THE TRACHEA OF THE HAWAIIAN GOOSE

Transcription

1 Sep., THE TRACHEA OF THE HAWAIIAN GOOSE By PHILIP S. HUMPHREY The unforunae deah of one of a pair of S. Dillon Ripley s Hawaiian Geese (Bruna [ Nesoche#] sandvicensis) has given me he rare opporuniy of examining a fresh specimen of his ineresing species. Oher han Miller s (Univ. Calif. Publ. ZOOS., 42, 1937: l-80) sudy of he Srucural Modificaions of he Hawaiian Goose (Nesochen sandvicensis), here has been no sudy of he morphology of he Hawaiian Goose. Miller s sudy was confined o an analysis of hindlimb locomoor adapaions. I is regreable ha he specimen available o me was damaged so severely as o make sudies of perylosis, digesive rac, and cerain oher aspecs of he anaomy of his specimen impossible. The poserior half of he rachea, however, was undamaged. Since his srucure and is associaed musculaure have never been described for he Hawaiian Goose, I ake his opporuniy of making a record of hem. \ This specimen of he Hawaiian Goose was a year old and probably a male, alhough I as unable o idenify he eses wih any cerainy. Pos-morem examinaions reve ed indicaions ha he bird may have been weakened by hepaiis before being 7 a acked and parly eaen by ras. The lining of he empy gizzard was brigh chrome y $ llow in color, and he gall bladder was grealy enlarged. The deah of one of Dr. Ripley%&rsralian Black Swans (Cygnus aruus) in 1957 was aribued o hepaiis; his bird had an enlarged gall gladder and a yellow gizzard lining. The fac ha one of he Hawaiian Geese was aacked by ras while none of he many healhy birds in he pen was aacked lends furher suppor o he idea ha he goose was in a weakened condiion. I am graeful o Dr. Ripley for his helpful suggesions and for permission o examine his valuable specimen. For his help in making a deailed phoographic record of he anaomy of he rachea of he Hawaiian Goose, I am very much indebed o Rudolph Zallinger. I wish o hank Shirley Glaser for assisance wih figure 1 and leering figure 2 and Jean Richards for yping he manuscrip. This sudy was underaken in he course of a survey, suppored by he Naional Science Foundaion, of he anaomy of he rachea of ducks and of he classificaion of ha group. ANATOMY OF THE TRACHEA AND ASSOCIATED STRUCTURES Trachea.-The rachea of he Hawaiian Goose exends along he venral surface of he neck in close associaion wih he esophagus. The rachea diverges from he esophagus approximaely 3 cm. anerior o he arms of he furculum and proceeds venrally along he membrane of he inerclavicular air sac a an angle of 45 degrees. A a poin 12.9 mm. dorsal o he hypocleideum and 30 mm. venral o he esophagus he rachea eners he inerclavicular air sac and proceeds dorsally a an angle of 4.5 o 50 degrees from he verical. Couning from he poserior end of he rachea, racheal ring 30 lies a he level of he hypocleideum. The rachea ouches he anerior dorsal margin of he body of he sernum in passing. The laeral margins of he rachea beween he furculum and he anerior margin of he body of he sernum are joined by membranes o he venrolaeral walls of he inerclavicular air sac. The dorsal surface of he caudal erminaion of he rachea is 3 mm. venral o he esophagus and lies dorsal o a poin 30 mm. caudad of he anerior margin of he sernum in he midline (see fig. 1). The dimensions of he rachea as i passes beween he arms of he furculum are: laeral diameer, 10.6 mm.; dorsovenral diameer, 7.9 mm. The rachea gradually decreases in size poseriorly; 10 mm. anerior o he poseriormos exremiy of he ympanum i measures 6.4 mm. in dorsovenral diameer and 6 mm. in laera diameer.

2 304 THE CONDOR Vol. 60 The ympanum may be incompleely fused in his individual. Is measuremens are: greaes lengh along venral surface, 5 mm.; greaes lengh along dorsal surface, 5 mm.; dorsovenral diameer a anerior end, 7 mm.; laeral diameer a anerior end, 6 mm.; smalles laeral diameer, 5 mm. ; greaes dorsovenral measuremen a poserior end of ympanum, 10 mm. Adul specimens of Anser and Bruna have ympanums which are four or five imes as long as he ympanum of his year-old specimen of B. sandvicensis. I do no have he maerial o deermine he relaion of age o variaion in fusion and lengh of he ympanum in geese. Fig. 1. Laeral view of he poserior end of he rachea of Bvana ( Nesocken ) sandvicensis. The rachea has been moved slighly dorsal so ha he Mm. ypsiloracheales and Mm. sernoracheales could be shown o beer advanage. The venral limi of he inerclavicular air sac beween he hypocleideum and he anerior border of he sernal body is indicaed by a dashed line. Bronchi ad syrinx.-the righ and lef bronchi are of equal size and neiher is enlarged nor has any enlargemens. The righ bronchus (he lef was no measured) was 3.9 mm. in dorsovenral diameer hroughou is lengh from he firs bronchial semiring caudad of he rachea o he poserior-mos bronchial semiring. The righ bronchus has 7 semirings; here are 6 semirings in he lef. Each bronchus diverges from he midline a an angle of abou 50 degrees. The bronchi consis largely of ransparen membrane; he bronchial semirings are no very prominen. The disance beween he middle of he firs semiring and he laeral poserior margin of he ympanum (he caudal end of he rachea) is 9 mm. The paired exernal and inernal ympaniform membranes and heir supporing srucures comprise he syrinx. The exernal ympaniform membrane is suppored aneriorly by he caudal margin of he laeral wall of he bronchial opening a he caudal end of he ympanum; his margin measured 9.3 mm. in lengh. The firs bronchial semiring forms he poserior suppor for he exernal ympaniform membrane. Compared o waerfowl oher han geese, he Hawaiian Goose has an exernal ympaniform membrane which is very exensive in area. The dorsal and venral margins of he exernal ympaniform membranes aach impercepibly o he corresponding margins of he righ and lef inernal ympaniform membranes, respecively, The inernal ympaniform membrane receives suppor aneriorly from he margin of he mesial wall of he

3 Sep., 1958 TRACHEA OF THE HAWAIIAN GOOSE 305 bronchial opening a he caudal end of he ympanum. The inernal ympaniform membranes erminae caudally by fusing wih one anoher in he midline. On looking hrough he inerbronchial opening beween he righ and lef inernal ympaniform membranes one can see he venral surface of he esophagus which is 2 or 3 mm. dorsal o he dorsal margins of he bronchi anerior o he firs bronchial semiring. Dorsally and venrally his inerbronchial space opens ino he inerclavicular air sac. Tracheal muscles.-the Hawaiian Goose possesses in common wih oher Anseres wo pairs of exrinsic racheal muscles, Mm. sernoracheales and Mm. ypsiloracheales, and one pair of inrinsic racheal muscles, Mm. racheolaerales. The sernorachealis is a very narrow, hin band of muscle uniformly 2 mm. in widh for mos of is lengh; i is slighly wider a is origin. The origin of he sernorachealis is on he dorsal side of he aneromesial margin of he sernocoracoidal process of he sernum. The muscle exends 30 mm. aneromesially o is inserion on he laeral surface of he rachea a racheal rings 18 and 19 (he poseriormos pre-ympanic racheal ring being couned as he firs). The inserion measured 3 mm. in lengh and is anerior limi was 37 mm. disan from he caudal margin of he ympanum and 17 mm. disan from he poserior limi of he fleshy par of he racheolaeralis. The sernorachealis insers on he rachea venral o he body of he racheolaeralis. The ypsilorachealis diverges from he laeral surface of he rachea a racheal rings 23 and 24 and runs direcly o he origin 20 mm. caudad. I is a very hin muscle 3 mm. in widh hroughou is lengh. The origins of he wo ypsiloracheales mee a he midline a he anerior border of he body of he sernum. The origin of each ypsilorachealis is 3 mm. in maximum widh. The ypsilorachealis and he racheolaeralis ogeher exend aneriorly along he laeral surfaces of he rachea and presumably have heir anerior aachmens on he venral surface of he cricoid carilage. Because he anerior par of he rachea was missing in his specimen, he relaions of he ypsilorachealis and racheolaeralis in ha region could no be deermined. The racheolaeralis erminaes as a narrow endon on he laeral surface of he rachea a he second pre-ympanic racheal ring 6.5 mm. anerior o he poserior margin of he ympanum. The fleshy par of he racheolaeralis erminaes on he laeral surface of he enh racheal ring 19 mm. anerior o he poserior margin of he ympanum. The racheolaeralis passes dorsal o he inserion of he sernorachealis. DISCUSSION I have examined he racheas of Bra&a bernicla hroa, B. canadensis, Anser ( Chen ) caerulescens caerulescens, A. c. hyperboreus, and A. c. alanicus. In all hese species he rachea diverges venrally from he esophagus and approaches he hypocleideum before enering he inerclavicular air sac. The arrangemen of he racheal muscles, he shape of he ympanum, and he orienaion of he bronchi and ympaniform membranes is he same in he Hawaiian Goose and oher geese ha I have examined excep for minor variaions. Alhough no enough specimens have been examined o enable me o commen on variabiliy, here appear o be wo differences beween Anser and Brana wih respec o he anaomy of he rachea. These are (1) in he number of bronchial semirings, and (2) in he locaion of origin and widh of he ypsilorachealis. Nesochen agrees wih Bra&a in boh hese characers. Wheher or no examinaion of series of specimens of hese and addiional species of geese will show ha hese characers consisenly reflec he limis of he genera as hey are currenly undersood (Delacour and Mayr, Wilson

4 306 THE CONDOR Vol. 60 Bull., 57, 1945:3-55) remains o be seen. I would be paricularly ineresing o examine specimens of addiional species of Anser, including Philaze, Ezdubeiu, and cygnopsis. Specimens of Bra&z and Nesochen a my disposal had fewer bronchial semirings han did specimens of Amer. They also had a narrow ypsilorachealis originaing on he anerior margin of he sernal body near or a he midline. Specimens of Anser, wih one possible excepion, (see fig. 2), had ypsiloracheales which originaed anerior o he sernum and were eiher narrow (2 specimens) or wide (2 specimens). Branfa sandvicensis 6 7 Branfa bernicfa 6 6 Branfa canadensis 7 7? Anser c. caerulescens - II Anser c. caerulescens - 9 Anser c. ailanficus?? Anser c. alanficus Anser c. hyperboreus - II - 9 Fig. 2. Number of bronchial semirings and characerisics of M. ypsilorachealis of several specimens of Anser and Brana. Bearing in mind ha more maerial should be examined o deermine he variabiliy of hese characers, I can conclude ha Nesoch en and Brana are in srucure of he rachea more similar o one anoher han o Amer. This conclusion is in agreemen wih Miller s (op. ci.: 60) saemen ha Nesochen is mos closely relaed o Bra&u.... Wih regard o racheal characers I canno agree wih Miller s saemen (Zoc. ci.) ha Nesochen is as disinc from Bruna as is Cher. The srucure of he rachea of Nesochen bears ou Delacour and Mayr s (op. ci.) opinion ha he genus should be merged wih Bruna. SUMMARY 1. The caudal porion of he rachea and racheal musculaure, and he bronchi of he Hawaiian Goose are described. 2. The rachea and racheal musculaure, and bronchi of he Hawaiian Goose are idenical (excep in minor deail) wih hose srucures in oher species of Bruna and only slighly differen from hose in Amer.

5 Sep., 1958 TRACHEA OF THE HAWAIIAN GOOSE The bronchi of Brana and Neso&e& each have 6 or 7 bronchial semirings; hose of Anser each have 9 o 11 semirings. 4. The ypsiloracheales of Brana and NesocJzen are narrow and originae on he anerior margin of he body of he sernum near he midline; hose of Amer may be eiher narrow or wide and originae (wih one possible excepion) anerior o he sernum. 5. More specimens of Bra&a and Anser should be examined o deermine more precisely he variabiliy of heir racheal characers. 6. The srucure of he rachea of Nesochen bears ou Delacour and Mayr s opinion ha he genus should be merged wih Bra&a. Peabody Museum of Naural Hisory, Yale U&e&y, January 27, New Hmven, Conmx%icui,