There are eight species of Majidae Samouelle, 1819 from Korean waters: four species of Majinae [
Larval descriptions of Majidae are limited to eight species in the northwestern Pacific:
On 30 December 2011 an ovigerous crab of
Comparison of the first zoeal characteristics of Leptomithrax edwardsii described by Kurata (1969) with those obtained in the present study
and described from anterior to posterior. Setal armature is described from proximal to distal segments and in order of endopod to exopod. The long plumose natatory setae of the first and second maxillipeds were drawn truncated. A micrometer was used for measurements: Carapace length (CL) was measured from the anterior margin of the eye to the most posterior carapace margin. Rostral spine to dorsal spine length (RDL) was measured from tip of the rostrum to tip of the dorsal spine. The classification follows that of Ng et al. (2008). The zoeas and spent female were deposited at Silla University, Korea.
Zoeal development consists of two zoeal stages. The mean duration of the first zoeal stage at 15℃ was 16 days. The second zoeal stage survived for 17 days. The moult to megalopa was not entirely successful because the megalopa was unable to extricate themselves from the zoeal exoskeleton. The first zoeal stage is described and illustrated completely. Only the main differences from the first zoea are described for the second zoeal stage.
Size: CL, 1.11±0.02 mm; RDL, 1.56±0.03 mm.
Chromatophores (Fig. 1). Predominantly yellow pigments which occurring on carapace, antenna, mandibles, basis of maxillipeds, pleomeres 1-4, and fork of telson; brown and black pigments which occurring behind eye, posterodorsal and posterolateral regions of carapace, mandibles, basis of maxillipeds, posterolateral margins of pleomeres 1-4, fork of telson.
Carapace (Fig. 2A). Dorsal spine slightly shorter than 1/2 CL, slightly curved posteriorly; rostral spine straight, approximately 1/2 length of dorsal spine; lateral spine absent; pair of posterodorsal setae present; each ventral margin with 1 plumose anterior and 4 posterior setae; eyes sessile.
Antennule (Fig. 2B). Uniramous; endopod absent; exopod with 1 long, stout aesthetasc, 2 shorter, thinner aesthetascs, 1 long and 1 shorter setae, all terminal.
Antenna (Fig. 2C). Biramous; endopod bud present; protopod about twice length to rostral spine, spinulate distally; exopod with 2 unequal subterminal setae, its tip shorter than protopod.
Mandibles (Fig. 2D). Asymmetrical; right molar and left molar processes each with tooth, confluent with incisor process; palp absent.
Maxillule (Fig. 2E). Coxal and basial endites both with 7 setae; endopod 2-segmented, proximal segment with 1 seta, distal segment with 6 (2 subterminal, 4 terminal) setae; exopod seta and epipod absent.
Maxilla (Fig. 2F). Coxal endite bilobed, with 3 + 4 setae; basial endite bilobed, with 5 + 4 setae; endopod bilobed, with 3 + 2 setae; exopod (scaphognathite) margin with 10 plumose setae plus 1 distal stout process.
First maxilliped (Fig. 2G). Coxa without seta; basis with 9 setae arranged 2 + 2 + 2 + 3; endopod 5-segmented with 3, 2, 1, 2, 5 (1 subterminal, 4 terminal) setae; exopod 2-segmented, distal segment with 4 terminal plumose natatory setae.
Second maxilliped (Fig. 2H). Coxa without seta; basis with 3 setae arranged 1 + 1 + 1; endopod 2-segmented, with 0, 7 (1 proximal, 3 subterminal, 3 terminal) setae; exopod 2-segmented, distal segment with 4 terminal plumose natatory setae.
Third maxilliped (Fig. 2I). Biramous.
Pereiopods (Fig. 2J). Present as buds.
Pleon (Fig. 2K). With 5 pleomeres; pleomere 1 with 2 dorsomedial setae; pleomere 2 with a pair of lateral processes directed anteriorly; pleomeres 2-5 each with a pair of pos-
terodorsal setae, pleomeres 3-5 with long posterolateral processes, progressing reduced in size; pleopod present as buds without endopods.
Telson (Fig. 2K, L). Each fork long, covered with setules, with 1 stout, 2 shorter spines laterally; each posterior margin with 3 serrated setae.
Size: CL, 1.43±0.05 mm; RDL, 1.68±0.05 mm.
Carapace (Fig. 3A). Each ventral margin with 1 plumose anterior and 7 posterior setae; eyes stalked.
Antennule (Fig. 3B). Biramous, endopod present, exopod with 1 subterminal and 5 terminal aesthetascs, 2 terminal short setae.
Antenna (Fig. 3C). Endopod bud approximately 1/2 length of protopod.
Mandibles (Fig. 3D). Right molar process with 2 teeth, confluent with incisor process; palp present.
Maxillule (Fig. 3E). Basial endite with 8 setae. Exopod plumose seta now present.
Maxilla (Fig. 3F). Basial endite with 5 + 5 setae; exopod (scaphognathite) margin with 16 marginal plumose setae.
First maxilliped (Fig. 3G). Coxa with 1 seta; exopod distal segment with 6 terminal natatory setae.
Second maxilliped (Fig. 3H). Exopod distal segment with 6 terminal natatory setae.
Third maxilliped (Fig. 3I). Endopod and exopod more developed.
Pereiopods (Fig. 3J). More developed, segments differentiated, chela bilobed.
Pleon (Fig. 3K). With 6 pleomeres; pleomere 1 with 3 dorsomedial setae; pleopod buds more developed, endopods present.
Telson (Fig. 3K). Unchanged.
Kurata (1969) described only the first zoeal stage; however, his description was too brief compared with that of the present study (Table 1). Moreover, he described the endopod of the maxillule as having 1, 7 setae, but it does not coincide with the other six known species of Majidae, which have 1, 2 + 4 setae. Also, he described the endopod of the second maxilliped as having 0, 1, 6 setae; however, we found 0, 7 setae as in
In the northwestern Pacific, larval informations of the family Majidae are available for eight species [three species (
Comparison of the first zoeal characteristics in eight species of Majidae from the northwestern Pacific
endopod of the maxillule with 1, 2 + 4 setae; the endopod of the first maxilliped with 3, 2, 1, 1, 5 setae; the basis of the second maxilliped with 1, 1, 1 setae; and the telson fork with lateral spines. However, the zoeas of Majinae are different from those of Mithracinae by having a dorsal carapace spine, no lateral carapace spines (except in
As shown in Table 2, the first zoea of
The following provisional key is provided for identifying the eight majid zoeas
1. Dorsal carapace spine present ?????????????????????????????????????2
- Dorsal carapace spine absent ??????????????????????????????????????3
2. Tip of exopod longer than that of protopod in antenna???????????????????????????????????????????????????????????????????
- Tip of exopod shorter than that of protopod in antenna????????????????????????????????????????????????????????????????????????
3. Lateral carapace spine present ??????????
- Lateral carapace spine absent??????????????????????????????????????4
4. Lateral processes on abdominal somites 2, 3????????????????????????????????????????????????????????????????????????????????
- Lateral process on abdominal somite 2 ????????????????????????5
5. Rostral carapace spine reduced or extremely short ???????????????????????????????????????????????????????????????????
- Rostral carapace spine approximately 1/2 length of dorsal carapace spine ???????????????????????????????????????????????????????????6
6. Endopod of second maxilliped with 0, 1, 6 setae ??????????????????????????????????????????????????????????????????
- Endopod of second maxilliped with 0, 7 setae??????????????7
7. Fork of telson with 1 large lateral spine ??????????????????????????????????????????????????????????????????????
- Fork of telson with 1 large and 2 smaller lateral spines??????????????????????????????????????????????????????????????????????