THE BEHAVIOR OF SOME DEEP-WATER HERMIT CRABS (: PAGURIDEA) FROM THE STRAITS OF FLORIDA!

BRIAN A. HAZLETT Institute of Marine Science, University of Miami and Biological Laboratories, Harvard University

ABSTRACT The behavior of specimens of eleven of hermit crabs, collected from depths of 110 to 713 meters, was observed in the laboratory (Dio- genidae: anomalus, spinipes, Paguristes moorei, Paguristes "A", and Dardanus insignis; Paguridae: Benthopagurus cokeri [new combination], Pagurus rotundimanus, Pagurus politus, Pylopagurus discoidalis, Parapagurus piClUs, and Spiropagurus iris). The aggressive displays executed as individuals approached one another are described for each species. These movements of the chelipeds and ambulatory legs are similar to those of congeneric species from shallow water. Pagurid hermits exhibited extreme avoidance of conspecific individuals during diurnal observation periods. Specimens of Pagurus politus showed a peculiar "appeasement" behavior whereby individuals could come closer than usual to one another. The behavior patterns associated with shell fighting are described for four species (Clibanarius anomalus, Paguristes moorei, Dar- danus insignis and Pylopagurus discoidalis). Several adaptations of the behavior of Pylopagurus discoidal is affected by inhabiting scaphapod shells are described.

INTRODUCTION A number of species of hermit crabs, especially in the family Paguridae, are found well below the littoral zone. The social behavior of the shallow- water hermit crabs of Cura<;ao, N.A. (Hazlett, In Press) and of the Miami area (Hazlett, MS) has been examined from a comparative viewpoint. Although each species observed has a characteristic repertoire of be- haviors, the patterns of all shallow-water species examined are markedly similar. The intraspecific interactions of some deep-water species were observed both for systematic purposes and to compare the behavior of these forms with that of shallow-water species. The 11 species considered in this paper were collected by bottom trawls and dredges between 60 and 390 fathoms (110-713 m) during cruises by University of Miami vessels, the RjV JOHN ELLIOTT PILLSBURY and the RjV GERDA. The range of these cruises extended from Key West to

'Contribution No. 669 from the Institute of Marine Science, University of Miami. This work was supported by fellowship F 2 MH-14, 274 from the National Institutes of Health and a Grant-in-Aid of Research from the Society of the Sigma Xi. Biological Ship time was supplied by Grant GB-1204 from the National Science Foundation. The material reported here was collected with the coopera- tion of the National Geographic Society-University of Miami Deep-Sea Biology Program. 1966] Hazlett: Deep-water Behavior 77 Bermuda but the majority of the collecting was done in the Straits of Florida proper. When brought on deck, the specimens were quickly placed in individual containers of cooled Florida Current water in a refrigerator. Observations were carried out by placing the specimens of one species together in a cooled aquarium with sand on the bottom and watching them for periods of 30 to 45 minutes, except when prolonged interactions ex- tended beyond this time. All observations of specimens collected on the RjV GERDAwere carried out at the Institute of Marine Science in Miami. were maintained at 10°, 15°, or 20° C depending on the depth and area they came from and were kept on a schedule of 12 hours illumi- nation and 12 hours dark. Except when placed together for observation, the specimens were kept in individual containers of Gulf Stream water. The change in water temperature during an observation period was 1°_2° C. Although the level of general activity sometimes appeared to increase slightly as the water temperature rose, the character of the move- ments executed during social interactions did not change. Observations at night were carried out with a "red light" (an ordinary low wattage red light bulb, not a monochromatic source) at some times and a low level white light at other times. The conditions of carrying out the observations and the limited number of specimens available make these descriptions preliminary in nature. With several exceptions, however, the behavior patterns observed were not at all unusual when compared with the laboratory and field behavior of related shallow-water hermit crabs (Hazlett, In Press and MS). Indeed, the similarity between the behavior of these deep-water species and that of congeneric shallow-water forms was surprising in view of the difference in light conditions in the field for the two groups. The author wishes to thank Mrs. Edith Marks and Talbot E. Murray, Jr. for their help in maintaining specimens in the laboratory and Dr. A. J. Provenzano, Jr. of the Institute of Marine Science, for his aid and advice. Species identifications were confirmed by Dr. Provenzano. Most of the specimens observed in this study have been deposited in the Institute of Marine Science Museum. The patterns described in this paper belong to two categories of aggres- sive behavior-general aggressive behavior and shell fighting behavior. The latter is an exchange of signals between two crabs which effects an exchange of shells without physical damage to the interacting crabs. In the twelve shallow-water species observed in Cura<;ao (Hazlett, In Press), the general outline of events was the same in all species although there were distinct familial, generic and specific characteristics in the execution of most acts. The attacking crab approaches another crab and, after an exchange of visual displays (see below), gets into an opposed position with respect to the other crab. In this position, the apertures of the two shells are facing, 78 Bulletin of Marine Science [16(1)

FIGURE 1. Schematic diagrams of the aggressive displays of hermit crabs. The dotted outlines indicate the resting position of the limb. Appendages other than those involved in the display illustrated have been omitted. A. Side view of a Pagurus species, showing the major cheliped presentation (manus moved through almost 100° from its resting position to 10° beyond the vertical) and the major cheliped extension (moving the manus another 80° upward to a horizontal position). B. Front view, showing a single ambulatory raise (45° of movement to a position 20° below the horizontal). 1966] Hazlett: Deep-water Hermit Crab Behavior 79 forming an angle of about 30° with one another. The attacking crab has its ambulatory legs around the aperture of the defender's shell and is usually above the defender. The latter is withdrawn in its shell. From this position, the attacker carries out positioning movements (basically a rock- ing from side to side of the attacker's body-shell) and then rapping move- ments (a rapid bringing together of the two shells by the attacker). After the execution of a number of these movements, the defending crab may come competely out of its shell and move onto the back of the shell of the attacker. The two crabs then exchange shells. In addition to this form of interaction, individuals of all species also interact in a more general way. Hermit crabs are not territorial but like most animals have an individual distance. When another crab moves too close to an individual, it usually responds to the presence and/or move- ments of the other either by retreat or the execution of a stereotyped visual display. In most species of hermits, physical damage between con- specific individuals almost never occurs but rather, exchanges of these display movements result in one crab moving away or ducking back into its shell. The three most common displays have been termed the ambula- tory raise, the cheliped presentation and the cheliped extension. The speed and extent of movement of the respective limbs in these displays vary from species to species. When one crab executes a display, the other usually responds by either retreating or executing a display. Thus long series of exchanges of displays may occur before one or both crabs move away. Smaller crabs usually retreat from just the approach of a larger crab or from the execution of a cheliped presentation movement. The ambulatory raise and cheliped extension displays are stronger aggressive signals and in extended en- counters, the simultaneous movement of several ambulatory legs and both chelipeds is common. It is difficult to clearly describe the limb movements involved in these displays in a few words. The terminology used in these descriptions is illustrated in Figure 1. The cheliped presentation display (Fig. lA) brings the limb(s) forward (with little lateral movement) from the normal resting position-some degrees posterior to the D-V axis-until the manus is approximately vertical (parallel to the D-V axis). In the extension display, the limb is moved forward farther. In both movements the proximal segments of the chelipeds are moved almost to the horizontal (parallel to the A-P [anterior- posterior] axis). In each species, these movements are described in terms of the movement of the manus (number of degrees in the angle formed by lines connecting the tip of the dactyl of the manus and the carpus-manus articulation in the two positions) and the final position of the manus (degrees anterior or posterior to the vertical or degrees below the horizon- 80 Bulletin of Marine Science [16(1) tal). The ambulatory raise movement (Fig. IB) brings the limb(s) from the normal walking position, laterally upward, to a position in which some or all segments of the limb are almost horizontal (at right angles to the D-V [dorso-ventral] axis of the ). In some species, the segments are approximately straight in the raised position. In others the dactyl may be declined below the line of orientation of the other segments. In the simplest case, only the degrees of movement of the dactyl (the number of degrees in the angle formed by lines connecting the dactyl and coxa of the limb in the two positions) and the final position (in degrees below the hori- zontal) are given. Unless otherwise mentioned, no anterior-posterior move- ment of the limb occurs.

RESULTS Family Clibanarius anomalus (H. Milne-Edwards, 1848) GERDA stations, G-526 (220-170 fms; 403-311 m) and G-533 (210-220 fms; 384-403 m). Three specimens observed. Specimens of this medium-sized species moved about rather slowly both at 150 and 200 C, usually dragging their shell on the substrate. When two crabs came close to one another, they frequently moved their chelipeds in one of two stereotyped patterns. The execution of a display was usually followed by either the execution of a display by the other member of an interacting pair or retreat by that crab. As was true of most species observed, when the crabs were placed in an observation container, there was rarely any direct movement toward one another. Interactions occurred as crabs encountered one another in their general movement about the container. The cheliped presentation display in this species was a movement 0 through about 40 , bringing one or both chelipeds to a position where the proximal segments were almost horizontal. The mani were perpendicular to the substrate, with the tips of the dactyls slightly off the substrate. The appendage was either maintained in this position for some seconds, quickly returned to a position beneath the mouth region, or moved forward and upward in a cheliped extension movement. In the latter display, the appendage(s) was moved rather slowly and smoothly until the manus of the cheliped was about 250 below the horizontal, dactyls slightly open. The appendage was either maintained in the extended position for several seconds or was lowered almost as soon as it was extended. No display movements of the ambulatory legs were observed. One shell fight was observed. Initially, the attacking crab held the de- fending crab in an opposed position with its ambulatories and performed positioning movements. These consisted of rocking the defending crab laterally from side to side around an axis through the aperture of the 1966] Hazlett: Deep-water Hermit Crab Behavior 81 defender's shell. Following positioning, the attacker executed a series of rapping movements, rapidly bringing its shell into contact with that of the defender in short series of raps. As the attacker's shell was lifted up, about one-third of its cephalothorax was exposed. The rapping was slow, taking about 1.5 sec per cycle of movement. There was a marked pause in each cycle, when the attacker's shell was in the raised position. This resembles the behavior of Clibanarius cubensis and C. vittatus and is in contrast to that of C. tricolor and C. antillensis, in which there is a pause when the attacker's shell is in the lowered position. The attacking crab frequently executed positioning movements between series of rapping movements.

Paguristes spinipes A. Milne-Edwards, 1880 PILLSBURYstations, P-198 (120-125 fms; 219-228 m): P-199 (150- 160 fms; 274-293 m): and P-200 (180-190 fms; 329-447 m). GERDA stations, G-251 (160-170 fms; 293-311 m): and G-482 (110 fms; 201 m). Twelve specimens observed. This rather large species was one of the more common hermit crabs obtained in trawls in the Straits of Florida. It was a rather slow moving crab and at 150 C was not very active at any time. Several specimens kept at 250 C were similarly sluggish and slow moving. Individuals did not clearly react as regularly to one another's presence or movements as other species of hermit crab do. Individuals in the Paguristes tend to "ignore" one another and P. spinipes showed this tendency rather strongly. As individuals came together, two types of cheliped movements were observed. The cheliped presentation display, bringing the manus of the appendage through 450 to about 50 beyond the vertical (anterior to a line parallel to the D-V axis), was executed a number of times. In extended interactions, single or double cheliped extension movements were also executed. This display brought the manus to about 400 below the hori- zontal. Both were slow movements, and in both the mani were turned medially rather strongly (at an angle to the plane formed by the D-V axis and A-P axis) and the dactyls were slightly open. On a few occasions, a single ambulatory raise movement was executed. A first ambulatory leg (second pereiopod) was rather slowly moved laterally through 250 to about 250 below the horizontal. The limb was not rigid during movement and was definitely curved downwardly when fully raised. It was either maintained in the raised position for several seconds or lowered at once. Paguristes moorei Benedict, 1901 PILLSBURYstation, P-198 (120-125 fms; 219-228 m). Nine specimens observed. This species is morphologically and behaviorally very similar to Paguris- 82 Bulletin of Marine Science [16 (1) tes spin/pes but was much more active when maintained at the same temperature (150 C). It moved about with moderate speed and social interactions were frequently observed. The cheliped presentation display was executed more quickly but other- wise was similar to that of P. spinipes. The cheliped extension display brought the manus to 15 a below the horizontal. Unlike P. spinipes, in both displays the mani were oriented parallel to the plane formed by the D-V axis and A-P axis. The extension display was a moderately slow move- ment, taking a little less than a second to execute. During interactions, one or both first ambulatory legs were sometimes raised rapidly upward and outward to a position about 100 below the horizontal. There was little forward movement, but the limb was not rigid (the distal segment was moved up noticeably after the proximal ones) and was curved downward when fully raised. Shell fighting behavior was similar to that described for Clibanarius anomalus except that during positioning the movement by the attacker described a horizontal figure 8 (instead of a smooth arc), moving back and forth as it moved from side to side.

Paguristes "A" GERDAstations, G-482 (110 fms; 201 m) and G-480 (l05 fms; 192 m). Eleven specimens observed. This species, originally identified as Paguristes lymani A. Milne-Edwards and Bouvier, 1890, is an apparently undescribed species, closely resem- bling P. lymani. (Provenzano, personal communication.) This detritus covered species resembles P. spinipes very closely in its behavior. It was rather sluggish, moved about slowly, and executed its aggressive display movements slowly. The cheliped presentation display and cheliped extension movements were frequently executed during interactions, although crabs often moved by or passed each other without any observable change in behavior. The cheliped displays were almost identical to those of P. spinipes. No ambulatory displays or shell fights were observed.

Dardanus insignis (Saussure, 1858) PILLSBURYstation, P-198 (120-125 fms; 219-228 m). GERDAstations, 0-388 (174 fms; 318 m): 0-419 (70-60 fms; 130-110 m): and 0-390 (135-150 fms; 247-274 m). Nine specimens observed. This active species was found living not only in gastropod shells but also in straight, calcareous worm tubes. It showed a full repertoire of ag- gressive displays during interactions with conspecific individuals. Many of its movements closely resembled those of Petrochirus diogenes (Hazlett, MS). 1966J Hazlett: Deep-water Hermit Crab Behavior 83 A cheliped presentation display was frequently executed as one crab approached another. The limb(s) moved rather rapidly through about 40° to a position where the manus was just posterior to the vertical. Cheliped extension movements were also executed, one or both limbs being moved forward at moderate speed until the mani were about 40° below the horizontal. The proximal segments of the cheliped were horizontal or a little higher when fully raised. Two types of ambulatory display-movements were seen. The more common was an upward, outward, straight up and down ambulatory raise movement, bringing the limb(s) almost to the horizontal. Although hori- zontally straight, the limb was curved posteriorly in the raised position. One, two or all four legs may be raised at the same time. The second ambulatory legs were moved up to 15° below the horizontal. The forward ambulatory movement was a rapid movement of a limb upward and forward, toward the other member of an interacting pair. A first or second ambulatory leg was moved diagonally up to 30° below the horizontal, down slightly and forward to about 45 ° anterior from the neutral ambulatory position and then back to the neutral position. The movement was smooth and approximated an oval in its path. A variation of the ambulatory raise movement was seen occasionally during prolonged interactions. The crab executed the upward motion of a raise, held the limb in the raised position for several seconds and from there moved the limb forward 30°-40°, lightly striking the other crab in the eye region. The limb was then moved back to the normal raised position and down. Shell fighting was observed on eight different occasions. These included fights in which an animal inhabiting a straight calcareous worm tube was the attacker and others in which it was the defender. After getting into an opposed position, the attacking crab carried out positioning movements, moving back and forth and from side to side in the pattern of a large V over the aperture of the defending crab. These movements were followed by diogenid type rapping movements (Hazlett, In Press), the attacker bringing its shell rapidly down into contact with the defending crab's shell while the attacker's ambulatory legs and defender's shell remained sta- tionary. A few times during raps the defender's shell was moved into contact with the attacker's but this did not resemble the spasmodic shaking characteristic of pagurid hermit crabs (Hazlett, In Press) in which the defender is moved back and forth rapidly while the attacker's shell remains stationary. When the defender's shell moved, it was either noticeably smaller than the attacker's or the attacker was in a worm tube. Although individuals of D. insignis dug in the sand with their ambula- tories and chelipeds, bringing particles toward their mouthparts, this activity was not as vigorous or continuous as in Dardanus venosus or 84 Bulletin of Marine Science [16(1) Petrochirus diogenes. Also unlike those species, no dislodging-shaking movements were executed when one crab crawled on the back of the shell of another. Family Paguridae Benthopagurus coked (Hay, 1917) (new combination) GERDAstations, G-462 (95 fms; 174 m): and G-482 (110 fms; 201 m). Two specimens observed. Wass (1963) erected the genus Benthopagurus and described two species in it, one of which, Benthopagurus schmitti, had been described by Hay (1917) as Pagurus coked (Provenzano, personal communication). This is a moderately large crab that moves about rather slowly when maintained at 150 C. Its walking movements and aggressive display move- ments were slower than those of any other pagurid observed. The crabs quite frequently came close to one another without any observable change in behavior. The cheliped presentation display brought the appendage forward until the manus was slightly back of the vertical, dactyls well off the substrate, as the animal raised its whole body slightly on its ambulatory legs. The cheliped extension display brought the whole appendage to an almost horizontal position at a moderate rate of speed. On a few occasions, while maintaining a sustained double cheliped extension, a crab rapidly moved both limbs medially as it lunged forward, striking the other crab near the eyes. Cheliped flicks occurred when one crab touched the major manus of another crab withdrawn into its shell or held the withdrawn crab in its ambulatory legs. These flicks by the withdrawn crab involved a short, moderately rapid movement of only the major manus forward and back 0 through about 30 • Ambulatory raise displays were executed which involved one or both first ambulatory legs. The limb was held rigid and straight as it moved rather slowly laterally upward to about 10° below the horizontal. A for- ward ambulatory movement was seen a few times but was not stereotyped in speed or pattern of movement. No dislodging-shaking behavior pattern was seen. A number of times one crab crawled over the other with no observable response; other times the crab that was crawled upon moved away as the other touched its shell, but no special behavior pattern was executed.

Pagurus rotundimanus Wass, 1963 GERDAstations, G-464 (202 fms; 369 m): G-465 (221 fms; 404 m): and G-467 (202 fms; 369 m). Three specimens observed. This rather small hermit crab resembles the shallow-water species, ] 966J Hazlett: Deep-water Hermit Crab Behavior 85 Pagurus bonairensis, in its general movements and aggressive displays (Hazlett, In Press). It moved about rather rapidly, and when walking, it often moved its chelipeds back and forth as if using them as accessory walking appendages. The cheliped presentation display was a moderately rapid movement, bringing the manus through 100° (major) or 60° (minor) to a position ]0 ° beyond the vertical. Only double cheliped presentations were seen but it is assumed that major and minor displays do occur individually. The cheliped extension movement rapidly brought the entire appendage to a horizontal position. The chelipeds were held very straight in the extended position and were very close to one another when viewed from above. Ambulatory movements were not as frequent as cheliped movements, but double and quadruple ambulatory raises (in which two and four legs were moved upward simultaneously) were executed during prolonged interactions. The appendages were rather rapidly brought to a position slightly below the horizontal. The limbs were not completely rigid during execution of the movement. When one crab crawled onto the back of another, the latter moved away rapidly, as it moved its body straight up and down in short rapid movements. These dislodging-shaking movements were similar to those of P. bonairensis. Pagurus politus (Smith, 1882) GERDAstations, G-464 (202 fms; 369 m) and G-467 (202 fms; 369 m). Three specimens observed. This large crab was very active at 15 ° C. It moved about rapidly, hold- ing its shell high off the substrate. When placed in an aquarium, specimens tended to avoid one another vigorously, retreating very rapidly when conspecific individuals approached. This avoidance was not as marked dur- ing "red-light" observation periods. No ambulatory display movements were observed but three types of cheliped movements were frequently seen during interactions. The cheli- peds, one at a time or together, were moved forward rapidly to a number of positions between vertical and horizontal. The extent of forward movement often seemed to be proportional to the relative intensity of the aggressive situation. However, three positions were assumed much more frequently and movement to these positions was more definite and smooth. The cheliped presentation display was a movement of the appendage through 45 °-50°, until the manus was just a little back of the vertical. At the same time, the animal raised upward on its ambulatory legs and the proximal segments of the ambulatories were moved outward slightly. The tips of the cheliped dactyls were well off the substrate in the presentation position. In the intermediate cheliped movement, the crab moved the mani out farther, 30°-35° beyond the vertical. On a number of occasions, the 86 Bulletin of Marine Science [16(1 ) simultaneous execution of a major cheliped presentation and an interme- diate movement of the minor cheliped was seen. In the cheliped extension, the manus of the appendage was moved to about 15° below the horizontal; with a double cheliped extension, the two appendages were held rather far apart, forming an angle of almost 110° when viewed from above. The chelipeds were often maintained in the extended position for some seconds; however, the downward motion could follow the upward without a notice- able pause. The downward motion that occurred after a sustained exten- sion was markedly slower than when little time was spent in the extended position. Crabs often moved their whole body forward rapidly a short distance while maintaining a cheliped display. A short lunge forward while maintaining a double extension was almost always followed by retreat of the other crab, although the latter frequently executed a double extension as it retreated. Another cheliped movement was seen when a crab was withdrawn into its shell, its major manus projecting from the aperture. These very short rapid cheliped flicks moved only the manus about 15°-20° out and back in. They were executed when another crab touched the manus of a with- drawn individual. No clear dislodging-shaking movements were seen but individuals of P. poUtus avoided one another so efficiently and retreated so quickly from the placement of even one ambulatory leg on their shell, that the proper situation for the execution of such movements was not observed. An unusual sequence of behaviors was seen on three occasions which appeared to be functionally similar to head flagging in gulls (Tinbergen, 1954). As one crab approached another, one of the two would "squat" down, lowering itself until its cephalothorax was almost in contact with the sand. The other crab then also lowered itself and the two quietly remained in this position, almost touching each other, for many seconds or even several minutes. On two occasions, one crab got up and walked away relatively slowly while the other crab remained in the lowered posi- tion. The other time, after about a minute of quiet proximity, both crabs got up at the same time and immediately executed double cheliped extensions and rapidly retreated from one another. Pylopagurus disco ida lis (A. Milne-Edwards, 1880) P1LLSBURYstation, P-198 (120-125 fms; 219-228 m). GERDAstation, G-334 (146 fms; 267 m). Five specimens observed. This small species was found living only in scaphopod shells. Inhabiting such straight tubes appears to have affected several behavior patterns. Although it moved about rather rapidly, it could not move directly back- wards as readily as many pagurid hermits. The pointed end of the scapho- pod shell sometimes became imbedded in the sand and halted backward movement. Perhaps as a result of this limited ability to move backwards, 1966] Hazlett: Deep-water Hermit Crab Behavior 87 individuals tended to duck into their shells during aggressive interactions more frequently than other pagurids. (This tendency was observed in two other, undescribed species of Pylopagurus that also inhabit scaphopod shells. ) As individuals of Pylopagurus discoida/is walk about, feed, etc. the major manus is at an oblique angle to the carpus. The latter is approxi- mately horizontal while the manus is 10° beyond the vertical. Thus the major cheliped is always in a "presentation" position. From this position, a cheliped extension was executed a number of times as two crabs came toge:ther. The minor cheliped was rapidly moved upward and forward, until the proximal segments were horizontal and the manus 15° below the horizontal. The proximal segments of the major cheliped were slightly above the horizontal and the manus about 30° below the horizontal in the extended position. A single ambulatory raise movement was seen during a few interactions. The limb was rapidly brought up to 20° below the horizontal and just as rapidly returned to the normal walking position. Shell fighting behavior was seen on two occasions. Apparently because of their scaphopod houses, the attacker did not get into the opposed position which all other marine species use. (Dardanus insignis combatants in straight worm tubes did get into an "opposed" position, although, when the defender was in a tube, the attacker seemed to have difficulty deter- mining from what position to carry out rapping movements.) The attacking crab, grasping the defending crab's shell just behind the aperture with its ambulatory legs and placing its major manus in the aperture (in light contact with the defending crab's manus), aligned itself parallel to and on top of the defender, facing the same direction as the defender. From this position, rapping was carried out. No positioning movements were distinguished. The rapping movements were the spasmodic shaking characteristics of the Paguridae, but the attacking crab was moved more than the defending crab (due to the former's superior position?). In short rapid movements, the whole body-shell of the attacker was moved up and down several millimeters above the defending crab. The defender was shaken by these movements, but little or no shell-to-shell contact occurred. Raps were carried out in series of 4-8 cycles of movement. After a number of such series, the defender vacated its shell and the two crabs exchanged shells. Often, when one crab crawled over another, anywhere along the length of its scaphopod shell, a series of rapid, side-to-side movements were executed by the crab crawled upon. This dislodging-shaking rarely threw the offending crab off physically, but elicited a marked increase in its locomotory movements. The dislodging movements were short, rocking movements, from side-to-side through about 40°, around the A-P axis of 88 Bulletin of Marine Science [16(1 ) the crab crawled upon, carried out either singly or just two cycles in sequence. Execution speed was about two cycles per second.

Parapagurus pictus (Smith, 1884) GERDAstations, G-482 (110 fms; 201 m): G-524 (281-390 fms; 513- 713 m): G-525 (220-170 fms; 403-311 m): and G-526 (161 fms; 294 m). Four specimens observed. This rather large hermit crab was very active at 150 C. Individuals moved about rapidly, carrying their shells far off the substrate. Like Pagurus paUtus, individuals of Parapagurus pictus tended to retreat rapidly from one another and often jumped completely off the sand as they moved back from one another. Cheliped presentation displays were frequently executed as two crabs came near each other. The crab raised up on its ambulatories and brought one or both chelipeds forward, the manus to the vertical, dactyls off the sand. The movement was rather rapid and moved the minor manus 0 0 through 45 and the major through 80 • Cheliped extension displays were frequently executed during interactions. The limb was brought forward and upward moderately rapidly, the proximal segments horizontal, the manus about 400 below the horizontal in the extended position. Cheliped flicks, as described for Pagurus paUllls, were executed by animals withdrawn in their shells. Two types of ambulatory movements were observed during aggressive interactions. A single ambulatory raise rapidly moved the limb straight up to 400 below the horizontal and back down. The limb was held rigidly but curved downwardly throughout the display. In the second movement, a forward ambulatory movement, the limb (one or both first ambulatories) was rapidly moved up diagonally to 400 below the horizontal and 200- 250 forward and then right back. This oval movement sometimes brought the limb in contact with the other crab. Dislodging-shaking movements were readily executed when one crab touched the back of another. As in other species, the whole body-shell of the crab was moved up and down in short, rapid movements.

Spirapagurus iris A. Milne-Edwards, 1880 PILLSBURYstation, P-198 (120-125 fms; 219-228 m). Fourteen speci- mens observed. This medium-small species was not very active at 100 C, but at 150 C moved about rapidly and continuously. Specimens often did not seem to be walking but rather half swimming, half running around the aquarium. The animal's shell is held high off the substrate when walking and, when rapidly retreating, an individual often would swim back for 5 or 6 em. The cheliped presentation and extension displays were similar to those 1966] Hazlett: Deep-water Hermit Crab Behavior 89 of Parapagurus pictus except that the speed of movement was even faster and in the major cheliped extension the proximal segments were slightly above the horizontal and the manus about 30 ° below the horizontal in the extended position. During some prolonged interactions, while one or both crabs were maintaining a double presentation or extension, a combatant rapidly moved its whole body forward several millimeters and then back in series of short, stereotyped lunges. Also during long encounters a variation of the cheliped presentation display was occasionally executed. While sustaining a cheliped presentation, and maintaining the proximal segments in a horizontal position, the dactyl was rapidly flicked back and forth through about 20°. Similar cheliped flicks were executed when a withdrawn animal was touched by another crab. Two types of ambulatory movements were observed. The ambulatory raise display (single, double or quadruple) rapidly moved the limb straight up to 15° below the horizontal and immediately back down. The forward ambulatory movement (single or double, first or second ambu- latories) in which the appendage was lifted upward only about 10° and moved forward about 30°, sometimes lightly touching the other crab. Strong dislodging-shaking movements were executed whenever a crab crawled on or touched the shell of another. The animal jumped up and down rapidly, twisting from left to right at the same time.

DISCUSSION In manner of execution and in the elicited behaviors of recipient crabs (retreat or the execution of similar or different displays), the movements described above appear to be aggressive displays (sensu Moynihan, 1960) by which individuals communicate to one another, altering one another's behavior without physical contact (see Hazlett & Bossert, 1965). Experi- ments with model presentations have shown that these positions of the chelipeds and ambulatory legs can act as visual stimuli in shallow-water species (Hazlett, In Press) and it is assumed they function in a similar manner in these species. However, this assumption leads to a second aspect to be considered about the behavior of these deep-water crabs. Can these movements function as visual displays at the depths at which these crabs were collected? And are there characteristics in the behavior of these crabs that could be associated with the fact that they live in an area of reduced light? Most of the species considered here were collected between 100 and 200 fms (183 and 366 m). Pagurus potitus was collected only near 200 fms, but Howe (1901) records P. politus from as shallow as 31 fms (55 m), and as deep as 640 fms (1170 m). According to light penetration data given by Clarke & Denton (1962), in clear tropical waters such as the waters these species were collected in, illumination of a level needed 90 Bulletin of Marine Science [16 (1) to visually detect objects is almost certainly present at 100 fms (183 m). The visual acuity of these at such light intensities may be questionable and at the lower depths at which some of these species are found, form vision is probably negligible. Clarke & Denton (ibid.) report measurable light from the surface at 950 m, well below the 390 fms (713 m) reported for Parapagurus pictus in this paper or the 360 fms (657 m) reported by Wass (1963) for Pagurus rotundimanus. But form vision or the detection of motion by surface transmitted light is very un- likely at such depths. However, in at least part of the depth ranges of these species, the functional exchange of visual displays seems possible. Two facts can be mentioned with respect to adaptions for social inter- action in reduced light intensity. A number of these species possess similar color patterns. Paguristes spinipes, P. moorei, Dardanus insignis, Pagurus poUtus and Pylopagurus discoidali.\' have a general pattern of red stripes or patches on a white background. In Paguristes spinipes, P. moorei, and a number of species not dealt with in this paper, the close similarity of color pattern seems to suggest a convergence toward a pattern which most advantageously utilizes the available light, perhaps in visually delineating the appendages used in aggressive displays. While observing these animals at night with a "red light" source, certain characteristics were observed in the interaction pattern of all species. The activity and sensitivity of the individuals of any species varies throughout the 24 hours. Most shallow-water species I have observed are nocturnal and tend to jump away from one another upon tactile contact more readily under red light conditions than during the day. This is true for both dioge- nid and pagurid species. These deep-water forms were generally active at night, under red light conditions. However, they tended to not jump away as readily and not avoid tactile contact with one another as much as during the day. Under reduced light conditions, they were not as anti-social. Orderly symbolic communications occurred at low light levels. The social reactivity of these species under reduced light conditions tended to be of the same level as that of shallow-water species under stronger illumination. Conver~ely, it could be argued that the strong avoidance of conspecific individuals shown by several pagurid species was an unnatural exagger- ation of behavior caused by the high light level present in the laboratory during the day. Another aspect of consideration of these data is their use in a compara- tive manner for phylogenetic purposes. The social behavior of diogenid and pagurid species is distinctly different in a number of ways (Hazlett, In Press; this paper; and MS) and adds another biological factor to the con- sideration of the two groups as distinct entities as is currently recognized by systematists (MacDonald, Pike, & Williamson, 1957; Pike & William- son, 1960). 1966] Hazlett: Deep-water Hermit Crab Behavior 91 Within the Diogenidae, the genera Paguristes, Clibanarius and show a number of similarities and are rather strongly different from Dardanus and Petrochirus. The latter genera, based upon observations of D. insignis, D. venosus and Petrochirus diogenes, behaviorally form a sub- group that shows a number of patterns similar to those of pagurid crabs. Within the genus Clibanarius, C. anomalus is behaviorally similar to C. vittatus and cubensis and somewhat different from C. antillensis and tricolor. The former sub-group shows closer relationship to the genus Paguristes (pattern of shell fighting, manner of execution of ambulatory raise display, sexual behavior) while the latter sub-group shows closer relationship to the genus Calcinus. The three species of Paguristes dealt with in this paper show no important divergence from the patterns shown by P. grayi (Hazlett, In Press), P. tortugae, P. anomalus, P. hummi and P. puncticeps (Hazlett, MS). The behavior of P. cadenati (Hazlett, In Press) is somewhat divergent from that of the other eight Paguristes species observed. The pagurid hermits differ behaviorally from the diogenids in (1 ) greater speed of general movement, (2) importance of cheliped displays, (3) manner of shell fighting, (4) pattern of sexual behavior, (5) having a distinct dislodging-shaking behavior, and (6) complexity of ambulatory display repertoire. Although items 3 and 4 were not seen for most of these deep-water hermits, it is possible to rank the pagurids observed according to how strongly they show these patterns characteristic of the Paguridae and thereby differ from the Diogenidae. Thus Benthopagurus cokeri, although very obviously pagurid in morphology, larval development (Provenzano & Hazlett, unpublished data), and behavior, did not show the patterns characteristic of pagurids as strongly as Pagurus rotundimanus or P. politus. Pylopagurus discoidalis and Parapagurus pictus show these patterns more strongly than most Pagurus species. (A tentative ranking of the Pagurus species I have observed is, from weakest to strongest expres- sion of pagurid characters, P. miamensis, pygmaeus, marshi, pollicarus, rotundimanus, bonairensis, longicarpus and politus.) Spiropagurus iris is the most "pagurid" species observed, in light of the data available; it differs from the diogenids more than other species. The above phylogenetic considerations do not differ in any important way from the systematics of the group based on other aspects of the species' biology. However, as data on more species becomes available, further clarification of the inter-relationships of the various groups will be possible.

SUMARIO COMPORTAMIENTO DE ALGUNOS CANGREJOS HERMITANOS (DECAPODA: PAGURIDAE) DE AGUAS PROFUNDAS DEL ESTRECHO DE LA FLORIDA Se recolectaron ejemplares de once especies de cangrejos hermitafios 92 Bulletin of Marine Science [16(1) (Paguridae y Diogenidae) en el Estrecho de la Florida, en operaciones de rastreo a profundidades de 60-390 brazas. Se las mantuvo en refrigerado- res a 10°, 15° Y 20°C, segun el area en que fueron recolectados. Se colo- caron juntos los individuos conespedficos y se observaron sus interacciones socia]es. Se describen los movimientos de demonstraciones agresivos de las patas ambu]atorias y los quelipedos, para cada especie, y se describe e] comportamiento de lucha par ]a concha en cuatro especies (Clibanarius anomalus, Paguristes moorei, Dardanus insignis y Pylopagurus discoidalis). Esta forma de comportamiento se encontr6 ser genera]mente similar a ]a de especies atines de aguas bajas. Se presentan a]gunas consideraciones filo- geneticas basadas en ]a comparaci6n del comportamiento de las especies. Se ordenan catorce especies de Paguridae, de diferentes profundidades y areas de acuerdo con el grado en que ditieren en su comportamiento del caracteristico de Diogenidae.

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