Larval development of Acanthonyx lunulatus (Brachyura, Majidae, Epialtinae)

Journal of Plankton Research Vol.18 no.7 pp.1185-1200, 19%

Larval development of Acanthonyx lunulatus (Brachyura, Majidae, Epialtinae) G.Guerao1 and P.Abello3 'Departament de Biologia Animal (Artropodes), Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, E-08028 Barcelona, and 2Institut de Ciencies del Mar (CSIC), Passeig Joan de Borbd s/n, E-08039 Barcelona, Spain

Introduction Acanthonyx lunulatus (Risso, 1816) is a small majid crab known from the Mediterranean Sea and eastern Atlantic waters from Portugal to Namibia, including the Azores (Zariquiey-Alvarez, 1968; Manning and Holthuis, 1981). It lives attached to algae at depths of between ~0 and 20 m (Zariquiey-Alvarez, 1968). Some aspects of its biology are known, including its life cycle (Chaix, 1979; Sanz, 1989), relative growth and biometry (Sanz, 1986), and physiology (Chaix et ai, 1976; Chaix, 1984; Laugier and Chaix, 1984,1985). However, the knowledge of its larval development was, to date, incomplete. Cano (1893) was the first author to illustrate a larval stage attributed to A.lunulatus. Bourdillon-Casanova (1960) reported limited descriptions of the first and second zoeae from plankton material. Heegaard (1963) described a first zoea from laboratory-hatched material. The megalopa stage was, as yet, unknown. The larval development of other species of the genus Acanthonyx is only known for A.petiverii (see Hiyodo et ai, 1994), whereas complete descriptions of other species of the subfamily Epialtinae (=Acanthonychinae) are only available for four species: Epialtus dilatatus (see Yang, 1968), Taliepus dentatus (see Fagetti and Campodonico, 1971), Dehaanius limbatus (see Kakati and Sankolli, 1975), and Epialtus brasiliensis (see Negreiros-Fransozo and Fransozo, 1991). Partial or incomplete descriptions are known for Menaethius monoceros (see Gohar and AlKholy, 1957), Puggetia quadridens (see Kurata, 1969; Iwata, 1970), P.incisa (see Kurata, 1969), P.gracilis (see Forss and Coffin, 1960), and Huenia proteus (see Aikawa, 1937; Kurata, 1969). The present study aimed to describe the complete larval development (two zoeal stages and the megalopa) of the majid crab A.lunulatus, and to compare its larval features with other species of the Epialtinae. Method An ovigerous A.lunulatus, 14 mm carapace length, was collected near Tarragona (41°06.4 N, 1°17.1 E, western Mediterranean) from a depth of 0 m in June 1995 and was associated to the alga Pterocladia capillacea. © Oxford University Press

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Abstract The two zoeal stages and the megalopa of the majid crab Acanthonyx lunulatus are described and illustrated from laboratory-reared material The morphology of the larvae is compared to previous descriptions of larvae of other majid crabs of the subfamily Epialtinae.

G.Guerao and P.Abell6

Results Acanthonyx lunulatus (Risso, 1816) Cano, 1893:582, Plate 35, Figs 60-63 (zoea II); Bourdillon-Casanova, 1960:214, Fig. 73 (zoeae I—II); Heegaard, 1963:482^84, Figs 112-118, Plate 17, Fig. 21 (zoea I). Two zoeal stages plus the megalopa were observed in the larval development of A. lunulatus. A prezoeal stage was not observed and none of the specimens reached thefirstcrab stage. The main morphological characteristics of each larval stage are given below. First zoea

Size: TT: 0.60-0.68 mm; CL: 0.57-0.62 mm. Duration: 4-6 days. Carapace (Figure 1A,B): dorsal spine curved, smaller than the diameter of the eye but longer than rostral spine and distally armed with minute granular protuberances; rostral spine short, much shorter than the antennule protopod; lateral spines absent; 1 pair of anterodorsal and posterodorsal setae; majid spine present with 7 posterolateral subterminal setae on ventral margin of carapace; eyes sessile. Antennule (Figure IE): uniramous; endopod absent; exopod unsegmented with 3 terminal aesthetascs and a seta. 1186

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The crab was placed in an aquarium (60 x 35 x 30 cm) containing filtered and well-aerated sea water at a salinity of 37 p.p.t. and maintained at 21 ± 1°C until larvae hatched. The zoeae were placed in individual compartments of 30 cm3 and checked daily for evidence of moulting. The larvae were fed fresh Anemia nauplii and were maintained under the same constant conditions of temperature and salinity. Exuviae and specimens of each developmental stage were preserved in 7% buffered formalin. An Olympus phase contrast microscope was used in the dissection and observation of the setal structures of the appendages. Measurements were taken with a Wild binocular microscope equipped with an ocular micrometer, and are based on measurements of five individuals within each stage. The following measurements were taken: distance between tips of dorsal and rostral spines (TT); carapace length (CL), from the base of the frontal spine to the posterior margin of the carapace. For the megalopa, carapace width (CW) was measured as the greatest distance across the carapace, and carapace length (CL) as the distance from the tip of the rostrum to the posterior margin of the carapace. All drawings were made with the aid of a camera lucida. The number of individuals of each stage examined to describe the morphology varied between four and five. The adult female from which the present larvae were obtained is deposited in the Biological Collections of Reference of the Institut de Ciencies del Mar (CSIC) in Barcelona (Registration Number: ICMD-341995).

Larval development of Acanthonyx lunulatus

B

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Fig. 1. Acanthonyx lunulatus,firststage. (A) Frontal view; (B) lateral view; (C) abdomen, dorsal view; (D) half of telson, enlarged; (E) antennule; (F) antenna; (G) antenna, tip of exopod. Scale of A-C, E and G = 0.2 mm; scale of D and F = 0.1 mm.

Antenna (Figure 1F,G): protopod (spinous process) distally spinulate and longer than rostral spine; endopod present; exopod almost equal in length to protopod, distally spinulate with two subterminal setae of unequal length. Mandible: incisor and molar processes well developed; mandibular palp absent. Maxillule (Figure 2A): coxal endite with 7 setae; basal endite with 7 setae, single seta absent on external margin; endopod 2-segmented, distal segmented with 4 terminal setae. Maxilla (Figure 2B): coxal endite bilobed with 5+3 setae; basal endite bilobed with 5+4; endopod not bilobed with 5 terminal setae; exopod (scaphognathite) margin with 11 setae and 1 distal stout process. 1187

G.Guerao and P.Abello

\

Fig. 1 Acanthonyxlunulatus, first stage. (A) Maxillule: (B) maxilla: (C) 1st maxilliped: (D) 2nd maxilliped. Scale = 0.1 mm.

First maxilliped (Figure 2C): basis with 10 setae arranged 2,2,33; endopod 5-segmented with 3,2,1,2,4+1 setae, respectively; exopod 2-segmented, distal segment with 4 terminal plumose natatory setae. Second maxilliped (Figure 2D): basis with 2 setae; endopod 3-segmented with 0,1,4 setae, respectively; exopod 2-segmented, distal segment with 4 terminal plumose natatory setae. Third maxilliped: present, rudimentary, bilobed. Pereiopods: present, rudimentary; chela bilobed. Abdomen (Figure 1B,C): 5 somites, somite 2 with 1 pair of lateral processes directed anteriorly; posterolateral processes absent from somites; somite 1 with one pair of dorsomedial setae; somites 2-5 with 1 pair of posterodorsal setae; pleopods absent. 1188

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/

Larval development of Acanthonyx lunulatus

Telson (Figure 1 B,C,D): each telson fork with a minute lateral spine and distally spinulate; posterior margin with 3 pairs of long plumodenticulate setae, medial notch absent. Second zoea Size: TT: 0.95-0.99 mm; CL: 0.69-0.75 mm. Duration: 5-9 days. Carapace (Figure 3A,B): carapace unchanged except dorsal spine now without distal protuberances; 3 pairs of anterodorsal setae (the third one longer), one pair 1189

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Fig. 3. Acanthonyx lunulatus, second stage. (A) Frontal view; (B) lateral view; (C) abdomen, dorsal view; (D) half of telson, enlarged; (E) antennule; (F) antenna. Scale of A and B = 0.5 mm; scale of D-F = 0.1 mm.

G.Cuerao and P.Abello

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Fig. 4. Acanthonyx lunulatus, second stage. (A) Maxillule; (B) maxilla; (C) 1st maxilliped; (D) 2nd maxilliped. Scale of A and B = 0.1 mm; scale of C and D = 0.2 mm.

near the base of the dorsal spine, and one pair placed posterodorsally; majid spine now with 9 posterolateral subterminal setae on ventral margin of carapace; eyes stalked. Antennule (Figure 3E): unchanged except endopod now present; exopod now with 6 aesthetascs and 2 setae. Antenna (Figure 3F): unchanged except endopod now almost half the length of the protopod. Mandible: unchanged except mandibular palp now present. Maxillule (Figure 4A): coxal endite now with 8 setae; basial endite now with 10 setae, single plumose seta present on external margin; endopod unchanged. 1190

Larval development of Acanthonyx lunulalus

Megalopa Dimensions: CL 1.18-1.26 mm; CW 0.82-0.96 mm. Carapace (Figure 5A,B): longer than broad, narrowing anteriorly and without spines; rostrum acute, well developed and straight; front with acute corners each one bearing a seta in its tip. Antennule (Figure 5D): peduncle 3-segmented with 2,1,1 setae; endopod 2-segmented with 0,1+2 setae; exopod 4-segmented with 0,8,4,0 aesthetascs and 0,1,0,1 setae, respectively. Antenna (Figure 5E): protopod 3-segmented with 0,2,2 setae; segment 1 with a dorsal protuberance;flagellum4-segmented, with 0,0,4,4 setae. Mandible (Figure 5F): mandibular palp 3-segmented with 0,0,4 setae. Maxillule (Figure 6A): coxal endite with 8 setae; basal endite with 17 setae; endopod unsegmented without setae. Maxilla (Figure 6B): coxal endite slightly bilobed with 6+3 setae; basal endite with 6+6 setae; endopod unsegmented with one seta; exopod (scaphognathite) with 36 setae and 2 medial setae. First maxilliped (Figure 6C): coxal endite with 4 setae; basal endite with 9 marginal setae; epipod with 8 long setae; endopod unsegmented; exopod 2-segmented, proximal segment with one plumose terminal seta, distal segment with 4 long plumose terminal setae. Second maxilliped (Figure 6D): endopod 4-segmented with 0,1,3,6 setae; exopod 2-segmented, distal segment with 4 terminal plumose setae. Third maxilliped (Figure 6E): coxa with 7 setae; epipod with 3 long setae and 2 small setae; endopod 5-segmented with 9,8,5,5,4 setae; exopod 2-segmented, distal segment with 4 plumose setae. Pereiopods (Figure 7A-I): pereiopod 2 with spine on ischium; dactylus of pereiopods 2-5 distally spiculated with 4,4,5,5 small spines on their inner margin; pereiopods 1-5 setose as shown. Abdomen (Figure 5C): abdomen with 6 somites plus telson; posterolateral margins of segments 1-3 rounded; somite 1 with 1 pair of posterolateral setae; somites 1191

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Maxilla (Figure 4B): coxal endite bilobed with 5+3 setae; basial endite bilobed now with 5+5; endopod unchanged; exopod (scaphognathite) margin now with 22 setae and distal stout process now absent. First maxilliped (Figure 4C): unchanged except exopod distal segment now with 6 terminal plumose natatory setae. Second maxilliped (Figure 4D): unchanged except exopod distal segment now with 6 terminal plumose natatory setae. Third maxilliped: present, rudimentary, bilobed. Pereiopods: present, rudimentary; chela bilobed. Abdomen (Figure 3B,C): unchanged except now with 6 somites; somite 6 without setae; somite 1 now with 3 dorsomedial setae; somites 2-3 now with 1 pair of dorsomedial setae; pleopods now present with endopod buds. Telson (Figure 3 C, D): unchanged.

G.Guerao and P.Abello

2 and 3 with 1 pair of dorsal and 3 pairs of posterodorsal setae; somite 4 with 4 pairs of posterodorsal setae; somite 5 with 3 pairs of posterodorsal setae; somite 6 with 1 pair of posterodorsal setae. Pleopods (Figure 7J-M): present on segments 2-6; endopods with 2,3,2,2 coupling hooks; exopod of segments 1-4 with 12,12,12,10 long plumose natatory setae; uropods with 5 plumose setae. Telson (Figures 5C, 7N): slightly broader than long; posterior margin almost straight; dorsal surface with 2 median setae and 2 terminal spines. 1192

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Fig. 5. Acanthonyx lunulatus, megalopa. (A) Lateral view; (B) dorsal view; (C) abdomen, dorsal view, (D) antennule; (E) antenna; (F) mandible, endopod. Scale of A and B = 0.5 mm; scale of C = 0.2 mm; scale of D-F = 0.1 mm.

Larval development of A canlhonyx

lunulalus

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Fig.6. Acanthonyx lunulalus, megalopa. (A) Maxillule; (B) maxilla; (C) 1st maxilliped; (D) 2nd maxilliped; (E) 3rd maxilliped. Scale of A and B= 0.05 mm; C-E = 0.1 mm.

Discussion Zoeal stages of A. lunulatus were previously described by Cano (1893), BourdillonCasanova (1960), and Heegaard (1963). Cano (1893) described the second zoeal stage of Acanthonyx sp., attributed to A.lunulatus by Bourdillon-Casanova (1960) and Heegaard (1963). Bourdillon-Casanova described incompletely two zoeal stages taken from plankton samples which were attributed to A.lunulatus. Heegaard (1963) described the first stage from laboratory-hatched material. These descriptions are limited and there are some discrepancies between them. For example, Bourdillon-Casanova (1960) illustrated some small protuberances on the 1193

G.Guerao and P.Abello

Fig. 7. Acanthonyx lunulaius, megalopa. (A-C) Pereiopods 1-3; (D-E) dactylus of pereiopods 2-3; (F) pereiopod 4; (G) dactylus of pereiopod 4; (H) pereiopod 5; (I) dactylus of pereiopod 5; (J-M) pleopods 1-4; (N) telson andrighturopod. ventral view. Scale of A-C, F and H = 0.2 mm; scale of D-E, G and 1-N = 0.1 mm.

dorsal spine, while Heegaard (1963) showed it as smooth. The former author mentioned a small spine on the base of the telson fork whereas the latter did not mention its occurrence. Cano (1893) also showed the telson fork without a spine. Yang (1968), and Kakati and Sankolli (1975), who worked on other species of the subfamily Epialtinae, suggested that, since Bourdillon-Casanova's material was obtained from the plankton, her identification must be suspect, especially since other features of her larvae did not correspond to those described by Heegaard. However, the present laboratory-reared material clearly confirms the results of Bourdillon-Casanova (1960): the first zoeal stage of A.lunulatus possesses minute protuberances on the dorsal spine and a very small lateral spine on 1194

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J

Larval development of Acanlhonyx lunulatus Table I. Comparison of the characteristics of the first zoeae of Acanthonyx lunulatus. as given by the drawings of Heegaard (1963). with those obtained in the present study Present work

2.1

3.1

0,3 8 5

0.4 7 7

4 3+3 7 10

5 5+4 8 11

1,2,1,1.4

32.123

S = setae; A = aesthetascs: PI = plumose seta.

each telson fork. These spines are very small and rather difficult to see so they were probably missed by Heegaard and Cano. Hiyodo et al. (1994) also observed a small lateral spine on each telson fork of the zoeae of Acanthonyx petiverii which were also not recorded in the first description of this species by Lebour (1944). Moreover, there are many differences (Table I) between the present descriptions and the drawings of the appendages of the first zoea illustrated by Heegaard (1968). The zoeal stages of A. lunulatus are very similar to those of A.petiverii (Hiyodo et al, 1994). Differences between the larvae of the two species appear to be limited to the setation of the appendages (Table II), since no granular round protuberances on the dorsal spine are mentioned in the descriptions of the zoeal stages of A.petiverii. The species of the subfamily Epialtinae may be divided into three subgroups depending of the degree of development of the dorsal spine. Subgroup I includes species whose zoeae have a long dorsal spine on their carapace (longer than the eye diameter), such as Pugettia spp. and Taliepus dentatus. Subgroup II includes the species whose zoeae have a short dorsal spine (shorter than the eye diameter), such as Acanthonyx spp., Epialtus spp., Dehaanius limbatus and Huenia proteus. Subgroup III includes only one species, so far, which lacks a dorsal spine: Menaethius monoceros. Taliepus dentatus differs from all the other Epialtinae of subgroup I {Pugettia spp.), and also from those of subgroup II, in the presence of knobs in the third abdominal somite. The zoeae of the genus Acanthonyx differ from the other known Epialtinae of subgroup II in the setation of the maxillule endopod (Table II), the very small size of the outer telson spines, and in the absence of postero-lateral processes on the abdominal somites, although this last characteristic is also shared by Epialtus brasiliensis. They resemble those of Dehaanius limbatus in their possession of minute protuberances on the dorsal spine (Kakati and Sankolli, 1975), and differ in their lack of dorso-lateral processes in the abdominal somites, together with some 1195

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Antennule setation: A. S Maxillule setation: S on endopod S on basal endite S on coxal endite Maxilla setation: S on endopod S on basal endite S on coxal endite PI on scaphognathite Maxilliped 1 setation: S on endopod

Heegaard (1%3)

Reference Zoea I Carapace: Dorsal spine Antennulc setation: A.S

Maxillule setation: S on endopod S on basal endite S on coxal endite Maxilla setation: Son endopod S on basal endite Son coxal endite Sp on scaphognathite

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Table II. Morphological diferences in the zoeal stages of eight species of Epialtinae

p o s

3 o

Talieptis dentatus

Epialtus brasiliensis

Epialtus ditatatus

Acanthonyx petiveni

Acanthonyx lunulatus

Fagetti and Campodonico (1971)

Negreiros and Fransozo (1991)

Yang (1968)

HiyodoeJn/. (1994)

Present study

long

short

short

short

short

short

long

absent

4+2

3+1

2+1

3+1

3+1

2+1

ND

2?

1.5 7 7

0.6 7-8 4

6 (unseg.)

0.4 7 7

0.4 7 7

1.6 7 6

1.4

7 7

7(6)6(7)-

0.4 6 5

4 5+4 5+4 10

5 5+3 5 12

5 5+4 6 12

5 5+4 5+3 11

5 5+4 5+3 11

5 5+4 4+4 13

4 (2-3K 4+4 (4+5)" 4+4 (2+4)9(5)-

Dehaanms limbatus

Pugettia quadridcns

Menaethius nwnoceros

Kakati and Kurata(1969) Gohar and Sankolli(1975) (Iwata. 1979)* Al-Kholy(l957)

4 3+3 4+4

10-12

A.S

22,2,3

3,1,2,3?

2223

22.33

2,2.3,3

3

2(3)

2

3

2

present

absent

absent

absent

absent

7

7+1

6

6+2

6+2

0.6 9 5

5 (unseg.)

0,4 10 7

0,4 10 8

6

5 5+5

22 approx.

5 5+4 22

5 5+5 22

3.2,2.2 ?

2.2.23

2233

2.233

4

2 3.2+22.22.0

3 ND

2

Maxillule setation: 1.5 S on endopod 10 S on basal endite 8 S on coxal endite Maxilla setation: 4 S on endopod 5+5 S on basal endite Sp on scaphognathite 20 approx. Maxilliped 1 setation: 2,2,23 S on basis Maxilliped 2 setation: 3 S on basis 3,2+2.2+222,0 Abdomen setation

3(4)+3(4) 19(20)

ND

9 7

2,222

(2,2,2,3)-

ND

3

(3)-

3

absent

absent

present

6+2

ND

4?

1.6 10 7

1,4 9 9

0,4 8 3

5 5+5 22

4 5+5 24

5 3+4

2,2,22

ND

ND

ND ND

ND ND

3 3.2+2,2+2.2,2,0 ND

20-25

1

il development ol

S = setae; A = aesthetascs: Sp = plumose setae; ND = no data.

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Maxilliped 1 setation: S on basis Maxilliped 2 setation: S on basis Pleon: Knobs on somite 3 Zoeall Antennule setation:

I myx lanu

5*^

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b S

Table HI. Morphological diferences in the megalopa of seven species of Epialtinae. Abbreviations and remarks in Table II

Reference Megalopa Antenna setation: Maxillule setation: S on endopod S on basal endite S on coxal endite Maxilla setation: S on endopod S on basal endite S on coxal endite Maxilliped 1 setation: S on basal endite S on coxal endite S on exopod Maxilliped 2 setation: S on endopod S on exopod Maxilliped 3 setation: S on endopod Abdominal segments: Pleopod setation: S on exopod of PL 1 S on exopod of PL 2 S on exopod of PL 3 S on exopod of PL 4

i

Taliepus dentatus

Epialuis brasiliensis

Epialms dilatatus

Acanthonyx petiverii

Acanthonyx luniilatus

Dehaanius hmbatus

Meiiaelhms mnnnceros

Fagetti and Campodonico (1971)

Negreiros and Fransozo (1991)

Yang (1968)

Hiyodo et al. (1994)

Present study

Kakati and Sankolli(1975)

Gohar and AlKholy(1957)

1.2.3,0.0,4,3

0.23,0,0.4.3

1,2,3,0,03.4

0.1.1.0.03.4

0.2,2,0.0.4.4

0.1.1,0,0.4

ND

3

0 16 8

1+1 17 9

0 17 8

0 17 10

0

10

0 13 8

2 6+6 7+3

0 9 7

0 10 7

0 6+7 7+3

1 6+6 6+3

0 5+5 6+2

0 2+3 5+3

12 approx.

8 3 1+2

7 approx.

6 1+4

5 1+4

10 7 1+4

9 4 1+4

8 4 1+4

4

0,1,3,6

0,13.6

0.13.5

0,1,3.6

0,13.6

0.0.1.7

0.0.0.8

0.5

0,4

0,4

0.4

0.4

0.4

03

17aprox.

7 7

11-15 3 (unseg.)

12,7,5,5,4

6.1.43.6

13,633.5

7.633,4

9.833,4

7.2,5.5,4

i o — i •s • > • > • >

6

6

6

6

6

6

5

13 13 12 10

12

12 11 11 9

12 12 11 8

12 12 12 10

12 12 12 10

6 6 6 4?

12(11) 11(10) 9(8)

a B> C>

n E o.

Larval development of Acanlhonyx lunulatus

Acknowledgements We wish to thank M.Codina for the help provided and Dr P.F.Clark for his constructive suggestions to improve the manuscript. Partial support by CICYT research programmes MAR91-0860 and AMB95-0901-C02-01 is acknowledged. References Aikawa.H. (1937) Further notes on brachyuran larvae. Rec. Oceanogr. Works Japan, 9,87-162. Bourdillon-Casanova,L. (1960) Le meroplancton du Golf de Marseille: Les larves de Crustacea D£capodes. Rec. Trav. Stn Mar. Endoume, 30,1-286. Cano.D.G. (1893) Sviluppo e morfologia degli Oxyrhynchi. Mitt. Zool. StaL Neapel, 10,527-583. Chaix,E.L. (1979) Le cycle biologique et quelques aspects de la reproduction du crabe oxyrhynque Acanthonyx lunulatus (Risso, 1816) (Crustacea Decapoda Oxyrhyncha). Tethys, 9,17-22. Chaix J.C. (1984) Influence de l'ablation des pecloncules oculaires et de quelques facteurs externes sur les mues et reproduction de Acanthonyx lunulatus (Crustacea, Decapoda, Oxyrhyncha). Vie Mar., 6, 25-37. ChaixJ.C, TrillesJ.P and Vernet.G. (1976) Deg6n6rescence de l'organe y chez les males d'Acanthonyx lunulatus (Risso) (Crustacea, Decapoda, Oxyrhyncha). C.R. Acad. Set, Paris, 28, 253-255. Fagetti.E. and Campodonico.I. (1971) Desarrollo larval en el laboratorio de Taliepus dentatus (MilneEdwards) (Crustacea Brachyura: Majidae: Acanthonychinae). Rev. BioL Mar., 14,1-14. Forss.C.A. and Coffin.H.G. (1960) The use of the brine shrimp nauplii. Anemia salina, as a food for the laboratory culture of decapods. Walla Walla College Publ., 26.1-15.

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setation features (Table II). The zoeae of Epialtus resemble Acanlhonyx and Hueniaproteus, and differ from the rest of Epialtinae species in the absence of setae in the proximal segment of the maxillule endopod (segment absent in Epialtus dilatatus\ Table II). The second zoeae of Epialtus differ from the other Epialtinae species in the absence of the outer plumose seta on the maxillule. The megalopa of A.lunulatus shows some differences with those of A.petiverii and the other known megalopae of Epialtinae. The carapace of A.lunulatus narrows anteriorly in dorsal view; it is not sub-rectangular as in A.petiverii. The rostrum is acute and straight, not small and deflected. Other meristic and morphometric data of the different described megalopal stages of Epialtinae crabs are shown in Table III. The morphological variability of the megalopal antenna in the family Majidae, and in particular within the subfamily Epialtinae, enables the differentiation between several genera (Rice, 1988). In Acanthonyx, Taliepus, and Puggetia, the antennae are similar to those of the typical Pisinae (Rice, 1988), with the size of their terminal article being more than half the length of the anterior article. However, the terminal article in the genus Epialtus is greatly reduced, and in Dehaanius limbatus it is absent (Kakati and Sankolli, 1975). The relationships between Acanthonyx and Dehaanius, based on adult characters, are unclear (Tirmizi and Serene, 1971; Manning and Holthuis, 1981). Adults of Acanthonyx closely resemble Dehaanius, however, some features clearly separate Dehaanius larvae from those of Acanthonyx. Thus, the two complete larval developments described for species of Acanthonyx indicate that larvae of both species have a larger number of morphological characters in common than shared with Dehaanius limbatus. These features would support the validity of keeping Dehaanius as a distinct genus, as suggested by Kakati and Sankolli (1975).

G.Guerao and P.Abello

Received on October 30, 1995: accepted on February 9, 1996

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Gohar.H.A.F and Al-Kholy,A.A. (1957) The larvae of four decapod Crustacea (from the Red Sea). Publ. Mar. Biol. Stn, Al-Ghardaqua,9. 177'-202. Heegaard.P. (1963) Decapod larvae from the Gulf of Napoli hatched in captivity. Vidensk. Medd. fra Dansk naturh. Foren . 125. 450-493. Hiyodo.C.M.. Fransozo.A and Negreiros Fransozo.M.L. (1994) Larval development of the spider crab Acanthonyx petiverii H. Milne Edwards. 1834 (Decapoda. Majidae) in the laboratory. Crustaceana. 66,53-66. I wata.F. (1979) Studies on the development of the crab Pugettia quadridens (De Haan): 1. Hatching and zoeae. Publ. Seto Mar. Biol. Lab., 18, 189-197. Kakati.V.S. and Sankolli.K.N. (1975) On the metamorphosis of the spider crab. Dehaanius limbmits (A. Milne Edwards) in laboratory (Brachyura, Majidae)./ Karnatak Univ. Sci.. 20. 275-282. Kurata.H. (1969) Larvae of Decapoda Brachyura of Arasaki, Sagami Bay - IV. Majidae. Bull. Tokai Reg. Fish. Res. Lab., 57, 81-127. Laugier.N. and ChaixJ.C. (1984) La croissance des bourgeons de rdg£ne>ation chez Acanthonyx lunulanis (Risso) (Crustacea Decapoda Oxyrhyncha) en r£g£ne>ation unique et multiple. Vie Mar., 6.39-47. Laugier.N. and ChaixJ.C. (1985) Regeneration and post-autonomy molting cycle in the spider crab Acanthonyx lunulatus (Risso), Crustacea, Decapoda, Oxyrhyncha. Cah. Biol. Mar., 26. 379-392. Lebour.M.V. (1944) Larval crabs from Bermuda. Zoologica. 29. 113-128. Manning.R.B. and Holthuis.L.B. (1981) West African brachyuran crabs (Crustacea: Decapoda). Smithsonian Comrib. Zooi, 306. 1-379. Negreiros-Fransozo.M.L. and Fransozo.A. (1991) Larval stages of Epialius brastliensis Dana, 1852 (Decapoda, Brachyura, Majidae) reared in the laboratory, with notes on characters of the majid subfamilies. Crustaceana, 60, 200-212. Rice.A.L. (1988) The megalopa stage in majid crabs, with a review of spider crab relationships based on larval characters. Symp. Zool. Soc. Lond., 59. 27-46. Risso,A. (1816) Histoire naturelle des Crustacts des environs de Nice. Paris, 1-175 pp. Sanz^\. (1986) Biometria y crecimiento relativo de Acanthonyx lunulatus (Risso. 1816) (Crustacea: Decapoda: Majidae). Adas VlllJom. Asoc. Esp. Entom., 1.180-187. Sanz A- (1989) Ciclo biol6gico de Acanthonyx lunulatus (Risso, 1816) (Crustacea: Decapoda: Majidae) en las costas del levante ib£rico (Mediterr£neo occidental). Sci. Mar., 53, 857-861. Tirmizi.N.M. and Serene,R. (1971) The rediscovery of two species of crabs (Decapoda, Brachyura) with observations on three other species from Pakistan. Crustaceana. 21,21-32. Yang.W.T. (1968) The zoeae, megalopa andfirstcrab of Epialtus dilatatus (Brachyura. Majidae) reared in the laboratory. Crustaceana, suppl. 2, 181-202. Zariquiey-Alvarez,R. (1968) Crust^ceos decipodos iWricos. Invest. Pesq., 32, 1-510.