<I>Petrochirus Diogenes</I>

THE COMPLETE LARVAL DEVELOPMENT OF THE WEST INDIAN HERMIT CRAB PETROCHIRUS DIOGENES (L.) (DECAPODA, DIOGENIDAE) REARED IN THE LABORATOR yl

ANTHONY J. PROVENZANO, JR. Institute of Marine Sciences, University of Miami

ABSTRACT The complete zoeal development and the early post-larval development was followed in the laboratory. Description and illustrations of five zoeal stages and the glaucothoe are presented. There may be five or six zoeal stages in the larval development of P. diogenes, the number depending in part upon temperature. The zoeal stages and glaucothoe were compared in detail with those known of other species of diogenid and coenobitid hermit crabs and the systematic significance of a number of morphological features was evaluated. Ridges and grooves on the zoeal carapace of Petrochirus have not been reported for any other hermit larvae and may be unique to the genus, but other zoeal features considered to be "generic" in significance are shared with Dardanus. The glaucothoe described in a previous paper by this author and attributed to Petrochirus is shown to have been erroneously identified. Starved stage-I larvae were not able to survive to molt at any of five temperatures used, but survival was longer at 20° C than at lower or higher temperatures. At 10° C, and ] 5° C, larvae provided with Artemia nauplii as food were also unable to molt, and died in approximately the same time as starved siblings. At 20° C, 25° C, and 30° C, fed larvae were able to molt and to continue growth. Viable glaucothoes were not obtained at 20° C, but a few specimens reaching the terminal molt died in the process of becoming glaucothoes. At 25° C, glaucothoes were obtained after five and six zoeal stages. At 30° C, nearly all specimens reaching glaucothoe did so after only five zoeal stages. At all temperatures, the first zoeal stage had a longer mean duration than did the stages immediately following, but duration increased again in the last zoeal stages and reached a maximum in the glaucothoe, becoming less again at the crab stages. Explanations for these differences are offered. Total duration of the zoeal phase of development was approximately 50 days at 20° C and approximately 25 days at the higher temperatures used. Since the glaucothoe also is planktonic for much of its existence, the total potential planktonic life of this species may vary from 31-43 days at 30°, 37-50 days at 25°, and 72-84 days at 20" C.

INTRODUCTION The last decade has seen a sudden increase in laboratory studies on the larval development of decapod crustaceans, and more information

1 Contribution No. 867 from the Institute of Marine Sciences, University of Miami. This work was supported by grant No. GB-4305 from the National Science Foundation and grant No. GM-1I244 from the Institute of General Medical Sciences, U. S. Department of Health, Education and Welfare. 144 Bulletin of Marine Science [18(1) concerning the development of hermit crabs has been gathered during this period than in all the years preceding. The tropical western Atlantic contains a relatively rich pagurid fauna, the two major families, Diogenidae and Paguridae, being represented by well over 100 species, at least 10 per cent of which are still undescribed (Provenzano, unpublished data). Until 1962, no larval histories were known for any of the tropical western Atlantic hermit crabs and very few in other parts of the world had been studied. The tropical hermit crab family Diogenidae is represented in the western Atlantic by about 40 species. The only descriptions of known diogenid larvae and glaucothoes of this faunal region published as of the present writing are those for Calcinus tibicen (all stages, Provenzano, 1962a), Paguristes sericeus (all stages, Rice & Provenzano, 1965), and the glaucothoes of Dardanus venosus and D. insignis (Provenzano, 1963a, 1963b). Additional species of western Atlantic diogenids (Clibanarius, three species; Calcinus verrilli; Cancellus spongicola; Dardanus venosus and six species of Paguristes) have been reared at this laboratory but the results are not yet ready for publication. The genus Petrochirus is composed of only three Recent species, P. pustulatus (H. Milne-Edwards, 1848), which occurs off West Africa, P. californiensis Bouvier, 1895, from the tropical eastern Pacific faunal region, and P. diogenes (L.) of the western Atlantic. The West African species is much less similar to the American forms than the latter are to each other. Toula (1911) described a fossil pagurid which he referred to the Recent West Indian species of Petrochirus, but Rathbun (1918), noting that it appeared to have the right chela of P. californiensis and the left chela of P. bahamensis (= P. diogenes), considered Toula's form as a distinct species, possibly ancestral to the Recent American forms. No larval forms of this genus have been described previously, although Provenzano (1963b) attributed specimens of a large glaucothoe to Pet- rochirus diogenes, erroneously, as is now evident (see discussion which follows). Petrochirus diogenes (L.), the correct name of which was established by Holthuis (1959: 151-152) is known from Cape Hatteras, North Car- olina (Williams, 1965) south through the West Indies (including even the northern Gulf of Mexico [Hulings, 1961; Pounds, 1961]) to southern Brazil (Alves Coelho, 1964). Its large size and frequent occurrence in Queen Conch shells (Strombus gigas) make it a conspicuous element of the shallow-water fauna of this region. The purpose of the present paper is to present an account of the complete lOeal development and the glaucothoe of Petrochirus diogenes as discovered from laboratory rearings, to summarize the morphological features of the 1968] Provenzano: Larval Development of Petrochirus 145 zoeae and glaucothoes of the Diogenidae as presently known, and to make available some limited ecological data derived from the rearing experiments.

ACKNOWLEDGMENTS The female hermit crab which yielded the larvae described herein was coUected by the RjV HERNANCORTEZ,research vessel of the Florida State Board of Conservation, Division of Salt Water Fisheries. I am indebted to the staff of the State Board of Conservation Marine Laboratory at St. Petersburg, especially to Mr. William G. Lyons, and to the crew of the HERNANCORTEZfor their efforts to obtain this specimen for me and for keeping it alive after capture until it could be transferred to Miami. The success of the rearing experiments was largely due to the special efforts of C. Edith Marks who took care of the larvae daily from the time of hatching through metamorphosis, assisted at times by Mr. Talbot Mur- ray and Mr. Koesoebiono. I am especially grateful to Miss Barbara Stolen who did the necessary dissections and made all the illustrations. The financial support for the work came from research grant No. GB-1405 from the National Science Foundation and from grant No. GM-11244 from the National Institutes of Health, U. S. Department of Health, Education and Welfare. METHODS On 2 August, 1966 an ovigerous Petrochirus diogenes (shield length 14 mm, total carapace length 31 mm) was taken in a trawl by the RjV HERNANCORTEZat "hourglass station D" off the west coast of Florida (27°37'N, 83°58'W) at about 55 meters depth (180 feet). The bottom temperature at the station was 210 C. Two days later she was ashore at St. Petersburg in aerated sea water, and after being transported to Miami on 5 August she was placed in running sea water which fluctuated between 29-300 C from that date until hatching, which occurred on 14 August. Eggs examined on 6 August were very early in development with no differentiation of the embryo apparent under 60 X magnification, indicating that the eggs probably were laid not earlier than one or two days immediately preceding capture of the female. At the time of hatching, the sea water in the aquarium was at 29° C, and approximately 500 larvae were collected and placed into water of similar temperature. After isolation of the larvae into compartmented trays (as described in prior publications of this author and others) the trays were then placed at various temperatures. Some larvae were kept in mass culture at room temperature. Some isolated larvae were starved to deter- mine survival time at various temperatures, but most others were fed with Artemia nauplii daily or every second day, depending on temperature. All larvae except those at "room temperature" were kept in non-illu- 146 Bulletin of Marine Science [18(1 ) minated, controlled-temperature cabinets (BOD boxes or converted refrig- erators). Hence the larvae were reared essentially in the dark with exposure to normal lighting daily for one to two hours only. Larvae reared at room temperature were subjected to diurnal light variation, but were not permitted to receive direct sunlight. The lowest and most stable temperature used was 10° C, variations being less than plus or minus 0.2° C during the short duration of the experiment. Other larvae were maintained at approximately 5° C intervals which for convenience are hereafter termed 15° C, 20°, 25" and 30° C. In fact the variation at each of these temperatures above 10° C was considerable as revealed by recording thermometers. Thus the "15° C" actually varied between 13.5-14.5° C during the relatively short duration of that experiment. The "20° C" box varied from 19.5-21.5° C, during the time larvae were kept therein. The "25° C" or room temperature varied most of all, ranging from 27-26° during the first two weeks, dropping to about 25° during the third week. Because of factors not relevant to the experiment, room temperature dropped to about 20-21 ° during the fourth week, then returned to about 25° after the fourth week. The highest temperature, which was intended to be about 30° C, was actually about 30.5° the first week, one degree higher the second week, and then dropped to approximately 28-29° C during the next two weeks. The salinity for all experiments remained at 35.8%c, as stored, filtered water was used. At each experimental temperature, 36 larvae were isolated and starved. An additional 36 larvae were isolated but fed with newly hatched Artemia nauplii every day or every second day, at which time they were changed to clean trays. Larvae and exuviae were preserved in several fluids, but the best results and least distortion were obtained using ethylene glycol (100 per cent) as suggested by Williamson (1965). Ethyl alcohol (70 per cent) was about as good, but destroyed color more rapidly and turned the flesh of larvae opaque, making examination of details more difficult. Moreover, ethyl alcohol evaporates very readily, whereas ethylene glycol will remain even in loosely capped vials for indefinite periods, making it especially suitable for long-term storage of specimens. Measurements and drawings of whole animals were made with the aid of a Wild M-5 stereoscopic microscope equipped with camera lucida. For measurements of live specimens, the larvae were narcotized with a drop of propylene phenoxytol in a shallow watch glass. Measurements of carapace length (CL) gave similar results for preserved and living larvae, but measurements of total length (TL) were found to be approximately 0.3-0.4 mm less in preserved larvae of the younger stages than for living specimens, and in the larger stages the difference was even greater. The term "stage" is used herein in the sense of intermolt. Most appendages 1968] Provenzano: Larval Development of Petrochirus 147 were drawn with the Wild M-5 and camera lucida, but checking of details and illustrations of the smaller appendages were done with a binocular compound microscope (Wild M-20) equipped with drawing tube. Ap- pendages were drawn while unstained and while in wet mounts of ethylene glycol, but mandibles were mounted in glycerine jelly before illustration and all permanent slides were made using glycerine jelly as the mounting medium. Some specimens were stained with chlorozol black to reveal details not otherwise apparent. The female from which the larvae were hatched is deposited in the Marine Museum of the Institute of Marine Sciences, University of Miami under accession No. UMML 32.3123. The classification of hermit crabs used herein is that proposed by MacDonald, Pike & Williamson (1957: 256) and adopted by Provenzano (1959) and later workers. Superfamily Coenobitidea Pylochelidae Diogenidae Coenobitidae Lomisidae Superfamily Paguroidea Paguridae Lithodidae

MORPHOLOGY There may be five or six zoeal stages before the glaucothoe in the development of Petrochirus diogenes. General Characteristics of the Zoea.-The zoeal carapace is notable in having transverse and longitudinal ridges as illustrated (Figs. I & 2). The rather long rostrum exceeds the cephalic appendages and has a dorsal crest which extends back to the middle portion of the carapace, where it stops rather abruptly in a flattened area. There are no major deviations from the typical pattern of diogenid zoeal development. The eyes are fused to the carapace in the first stage, becoming free in the second. The rudimentary third maxilliped buds of the first stage become setose in the second, and there is another pair of telson spines added medially. The uropods become free and the telson is articulated for the first time in the third stage, but the endo-uropods do not become setose until the fourth stage. In the third stage, the fourth telson process becomes fused to the tclson and is much thickened, this condition persisting through the subsequent zoeal stages. The color pattern of the zoea is relatively simple. There is a pair of red chromatophores ventrolaterally on the fifth abdominal somite which 148 Bulletin ot Marine Science 118(1)

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FIGURE 1. Petrochirus diogenes. Dorsal view of zoeal stages I-V. Scale IS 0.5 mm. persists throughout the zoeal stages. There is in addition a group of orange and/or reddish chromatophores seen ventrally in the region of the labrum and mandibles and between the bases of the maxillae and maxillipeds. Other color, apparently not due to the usual chromatophores, is seen 1968] Provenzano: Larval Development of Petrochirus 149

FIGURE 2. Petrochirus diogenes. Lateral view, zoeal stages I-V. Scale IS 0.5 mm. posterolaterally on the telson in the second stage as two areas of diffuse yellow. It becomes apparent in the third stage that this color is restricted to the exo-uropods which in the second stage were still developing within the telson. These rather prominent spots remain through the fourth and fifth zoeal stages and, in addition, the tip of the rostrum in these stages has acquired a yellow tinge. 150 Bulletin of Marine Science [18(1)

FIGURE 3. Petrochirus diogenes. Telson and tail fan of zoeal stages I-V. Scale is 0.5 mm.

The detailed external morphology of the larval stages is shown in the accompanying figures; a detailed description therefore will be omitted, but the following remarks will deal with variations noted and with features of particular significance in the comparative morphology of diogenid larvae. First Zoea.-SlzE: CL 1.38 mm (1 spec., live), TL 2.80 (1 spec., live); CL 1.43-1.53 mm (8 spec., all preserved), TL 2.47-2.70 (8 spec., all preserved) . DESCRIPTION: The most notable characteristic of the first zoea is the pattern of ridges on the carapace. There are no sharp anterolateral spines 1968] Provenzano: Larval Development of Petrochirus 151

FIGURE 4. Petrochirus diogenes. Top row, antennule; middle row, antenna; bottom row, maxillule; of (left to right) zoeal stages I-V. Scale is 0.5 mm. 152 Bulletin of Marine Science [18(1)

on the carapace below the eyes as are formed in some other genera, and the posterolateral carapace corners are smoothly rounded. The abdomen lacks spines or bumps sometimes seen in other diogenids. The posterior margin of the telson (Fig. 3, I) is bilaterally convex with a moderately prominent median notch. The antennule (Fig. 4, I, top row) typically has a single plumose seta and five or six aesthetascs. The antenna (Fig. 4, I, middle row) has the normal armament on the endopod, but the scale, with nine or ten plumose setae, is rounded distally, not spined, and minute setules continue the armature onto the lateral margin distally. The maxillule (Fig. 4, I, bottom row) may have six or seven plumose setae on the coxal endite and the basal endite is armed with the normal two large spines and two smaller hairs. However, the endopodite is only two-segmented, 1968] Provenzano: Larval Development of Petrochirus 153 the distal segment bearing two terminal setae, the proximal segment bearing a single simple seta. The maxilla (Fig. 5, I) has a fringe of very fine setules around each endite. There is some variation in setation of the endites (three to five setae on the endopodite, the lobes of the basal endite bearing four or five setae each, the distal and proximal lobes of the coxal endite bearing four and six setae respectively). The first maxilliped (Fig. 6, I, top row) is notable in having a very prominent hook-like process on the proximal medial corner of the basipodite, the process bearing a single seta. As in other species, the medial margin of the endopodite in this stage has only fine setules. There was minor variation (from two or three in each cluster) in the number of setae on the medial margin of the basipodite, and on the proximal segment of the endopodite. The second maxilliped as illustrated (Fig. 6, I, bottom row) is very typical of diogenid larvae in general. The third maxilliped is a mere rudiment (Fig. 7, I). Second Zoea.-SIZE: CL 1.67-1.93 mm (6 live spec.), TL 3.20-3.60 mm (6 live spec.); CL 1.74-1.88 mm (11 preserved spec.), TL 2.84-3.22 (12 preserved spec.). DESCRIPTION: The second zoea differs in many respects from the first. The eyes are free, and the telson has added a pair of articulated processes medially, but there are also differences in all the appendages. The antennule may have up to eight aesthetascs; there are two small simple setae just proximal to the large plumose seta, but on the opposite side of the appendage. The antenna shows a reduction of one of the endopodal setae, and an increase in the number of marginal setae on the scale to about 14. The small lateral spine or tooth which appears on the base of the scale in other genera does not appear in this species. The maxillu\e may add one or two small setae on the coxal endite and two large teeth on the basal endite, but the endopodite remains the same. The maxilla has added four to five marginal setae on the scaphognathite and sometimes one on the proximal lobe of the coxal endite, but otherwise is similar to that of the preceding stage. The first and second maxilliped have added two natatory setae to the exopodite, and have replaced the fringe of fine hairs on the lateral margins of the endopodite with large setae as in other species. The third maxilliped is now functional, with six natatory setae on the exopodite and a lobe which will be the endopodite, bearing a single seta. Third Zoea.-SIzE: CL 2.15-2.38 mm (4 live spec.), TL 3.95-4.55 mm (4 live spec.); CL 2.17-2.40 mm (3 spec. dead), TL 3.93-4.20 mm. DESCRIPTION: The articulation of the telson with the sixth abdominal somite and the appearance of the uropods are the most important features of this stage. The outermost telson process has disappeared and the fourth process has now fused with the telson, but is not greatly enlarged. The telson bears one or two pairs of simple setae dorsally. The lateral margins 154 Bulletin of Marine Science 1968] Provenzano: Larval Development of Petrochirus 155

I II III IV V FIGURE 7. Petrochirus diogenes. Third maxilliped of zoeal stages I-V. Scale is 0.5 mm. of the telson are convex proximally, concave distally. Instead of 8 articulated setae between the two fused fourth processes of the telson, there may be 10, 11, or 12 setae. The exo-uropods bear 13-16 plumose setae marginally and three plumose setae ventrally. The antennule now has an articulated tip; the peduncle bears three plumose setae instead of one, three or four simple setae at the articulation, and a couple of small, simple setae proximally. There may be six or seven aesthetascs on the distal segment that will become the dorsal flagellum. The antennal endopodite has elongated and has changed its terminal armature to a single simple seta, as is usual in diogenids at this stage. The antennal scale now bears from 14-19 plumose setae marginally, some of them extending onto the lateral margin distally. The maxillule has up to 10 setae on the coxal endite, and there is sometimes an extra small spine on the basal endite. The endopodite is unchanged. The maxilla may have from 11 to 15 setae on the scaphognathite, and on the endopodite a minimum of three setae, most often four, rarely five. The distal lobe of the basal endite may have four to six setae, the proximal lobe normally has six. The distal lobe of the coxal endite had four setae in several specimens examined, and the proximal lobe had seven in a total of four specimens examined. The first maxilliped may have as few as six nata tory setae on the exopodite, but the usual number is eight, and there are eight on the second maxilliped. The third maxilliped may have six or seven.

~ FIGURE 6. Petrochirus diogenes. Top, first maxilliped; bottom, second maxilliped; of zoeal stages I-V. Scale is 0.5 mm. 156 Bulletin of Marine Science [18(1) ~------<

FIGURE 8. Petrochirus diogenes. The paired mandibles of zoeal stages I-V, in (left column) anterior aspect, and (right column) posterior aspect. Scale is 0.5 mm.

Fourth Zoea.-SIzE: CL 2.82-3.15 mm (6 live spec.), TL 5.0-5.55 (6 live spec.). DESCRIPTION: The telson is about as wide as in the preceding stage, but is considerably more elongate. The endo-uropods are setose for the first time, with 8-10 setae marginally, usually nine, and three setae sub- marginally on the dorsal surface. The setation of the exo-uropods varies from 15-19 marginal setae, and there are five submarginal setae ventrally. Otherwise the larva has not changed much in gross appearance, although 1968] Provenzano: Larval Development of Petrochirus 157 the appendages have developed further and have generally increased their setation. The antennule is now biramous. The peduncle has added a few small setae, and there are now four large plumose setae distally in addition to three or four small setae at the distal margin of the peduncle. The dorsal flagellum has seven terminal aesthetascs, of which five are usually large and two small. There are in addition a few groups of more proximal aesthetascs, each group consisting of two or three processes. The antennal endopodite remains essentially unchanged, but the antennal scale has added a couple of marginal setae, making 18-21 plumose setae. The maxillule is unchanged but for the addition of a seta or two on the coxal endite. The marginal setation of the scaphognathite on 13 maxillae was examined and found to range from 15-16. The setation of the endopodite and other endites has increased only by one seta usually, although the proximal lobe of the coxal endite might have 8-10 rather than seven as in the previous stage. The number of natatory setae on the exopodite of the first maxilliped is usually eight, but one specimen had 10. Other setation of this appendage is unchanged. The second maxilliped is likewise unchanged except for the nata tory setation which may be from eight to ten. The third maxilliped sometimes has a well-developed endopodal bud and the natatory setation may be seven to nine. Fifth Zoea.-All but one of the 42 animals which reached metamorphosis at 30° C went through only five zoeal stages, the other went through a sixth stage. Of the 31 at 25° C, which molted from stage V, 21 reached metamorphosis after five zoeal stages, and the others molted to a sixth zoeal stage. There is no significant difference between the metazoeae of the short series and longer series. A tendency for an additional natatory seta on the maxillipeds in sixth stage zoeae and a tendency towards slightly greater setation of the uropods were the only differences noted. Accord- ingly, the discussion of the ultimate zoea given below is that of terminal stage-V larvae which molted directly into glaucothoe. SIZE: CL 3.29-3.70 mm (6 live spec.), TL 5.88-6.45 mm (6 live spec.). (Note: Five specimens which molted from stage V to stage VI varied in carapace length from 2.88-3.13 mm. The size of subterminal stage- V individuals therefore is less than that of terminal stage- V larvae, and approximates the size of the fourth larva of a five-larva series. In five individuals of stage VI, the carapace length varied from 3. I2-3.69 mm, thus being within the range of size of terminal stage- V larvae.) DESCRIPTION: The gross features in which the ultimate zoea differs from the fourth stage are the presence of the pleopod buds on abdominal somites 2-5 and the presence of well-developed pereiopod buds. The tel son is now about two times longer than wide and is almost rectangular. The uropodal setation has increased somewhat, with 11-15 marginal setae 158 Bulletin of Marine Science [18(1) 1968] Provenzano: Larval Development of Petrochirus 159 on the endo-uropod, and usually three submarginal setae on the dorsal surface. The exo-uropod has 17-21 marginal plumose setae and four or five submarginal setae on the ventral surface. The dorsal surface of the telson has about six pairs of small simple setae along the dorsal surface. The antennule now has as many as seven groups or rows of subterminal aesthetascs, each group consisting of two to four processes, in addition to the terminal ones. The antennal endopodite is now longer than the scale and is segmented near the base. It terminates still in a single, very small, flexible seta. The marginal armature of the antennal acicle or scale is 20-23 plumose setae. The mandibles have for the first time a bud of the mandibular palp present, with or without a single small seta. The maxillule shows little variation. There are usually five strong teeth on the basal endite and one to three small, simple setae subterminally. The coxal endite may have from 10-13 setae. The first maxilIiped does not yet show evidence of the gross change which will occur at metamorphosis. The natatory setation may vary from 8-12, even in subterminal stage-V larvae. The second maxilIiped likewise shows little variation. The natatory setation is nearly always 10, and occasionally there will be one more or one less seta on one of the other parts of the appendage. The third maxilliped nearly always has 10 natatory setae, and the endopodal bud carries a terminal seta. Glaucothoe.-SIZE: CL 1.81-2.05 mm (8 spec.); TL 4.75-5.50 mm (3 spec., dead), 5.82 (1 spec., live). (Shield length [SL] varied from 0.98- 1.34 mm in 8 specimens. SL and CL did not differ much in animals measured dead and measured alive, but note that TL did show variation. In the three specimens for which TL was obtained, all had nearly identical SL and CL.) DESCRIPTION: The chromatophore pattern of the glaucothoe stage is similar to the zoeal pattern, i.e., there is a notable reddish area on the sixth abdominal somite and there are red chromatophores between the bases of the thoracic appendages ventrally. The glaucothoe is illustrated in Figures 9 and 10, and details of the appendages are shown in Figures 11 and 12. The various appendages have changed radically from the last zoeal stage. Like all diogenids, the glaucothoe of this species has a symmetrical, well-developed tail fan with well-developed endopodites. The number of large marginal setae on the telson varies from 11-13 (eight are usually seen in glaucothoes of the family Paguridae, whereas in the Diogenidae, the telson armature varies

FIGURE9. Petrochirus diogenes. The glaucothoe in dorsal view. Scale is 0.5 mm. 160 Bulletin of Marine Science [18(1) 1968] Provenzano: Larval Development of Petrochirus 161 from one species to another). But unlike other described diogenid glaucothoes, this stage in Petrochirus diogenes usually has the right hand larger than the left, as in the adult, a character which distinguishes this genus from all others in the Diogenidae. A few individual glaucothoes had subequal chelae. Of special significance, also, is the armature of the dactyls of the second and third pereiopods. On the third pereiopod, the four large teeth projecting towards the body are readily seen; while of the same type as in Dardanus, they are more numerous and their orienta- tion is different. The dissimilarity of the dactyl of the third pereiopod with that of the second is no less important a feature. Other significant features will be compared with corresponding ones of other species in the following section.

DISCUSSION-MoRPHOLOGY AND SYSTEMATIC CONSIDERATIONS Comparison of the Zoeal Stages with Those of Other Hermit Crabs.-The larvae of Paguridae are generally easily separable from larvae of the Diogenidae and Coenobitidae. Most important characters for distinguishing pagurid larvae are the presence of paired dorsal spines on the abdominal somites and the sharp angle of the posterolateral corner of the carapace. These characters are not absolutely reliable, however. The coenobitid crab, Birgus tatro, has a single pair of dorsal spines on the fifth abdominal somite (Reese, personal communication), although these are rather well developed, and not simply emarginations as are found on most pagurid zoeae. The only diogenid larvae so far known which have spines of any sort on the posterolateral carapace margins are those of Calcinus, but again the spines are very strong, corneous, and quite different in appearance from the simple, downturned, sharp corner typical of pagurid larvae. There are some species of pagurid larvae which lack posterolateral carapace armature entirely (Provenzano, unpub\.). In the third and fourth stages, the endo-uropod of pagurid larvae is a very reduced structure, bearing at most two setae in the last larval stage. (An exception is Parapagurus, a genus differing in many ways from others in the Paguridae.) The closest approximation in the coenobitidean hermits is in the larvae of Diogenes (MacDonald, Pike & Williamson, 1957). Otherwise, all diogenid and coenobitid larvae so far studied have, after the third stage, rather large, functional endo-uropods with numerous setae. In the following discussion, larvae of the Paguridae and Lithodidae are excluded from consideration, and wherever the term "hermit larvae" is used, it is intended to include only the larvae of Diogenidae and Coe- nobitidae. The Mediterranean Sea, in which there are only six species of diogenids distributed among five genera, is the only faunal region for which the knowledge of larvae of the Diogenidae is sufficiently complete to allow 162 Bulletin of Marine Science [18(1)

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/ k -~- -'------... 1968] Provenzano: Larval Development of Petrochirus 163 identification of planktonic forms. In contrast, the tropical western Atlantic or West Indian faunal region, in which Petrochirus diogenes occurs, contains at least 40 species of Diogenidae in eight genera (plus one species of Coenobita, the larva of which resembles those of the Diogenidae [Provenzano, 1962b]). In addition to representative larvae of most of the western Atlantic diogenid genera, larvae have been described for Diogenes and Trizopagurus, genera which occur only outside the western Atlantic. While it is not yet possible to construct keys for the identification of the larvae of the West lndian hermit crabs, a sufficiently large number of larvae have been described to permit at least a preliminary evaluation of some morphological features as aids to identification and as indicators of systematic relationships. Features important in distinguishing zoeal stages of various coenobitidean hermits are the general size, the carapacial armature and relative length of the rostrum, presence or absence of carinae, posterolateral or anterolateral spines or other sculpturing, the abdominal armature, the shape of the tel son and its armature, the scale of the antenna and the setation of the antennal endopodite, the character of the medio- proximal corner of the first maxilliped, the segmentation and setation of the endopodite of the maxillule, and the color pattern. Within single genera, larvae of known parentage have been described for more than one species only for Paguristes, Calcinus, and the terrestrial hermit genus Coenobita. The work by Dechance (1962) on Dardanus was based largely on planktonic material but the larvae are so similar that the generic identity is probably correct. Otherwise, there are only two species in each of the first three genera mentioned above, for which larvae have been described. This makes any statements regarding probable generic value of larval characters somewhat tentative. Fortunately, unpublished data of the writer has allowed consideration of at least some features of additional species of Dardanus, Clibanarius, and Paguristes. In the following discussion, if a given character is known to vary between larvae of the same genus, it is considen:d a specific character. If a given character is similar in two or more species within a genus as so far known, it is considered tentatively as a generic feature. The larvae of Petrochirus differ from all those described for other coenobitideans. There is no single feature other than the carapace grooves by which larvae of Petrochirus diogenes may be distinguished from all

>E-

FIGURE LI. Petrochirus diogenes. Appendages of the glaucothoe. a, antennule; b, antenna; c, left cheliped, dorsal view; d, right cheliped, dorsal view; d', right cheliped, lateral view; e, fourth pereiopod, lateral view; f, fifth pereiopod; f', detail of fifth pereiopod, lateral view; g-j, pleopods of the second to fifth abdominal somites respectively; k, the tail fan. Scale is 0.5 mm. 164 Bulletin of Marine Science [18(1)

) '··L. c 1968] Provenzano: Larval Development of Petrochirus 165

other known larvae of the Coenobitidea, but the features shared with larvae of other genera are shared independently so that combinations of characters do seem to distinguish described larvae of various genera from each other. One feature of apparent generic importance is the relative length of the rostrum and its shape. Petrochirus is like nearly all other coenobitideans for which larvae have been described, in having the zoeal rostrum longer than the cephalic appendages. An exception is Paguristes in which the rostrum is not longer than the cephalic appendages (Hart, 1937; Pike & Williamson, 1960; Rice & Provenzano, 1965). The rostrum itself usually has a sharp dorsal margin or carina extending back onto the dorsal surface of the carapace. Such a carina is not indicated in published figures of Clibanarius, but it is present in Clibanarius tricolor at least (Provenzano, unpub!.). In Paguristes sericeus the ridge is not prominent on the rostrum itself, but is present on the anterior carapace. The apparent absence of the dorsal carina in Diogenes pugi/ator needs to be confirmed. The rostrum of Clibanarius larvae ends in a very typical constricted tip, a feature not shared with other genera. Other carapacial armature also appears to have generic significance. Petrochirus diogenes has ridges and grooves on the zoeal carapace which are not known for any other species. The anterolateral carapacial spines so characteristic of Paguristes, and present in less prominent form in Trizopagurus (Provenzano, 1967) and perhaps other genera, are definitely missing in Petrochirus. The posterolateral carapace spines of Calcinus (two species published, two more unpublished) are not known in any other genus. The armature of the abdominal somites may be distinctive for all species within a genus or may show some variation within a genus. Petrochirus diogenes is like at least five species of Clibanarius and two species of Dardanus in lacking completely any spination on the dorsal or lateral margins of the abdominal somites. All other genera for which larvae have been described have at least a pair of lateral spines on the fifth abdominal somite and usually a mediodorsal spine as well. Some genera have additional spination on the more anterior abdominal somites. In the genus Dare/anus, D. arrosor of the Mediterranean (Pike & Williamson, 1960) and some larvae from the Indo-Pacific attributed to this genus by Dechance (1962) all have (only) a pair of lateral spines on the fifth abdominal somite, but D. venosus of the West Indies and D. sinistripes of the eastern

+- FIGURE 12. Petrochirus diogenes. Appendages of the glaucothoe. a, right mandible, ventral view; a', right mandible, dorsal view; b, maxillule; c, maxilla; d, first maxilliped; e, second maxilliped; f, third maxilliped. Scale is 0.5 mm. 166 Bulletin of Marine Science [18(1)

:I: ;;3 ••• V.I Z w •• • CL RANGE ...• IV Of VI

• cr@J~ • 09--;'--'. II

11.-----r------r------.------,.------r----'2 4 5 TOTAL LENGTH (MM)

FIGURE 13. Ratio of total length to carapace length in successive stages of P. diogenes reared at 25° C. Hollow circles represent specimens measured after preservation; solid circles represent specimens measured alive. VAt indicates subterminal stage V; Vt indicates terminal stage V. No stage-VI larvae were measured alive for TL, but CL was taken from some exuviae after specimens had completed the molt to glaucothoe. The CL size range of five such stage-VI larvae is indicated; it falls within the approximate size of terminal stage V.

Pacific lack these spines (Provenzano, unpubl.). Variation in abdominal armature occurs in Paguristes also. Thus this feature may be of value for specific differentiation in some genera. General features of the telson are somewhat different in various genera, but there is also minor variation between species. The first zoea in most genera has a slightly to markedly convex posterior tel son margin. In Trizopagurus magnificus and Diogenes pugilator it appears to be straight. The median telson notch in the first zoea varies considerably, from very deep and marked in Clibanarius, to rather shallow in Trizopagurus and Calcinus. In later stages the notch becomes obliterated. One of the most striking features of the telson is the marginal armature. While the total number of marginal processes is the same in the first zoea of all species, the relative lengths may vary between species as in Paguristes. More 1968] Provenzano: Larval Development of Petrochirus 167 important, however, is the change in the fourth process which frequently takes place in the molt to third zoea. In Paguristes this process remains an articulated plumose seta as in earlier stages, but in other genera it normally becomes a nonplumose spine fused to the telson, and is either enlarged or reduced. In the fourth zoea the change is accentuated. The fusion and enlargement of this process in Petrochirus is similar to what occurs in Calcinus, Coenobita, Dardanus, and Trizopagurus. In Diogenes the process is greatly reduced and in some specimens may be absent, while in Clibanarius the process is fused to the telson and becomes considerably reduced, even to a small stub. Another obviously prominent feature of probable generic value is the armature of the antennal scale and the exo-uropodite. In any given species the marginal armature of the exo-uropodite, when it appears, is similar to that of the antennal scale. The number of setae on the scale and exo-uropodite is a variable feature among larvae of the same brood and not a specific character. The terminal spine which arms the scale and exo-uropodite in Coenobita, Calcinus, Paguristes, Trizopagurus, and Diog- ene.l' is absent in Petrochirus, Clibanarius, and three species of Dardanus larvae of known parentage. In species without a terminal spine of the scale, or exo-uropodite, the setation extends onto the lateral margin of the structure. Dechance illustrated a graduated series of antennal scales among planktonic larvae attributed to Dardanus which shows development of the terminal spine, from D. arrosor in which it is absent, through a series of other species to a form similar to that known for other genera. If those planktonic larvae were in fact not of the genus Dardanus, the presence or absence of the antennal spine (and the corresponding armature of the exo-uropodite) may be considered a possible generic feature, since the other genera for which larvae of more than one species are known appear to be consistent. In all hermit-crab larvae there is a serrated spine on the ventral surface of the antennal peduncle just proximal to the endopodite. In some larvae there is an additional process, a short tooth, on the lateral distal margin of the peduncle, proxima] to the antenna] scale. In Calcinus tibicen, Coenobita clypeatus, Paguristes sericeus and Trizopagurus magnificus, the tooth is missing in the first zoea but present in later stages. The situation in Diogenes and Clibanarius is uncertain, but in at least one species of Dardanus (D. venosus), as in Petrochirus diogenes, the tooth is missing throughout development (Provenzano, unpub!.). The proximal medial corner of the first maxilliped varies in shape from one genus to another, and perhaps from one species to another within a genus. Most larvae described have a very prominent hook-like process with a seta at the tip. In Paguristes sericeus, Trizopagurus magnificus, and Clibanarius, the process is not well developed, and there is in its place only 168 Bulletin of Marine Science [18(1) a seta, or sometimes two. This character has not been described in Diogenes, but Petrochirus diogenes is like Calcinus, Coenobita, and Dardanus in having a strong, hook-like process present. General body size of the first larva (and of later stages) varies considerably from one species to another. There is some intrageneric variation in size of first zoea, particularly in Paguristes. Therefore length of carapace or total length, which is a slightly more variable measurement, is useful for specific differentiation. As might be expected from the large size of the adult, the first zoea of Petrochirus diogenes is somewhat larger than that of most other larvae studied. Only the first zoea of Dardanus arrosor, among those described, is larger at hatching and this may correlate with the large size of that species as well. There are no good data yet available showing a general correlation of size of hatching larva with size of mature crab. The glaucothoe stage of Petrochirus is considerably smaller than that known for several species of Dardanus, although the average size of adult Petrochirus may be larger than that of the corresponding species of Dardanus (see discussion below). The number of larval stages in coenobitidean development is highly variable (both intra- and inter-specifically) and probably is of little or no systematic significance. A possible exception may be Paguristes, in which the four species for which the post-embryonic development has been described all have abbreviated development, as do at least six other species from the West Indian region (Provenzano, unpub!.). The segmentation of the endopodite of the maxillule in the Diogenidae varies from one to three, and the setation also varies. These characters show little consistency even within a genus and thus are useful as specific characters. The endopodite of the antenna usually is half the length of the scale, but in Clibanarius erythropus and C. vittatus it is more than half the length of the scale. In all coenobitideans, there are three terminal plumose setae in the first and second zoeae; this armature changes in the third instar. Two of these setae are long in all species for which first-stage larvae have been described, but the third seta, nearly always shorter than the others, is of quite variable length. Extremes may be seen in Diogenes pugilator, where the third seta is only about one-tenth as long as the other two, and in Paguristes sericeus, where the third seta is as long as the others. Thus the length of this seta may be useful as an identification aid, at least at the specific level. The development of the mandible of Petrochirus is shown in Figure 8. An adequate comparison with mandibles of other diogenids cannot be made, for there are almost no illustrations in the literature which show details of the zoea] mandibles at high magnification. An exception is a paper on the development of Trizopagurus magnificus (Provenzano, 1968] Provenzano: Larval Development of Petrochirus ]69

1967). There are differences between the mandibles of these two species, but whether these differences have generic significance is not known. In general the similarities are more striking than the differences, and it will be very interesting to see at what taxonomic level this feature begins to show marked variation. This must await additional work on other species. In summary, the zoeal stages of Petrochirus differ from those of all others described in the ridges and grooves of the carapace. All other "generic" characters are shared with Dardanus. Thus, the zoeal stages of Petrochirus are similar in more ways to those of Dardanus than to those of any other genus for which larvae have yet been described. The social behavior of eight genera of coenobitidean hermit crabs has been studied by Hazlett (personal communication), who informed me that the behavior patterns of Petrochirus and Dardanus are rather similar to each other, but different from all other genera so far studied. Comparisons of the Glaucothoe with Those of Other Hermit Crabs.-The glaucothoes of the Paguridae differ from those of coenobitideans in at least two important features. The right hand is always larger than the left in glaucothoes of the Paguridae, whereas in coenobitideans the hands are nearly always equal; two exceptions are Diogenes, in which the left hand is larger than the right, and Petrochirus as here described, in which the right hand is slightly larger than the left. (The adults of Diogenes and Petrochirus have tbe respective hands larger, as in their glaucothoes.) Another feature of pagurid glaucothoes is that, in all species for which glaucothoe descriptions have been published, there are eight large setae on the posterior margin of the telson, whereas in coenobitidean hermits, the number of telson setae is variable, even within a species. In the glaucothoe stage, features of special importance are: general size, the shape of the eyes and anterior carapace, presence or absence of eyescales, the segmentation of the ventral ramus of the antennule, the number of segments of the antennal flagellum and the setation thereof, the presence or absence of a reflexed palp on the maxillule, the nature of the third maxillipeds (the exopodite is vestigial, the endopodite enlarged, in Coenobitidae [Provenzano, 1962bJ), the shape and armature of the chelipeds, the relative lengths of the dactyls of the second and third pereiopods and their armature, the armature of the protopodite of the uropods, and the shape and armature of the tel son. In general body size, the glaucothoe of Petrochirus diogenes is, like that of Coenobita clypeatus, much larger than the other West Indian diogenid glaucothoes so far described, except those of Dardanus. The unusually large size of Petrochirus adults gave rise to the expectation that the glaucothoe would be at least as large as those of Dardanus venosus and D. insignis. Instead, the glaucothoe of P. diogenes is only about half the size of those. 170 Bulletin of Marine Science [18(1) The glaucothoe of Petrochirus is like those of all other coenobitideans, except Diogenes, in its lack of eyescales. (Diogenes appears to be a rather unusual diogenid. The glaucothoe differs from those of other coenobitideans also in having a concave telson, and grossly asymmetrical chelae. The adults seem different from those of other genera in behavior [Hazlett, unpubl.] and in morphology.) In shape of the eyes, Petrochirus glaucothoes are like those of Dardanus and Calcinus in having the cornea dilated. (Clibanarius has the cornea very slightly dilated, but practically the same width as the eyestalk [Dechance & Forest, 1958; Pike & Williamson, 1960; Provenzano, unpub!.].) In Coenobita, Trizopagurus, Diogenes, and several species of Paguristes the cornea is narrower than the eyestalk. The segmentation of the ventral ramus of the antennule is apparently a generic feature. Petrochirus diogenes has three segments, as in Trizop- agurus magnificus, two species of Clibanarius (c. erythropus and C. tricolor) and two species of Calcinus (c. tibicen and C. verrilli). It differs from Dardanus in which at least three species have four segments, from Paguristes in which at least four species have two segments, and from Coenobita clypeatus in which there is only one. The number of segments in the antennal flagellum is a specific character subject to slight variation intraspecifically, but the differences in range between genera can be large. Thus Petrochirus with approximately 16-17 segments distal to the peduncle has a "medium" number, exceeded by species of Dardanus. D. scutellatus was reported as having 18, but in D. insignis there were 21 (Provenzano, 1963b) and in D. venosus 25-27 (Provenzano, 1963a). Calcinus tibicen has 10-11 segments, but C. verrilli has about 14 (Provenzano, unpubl.) and C. ornatus 13 (Pike & William- son, 1960). Trizopagurus magnificus has about 14 segments (Provenzano, 1967). In Coenobita, both species so far studied have seven segments, and Clibanarius erythropus and C. tricolor each have nine. Diogenes pugilator may have six or seven. Paguristes is variable, with six in P. sericeus, five in P. turgidus and four in P. abbreviatus (Rice & Provenzano, 1965; Hart, 1937; Dechance, 1963). The presence or absence of a reflexed palp in the endopodite of the maxillule of adult hermits has been used as a generic character by other workers. As reported in the previous section, the segmentation of the endopodite in zoeal stages is variable at the specific level. In the glaucothoe stage, the endopodite is always simple, and in some genera the tip is recurved. Petrochirus glaucothoes are like those of Dardanus in lacking a palp or lateral appendix on the endopodite of the maxillule. The feature has not been illustrated for Diogenes glaucothoes, but adults of that genus lack the palp. All other described glaucothoes have a reflexed tip of the endopodite. (That for Clibanarius has not been illustrated, but adults of 1968] Provenzano: Larval Development of Petrochirus 171 that genus do have a reflexed palp.) It is likely that presence or absence of this structure will be a useful aid in placing to correct genus those planktonic glaucothoes which have not yet been described. For instance, in the West Indian faunal region, glaucothoes of only two more genera need to be known before a generic key to coenobitidean glaucothoes of this area can be made. Since all genera in this region but Allodardanus and lsocheles have had their glaucothoes described, the field-collected, post-zoeal stages of these genera may be separable on the basis of the maxillule once they are found, for Allodardanus has a well-developed reflexed palp whereas lsocheles has none. (The only other genus of Diogenidae in the western Atlantic is Loxopagurus Forest, 1964, which is distributed between 13° Sand 27" S and is hence unlikely to contribute glaucothoe stages to the Caribbean plankton.) The setation of the maxillular endopodite varies from one genus to another and may even be of specific significance rather than generic, but there is not yet sufficient information on this point. The character of the third maxilliped is probably of generic value, since adults of the Diogenidae show variations in armature, particularly of the proximal segments. However, there are not yet sufficient good illustrations of this appendage in diogenid glaucothoes to permit intergeneric comparisons. At the familial level however, there is a very strong difference between the third maxilliped in Coenobita glaucothoes and the typical diogenid maxillipeds. In the glaucothoe of land hermits, the exopodite is greatly reduced, apparently non-functional, and the endopodite is very well developed. The symmetry of the chelae is one of the primary features by which most coenobitidean glaucothoes may be distinguished from those of the Paguridae. Two aberrant genera in this regard are Diogenes, in which the left chela of the glaucothoe is much larger than the right, and Petrochirus, where the right chela is slightly larger than the left. The armature of the chelae also varies from one genus to another, but there is not sufficient information to evaluate the specific variation within genera. In Petrochirus there are small tubercles on the movable dactyl, apparently lacking in other genera, and there is a notable spine on the carpus. Petrochirus diogenes has the dactyl about equal to the propodus, in contrast to Dardanus, in which the glaucothoe has the dactyl shorter than the propodus. The length of the dactyl of the second and third pereiopods relative to the respective propodus varies between genera, probably in correlation with the condition in adults, but in some genera this is a specific character. The ventral armature of both dactyls is of special importance and is apparently a generic character. In Petrochirus, the dactyl of the second pereiopod has six distally directed thin spines on the ventral margin, in 172 Bulletin of Marine Science [18 (1) addition to the terminus. Other genera have a variable number of such spines, but Dardanus is exceptional. In this latter genus there are two large, broad teeth normal to the ventral margin of the dactyl. The third pereiopod in most genera is armed similarly to the second, but in Pet- rochirus, the dactyl of the third pereiopod has four large, broad teeth of the type in Dardanus, all recurved toward the body. Thus the dactyl and propodus of both the second and third pereiopod of aU glaucothoes should be illustrated and compared with others as probably very useful generic features. One of the most readily observed generic and specific characters of glaucothoes is the form and armature of the telson. In Petrochirus, the length is double the maximum width, and the general shape of the telson is rectangular. In Dardanus the shape is variable, but the length is somewhat greater than the width, and again the posterior margin is almost transverse, giving a subrectangular appearance to the telson. In Coenobita, the length of the telson is less than the width, and the telson is suboval. rn Paguristes, the shape of the telson is variable. In Clibanarius, the telson is generally suboval, and in Trizopagurus, again the telson is subrectangular. As mentioned above, the telson in Diogenes is aberrant, being concave on the posterior margin. The setation of the tel son is a specific character. In summary, the glaucothoe of Petrochirus diogenes differs from all other coenobitidean glaucothoes described in having the right hand larger than the left, in having a telson twice longer than wide, subrectangular in shape, and in having four broad teeth on the ventral margin of the dactyl of the third pereiopod while having, on the dactyl of the second pereiopod, slender spines. In addition to the above characters, the glaucothoe of Petrochirus differs from those of Dardanus species in lacking broad teeth on the second pereiopod while having four teeth rather than two on the dactyl of the third pereiopod, in having a spine on the distal dorsal margin of the carpus of each cheliped, and spines on the manus, and in having three rather than four segments in the ventral ramus of the antennule. It is like those of Dardanus in the presence of broad teeth on the dactyl of the third pereiopod and in the absence of a reflexed palp on the maxillular endopodite. It shares with Dardanus a dilated cornea, a feature also shared with Calcinus. Other features in which it differs from those of Dardanus are either of specific significance or of uncertain systematic value.

EXPERIMENTAL RESULTS AND DISCUSSION Variation in Number of Larval Stages.-In addition to the series which had been in isolation since the first day after hatching, mass cultures at 250 C were maintained. At 11 days after hatching, 10 stage-III and 62 stage-II larvae were isolated from this mass and placed at 300 C. An 1968] Provenzano: Larval Development of Petrochirus 173 additional 47 stage-II larvae were isolated and then kept at 25° C. At 30°, a total of 40 glaucothoes were obtained, all of them after five zoeal stages. Only one animal molted to stage VI, and that one was abnormal at least as early as the fifth stage; it died in the molt from VI to glaucothoe. Numerous apparently normal stage-V animals also died in the terminal molt to glaucothoe at 30° C. At 25° C, at least 17 animals survived the molt from stage V to glaucothoe, but in addition, at least 12 specimens molted (as of ] 2 Sept.) successfully into stage VI. Molting and growth are semi-independent processes in a large variety of decapod larvae, as has become apparent in the course of work by the present writer, colleagues, and other workers. If growth is somewhat retarded as a result of low availability of food and if molting occurs on a more or less constant basis at a given temperature, then the number of instars through which larvae will pass prior to metamorphosis will vary as a function, in part at least, of food. The size range of zoeal stages which yielded glaucothoes of P. diogenes was similar for short series (five zoe a] stages) and long series (six zoea] stages), suggesting that total achieved size or biomass, rather than number of molts, is a primary requirement for metamorphosis. If low availability of food or intermittent feeding is a factor in delaying metamorphosis through retardation of growth, the importance of this in the problem of distributional potential for larvae will be apparent. Effect of Temperature on Survival Time of Starved Larvae.-All larvae which were starved died without molting, regardless of the temperatures at which they were kept. Larvae were considered dead when opaque or when no movement of any appendage or internal structure could be seen under moderate magnification. Figure 14 shows the survival times of starved larvae at the five experimental temperatures. 'Since inspection of larvae did not always take place at the same time of day, these curves must be considered as having an error of plus or minus 0.5 day. The shorter survival time of starved larvae at 25° and 30° C, as compared with that of animals at 20° C, may be presumed due to the more rapid consumption of stored yolk reserves. At temperatures below 20° C, the mortality was apparently a direct effect of the cold, as even fed larvae at those temperatures died after similar times (see below). Effect of Temperature on Duration of Larval Stages of Fed Animals.- Figure 15 shows the sequence and duration of larval stages at the various temperatures used, for fed animals. All larvae kept at 10° C and 15° C died without molting, just as had all starved larvae at all temperatures. Fed and starved larvae at 10° C died at similar times. There may have been a tendency for fed larvae at ] 5 ° C to live a couple of days longer than their starved siblings at the same temperature. That the survival 174 Bulletin of Marine Science [18(1)

36 NUMBER ALIVE C, 100'1. MORTALITY o SO'll. MORTALITY

18 15' w < 36 ell:> ....j« •••• 18 20' 0

Q: w a:l ~ 36 ::::> Z

18 25'

o 2 4 6 8 10 12 DAYS AFTER HATCHING

FIGURE 14. Survival of starved first-stage zoeae of Petrochirus diogenes kept at various temperatures. 1968] Provenzano: Larval Development of Petrochirus 175

18 w "'36 ~::::~~~I..~/:~.='~34_= ~:=_:_;_~0__=;:=_~~6---;:__~ 36

(" 30' / •..----- 18 , '" ' - ~" ,"___ 3.4 36 38 II .~", III X 1\ -~-_t_ (, .

'~-- --"" •••••• ;>-<- - .-'.- - •••• ------_-....._""--~:.:-::------8 10 12 1.4 16 18 20 22 24 26 28 30 32 DAYS AFTER HATCHING

FIGURE 15. Duration and survival of larvae of Petrochirus diogenes at various temperatures when provided with Artemia nauplii as food. None of the larvae at 10° or 15° C molted, and the survival time of those is similar to that of starved specimens. At 20° C, the individuals in fifth zoeal stage all died in the molt to glaucothoe at points indicated by am". The sharp drops in stage-II larvae at 25° C on the seventh day after hatching and at 20° C on the 19th day after hatching represent specimens removed from the experimental group. G indicates glaucothoe; C1 indicates crabl• curves at 10° C and 15° C did not differ much for fed larvae and starved larvae suggests that the deaths were a direct effect of temperature and not due to a failure to feed. At temperatures of 20° C and higher, fed larvae were able to molt and grow. The curves are based on an initial number of 36 larvae (isolated) in each experiment. If the data obtained from animals reared in mass culture prior to isolation at the end of the second stage were added or superimposed, the same general pattern would be seen, but of course larger numbers would be surviving at corresponding places along the time axis. Glaucothoes were obtained at 30° and 25° and, if larger numbers had been used, might have been obtained at 20°. Unfortunately a few specimens at 20° were accidentally lost, thus reducing the available number slightly, but this occurred only after nearly three weeks, so the primary factor in failure of larvae to become glaucothoes at this temperature was the attrition spread over the developmental period. For instance, at 18 days after hatching there were 14 larvae still alive at 20° and at 25 0, and 176 Bulletin of Marine Science 118(l}

U U 015. 1"115. - '" - '"

II") J U III 0'\ 0 I c:o.. or, o:l '" III E~

1.0-: 'U u Mill 0 M 0.. 0 ' c:: '" ..... ""';('0 III 1.0 El""l '-'

:1lI 0 .....• .s:: •....• .....• •....• .....• .....•> '0 ... "" > () .-< ~ o:l o:l o:l o:l o:l ;:l .n .n0' III III III III III o:l o:l ('0 •....'"c: 0 0 0 0 0 I- •... N N N N N 0 U U 1968] Provenzano: Larval Development of Petrochirus ]77

WV ~ ,I

••••< IV III

III

II 20' ISOLATED 25' ISOLATED 25' MASS, THEN ISOLATED 30' ISOLA TED 30' MASS, THEN IS:llATED

6 8 10 12 14 16 18 MEAN DURATION IN DAYS

FIGURE 16. Mean duration of larval and early postlarval stages of Pe/rochirus diogenes at several temperatures. At 25° and 30° C, some individuals had been left in mass culture until after the second stage and were then isolated. All other specimens were isolated from the time of hatching. Data for these curves are from Table 1, and are based on individuals which survived the molt from the respective stage. An exception is the point for duration of stage V at 20° C, for which the termination of the stage was taken to be the day the animal began its molt to glaucothoe. V"t indicates subterminal stage V; Vt indicates terminal stage V; G indicates glaucothoe; Cl indicates crabl stage; C2 indicates crab~ stage. only 12 at 30°. However, at the highest temperature most were in the 5th stage and two days later glaucothoes began to appear, whereas at the lowest temperature some individuals were still in the second stage and others were only in the third. Thus, although the survivals were similar up to that point, the stage of development after a given time period was very much dependent upon temperature. The earliest attainment of glaucothoe stage at 25° C (24th day after hatching) was four days later than at 30° C (20th day after hatching). At 20° C, none of the four specimens dying in the molt from the last zoeal stage actually survived the molt, but they were obviously glaucothoes at the time of death. The 178 Bulletin of Marine Science [18(1) initiation of the molt to glaucothoe at 20° C took place on the 46th, 48th, and 56th days after hatching. (The longest surviving individual died, still not free from the old exuvia, 62 days after hatching.) Thus the zoeal phase of development occupied a minimum of 20 days at 30° C, 24 days at 25° C, and 46 days at 20° C. At temperatures of 25° and 30° C the total duration of zoeal life is much shorter (26 ± 2 days at 25 0, and 24 ± 2 days at 30°) than at 20° C (approximately 50 ± 6 days). Approximately half the time is required at temperatures of 25-30° as compared with 20° C. Although no data were obtained for duration of glaucothoe at 20° C, there is no reason to assume that this duration would not be correspondingly longer than at the higher temperatures. If the duration of the glaucothoe stage at 20° were, like the zoeal phase of development, approximately double the duration at 25°, it would be about 26 days. The glaucothoe phase represented about one-third the total planktonic duration. Thus the total duration of planktonic life of Petrochirus diogenes might vary from a minimum of 31 days after hatching at 30° C, to 37 days minimum at 25° C, and to about 72 days at 20° C. The maximum duration possible might be considerably more, as a first-stage crab was obtained on the 43rd day after hatching (30°) and on the 50th day after hatching at 25° C. The approximate equivalent maximum at 20° C would be on the order of 84 days after hatching, or, nearly three months. Since the glaucothoe does not remain pelagic for its entire existence, but goes to the bottom as final metamorphosis approaches, the figures given here for maximum duration of planktonic life are perhaps high, but on the other hand, the number of specimens available for these estimates was very small, and in a much larger population, greater variation may be expected. The minimum, maximum, and mean durations of each stage at each temperature, based on data only from individuals which succeeded in molting to the subsequent stage, are presented in Table 1. Figure 16 is a plot of mean duration of each stage for each of the experimental groups. From this figure it is apparent that the first zoeal stage has a longer duration at all temperatures than the stages immediately following. At all temperatures, there was a very pronounced extension of duration at the end of larval development, especially in the glaucothoe stage. Whether the longer duration of the first zoeal stage is due to lesser ability of the animals to capture and eat the Artemia nauplii provided as food or whether there is another factor involved is uncertain at this time. The prolongation of the last zoeal stage is undoubtedly related to the extensive internal reorganization of tissues and organs which begins to take place near the end of the zoeal phase of development. The very markedly longer duration of the glaucothoe stage is probably due primarily to this same process, 1968] Provenzano: Larval Development ot Petrochirus 179 since it is during the glaucothoe stage that the abdominal musculature and pleopods degenerate, the arterial system is reorganized, and the liver, sexual cells, and green glands become wholly or partly abdominal in location (Thompson, 1903). It is not known how far in advance of the molt to crab stage the reorganization may be completed. In the species of Pagurus studied by Thompson the entire glaucothoe stage lasted only 4-5 days. The internal reorganization is completed by the time the first crab stage is reached, and the intermolt duration of first and second crabs therefore is shortened relative to duration of the glaucothoe.

SUMARlO DESARROLLO LARVAL COMPLETO DEL CANGREJO ERMITANO DE LAS ANTlLLAS, Petrochirus diogenes (L.), (DECAPODA, DlOGENIDAE) CRIADO EN EL LABORATORIO Se sigui6 en el laboratorio el desarrollo comp]eto de las zoeas y el desarrollo inicial de ]a post larva del cangrejo ermitaiio rojo, grande, comun, de las Antillas, P. diogenes. Puede haber cinco 0 seis estados de zoeas antes del g]aucotoe, dependiendo de la temperatura. Los estados de zoea y glaucotoe se compararon en detalle con los de otras especies de Diogenidae y Coenobitidae y se evalu6 el significado sistematico de varios caracteres morfol6gicos. Los estados de zoea de esta especie difieren de todos los otros descritos, en que tienen e]evaciones y surcos en e] carapacho. Otras caracteristicas genericas son compartidas con larvas de Dardanus, indicando una mayor similitud entre Petrochirus y Dardanus que entre cualquiera de estos generos y los otros cuyas larvas son conocidas. EI g]aucotoe de Petrochirus se diferencia de los de Dardanus en que carece de dientes anchos en e] segundo periopodo mientras que tiene cuatro dientes en vez de dos en el dactilo del tercer periopodo, que tiene una espina en e] margen dorsal distal del carpo de cada quelipedo, que tiene espinas en las manos y que tiene tres en vez de cuatro segmentos en la rama ventral de la antenula. Es como los de Dardanus en que presenta dientes anchos en el dactilo del tercer periopodo y en que no tiene un palpo replegado en el endopodito de la maxflula. Comparte con Dardanus una c6rnea dilatada, que tambien es compartida por los g]aucotoes de CaJcinus. Otras caracteristicas en las que el glaucotoe de Petrochirus difiere de los de Dardanus son de significado especifico 0 de valor incierto. Las larvas hambrientas no fueron capaces de mudar a ninguna de las cinco temperaturas usadas, pero la supervivencia fue mayor a 20° C que a temperaturas mas bajas 0 mas altas que esa. A 10° y 15° C, las larvas a las que se les suministr6 nauplius de Artemia como alimento tambien fueron incapaces de mudar y murieron aproximadamente en el mismo tiempo que las siblins hambrientas. A 200, 25° Y 30° C, las larvas co- 180 Bulletin of Marine Science [18(1) rrectamente alimentadas fueron capaces de mudar y continuar creciendo. A 20° C no se obtuvieron glaucotoes viabIes porque los pocos individuos que alcanzaban el estado final murieron en la muda a glaucotoe. A 25° C se obtuvieron glaucotoes despues de cinco y seis estados de zoea. A 30° C casi todos los ejemplares pr6ximos al estado de glaucotoe, 10 alcanzaron despues de s610 cinco estados de zoea. A todas las temperaturas el primer estado de zoea tuvo una mayor duraci6n media que los estados que 10 siguieron inmediatamente, pero la duraci6n aument6 otra vez en los ultimos est ados de zoea y alcanzaron un maximo en el estado de glaucotoe. La duraci6n total de la fase de zoea del desarrollo fue aproximadamente 50 dias a 20° C y aproximadamente 25 dias a las mas altas temperaturas usadas. Como que el glaucotoe es tam bien planct6nico en gran parte de su existencia, la vida planct6nica potencial total de est a especie puede variar de 31-43 dias a 30° C, de 37-50 dias a 25° C y de 72-84 dias a 20° C. LITERATURE CITED ALVES COELHO, P. ] 964. Alguns crustaceos decapodos novos para Pernambuco e Estados vizinhos na Colec;ao Carcinol6gica do Instituto Oceanognifico da Universidade do Recife. Ciencia e Cultura, 16 (2): 255-256. BOUVIER, E. L. 1895. Sur une collection de Crustaces decapodes recueillis en Basse- Californie par M. Diguet. Bull. Mus. Nat. d'Hist. nat., Paris, 1: 6-8. DECHANcE, M. 1962. Remarques sur les premiers stades larvaires de plusiers especes Indopacifiques du genre Dardanus (Crustaces Decapodes Pagurides). Bull. Mus. Nat. d'Hist. nat., Paris, Ser. 2, 34 (1): 82-94. 1963. Developpement direct chez un paguride, Paguristes abbreviatus Dechance, et remarques sur Ie developpement des Paguristes. Bull. Mus. Nat. d'Hist. nat., Paris, Ser. 2, 35 (5): 488-495. DEC HANcE, M. AND J. FOREST ]958. Les glaucothoes de Catapaguroides timidus (Roux) et de Clibanarius erythropus (Latreille). Remarques sur Ie stade post-Iarvaire des pagurides. Bull. Soc. Zool. France, 83 (2-3): 274-293. FOREST, J. 1964. Sur un nouveau genre de Diogenidae (Crustacea Paguridea) de l'Atlantique Sud-America in, Loxopagurus gen. nov., etabli pour Pagurus /oxochelis Moreira. Zool. Meded., Leiden, 39: 279-296. HART, J. F. L. 1937. Larval and adult stages of British Columbia Anomura. Canad. J. Res., D, 15: 179-220, 7 pis. HOL THUIS, L. B. 1959. The Crustacea Decapoda of Suriname (Dutch Guiana). Zool. Verhand., Leiden, No. 44: ]-296, pIs. I-XVI. HULINGS, N. C. 1961. The barnacle and decapod fauna from the nearshore area of Panama City, Florida. Quart. J. Fla. Acad. Sci., 24 (3): 215-222. 1968] Provenzano: Larval Development of Petrochirus 181

MACDoNALD, J. D., R. B. PIKE, AND D. I. WILLIAMSON 1957. Larvae of the British species of Diogenes, Pagurus, Anapagurus, and Lithodes (Crustacea, Decapoda). Proc. ZOO!.Soc. Land., 128 (2): 209-257. MILNE-EDWARDS, H. 1848. Note sur quelques nouvelles especes du genre Pagure. Ann. Sc. nat. Zool., Ser. 3, 10: 59-64. PIKE, R. B. AND D. I. WILLIAMSON 1960. Larvae of decapod Crustacea of the Families Diogenidae and Paguridae from the Bay of Naples. Pubbl. Staz. zool. Napoli, 31 (3): 493-552. POUNDS, S. G. 1961. The crabs of Texas. Texas Game and Fish Comm. Bul!., No. 43, (Ser. 7): 1-57. PROVENZANO, A. J. 1959. The shallow-water hermit crabs of Florida. Bull. Mar. Sci. Gulf & Carib., 9 (4): 349-420. 1962a. The larval development of Calcinus tibicen (Herbst) (Crustacea, Anomura) in the laboratory. Bio!. Bull., 123 (I): 179-202. 1962b. The larval development of the tropical land hermit Coenobita ely- pea Ills (Herbst) in the laboratory. Crustaceana, 4 (3): 207-228. 1963a. The glaucothoe stage of Dare/anus venosus (H. Milne-Edwards) (Decapoda: Anomura). Bul!. Mar. Sci. Gulf & Carib., 13 (I): 1] -22. 1963b. The glaucothoes of Petrochirus diogenes (L.) and two species of Dare/anus (Decapoda: Diogenidae). Bull. Mar. Sci. Gulf & Carib., 13 (2): 242-261. 1967. The zoeal stages and glaucothoe of the tropical Eastern Pacific hermit crab, Trizopagurus magnificus (Bouvier, ]898) (Decapoda; Dio- genidae), reared in the laboratory. Pacific Sci., 21 (4): 457-473. RATHBUN, M. J. 1918. Contributions to the geology and paleontology of the Canal Zone, Panama, and geologically related areas in Centra] America and the West Indies. Decapod crustaceans from the Panama region. U. S. Nat. Mus. Bul!., 103: 123-184, pIs. 54-56. RICE, A. L. AND A. J. PROVENZANO 1965. The zoeal stages and the glaucothoe of Paguristes sericeus A. Milne- Edwards (Anomura, Diogenidae). Crustaceana, 8 (3): 239-254. TOULA, F. 1911. Die jungtertiaere Fauna von Gatun am Panamakana!. II. Tei!. Jahrb. Kaiser]ich-Koniglichen Geologischen Reichsanstalt, Wien, 61: 487- 530, 2 pIs. THOMPSON, M. T. 1903. The metamorphoses of the hermit crab. Boston Soc. nat. His!., 31 (4): 147-209, pIs. 4-]0. WILLIAMS, A. B. ]965. Marine decapod crustaceans of the Carolinas. U. S. Fish Wildl. Serv., Fish. Bull., 65 (1); i-xi + 1-298. WILLIAMSON, D. I. 1965. Ethylene glycol as a preservative for marine organisms. Nature, 206 (499\); 1370-1371.

&lt;I&gt;Petrochirus Diogenes&lt;/I&gt;

<I>Petrochirus Diogenes</I>