THE RELATIONSHIP OF THE CHELICERATE ARTERIAL SYSTEM ...

More documents

Recommendations

Info

cmusperineural vascular membrane 1ventral suspensorstransverse suspensorsFig. l.-TYPICAL APULMONATE ARTERIAL SYSTEM. This condition exists in all chelicerateswhich lack book lungs. It exists in the arachnid Orders Palpigradida, Opilionida, Acarida, Pseudoscorpionida,Ricinuleida, Solpugida, and in the lungless spiders. It exists also in the merostome,Limulus, and a similar, homologous condition exists in the Pycnogonida. The central nervous System isshown in dark stipple. Note that blood is pumped into a periganglionic arterial sinus which surroundsthe central nervous System. A: midsagittal view; B: transverse section through the subesophagealganglionic mass; C: lateral view of the endosternite and dorsoventral muscles, seen from the left;D: dorsal view of the endosternite and transverse suspensors; the circles represent the positions ofdorsoventral muscles.tinuous. The endosternite, in the apulmonate arachnids, is a thickened portion of theperineural vascular membrane.In all the pulmonate arachnids (i.e., those which breathe with book lungs) the perineuralarterial development stops short at the stage (äs in the larval Limulus) in which apair of thoracic sinuses lie on top of the subesophageal ganglionic mass (Kingsley,1893). The endosternite of pulmonates develops independently of the arterial System,notwithstanding the primitive association of the two which persists in all other chelicerateswhich have endostenites. The arrested arterial development peculiar to pulmonatearachnids is an ontogenetic specialization which apparently has arisen through neoteny.The possibility that this has actually occurred will be discussed in greater detaillater.MATERIALS AND METHODSAll specimens were chosen for this study on the basis of availability. Some groups ofchelicerates are rare, in which case specimens for dissection must be obtained either fromspecialists, or eise from curators of museum collections. Dr. J. W. Hedgpeth gave me
FIRSTMAN-CHELICERATE ARTERIAL SYSTEM AND ENDOSTERNITEchelicerat arteryendosterniteheartendosternitethoracic sinus.ventralsuspensor'mouthpedipalpal arterydorsal suspensorsendosterniteabdominal dorsoventral musclesendosterniteventral suspensors•ransverse suspensorsFig. 2.-TYPICAL PULMONATE ARTERIAL SYSTEM. This condition exists in all arachnidswhich possess book lungs. It exists in the Orders Scorpionida, Thelyphonida, Schizomida,Amblypygjda, and Araneida (except lungless Spiders)- The central nervous System is shown in darkshading. Note that blood is pumped into a paired thoracic sinus which lies on top of thesubesophageal ganglionic mass. A: sagittal view, with the left side of the arterial System superimposed,äs seen from the left; B: transverse section through the subesophageal ganglionic mass; C: lateral viewof the endosternite and dorsoventral muscles, seen from the left; for clarity the circulatory system isomitted; D: dorsal view of the endosternite and transverse suspensors; the circles represent the positionsof dorsoventral muscles; for clarity the thoracic sinuses have been omitted, though a heart andaorta are shown. For a dorsal view of tne thoracic sinus arterial System, see Figure 19B.specimens of the following pycnogonids: Colossendeis scotti, Pycnogonum rhinoceros,Endeis sp., Decolopoda australis, Nymphon charcoti, Pentanymphon antarcticum, andAmmothea striata. Dr. Willis J. Gertsch gave me specimens of the following arachnids:Prokoenenia wheeleri, Trithyreus pentapeltis, Cryptocellus boneti, and Orthonops gertschi.From Dr. D. P. Abbott, I obtained Garypus californicus', from Dr. R. W. Mitchell,Cryptocellus osorioi', from Dr. L. E. Eighm, Siro acaroides', and from Miss M. J. Moody, aCosta Rican amblypygid, Tarantula sp. I purchased specimens of Pycnogonum littorale,Argas persicus, andLimulus polyphemus from General Biological, Inc. (Turtox), Chicago,Illinois.Dr. E. T. Röche prepared serial cross sections of Siro acaroides', the microtome sectioningof this arachnid was made practical by the prior removal of the exoskeleton. Allother specimens used in this study were dissected in 70% ethanol, using a Spencer stereoscopicdissection microscope with objectives of IX, 4X,and 8X, and with oculars of 12Xand 20X. Most specimens were cut midsagittally, with a sharp razor blade, and anchoredto a Syracuse watchglass with paraffin. Other specimens were cut parasagittally, to theleft of the midline, anchored in paraffin on the right side, and dissected from the left
Page 3: FIRSTMAN-CHELICERATE ARTERIAL SYSTE
Page 7 and 8: FIRSTMAN-CHELICERATE ARTERIAL SYSTE
Page 15 and 16: FIRSTMAN-CHEEICERATE ARTERIAE SYSTE
Page 35 and 36: ;FIRSTMAN-CHELICERATE ARTERIAL SYST

THE RELATIONSHIP OF THE CHELICERATE ARTERIAL SYSTEM ...

Create successful ePaper yourself

Delete template?

Save as template?