The complete larval development of Sadayoshia edwardsii (37) (Decapoda: Anomura: Galatheidae) described from laboratory‐reared material

The complete larval development of Sadayoshia edwardsii (Miers, 1884) is described and illustrated from laboratory‐reared material. The development comprises four zoeal and one megalopal stages. Diagnostic zoeal characters of Sadayoshia are provided and these are compared with other galatheid genera for which the larval morphology is known. Zoeas of S. edwardsii are readily distinguished from those of other galatheid species by the setation of the maxillular endopod together with the basis and endopod of the first maxilliped. The megalop of S. edwardsii has a flattened, triangular‐shaped rostrum, which differs remarkably from that of the adult. Although the rostral shape resembles that of Galathea megalops, the armature of the lateral margins is different between megalops of the two genera. The present larval study suggests that Sadayoshia is more closely allied to Galathea than to Munida.

Colour in life. Carapace, abdomen including telson and appendages essentially transparent; median gastric region and ventral side of abdominal segments bright orange; red or brightorange chromatophores present on lateral margin of carapace, eyes, mandibles, maxillule, maxilla, and basis and endopod of first and second maxillipeds.
Carapace ( Figures 1B, 2C, D). Posterodorsal and posteroventral margins with 8-12 and 26-29 teeth, respectively; three pairs of setae present on proximal part of rostrum and median part of carapace; basal part of rostrum swollen; eyes now stalked; otherwise unchanged.
Antennule ( Figure 3B). Protopod with two or three plumose setae present at distal onequarter, distally with four aesthetascs and three or four simple setae; endopodal bud slightly developed, with a terminal plumose seta.
Colour in life. Similar to first zoea, but antennule and third maxilliped with red or brightorange chromatophores.
Antennule ( Figure 3C). Protopod swollen proximally, with one short plumose seta, one lateral plumose seta present at mid-length of lateral margin, four plumose setae present at junction with exopod; endopod developed, but still fused to protopod, bearing one long plumose seta terminally; exopod articulated, with two lateral aesthetascs, terminally with three aesthetascs and three setae.
Third maxilliped ( Figure 9C). Endopod more developed than in previous stage, with one terminal seta; exopod with seven or eight (usually eight) natatory setae.
Abdomen (Figures 1C,10F). Six segments; segment 6 with one dorsal and one ventral posteromedian spine, and with pairs of posterolateral spines; appearance of biramous uropods, endopods naked, exopods well developed, with nine or 10 plumose setae marginally and two small setae at ventral surface.
Colour in life. Almost as in previous stage, but chromatophores on antennule sometimes absent.
Colour in life. Similar to third zoea.
Carapace ( Figures 1E, F, 2G, H, I, J). Longer than broad; dorsal surface with numerous setae, lateral margin with six or seven (usually seven) small spines, three sublateral spines on hepatic to epibranchial regions, pair of epigastric spines present; transverse striae indistinct. Rostrum triangular, broad proximally, with three lateral teeth, anterior tooth distinctly smaller than the posterior teeth. Pterygostomian flap differentiated from the carapace by faint demarcations, anterior margin armed with two spines. Thoracic sternites as illustrated; third thoracic sternite approximately three times as wide as long, anteromedian margin concave; following sternites expanded laterally, without distinct transverse striae or ridges, sparsely setose as illustrated.
Third maxilliped ( Figure 9E). Coxa and basis with 12 or 13 and four to six setae, respectively; endopod five-segmented, ischium with crista dentata of 12-17 small teeth and four to seven setae; merus with five to seven setae; carpus, propodus and dactylus with 20-24, 41-48, 29-36 setae (including stout serrate setae), respectively; exopod segmented, proximal segment with three or four setae marginally, distal segment with 10-12 terminal simple/plumose setae. Figure 9I, J, K). All pereiopods fully developed, segmented. Cheliped (first pereiopod) robust, approximately as long as carapace, sparsely setose and spinose as illustrated; carpus with one large acute spine on mesial margin. Ambulatory legs (second to fourth pereiopods) slender, sparsely setose as shown; merus with row of small teeth on extensor and flexor margins; carpus with one large, acute spine and few small spines on extensor margin; propodus with four to six movable spines on flexor margin, distal pair largest; dactylus with four to five movable spines and four to six teeth. Fifth pereiopod short, subcylindrical, chelate; palm with three to five long and some short serrate setae. No male/female gonopores.
Colour in life. Carapace and abdomen generally transparent, with scattered, orange or/and red chromatophores; telson with red chromatophores on posterolateral margin; appendages essentially transparent, red or bright-orange chromatophores present on eye stalk, antennal peduncle, second and third maxillipeds, chela of first pereiopod, dactyli and propodi of second to fourth pereiopods, and uropods.

Discussion
Sadayoshia edwardsii zoeas agree well with diagnostic features of the galatheids proposed by Gurney (1942) and Konishi and Saito (2000); in particular in that the carapace possesses a pair of posterolateral spines and posterodorsal and posteroventral teeth, and that the maxillar scaphognathite bears a long plumose process on the posterior margin.
As shown in Table I, Sadayashia zoeas are diagnosed by the following characters: (1) the anterolateral spine of the carapace is absent; (2) the maxillular endopod is unsegmented, with 1+1+4 setae; (3) the maxillar endopod bears 3+4 setae; (4) the first maxilliped bears two setae on the coxa and 12 (3+3+3+3) setae on the basis, respectively; (5) the endopod of the first maxilliped bears 3, 2, 1, 2, 4 setae each on ventral margins of the first to fifth segments; (6) the sixth abdominal segment armed with a posterodorsal spine in the third and fourth zoeas; (7) telsonal formulae in the first and second zoeas are I+ii+3-7, I+ii+3-8, respectively, and in the third and fourth zoeas respectively;and (8) lateral spines of the telson are much shorter than the posterior plumose processes through the zoeal stages. Among these characteristics, the setation of the maxillular endopod is an uncommon character and known only in Cervimunida johni Porter 1903 (see Table I. Morphological differences in zoeal stages among seven galatheid genera, for which larval morpology has been described.

Agononida
(1) Posterior processes Fagetti 1960). However, Sadayoshia zoeas differ considerably from C. johni by the setation of the basis and endopod of the first maxilliped (see Table I). Therefore, Sadayoshia zoeas can be distinguished from the other genera through the zoeal stages by the combination of setation of the maxillular endopod and of the first maxillipedal basis and endopod. With regard to the adult systematics, Baba and de Saint Laurent (1996) and Baba and Wicksten (1997) suggested that the Galatheidae could be separated into two groups by the presence or absence of first pleopods in males. The genera having the pleopods are as follows: Alainius Baba, 1991, Allogalathea Baba, 1969, Allomunida Baba, 1988, Anomoeomunida Baba, 1993, Cervimunida, Fennerogalathea Baba, 1988, Galathea, Janetogalathea Baba and Wicksten, 1997, Leiogalathea Baba, 1969, Munida, Munidopsis, Pleuroncodes, Raymunida Macpherson and Machordom, 2000, Sadayoshia Baba, 1969and Shinkaia Baba and Williams, 1998. Among these genera, Sadayoshia is allied to Anomoeomunida, Cervimunida, Pleuroncodes and Munida by having a spiniform rostrum (Baba and Wicksten 1997). Although the Anomoeomunida zoea is still unknown, Sadayoshia also resembles Cervimunida, Pleuroncodes and Munida in the following zoeal characters (Table I): (1) the maxillular endopod is unsegmented through the zoeal stages and (2) the posterior margin of the telson bears more than 9+9 processes in the fourth zoea. Moreover, Sadayoshia has a dorsal-posteromedian spine on the sixth abdominal segment in the third and fourth zoeas, the character is also shared in Pleuroncodes and Munida. The abdominal armature is not known for Cervimunida, because the complete larval development remains undescribed.
Sadayoshia larvae have short lateral spines on the telson that are much shorter than the posterior plumose processes through the zoeal stages and this character has also been described for Galathea larvae (see Gore 1979;Christiansen and Anger 1990;Fujita et al. 2001Fujita et al. , 2003. Although the larvae of Munidopsis are also known to possess short lateral spines, the general larval morphology is remarkably different from those of the other genera due to the abbreviated larval life (Sars 1889;Samuelsen 1972;Wilkens et al. 1990). The larvae of Cervimunida, Pleuroncodes and Munida possess lateral spines extremely longer than the posterior processes of the telson, which bears numerous marginal spinules in the first and second zoeal stages, and become shortened in the subsequent larval stages (Huus 1934;Boyd 1960;Fagetti and Campodonico 1971;Pike and Williamson 1972;Roberts 1973). From the viewpoint of the shape of the lateral spines of the telson, Sadayoshia zoeas seem to be allied to Galathea rather than to Cervimunida, Pleuroncodes and Munida.
Although zoeas of six galatheid genera have been identified to date, knowledge of megalopal morphology is restricted only to Galathea and Munida (Sars 1889; Lebour 1930Lebour , 1931Huus 1934;Al-Kholy 1959;Pike and Williamson 1972;Roberts 1973;Gore 1979;Christiansen and Anger 1990;Fujita et al. 2001Fujita et al. , 2003. Sadayoshia edwardsii megalop has a flattened, triangular-shaped rostrum, which is clearly different from that of the adult ( Figure 2H). This shape of the rostrum resembles that of Galathea megalops rather than Munida, although the adult of S. edwardsii has a spiniform rostrum as in Munida. The Munida megalop has a long, spine-like rostrum (but subterminally with very small lateral teeth) and two proximal short spines (see Sars 1889; Lebour 1930;Pike and Williamson 1972;Roberts 1973). However, the S. edwardsii megalop is easily distinguished from Galathea megalops by the rostrum with three lateral small teeth (with four teeth in Galathea megalops). Baba (1969) stated that Sadayoshia was placed between Munida and Galathea when he established the genus Sadayoshia. The present larval evidence agrees well with his opinion, and suggests closer relationships between Sadayoshia and Galathea than between Sadayoshia and Munida. In order to discuss accurate relationships between Sadayoshia and its related galatheid genera, further descriptive studies of larval development are required.