<I>Petrochirus Diogenes</I>

THE GLAUCOTHOES OF PETROCHIRUS DIOGENES (L.) AND TWO SPECIES OF DARDANUS (DECAPODA: DIOGENIDAE)I ANTHONY J. PROVENZANO, JR. Institute of Marine Science, University of Miami ABSTRACT The post-zoeal stages of three hermit crabs, Dardanus scutellatus of the Pacific and two west Indian forms, D. insignis and Pe~rochirus diogenes, were identified and described in detail. Characters of specific and generic significance were discussed. Glaucothoes of P. diogenes and several species of Dardanus are similar in all features distinguishing them from described glaucothoes of other genera. Differences between the post-zoeal stages of P. diogenes and Dardanus ssp. are no greater than differences among species of Dardanus. A plot of size vs number of telson setae for four species suggests that morphologically similar glaucothoes may be differentiated by this or similar means. INTRODUCTION Although taken only rarely, among the most distinctive of the crusta- ceans occurring in the plankton are those forms usually designated only as "pagurld glaucothoes." Identification of these animals to the generic level has been possible only in very few instances until recent years. How- ever, study of larval and post-larval hermit crabs by several workers has permitted the recognition of familial characters and the identification of specimens to generic and sometimes specific levels in some localities. In a previous paper, distinguishing familial characters of pagurine post-larvae were noted, and a list of the known glaucothoes of the hermit crab family Diogenidae was given in the introduction to a detailed description of a Dardanus glaucothoe (Provenzano, 1963). A comparison of the post-zoeal stage of Dardanus venosus with other known glaucothoes indicates that the form of the telson and other morpho- logical features may be used to separate, at least at the generic level, all the known diogenid glaucothoes. Among the features apparently distinguishing Dardanus glaucothoes from those of other diogenids are very large size, elongate telson, and presence of tooth-like processes on the ventral margins of the dactyls of the ambulatory legs. Unfortunately, there have been no adequate descriptions and illustrations for the three other species of Dardanus glaucothoes known and thus detailed comparison of the post-zoeal stage of D. venosus with that of other species within the genus was not possible. lContribution No. 470 from the Marine Laboratory, Institute of Marine Science, University of Miami. This research was supported by National Science Foundation grants GI6298 and G20355. 1963] Provenzano: Glaucothoes of Diogenid Hermit Crabs 243 The genus Petrochirus contains only three recognized Recent species, one on each side of the Central American land barrier and one off West Africa. No larvae are known for the genus. The species are similar in many ways to Dardanus, despite the fact that Petrochirus is the only genus in the family with the right hand larger than the left. Dechance and Forest (1958) suggested that the glaucothoe is probably similar to that of Dardanus. A number of glaucothoes have been accumulated and studied and, on the basis of facts given below under the heading of each species, the identities of several have been established. The present paper provides descriptions and illustrations of the glaucothoes of three species of large diogenid hermit crabs. It is one of a series providing basic descriptive data to aid identification of planktonic forms and to facilitate eventual detailed comparison of the larvae and post-larvae of paQUrid crabs. Such informa- tion may be considered in evaluation of systematic relationships within the group. I wish to thank Charles E. King for the specimen of Dardanus scutellatus and for permission to use it in the present study. I am pleased to acknowl- edge the assistance of Walter A. Starck, II and William Davis in obtaining material for study. THE GLAUCOTHOEOF Dardanus scutellatus (H. MILNE-EDWARDS,1848) Material.-1 specimen taken in company with 8 Diogenes gardineri, 4 Calcinus latens, and 16 Dardanus scutellatus ranging in size from first crab to ovigerous females, from Charles E. King's quadrant F-2-N, 16m2, about 40 yards offshore on lagoon side of Chinimi Island, Eniwetok Atoll, at a depth of 22 feet. Substrate: coral lime sand and rubble. 10 July 1961. Size.-CL 2.2 mm; TL 6.8 mm. Description.- The carapace, as in diogenids generally, is less than half the total length of the animal measured from the tip of the projecting but blunt rostrum to the posterior margin of the telson. The anterior portion of the thoracic shield is nearly half again as long as the posterior portion and is only slightly longer than wide. The eyes are widest at the cornea, width being two-thirds the length. The antennae exceed the chelipeds which do not reach to the dactyli of the walking legs. In the present specimen, which is a late glaucothoe, the abdomen has a slight twist due to the asymmetry of the crab stage which is well formed within the exoskeleton of the post-larva. The Tail Fan (Fig. 1,a) The telson has a LjW ratio of about 1.5. It is broadest proximally and tapers smoothly to about half maximum width. On the posterior margin 244 Bulletin of Marine Science of the Gulf and Caribbean [13(2) of the telson there are 15 plumose setae and about three additional pairs of smaller setae distally on each of the lateral margins. There is a median row of at least eight pairs of short setae and there are additional setae dorsally on the telson. The telson of the first crab stage is visible through the exoskeleton. The left lobe of the bifurcated telson of the crab is larger than the right, and both lobes have a few setae on the posterior margin. The protopod of the glaucothoe uropod on each side has a prominent spine. The exopodite of the uropod has about 45 straight setae fringing its margins, with about six additional curved setae on the postero-Iateral side. There are about a dozen corneous granules on the postero-Iateral margin of the exopodite. The endopodite is smaller than the exopodite and is more pointed posteriorly. There are about 30 setae lining the margins of the endopodite and about five corneous granules on the postero-Iateral margins of each. The Pereiopods The chelipeds (Fig. 2,a,a') are subequal; the hand is about two and a half to three times longer than high. The dactyli each have clusters of setae and two blunt teeth. a b FIGURE 1. The tail fan of: a, Dardanus scutellatus; b, D. insignis; and c, Petro- chDrusdiogenes. 1963] Provenzano: Glaucothoes of Diogenid Hermit Crabs 245 The second pereiopod (Fig. 3,a) has the dactyl about half as long as the slender propodus. The dactyl has a horny terminus and two large distally curving processes on the ventral margin. There is a third, similar but much smaller process distally. There are several large setae on the ventral margin. These processes are of considerable significance since they are not found in the glaucothoes of at least three other diogenid genera for which -the post-larva is known. The third pereiopod (Fig. 3,d) is similar to the second but the ventral processes of the dactyl are more strongly curved toward the terminus. The fourth pereiopod (Fig. 4,a) is subchelate; there is a very long seta and several shorter ones on the dactyl. The propodus bears a double row of corneous granules which total about eight, and a number of setae. The fifth pereiopod (Fig. 4,d,d') is chelate; the immobile dactyl has about seven corneous granules. There are a number of large setae on the distal portion of this appendage, some of them curved. The propodus is about four times longer than broad. Other Appendages The antennule (Fig. 5,a) consists of a jointed peduncle upon which there is a four-segmented ventral, or inner, ramus and a nine-segmented(?) dorsal, or outer, flagellum which bears numerous aesthetes on segments two to five. The antenna (Fig. 5,d) consists of a 19-segmented flagellum upon the peduncle. The antennal scale is a simple, ovate lobe. The mandible (Fig. 6,a,tr) consists of a stalked cup with a three-segmented palp bearing about 13 short setae. The maxillule (Fig. 6,d,d') has an apparently unsegmented endopodite bearing a single terminal and a smaller proximal seta. The basal endite bears about 15 stout setae distally and at least 17 others. There are three fine marginal setae. The coxal endites of both maxillules of the single specimen were damaged during dissection. The maxilla (Fig. 6,g) has the scaphognathite with a posterior lobe bearing about 70 setae. The distal lobe of the basal endite has about 17 setae, the proximal lobe about 12. The distal lobe of the coxal endite bears about five setae, the proximal lobe about 17 in two rows. The first maxilliped (Fig. 7,a) has a short, unsegmented exopodite bearing about 11 plumose setae laterally and a simple unarmed endopodite. The basal endite has at least 24 setae along its distal margin, some of them stout and bearing setules. The second maxilliped (Fig. 7,d) bears upon the basipodite a two- segmented exopodite which has more than nine setae distally upon the terminal portion and two medial setae on the proximal portion. The four- 246 Bulletin of Marine Science of the Gulf and Caribbean [13(2) segmented endopodite bears about 10 setae on the terminal segment, a few setae on the proximal segments. The third maxilliped (Fig. 7,g) bears about 13 plumose setae on the exopodite. The terminal segment of the five-segmented endopodite bears about 21 setae, some of which are serrated; the penultimate segment bears about 15.

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