6. 5d.AUTHORS PROJECT NUMBER 20000913 051
Form ApprovedOMB No. 0704-01-0188REPORT DOCUMENTATION PAGEThe public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources,gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collectionof information, including suggestions for reducing the burden to Department of Defense, Washington Headquarters Services Directorate for Information Operations and Reports(0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall besubject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.1. REPORT DATE (DD-MM-YYYY)2. REPORT TYPE3. DATES COVERED (From - To)Professional Paper1999 4. TITLE AND SUBTITLE5a. CONTRACT NUMBERThe Cetacean central nervous system5b. GRANT NUMBER5c. PROGRAM ELEMENT NUMBER5d. PROJECT NUMBER6. AUTHORSRidgway, Sam H.5e. TASK NUMBER20000913 0515f. WORK UNIT NUMBER7. PERFORMING ORGANIZATION NAME S) AND ADDRESS(ES)8. PERFORMING ORGANIZATIONREPORT NUMBERSpace and Naval Warfare Systems Center53560 Hull StreetSan Diego, CA 92152-50019. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)10. SPONSOR/MONITOR'S ACRONYM(S)11. SPONSOR/MONITOR'S REPORTNUMBER(S)12. DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited.13. SUPPLEMENTARY NOTES14. ABSTRACTWhales, dolphins, and porpoises, 78 species of entirely aquatic mammals, comprise the order Cetacea whose distantancestors, according to paleontologists, left land in the early Eocene about 55 to 60 million years ago. The Odontoceti (toothedwhales, presently 67 species) and the Mysticeti, 11 species of baleen whales, have evolved separately since at least the lateEocene. Modern cetaceans are diverse; the largest blue whale is some 60,000 times heavier than the smallest newborn porpoise.Average adult size among cetaceans varies by at least 1000 times. Small and large species occupy all oceans from the equator tothe polar seas, some forms also inhabit rivers, and four species live only in fresh water.Published in Elsevier's Encyclopedia of Neuroscience, 2nd enlarged and revised ed., pp. 352-358, 1999.16. SUBJECT TERMSCetaceancentral nervous system16. SECURITY CLASSIFICATION OF:17. LIMITATION OFABSTRACTa. REPORTb. ABSTRACT c. THIS PAGEuUuuu18. NUMBEROFPAGES19a. NAME OF RESPONSIBLE PERSONRidewav. Sam H. D350319B. TELEPHONE NUMBER (Include area code)(619)553-1374Standard Form 298 (Rev. 8/98)Prescribed by ANSI Std Z39.18
352The Cetacean central nervous systemThe Cetacean central nervous systemSam H. RidgwayWhales, dolphins, and porpoises, 78 species of entirely aquaticmammals, comprise the order Cetacea whose distant ancestors,according to paleontologists, left land in the early Eoceneabout 55 to 60 million years ago. The Odontoceti (toothedwhales, presently 67 species) and the Mysticeti, 11 species ofbaleen whales, have evolved separately since at least the lateEocene. Modern cetaceans are diverse; the largest blue whale issome 60,000 times heavier than the smallest newborn porpoise.Average adult size among cetaceans varies by at least 1000times. Small and large species occupy all oceans from theequator to the polar seas, some forms also inhabit rivers, andfour species live only in fresh water.1. Brain size, growth, and shapeBrain size among adult cetaceans ranges from about 200 g inan Indus River dolphin or a La Plata dolphin to a record high of9,200 to 9,300 g reported for the largest male sperm and killerwhales. Although adult male sperm whale brains average about7,800 g, the dolphin family (Delphinidae) seem to have reachedthe apex of cetacean brain:body ratio; with body size near thesame range as humans and brain weights approaching those ofthe human brains - Tursiops (Figure 1) about 1,500 g. Stenocirca 1,400 g, and Lagenorhynchus around 1.300 g.At birth, bottlenose dolphin's {Tursiops) brains are about42% of adult size, reach 80% by weaning-age at 18 months totwo years, and full development by age eight or ten.In the embryonic stage, the dolphin brain, like that of othermammals, is longer than wide. By the late fetal stage, theodontocete brain "is globular in appearance, wider than long(Figure 2). In postnatal mysticete brains, length and width aremore similar. A dolphin brain viewed from the medial aspect ofa sagittal section (Figure 3) shows that the height is also greatcompared with the length. An S-shaped curving of the neuralaxis leaves the axis of the forebrain almost perpendicular to thatof the midbrain, giving the impression that the forebrain rotatedventrally during development.The cerebral hemispheres of Cetacea are large and enormously convoluted. Odontocetes exceed humans, and all othergroups, in the complexity of the cerebral cortical pattern of gyriand sulci. A larger percentage of the dolphin cortical surfaceis buried beneath the surface of each cerebral hemisphere. Themain sulci that arch along the dorsolateral cerebral surface aredeep and incised with microgyri. Deep to the sylvian cleft liesFigure 1. Right side of head, Bottlenosed dolphin Tursiops. Avestiae of external auditory meatus, M melon.an extremely large insula consisting of radial gyri arising fanlike from the transverse insular gyrus, and covered completelyby the frontal, parietal, and temporal opercula. In a series ofTursiops, mean cortical surface area was 3745 cm2 comparedwith 2275 cm2 in a series of human brains; however, the dolphin's cortex was thinner (1.3 to 1.8 mm), and the total volumeof cortex was about 80% ofthat found in humans.2. The cerebral cortexSome histologists suggest that the whale cortex as a whole,while vast in surface area, does not appear to have reached theultimate stage of cortical evolution and retains some conservative characters seen in primitive forms such as hedgehogs andbats. Cortical layer I contains extraverted dendrites from neurons of layer II. Layer IV is incipient or at least hard to identify(perhaps with the exception of immature brains). With the absence of a typical layer IV, thalamocortical input to sensory cortex may be mainly to layer III based on cytochrome oxidase andGABA staining. Areas of cortical surface identified as primarysensory cortex"by physiological mapping studies are agranularand not distinguished as primary sensory cortex on histologicalgrounds. It has been suggested that during evolution, cetaceanshave preserved features of "initial" or "archetypal" brains ofprimitive mammals to a much greater extent than have the greatmajority of modern land mammals. A long period of evolutionFigure 2. (A) Postero-ventral and (B) Antero-ventral views of aneonate dolphin (Tursiops) brain. The dura, blood vessels, andmostcranial nerves have been removed. Neonate brains averaged 42.5% ofadult weight. OL olfactory lobe, II optic nerve, OT optic tract,VIII auditory nerve, OV olive, CB cerebellum, SF sylvianfissure, MR median raphe, calibration mark is I cm.
The Cetacean central nervous systemCC353cXREGGOPFigure 3. Sagittal section, about 1 cm to the right of median raphe of the brainstem. T tongue, GOP glandula teg.on of oropha,ynx. REGigh" skie of epHottis, SC spinal cord. CB cerebellum, PC posterior (inferior) colhculus, CC corpus callosum, Ce ce.eb.um. PNrnghtepiem4ofrontal sac, NP nasai plug. RN right nasal cavity. NPM nasal plug muscle. M melon.in a completely aquatic environment has often been cited as amajor factor in the development of cetacean brain characteristics; however, when making such suggestions one should keepin mind that the Sirenia have also been totally aquatic for 55to 60 million years and their brains are radically different relatively small and lissencephalic with a thick, highly laminated isocortex. Sirenia are slow plant caters in contrast to themost encephalized of the Cetacea which are fast upper food webpredators.According to at least two studies, the ratio of glial cells pernerve cell is'correlated directly with brain size. There is at leasta 20-fold decrease in neurone density from mouse to whale.Regressions of neurone density have a decreasing slope similarto the decreasing slope of regressions of corpus callosum sizeamong delphinid cetaceans emphasizing a likely connectionbetween the relatively small cetacean corpus callosum andneurone density.3. The brain blood supplyIn Tursiops, Delphinapterus (the white whale), and Monodon(the narwhal), and very possibly in all cetaceans, connectingvessels that make up the circle of Willis in most mammalsare absent. The subdural blood supply for each hemisphereis completely independent. Neither the internal carotids norvertebral arteries supply blood to the brain. There is novertebro-basilar system, and the internal carotid terminates atthe ear without entering the cranial vault. The entire cerebralblood supply comes through a massive thoracico-spinal retesupplied by intercostal and posterior thoracic arteries. Differentfrom the usual form in mammals, the dolphin blood-brainbarrier comprises both endothelial and glial cells forming twoconcentric rings separating blood from brain parenchyma.4. The olfactory apparatusIn early fetal stages of both mysticetes and odontocetes, theolfactory bulb, nerve, and tracts are present. As the fetusdevelops, these structures degenerate and are completely absentfrom mature odontocete brains. Olfactory tracts, but not nervesor bulbs, arc found in at least some adult mysticete brains.Although the more peripheral olfactory components of thecetacean nervous system are absent or rudimentary, other brainstructures traditionally thought to be involved in olfaction arepresent in the mature dolphin. The olfactory lobes and septalareas are large, the hippocampus and subiculum small, the welldeveloped entorhinal cortex more anteriorly located in the temporal lobe, and the presubiculum more posterior than in othermammals; however, in general, the rhinencephalon displays thesame basic structural arrangement as in primates or carnivores.The seemingly paradoxical presence of a ' nosebrain" withoutperipheral connections or sensory olfactory endings is one ofthe more interesting features of the cetacean central nervoussystem.The tiny terminal nerves that accompany the olfactory nervesin many vertebrate species are present both in fetal and inadult dolphins. The terminal nerve ganglia contain many largediameter myelinated fibers and the ganglia are grossly largerthan those seen in other mammals.Two external respiratory openings (blowholes) are present inbaleen whales and one in toothed whales. In dolphins, a singleblowhole with its muscular plug sits atop a system containingthree pairs of asymmetrical sacs below which are pairedrespiratory passages. Although there are no olfactory nerveendings, the paired external air passages and their associatedcartilage, sacs, and muscles are referred to as the nasal system.S. The gustatory senseBecause the dolphin is regarded as anosmic. and because theanimals usually swallow "fish and other food whole withoutmastication, some cetologists have doubted that the animalspossess the sense of taste. A presumed gustatory nucleus ofthe thalamus and the elaboration of the seventh and ninthcranial nerves suggested to neuroanatomists. however, that thegustatory sense is well developed.Recently, at least three histological studies have produceddescriptions of taste buds within five to eight pits that form aV-shaped row on the dolphin tongue. In one study, taste budswere found in the tongue pits of young dolphins, but not inthose of adults; in another study, a nerve supply to the buds
354The Cetacean central nervous systemcould not be demonstrated. There still seems room for doubtthat cetaceans have taste buds such as those present in manand most other mammals. Nonetheless, there appears to bepsychophysical evidence for chemoreception by sensors in thetongue or mucous membranes of the mouth since, reportedly,trained animals can detect chemicals dissolved in sea water.6. Asymmetry of the dolphin brainToothed whales, but not baleen whales, generally have astrikingly asymmetrical cranium. The blowhole is shifted tothe left of the cranial midline, and several skull and headstructures on the right are larger than those on the left. Thereis no known reversal of the family-specific asymmetries amongany individual odontocete. Several early authors also reportedasymmetries of the brain. These observations have often beendiscounted because of the possibility that such large brainsmight be liable to deformation during long periods of fixation.Recent studies of Tursiops and Delpliinus brains have shownthat not only brain size but cortical surface area is also asymmetrical. The right cerebrum is slightly larger. One plausibleexplanation was given by M.M. Sleptsov who argued in 1939that, in the embryonic state, the left olfactory nerve and lobedegenerate more rapidly than those on the right initiating a series of cerebral and cranial asymmetries.7. The visual systemThe Ganges dolphin with tiny optic nerves and small lenslesseyes is almost blind. Some other river species of dolphins alsohave small, atrophied eyes. Marine cetaceans, however, havewell-developed optic nerves and large eyes. In the bottlenosedolphin and the fin whale, rods and cones have been describedin the retina. In Tursiops, there is no distinct fovea centralis, theretina is thick, and a layer of giant ganglion cells (cell bodiesup to 150 pm in diameter) appears to serve most of the centralretina. These giant ganglion cells support giant dendrites andmyelinated optic nerve fibers that range up to 8 or 9 pm indiameter.In most mammals, each eye projects the majority of its nervefibers to the opposite cerebral hemisphere (crossed fibers);however, considerable numbers of uncrossed fibers project tothe cerebral hemisphere on the same side. Dolphins, and verylikely other cetaceans, are an exception to the general rulethat crossed and uncrossed fibers arise from each eye. Threedegeneration studies and one physiological study of evokedpotentials indicated that each of the bottlenose dolphin's eyesprojects only to the contralateral hemisphere. (One study ofthe harbor porpoise suggests only a 90% crossover.) Totaldecussation of the optic nerve across the optic chiasm is highlyatypical for mammals but common in other vertebrates. It mayalso be noteworthy that, compared with the human brain, thecetacean brain has a small corpus callosum - only one-quarteras large (Figure 4).Although the eyes of all cetaceans are widely spaced oneither side of the head, it appears that at least Tursiops has somedegree of visual overlap ventrally and rostrad as well as dorsallyand slightly caudad. Despite these small areas of overlap in thevisual field, the dolphin's eye movements are not conjugate.The dolphin corneal reflex appears well developed and thepupil reacts to light. The retractor bulbi is large, and the otherextrinsic ocular muscles are present and well developed. Theoculomotor nerves are small compared with the fifth, seventh,and eighth cranial nerves, but are by no means rudimentary.The presence of an Edinger-Westphal nucleus is questionable.Description of the oculomotor nuclei has been complicated bythe presence of a large encapsulated group of cells just dorsalto the third nucleus, the nucleus ellipticus. The function of thisFigure 4. Mid-line view of the brain of an older female bottlenosedolphin (Tursiops age about 30) showing the small corpus callosumrelative to total brain size.mesencephalic nucleus ellipticus remains obscure and it has nohomolog in other mammals, except for elephants and possiblyseals.The superior colliculus forms an obvious prominence inall cetacean species. In many, such as Tursiops, the superiorcolliculus is only a fraction as large as the inferior (acoustic)colliculus, a reversal of the size relationship seen in humansand other land mammals. The lateral geniculate nucleus isreadily identifiable, but, in Tursiops and Delpliinus at least,there is reported to be no true lamination such as occursin mammals with binocular connections. Mapping studies bySoviet investigators have located visual cortex not at theextreme occipital pole, but in a superior and medial position.The density of calretinin-positive neurons in dolphin visualcortex is low compared to the equivalent area of human cortex.8. Dolphin sleepSoviet investigations appear to support an earlier claim byAmerican observer, John Lilly, that dolphins can sleep withone cerebral hemisphere awake. The Soviets reported markedasymmetries in electroencephalograms (EEG) from right andleft hemispheres of Tursiops and recognized three dolphinsleep stages: stage 1, desynchronization; stage 2, intermediatesynchronization including sleep spindles and theta and deltawaves; stage 3, maximal synchronization, when delta waves ofmaximal amplitude occupied not less than 50% of each scoringinterval. Stages I and 2 occurred bilaterally or unilaterally.Stage 3 occurred in only one hemisphere at a time. Wakefulnessor bilateral EEG desynchronization (EEG stage 1 in bothhemispheres) occupied 50 to 60% of the recording time.Stage 2, intermediate synchronization, was sometimes recordedbilaterally, and at such times dolphins displayed EEG patternstypical of terrestrial mammals. Unihemispheric slow wavesleep (stage 3 in only one hemisphere), the main type ofsleep observed in the dolphin brain, occupied 30 to 40% ofrecording time and could last more than two hours. Paradoxicalor REM sleep was not found in extensive recordings of some 30dolphins. American workers, however, reported a brief periodof REM (based on loss of "trunk" muscle tonus) from a singlenight's recording of pilot whale EEG.
The Cetacean central nervous system9. The senses of touch, temperature and painThe cetacean trunk and tail are normally smooth, firm, and entirely hairless. Mysticetes have bristles or tiny vibnssae aboutthe forward portion of the head. Fetal odontocetes have one orseveral vibrissae on either side of the snout or upper lip, butthese fall out around the time of birth, leaving only whisker pitsbarely visible in adult animals. On histological section, thesepits can be seen to contain the remnants of the vibrissa anda good nerve supply. Encapsulated nerve endings are foundin the dermis. These endings are especially numerous aboutthe head, and around the blowhole, anus, and genital slit. Thetrigeminal nerve, the largest of the cranial nerves in Mysticetiand exceeded only by the auditory nerve in odontocetes, has aprominent ganglion. Trigeminal sensation is better representedthan general body somatosensation. The tactile thalamus isreduced compared with that of other mammals. The arcuatedivision is more developed than the external division, reflectinga greater representation of the face in animals that haverelatively large heads.Mapping studies have located somatosensory cortex in anarea postero-lateral to and bordering motor cortex and anteriorto and bordering visual and auditory cortex. Skin sensitivity ofsmall odontocetes has been studied with evoked potentials tostimuli such as vibrating, tapping, stroking or dripping wateron the skin recorded from contralateral somatosensory cortex.In Twsiops. greatest skin sensitivity was on the head - theupper and lower lip near the commissure, around the eyes,and around the blowhole. Stimuli to the body trunk and tailproduced minimal evoked potentials. Soviet investigators usedthe galvanic skin response (GSR) to stimuli produced by a0.3 mm weighted wire to make a partial map of body skinsensitivity in Delphinus delphis. The authors considered theirvalues for the threshold of sensitivity to touch around thedolphin eyes and blowhole to be close to the figures for a humanbeing in the most sensitive skin areas, i.e., the tactile surfaces ofthe fingers, the skin of the eyelids, and the lips.No systematic studies have been done on pain perceptionor sensitivity to temperature. My observations, made largelyduring the veterinary care of odontocetes, suggest that thesecetaceans are sensitive to painful stimuli to roughly the sameextent as domestic animals and must be anesthetized forsurgical procedures.10. The auditory systemHypertrophy of the auditory system may be the primary reasonfor the dolphin's large brain. The medial geniculate nucleusis about 7 times larger than that of the human, the inferiorcolliculus is 12 times larger, and the nucleus of the laterallemniscus is over 250 times larger than in humans. Theventral cochlear nucleus and some other brainstem nuclei alsoseem massive when compared with the human equivalent. Thecetacean auditory nerve has several times as many fibers asthe eighth nerve of man. Studies of fiber spectra have revealedlargermyelinated fibers in odontocetes than in mysticete whalesand the auditory structures are in general larger in odontocetebrains. Peak fiber diameters in the sperm whale eighth nervewere about 9 pm. in the bottlenose dolphin about 7 pm andin the fin whale about 5 pm. Auditory tracts reaching thecerebral cortex are extensive. Some observers of the dolphinbrain suggested that the cerebral cortex may have reached its«reat development on the basis of acoustic input.Mapping the auditory cortex. Soviet investigators locatedextensive auditory projection areas on the dorsal surface ofeach hemisphere about 1.5 to 3.0 cm lateral to the sagittalsuture. Thus, compared with most land mammals, there is inthe dolphin brain an apparent shifting of the auditory area355from the temporal to the parietal lobe and the dorsum of thehemisphere. Evoked potential data suggest the presence of bothprimary and secondary auditory cortex whereas histologicalinvestigation does not. On physiological grounds, the bat alsoexhibits complex organization of the auditory cortex, yet. likethe dolphin, shows the histologist a more primitive level ofcortical development than, for example, carnivores or primates.The extent of auditory cortex in dolphins may be greaterthan that indicated in the mapping experiments previouslymentioned. A tonotopic map of the cochlear projections on thedolphin cortex has not been done; nor have complex stimuli ofdifferent delays or rise times or other acoustic characteristicsbeen used in attempts to find areas of cortex specialized forspecific information bearing parameters like those found in batcortex. Therefore, it is entirely possible that further auditoryprojection areas will be found in temporal cortex, which, in thedolphin, is less accessible than the dorsal area that has beenmapped.Hearing and the ear. The mammalian ear evolved tor hearing in air. In assuming the aquatic mode, the cetaceans havemodified this aerial system, and audition has apparently becometheir most highly developed sense. When the distant ancestorsof the cetaceans entered the aquatic medium with their aerialear, it is almost certain that they could immediately hear highfrequency sounds conducted directly through the body becausebody tissues are well matched with water for sound conduction. Human divers can hear high frequencies underwater, but.because of the upper frequency limit of human hearing, thereis no pitch discrimination in the ultrasonic region above about20 kHz. The evolution of the dolphin ear has apparently beena process of enhancing those characteristics that allowed forgreater high-frequency"" hearing sensitivity and complex auditory processing. Audiograms have been done on several speciesof smaller odontocetes" by both behavioral and electrophysiological techniques. Tursiops responds to frequencies as high as150 kHz with greatest sensitivity between about 20 and 100 kHz- their hearing at frequencies below 1 kHz is relatively poor.Although no auditory studies have been done on the largebaleen whales such as the blue and fin it is assumed that theirhearing sensitivity may be shifted to the low frequencies sincethey produce calls as low as 16 to 20 Hz.All cetaceans lack a pinna and the external auditory meatushas apparently become a vestige in most species. The dolphinossicular chain is stiff and the malleus does not attach directlyto the tympanic membrane. In modern dolphins, the basilarmembrane of the cochlea is relatively long (35 to 40 mmin Tursiops) and very narrow near the basal end (25 pm inTursiops). The number of inner hair cells in the dolphin cochleais about the same as. and the number of outer hair cells onlyslightly greater than, in humans, but the number of ganglioncells is much larger. The ratio of ganglion cells to hair cells(inner and outer) Ts roughly 2:1 in humans and 5:1 in Tursiops.Echolocation. Research on dolphin echolocation done during the past thirty years has confirmed an earlier suspicion.Men who collected the first permanent captive dolphin colonyat Marine Studios in Florida in the late I930's and 1940"s suspected that dolphins possessed some sort of sonar or echolocation ability. Studies have since shown that blindfolded Tursiops can make extremely fine discriminations over underwaterranges of at least 100 m by employing trains of high-frequencyclicks emitted from the nasal system and directed forward in afairly narrow beam.Electrophysiological experiments with dolphins have shownthat temporal resolution of successive sounds is extremelyrapid and that very small changes in stimulus frequency altered evoked potential (EP) amplitude and waveform. The typical midbrain EP of Tursiops appears specialized for ultrasonic,ultrabrief, fast-rising, closely-spaced sounds like the echoloca-
356The Cetacean central nervous systemDOLPHIN10 msnucleus, at least in the caudal part. The pyramidal tract is verysmall. The cortical projection into the cord is rather small;however, there seems no doubt that corticospinal fibers arepresent and form a crossed projection in cetaceans. Accordingto one observer, the morphology of muscle spindles andneuromuscular junctions in Tursiops appeared similar to thoseof other mammals.CAT13. The pineal, mammillary bodies, and pituitary10 ms2 msFigure 5. Click-evoked dolphin (Tursiops) averaged brainstem response compared with that of the cat. The great hypertrophy of theauditory brainstem and large auditory fibers gives rise to a robust ABRwith waves of relatively short latency, even when compared to muchsmaller-brained species.tion clicks. However, at several cerebral locations (mainly in theposterior lateral temporal cortex) long latency, long duration,slowly recovering EP's have been evoked by lower frequencies,with either fast or slowly rising acoustic envelopes. This suggests dual analysis systems, one specialized for the ultrasonicclick and the other for lower frequency sounds such as whistlesand squeals produced by many of the smaller odontocetes andsome other whales as well.The averaged brainstem response (ABR) can be recordedfrom electrodes on the skin surface or placed subcutaneouslyover the dolphin cranium. The click-evoked dolphin ABRconsists of 7 waves within 10 msec, numbered by the positivepeaks at the vertex (Figure 5) and corresponding well in respectto latency of each peak with waves in other mammals. Thedolphin ABR waves are large, sometimes reaching an amplitudeof 10 /iV. The waves decrease in amplitude and increase inlatency as click stimuli are attenuated. The latency-intensityfunction is flat compared with that of other species. Brainstem transmission time (BTT) is considerably faster in Tursiops(brain weight around 1500 g) than in humans or domestic catsand is similar to that of the rat. Despite a much longer nervepathway, BTT in the dolphin is equal to or faster than thatin much smaller brained species. It has been suggested that,due to larger auditory myelinated fiber diameters, the axonalconduction velocity is higher by just enough to compensate fora longer path in the dolphin brainstem.11. The facial nerveThe main facial nucleus lateral to the superior olive is large andconspicuous. The dolphin facial nerve is well developed andapparently supplies the extensive musculature of the blowhole,nares and nasal sac system. Since sound production is soimportant to animals that use echolocation and rely uponsound for underwater communication, such development is notsurprising.12. The spinal cordThe spinal cord is nearly cylindrical throughout. A cervicalswelling is present in all species studied, but the lumbarenlargement is described as absent or not prominent. Thefin whale and harbor porpoise have 44 spinal nerves - eightcervical. 12 thoracic, and 24 lumbocaudal. The anterior hornsare long and slender, occupying about one-half of the greymatter. The posterior horns have a stunted appearance. A short,pointed lateral horn is discernible at thoracolumbar levels. InTursiops, the ventral columns of white matter are stronglydeveloped. Clarke's columns are fused into a single medianIn numerous dissections, I have never found the pineal bodywhich is considered absent by most observers of the odontocetebrain. There is one report of a small pineal from a mysticete,the humpback whale. The organ is also present in embryonicstages of the blue whale. Gross examination does not revealmammillary bodies, but mammillary nuclei are recognized histologically. The pituitary is well developed with adenohypophysis and neurohypophysis separated by a dural septum.14. The cerebellumIn the embryonic stage, the dolphin cerebrum and cerebellumare about equal in width. According to paleontologists, theearliest cetaceans were the first giant mammals adapted tolife-long swimming. These ancient cetaceans already had alarge cerebellum that was wider than the cerebrum. In modernodontocetes, the cerebrum has so enlar
primitive mammals to a much greater extent than have the great ofmodern land mammals. A long period evolution Figure 1. Right side of head, Bottlenosed dolphin Tursiops. A vestiae of external auditory meatus, M melon. Figure 2. (A) Postero-ventral and (B) Antero-ventral views of a neonate d
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Project - SUGAM End User Manual Project System DOCUMENT DETAILS PROJECT NAME MODULE Business Scenario: SUGAM PROJECT SYSTEM PROJECT SYSTEM MODULE LEAD - BSPTCL MODULE LEAD - YASH PROCESS OWNER Sri. Rakesh Kumar Sri. Praveen BBP NUMBER AS PER BPML PROCESS NAME PROJECT SYSTEM AUTHORS & PARTICIPANTS Role Name Core Team Members Sri. Praveen - AEE Projects-II
IV. PMO Project Management Lifecycle (Refer to attachment 2 - OIT PMO Project Management Lifecycle) The Project Management Process governs the project life-cycle which is comprised of the following five phases: 1. Project Initiating phase 2. Project Planning phase 3. Project Funding phase 4. Project Executing phase 5. Project Closing phase
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Project Risk Management A project planning enables project manager to translate project requirement into Work breakdown structure (WBS), tasks list, Gantt charts, resource assignment and risk register, etc. Once project charter is approved, the project is formally initiated. Project planning activity can begin
