BIOLOGICAL INVESTIGATIONS OF THE DEEP SEA. 34. A NEW HOST AND AN EXTENSION OF RANGE FOR THE COMMENSAL CRAB, MINYOCERUS ANGUSTUS (DANA, 1852) (CRUSTACEA: PORCELLANIDAE)l

ROBERT H. GORE AND JOHN B. SHOUP Institute of Marine Sciences, University of Miami

ABSTRACT Minyocerus angustus, a porcellanid crab commensal on the sea star, clathrata (Say), is here reported occurring on a new host, the nine- armed sea star, (Lamarck). Specimens of the crabs are compared with descriptions given in the literature. The color of the crab in life and observations of its habit are described. The known range for M. angustus is extended from Isla Cubagua, Venezuela, 1300 miles (ca. 2000 km) north and west to Trujillo Harbor, Honduras.

INTRODUCTION Members of the porcellanid genus Minyocerus live commensally on sea stars of the genus Luidia (Glassell, 1938; Haig, 1956). The occurrence of the western American Minyocerus kirki on the serpent stars Amphipholis platydisca, Ophiothrix spiculata, and Ophiolepis grisea, as well as on Luidia columbia, L. phragma, and L. foliolata, has been noted by Haig (1960) in her work on eastern Pacific Porcellanidae. The eastern American species, M. angustus, has until now been found only on (Haig, 1956, 1962). Minyocerus angustus has been previously reported from Brazil (Haig. 1956, 1962, 1966), Venezuela (Haig, 1956), Surinam (Holthuis, 1959), and Limon Bay, Panama (Boone, 1930). Haig (1956) considered Boone's Porcellana rosamondae from Panama as probably identical with Minyo- cerus angustus but left the Panama record in question at that time. The present paper is a report of 6 specimens of Minyocerus angustus which were found living commensally on a new host, the nine-armed sea star Luidia senegalensis (Lamarck). Observations of the crab on its host are noted. In addition, a northwestern extension of the range for this crab is reported. We wish to thank Drs. Anthony J. Provenzano, Jr., Lowell P. Thomas, and Donald R. Moore, all of whom critically read the manuscript and made many helpful suggestions. Our thanks are also extended to Mr. Jerald A. Halpern who confirmed our identification of Luidia senegalensis.

1Contribution No. 870 from the Institute of Marine Sciences, University of Miami. This work was supported in part by Research Grant No. GN-l1244 from the Institute of General Medical Science. U. S. Department of Health, Education and Welfare; National Geographic Society-University of Miami Deep Sea Biological Program; and National Science Foundation Grant No. GB-3BOBin support of ship time. 1968] Gore & Shoup: Commensal Crab, Minyocerus angustus 241

COLLECTION DATA Two pairs of crabs, a large male and large female, and a small male and female, were found living on a single Luidia senegalensis (UMML 40. 182). The sea star, which measured 20 em from arm tip to center of disc, was collected by one of us (JBS) on 21 July, 1966, in 3 m of water in the harbor of Trujillo, Honduras, during a diving trip. The crabs were seen on the ventral surface of the sea star when it was excavated from the bottom of the harbor. The third pair of crabs was collected from a 15-cm (arm tip to center of disc) Luidia senegalensis (UMML 40.181) while the first author was participating on a cruise of the Institute of Marine Sciences' research vessel, JOHN ELLIOT PILLSBURY. These crabs were taken in a 10-foot otter trawl in 24 m of water, just offshore and west of Colon, Panama~ This location is only 15 km west of Limon Bay, Panama. It would confirm Boone's record of location if her species is indeed M. angustus as Haig (1956, 1966) suggested.

Genus Minyocerus Stimpson, 1858 Minyocerus angustus (Dana), 1852 For previous records and synonymy, see Haig, 1956: 30; 1960: 193; 1962: 184; 1966: 354. All measurements refer to carapace length obtained with an ocular micrometer.

Material Examined.-l ~, 5.3 mm; 1 lj>, 5.0 mm, ovigerous; commensal on Luidia senegalensis. Cruise P 6608, Station P-432, 9° 18.2N, 80° 03.3'W, 20 July, 1966; 24 meters; UMML 32.3357. 1 ~, 5.6 mm; 1 'i?, 5.6 mm, non-ovigerous; 1 i5, 2.77 mm; 1 'i?, 2.3 mm, non-ovigerous, all commensal on Luidia senegalensis. Trujillo Har- bor, Honduras, sand bottom, 21 July, 1966; 3 meters. Collected by John B. Shoup. UMML 32.3358. Remarks.-The specimens from Honduras and Panama are similar to each other. All have 3 frontal teeth, the median tooth being equal or very slightly longer than its neighbors. Rathbun's specimen (1900) was two- toothed frontally, the left tooth being much shorter than the right and with only a shallow lobe where the median tooth should be. Rathbun (loc. cit.) thought it possible that both median and left tooth had been broken prior to the last molt in her specimen and had not been renewed. Haig's (1956) specimens agreed with Dana's (1852) description and with Rathbun's specimen. Our specimens agree with both Dana's and Rathbun's descrip- tion, but do not completely agree with Boone's description. In Boone's specimens the carapace is wider posteriorly than anteriorly, and the median 242 Bulletin of Marine Science [18(1)

....: ]968] Gore & Shoup: Commensal Crab, Minyocerus angustus 243 frontal tooth is shorter relative to the two pre-orbital teeth. In her figure (I930, plate 21) she depicted two suprahepatic spines directly behind the eyes. We consider these to represent the left and right postorbital teeth respectively, which occur in all of our specimens and are located above the eyes but in the same plane of curvature as the median and pre-orbital teeth (Figs. 1 and 2). If the spines pictured by Boone are truly supra- hepatic, there is no mention of it in her description. As Haig (I 956) pointed out, the differences in width of carapace and lack of median frontal tooth are the only characters which separate Porcellana rosamondae from Minyocerus angustus. Thus, we concur with her suggestion that Boone's P. rosamondae is the same species as Minyocerus angustus. Haig, in a later paper (1966) classified P. rosamondae in the synonymy of M. angustus. Our specimens differ from all descriptions in one minor respect. The merus of the cheliped in both our Honduran and Panamanian crabs not only has a spine on the inner, upper, distal angle, but all of our specimens have a smaller, second spine or series of spinules on the dorsomedial margin of the merus (Figs. 1 and 2, A-B). The presence in our adult specimens of three more-or-less-equal spines located distally on the inner lateral margin of the carpus is apparently within the range of variation allowed for this species (Haig, ]960: 196). In our specimens, the outer surface of the chelipeds, the fingers, and the inner surface of the carpus were liberally covered with hair. The remaining appendages and the abdominal segments were less densely pubescent. The carapace is lightly covered with setae, especially the anterior, lateral, and posterior margins. This pubescence, while perhaps implied by other authors, was mentioned in earlier description only by Dana. Only minor variation was observed in color patterns (see Figs. 1, 2, and 3). The female from Panama molted aboard ship on July 21, and died on July 26. Both the molt and dead female were preserved in 70 per cent ethanol on board ship. The molt was later transferred to 10 per cent non-buffered formalin when the specimens reached the Institute. The preserved female (Fig. 2, B) has lost most of the reticulate pattern, becoming pale pinkish-tan with diffuse orange on both hepatic regions. The molt (Fig. 3, A), however, retains the reticulation which is similar to that seen in all other specimens examined. The color of the preserved molt which, as might be expected, differs from the color seen in life, is the same as described by Rathbun (loc. cit.) for the she examined. Presumably she was looking at alcohol- or formalin-preserved specimens. Haig's animals had only "a faint trace of color (remaining)," and these were also preserved specimens. Thus, while the true color may be lost, the reticulate pattern, for the most part, remains for some time. 244 Bulletin of Marine Science [18 (1) L968] Gore & Shoup: Commensal Crab, Minyocerus angustus 245

Color in Life.-The following color notes were made on the living crabs collected from Panama. The live crabs were strikingly colored. The overall hue was an ochreous yellow-grey with dark brown reticulations on the dorsal surface of the carapace, chelipeds, and walking legs. On both the chelipeds and walking legs, the dark brown reticulation ( = "marbling," [Rathbun, lac. cit.]) was more irregular, being less distinct than that on the carapace. The dactyls were a lighter, translucent grey. The antennules were a brilliant blue with bright yellow flagella. The extremely extensible eyestalks were the same ochreous yellow-grey. Chelae were a more or less uniform grey, less translucent than the dactyls of the walking legs. Examination under the microscope showed that the major reticulate pattern was further broken up into smaller, thinner, and less distinct reticulations over the entire dorsal area of the carapace. In the figures, the major pattern is shown darker than the more irregular reticulation. The entire pattern appears to be a disruptive one which blends well with the dark grey, tuberculous background of the sea star. It may function as protective coloration for the crabs if they move onto the dorsal area of the sea star.

OBSERVATIONS OF THE CRAB ON ITS HOST The sea star collected by the PILLSBURY was the only one of several specimens of L. senegalensis taken which was noticed to have crabs attached to it. No other Minyocerus were collected, either free in the trawl nets or on other sea stars. The crabs were first noticed scuttling across the dorsal surface of the sea star during sorting of the trawl collection on deck. The sea star from Honduras was discovered buried about 3 cm under the sandy bottom in 3 m of water. Two pairs of porcellanids, two large and two small crabs, were seen clinging to the ventral surface of the sea star at the interbrachial arc (i.e., where the arms are attached to the body). Both the sea star and its attached crabs were collected. Two other Luidia, each with two pairs of crabs at the interbrachial arcs, were seen but not collected. The crabs tended to remain in the lower portion of the arc, near the ventral side of the sea star, but moved onto the dorsal surface of the host when prodded or disturbed. If the sea star was turned ventral side up, the crabs moved from the uppermost ventral surface to the now lower dorsal side of the arc. The Honduran observations show that the crab not only is sheltered by staying in the notch formed by the arms of the sea star, but gains additional protection by being covered with sand when the sea star is buried. When Luidia moves on the surface of the sand, the disruptive 246 Bulletin of Marine Science [18(1)

B c

ADE_ BC---- A D FIGURE 3. A, molted carapace of Panamanian female. The major reticulation is similar to that in all other crabs. The minor reticulation, more noticeable under a microscope, is shown here in lighter stipple. B-C, frontal region of the small Honduran female and male, respectively. D-E, small Honduran female and male crabs, respectively. Carpal spines were less developed on these crabs. Each scale indicates 1 mm. coloration on the porcellanids may aid in concealment of the crabs from possible predators.

DISCUSSION Prior to the present record, Minyocerus angustus was known from Florianopolis (= Desterro), Brazil (Muller, 1863), and Surinam, west- ward along the coast of Venezuela to Isla Cubagua which is located offshore from the Araya Peninsula, Venezuela. As mentioned earlier, Haig (1956) left Boone's report from Limon Bay, Panama, open to question, though she considered Boone's Porcel/ana rosamondae as "probably this species ... ," and, in a later paper (Raig, 1966) listed P. rosamondae in the synonymy of Minyocerus angustus. The record from the RjV JOHN ELLIOT PILLSBURY extends the range westward from Isla Cubagua and establishes a positive record from the Limon Bay area. The Honduran specimens extend the range northwestward to about 16°N latitude, 86°W longitude. The only specific host previously reported for crabs collected on the Atlantic side of Panama is Luidia clathrata, which is found (Clark, 1933) from Bermuda to Puerto Rico and well down the coast of Brazil (Raig, 1966). It is usually found in less than 50 fathoms, and seems to prefer a sandy bottom. Luidia senegalensis, here reported as the new host, is 1968] Gore & Shoup: Commensal Crab, Minyocerus angustus 247 found from south Florida (Robert Work, personal communication) throughout the Caribbean Islands and along the Brazilian coast (Clark, op. cit.). It is the only nine-rayed sea star in the Caribbean region. The bathymetric range is restricted to shallow waters. Thus, either species, in the reported range of the crab, is available for commensalistic purposes by M. angustlls, though so far the association has been noted only in the lower Caribbean and southwest Atlantic. Whether Minyocerus angustus is an obligate commensal on Luidia species is, at this time, conjectural. There is no doubt, however, that M. angustus (like the eastern Pacific species, M. kirki) is often found associated with Luidia spp. (Haig, 1956, 1960, 1962, 1966). It is pos- sible, because of the coloration of the crabs, their diminutive size, and their retiring behavior, that many specimens which might have been collected were consequently overlooked, dropped off the host, or were forcibly brushed off during collection. As noted previously, the crabs tend to remain near the undersurface of the host, whether the sea star is right side up or not. In this position, they could easily be scraped off as the trawl net drags over the bottom. Hopefully, careful collection of both sea-star host species will allow the opportunity of further investigation on this most interesting relationship.

SUMARIO NUEVO HUESPEO EN UNA ESTRELLA DE MAR y EXTENSION DE LA DrSTRlBucrON DEL CANGREJO COMENSAL, Minyocerus angustus (DANA, 1852) (CRUSTACEA: PORCELLANIOAE) Minyocerus angustus, cangrejo porcehinido comensal de la estrella de mar Luidia clathrata (Say), se reporta aquI como presente en un nuevo hue-sped, la estrella de mar de nueve brazos Luidia senegalensis (Lamarck). Ejemplares de este cangrejo son comparados con descripciones dadas en ]a literatura. Se describen el color del cangrejo vivo y observaciones de sus habitos. La distribuci6n conocida de M. angustus es ampliada de Isla Cubagua, Venezuela, a 1300 millas (aprox. 2000 km) al norte y oeste hasta BahIa Trujillo, Honduras.

LITERATURE CITED BOONE, LEE ]930. Scientific results of the cruises of the yachts "Eag]e" and "Ara", 1921- 1928, William K. Vanderbilt, commanding. Crustacea: Anomura, Macrura, Schizopoda, Isopoda, Amphipoda, Mysidacea, Cirrepedia, and Copepoda. Bull. Vanderbilt Mar. Mus., 3: 1-221, pis. 1-83. CLARK, H. L. 1933. A handbook of the ]ittoral of Porto Rico and the other West Indian islands. Sci. Surv. Porto Rico & the Virgin Islands, 16 (1): 1-147, pis. I-VII. 248 Bulletin of Marine Science [18(1)

DANA, J. D. 1852. United States Exploring Expedition during the years 1838, 1839, 1840, 1841, 1842, under the command of Charles Wilkes, U. S. N. Vol. 13, Crustacea, part 1, (viii) + 685 pp. 1855. Ibid., Vol. 14, Crustacea, Atlas, pp. 1-27, pis. 1-96. GLASSELL, S. A. 1938. New and obscure decapod Crustacea from the west American coasts. Trans. San Diego Soc. Nat. Hist., 8: 411-454, pIs. 27-36. HAIG, JANET 1956. The Galatheidea (Crustacea Anomura) of the Allan Hancock Atlantic Expedition with a review of the Porcellanidae of the western North Atlantic. Allan Hancock Atlantic Expedition Rpt. No.8: 1-45, pI. l. 1960. The Porcellanidae (Crustacea Anomura) of the Eastern Pacific. Allan Hancock Pacific Expedition, Vol. 24. Pp. 1-440, pIs. 1-41. 1962. Papers from Dr. Th. Mortensen's Pacific Expedition 1914-1916. LXXIX. Porcel1anid crabs from eastern and western America. Vidensk. Medd. fra Dansk naturh. Foren., 124: 171-192, figs. 1-5. 1966. Porcel1anid crabs (Crustacea Anomura). Resultats Scientifiques dcs Campagnes de la "Calypso," 7 (2): 351-358. HOL THUIS, L. B. 1959. The Crustacea Decapoda of Suriname (Dutch Guiana). ZooI. Verh., Leiden, No. 44: 1-296, pIs. 1-16. MULLER, FRITZ 1863. On the transformations of the Porcel1anae. Ann. Mag. Nat. Hist., Ser. 3, 11: 47-50, pI. 1. (Translated by W. S. Dallas from Wieg- mann's Archiv f. Naturgesch., 28 (1): 194-199, pI. 7.) RATHBUN, M. J. 1900. Results of the Branner-Agassiz Expedition to Brazil. 1. The decapod and stomatopod crustacea. Proc. Wash. Acad. Sci., 2: 133-156, pI. 8.