- J M
O ffp rin t from “M a rin e B iology”
International J o u rn a l on L ife in Oceans a n d Coastal W aters, Vol. 3, N o . 2, J u n e 1969, Pages 110— 116
Springer-Verlag, Berlin • Heidelberg ■ New York
Instituai wor Z e w rfw s d fiK Ä o u te m !
Insfiiute fcf
fe&iic n*33oarà
Printè* ttftabeVhtaen 69
8401 Brüden« * Belgium * f el. 059 / 80 37 15
Slow developing demersal embryos and larvae of the antarctic sea star O dontaster validus
J . S. P
ea u se
Department of Biological Sciences, Stanford University; Stanford, California, USA
S *
110
J. S.
P earse:
Development of embryos and larvae of Odontaster
A bstract
The early development of Odontaster validus a t McMurdo
Sound, Antarctica, is indirect and includes equal cleavage, a
convoluted blástula, a free-swimming coeloblastula, a gastrula,
and a feeding bipinnaria larva. Development differs from th at
of other asteroids in two respects: (1) The developmental rate
is extremely slow ; blastulae form nearly 2 days after fertiliza­
tion, gastrulation begins after 7 days, and the bipinnaria devel­
ops in about 40 to 55 days. The slow developmental rate appears
to be only partly related to the low environmental temperature
(-1 .5 °C). (2) The embryos and larvae are largely demersal.
Such behavior may be an adaptation to keep the larvae out of
antarctic surface waters, as does brooding in many other polar
echinoderms.
In troduction
T h e e a rly d e v e lo p m e n t o f a ste ro id s h as b een d e ­
sc rib ed fo r m a n y te m p e ra te a n d tro p ic a l species (e.g.
M o r t e n s e n , 1921, 1931, 1937, 1938). H o w ev er, in
p o la r reg io n s w here h a rsh co n d itio n s h av e m a d e lo n g ­
te r m la b o ra to ry o b se rv a tio n s difficult, little com ­
p a ra b le in fo rm a tio n is av a ilab le. T h e re c e n t e sta b lish ­
m e n t o f p e rm a n e n t biological la b o ra to ries in th e
a n ta rc tic , p a rtic u la rly in M cM urdo S o u n d (W o h ls c h l a g , 1963), p ro v id es new o p p o rtu n itie s to m ake
su c h o b se rv a tio n s.
T h e a s te ro id Odontaster validus K o e h l e r is one
o f th e m o s t a b u n d a n t an im als a ro u n d th e a n ta rc tic
co ast. E m b ry o s a n d la rv a e o f th is species w ere m a in ­
ta in e d d u rin g 1961 a t M cM urdo S ta tio n ( P e a r s e ,
1962). T h e p re s e n t p a p e r p ro v id es m ore d e ta ils on
th e se em b ry o s a n d la rv a e a n d draw s special a tte n tio n
to th e ir u n u su a lly slow ra te s o f d ev e lo p m e n t a n d th e ir
dem ersal h a b it.
M aterials and m ethods
Specim ens o f Odontaster validus w ere co llected in
M cM urdo S o u n d w ith m e a t-b a ite d tr a p s s e t a t ab o u t
20 m , as d escrib ed p rev io u sly ( P e a r s e , 1965).
Odontaster validus spaw ns d u rin g th e a u s tra l w in ter
fro m M ay th ro u g h m id -S ep te m b er ( P e a r s e , 1965,
1966). S paw n in g occu rred in th e la b o ra to ry on only
one o ccasion; 10 o f 35 ex c ep tio n ally rip e anim als
collected o n S e p te m b e r 4, 1961, fro m C ape E v an s,
M cM urdo S o und, sp a w n e d w ith in 5 to 105 m in after
being le ft o u t o f w a te r a t room te m p e ra tu re . A sim ilar
sp aw n in g response to being left o u t o f w a te r w as re­
p o rte d b y N e w m a n n (1925) for P a tiria m iniata.
O o cy tes sp aw n ed fro m 1 fem ale w ere m ix e d w ith
sp erm sp a w n e d from 1 m ale o f th e S e p te m b e r Cape
E v a n s sam ple. N in e ty -six p e rc e n t o f th e spaw ned
o o cy tes u n d e rw e n t fertiliza tio n , in d ic a tin g t h a t only
rip e o o cy tes w ere spaw ned. T hese fertilize d oocytes
w ere m a in ta in e d a n d th e ir d ev e lo p m e n t follow ed.
Mar. Biol.
G am etes fo r o th e r c u ltu re s o f em b ry o s w ere o b ­
ta in e d fro m ex cised g o nads. O v aries w ere d issected
fro m fem ales a n d p la ce d in finger bow ls co n ta in in g
filtered s e a w a te r k e p t a t — 1.5 + 1 °C. A fte r th e
oocytes w ere sh ed fro m th e ex cised o v aries fo r 5 m in ,
th e o v aries w ere re m o v e d a n d a few d ro p s o f sp e rm
collected fro m a fre sh ly d issected m ale w ere ad d e d .
C ultures w ere s ta r te d fro m excised g o n ad s o n th e
following d a te s in 1961: J u n e 25 (3 cu ltu res), J u l y 15
(7 cu ltu res), A u g u st 6 (5 cu ltu res), a n d S e p te m b e r 4
(6 cu ltu res). A tte m p ts w ere also m a d e to esta b lish
cu ltu res fro m g a m e te s co llected fro m ex cised g o n ad s
in J a n u a r y , F e b ru a ry , A pril, la te S ep te m b er, O cto b er,
N ovem ber a n d D ecem b er, 1961; th e se a tte m p ts w ere
unsuccessful b ecau se all th e o o cy tes w ere im m a tu re
( P e a r s e , 1965).
T h e p erc en ta g e o f o o cy tes sh e d fro m excised o v aries
th a t u n d e rw e n t fe rtiliz a tio n v a rie d fro m less th a n
1 to 3 6 % . T h ese v a ria tio n s reflected th e rip en ess o f th e
ovaries; larg e rip e o v aries fro m fem ales w ith h igh
gonadal in d ices g en e rally y ie ld ed th e h ig h e st p e rc e n t
o f fertilizab le o ocytes. P ro c e d u re s fo r h a n d lin g o v arie s
an d o o cy tes t h a t m ig h t affect th e p e rc e n t fertilize d
were also te s te d in J u ly . Single o v aries w ere d issected
from ea ch o f 4 an im als a n d tr e a te d to g e th e r fo r e a ch
o f 5 tre a tm e n ts . T w elv e to 14 h a f te r th e sh e d o o cy tes
were m ix e d w ith sp erm , 50 to 100 cells w ere collected
an d th e n u m b e r o f zy g o tes c o u n ted . T h e tr e a tm e n ts
an d p e rc e n t fertilize d w ere: (1) o v aries p laced d ire c tly
in se a w a te r a t — 1 .5 °C fo r sh ed d in g , 3 2 % fe rtiliz e d ;
(2) o v aries rin sed in se a w a te r a t —1.5 °C, a n d th e n
placed in sh e d d in g d ish es a t — 1.5 °C, 2 c u ltu re s, 21
a n d 2 0 % fe rtiliz e d ; (3) o v aries rin se d a n d p laced in
seaw ater w ith 2 % coelom ic fluid a t — 1.5 °C, 17%
fertilized ; (4) o v aries ex p o sed in th e d issected an im als
a t ro o m te m p e ra tu re (c. 20 °C) fo r 5 a n d 10 m in,
rin sed a n d p la ce d in sea-water a t — 1.5 °C, 13 a n d 14%
fertilized , re sp e c tiv e ly ; (5) o v arie s rin se d a n d p laced
in s e a w a te r a t + 5 ° + 2 °C, 1 8 % fertilized . T h e h ig h e st
p e rc e n t fertilize d w as o b ta in e d w ith th e u n rin se d
o v arie s; rin sin g p ro b a b ly w ash ed a w a y m a n y rip e
o o cytes. A lth o u g h J u st (1939) fo u n d t h a t coelom ic
fluid te n d e d to b e to x ic to a s te ro id o o cy tes, a d d itio n
o f 2 % coelom ic fluid to th e filte re d s e a w a te r h a d little
effect. T h ere w as little d ifference in p e rc e n t fertilize d
b etw e en rin sed o o cy tes a t — 1.5 °C a n d + 5 .0 °C. M ore­
over, m a n y o f th e o o cy tes a p p e a re d to to le r a te 5 an d
10 m in ex p o su re s to ro o m te m p e ra tu re s.
T h e d ev elo p in g em b ry o s a n d la rv a e w ere m a in ­
ta in e d in filtered se a w a te r in finger bow ls p laced in
p o ly e th y le n e p a n s filled w ith se aw ater. T h e p an s, w ith
J . S. P e a r s e : Development of embryos and. larvae of Odontaster
Vol. 3, No. 2,1969
th e finger bow ls, w ere p laced in e th y le n e glycol
c o o la n t in a L a b lin e T em pm obile. T h e te m p e ra tu re
w as k e p t a t — 1.5 + 0.5 °C. O ne c u ltu re m a in ta in e d a t
+ 5 + 2 °C w as k e p t in a re frig e ra to r. T h e c u ltu re s
w ere k e p t in co m p lete d a rk n e ss e x c e p t fo r b rie f
p erio d s o f o b se rv a tio n . W a te r ch an g es w ere m a d e
ev e ry 4 d a y s b y d e c a n tin g off 1/ 2 to 3/ 4 o f th e c u ltu re
w a te r a n d rep la cin g i t w ith fre sh ly filte re d se aw ater.
I n th e few cases w h en th e an im als w ere sw im m ing off
th e b o tto m , th e u p p e r h a lf o f th e c u ltu re s, w ith th e
h e a lth y specim ens, w ere d e c a n te d in to bow ls w ith
fre sh filte re d se aw ater.
111
O b serv atio n s o f th e em b ry o s a n d la rv a e w ere m a d e
b y su ck in g 25 to 100 in d iv id u a ls in to a sm all p ip e tte
a n d sp re a d in g th e m o n a g lass slide. T h e v a rio u s stag es
w ere q u ic k ly co u n te d a n d th e sp ecim en s re p la c e d in
th e c u ltu re dishes. W h e n e x te n d e d o b se rv a tio n s a n d
p h o to g ra p h s w ere m a d e (ta k in g m o re th a n a few
m in u tes) th e sp ecim en s w ere d isc ard ed .
R esults
F e r tiliz a tio n
C hanges a f te r fe rtiliz a tio n p ro ce ed ed in close s y n ­
c h ro n y in th e o n e c u ltu re e s ta b lish e d fro m sp a w n e d
100JL
& V--.
¿ -•V
■ .% > .
3 / •■ if
%
W-
â - r - ‘#1
%
'i #
Fig. 1. Developmental stages of Odontaster validus, (a) Zygote before female m aturation divisions showing prominent
germinal vesicle, 30 min; (b) two-celled stage showing polar body within fertilization membrane, 13 h ; (c) eight-celled stage,
32 h; (d) morula, 68 h; (e) convoluted blástula, 5 days; (f) free-swimming coeloblastula shortly after release from fertilization
membrane, 8 days; (g) late gastrula with mesenchyme cells and the formation of enterocoels and the stomodaeum, 44 days;
(h) early bipinnaria larva with complete gut, enterocoels, and 2 ciliary bands, 62 days; (i) bipinnaria larva with resorbed
enterocoels, 80 days. All were drawn from photographs and adjusted to the same magnifications and actual times after
fertilization given
112
J . S.
P ea rse:
Development of embryos and larvae of Odontaster
gam etes. O nly p rim a ry oo cy tes w ith in ta c t g erm in al
vesicles w ere sp aw n ed , a n d no g e rm in a l vesicle b r e a k ­
dow n o cc u rre d for a t le a st 35 m in a f te r th e o o cy tes
w ere spaw n ed . T e n m in a fte r th e sp e rm w ere in tr o ­
d uced, fe rtiliz a tio n m e m b ran es a p p e a re d (Fig. l a ) ,
b u t th e g erm in al vesicles re m a in e d in ta c t a t le a s t 1 h
a f te r fe rtiliz a tio n . All th e zy g o tes h a d u n d erg o n e
m a tu r a tio n div isio n a f te r 7 h, a n d th e p o la r bodies
w ere p re s e n t u n d e r th e fe rtiliz a tio n m e m b ran es
(Fig. lb ) .
S im ilar ch an g es o cc u rre d in o o cy tes sh e d fro m
excised ovaries. G erm in al vesicle b re a k d o w n d id n o t
o ccur in artific ia lly sh e d oocy tes fo r u p to 3.5 h before
sp e rm in tro d u c tio n . M a tu ra tio n div isio n s u su a lly
o cc u rre d se v eral h o u rs a fte r fe rtiliz a tio n . H o w ev er,
m a tu r a tio n divisions d id n o t o cc u r in u p to 3 5 % o f
th e o o cy tes t h a t fo rm ed fe rtiliz a tio n m e m b ran es.
A p p a re n tly m a n y im m a tu re o o cy tes sh e d fro m th e
excised o v arie s w ere ca p ab le o f raisin g a fe rtiliz a tio n
m e m b ran e, b u t in c a p a b le o f u n d erg o in g m a tu r a tio n
divisions.
Mar. Biol.
su ch feedings, y e t th e la rv a e still reso rb ed th e ir
en tero co els a n d e v e n tu a lly died.
R a te o f d ev elo p m e n t
T h e r a te s o f d e v e lo p m e n t o f th e se c u ltu re s w ere
e x tre m e ly slow . A s sh o w n in F ig . 2, h o w ev er, th e
d e v e lo p m e n ta l r a te s w ere sim ila r in t h e c u ltu re s b eg u n
o n d iffe ren t d a te s. T h e ch ro n o lo g y o f th e firs t o b serv ed
a p p e a ra n c e s o f w ell d efin ed d e v e lo p m e n ta l stag es
w as: cleav ag e, 0.67 d a y ; c o n v o lu te d b lá s tu la , 1.67
d a y s ; co e lo b la stu la , 5 d a y s ; g a s tru la , 7 d a y s ; m esen ­
ch y m e a p p e a ra n c e , 20 d a y s ; en tero co el a p p e a ra n c e ,
D e s c r ip tio n oj d ev elo p m e n t
D e v e lo p m e n t to a n arm less b ip in n a ria la r v a w as
sim ila r to t h a t in o th e r a ste ro id s w ith in d ire c t d ev e lo p ­
m e n t. H o lo b la stic , e q u a l cleavage (F ig. l b , c) le d to a
m o ru la com posed o f re la tiv e ly la rg e b la sto m e re s
(Fig. I d ) . T h e m o ru la sta g e w as follow ed b y a m u ch
co n v o lu ted , g en e rally 4-lobed, b lá s tu la sta g e (Fig. l e )
ty p ic a l o f o th e r p h a n e ro z o n id a s te ro id s w ith in d ire c t
d e v e lo p m e n t (M o r t e n s e n , 1913 a ; H ö r s t a d i t j s , 1939;
N e w t h , 1925). A c ilia te d c o e lo b la stu la (Fig. I f )
d ev elo p ed fro m th e c o n v o lu te d b lá stu la , a n d escap ed
fro m th e fe rtiliz a tio n m e m b ran e. G a s tru la tio n o ccu rred
b y in v a g in a tio n , m esen ch y m e b ecam e sc a tte re d in th e
blasto co el, a n d e v e n tu a lly p a ire d enteroeo elic p o u ch es
a p p e a re d (F ig. lg ) . F ollow ing sto m o d a e a l b re a k ­
th ro u g h , th e e a rly b ip in n a ria la rv a d ev elo p ed w ith p rea n d p o sto ra l cilia ry b a n d s 1 (Fig. l h ) . N o a u ric u la ria n
sta g e w ith a single cilia ry b a n d w as seen.
T h e e a rly b ip in n a ria la rv a e sho w ed little fu rth e r
ch an g e ev e n th o u g h som e w ere m a in ta in e d fo r u p to
60 d ay s. F a ilu re o f c o n tin u e d d e v e lo p m e n t w as
p ro b a b ly d u e to la c k o f su ita b le food ; th e en tero co e ls
b eg a n to b e reso rb ed a b o u t 80 d a y s a f te r fe rtiliz a tio n
(Fig. l i) . T h ese la rv a e all re a c h e d th e b ip in n a ria sta g e
d u rin g th e la te a u s tra l w in te r befo re th e b eg in n in g o f
th e su m m er p h y to p la n k to n bloom ( L i t t l e p a g e , 1965).
B ecau se th e re w as little p h y to p la n k to n p re se n t, a n d
because th e se la rv a e w ere d e m ersal (see below ), th e ir
n o rm a l food m ig h t h a v e consisted o f b o tto m m a te ria l.
F in e suspensions o f b o tto m m a te ria l o b ta in e d fro m a
g rab , a n d co n sistin g m a in ly o f d e tritu s , cilia tes a n d
flagellates, w ere offered p erio d ically to th e la rv a e.
M ateria l w as o fte n p re se n t in th e la rv a l sto m a c h s a fte r
1 Usage of the term bipinnaria for this stage follows M o r t e n s e n (1931,1937,1938) and H ö r s t a d i u s (1939). C o s t e l l o
e t al. (1957) refer to this stage as the dipleurula.
20
30
June
10
20
30
Ju ly
10
20
30
10
Aug.
1961
20
30
10
S e p t.
20
Oct.
Fig. 2. Chronology within the 4 sets of cultures of Odontaster
validus embryos. The earliest appearance of each developmental
stage is followed. The developmental stages are: 1 zygote;
2 cleavage; 3 convoluted blástula; 4 coeloblastula; 5 gastrula;
6 mesenchyme appearance; 7 enterocoel appearance; 8 stomo­
daeal breakthrough; 9 bipinnaria. The arrows indicate when
the embryos began to swim on the surface ( f ) and when they
settled again on the bottom ( i )
5
^
U
H
~s
£
|.
| 3
a 2
r'
1
0
2
3
U
5
6
7
8
D ays
Fig. 3. Odontaster validus. Developmental rates to gastrulation
in 1 culture of embryos maintained a t + 5° + 2 °C (- - - -) and
6 cultures of embryos maintained a t -1.5° + 0.5 °C (mean
and range). Developmental stages as given in Fig. 2
J. S.
Vol. 3, No. 2,1969
P ea rse:
Development of embryos and larvae of Odontaster
113
Discussion
30 d ay s ; sto m o d a e a l b re a k th ro u g h , 38 d a y s ; co m p leted
e a rly b ip in n a ria , 55 d ay s. B ecau se th e se la rv a e fed
little o r n o t a t all, th e tim e ta k e n to re a c h th e b ip in ­
n a ria m a y h a v e b e e n a b n o rm a lly lo n g ; w ith food,
p e rh a p s th e e a rly b ip in n a ria sta g e could b e re a c h e d
s h o rtly a f te r sto m o d a e a l b re a k th ro u g h in as little as
40 days.
O ne c u ltu re w as b eg u n o n J u ly 15, 1961 a n d m a in ­
ta in e d to g a s tru la tio n in a re frig e ra to r a t + 5 ° + 2 °C.
F ig. 3 co m p ares th e r a te o f d e v e lo p m e n t in th is c u ltu re
w ith th e r a te s o f d e v e lo p m e n t o f 6 o th e r c u ltu re s
b e g u n w ith g a m e te s fro m th e sa m e an im als a n d m a in ­
ta in e d a t — 1.5° + 0.5 °C. (These w ere th e cu ltu res
re su ltin g fro m th e fe rtiliz a tio n te s ts g iv e n in th e
M a teria ls a n d m e th o d s section.) T im e to cleavag e a fte r
fe rtiliz a tio n in th e -j-5 °C c u ltu re w as a b o u t h a lf t h a t
in th e c u ltu re s a t — 1.5 °C. H o w ev er, n o difference
could b e d e te c te d in th e tim es to re a c h la te r sta g es o f
d ev e lo p m e n t.
D e v e lo p m e n t rate
A co m p ariso n a m o n g d iffe ren t a ste ro id s show s a
g en e rally d ire c t re la tio n sh ip b e tw e e n la titu d e a n d
d e v e lo p m e n ta l r a te (T ab le 1); m o s t tro p ic a l fo rm s
d ev elo p fa s te r th a n m o s t te m p e ra te form s. T h is
re la tio n sh ip b etw e en d e v e lo p m e n ta l r a te a n d la titu d e
a lm o st c e rta in ly reflects a te m p e ra tu re re la tio n sh ip .
D e v e lo p m e n t o f L u id ia sa v ig n yi in th e R e d S ea
(a b o u t 30 °C), fo r ex am p le, is close to 3 tim e s as ra p id
as t h a t o f P o ra n ia p u lv illu s off S c o tla n d (a b o u t 15 °C).
W ith su c h a co m p ariso n , th e Q10 fo r a s te ro id d ev e lo p ­
m e n ta l r a te a p p e a rs to b e a p p ro x im a te ly 2. T h e d e ­
v e lo p m e n ta l r a te to g a s tru la tio n o f Odontaster validus
a t — '1.5 °C is in f a ir ac co rd an c e w ith su c h a Q10; i t is
a b o u t h a lf t h a t o f P . p u lvillu s. E a r ly d e v e lo p m e n t o f
0 . validus, th e re fo re , show s n o ev id en ce o f te m p e ra tu re
a d a p ta tio n . M oreover, as d ia g ra m m e d in F ig . 4, p o stg a s tru la d e v e lo p m e n t in 0 . va lid u s is m u c h slow er
th a n w o u ld b e p re d ic te d b y co m p ariso n s w ith o th e r
a ste ro id s ; d e v e lo p m e n t to th e b ip in n a ria in P .
p u lv illu s is a b o u t 6 to 8 tim es fa s te r th a n in 0 . validus.
A s also in d ic a te d in T a b le 1, d e v e lo p m e n ta l r a te s in
a ste ro id s a re u n d o u b te d ly in flu en ced b y fa c to rs o th e r
th a n te m p e ra tu re . Som e tro p ic a l a ste ro id s h a v e
re la tiv e ly slow d e v e lo p m e n ta l r a te s (e.g. L in c k ia
m u ltifo ra ), som e te m p e r a te fo rm s h a v e re la tiv e ly ra p id
d ev e lo p m e n ta l r a te s (e.g. P a tir ia m in ia ta ), a n d 3
species o f Astropecten fro m d iffe ren t la titu d e s a re r e ­
p o rte d to h a v e th e sa m e d e v e lo p m e n ta l ra te s. I t is
p ro b a b le t h a t th e slow r a te o f d e v e lo p m e n t in O don­
taster validus, p a rtic u la rly a f te r g a s tru la tio n , re su lts
fro m fa c to rs o th e r th a n low te m p e ra tu re .
T h e re is som e ev id en ce t h a t o th e r in d ire c tly
d ev elo p in g ec h in o d e rm s in cold w a te rs h a v e e x tre m e ly
B e h a v io r o f the e m b ry o s a n d larvae
T h e em b ry o s a n d la rv a e o f Odontaster va lid u s
a lm o st alw a y s sta y e d close to th e b o tto m o f th e c u ltu re
dishes. A fte r release fro m th e fe rtiliz a tio n m e m b ran es,
th e y seem ed to a c tiv e ly seek th e lo w est p o rtio n s o f th e
dishes (th e o u te r rin g o f th e finger bow ls), a n d larg e
n u m b e rs o f h e a lth y em b ry o s c o n c e n tra te d in th e se
d ep ressio n s. E a c h c u ltu re , how ever, w e n t th r o u g h a
b rie f p erio d (3 to 6 d ay s) w h en th e la te g a s tru la e m ­
b ry o s sw am off th e b o tto m a n d n e a r th e su rfa ce ; th is
p erio d is in d ic a te d in F ig. 2. E m b ry o s in all th e c u ltu res
b e g u n o n th e sa m e d a y w e n t th ro u g h th e su rfacesw im m ing b e h a v io r a t th e sam e tim e. A fte r th e b rie f
surface-sw im m in g perio d , th e em b ry o s a g a in co n cen ­
tr a t e d in th e lo w est p o rtio n s o f th e d ishes a n d w ere
ra re ly fo u n d off th e b o tto m .
Table. 1. Comparison of asteroid developmental rates. (Approximate times in days)
15
Species
Locality
Beginning of
gastrulation
Luidia savignyi
Pentaceraster mammillatus
Patiria pectinifera
Patiria miniata
Linckia laevigata
Astropecten polyacanthus
Astropecten aranciacus
Astropecten irregularis
Asterias forbesi
Ophidiaster guildingii
Asterope carinifera
Acanthaster planci
Asterias vulgaris
Pisaster ochraceus
Gymnasteria carinifera
Linckia multifora
Asterias rubens
Evasterias troscheli
Pycnopodia helianthoides
Luidia ciliaris
Porania pulvillus
Odontaster validus
Red Sea
Red Sea
Japan
California
Ja v a Sea
Red Sea
Italy
England
Connecticut
Tobago
Red Sea
Java Sea
Massachusetts
British Columbia
Hawaii
Red Sea
Scotland
British Columbia
Washington State
England
Scotland
Antarctica
1
1
1
1
?
1
1
1
Marine Biology, Vol. 3
1
?
1
1
1
2
2
2
2
2— 3
2—3
3
3— 4
7
Early
bipinnaria
2
2
2
3
3
3
3
3
3 —4
4
6
6
6
4— 5
5
5
6
4— 5
5
6
7
4 0 — 55
Investigator
M o r t e n s e n (1 9 3 8 )
M o r t e n s e n (1 9 3 8 )
M o r t e n s e n (1 9 2 1 )
N e w m a n n (1 9 2 5 )
M o r t e n s e n (1 9 3 1 )
M o r t e n s e n (1 9 3 7 )
H ö r s t a d iu s (1 9 3 9 )
N e w t h (1 9 2 5 )
L a r s e n (1 9 3 7 )
M o r t e n s e n (1 9 2 1 )
M o r t e n s e n (1 9 3 7 )
M o r t e n s e n (1 9 3 1 )
F i e l d (1 8 9 2 )
M o r t e n s e n (1 9 2 1 )
M o r t e n s e n (1 9 2 1 )
M o r t e n s e n (1 9 3 8 )
C e m m t l l (1 9 1 4 )
M o r t e n s e n (1 9 2 1 )
G r e e r (1 9 6 2 )
M o r t e n s e n (1 9 1 3 a )
G e m m il l (1 9 1 5 )
this paper
J. S.
114
P ea rse:
Development of embryos and larvae of Odontaster
slow d e v e lo p m e n ta l ra te s . D e v e lo p m e n t o f th e a rc tic
o p h iu ro id Ophiocten sericeum is e x tre m e ly slow a n d
m e tam o rp h o sis o ccurs a b o u t 6 m o n th s a f te r sp aw n in g
( P e a r s e , 1 9 6 5 ). P e rh a p s d e v e lo p m e n t to m e ta m o rp h o ­
sis o f th e a b y s sa l o p h iu ro id O phiura lju n g m a n i is as
slow (S c h o e n e r , 1 9 6 8 ). I f m e ta m o rp h o sis in O don­
taster validus o ccurs 6 m o n th s a fte r sp aw n in g , it w ould
ta k e p lace so m etim e d u rin g th e l a tte r h a lf o f th e a u s tra l
sum m er.
T h e unm odified r a te o f d e v e lo p m e n t a f te r cleavage
a t + 5 °C c o n tra s ts sh a rp ly w ith sim ila r e x p e rim e n ts
d o n e w ith echinoids. O n ly a th re e -d e g re e rise in te m ­
p e r a tu re (from 20° to 23 °C ) decreases th e tim e to
g a s tru la tio n b y m o re th a n 2 5 % in A rbacia punctulata
(C o s t e l l o e t al., 1957). W ith o n ly on e e x p e rim e n t a t
o n ly one h ig h e r te m p e ra tu re , how ever, i t is b y no
B
a
g G
E
O.
Q
J
>
ai
a
Z
0
5
10 15 20 25 30 35 40 45 50 55 60
D ays
Fig. 4. Comparison of developmental rates of (1) fast devel­
oping asteroid Luidia savignyi in the Red Sea a t about 30 °C
(M o r t e n s e n , 1938); (2) slow developing asteroid Porania
pulvillus off Scotland a t about 15 °C (G e m m i l l , 1915); (3)
Odontaster validus a t -1 .5 °C. D otted line indicates possible
post-gastrula developmental rate in Odontaster validus with
suitable food present. Development stages: Z zygote, G
gastrula, B bipinnaria
m e an s conclusive t h a t th e d e v e lo p m e n ta l r a te o f
Odontaster validus is in se n sitiv e to te m p e ra tu re . I n
se v eral a n ta r c tic fish, re s p ira tio n in creases m a rk e d ly
w ith te m p e ra tu re rises f r o m — 1.5° to a b o u t 5 ° C , b u t
decreases a b o v e 5 °C ( W o h l s c h l a g , 1964). R e sp ira tio n
in th e a n ta r c tic e u p h a u sid E u p h a u sia superba in ­
creases fro m 0° to 5 °C, b u t n o f u rth e r in c re ase o ccu rs
a t h ig h e r te m p e r a tu re s ; in d e ed , te m p e ra tu re s a b o v e
4 °C a re le th a l w ith in 24 h (M c W h i n n i e , 1964). T h e
d ev e lo p m e n ta l r a te o f 0 . validus em b ry o s m a y also
in c re ase w ith te m p e ra tu re , u p to a b o u t 4° to 5 °C , b u t
d elete rio u s effects o f h ig h e r te m p e ra tu re s m a y w ell
c o u n te r a n y f u rth e r s tim u la to ry effects. I t is also o f
in te r e s t t h a t th e tim e to cleavage w as h a lv e d a t 5 °C ;
p e rh a p s th e d is ru p tiv e effects o f 5 °C a r e less p ro ­
n o u n c e d o n th e re la tiv e ly few en zy m e s y ste m s in v o lv e d
in v e ry e a rly d e v e lo p m e n t, th a n la te r w h en m o re e n ­
zy m e c o o rd in a tio n p ro b a b ly com es in to play .
Mar. Biol.
Demersal behavior
T h e m a in ta in e d Odontaster va lid u s em b ry o s a n d
la rv a e s p e n t th e g r e a t m a jo rity o f th e tim e as b o tto m
sw im m ers. T h is b e h a v io r su g g ests t h a t th e y a re
d em ersal r a th e r th a n pelagic. S u ch a su g g e stio n is
su p p o rte d b y co n sid e ra tio n o f th e a n ta r c tic p la n k to n .
O nly a few p elag ic ec h in o d e rm la rv a e (in clu d in g a
b ip in n a ria ) a re k n o w n fro m th e a n ta r c tic (e.g. M o r ­
t e n s e n , 1913 b), a n d ec h in o d e rm la rv a e (as w ell as
tro ch o p h o res, veligers, a n d sim ila r la rv a e ) h a v e longb e e n n o ta b le b y th e ir s c a rc ity in th e a n ta r c tic p la n k to n
( H a r d y , 1960). B u n t (1960) m a d e a t le a s t m o n th ly
p la n k to n collectio n s a t M aw son, A n ta rc tic a , fro m 1
M ay 1956 to 10 F e b r u a r y 1957, a n d failed to fin d a
single ec h in o d e rm la rv a , y e t O. va lid u s is co m m o n a t
M aw son (J. S. B u n t , p e rso n a l co m m u n ic atio n ). E x te n ­
siv e p la n k to n collectio n s ta k e n fro m M cM urdo S o u n d
b etw e en D ecem b er, 1960 a n d D ecem b er, 1961, also
c o n ta in e d no ec h in o d e rm la rv a e (J. L . L i t t l e p a g e ,
p erso n a l co m m u n icatio n ). O. va lid u s is v e ry a b u n d a n t
in th e re la tiv e ly sh allo w w a te r o f M cM urdo S o u n d
(D e a r b o r n , 1967) a n d , e x c e p t fo r a p o ssib le b rie f
e a rly p elagic p erio d , th e em b ry o s a n d la rv a e m u s t b e
d em ersal in h a b it.
O th e r ech in o d erm a w ith in d ire c t d e v e lo p m e n t also
h a v e d em ersal em b ry o s a n d la rv a e . N e w t h (1925)
fo u n d t h a t b la stu la e a n d e a rly g a s tru la e o f Astropecten
irregularis sw am n e a r th e b o tto m o f h is c u ltu re d ish es
(he d id n o t m e n tio n th e b e h a v io r o f la te r sta g es), a n d
M o r t e n s e n (1921) re p o rte d th e sa m e b e h a v io r fo r
b ip in n a ria o f P a tiria pectin ifera a n d E vasterias
troscheli. M o r t e n s e n (1921) also n o te d t h a t th e
em b ry o s a n d p lu te i o f th e ec h in o id L a g a n u m diplopora
sw am n e a r th e b o tto m o f th e c u ltu re dishes. M oreover,
th e a n ta r c tic ec h in o id S terechinus n eu m a yeri p ro b a b ly
d ev elo p s th ro u g h p lu te u s stag es, y e t th e se a re ra re in
th e p la n k to n a n d p ro b a b ly d em ersal in h a b it ( P e a r s e
a n d G i e s e , 1966).
D em e rsal la rv a e t h a t a r e m o rp h o lo g ic ally sim ila r
to c o m p a ra b le p elag ic la rv a e h a v e b e e n r e p o rte d fo r
o th e r p h y la . S a n d e r s (1963) fo u n d t h a t th e d e m ersal
ce p h alo ca rid , m y sta c o c a rid , a n d h a rp a c tic o id copepod n a u p lii a re v e ry sim ila r to p elag ic ca la n o id
co p ep o d n au p lii. T h is s im ila rity “ . . . i s d u e to th e
f a c t t h a t th e y m o v e a n d feed in th e sa m e m a n n e r, one
sw im m in g th r o u g h th e w a te r a n d feed in g o n fine
su sp e n d e d m a tte r, th e o th e r m o v in g o n th e b o tto m
a n d feed in g o n a d e tr ita l m a te ria l s u sp e n d e d b y a
sw eeping a c tio n o f th e (ap p e n d ag es)” (S a n d e r s , 1963,
p. 24). Y o u n g la rv a e o f th e p o ly c h a e te N e reis d iversi­
color off F in la n d also a re d e m ersal in h a b it, in th is case
sta y in g o u t o f th e low su rfa c e salin ities, b u t la te r
sta g es w ith w id er to le ra n c e s b eco m e p la n k to n ic
(S m i t h , 1964).
W ith th e e s ta b lis h m e n t o f a d e m ersal h a b it fo r
Odontaster va lid u s em b ry o s a n d la rv a e , in d ire c t
d e v e lo p m e n t in ech in o d e rm s ca n no lo n g e r b e v iew ed
as le ad in g o n ly to p elagic la rv a e (e.g. H ö r s t a d i u s ,
1939 ; T h o r s o n , 1950 ; F e d e r a n d C h r i s t e n s e n , 1966).
Vol. 3, No. 2,1969
J. S.
P ea rse
: Development of embryos and larvae of Odontaster
I n d eep seas as w ell as p o la r seas, in d ire c tly d evelo p in g
em b ry o s a n d feeding la rv a e o f ec h in o d e rm s t h a t a re
d em ersal m a y b e o f m o re im p o rta n c e th a n p re v io u s ly
th o u g h t. M o r t e n s e n (1921) n o te d t h a t d eep -sea
ech in o d erm s w ith p elag ic la rv a e h a d n e v e r b een
d efin itely fo u n d a n d , from th is a n d o th e r o b se rv a tio n s,
i t h a s b e e n g en eralized t h a t all d eep -sea an im als h a v e
n o n-pelagic, no n -feed in g la rv a e (e.g. T h o r s o n , 1950;
M a d s e n , 1961). 0 . va lid u s occurs to d e p th s o f a t le a st
914 m (C l a r k , 1963) a n d c a n b e co n sid ered as a
species o cc u rrin g in m o d e ra te ly deep w a te r (b a th y a l
zone) w ith non-pelagic, y e t feeding, la rv a e . S im ilarly ,
th e ec h in o id L a g a n u m diplopora fro m 800 m h a s p lu te u s
la rv a e t h a t a re p ro b a b ly d em ersal (M o r t e n s e n , 1921).
M ore re c e n tly , S c h o e n e r (1968) h a s g iv e n ev id en ce
t h a t a n a b y s sa l (1 to 4000 m ) o p h iu ro id h a s in d ire c tly
d ev elo p in g la rv a e t h a t a re lik ely to b e b o tto m feeders.
A s h a s long b e e n kn o w n , a n u n u su a lly h ig h p ro p o r­
tio n o f a n ta r c tic ec h in o d e rm s b ro o d th e ir em b ry o s a n d
la rv a e ( T h o m s o n , 1876; T h o r s o n , 1950). S ev eral
reaso n s h a v e b e e n p ro p o sed fo r th is h ig h inciden ce o f
b ro o d in g , in c lu d in g : (1) low su rfa ce sa lin ities d u e to ice
m e lt (Ö S T E R G R E N , 1912; H a r d y , 1960), a n d (2) p o o r
p la n k to n ic food cond itio n s, w ith a s h o r t su m m e r p ro ­
d u c tiv e perio d , w hich m ig h t fa v o r y o lk y r a th e r th a n
feeding la rv a e ( T h o r s o n , 1950). H a r d y (1960)
p o in te d o u t t h a t c ru sta c e a n la rv a e a re esp ecially
a b u n d a n t in th e a n ta r c tic p la n k to n a n d , b ec au se o f
th e ir th ic k cuticle, th e se m a y b e less v u ln e ra b le to
o sm o tic stresses th a n m o re d e lic a te la rv a e su c h as
th o se o f echin o d erm s. C o n sid eratio n o f th e p la n k to n of
M cM urdo S o u n d ( J . L . L i t t l e p a g e , p erso n a l co m ­
m u n ic atio n ), M aw son ( B u n t , 1960), a n d H e a rd I s la n d
( E a l e y a n d C h i t t l e b o r o u g h , 1956) s u p p o rts th is
h y p o th e sis. T h e m o s t a b u n d a n t m e ro p la n k te rs in
th e se a re a s a re y o u n g p o ly c h a e te s w h ich a re all w ell
se g m en ted a n d m a y h a v e a w ide s a lin ity to le ra n c e as
is fo u n d in c o m p arab le sta g es o f N ereis diversicolor
( S m i t h , 1964). A lso in d ic a tiv e o f th e im p o rta n c e o f
o ccasional low su rfa c e salin ities, a d u lt specim en s o f
Odontaster va lid u s h a v e som e coelom ic w a te r v o lu m e
c o n tro l t h a t m a y b e a n a d a p tio n to fre sh w a te r ru n o ff
( P e a r s e , 1967).
R e g ard le ss o f w h ich fa c to rs a r e im p o r ta n t in
re s tric tin g ec h in o d e rm a n d sim ila r la rv a e fro m p o la r
p elagic w a te rs, Odontaster validus is v e ry p ro b a b ly
resp o n siv e to th e se fa c to rs. T h e resp o n se, th o u g h , is
n o t b y th e d e v e lo p m e n t o f d ire c t d e v e lo p m e n t a n d
b ro o d in g , b u t b y th e d e m ersal b e h a v io r o f feed in g
la rv a e . T h is b e h a v io ra l resp o n se w eakens T h o r s o n ’s
(1950) p ro p o sal t h a t p o o r food co n d itio n s a re in v o lv e d
in lim itin g th e o cc u rre n ce o f p elagic p o la r la rv a e .
O. va lid u s la rv a e in d e e d m u s t feed, b u t th is sh o u ld be
n o m o re o f a p ro b le m th a n i t is fo r o th e r sm a ll an im als
in h a b itin g th e b o tto m .
Odontaster validus is a w id esp re ad a n ta r c tic
astero id , being circ u m c o n tin e n ta l a n d o cc u rrin g n e a r
isla n d s as fa r n o r th as S o u th G eorgia a n d th e B o u v e t
isla n d s (C l a r k , 1963). T h e d e v e lo p m e n t o f a p re d o m ­
15*
115
in a te ly d e m ersal la r v a w ith b rie f p elagic phases,
m a y b e co n sid ered a n a d a p tiv e “ co m p ro m ise,”
serv in g fo r effective d isp ersio n , y e t p re v e n tin g e x ­
cessive la rv a l w a sta g e in th e a p p a r e n tly h a z a rd o u s
a n ta r c tic su rfa ce w ate rs. T h e co m m o n a rc tic o p h iu ro id ,
Ophiocten sericeum , also h a s p a r tly d em ersal, p a r tly
pelag ic, em b ry o s a n d la rv a e ( P e a r s e , 1965), a n d th is
b e h a v io r m a y a c c o u n t fo r its w ide d istrib u tio n .
A lth o u g h m a n y p o la r ec h in o d e rm s h a v e d ire c t d ev e lo p ­
m e n t [acco rd in g to T h o r s o n (1950) p e rh a p s 9 5 % o f
th e p o la r species h a v e d ire c t d e v e lo p m e n t], th e re is
still a p a u c ity o f k n o w n p elag ic la rv a e to a c c o u n t fo r
th e re m a in in g species. T h is p a u c ity is esp ecially
e v id e n t w h en i t is co n sid ered t h a t co m m o n , w id e ­
sp re a d p o la r species (such a s Odontaster va lid u s a n d
Sterechinus n eu m a yeri o f th e A n ta rc tic a n d Ophiocten
sericeum a n d Strongylocentrotus drobachiensis o f th e
A rctic) h a v e in d ire c t d e v e lo p m e n t, w ith feed in g
la rv a e ( T h o r s o n , 1950). I t is lik e ly t h a t o th e r co m m o n
p o la r ech in o d erm s h a v e u n d e rg o n e la rv a l a d a p ta tio n s
le ad in g to d e m ersal b eh a v io r. F u tu r e in v e stig a to rs
sh o u ld b e esp ecially co g n iz a n t o f possible differences
in d is trib u tio n a l ran g e s b etw e en b ro o d in g species a n d
species w h ich m a y h a v e p re d o m in a te ly d em ersal,
feed in g la rv a e su c h as O. validus.
S um m ary
1. T h e d e v e lo p m e n t o f th e a n ta r c tic a ste ro id
Odontaster va lid u s is in d ire c t, a n d in c lu d es a feed in g
b ip in n a ria stage.
2. T h e r a te o f d e v e lo p m e n t o f O. va lid u s a t a m ­
b ie n t se a te m p e ra tu re s ( — 1 .5 °C) is e x tre m e ly slow ;
b la s tu la e fo rm n e a rly 2 d a y s a f te r fe rtiliz a tio n ,
g a s tru la tio n beg in s a f te r 7 d a y s a n d th e b ip in n a ria
d ev elo p s in a b o u t 40 to 55 d a y s. T h e r a te o f d ev e lo p ­
m e n t a f te r cleav ag e is n o t in c re a se d a t + 5 °C. T h e
r a te o f d e v e lo p m e n t to g a s tru la tio n is sim ila r to t h a t
o f m o s t tro p ic a l a n d te m p e r a te a ste ro id s i f co m p en sa­
tio n is m a d e fo r te m p e ra tu re differences, a n d th e r e is
no ev id en ce o f te m p e r a tu re a d a p ta tio n . P o s t-g a s tru la
d e v e lo p m e n ta l r a te is e v e n m u c h slow er th a n w o u ld be
e x p e c te d fro m stu d ie s on a s te ro id s o f o th e r areas.
3. T h e em b ry o s a n d la rv a e a re la rg e ly d em ersal in
h a b it. T h e y s p e n d m o s t o f th e tim e o n th e b o tto m o f
c u ltu re d ish e s a n d a re a b s e n t in p la n k to n . T h is
b e h a v io r p ro te c ts th e la rv a e fro m e x p o su re to a p p a r e n t
h a r s h co n d itio n s o f t h e a n ta r c tic su rfa c e w a te r, a n d is
an alo g o u s in effect t o b ro o d in g in m a n y o th e r a n ta rc tic
fo rm s. I t is su g g e sted t h a t d e m e rsa l feeding la rv a e m a y
b e im p o r ta n t fo r th e d isp e rsal o f b o th p o la r a n d deepse a echinoderm s.
Acknowledgments. This work was begun while doing
predoctoral research with Stanford University. I t was support­
ed in p art by grants to Dr. D. E. W o h l s c h l a g from the Office
of Antarctic Programs, U.S. National Science Foundation,
and in p art through a contract with the Smithsonian In stitu ­
tion using funds from the Office of Antarctic Programs,
thank Dr. D. E. E p e l , Dr. J . J. G o x o r , Dr. J . W . H e d g p e t h ,
Dr. J. L. L i t t l e p a g e , and B. K. M c C a w for criticizing the
manuscript, and K . T. P e a r s e for preparing the illustrations.
116
J.
S. P earse
: Development of embryos and larvae of Odontaster
L iteratu re cited
J. S.: Introductory studies: hydrology and plankton,
June, 1956 — February, 1957. A. N. A. R. E. Rep. (Ser. B)
3 ,1 —135 (1960).
C l a r k , H. E. S.: The fauna of the Ross Sea. P t 3. Asteroidea.
Bull. N. Z. Dep. scient, ind. Res. 151, 1—84 (1963).
C o s t e l l o , D. P., M. E. D a v i d s o n , A. E g g e r s , M. H. Fox and
C. H e n l e y : Methods for obtaining and handling marine
eggs and embryos, 247 pp. Woods Hole, Mass.: Marine
Biological Lab. 1957.
D e a r b o r n , J. H. : The fauna of the Ross Sea. P t 5. Stanford
University invertebrate studies in the Ross Sea 1958—61 :
general account and station list. Bull. N. Z. Dep. scient,
ind. Res. 176, 31—47 (1967).
E a l e y , E. H. M. and R. G. C h i t t l e b o r o u g h : Plankton,
hydrology and marine fouling a t H eard Island. Interim
Rep. Aust. natn. Antarct. Res. Exped. 15, 1—81 (1956).
F e d e r , H. and A. M. C h r i s t e n s e n : Aspects of asteroid
biology. In : Physiology of Echinodermata, pp 87—127.
Ed. b y R. A. B o o l o o t i a n . New York: Interscience Publ.
1966.
F i e l d , G. W. : The larvae of Asterias vulgaris. Q. J1 microsc.
Sei. 34, 105—128 (1892).
G e m m il l , J. F .: The development and certain points in the
adult structure of the starfish Asterias rubens L. Phil. Trans.
R. Soc. (B) 205, 213—294 (1914).
— The larva of the starfish Porania 'pulvillus (0. F. M.), Q.
J1 microsc. Sei. 61, 27—50 (1915).
G r e e r , D. L.: Studies on the embryology of Pycnopodia
helianthoides (B r a n d t ) Stimpson. Pacif. Sei. 14, 280—285
(1962).
H a r d y , A.: Remarks. In : A discussion on the biology of the
southern cold temperate zone. Proc. R. Soc. (Ser. B) 152,
641—642 (1960).
H ö r s t a d i u s , S.: Über die Entwicklung von Astropecten
aranciacus L. Pubbl. Staz. zool. Napoli 17, 222—312 (1939).
J u s t , E. E .: Basic methods for experiments on eggs of marine
animals, 89 pp. Philadelphia: P . Blakiston’s Son & Co.
1939.
L a r s e n , E. J . : The laboratory culture of the larvae of Asterias
forbesi. In : Culture methods for invertebrate animals,
p p 5 5 0 — 5 5 3 , Ed. by P. S. G a l t s o f f , F. E. L u t z , P. S.
W e l c h and J . G . N e e d h a m . Ithaca, New York: Comstock
Publ. Co., Inc. 1 9 3 7 .
L i t t l e p a g e , J . L. : Oceanographic investigations in McMurdo
Sound, Antarctica. In : Biology of the Antarctic Seas. 2.
Antarctic Res. Ser. 5, 1—38 (1965).
M c W h i n n i e , M . A. : Temperature responses and tissue respira­
tion in antarctic Crustacea with particular reference to the
krill Euphausia superba. In : Biology of the Antarctic Seas.
1. Antarctic Res. Ser. 1, 63—72 (1964).
M a d s e n , F. J. : On the zoogeography and origin of the abyssal
fauna in view of the knowledge of the Porcellanasteridae.
Galathea Rep. 4, 177—218 (1961).
M o r t e n s e n , T. : On the development of some British echino­
derms. J . mar. biol. Ass. U. K. 10, 1—18 (1913 a).
— Die Echinodermenlarven der Deutschen Sud-polar Expedi­
tion 1901—1903. D t. Südpol.-Exped. 14 (Zool. 6), 69—111
(1913b).
B unt,
Mar. Biol.
— Studies of the development and larval forms of echino­
derms, 261 pp. Copenhagen: G. E. D. Gad 1921.
— Contributions to the study, of the.development and larval
forms of echinodernis 1 and IT. K. danske Vidensk. Selsk.
Skr. (Naturv. — math. Afd.) Raekke 9. 4 (1), 1—39 (1931).
— Contributions to the study of the development and larval
forms of echinoderms III. K. danske Vidensk. Selsk. Skr.
(Naturv. — math. Afd.) Raekke 9. 7 (1), 1—65 (1937).
— Contributions to the study of the development and larval
forms of echinoderms IV. K. danske Vidensk. Selsk. Skr.
(Naturv. — math. Afd.) Raekke 9. 7 (3), 1—59 (1938).
N e w m a n , H. H .: An experimental analysis of asymmetry in
the starfish Patiria miniata. Biol. Bull. mar. biol. Lab.,
Woods Hole 49, U l —138 (1925).
N e w t h , H. G. : The early development of Astropecten irre­
gularis with remarks on duplicity in echinoderm larvae.
Q. J1 microsc. Sei. 69, 520—554 (1925).
Ö S T E R G R E N , H. : Uber die Brutpflege der Echinodermen in den
südpolaren Küstengebieten. Z. wiss. Zool. 101, 325—341
(1912).
P e a r s e , J . S. : Early development of the antarctic asteroid
Odontaster validus K o e h l e r . A m . Zool. 2 , 4 3 6 ( 1 9 6 2 ) .
— Reproductive periodicities in several contrasting popula­
tions of Odontaster validus K o e h l e r , a common antarctic
asteroid. Biology of the Antarctic Seas. 2. Antarctic Res.
Ser. 5, 39—85 (1965).
— Antarctic asteroid Odontaster validus: constancy of repro­
ductive periodicities. Science, N. Y. 152, 1763—1764
(1966).
— Coelomic water volume control in the antarctic sea-star
Odontaster validus. Nature, Lond. 216, 1118—1119 (1967).
— and A. C. G t b s e : Food, reproduction and organic constitu­
tion of the common antarctic echinoid Sterechinus neu­
mayeri (M e i s s n e r ). Biol. Bull. mar. biol. Lab., Woods Hole
130, 387-401 (1966).
S a n d e r s , H. L. : The Cephalocarida. Functional morphology,
larval development, comparative external anatomy. Mem.
Conn. Acad. Arts Sei. 15, 1—80 (1963).
S c h o e n e r , A.: Evidence for reproductive periodicity in the
deep sea. Ecology 49, 81—87 (1968).
S m i t h , R. I. : On the early development of Nereis diversicolor
in different salinities. J. Morph. 114, 437—463 (1964).
T h o m s o n , C. W. : Notice of some peculiarities in the mode of
propagation of certain echinoderms of the Southern Sea.
J . Linn. Soc. (Zool.) 13, 55—79 (1876).
T h o r s o n , G.: Reproductive and larval ecology of marine
bottom invertebrates. Biol. Rev. 25, 1—45 (1950).
W o h l s c h l a g , D. E .: The biological laboratory and field
research facilities a t the United States “McMurdo” Station,
Antarctica. Polar Rec. 11, 713—718 (1963).
— Respiratory metabolism and ecological characteristics of
some fishes in McMurdo Sound, Antarctica. Biology of the
Antarctic Seas. 1. Antarctic Res. Ser. 1, 33—62 (1964).
Author’s address: Dr. J . S. P e a r s e
Kerckhoff Marine Laboratory
California Institute of Technology
101 Dahlia Street
Corona del Mar
California 92625, USA
D ate of final manuscript acceptance: March 26, 1969. Communicated by G. L. Voss, Miami