Larval development of Clastotoechus nodosus ( Streets , 1872 ) ( Crustacea : Decapoda : Porcellanidae ) , under laboratory conditions *

The genus Clastotoechus was erected by Haig (1960) to receive those Petrolisthes species with lateral walls of carapace consisting of several pieces separated from each other by a membrane. It is endemic to the Americas and comprises six species: C. nodosus (Streets, 1872), C. vanderhorsti (Schmitt, 1924), C. diffractus Haig, 1957, C. gorgonensis Werding and Haig, 1983, C. hickmani Harvey, 1999, and C. lasios Harvey, 1999. The two former species are restricted to the Western tropical Atlantic Ocean (see Haig, 1956; Gore and Abele, 1976; Werding, 1977, 1983; Scelzo, 1982; Harvey, 1999). SCI. MAR., 67 (4): 419-428 SCIENTIA MARINA 2003

Based on (a) the type of coverage of the carapace, chelipeds, walking legs and antennae, (b) the proximity degree of the teeth on the anterior margin of the carpus of chelipeds, (c) the presence and/or distribution of setae on propodus of chelipeds, and (d) the number of medial spines on propodus of walking legs, Harvey (1999) placed one of those species (i.e. C. vanderhorsti) in the junior genus Madarateuchus.The genus Clastotoechus has been recognised now and then, but the erection of the genus Madarateuchus has not been fully recognised yet, and has been only sparingly used.
The larval characters have been used for studying crustacean systematics and phylogeny (Martin and Davis, 2001).Thus, the detailed morphology of the zoeae and megalopa of C. nodosus provided herein is compared to those of C. vanderhorsti, which is the other congeneric species with available larval development (see Schoppe, 1994), assuming such comparison as a suitable starting point for the testing the adult-based relationships between Clastotoechus and Madarateuchus.

MATERIAL AND METHODS
Larvae from hatchings of four females of C. nodosus, collected by hand in balanid conglomerates from Charagato Bay, Cubagua Island, Venezuela (10°51´N, 64°9´W) were incubated individually in 150 ml glass containers with filtered and UV-sterilised sea water at 25ºC and 37‰ salinity; 60 to 80 larvae hatched in each batch.Larvae were fed daily with newly hatched Artemia nauplii.Water in the containers was changed daily.Survival and molting were recorded daily.
Samples of both dead and living zoeae and megalopa were preserved in a 1:1 mixture of glycerin and 70% isopropyl alcohol, and are currently deposited in the collection of the Laboratory of Crustaceans at the Universidad de Oriente.Drawings were made with the aid of an Olympus U-IT120 camera lucida using an Olympus BMAX-50 microscope.Measurements were made with a calibrated ocular.At least three specimens of each zoeal stage and megalopa from two or more females were measured, dissected, and analysed.The carapaces of zoeal stages and megalopa were measured in the standard way for Porcellanidae (Gore, 1968;Hernández et al., 1998).These measurements are expressed as the arithmetic average of the number of measured specimens and their standard deviation.The following abbrevia-tions are used: CL= carapace length; CW= carapace width; RL= rostral length; LPS= length of posterior spines of the carapace.The distribution of the chromatophores and coloration was determined on live specimens.The term seta is used as defined by Thomas (1960) and Gonor and Gonor (1973); the nomenclature for the different types of setae is based on the proposal by Stuck and Truesdale (1988) and has been used in previous publications by Hernández et al. (1998Hernández et al. ( , 2000Hernández et al. ( , 2002)).

RESULTS
Clastotoechus nodosus hatches as a prezoea of less than 60 minutes´ duration, and then passes through two subsequent zoeal stages which last 5-7 and 9-13 days respectively before the megalopa is reached.The duration of the megalopa was not recorded.
Telson (Fig. 6D) -Slightly wider than long.Anal spine present.Three pairs of setae dorsally.Seven pairs of processes on posterior margin: first pair represented by 1 spinulose spine (Fig. 6E), second a small setulose seta, third to seventh long setuloserrate setae (Figs.6F-J); fifth pair of long setae on central prominence; microtrichia on central prominence.
Color -Rostrum with three orange bands transversely.Posterolateral spines with one orange band distally.Red chromatophores on carapace dorsolaterally.Rest of body translucid.
Pereiopods (Fig. 5B) -Increasing in size and assuming segmentation as stage progresses.
LARVAL DEVELOPMENT OF CLASTOTOECHUS NODOSUS 423 Color -Same as in zoea I, but with additional red chromatophores on pereiopods and abdomen.
Colour -Not recorded.

DISCUSSION
Clastotoechus nodosus and C. vanderhorsti have been reported from the Caribbean, frequently sharing several local areas (Scelzo, 1982;Werding, 1977;Harvey, 1999).Although the former species prefers rocky intertidal shores (especially on balanid conglomerates) and the latter lives as a commensal on echinoids of the genus Echinometra, the zoeae and/or megalopae of both species could occur eventually in samples of plankton or benthos respectively from many Caribbean areas.
Zoeal stages of C. nodosus can be easily differentiated from those of C. vanderhorsti by some setal or spinal formulas of carapaces, several appendages, and telson (Table 1).The presence/absence of (a) spinules on the telsonal lateral spine (both zoeal stages), (b) the spinelike projection on coxopodite of maxilliped 1 (zoea I), and (c) the postorbital spine (zoea II), seem to support the disgregation of C.  Neither of these genera is unique in having such larval morphological features.The spinulation on the telsonal lateral spines has been reported for Porcellana sayana, P. sigsbeiana, and Ancylocheles gravelei (see Hernández et al., 1998); a similar spinelike projection on coxopodite of maxilliped 1 for both zoeal stages has been observed in several Petrolisthes species (i.e.P. tridentatus, P. tonsorius, P. violaceus, and P. magdalenensis); and a similar postorbital spine has not been hitherto reported for the American porcellanids, but it has been described for the larvae of the Indopacific species Petrocheles spinosus and P. australiensis (see Gurney, 1924;Wear, 1965).
FIG. 1. -Clastotoechus nodosus.Lateral view of zoea I (A) and zoea II (E); proximal (B), and medial (C) portions of rostrum of zoea I; details of postorbital spine of zoea II (F); proximal portion of posterior spines of zoea I (D) and zoea II (H); medial portion of rostrum of zoea II (G); dorsal view of megalopa (I) and details of its front (J).
nodosus and C. vanderhorsti into the two different genera Clastotoechus and Madarateuchus.Never-LARVAL DEVELOPMENT OF CLASTOTOECHUS NODOSUS 427

TABLE 1 .
Werding et al. (2001)ifferences in the zoeal stages of two Clastotoechus species., according toWerding et al. (2001), the C. nodosus/C.vanderhorsti clade is 100% supported on the basis of molecular characters.Both the knowledge of the larval morphology of the remaining Clastotoechus species and subsequent DNA sequencing analysis of all the species involved are essential to obtain a valid conclusion. theless