LANG and YOUNG: LARVAL DEVELOPMENT OF HYPOCONCHA SABULOSA 



DISCUSSION 



Hypoconcha Species Distinction 



Both H. arcuata and H. sabulosa have similar 

 ranges and habitats along the southeastern Unit- 

 ed States coast (Hay and Shore 1918; Williams 

 1965) and adult morphology is quite similar 

 (Rathbun 1937; Williams 1965). The source of lar- 

 vae for this study was a small (carapace 17 x 17 

 mm) female with characteristics dorsal carapace, 

 color, and marginal spines (Williams 1965). How- 

 ever, the ventral carapace ridges were weakly de- 

 veloped and the three characteristic tubercles 

 (Rathbun 1937) were not evident (one small tuber- 

 cle was present). This may be characteristic of 

 young specimens or it may indicate hybridization 

 of the two species. The distinction of species for 

 these two forms should perhaps be reinvestigated. 



Not surprisingly, the differences between the 

 larval morphology ofH. arcuata given by Kircher 

 (1970) and//, sabulosa are slight. The differences 

 we observed overlap the ranges of variation re- 

 ported for setation or represent fine points open to 

 interpretation. Based on present published infor- 

 mation, a reliable means to distinguish corres- 

 ponding zoeal stages between the two species is 

 absent. Hypochoncha sabulosa megalopae have 

 spines on the eyestalk and abdominal segments, 

 features not noted for//, arcuata. However, these 

 may be points of omission by Kircher (1970) and 

 represent only tentative differences. A detailed 

 direct comparison of larvae is needed to determine 

 if these species can be identified during ontogeny. 



Characteristics of Dromiidae Larvae 



Knowledge of dromiid larvae is limited to five 

 genera within the family Dromiidae (Table 3). The 

 larvae of//, sabulosa demonstrate most general 

 features of dromiid larval development; some fea- 

 tures, however, such as carapace armature are 

 surprisingly diverse. Larval development ranges 

 from six zoeal stages in Dromidia antillensis to 

 two zoeal stages in Conchoecetes artifiosus. Four of 

 ten documented species have abbreviated de- 

 velopment (Table 3). 



The dromiid zoeal carapace is elongated with a 

 large, anteriorly directed rostrum, transverse 

 grooves, and, in most cases, a textured surface of 

 fine ridges. The carapace may lack armature 

 {Hypoconcha, Conchoecetes), have posterolateral 



spines (Dromia), have supraorbital spines (Dro- 

 midia), or have a dorsal spine and lateral "wings" 

 (Petalomera). Carapace margins are either 

 smooth or denticulate. All zoeae are richly pig- 

 mented with a general orange-red color. 



The antennal morphology is unique to the 

 group. The endopodite has 3 or 4 plumose setae in 

 stage I larvae. The exopodite is a flat scale and 

 after stage I has setae on its outer margin. 



The mandibular palp generally does not develop 

 until the terminal zoeal stage while the maxilla 

 endopodite is well developed and often distinctly 

 segmented. The endopodites of the first and second 

 maxillipeds are five- and four-segmented respec- 

 tively. The third maxilliped is usually biramous 

 and rudimentary in stage I but well developed 

 with a basally situated endopodite by stage II. 



Table 3.- 



- Principal studies on the postembryonic development 

 in taxa of the family Dromiidae. 



' Desaibed as Dromia vulgaris, 

 ^Described as Dromia personatus 



The pereiopods may be uniramous (Conchoec- 

 etes, Petalomera) or biramous (Dromidia). Only 

 the first pereiopod is biramous in Dromidia and 

 Hypoconcha. Uropods are well developed in late 

 zoeae oi Dromia, Dromidia, and Hypoconcha but 

 are reduced in Conchoectes and Petalomera. 



Systematic Position of the Dromiidae 



The classification and phylogeny of the 

 Dromiidae and other decapod groups rests princi- 



861 



