A review of the literature reveals that, if females prefer traits that deviate from the population mean, they usually prefer traits of greater quantity. In cases in which the sensory bases of these preferences are identified, females prefer traits of greater quantity because these traits elicit greater sensory stimulation. However, two caveats apply. First, the studies surveyed might not represent an unbiased sample of mate choice, because researchers usually study systems characterized by exaggerated traits. Second, a preference for traits of greater quantity does not suggest that preference for average traits is unimportant; it might be more usual than preference for exaggerated traits. Phylogenetic comparisons sometimes allow one to distinguish among competing hypotheses for the evolution of female mating preferences. Two hypotheses, Fisher's theory of "runaway" sexual selection and the "good genes" hypothesis, predict that traits and preferences coevolve, whereas the "sensory exploitation" hypothesis ...

Directional patterns of female mate choice and the role of sensory biases

Female mate choice in treefrogs : static and dynamic acoustic criteria

Numerical competence is one of the many aspects of animal cognition that have enjoyed a resurgence of interest during the past decade. Evidence for numerical abilities in animals has followed a tortuous path to respectability, however, from Clever Hans, the counting horse, to modern experimental studies. Recent surveys of the literaturereveal theoretical as well as definitional confusion arising from inconsistent terminology for numerical processes and procedures. The term “counting” has been applied to situations having little to do with its meaning in the human literature. We propose a consistent vocabulary and theoretical framework for evaluating numerical competence. Relative numerousness judgments, subitizing, counting, and estimation may be the essential processes by which animals perform numerical discriminations. Ordinality, cardinality, and transitivity also play an important role in these processes. Our schema is applied to a variety of recent experimental situations. Some evidence of transfer is essential in demonstrating higher-order ability such as counting or “sense of number.” Those instances of numerical competence in which all viable alternatives to counting (e.g., subitizing) have been precluded, but no evidence of transfer has been demonstrated might be described as “protocounting.” To show that animals are capable of “true” counting future research will have to demonstrate generality across situations.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0140525X00053437

Numerical competence in animals: Definitional issues, current evidence, and a new research agenda.

Measuring female mating preferences

1.

The responses of fifty-eight neurons in the cricket brain to auditory stimuli were studied by intracellular recording, after which the cells were marked with Lucifer Yellow. These auditory interneurons could be assigned to three classes on the basis of anatomical criteria: (i) neurons (AN1 and AN2) ascending from the prothoracic ganglion into the brain, (ii) brain neurons (BNC 1) with arborizations overlapping those of ascending cells, and (iii) brain neurons (BNC 2) with arborizations that had no overlap with those of ascending cells.




2.

All the ascending neurons had one projection field in common, an area in the anterior dorsal region of the diffuse neuropil lateral to the alphalobe. This field overlaps one of the projection fields of the BNC 1 neurons. Other projection fields of the BNC 1 neurons are frequently found in the posterior ventral region, at the boundary between the proto and deutocerebrum; the latter overlap projection fields of the BNC 2 cells, the arborizations of which are often not clearly distributed in more than one distinct region (Figs. 1–4).




3.

The threshold curves and suprathreshold responses revealed that all three classes (AN, BNC 1 and BNC 2) include cells with low frequency (5 kHz) and others with broad-band (2–20 kHz) tuning; high-frequency (10–20 kHz) tuning was found only in AN and BNC 1 cells. Within the region to which the cells were tuned, sensitivity decreased in the order AN, BNC 1, BNC 2 (Figs. 2–4). A frequently observed property of BNC 2 neurons was independence of sound intensity in the suprathreshold intensity region. The response latency increased in the order AN, BNC 1, BNC 2 (Figs. 5, 6).




4.

The effect of stimulus temporal structure was studied by presenting ‘constant-energy-chirps’, trains of sound pulses (syllables) varying in duration and repetition interval. The low frequency AN1 neurons, like other prothoracic neurons, copy such signals over a broad range of repetition intervals. Copying by the BNC 1 neurons was less accurate, and the responses of BNC 2 neurons were often not detectably synchronized with the syllables of the stimuli (Figs. 7–10).




5.

Strikingly, the magnitude of the BNC 2 responses was in some cases (7 out of 15) found to vary with repetition interval; curves for the BNC 2 responses vs. repetition interval match closely those for the behavioral tracking response of females given an identical stimulus paradigm, and are independent of intensity at intensities 10 dB or more above threshold. By contrast, the responses of AN and most BNC 1 neurons are uniform, regardless of stimulus intensity, over the entire range of repetition intervals studied (Fig. 11).




6.

Some BNC 2 neurons responded to constantenergy chirps only with short and intermediate or with intermediate and long repetition intervals, resembling the high-pass and low-pass neurons found in frogs (Fig. 12). This finding, the systematic latency differences, and the anatomical relationships among the AN, BNC 1 and BNC 2 cells all point to a rather specific picture of the way that the male calling song is recognized.

Temporal selectivity of identified auditory neurons in the cricket brain

Comparative study of phonotactic reactions of females of 5 species of crickets to the calling song (CS) of conspecific males and different sound models in Y-maze experiments showed:

1.

InGryllodinus kerkennensis the essential property of the signal is the continuity of the song (Fig 3).




2.

InGryllus campestris andG. bimaculatus pulse rate and chirp duration are important, the former having narrow and the latter broad tuning of reaction to chirp duration (Fig. 4).




3.

InSpecies 2 (see Methods) chirp rate and pulse duration determine the specific response of females (Figs. 5 and 6).




4.

InMelanogryllus desertus the most important parameters are the mean pulse rate and the increase in amplitude of pulses within the chirps (Fig. 7).




6.

The spectrum of the CS is not important for the process of recognition as far as it falls into the tuning curve of specialized low-frequency channel of the auditory system. High-frequency sounds outside the range of this channel are not effective even if they have the same amplitude modulation pattern as the CS.

Phonotactic Behavior of Crickets

1.

A high-frequency auditory neurone (HF1AN) was identified morphologically and physiologically in the prothoracic ganglion of the cricket,Gryllus bimaculatus DeGeer.




2.

The main inputs of the HF1AN are from the lateral and medial parts of the auditory neuropile ipsilateral to the axon and to a lesser extent, the medial part of the contralateral auditory neuropile. The single axon ascends to the brain and the soma is located either near the base of the anterior connective or close to the base of nerve N1 contralateral to the axon (Fig. 1).




3.

The HF1AN is sensitive to sound stimulation in the whole range of tested (from 2 to 100 kHz) frequencies. The neurone is not tuned to a particular frequency and has greatest sensitivity in the range 13–25 kHz (Fig. 2). At frequencies below 10–12 kHz the neurone receives additional inhibitory inputs which greatly modify its response pattern from phasic-tonic with prolonged discharge to phasic with an inhibitory pause (Figs. 3–4). The inhibitory effect is intensity dependent and its frequency range varies between animals. In the range of frequencies where the inhibitory effect is pronounced, sound stimulation evokes suppression of activity during the sound pulse and increase of activity between the pulses. On the contrary, at high frequencies the cell gives a burst of spikes to each sound pulse and background activity (if present) is suppressed after each burst for at least 1–2 s (Figs. 5, 6).




4.

The HF1AN responds in a phasic-tonic manner to pure high-frequency tones of long duration (1,300 ms) throughout the whole intensity range (Fig. 7).




5.

The HF1AN responds strongly to high-frequency ticks of the courtship song of conspecific males and to the location sounds of sympatric bats (Fig. 8).




6.

Both anatomical and physiological properties indicate that the HF1AN may belong to the neuronal circuits controlling evasive behavior and/or arousal of the cricket.

Auditory interneurones in the prothoracic ganglion of the cricket, Gryllus bimaculatus

Two ventral-cord neurons in the auditory system ofGryllus bimaculatus were studied electrophysiologically by stimulation with pulses of sound at a single frequency (sine-wave pulses), stridulatory songs, and artificial sounds constructed to imitate the conspecific songs. The sine-wave pulses were varied in frequency, sound intensity, duration, and repetition rate. The stridulatory songs were the conspecific calling, aggressive, and courtship songs and the calling songs of 8 sympatric gryllids (played back at different sound intensities). The artificial songs were varied in carrier frequency, pulse rate, chirp rate, and sound intensity. The LF1 neuron precisely duplicates the temporal structure of the conspecific calling (and aggressive) song over the whole intensity range (Figs. 7, 8, 10). It is sharply tuned to the carrier frequency of the song (5 kHz) and shows little or no response above 10 kHz and below 3 kHz (Figs. 1, 2). By variation of the calling song's temporal structure it can be demonstrated that the LF1 neuron is particularly suited to respond to the pulse duration and the pulse and chirp repetition rates of this song pattern (Figs. 6, 9). On the other hand, the HF1 neuron is a broad-band neuron with a maximal sensitivity at 16 kHz (Figs. 1, 4); it is tuned to the conspecific courtship song with respect to carrier frequency, the short pulse duration, and the very low pulse repetition rate (Figs. 6, 7, 8). The results demonstrate that the two ventral-cord neurons represent highly evolved channels of the auditory pathway in gryllids, each of which transmits important features of the corresponding conspecific songs to several areas of the brain (Fig. 11). But they are not ideal filters for these conspecific songs, since they also respond to many other sound signals (Fig. 10).

Brain projections and information processing of biologically significant sounds by two large ventral-cord neurons of Gryllus bimaculatus DeGeer (Orthoptera, Gryllidae)

1.

The spontaneous song ofCicadetta sinuatipennis males consists of alternating tymbal sound production and wing-clicking (Fig. 1). The temporal and spectral characteristics of tymbal and wing sounds are unalike (Table 1, Fig. 7).




2.

Wing-clicking is the result of sudden lateral movements of the forewings. A click is generated by the outward buckling of a specialized caudal margin of a forewing which is locked in a narrow groove on the scutellum before sound production (Fig. 2).




3.

Central projections of auditory and motor fibres with axons in the tympanal and tensor nerves were shown with the help of axonal cobalt iontophoresis (Figs. 3–5). The anatomy of the large tymbal motor neuron and three tensor motor neurons with ventral cell bodies is described.




4.

Stimulus thresholds for the summed response of primary auditory fibres were measured for different sound frequencies. The resulting hearing curves show that the auditory organs have a sharp peak of sensitivity near 6–6.5 kHz. When stimulated by the natural spontaneous song of a male, the ear gives clear “on”-responses to each click of a wing sound with thresholds of about 21–31 dB SPL and very weak asynchronous reaction to tymbal sounds with thresholds of about 70 dB SPL. This is a result of the different spectral content of these sounds (Fig. 6, 7). It is suggested that wing sounds are used for long-range communication between males and females. Tymbal sounds can be used only for short-range communication or have another, possibly repellent function.

Sound production and hearing in the cicada,Cicadetta sinuatipennis osh. (Homoptera, Cicadidae)

For efficient acoustic communication precise concordance between the properties of sound signals of emitters and those of the auditory system of receivers is necessary. An extremely important parameter, the communication range, directly depends on it. So, for any species this concordance is highly “desirable”. Sound-producing and sound-receiving systems have different morphological substrate, are controlled by different genes and matching between them is established by natural selection as the result of a complicated game of different selection forces fitting the animal as a whole to definite environment. The degree of concordance between hearing and sound production vary greatly in different animals and is dependent on the presence or absence of forces working against it.

Andrej V. Popov

Papers

Phonotactic Behavior of Crickets

Auditory interneurones in the prothoracic ganglion of the cricket, Gryllus bimaculatus

Brain projections and information processing of biologically significant sounds by two large ventral-cord neurons of Gryllus bimaculatus DeGeer (Orthoptera, Gryllidae)

Sound production and hearing in the cicada,Cicadetta sinuatipennis osh. (Homoptera, Cicadidae)

Co-Evolution of Sound-Production and Hearing in Insects