Agonistic behaviour and sound production in Gaidropsarus mediterraneus, (Gadidae)

Agonistic behaviour and sound production were described for captive Gaidropsarus mediterraneus , a shore-dwelling gadoid. Thump-like sounds were produced during agonistic interactions, which involved disputes over access to shelter sites.     

Spawning Sounds of the Male Haddock, Melanogrammus aeglefinus

The codfish family, Gadidae, contains many vocal species. The sounds produced are species-characteristic and relatively simple. Unusually within this family, the haddock Melanogrammus aeglefinus, produces a range of sounds in different contexts. Both male and female haddock produce short sequences of repeated knocks during agonistic encounters. During the spawning season, however, male fish produce sounds which vary in their characteristics as courtship proceeds. The repertoire of the male fish consists of a graded series of sounds ranging from a short series of slowly repeated knocks to long sounds of rapidly repeated knocks. The fastest sounds are heard as a continuous humming. Different behavioural acts leading up to the mating embrace are associated with particular sounds, the sounds becoming longer and faster as the level of arousal of the male increases. It is suggested that the sounds serve to bring male and female fish together in the same part of the ocean, and that the sounds also play a role in synchronising the reproductive behaviour of the male and female.     

Laboratory studies of the effects of short‐term isolation on aggressive behaviour in fish

A review of the literature on the effects of short‐term isolation on aggressive behaviour in a variety of fishes reveals different approaches and often conflicting results. This diversity is attributed to a number of factors, including different experimental conditions and specific differences in habitat, behavioural repertoire and social system. Some common trends are identified and the main hypotheses proposed to account for the different results are discussed. Some methodological issues as well as proximate and ultimate mechanisms are examined, and the importance of a standard experimental paradigm in comparative research emphasised.     

A unique sound production mechanism in the pipid anuran Xenopus borealis

The totally aquatic pipid frog Xenopus borealis produces long trains of click-like sound at high sound pressure levels (> 105 dB SPL) underwater at night. While X. borealis retains an essentially terrestrial respiratory tract, the larynx is highly modified in two ways. First, the cricoid cartilage is greatly expanded posteriorly to form a large 'box'. Portions of this cricoid box are composed of an unusual elastic cartilage. Second, portions of the arytenoid cartilages are elaborated into calcified rods with disc-like enlargements at their posterior ends. These discs are the only freely moveable components within the larynx–there are no vocal cords. Artificial stimulation of a pair of muscles controlling the discs and discrete lesions that impair their movement demonstrate that motion of the discs is both necessary and sufficient for click production. Unlike all other anurans, X borealis does not use a moving air column in sound production. A possible mechanism of click production involves two steps: (1) at first, the discs are held tighdy apposed in the midline by fluid adhesive forces, and contraction of bipennate muscles is isometric; (2) when the muscle tension exceeds the adhesive force, the discs separate with very high acceleration leaving a vacuum between them. Air rushing into the space at high speed (an implosion) produces the click. The cricoid box shapes the frequency spectrum of the clicks, and opening the box broadens the power spectrum. The power spectrum of clicks produced by males after breathing helium is unchanged.     

Analysis of the Stridulation in Solifuges (Arachnida: Solifugae)

Stridulation in solifuges has not been investigated yet. We performed a comparative analysis of the stridulatory organs and sounds produced by juveniles of various developmental stages and adults (both sexes) of Galeodes caspius subfuscus Birula. The stridulatory organ is of similar morphology in all developmental stages. The sound that they produced was a broad frequency hissing, composed of one or two chirps with maximum at 2.4 kHz. The intensity of the sound was found to increase with body size. Otherwise, no differences were observed between stridulation in juvenile, male and female individuals. Therefore, we suggest that the stridulation in solifuges has primarily a defensive role. As solifuges are neither venomous nor unpalatable, they might imitate an accoustically aposematic organism that shares the same habitat and has similar circadian activity, e.g. vipers. It may also have an intraspecific function in reduction of cannibalistic tendencies.     

Exocrine and endocrine secretion of renin and epidermal growth factor from the mouse submandibular glands

Renin and epidermal growth factor (EGF) are synthesized in large amounts by the male mouse submandibular glands. We report the peptides to be secreted mainly in an exocrine manner. The highest values in saliva are obtained upon stimulation with the alpha-adrenergic agonist phenylephrine. The median value for renin is 54 700 nmol/l and the median value for EGF is 211 800 nmol/l. Aggressive behaviour and beta-adrenergic stimulation also increase salivary output of both peptides, while vasoactive intestinal polypeptide (VIP) plus pilocarpine selectively stimulate the secretion of renin. The pattern of increase in plasma is comparable to that in saliva though the substance concentration is lower by a factor of 2 to 70 for renin and a factor of 280 to 12 000 for EGF.     

Elimination of sexual brood in the Argentine antLinepithema humile: queen effect and brood recognition

Mated queens of the antLinepithema humile (Iridomyrmex humilis Mayr) introduced into dequeened colony fragments rearing sexual brood elicited worker aggression resulting in queen larvae being bitten and eliminated. By contrast, male larvae were spared. Regarding queen brood, killing mainly concerned small and medium sized larvae. A large proportion of the large larvae escaped extermination, and prepupae and pupae were spared. These data suggest that workers were able to discriminate sex, caste and age of the brood. That a queen pheromone may be involved was shown by experiments using whole or cut corpses that were either rinsed or not rinsed in pentane. The pheromone eliciting worker aggressive behaviour was shown to act over a short distance, suggesting that it is somewhat volatile. Similarities and differences between this new queen pheromone and other known queen pheromones acting on queen production or worker attraction are discussed as well as the origin of the signals underlying the recognition of the larval classes.     

Sexual cannibalism in scorpions: fact or fiction?

Females of several scorpion species are currently deemed to be sexual cannibals, but this reputation is, however, largely built on anecdotal evidence from the older literature. Theoretical models predict that given the low rates of female-male encounter, males should allow themselves to be cannibalized after sperm transfer. The present paper examines the information available for a number of species to determine (a) whether sexual cannibalism is as widespread as previously suggested, and (b) whether it is likely to involve male self-sacrifice. Information on three scorpions currently regarded as sexual cannibals is presented: the bothriurids Bothriurus bonariensis (C.L. Koch) and Urophonius jheringii Pocock, and the buthid Leiurus quinquestriatus (Hemprich & Ehrenberg). No post-mating cannibalism was ever observed in these species, nor in another 19 representatives of four families. In L. quinquestriatus only two cases of cannibalism of the male by the female occurred, both in the beginning of courtship and after long periods of food deprivation. We suggest that if sexual cannibalism occurs in scorpions, it is most likely to be of an 'economic' type, where females perceive males as prey rather than mates, and not a 'self-sacrificial', post-mating cannibalism enhancing the fitness of the offspring of the male.     

Female Corncrake(Crex crex) singing in the wild

Summary The male Corncrake (Crex crex) has a characteristic mating call. In aviary it has been shown that females can also produce a call similar to the male's typical crex crex. I describe a strikingly different call produced by a female on Öland, southeast Sweden. The sex identification was based on the small size during close examination in the hand. The female call has a similar rhythm to the male call but lacks the rasping of the male and is almost a barking sound. The female was heard calling continuously at night throughout a three-week-period. Another bird producing the same call was heard about 100 m from the caught female suggesting two females in the same field. No male Corncrakes were heard in the field during the period when the female was calling. Possible explanations for this behaviour and the function of the call is discussed.

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Rufe eines weiblichen Wachtelkönigs(Crex crex) im Freiland

Zusammenfassung Männliche Wachtelkönige (Crex crex) haben charakteristische Balzrufe. In Gefangenschaft gehaltene weibliche Wachtelkönige rufen ebenfalls männchenähnlich crex crex. Dieser Artikel beschreibt einen bisher unbekannten Ruf eines weiblichen Wachtelkönigs von der Insel Öland/SE Schweden. Die Geschlechtsbestimmung erfolgte aufgrund der geringen Maße. Die Rufe des Weibchens zeigten einen ähnlichen Rhythmus wie die der Männchen, ihnen fehlt jedoch der knarrende Klang und sie klingen eher bellend. Das rufende Weibchen wurde über drei Wochen regelmäßig nachts gehört. Ein weiterer Vogel mit den gleichen Rufen wurde etwa 100 Meter neben dem gefangenen Weibchen gehört, was darauf deutet, daß es sich um zwei Weibchen in dem gleichen Feld gehandelt hat. Rufende Männchen wurden während dieser Zeit nicht gehört. Die Bedeutung dieser Weibchen-Rufe wird diskutiert.