Illustrated key for the identification of brachyuran zoeal stages (crustacea decapoda) in the plankton of peter the great bay (sea of japan)

Abdominal somites 3–5 with poorly developed posterolat-eral spines Figure 4B, C; furcal rami without latposterolat-eral and dorsal spines Figure 4B or with lateral spines only Figure 4C.

Illustrated key for the identification of

brachyuran zoeal stages (Crustacea:

Decapoda) in the plankton of Peter

the Great Bay (Sea of Japan)

elena s kornienko and olga m korn

Institute of Marine Biology, Far East Branch, Russian Academy of Sciences, 17 Pal’chevskogo Street, 690041 Vladivostok, Russia

A dichotomous identification key for brachyuran zoeal stages from Peter the Great Bay (Russian waters of the Sea of Japan) is provided for the first time The key covers 16 taxa identified to species level and uses only the most conspicuous external char-acters of larvae that are easy to observe under a stereomicroscope without specimens dissection The key is based on the accounts by various authors and new original descriptions of larvae obtained both from plankton samples and from labora-tory culture Brief descriptions of larvae of 16 brachyuran species are also included

Keywords:zoea, Brachyura, crab, identification key, plankton, Sea of Japan

Submitted 15 May 2008; accepted 4 August 2008; first published online 16 October 2008

I N T R O D U C T I O N

Larval development is one of the most important periods of

the decapod life cycle; recruitment does not occur unless the

larval period is completed Larval data can be useful in

evalu-ating species diversity in a region and in specifying the

repro-duction time of brachyuran species Morphological features of

larvae are complementary characters for crustacean taxonomy

and phylogeny The study of larvae is important for the

problem of introduced species arriving in ballast waters or

on fouled ships However, insufficient attention has been

paid to decapod larval development in the Russian Far East

Seas Many keys exist for the identification of brachyuran

larvae in different regions of the World Ocean (Ingle, 1992;

Paula, 1996; Ba´ez, 1997; Pessani et al., 1998; Anosov, 2000;

Puls, 2001; Santos & Gonza´lez-Gordillo, 2004; Rice &

Tsukimura, 2007), but only one taxonomic guide is known

for the Sea of Japan (Konishi, 1997) There is no

comprehen-sive key for identification of the brachyuran larvae in Russian

waters of the Sea of Japan; however, the species list of this

region considerably differs from that of coastal waters of

Japan The aim of this work is to provide a key for the

identi-fication of brachyuran larvae in Peter the Great Bay

M A T E R I A L S A N D M E T H O D S

The key is based on the accounts previously published by

various authors (Table 1) and new original descriptions of

brachyuran larvae both taken from plankton samples and

reared from ovigerous crab females in the laboratory

Zooplankton was sampled in Vostok Bay (inner bay of Peter the Great Bay, Sea of Japan) between May and November 2002 using a Norpac net with a ring diameter of

40 cm and a filtering cone made of a 168 mm mesh, and in Amursky and Ussurijsky Bays (inner bays of Peter the Great Bay, Sea of Japan) between April and October 2007 using a Juday net with a ring diameter of 38 cm and a filtering cone made of a 168 mm mesh (Figure 1)

It is very difficult to identify the larvae (especially the larvae

of congeneric species) using drawings and descriptions of different authors in more or less detail So, zoeae of most con-sidered species were obtained under the laboratory conditions This material was used for the construction of the key and the original figures

Ovigerous crab females were maintained in an aerated sea-water aquarium until larvae hatched After hatching, larvae were concentrated at the edge of the aquarium using a point-light source and transferred to 1-l glass vessels with filtered and UV-sterilized seawater and reared to the megalopal stage The density of larvae was about 100 specimens l21 The water in the vessels was changed daily The larvae were fed with newly hatched nauplii of Artemia salina Very small zoea of varunid and pinnotherid crabs were reared using nauplii of the rhizoce-phalan crustacean, Polyascus polygenea, as a food Earlier, this method was described in detail (Kornienko & Korn, 2005a) All larvae were fixed in 4% formaldehyde for light micro-scopic studies

The dichotomous identification key is based mainly on external morphological characters, which are easy to observe under a stereomicroscope MBS-10 without specimen dissec-tion When these features are insufficient, the morphology and setation of appendages has been included Moreover, new original figures were provided to make identification easier The outlines of the larvae were drawn using a camera lucida attached to a binocular Ergaval microscope (Carl Zeiss Jena)

Corresponding author:

E.S Kornienko

Email: kornielena@mail.ru

The key was constructed for zoea I, but the characters used

in the key do not change or change slightly through the

suc-cessive zoeal stages, with the exception of peculiar cases

Main characters of brachyuran zoea used for the identification

are represented in Figure 2

R E S U L T S

Key for the identification of brachyuran zoea I

(interspecific distinctions)

1a Carapace with rostral, dorsal and lateral spines

(Figure 3A) 2

1b Carapace with rostral spine only (Figure 3B) or with rostral and dorsal spines (Figure 3C), lateral spines absent 11 2a Abdominal somites 3 – 5 with well developed posterolat-eral spines; furcal rami with latposterolat-eral and dorsal spines (Figure 4A) 3 2b Abdominal somites 3–5 with poorly developed posterolat-eral spines (Figure 4B, C); furcal rami without latposterolat-eral and dorsal spines (Figure 4B) or with lateral spines only (Figure 4C) 7 3a Furcal rami longer than proximal part of telson; dorsal and lateral furcal spines short (Figure 5A) 4 3b Furcal rami shorter than proximal part of telson; lateral furcal spines long (Figure 5B, C) 6 4a All carapace spines spinulated; dorsal spine straight; posterolateral spines longer than half abdominal somite; each furcal ramus with three spines Chionoecetes opilio (Figure 11A)

Fig 2 Main characters used for the identification of brachyuran zoea Fig 1 Map showing the sampling area.

Table 1 List of species and sources of descriptions of brachyuran zoeae included in the identification key.

Oregonidae Chionoecetes opilio (O Fabricius, 1788) Kurata, 1963b; Motoh, 1973; Haynes, 1973, 1981 Pisidae Pisoides bidentatus (A Milne-Edwards, 1873) Kurata, 1969; Kornienko & Korn, 2007

Telmessus cheiragonus (Tilesius, 1812) Kurata, 1963a

Hemigrapsus sanguineus (De Haan, 1835) Hwang et al., 1993; Kornienko et al., 2008

H penicillatus (De Haan, 1835) Hwang & Kim, 1995; Kornienko et al., 2008

H longitarsis (Miers, 1879) Park & Ko, 2002; Kornienko et al., 2008

[Lateral spines long, slightly shorter dorsal and

rostral spines Antenna biramous; protopod

spinu-lated, approximately equal rostral spine; endopod

with three terminal setae of unequal length

Lateral knobs on abdominal somites 2 – 3 long,

those of third one reach end of the same somite

Larvae found from April to July.]

4b All carapace spines smooth; dorsal spine slightly curved; posterolateral spines shorter than half abdominal somite; each furcal ramus with two spines 5 5a Abdominal somite 2 with a pair of lateral knobs; out-ermost pair of inner setae on posterior telson margin dentated on inside surface (Figure 6A, A0); posterolateral spines very short in zoea I and considerably lengthen in successive stages Cancer amphioetus (Figure 11B)

[Antenna biramous; protopod with two rows of spinules, nearly half of rostral spine; exopod with

Fig 6 Abdomen and telson of zoea in Cancer amphioetus (A, A 0 ) and Charybdis japonica (B) (after Yatsuzuka et al., 1984).

Fig 4 Abdomen and telson of zoea in Chionoecetes opilio (A), Tritodynamia

rathbuni (B) and Pisoides bidentatus (C).

Fig 3 Carapace of zoea in Eriocheir japonicus (A), Sakaina yokojai (B) and

Pisoides bidentatus (C).

Fig 5 Telson of zoea in Chionoecetes opilio (A), Telmessus cheiragonus (B) and Erimacrus isenbeckii (C).

two terminal setae of unequal length Larvae

found from June to September.]

5b Abdominal somites 2 and 3 with a pair of lateral knobs; all

inner setae on posterior telson margin plumodenticulate;

posterolateral spines prominent in all zoeal stages

(Figure 6B) Charybdis japonica (Figure 11C)

[Antenna biramous; protopod with two rows of

spinules, nearly half of rostral spine; exopod with

two terminal setae of unequal length Larvae not

found yet.]

6a Abdominal somite 2 with a pair of lateral knobs;

postero-lateral spines of somite 4 shorter somite 5; postero-lateral telsonal

spine shorter than half furcal ramus; each furcal ramus

with three inner setae (Figure 5B)

Telmessus cheiragonus (Figure 11D)

[Dorsal spine straight; rostral and dorsal spines

spinulated in distal part Antennal protopod

spi-nulated, shorter than rostral spine; exopod with

two nearly equal setae Abdominal somites 3 – 5

with long posterolateral spines Each furcal

ramus with three spines: one long lateral spine

and two short dorsal spines Larvae found in

April and May.]

6b Abdominal somites 2 and 3 with a pair of lateral knobs;

posterolateral spines of somite 4 shorter than somite 5;

lateral telsonal spine longer than half furcal ramus; each

furcal ramus with four inner setae (Figure 5C)

Erimacrus isenbeckii (Figure 11E)

[Dorsal spine straight; rostral and dorsal spines

spinulated in distal part Antennal protopod

spi-nulated, shorter than rostral spine; exopod with

two nearly equal setae Abdominal somites 3 – 5

with long posterolateral spines Each furcal

ramus with three spines: long lateral spine and

two short dorsal spines Larvae found in April

and May.]

7a Lateral carapace spines arranged as in typical brachyuran

larvae; all abdominal somites cylindrical; telson triangular;

furcal rami without spines (Figure 7A, B) 8

7b Lateral carapace spines arranged more ventrally than in typical brachyuran zoea; abdominal somites 4 – 5 not cylindrical but laterally expanded; telson subrectangular; furcal rami without spines or with minute lateral spines (Figure 7D – F) 10 8a Dorsal and rostral spines longer than carapace; dorsal car-apace spine straight; antenna uniramous (Figure 8A) Tritodynamia rathbuni (Figure 11F)

[Antennal protopod with two rows of spinules and with short seta near base Posterolateral spines on abdominal somites 3 – 5 highly reduced Larvae found from June to September.]

8b Dorsal and rostral spines slightly shorter than carapace; dorsal carapace spine slightly curved; antenna biramous (Figure 8B) 9

Fig 7 Carapace of zoea in Tritodynamia rathbuni (A) and Pinnaxodes

mutuensis (C); telson of zoea in Tritodynamia rathbuni (B); Pinnaxodes

mutuensis (D), Pinnixa rathbuni (E) and Sakaina yokoyai (F).

Fig 8 Antenna and carapace of zoea in Tritodynamia rathbuni (A) and Eriocheir japonicus (B).

Fig 9 Antenna, antennule and abdomen of zoea in Eriocheir japonicus (A) and Hemigrapsus sanguineus (B).

9a Abdominal somites 2 – 4 with a pair of lateral knobs

(lateral knobs on somite 4 disappear in successive

stages); antennule with 2 aesthetascs; antennal exopod

nearly half protopod (Figure 9A)

Eriocheir japonicus (Figure 11G)

[Antennal exopod as tapering spine with two

small unequal subterminal setae Larvae found

from June to September.]

9b Abdominal somites 2 – 3 with a pair of lateral knobs;

antennule with 3 aesthetascs; antennal exopod nearly

2/3 protopod (Figure 9B)

Hemigrapsus sanguineus, H penicillatus, H longitarsis

(Figure 11H)

[Antennal exopod as tapering spine with small

unequal subterminal setae Larvae found from

June to September.]

10a Abdominal somites 4–5 expanded; furcal rami shorter

than proximal part of telson, with minute lateral spines

(Figure 7D)

Pinnaxodes mutuensis (Figure 11I)

[Antenna uniramous; protopod with two rows of

spinules Lateral telsonal margins slightly convex

Larvae found in July.]

10b Abdominal somite 5 as a horseshoe; furcal rami longer

than proximal part of telson, without lateral

spines Pinnixa rathbuni (Figure 11J)

[Rostral and dorsal carapace spines straight

Antenna uniramous; protopod with two rows of

spinules and with short seta near base Furcal

rami without spines (Figure 7E) Larvae found

from May to November.]

11a Carapace with rostral spine only

Sakaina yokoyai (Figure 11K)

[Antenna uniramous; protopod with two rows of

spinules Abdominal somites 4 – 5 as a horseshoe

Telson nearly rectangular; furcal rami shorter

than proximal part of telson, without spines;

median notch virtually absent (Figure 7F)

Larvae found in June – August.]

11b Carapace with rostral and dorsal spines (Figure 10)

12

12a Rostral and dorsal spines three times longer than

cara-pace; dorsal spine straight

Paradorippe granulata (Figure 11L)

[Dorsal spine with blunt spinules, rostral spine with

acute spinules Antenna biramous; protopod and

exopod sub-equal Abdominal somite 2 with pair

of lateral knobs Telson narrow and long, with a

pair of lateral spines; furcal rami twice exceeding

proximal part of telson Posterior telsonal margin

with two inner setae only (Figure 10A, A0) Larvae

found in July and August.]

12b Rostral and dorsal spine shorter than carapace, dorsal

spine slightly curved (Figure 10B)

Pugettia

quadridens, Pisoides bidentatus (Figure 11M)

[Rostral spine nearly one-third antenna; dorsal spine with sparse blunt spinules Antenna bira-mous; protopod and exopod sub-equal

Abdominal somites 2 with a pair of lateral

Fig 10 Carapace (A) and telson (A 0 ) of zoea in Paradorippe granulata; carapace of zoea in Pugettia quadridens (B).

knobs Furcal rami with lateral spines (Figure 4C).

Larvae found from June to September.]

Most Brachyura from Peter the Great Bay pass through five

zoeal stages Majiod crabs (Pisoides bidentatus, Pugettia

quad-ridens, and Chionoecetes opilio) have an abbreviated

develop-ment including only two zoeal stages Two of three

pinnotherid crabs also undergo an abbreviated development:

Sakaina yokoyai passes through probably three zoeal stages;

Pinnaxodes mutuensis, through four zoeal stages Four zoeal

stages are known also for Paradorippe granulata

Different zoeal stages of brachyuran crabs (age

distinc-tions) are easily determined using the number of natatory

setae on the exopods of maxillipeds, the number of setae

along the posterior telsonal margin, the presence of

unira-mous or biraunira-mous pleopod buds and some other

morphologi-cal features The same stages in the species with abbreviated

development are more advanced in the number of characters

over those of the species with longer development

Identification of different zoeal stages of

brachyuran crabs (age distinctions)

Zoea I Eyes sessile; exopod of maxilliped each with 4 natatory

setae; abdomen consists of 5 somites and telson; posterior

telsonal margin with 3 þ 3 setae (in Paradorippe granulata,

posterior telsonal margin with two setae only in all zoeal stages)

Zoea II Eyes stalked; exopod of maxilliped each with 6 nata-tory setae; in most species abdomen consists of 5 somites and telson; pleopod buds absent; posterior telsonal margin with

3 þ 3 setae In Pisoides bidentatus, Pugettia quadridens, and Chionoecetes opilio, zoea II is the last stage; hence, the sixth somite is delineated, somites 2–6 with biramous pleopod buds In Sakaina yokoyai, pleopod buds uniramous In Charybdis japonica and Chionoecetes opilio, posterior telsonal margin with 4 þ 4 setae

Zoea III Exopod of maxilliped each with 8 natatory setae; the sixth somite delineated, with the exception of Pinnixa rathbuni which has 5 somites in all zoeal stages In Cancer amphioetus, Trithodynamia rathbuni, Erimacrus isenbeckii, Telmessus cheiragonus, Eriocheir japonicus and Hemigrapsus species, posterior telsonal margin with 4 þ 4 setae; in Charybdis japonica and Pinnaxodes mutuensis, with additional small unpaired setae In Sakaina yokoyai, pleopod buds biramous

Zoea IV Exopod of maxilliped each with 10 natatory setae; somites 2 – 6 with uniramous pleopod buds In Cancer amphioetus and Tritodynamia rathbuni, posterior telsonal margin with 5 þ 5 setae

Zoea V Exopod of maxilliped each with 12 natatory setae; pleopod buds biramous In Eriocheir japonicus and Hemigrapsus species, posterior telsonal margin with 5 þ 5 setae

Fig 11 Lateral view of zoea in Chionoecetes opilio (A), Cancer amphioetus (B), Charybdis japonica (C), Telmessus cheiragonus (D), Erimacrus isenbeckii (E), Tritodynamia rathbuni (F), Eriocheir japonicus (G), Hemigrapsus sanguineus (H), Pinnaxodes mutuensis (I), Pinnixa rathbuni (J), Sakaina yokoyai (K), Paradorippe granulata (L), and Pisoides bidentatus (M).

D I S C U S S I O N

According to Adrianov & Kussakin (1998), 20 brachyuran

species belonging to 8 families and 16 genera inhabit Peter

the Great Bay (Russian waters of the Sea of Japan) We

found larvae of only 16 species from 9 families and 14

genera occurring in the plankton of Peter the Great Bay

(Table 1) To date, we have not found both adults and

larvae of Goetice depressus (de Haan, 1835), Helice tridens

de Haan, 1833, and Paradromia japonica (Henderson,

1888) According to Vassilenko (1990), adult specimens of

Pinnixa tumida Stimpson, 1858 are found only in Possyet

Bay (eastern Peter the Great Bay) Brachyuran larvae occur

in Peter the Great Bay from April to November

Zoea of each species represented in this key has been

previously described Only the larvae of Sakaina yokoyai

are not known yet; however, the morphology of closely

related species, S japonica, has been described (Konishi,

1981a) Both adults and larvae of S yokoyai are rarely

found in Peter the Great Bay, so we failed to obtain the

total series of their larval stages Nevertheless, we believe

that S yokoyai, like S japonica, passes through three zoeal

stages

Frequently, the distinction between larvae of congeneric

species is based on slight differences The larvae of

congene-ric species, described on the basis of specimens hatched in

the laboratory from ovigerous females, can be identified

only to the generic level when collected in nature In our

case, the specific identification of three Hemigrapsus

species (H sanguineus, H penicillatus and H longitarsis) is

very difficult Zoea I and zoea II of these species are nearly

identical The larvae are distinguishable only from zoea III

Zoea III – V of Hemigrapsus species differ in the number of

dorsomedial setae on the abdominal somite I and in the

number of setae on the posterodorsal arch It is pertinent

to note that among the three Hemigrapsus species, zoea

and megalopa of H penicillatus differ greatly (Kornienko

et al., 2008) Despite the great similarity of larvae in

varunid crabs of the genera Hemigrapsus and Eriocheir, the

latter possess a number of distinctive features in all

develop-mental stages (Kornienko & Korn, 2005a; Kornienko et al.,

2008)

It was recently shown that zoea of Pisoides bidentatus and

Pugettia quadridens belonging to different families are also

nearly identical, with the exception of a more intensive

coloration of the latter Some differences appear only in

the megalopal stage Based on the larval similarity

(Kornienko & Korn, 2007) and high genetic identity of

adults (Zaslavskaya et al., 2007) these two species should

be assigned to one genus

The larvae of the other ten species belonging to different

families and genera are easy to identify in the plankton The

features used in the key were chosen to enable identification

of zoea to the species level and do not reflect any systematic

arrangement of decapod families

A C K N O W L E D G E M E N T S

The project was supported by the Far East Branch of the

Russian Academy of Sciences (grant no 06-III-A-06-164)

and by the Russian Foundation for Fundamental Researches

(grant no 08-04-00929)

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and Zaslavskaya N.I., Kornienko E.S and Korn O.M (2007) Genetic differ-ences between two spider crabs Pisoides bidentatus (A Milne-Edwards, 1873) and Pugettia quadridens (de Haan, 1839) (Decapoda: Brachyura: Majoidea) from the Sea of Japan Biochemical Systematics and Ecology 35, 750– 756.

Correspondence should be addressed to:

E.S Kornienko Institute of Marine Biology Far East Branch, Russian Academy of Sciences

17 Pal’chevskogo Street, 690041 Vladivostok, Russia email: kornielena@mail.ru