toadfish boatwhistle is characterized by a higher fundamental frequency, longer duration, and tonality."

"Natural boatwhistles typically have a short initial grunt portion (Fig. 6H), but many of the boatwhistlelike sounds evoked in this study (i.e. transition boatwhistle) had a long introductory grunt portion. In a sample of spontaneous boatwhistles recorded from nesting males in the York River, Virginia (Table 2), the initial grunt portion comprised 16% to 25% of the total sound (20.4 +- 0.7%, mean +- standard error), with the exception of one boatwhistle with a grunt portion of 53% (Fig. 6D)."

"Power spectra for the evoked and spontaneous transition boatwhistle (Fig. 7C, D) had a major low frequency component and a less well defined harmonic structure because of the extended initial grunt portion. Of the 144 evoked boatwhistles, 119 (83%) were classified as transition boatwhistles and 25 as complete boatwhistles (Table 1). For complete boatwhistles, SPLs averaged 91 dB, fundamental frequencies 218 Hz, and durations 222 ms (Table 1). Transition boatwhistles were modestly lower in SPL (88 dB), substantially lower in fundamental frequency (196 Hz) and equivalent in duration (220 ms)."

"Sounds which were electrically evoked during this study were quantified for comparisons with spontaneous sounds recorded from York River toadfish. As indicated by sonagrams and power spectra, grunts and boatwhistles evoked by electrical stimulation are similar to spontaneous sounds (Figs. 3, 6, and 7). Additionally, measurements of SPL, fundamental frequency, duration and interval between calls permit quantitative comparisons between evoked and spontaneous sounds."

"Historically, grunts have been described as ranging from individual pulses to raucous growls, an imprecisely defined term for a rapid series of pulses, with fundamental frequencies in the range of 90 to 110 Hz (Fish 1954; Tavolga 1958). Fundamental frequencies evoked in this study were considerably higher, varying from 120 to 180 Hz, which is similar to the range of 100 to 185 Hz for spontaneous grunts of York River fish (Waybright et al. 1990)."

"Growls have been considered agonistic calls (Fish 1954; Gray and Winn 1961), but we interpret our longest burst grunts (see Fig. 3F) as suggestive of a mating rather than an agonistic call."

"SPLs of grunts evoked in this study varied over an extended range of 26 dB, similar to Waybright's et al. (1990) value of 30 dB for spontaneous grunts."

"Fine (1978) found that fundamental frequency varies seasonally from under 150 Hz to about 250 Hz and durations from under 120 ms to over 350 ms. Mean peak season values would be over 200 Hz and 270 ms respectively."

Observation Environment Quotes

"Oyster toadfish (Opsanus tau) captured in the York River were maintained in aquaria containing half strength sea water (Instant Ocean). The fish were anesthetized with tricaine methanesulfonate (MS 222) and clamped into a plexiglass stimulation tank with the top of the skull above water."

Behaviour Description Quotes

"We now report that electrical stimulation of the forebrain of the oyster toadfish (Opsanus tau) readily evokes both the agonistic grunt and the courtship boatwhistle."

"Both male and female toadfish are capable of producing the grunt call (Gray and Winn 1961), which is indicative of warning, fear, or aggravation (Fish 1954; Tavolga 1958; Gray and Winn 1961; Fish and Mowbray 1970)."

"In this study, we used electrical stimulation of the forebrain of the oyster toadfish, particularly the preoptic area, to identify centers involved in the control of mating call production."

" Growls have been considered agonistic calls (Fish 1954; Gray and Winn 1961), but we interpret our longest burst grunts (see Fig. 3F) as suggestive of a mating rather than an agonistic call."

Sound Name Quotes

"We now report that electrical stimulation of the forebrain of the oyster toadfish (Opsanus tau) readily evokes both the agonistic grunt and the courtship boatwhistle."

"Evoked sounds form a continuum from knock grunts, burst grunts, transition boatwhistles to complete boatwhistles; sound pressure level (SPL), fundamental frequency and duration increase consistently within the continuum. For all sound types, SPLs exhibit the smallest variation (coefficients of variation of 2.7 to 5.7% ), fundamental frequency is intermediate (5 to 13%) and durations vary most widely (18 to 60%). "

" The grunt varies from a single short duration pulse to a series of pulses and has a fundamental frequency of 90 to 100 Hz (Fish 1954; Tavolga 1958). Rapid series of grunt pulses are sometimes called a growl."

"It is unusual for a fish sound because it is tonal instead of pulse-like (Winn 1964, 1972; Fine et al. 1977)."

"Natural boatwhistles typically have a short initial grunt portion (Fig. 6H), but many of the boatwhistlelike sounds evoked in this study (i.e. transition boatwhistle) had a long introductory grunt portion."