Shell Utilization by the Hermit Crabs <I>Diogenes Pugilator</I> (Roux

BULLETIN OF MARINE SCIENCE, 65(2): 391–405, 1999

SHELL UTILIZATION BY THE HERMIT CRABS DIOGENES PUGILATOR (ROUX, 1829), PAGURISTES EREMITA (LINNAEUS, 1767) AND PAGURUS FORBESII BELL, 1845 (CRUSTACEA: DECAPODA: ANOMURA), IN A SHALLOW-WATER COMMUNITY FROM SOUTHERN SPAIN

M. E. Manjón-Cabeza and J. E. García Raso

ABSTRACT Gastropod shells used by the three dominant hermit crabs, Diogenes pugilator (Roux, 1829), Paguristes eremita (Linnaeus, 1767), and Pagurus forbesii Bell, 1845, of the detritic littoral bottoms from Barbate Bay (Cadiz, Spain) were analyzed. The study showed that these hermit crabs species have different patterns of gastropod shell use. Paguristes eremita, the largest and strongest species, inhabits heavier gastropod shell species with wider aperture (belonging to the Muricidae family), while, Diogenes pugilator and Pagurus forbesii, inhabit smaller and lighter shells (mainly those belonging to the family Turridae). Diogenes pugilator, despite being clearly the more abundant species, does not use the most abundant species of the gastropod community (Turritella turbona), which instead is used by Pagurus forbesii. However, no morphological relationships between these hermit crabs and the diameter of shell aperture have been found, either in relation with the whole gastropod shells used or in relation with the more specifically used shells. On the other hand, specimens of D. pugilator with cephalothoracic shield widths larger than the shell aperture have been found, however, this result has not been found in P. forbesii or in Paguristes eremita. Also, in these three species no differences in shell use by sexes exist. These and other data indicate that D. pugilator does not make a strong shell selection, perhaps in part, due to a competition with P. forbesii and a scarcity of available useful shells in the area, which are a fundamental limiting factor. On the contrary, P. eremita seems to use adequate shells, a point that allows us to speculate that this species makes (with or without competition with the other hermit crabs) a real selection. Finally, the data about relative growth of the cheliped of D. pugilator in different areas, in which they use different shells, are similar. These data contrasts with the stunting hypothesis.

Studies related to the utilization of gastropod shells by hermit crab populations have been based on direct observation in natural conditions (Bertness, 1980, 1981a, 1982; Blackstone, 1986a, 1989; Gherardi and Vannini, 1989; Lancaster, 1990; Pessani et al., 1990; Gherardi, 1991; Pessani and Premoli, 1993) or through laboratory studies (McLay, 1985; Walters and Griffiths, 1987; Lively, 1988; Lowery and Nelson, 1988; Hazlett, 1989, 1990,1992; Bertness, 1981b; Asakura, 1992). Direct observations are basically made on intertidal species and they permit the de- scriptions of interspecific and intraspecific competition for the available gastropod shells in this environment. On the other hand, laboratory experiments are only partially useful to learn the relationships among the species and their surroundings. Gastropod shell utilization by different species of hermit crabs in natural intertidal habitat studies are scarce because there are many difficulties and factors without control; however, they allow us to know more about the real behavior of the species in their natural habitats and the reactions to different conditions (Bach, et al., 1976; Gherardi, 1991; Gherardi and Vannini, 1989; Lowery and Nelson, 1988).

391 392 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 2, 1999

The authors tried to analyze how the allometry between the chelipeds and cephalothorax shield length can be altered if an individual of a hermit crab species uses a particular shell over a period of time (Wilber, 1990). There are two potential explanations that have made in some interesting papers which will allow us to discuss it. First, “the molding hypothesis” suggests hermit crabs may conform to the shape of the shell aperture when their exoskeleton is malleable during the postmolt period (Golsdschmidt, 1940; Wolff, 1961). The second hypothesis, “stunting hypothesis”, states that hermit crabs whose overall growth is stunted from occuping poorly fitting shells (Markham, 1968; Fotheringham, 1976a,b; Bertness, 1981a,c) acquire relatively large chelipeds. This paper seeks to describe and analyze the utilization of the shells inhabited by the dominant species of hermit crabs of shallow detritic bottoms in relation to the living community in the study area. Furthermore, it tries to explain the adaptation of the hermit crabs in the gastropod shells, the influence of this fitness and in aspects such as inter- and intra-specific competition and the utilization of the largest cheliped as a cover of the shell aperture.

MATERIAL AND METHODS

The study area. (Fig. 1) is located in Barbate Bay, province of Cadiz, in the neighborhood of the Straits of Gibraltar, between 36°08.73'–36°09.71'N and 05°55.19'–05°53.59'W. The analyzed benthos are situated between 15 and 24 m deep and we selected for sampling two transects separated by 2.5 km, one in front of the village of Barbate (B) and the other one further east, in front of Retín (R), taking in each one two samples at 15–18 m (B1, R1) and at 24 m (B2, R2), respectively. Samples were taken from October 1993 to December 1994. For sampling, a small heavy dredge similar to a rock-dredge, with a rectangular frame of 42 × 22 cm, and a double net were used; the inside mesh size was 4.5 mm. In the laboratory, sediment was washed over a sieve column with a mesh size between 1 cm and 1 mm. The fauna were separated, and the hermit crabs and their gastropod shells were identified based on the works of Zariquiey Álvarez, 1968; Ingle, 1993; Sabelli et al., 1990, 1992a,b; Pope and Goto, 1991. The sediment is mostly detritic composed of coarse sand, fine gravel and Amphioxus sand, under bottom currents, with abundant bioclastic remains (bivalve and gastropod shells). The tidal currents locally increased by the existence of flagstones that guided them, and the main one by the proximity of Punta del Tajo and Trafalgar Cape. For relative growth, the anatomical structures were analyzed with a VID V computer program that processed stereoscopic microscope images taken by a video camera, with a measurement error of 0.001 mm. Four dimensions were measured: cephalothoracic shield length (SL): maximum length, from rostrum to posterior midpoint of shield; cephalothoracic shield width (SW): maximum width; cheliped length (CHL): from the distal part of propodal prolongation to the basal part of propodus; and cheliped width (CHW): maximum propodal width. The maximum diameter of the gastropod shell aperture (SAW) was measured with a caliper (measurement error: ± 0.05 mm). To determine the relationships between morphological parameters of hermit crabs species and gastropod shell aperture widths, the correlation coefficients were computed. Kendall (t) or Pearson (r) was applied depending on whether the parameters showed a non-normal or normal distribution following the significance of the Kolmogorov-Smirnoff test. MANJÓN-CABEZA AND GARCÍA RASO: SHELL UTILIZATION BY HERMIT CRABS FROM SOUTHERN SPAIN 393

Figure 1. Location of the study area showing sampling stations (R1, B1, R2 and B2).

Additionally, simple (linear, logarithmic, quadratic, potential and exponential) and multiple regression analyses were carried out on shells used, and on dominant gastropod shell species use by hermit crabs: D. pugilator, P. eremita and P. forbesii. Since the abundance of D. pugilator was large, it was possible to analyze shell-utilization by sex. For this, a χ2 test (Siegel, 1972) was applied. Also, on the principally used shells, a percentage comparison test was carried out (Lamotte, 1988) between sexes and between ovigerous and non- ovigerous females.

RESULTS

In the study area, 42 species of living gastropods were found (the pateliform species, such as Calyptraea chinensis Linnaeus, 1758, were excluded from the study). The species 394 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 2, 1999

Figure 2. Composition of living gastropod community in Barbate Bay. MANJÓN-CABEZA AND GARCÍA RASO: SHELL UTILIZATION BY HERMIT CRABS FROM SOUTHERN SPAIN 395

distribution in the study area revealed the dominance of T. turbona Monterosato, 1877, Gibbula magus Linnaeus, 1758 and Mesalia varia (Kiener, 1887) (Fig. 2). DIOGENES PUGILATOR.—D. pugilator occupied shells of 27 gastropod species (Fig. 3); shells of the remaining 15 species were of very small sizes and they only represented 11.59% of the total number of living specimens of the gastropod community. Also, there were occupied shell of other eight species imported from elsewhere, but they only represented 4.68% of the total shells species used. Other mollusk shells occupied by D. pugilator were two species of Scaphopoda (Den- talium novemcostatum Dautzenberg, 1891 and Dentalium vulgare Da Costa, 1778), but with a very small occupation percentage (Table 1). The utilization of Dentalium shells has been documented elsewhere. An uncommon finding was the 0.1% use of Polychaeta tubes. We have found this kind of occupation in other samples but were not included in this study. The shell species used by D. pugilator (Fig. 3) in the area were Mesalia varia, followed by Turritella communis Risso, 1826, Nassarius reticulatus (Linnaeus, 1758), Nassarius mutabilis (Linnaeus, 1758), T. turbona and G. magus, which represented 76.35% of the shells used by this hermit crab. These species were dominant in the living gastropod community, but in a different order (Fig. 2). Of gastropod families, Turritellidae species were used by D. pugilator (54.56%) followed by Muricidae (28.89%) (the same sequence as in the living gastropod community). D. pugilator showed a clear preference for Naticidae species over Trochidae, even though the latter family was more abundant in the living gastropod community. A general analysis of the use of shells (all species) by males and females shows that there was no significant difference (test χ2 at 99.95% of confidence level); both sexes have the same pattern of shell-use but, significantly different percentages were found in G. magus and Polynices guillemini (Payrandeau, 1826) (Table 1). However these two species only represented 8.25% of total shell used by D. pugilator. In addition, ovigerous females chose within a smaller range of species than non ovigerous females and clearly prefered M. varia (Table 1). The relationships between the maximum diameter of the shell aperture, cheliped length and cephalothoracic shield width have been analyzed to determine whether they are key factors in the use of gastropod shells. The percentage of D. pugilator with a cheliped length greater than shell aperture width was 54.41% and smaller 45.59%, which were not statistically different. In contrast, 15.78% of specimens of D. pugilator, in the study population, had a cephalothoracic shield width greater than the diameter of the shell aperture. Before trying to construct a model that explains the relationships among the parameters chosen (SL, SW, CHL, CHW) and the diameter of shell aperture (SAW), in the whole shell gastropod community, the correlation coefficients were computed and these were statistically significant; but the correlation values of the different relationships were very low, never higher than 0.5 (Table 2). The coefficient of determination values found were lower than 0.3 (Table 3), which indicated that not one of these single variables totally determined the gastropod shell uses of D. pugilator (in accordance with the size of the shell aperture). Multiple regression analyses were then used to test whether gastropod shell use could be due to more than one variable. The results (Table 4) are similar but there were large unexplained variances. In addition, a similar analysis was made on the species of gastropod shells used by D. pugilator (M. varia, T communis, N. reticulatus, N. mutabilis, T. 396 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 2, 1999

Figure 3. Gastropod shells used by Diogenes pugilator in Barbate Bay. MANJÓN-CABEZA AND GARCÍA RASO: SHELL UTILIZATION BY HERMIT CRABS FROM SOUTHERN SPAIN 397

Table 1. Percentages of shells occupation by males (M) and females (F): no ovigerous (Nof) and ovigerous (Of) of Diogenes pugilator. * significantly different at 99.95%.

GMastropod %F%f%fO %No Mesalia varia (2Kiener, 1887) 288.4 364.7 1*2.0 24.21 Turritella communis R0isso, 1826 126.0 145.4 47.7 11.3 Nassarius reticulatus (3Linnaeus, 1758) 110.5 77.5 28.1 5.6 Nassarius mutabilis (5Linnaeus, 1758) 91.0 79.9 16.1 7.1 Turritella turbona M6onterosato, 1877 50.2 87.5 21.7 6.1 Gibbula magus L3innaeus, 1758 6*.5 20.77 04.2 2.7 Polynices guillemini (5Payrandeau, 1826) 5*.0 29.37 09.5 1.8 Polynices macilenta (8Philippi, 1844) 35.5 30.7 08.4 3.5 Nassarius pygmaeus (3Lamark, 1822) 25.5 39.7 05.9 2.9 Nassarius incrassatus (2Stöm, 1768) 27.3 29.3 08.7 1.6 Nassarius elatus (1Gould, 1846) 27.1 29.1 07.7 1.4 Polynices alderi (5Forbes, 1938) 17.0 20.3 02.2 2.3 Bolinus brandaris (8Linnaeus, 1758) 19.6 04.7 0.8 Aporrhais pespelecani (3Linnaeus, 1758) 00.6 02.4 0.4 Calliostoma s1p. 09.2 1 04.7 0.8 Dentalium novemcostatum D3autzenberg, 1891 00.6 02.4 0.4 Ocenebra erinacea (3Linnaeus, 1758) 00.6 01.2 0.2 Ocenebrina aciculata (2Lamark, 1822) 00.4 02.4 0.4 Dentalium vulgare d1a Costa, 1778 00.2 02.4 0.4 Jujubinus dispar C2urini Galetti, 1982 00.4 00.2 0.2 Nassarius vaucheri (0Pallary, 1906) 09.0 00.5 02.2 0.4 Trophon muricatus (1Montagu, 1803) 00.2 02.4 0.4 Mangelia attenuata (2Montagu, 1803) 0.4 Fusinus rostratus (2Olivi, 1792) 0.4 Nassarius heynemanni (0Von Maltzan, 1884) 00.0 00.4 01.2 0.2 Natica hebraea (0Martyn, 1786) 00.0 00.4 01.2 0.2 Ocenebrina edwarsi (1Payraudeau, 1826) 00.2 00.2 0.2 Bela laevigata (1Philippi, 1836) 0.2 Cancellaria cancellata (1Linneaeus, 1767) 0.2 Cerithium vulgatum B0ruguiè re, 1792 00.0 01.2 0.2 Fusinus pulchellus (1Philippi, 1844) 0.2 Gibbula fanulum (1Gmelin, 1791) 0.2 Gibbula guttadauri (1Philippi, 1836) 0.2 Hexaplex trunculus (0Linnaeus, 1758) 00.0 01.2 0.2 Muricopsis cristata (0Brocchi, 1814) 00.0 01.2 0.2 Polynices catena (1da Costa, 1778) 0.2 T0ubes of Polychaeta 00.0 01.2 0.2 Turbonilla rufa (1Philippi, 1836) 0.2 1000 100 100 10 turbona and G. magus) in relation to the studied parameters of the hermit crab, but the coefficient of determination values were not statistically significant. PAGURUS FORBESII.—Turritella turbona is the gastropod species used most frequently by P. forbesii, followed by N. reticulatus (Fig. 4). Both species are very abundant in the living gastropod community and they have shell apertures wider than M. varia or T. communis (species used more by the dominant hermit crab D. pugilator). 398 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 2, 1999

Table 2. Diogenes pugilator. Results of Kolmogorof-Smirnoff Test (K-S), Pearson and Kendall coefficients. (CHL: cheliped length; CHW: cheliped width; F: females, SAW: maximum diameter of the shell aperture (whole gastropod used), SL: cephalothoracic shield length; M: males, Nof: no ovigerous females, Of: ovigerous females, SW: cephalothoracic shield width).

K-S P(0.01) MFOf fNlo Al SAW Nlot normal Nlot norma Nlorma Nlot norma Not norma LS Nlormal Nlorma Nlorma Nlot norma Norma SW Nlot normal Nlorma Nlorma Nlorma Not norma CHL Nlot normal Nlorma Nlorma Nlorma Not norma CHW Nlormal Nlot norma Nlorma Nlorma Norma r (Pearson) P < 0.01 MFOf fNlo Al SL-SAW 09.48 00.3 05.3 0.4 SW-SAW 01.42 06.3 0.4 CHL-SAW 08.42 01.4 0.5 CHW-SAW 01.46 01.3 07.5 0.4

τ (Kendall) P < 0.01 MFOf fNlo Al SL-SAW 01.24 0.3 SW-SAW 05.37 04.2 0.3 CHL-SAW 01.38 06.3 0.3 CHW-SAW 06.33 0.2 The results of the correlation and regression analyses are given in Table 5, in which only the significant linear patterns are indicated. The correlation values were not significant or they were very low. The coefficient of determination showed that the analyzed parameters explained only about the 50% of the variance. PAGURISTES EREMITA.—The other species, P. eremita, most frequently used Bolinus brandaris (Linnaeus, 1758) and Hexaplex trunculus (Linnaeus, 1758) (Fig. 5). Also, the species: Buccinulum corneum (Linnaeus, 1797), Bolma rugosa (Linnaeus, 1767) and Cymbium olla (Linnaeus, 1858) are used exclusively in relation to the other hermit crabs of the area. In Table 6, the results of the correlation and regression analyses are given. The highest correlation values were found in shell species used by P. eremita. In the regression analysis only the patterns that were significant are indicated. The shell aperture diameter showed a significant relationship with the studied variables only when a quadratic regression was applied. The analysis of the data on the apertures of gastropod shells species used by P. eremita (Bolinus brandaris, Haxaplex trunculus and Ocenebra erinacea), in relation to the studied parameters of the hermit crab, showed that all determination coefficient values were highly significant (Table 7).

DISCUSSION

In the study area, the three hermit crabs species analyzed show different patterns of gastropod shell utilization. P. eremita, the largest and strongest species of hermit crab studied, inhabits heavier gastropod shells of species with wide apertures such as Bolinus MANJÓN-CABEZA AND GARCÍA RASO: SHELL UTILIZATION BY HERMIT CRABS FROM SOUTHERN SPAIN 399

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O4 MANJÓN-CABEZA AND GARCÍA RASO: SHELL UTILIZATION BY HERMIT CRABS FROM SOUTHERN SPAIN 401

Figure 4. Gastropod shells used by Pagurus forbesii in Barbate Bay.

brandaris and Hexaplex trunculus (the largest species of Muricidae family in the area). Even small specimens use heavy shells, such as Cymbium olla or Cerithium vulgatum. In contrast, the other two hermit crab species, D. pugilator and P. forbesii inhabit smaller and lighter shells, mainly those belonging to the family Turridae (T. communis, T. turbona, and M. varia) and Nasaridae (N. reticulatus). Species of the Turridae family are also used

Figure 5. Gastropod shells used by Paguristes eremita in Barbate Bay. 402 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 2, 1999

Table 5. Pagurus forbesii. Results of Kolmogorof-Smirnoff Test (K-S), Pearson and Kendall coefficients and simple and multiple regression analysis between the maximum diameter of the shell aperture (all gastropod) (SAW) and the morphological parameters studied (CHL: cheliped length; CHW: cheliped width; SL: cephalothoracic shield length; SW: cephalothoracic shield width).

K-S P (0.01) τ (<1Kendall) P 0.0 SAW NWot normal S7L-SA 0.3 LS NWot normal S0W-SA 0.2 SW NWormal C7HL-SA 0.3 CHL NWormal C5HW-SA 0.5 CHW Not normal Simple regression S8L yr(SAW) = 0.17x + 2.0 2 =10.59 P < 0.000 C3HL yr(SAW) = 0.28x + 2.3 2 =10.55 P < 0.000 Multiple regression SWAW = 3.53SL + 0.48S − 5r.81 2 =20.58 P < 0.00 SLAW = 4.08S − 2.30SW + 1.20CHL − 3r.56 2 =20.62 P < 0.00

by other species of the genus Diogenes, such as Diogenes brevirostris Stimpson, 1858 (Walters and Griffith, 1987). The use of the same species of shells by these two species might indicate the existence of a competition between them. In fact, both have similar medium body sizes, which is a point to take in account (Bertness, 1981c; Gilchrist and Abele, 1984). Also, D. pugilator individuals, in spite of being clearly the more abundant species (Manjón-Cabeza and García Raso, 1998), does not use the most abundant species of shell from the gastropod community (T. turbona), which is used by P. forbesii. However, no morphological rela-

Table 6. Paguristes eremita. Results of Kolmogorof-Smirnoff Test (K-S), Pearson and Kendall coefficients and simple and multiple regression analysis between the maximum diameter of the shell aperture (all gastropod) (SAW) and the morphological parameters studied (CHL: cheliped length; CHW: cheliped width; SL: cephalothoracic shield length; SW: cephalothoracic shield width).

KP-S P(0.01) t (Kendall) < 0.01 SlAW NWot Norma S7L-SA 0.7 LlS NWot Norma S8W-SA 0.7 SlW NWot Norma C7HL-SA 0.5 ClHL NWorma C3HW-SA 0.6 ClHW Not Norma

Simple regression S)L y (SAW = 0.02x2 − 0.22x + 5r.72 2 = 0P.81 < 0.0001 S)W y (SAW = 0.02x2 − 0.18x + 4r.17 2 = 0P.84 < 0.0001 C)HL y (SAW = 0.03x2 − 0.36x + 5r.72 2 = 0P.88 < 0.0001 C)HW y (SAW = 0.02x2 − 0.18x + 3r.57 2 = 0P.83 < 0.0001

Multiple regression SLAW = 0.20S + 2.71SW − 2r.21 2 =P0.72 < 0.00001 SLAW = 0.41S + 1.48SW − 0r.80CHL -2.32 2 =P0.73 < 0.00001 SLAW = 0.57S + 0.83SW − 0.50CHL + 0r.84CHW - 1.99 2 =P0.73 < 0.00001 MANJÓN-CABEZA AND GARCÍA RASO: SHELL UTILIZATION BY HERMIT CRABS FROM SOUTHERN SPAIN 403

Table 7. Paguristes eremita. Determination coefficient values of the simple regression analysis between the maximum diameter of the shell aperture (SAW) of the more used gastropod and the morphological parameters studied (CHL: cheliped length; CHW: cheliped width; SL: cephalothoracic shield length; SW: cephalothoracic shield width).

Hsexaplex trunculus Baolinus brandari Ocenebra erinace ScAW Qruadrati Lcinea Qruadrati Lcinea Qruadrati Linea SrL 2 = 0r.87 2 = 0r.87 2 = 0r.87 2 = 0r.80 2 = 0r.99 2 = 0.99 P < 0P.06 < 0P.0007 < 0P.06 < 0P.0005 < 0P.005 < 0.0002 SrW 2 = 0r.90 2 = 0r.90 2 = 0r.96 2 = 0r.71 2 = 0r.98 2 = 0.98 P < 0P.03 < 0P.0003 < 0P.0001 < 0P.0021 < 0P.019 < 0.0011 CrHL 2 = 0r.96 2 = 0r.93 2 = 0r.90 2 = 0r.16 2 = 0r.91 2 = 0.91 P < 0P.001 < 0.0001 P < 0P.003 < 0.1000 P < 0P.088 < 0.0116 CrHW 2 = 0r.94 2 = 0r.94 2 = 0r.94 2 = 0r.34 2 = 0r.96 2 = 0.96 P < 0P.01 < 0P.0001 < 0P.001 < 0P.0100 < 0P.039 < 0.0036 tionships between these hermit crabs and shell aperture were found, neither in relation with the whole gastropod community nor in relation with the more used shells. In addition, the known information on the use of gastropod shells species in the Span- ish littoral by D. pugilator reveals differences. For example in Málaga Bay it uses N. mutabilis (Linnaeus, 1758) and Cancellaria cancellata (Linnaeus, 1767) (García Raso unpubl. data), and in the Alicante littoral N. mutabilis, N. reticulatus and N. incrassatus (Stroem, 1768) (Guillén Nieto, 1993). These data indicate that D. pugilator does not present a strong selection of shells (al- though it apparently prefers Turridae shells), perhaps in part because of competition with P. forbesii. This proposition might be supported, even more, if it realized that there are specimens of D. pugilator with a cephalothoracic shield width greater than the diameter of the aperture of shell, but not in P. forbesii. It also indicates a scarcity of available useful shells, in good conditions, in the area. The fact that these species have not shown a good body fit with the shell aperture means that: (1) the hermit crab could be exposed to losing the brood (Bach et al, 1976), (2) tend to brood a reduced number of smaller eggs (Fotheringham, 1976, 1980, Bertness, 1981c), (3) to be consumed (Vance, 1972), or (4) even to show slower growth rates (Markham, 1968; Fotheringham, 1976; Bertness, 1981a,c). On the contrary, P. eremita seems to use adequate shells suggesting that this species may (with or without competition with the other hermit crabs) represent a real selection. Finally, it should be pointed out that the known data about relative growth of the cheliped (relationships between cheliped length and cephalothoracic shield length) of the studied population of D. pugilator (Manjón-Cabeza and García Raso, in press), which present a poor body fit in relation to the shell aperture, are slightly different to another from a population from Alicante, which use larger and different shells (Guillen Nieto, 1997). This could support the stunting hypothesis according to which variations in allom- etric relationships between the chelipeds and cephalothorax can be affected by the size of shell occupied (Markham, 1968; Fotheringham, 1976; Bertness, 1981a,c; Blackstone, 1985, 1986a,b). Nevertheless, both results are very close and, also, the sampling and measurement methods and the population structure were different. These results suggest that the opinion of Wilber (1990), obtained from natural populations, can not be totally rejected. 404 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 2, 1999

ACKNOWLEDGMENTS

This research is included within the Project PB92-0415. “Comunidades bentónicas del litoral de Cádiz. Estructura y dinámica de las taxocenosis de crustáceos decápodos, moluscos y algas. Biología de las especies dominantes”, supported by the Spanish M.E.C, DGICYT funds. We must give thanks to S. Gofas (Muséum national d’Histoire naturelle, Paris) for his interesting opinions and helping shell identification.

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DATE SUBMITTED: February 16, 1998. DATE ACCEPTED: August 1, 1998.

ADDRESS: Departamento de Biología Animal, Universidad de Málaga, Campus de Teatinos s/n. 29071 Málaga, Spain. Tel: 34-5-2131857, Fax: 34-5-2132000, e-mail: .

Shell Utilization by the Hermit Crabs &lt;I&gt;Diogenes Pugilator&lt;/I&gt; (Roux

Shell Utilization by the Hermit Crabs <I>Diogenes Pugilator</I> (Roux