DESCRIPTIONS OF THE TblO PiEGALOPAL STAGES OF
LA)3OKATORY-REARED PINK SHRIMP, PANDALUS JORDANI
I NFORMTIOid REPORT
Michael J . Hosie
Fish Commission o f Oregon
Groundfish and Shrimp Investigations
April 1975
DESCRIPTIONS
OF THE ndo MEGALOPAL STAGES OF LABORATORY-REARED
PIi4K SHRIEIP, PANDUUS JORDANI
This report describes f o r the f i r s t time, megalopal stages o f the commercially
important pink shrimp, Prmdatus jordmri, w i t h a comparison w i t h previously published
l a r v a l studies.
This w i l l benefit future workers rearing t h i s species' larvae and
also i n i d e n t i f i c a t i o n o f i t s rnegalopae from plankton samples.
Published studies o f P. jordani larvae have been p r i m a r i l y r e s t r i c t e d t o
descriptions o f laboratory-reared zoeal stages.
t4odin and Cox (1967) c u l t u r e d t h i s
species through 11 t o 13 zoeal stages, w i t h only one shrimp surviving t o the f i r s t
p o s t l a r v a l (mega1opal ) stage.
This mega1opal stage was not described.
Lee (1969)
also reared P. jordani larvae but none survived past the eighth zoeal stage.
.
Peter Rothl isberg (Oregon State Uni v e r s i t y , Department of ~ o o l o ~ yPers
,
C m .)
reared P. jordani through 16, not y e t i d e n t i f i e d , l a r v a l stages w i t h a few i n d i v i d u a l s
surviving t o become j u v e n i l e shrimp.
Hosie (1975) reared P. jordani through 10 t o
12 zoeal stages and 2 megalopal stages, which are discussed i n t h i s paper.
SIETHODS AlJD i4ATERIALS
There i s confusion regardi ng terminology o f northeastern P a c i f i c ocean pandal i d
shrimp larvae.
This confusion applies t o use o f the words stage, larva, zoea,
megalopa, and postlarva.
I n t h i s paper, a stage denotes the period (intermoul t )
between successive ecdyses (Price and Chew 1972).
A l a r v a i s a young post-embryonic
form, morphologically d i s t i n c t from the mature adult.
the zoea and nlegalopa o f P. jordani.
This term i s applicable t o
l 4 i l liamson (1969) considered a zoea t o be
a l a r v a w i t h pleopods generally absent o r rudimentary and having natatory exopodi tes
on some o r a l l thoracic appendages.
P. jordani known t o occur i n nature.
The zoea i s the e a r l i e s t l a r v a l form of
Lee (1969) however, reported a pre-toea,
which emerged under unfavorable 1aboratory conditions
.
Pike and W i 11iamson (1969)
defined a pandal i d shrimp megalopa as the l a r v a l form i n which e i t h e r pleopods
become f u n c t i o n a l o r n a t a t o r y exopodites on t h e pereiopods are l o s t , o r both.
terminology has been adopted i n t h i s r e p o r t .
Their
They found morphological character-
i s t i c s a t rdetamorphosis t o t h e megalopa were n o t t h e same f o r a l l pandalid species
studied.
Modin and Cox (1967) and Lee (1969), used t h e ternis postlarva o r almost
a d u l t instead o f megalopa f o r P. jordrmi. These names are misleading because t h e
siegalopa i s a l a r v a l form morphologically d i s t i n c t from j u v e n i l e and a d u l t P. j o r d d .
The j u v e n i l e has the c h a r a c t e r i s t i c s o f t h e a d u l t , b u t i s sexually immature.
Ovigerous P. jordani were obtained i n f+larch 1971 by shrimp t r a w l o f f Coos Bay,
Oregon.
These shrimp were transported t o t h e F i s h Cormission o f Oregon marine
l a b o r a t o r y a t Newport, Oregon.
A d u l t shrimp were h e l d a l i v e i n t h e l a b o r a t o r y and
newly hatched l a r v a e obtained from them.
Culture techniques were those o f Hosie (1975).
During A p r i l 1971, 120 newly
hatched zoeae were p l aced in t o four 500-ml aerated transparent Erlenmeyer f l a s k s
(30 zoeae/flask),
water bath.
each containing 400 m l o f water.
The f l a s k s were h e l d i n a constant
Larvae were maintained u n t i l J u l y 1971 when t l i e experiment was terniinated.
A t each stage l a r v a e were measured from t h e a n t e r i o r t i p of the antenna1 scale t o
t h e p o s t e r i o r margin o f t h e telson.
Carapace lengths, from t h e base of t h e eyestal k
t o t h e p o s t e r i o r mid-dorsal edge, were a l s o obtained a t a l l stages.
Measurements
were made t o t h e nearest lower 0.5 mm u s i n g a m e t r i c r u l e r .
Transparent exuviae and dead l a r v a e were removed from t h e c u l t u r e system and
preserved i n 5% fornialin f o r morphological work.
t o 100% g l y c e r i n f o r d i s s e c t i o n .
dissected m a t e r i a l
Megalopae were l a t e r t r a n s f e r r e d
Temporary mounts i n g l y c e r i n were made o f t h e
.
Drawings of magalopae were made w i t h t h e a i d o f a d i s s e c t i n g microscope and a
compound microscope, both w i t h a camera l u c i d a attachment.
using a t y p i c a l i n d i v i d u a l from each megalopal stage.
I l l u s t r a t i o n s were made
Drawings were made o f t h e
whole animal ' s l a t e r a l view, antennule, antenna, f i r s t t h r e e pereiopods, second
p l eopod and t e l son.
Descriptions and measurements were obtained from f i v e f i r s t
stage mega1opae and f o u r second stage mega1opae.
DESCKIPTIOWS OF MEGALOPAL STAGES
Measurements and spine counts (Table 1) o f c u l t u r e d specimens of the two m e g a l o ~ a l
stages showed some v a r i a t i o n between i n d i v i d u a l s w i t h i n a stage.
However, these
d i fferences were n o t 1arge.
Table 1.
Stage
V a r i a t i o n i n number o f r o s t r a 1 spines and t e l s o n spines, carapace
lengths, and t o t a l lengths of 5 f i r s t megalopae and 4 second megalopae
P. jordani c u l t u r e d a t Newport, Oregon, Spring 1971.
Ros t r a l spines
Specimen dorsal v e n t r a l
Megalopa I
1
2
3
4-l /
5
Wegalopa I1
1
2
3
4
L/
Tel son spines
terminal 1a t e r a l
6
12
14
14
15
16
3
4
4
5
5
a
8
15
17
17
19
6
7
8
7
5
6
4
4
6
18
18
17.5
18.0
18.0
18
3.0
2.5
3.0
3.0
3.0
18
18
18
18
3.0
3.5
3.5
3.5
18.0
18.0
18.5
18.5
18
-
Carapace
Total
1ength (m) 1ength (mm)
-
-
18.0
Telson missing, making t e l son spine count and t o t a l l e n g t h measurement impossible.
F i r s t ihlegalopal Stage
The f i r s t megalopa (Fig. 1A) measures 17.5 t o 18
mm.
It i s d i s t i n g u i s h e d from
the l a s t toea1 stage by l a c k o f n a t a t o r y exopodi tes on t h e f i r s t three pereiopods.
The most apparent l a r v a l c h a r a c t e r i s t i c s s t i l l remaining a r e a t e l s o n w i t h more than
f o u r terminal spines and a rostrum s h o r t e r than t h e antenna1 scale.
Rostrum
- The
rostrum (Fig. 1A) has 12 t o 16 dorsal spines and 3 t o 5 v e n t r a l
spines.
Antennule
- The o u t e r f l a g e l l u m (Fig.
1B) i s s t i l l d i v i d e d i n t o 6 segments.
The smaller i n n e r f l a g e l l u m bears 7 segments, one more than t h e preceding stage.
Antenna
- The antenna
f l a g e l l u m (Fig. 1C) i s d i v i d e d i n t o 45 t o 50 segments.
Fig.
. I . , Pandalus j o r d a n i b t h b u n ,
view; B, anter~nube;.C,antenna,
f i r s t megalopa.
A, l a t e r a l
The antennal scale i s much larger than i n previous stages and i s assuming the squaretipped narrow form of the adult.
First pereiopod
exopodi t e
- The
f i r s t pereiopod (Fig. ID) bears only a rudimentary bud-li ke
.
-
Second pereiopod
This thoracic appendage (Fig. 1E) has 6 segments, w i t h 1 joint
appearing on the carpus of the chela f o r the f i r s t time.
I t also possesses a rudi-
nientary exopodi te.
Third pereiopod
- This
pereiopod (Fig. IF) has grown larger than in the preceding
stage and lacks a functional natatory exopodite.
- These swimming structures
Pleopods
(Fig. 1G) are essentially adult, being
longer and more setose than the preceding stage.
Telson
- The telson
(Fig. 16) bears 6 to 8 large spines on its convex terminal
margin and 18 smaf 1 , simple spines along the lateral margin.
This compares t o 10
terrninal spines and 14 lateral spines described by Ietodin and Cox (19.57) for the l a s t
zoeal stage.
The uropods are well developed and densely fringed with about 60 large,
heavi ly pl urnose natatory setae.
Second Meqalopal Stage
The second megalopa (Fig. 28) i s 18.0 to 18.5 mm long and can easily be separated
from previous stages by a rostrum extending t o the t i p of the antennal scale.
stage, however, i s s t i l l a larval fom.
This
In post-larval juvenile and adult P. jordmri
the rostrum extends beyond the antennal scale and i s , according to Rathbun (1904),
about 1.75 times longer than the carapace.
Also the second megalopae s t i l l have the
larval characteristic of rudimentary exopodites on the f i r s t 3 pereiopods.
Rostrum
- The rostrunt
6 to 8 ventral spines.
Antennule
-
(Fig. 2A) has 15 to 19 dorsal spines, 1 near the t i p , and
I t now projects as f a r as t h e t i p of the antennal scale.
The outer flagellum (Fig. 2B) i s divided into 10 segments. The
smaller inner flagellum bears 8 segments.
Antenna
- The antenna
flagellum (Fig. 2C) i s divided into over 100 segments and
Fig.
1.
P a n d a l u s j o r d a n i Ratkbun, f i r s t megalopa.
f i r s t , second and t h i r d p e r e i o p o d s r e s p e c t i v e l y .
Q
-
F,
Fig,
1.
P a n d a l u s J o r d a n i Rathbun, first megalopa,
p l e o p o d ; H, t e l s o n .
G,
second
Fig.
2.
-
Bandalus j o r d a n i Bathbun,
view; B, a n t e n n u l e ; C, antenna.
second megalopa.
A, l a t e r a l
i s e s s e n t i a l l y a d u l t , being almost as l o n g as t h e body.
The antenna1 scale i s
s i m i l a r t o t h e f i r s t megalopal stage.
F i r s t pereiopod
-
This t h o r a c i c appendage (Fig. 20) has 5 segments.
one more segment than tile f i r s t meyalopa.
Second pereiopod
- The l e f t
A rudimentary exopodite i s s t i l l present.
second pereiopod (Fig. 2E) has an e s s e n t i a l l y
a d u l t chela w i t h 10 t o 14 j o i n t s on t h e carpus.
present.
This i s
A bud-like exopodite i s s t i l l
The r i g h t second pereiopod has 5 t o 7 carpus j o i n t s .
-
T h i r d pereiopod
(Fig. 2F) has 6 segments, one more than found on f i r s t
megal opae, and a rudimentary exopod it e .
- The
Pleopods
pleopods (Fig. 2G) are e s s e n t i a l l y adult, being unchanged from
t h e preceding f i r s t mega7 opae.
Telson
spines.
- The t e l s o n
(Fig. 2H) has 4 t o 6 l a r g e terminal spines and 18 l a t e r a l
The uropods are e s s e n t i a l l y a d u l t , being l i t t l e changed from t h e f i r s t
rnegalopae
.
DISCUSSION
Results o f t h e study silowed a l a r g e r s i z e (Table 2) than ;lodin and Cox (1967)
and Lee (1969).
stage 10.
Lengths o f zoeae increased from 6.25 mm a t stage 1 t o 17.25 mm a t
Zoeae reared by Modin and Cox (1967) were 5.00 mm a t stage 1 and 14.30 mm
a t stage 10.
Lee (1969) used a c r i t e r i o n f o r measuring growth n o t comparable t o
t h i s study (Table 2).
Duration o f l a r v a l stages i n the two previous studies averaged
G t o 7 days, a s h o r t e r time than the 10 t o 25 days found i n t h i s study.
megalopae achieved a l e n g t h of 18.00 mm and megalopae 11, 18.25 mm.
F i r s t stage
Carapace lengths
o f larvae increased from 1.25 mm a t zoeal stage 1 t o about 3.75 mm i n t h e second
megalopal stage.
The morphology o f zoeae reared i n t h i s study were s i m i l a r t o those reported
by l4odin and Cox (1967) and Lee (1969).
Oifferences i n growth
as we1 1 as morphological
discrepancies, were probably caused by a combination o f factors, i n c l u d i n g d i f f e r i n g
populations o f shrimp and c o n t r a s t i n g r e a r i n g conditions (Table 3).
Fig.
2.
Pandalus Jordani Rathbun, second megalopa.
first, second, and third pereiopods respectively.
D
-
F,
Fig.
2.
Pandalus Jordan1 Bathbun, second megalopa.
pleopod; H, telson.
G, second
Table 2.
Comparison of s i z e of laboratory-reared P. jordmri
larvae between previous descriptions and present study
[lean Length (mm)
Stages
Modin & Cox (1957)
Lee (1969)1/
Hosie
Zoea
1
2
3
4
5
6
7
8
9
10
11
12
13
Megal opa
I
-1/
Length measured from anterior t i p of antenna1 scale t o posterior
margin of telson, except Lee (1969) where growth was gauged from
anterior of rostruni t o posterior of telson.
The 10 to 12 zoeal stages and two megalopal stages found may be aty~fealf o r
t h i s species.
P i ke and Wi 11i amson (1964) cul tured European panda1 id shrimp and
reported more larval stages than i ti natural conditions.
The number of larval stages
has also been found t o vary f o r pandalid shrimp i n nature (Karata 1964, Pike and
Ldi 11iamson 1964).
T h i s variation i n moulting among decapod l arvae has been suggested
by Broad (1957a, 1957b) t o be governed by external factors independent of r a t e of
developn~enl. fjence, the stages of laboratory-reared P. jordmri larvae should not
be thought of as inflexible, natural steps through which a l l individuals pass.
I t was not possible to determine if lengths o f most P. jordani larval stages
cultured were similar t o those i n nature.
However, carapace lengths of second
megalopal stage shrimp possibly were close t o those i n the ocean.
Cultured larvae
a t this stage has carapace lengths w i th a mode of 3.5 mm a t 95 days of age.
Lukas
Table 3.
Differences in Hearing Conditions Betvreen P. jorduni Larvae Cultured i n This Study
and Previous Experiments.
e
ood and
rigin of
~ontain'ers
Food Rate
Femald Shrimp
Author
Temperature
Sal in i ty
pH
Hosie
7.2C h 10C,+0.5C
3 0 ~ 1 0,+lO/oo
0
Unknown
500-ml transparent
aerated Erlenmeyer
flasks i n a constant
temperature water
bath.
Brine si~rimp
t~aupli i , fed
a t 15/ml of
rearing watar
Pacific Ocean
off Czntral
Oregon
Modin & Cox
(1967)
10C to 13C
Unknown
sea-water
from open
ocean
Unknown
Individual shrimp
compartmented i n
styrene containers
with screen bottoms,
suspended i n an.
aquarium maintained
i n a temperatureregulated cooling
table.
Brine shrimp
naupl i i , fed
a t unknown
concentration
Pacific Ocean
off Northern
California
Lee (1969)
13CS+0.2C
24. 1 ° / 0 0
7.8 average
400-ml aerated
p l a s t i c beakers
i n a recirculating
constant temperature
sea water system.
Brineshrimp
naupl i i s fed
a t an unknown
concentration
HoodCanal,
Puget Sound,
ljashington
average
and tlosie (1973) found 3.5 t o 5.5 nun (mode 4.5 mm) carapace lengths f o r approximately
75 t o 90 day o l d j u v e n i l e P. jordani c o l l e c t e d from o f f n o r t h e r n Oregon i n e a r l y
June 1970.
The d e s c r i p t i o n s o f these megalopal stages o f P. jordmti may prove valuable i n
f u t u r e plankton l a r v a l s t u d i e s f o r i d e n t i f i c a t i o n o f megalopae o f t h i s species.
I
recommend t h a t these d e s c r i p t i o n s be used o n l y as g u i d e l i n e s because o f known
differences between l a b o r a t o r y and n a t u r a l populations o f l a r v a e o f o t h e r species of
pandalid shrimp.
LITERATURE CITED
1957 a. L a r v a l development o f PaZaeomonetes pugio H o l t h u i s .
Broad, A.C.
B u l l . 112: 144-161.
Biol.
1957 b. The r e 1a t i o n s h i p between d i e t and 1a r v a l development of Palaeomonetes.
B i o l . B u l l . 112: 162-170.
Hosie, M.J.
1975. C u l t u r e methods and response o f l a b o r a t o r y reared p i n k shrimp
(PandaZus jordani) 1arvae t o s e l e c t e d simulated environmental f a c t o r s . F i s h
Comm. Ore. Inform. Rep. 19 p . (mimeogr.)
Kurata, ti. 1964. Larvae o f t i l e decapod Crustacea o f tlokkaido, 3. Panda1idae. B u l l .
(English t r a n s l a t i o n
Fish. Res.
Hokkaido reg. Fish. Res. Lab. 28: 23-34.
Board Can. Transl Series No. 693. )
.
.
-
Lee, Y .J. 1969. Larval development o f p i n k shrimp, ~andaiusjordan5 Rathbun reared
i n l a b o r a t o r y . M. Sc. Thesis, Univ. Washington, S e a t t l e . 62 p.
Lukas, G. and '1.3. Hosie. 1973. I n v e s t i g a t i o n o f t h e abundance and b e n t h i c
d i s t r i b u t i o n o f p i n k shrimp o f f t h e n o r t h e r n Oregon coast. Comm. Fish. Res.
F i s h Comm. Ore., F i n a l Rep.,
and Dev. Act, Contract 14-17-0001-2323.
J u l y 1, 1969 t o June 30, 1970. 45 p. (mimeogr.)
Modin, 3. C. and K. W. Cox. 1967. Post-embryoni c development o f l a b o r a t o r y reared
ocean shrimp, Pandalus jordani Rathbun. Crustaceana 13(2) : 197-219.
Pike, R.B. and D.I. b.lilliawson. 1964. The l a r v a e o f some species o f Pandalidae
Crustaceana 6(4) : 265-284.
(Decapoda)
.
and K.W. Chew. 1972. Laboratory r e a r i n g of spot shrimp l a r v a e (Pandalus
pbtycems) and d e s c r i p t i o n s of stages. J. Fish. Res. Board Can. 29(4):
413-422.
Price, V.A.
Rathbun, irJ. 1904. Decapod crustaceans o f t l i e northwest coast o f North America.
Harriman Alaska Exped. Ser. 10,210 p.
W i 11iamson, D. I. 1969.
16: 210-213.
idames o f 1arvae i n t h e Decapoda and Euphausiacea Crustaceana