Caracterización CE

Cnly three studios have described the innervation of the axial complex and there have dealt with the asteroid ..eteriae rubens (BA’OTuVEK and VCIf H B R 196£)f and the echinoids pr imaechinui: miliarlr (JAHGCU & hCHAlTIH 1977) and ■ phnerechinui. ;tt»anul.rir (BACHK JT <Sh GCLIDPCHPIP 1?7€b).

The £tcne canal, which passes from the axial complex tc the circumoero— phayeal water liny, ie named ar such, after the translation cf 71 Try: *

1

Ai tropocten aurnntiacuf contained cnlcireou' i piculer which could be detected by rqueesing the canal with a pair of forceps. In echinoid* however, there are far fewer rpiculet in the stone canal (a consider ble advantage for tissue processing for T K) but the terminology remains the same. Kort early f tudies

65

on the ttcne ca al (tee r ICHCl 1966 fcr a review) were c o n c e m e u with the direction of ciliary currents within the lumen of the ©anal, and unlike the madrepcrite most workers cocmed tc agree upon the presence of strong orally directed currents (i.e. currents down the stone canal) • In a clastic export* ment by CirfklLi (

1914

There have been no published studies on the ultrartructurc of the rtone canal from any clacc of echinoderm*

The pollan veciclet have been described at •■ntcular tacf art:in; interraaially from the water r i n

:1

and

The circiunoecophsge il wuter ring and radial water canals of all clacree of echinodirmi have been the subject of a few histological .nd functional morphological studies. (eea review by HICHOLh 1566)* . ct t of there studies have been concerned with the role of the water canal in tube foot extension, particularly in the ophiuroids (E0CK-4U?t & WCC^L Y 1963| tC X >Y 1967} and crinoidt (KlCHCLl 196C}* There have been no published ultractructural studies on the water ring or water can le*

It ie therefore the purpose of this chapter to describe studies on intrathecal regions of the echincid water vascular system but with a

particular enphati t on their innervation a:id muscle structure* ' roia there studies, hirtochemical and ultractructur

^-1

66.

BE£ULTr

1

.

Sine® the general ultraetructure of the echinoid axial complex

her boon dace ibed recently i. readme c-:inin mlliarie (j ~T-r" & ^ M L TIN 1974] and :. phaerec inu -ranul ric (? c-iR NX '• 001' C T..7" 19?fa) it i= unnece: j .try to repeat their findingr ar the a x i a l complex of c intie ec eulentue ic very

Bimil r in i tructure.

For the purporer cf thio study the axi 1 complex c i bo divided into five main region; (Fig* XI k)i

i) the n draperito which oor.vaunic ter with the exterior* ii) the ampul1» of the rtone canal which open; into the

aadrepcric canal £ (hydroporer} *

ill} the 1 byrinthine axi 1 organ which cont inc the pulsatile ver; el*

iv) the termination of the pul; -tile ve.-rel ’which abut; onto a cavity within thu lu .dreporite*

v) the t tcno canal which communic tes with tho circumcutoph^ eal w :ter ring.

The morphology of the raadreporic pi te or modropcrito hor. boon preview ly def cribed in Chapter 3. The poriferon* region of -.he pi to conrirtB of a longitudinal array of canal; 9 the nr dreporic can 1" , pagein. through the pi to. l ight microscopy and electron micro? copy chow that the canalt are ccntinuour with the ampulla o the • tone ca.al *m& thu; lined by celli whic are hcmolc— gotir to the endotheli 1 celli lining all regions of the water vet scalar cyvtem. Fovever, the endotheli; linin the madrepcric canale r how di;tinct zonal variation along the length of the canal (Fig* i t ) * The proximal half of the canal if lined by a •. imple t c uar cui endothelium ( ig.

46

endothelium becomes thicker and more extensively ciliated (Pig* 47)* The dit tal half of the canal it lined 'ey ~ columnar endothelium c*. iracterit ed by lent microvillous pro Section?: similar in appearance to bra: u-bcrder opithelia. axtondiag from the di; tal endothelial cell into the lumen o: the canal ere lon;.. ciii • ( * tC^i) wfeici bend ■ c m project ten .‘.I'd. the extern opening of the canal ( i g s * 46 and 49)* moebocytct , granular inolinionr and as sorted vacuolar structural api e r within the c-nalt* Also occurring wit.in the dit tal eadothelia of the canals arc numerous.- spirit la— shaped aid lobular e moratory colli t w m y o f which ohoi interne ^ o r y awt&ohroiaa ia with

sure

o mat culrture or innervation of the n&drapcric canal, w t observed* A r ther anomtiou; pr©cipit ,tioa of urunyl acetate occurred over the endctiic-li microvilli and ecae V icuol r . Iruct re.\ within tiio taadreporic Cc.ali (fig* 46 } The reui ont for this are unkuownj it i possible however th it ur&nyl precipi- t.-.tion may bo intens ified over itee of highly polyanionic i-ubotaneet such ar the acid rmxccpolyc acckarides produced h. the secretory cells*

l nfcrtun t,ly t difficulties wit-* embedding modi.* infiltration (even with bpurr) hindered this present ultrastructur 1 study oi the cu^drepcrite*

The axial orgu. ©on be divided into three main layur*. (fig* .CX)* i) an outer ciliated epithelium containing'; a few, small,

Ion* :itudinally orie t .ted mac cl e call© and underlain b: ui extensive b siepitheli 1 plexus,

ii) a middle connective tissue layer which if extensively murcttlurized by mainl circularly orientated murcle cell?, ill) a cili ted endothelium which liner the axial .• inur*

The apparently complex structure cf the axial organ it uue to e tearive labyrinthine evaginations cf the axial ii m u • The outer layer of the axial organ it similar in ttructur© tc that cf the stone canal and vawer c&nalc i*e