Live CT imaging of sound reception anatomy and hearing measurements in the pygmy killer whale, <i>Feresa attenuata</i>

Montie, Eric W.; Manire, Charlie A.; Mann, David A.

doi:10.1242/jeb.051599

Cited by 19 publications

(18 citation statements)

References 66 publications

(108 reference statements)

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“…The large mandibular canals in protocetids and basilosaurids indicate the presence of a mandibular fat body similar to that of modern odontocetes. The fat body of odontocetes has an acoustic impedance close to that of seawater (22) and functions as a wave guide, conducting underwater sound received via vibration of the pan bone and through the mandibular foramen to the auditory bulla (10,(22)(23)(24).…”

Section: Resultsmentioning

confidence: 99%

Cranial asymmetry in Eocene archaeocete whales and the evolution of directional hearing in water

Fahlke¹,

Gingerich²,

Welsh

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Eocene archaeocete whales gave rise to all modern toothed and baleen whales (Odontoceti and Mysticeti) during or near the Eocene-Oligocene transition. Odontocetes have asymmetrical skulls, with asymmetry linked to high-frequency sound production and echolocation. Mysticetes are generally assumed to have symmetrical skulls and lack high-frequency hearing. Here we show that protocetid and basilosaurid archaeocete skulls are distinctly and directionally asymmetrical. Archaeocete asymmetry involves curvature and axial torsion of the cranium, but no telescoping. Cranial asymmetry evolved in Eocene archaeocetes as part of a complex of traits linked to directional hearing (such as pan-bone thinning of the lower jaws, mandibular fat pads, and isolation of the ear region), probably enabling them to hear the higher sonic frequencies of sound-producing fish on which they preyed. Ultrasonic echolocation evolved in Oligocene odontocetes, enabling them to find silent prey. Asymmetry and much of the sonic-frequency range of directional hearing were lost in Oligocene mysticetes during the shift to lowfrequency hearing and bulk-straining predation.Cetacea | land-to-sea transition M ost mammals have bilaterally symmetrical skulls. Symmetrical crania characterize the artiodactyls closely related to whales, and symmetrical crania characterize mysticetes within Cetacea (1) (Fig. 1A). Odontocetes are exceptional because most odontocete crania are asymmetrical, with dorsal cranial bones shifted posteriorly and to the left side (1-8). Living odontocetes have a hypertrophied melon, nasal sacs, and phonic lips used to produce high-frequency sound (> 20 kHz) (9-11). Mysticetes lack these specializations of the nasal apparatus, use low-frequency sound (11,12), and may use the larynx (13) to produce lowfrequency sound. Coupling of high-frequency echolocation with facial and cranial asymmetry in living odontocetes, and the absence of both in living artiodactyls and living mysticetes, make it reasonable to expect that asymmetry originated in odontocetes (5-7). However, it is unresolved how the cranial asymmetry of odontocetes evolved in the transition from archaeocetes to modern whales, and the history becomes even more complex when archaeocetes themselves are considered.Eocene archaeocete whales gave rise to all modern toothed and baleen whales during or near the Eocene-Oligocene transition (14-16). Archaeocetes were previously thought to have symmetrical skulls (3, 5, 7). Asymmetry observed in fossil crania has often been assumed to be an artifact of deformation following burial, and it has been ignored or even removed in published drawings [as was done initially for three of the skulls we studied (17-19)]. ResultsHere we document and quantify asymmetry in archaeocete crania. Further observations on exceptionally well-preserved archaeocete crania and dentaries suggest a link between cranial asymmetry and the ability to locate sound sources in water.We quantified midline suture deviation, δx, from a straight rostrocaudal axis [RC, after Ness...

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Section: Resultsmentioning

confidence: 99%

Cranial asymmetry in Eocene archaeocete whales and the evolution of directional hearing in water

Fahlke¹,

Gingerich²,

Welsh

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…Hearing can be studied electrophysiologically by noninvasively measuring the auditory brainstem response (ABR) [17,18], which has been used extensively to address many aspects of auditory processing in cetaceans [19][20][21][22]. One can record the ABR elicited by transient acoustic stimuli with contact electrodes on the body surface and average these time-locked to the stimulus onset to reduce the influence of independent additive noise.…”

Section: Introductionmentioning

confidence: 99%

Keeping returns optimal: gain control exerted through sensitivity adjustments in the harbour porpoise auditory system

Linnenschmidt

Beedholm

Wahlberg³

et al. 2012

Proc. R. Soc. B.

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Animals that use echolocation (biosonar) listen to acoustic signals with a large range of intensities, because echo levels vary with the fourth power of the animal's distance to the target. In man-made sonar, engineers apply automatic gain control to stabilize the echo energy levels, thereby rendering them independent of distance to the target. Both toothed whales and bats vary the level of their echolocation clicks to compensate for the distance-related energy loss. By monitoring the auditory brainstem response (ABR) during a psychophysical task, we found that a harbour porpoise (Phocoena phocoena), in addition to adjusting the sound level of the outgoing signals up to 5.4 dB, also reduces its ABR threshold by 6 dB when the target distance doubles. This self-induced threshold shift increases the dynamic range of the biosonar system and compensates for half of the variation of energy that is caused by changes in the distance to the target. In combination with an increased source level as a function of target range, this helps the porpoise to maintain a stable echo-evoked ABR amplitude irrespective of target range, and is therefore probably an important tool enabling porpoises to efficiently analyse and classify received echoes.

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“…Their results were compared to similar data from a live-stranded pygmy killer whale (animal #7) from the Caribbean (RodriguezLopez & Mignucci-Giannoni, 1999) and to average blood parameters taken from a rescued live pygmy killer whale (animal #8) in rehabilitation at Mote Marine Laboratory and Aquarium in Florida (unpub. data from case reported in Montie et al, 2011). This adult male stranded on 16 June 2008 with a second male (animal #9) and underwent rehabilitation for 5 mo.…”

Section: Discussionmentioning

confidence: 99%

“…In June 2008, two pygmy killer whales stranded live near Boca Grande, Florida, and were taken into rehabilitation. Montie et al (2011) examined the peripheral anatomy of the auditory system and hearing sensitivity. Although both animals died after several months, one appeared healthy enough to provide relatively normal values for comparison purposes (C. Manire, previously unpub.…”

Section: Introductionmentioning

confidence: 99%

Biological Data of Pygmy Killer Whale (Feresa attenuata) from a Mass Stranding in New Caledonia (South Pacific) Associated with Hurricane Jim in 2006

Clua¹,

Manire²,

Garrigue³

2014

Aquat Mamm

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Despite its distribution throughout the tropics and subtropics, the pygmy killer whale (Feresa attenuata) is one of the most poorly known species of odontocetes (Cetacea: Delphinidae). We used the opportunity of a mass stranding of six animals in New Caledonia (early February 2006) to gather information about their biology. Four animals, including three males and one female, were found dead, and morphometrics, including dental counts, were collected. Two live mature males of 236 and 246 cm total length (TL), respectively, were closely monitored and sampled via blood analysis. As it was not likely to survive, the second animal was euthanized and necropsied. Following the euthanasia of the larger animal, the smaller one, which was probably staying out of social solidarity, returned on its own to the open sea. The necropsy revealed the presence of cardiopulmonary collapse and enlarged and congested testes. Blood parameters confirmed a deteriorating health status for both animals, enhanced by starvation. Some of the relative morphometric measurements of all six stranded pygmy killer whales seemed to be larger for these animals living in the southwest Pacific as compared to the literature for this species. We hypothesize that this group of pygmy killer whales was probably pushed through the Coral Sea toward the New Caledonian lagoon by Hurricane Jim, which occurred in the area from 26 January until 2 February. These observations reveal January as a potential part of the mating season in this area for this rare, elusive, and unknown species. It also supports the notion that early sacrifice of distressed, terminal animals could be a way to improve the survival rate of other less traumatized individuals during cetacean mass strandings.

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Live CT imaging of sound reception anatomy and hearing measurements in the pygmy killer whale, Feresa attenuata

Cited by 19 publications

References 66 publications

Cranial asymmetry in Eocene archaeocete whales and the evolution of directional hearing in water

Cranial asymmetry in Eocene archaeocete whales and the evolution of directional hearing in water

Keeping returns optimal: gain control exerted through sensitivity adjustments in the harbour porpoise auditory system

Biological Data of Pygmy Killer Whale (Feresa attenuata) from a Mass Stranding in New Caledonia (South Pacific) Associated with Hurricane Jim in 2006

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