Bijdragen tot de Dierkunde, 53 (2): 233-243 — 1983 Amsterdam Expeditions to the West Indian Islands, Report 28. Predation as a factor influencing the occurrence and distribution of small Crustacea in West Indian groundwaters by Jan H. Stock Institute of Taxonomie Zoology, University of Amsterdam, P.O. Box 20125, 1000 HC Amsterdam, The Netherlands Summary 1. INTRODUCTION from inland Hadziid are known groundwaters Amphipoda During groundwater explorations (1800 sta- of 14 West Indian islands, Thermosbaenacea from those of tions in in the West 43 islands) Indies, great both 9 islands. Only 4 islands show joint occurrence of numbers of animals hypogean were en- Even in islands of hadziids occur groups. joint occurrence, countered in this significantly more often alone in a given locality, than in (see previous reports series). The combination with Thermosbaenacea or Copepoda most frequently represented groups were Cyclopidae. The latter two do not show signifi- groups any Oligochaeta, Gastropoda, and four crustacean for the cant avoidance of each other. Some possible causes taxa: Ostracoda, cyclopid Copepoda, Am- non-random occurrence of small groundwater Crustacea phipoda, and Thermosbaenacea. are discussed; it seems most likely that hadziids predate on Groundwaters river other Thermosbaenacea or (in springs, Crustacea, such as Cyclopidae. wells, caves, This have influence the and beach of islands predation may have, or had, on interstitia) the following of the under considera- actual distributionpatterns groups have been investigated (fig. 1) during a ten tion. years' period (1973-1982) by the Amsterdam Expeditions: Aruba, Curaçao, Bonaire, Isias Résumé Los Roques, La Tortuga, La Blanquilla, Los Des Hadziides des Amphipodes sont connus eaux souter- Testigos, Margarita, Barbados, St. Lucia, raines intérieures de 14 îles des Antilles; des Thermos- Martinique, Dominica, Guadeloupe, Antigua, îles baenacés sont connus de 9 îles. C’est seulement sur 4 Barbuda, St. Eustatius, Saba, St. Barthélémy, les deux rencontrent; mais même dans ces que groupes se St. dernières îles, il est nettement plus fréquent de trouver les Martin, Tintamarre, Anguilla, Anegada, Hadziides seuls à certaine association St. St. une localité, qu’en Virgin Gorda, Tortola, John, Thomas, des Thermosbaenacés des avec ou avec Copépodes St. Croix, Vieques, Culebra, Puerto Rico, deux derniers s’évi- Cyclopidés (tandis que ces groupes ne Mona, Hispaniola (Haiti), Jamaica, Grand de On discute tent pas façon significative). sur plusieurs Cayman Brac, South Caicos, raisons du fait la distribution de Cayman, possibles que ces Providenciales, Great Crustacés souterrains de taille réduite présente ce Inagua, Mayaguana, caractère l’idée la les Crooked San Salvador «non-random»; plus plausible est que Island, Island, de Crustacés Hadziides sont des prédateurs aux dépens Eleuthera, and New Providence. tels les Thermosbaenacés et les Cyclopidés. Ceci peut que The will present paper discuss the occurrence avoir — ou avoir eu — une influence sur la distribution and distribution of three crustacean actuelle de groups, ces groupes. viz. the family Cyclopidae of the Copepoda, the hadziid group of the Amphipoda Gammaridae, and the order Thermosbaenacea, in inland Of these the *) Report 27 has been published in Bijdragen tot de Dier- groundwaters. cyclopids are en- kunde, 53 165-177 countered almost but hadziid (1): (1983). on every island, Downloaded from Brill.com10/03/2021 09:45:49PM via free access - 234 J. H. STOCK PREDATION IN GROUNDWATER CRUSTACEA Fig. 1. Map of the West Indies, showing the islands mentioned in the text (§ 1). Heavy dots: Boundary ofthe distribution distribution the Ther- area of the generically diversified fauna ofhadziid Amphipoda. Light dots: Boundary of the area of mosbaenacea. Heavy strokes: Position of the Anegada Trough. Fig. 2. Distribution of hadziid Amphipoda (H, black dots) and Thermosbaenacea (T, triangles) in the West Indies. Downloaded from Brill.com10/03/2021 09:45:49PM via free access BIJDRAGEN TOT DE DIERKUNDE, 53 (2) - 1983 235 restricted certain calcareous for the International amphipods are to 3rd Symposium of and of islands (Stock, 1977, more recent data Groundwater Ecology (Lodz/Chestochowa, our own), viz. Aruba, Curaçao, Guadeloupe- 1981), which was published recently (Stock, Grande St. the the based Terre, Antigua, Barbuda, Martin, 1982). In present paper, data on Tintamarre, Anguilla, St. Croix, Puerto Rico, the completely sorted samples of the 1973 Hispaniola, and Jamaica (fig. 2). Members of through 1982 campaigns are included, and hadziid also several the the group are known from Marie- provisional results of earlier draft Galante and Cuba have been in definite (Stock, 1980) (Dancau, put now a more shape. visited 1973; Holsinger, 1977), not during our investigations. Besides, marine or anchihaline considered in this hadziids, not paper, are 2. ACKNOWLEDGEMENTS known from certains islands in the Leeward The fieldwork in the various West Indian islands has been group (Bonaire, Curaçao, La Tortuga), in the made ofthe Netherlands Foundation possible by grants for Bahamas, and from Puerto Rico. the Advancement of Tropical Research (WOTRO), The Thermosbaenacea are more limited in their Hague; the Treub Maatschappij, Utrecht; the Beijerinck distribution. They have been found in the Popping Fonds, Amsterdam, the Fonds Landbouw and the Amsterdamse Univer- inland waters of nine islands, viz. St. Croix Hogeschool, Wageningen, siteitsvereniging, Amsterdam. (Stock, 1976), Cuba (Botosaneanu et al., 1973: The has been executed a team of 1 sampling by changing 14; Orghidan, 1973: 38) ), Anegada, Virgin composition, consisting of Lazare Botosaneanu, Nico Gorda, Tortola, St. John, Culebra, Puerto Broodbakker, Sylvia van Lieshout, Jos Notenboom, Jan and Rico, Hispaniola (our own records). Stock, Maarten Stock, Steven Weinberg, and Francisca Moreover, marine or anchihaline thermos- Zijlstra. Many on the various islands, too to be considered in this persons many baenaceans, not paper, are mentioned in various individually, helped us ways: by known from Curaçao (Stock, 1976, and granting permissions, by providing transportation or unpublished data). accomodation, by guiding us to caves and wells, etc. During the fieldwork it looked as if the three under consideration crustacean groups were, although not entirely mutually exclusive, only 3. MATERIAL AND METHODS rarely found in each other's presence. For the Most samples have been collected with a vertical combination hadziids—thermosbaenaceansthis closing net of the Cvetkov type (see Bou, 1975), or with is already clear from the above enumeration of biophreatical pumps (Bou, 1975; Mittelberg, 1980). The localities: the former have been found 14 on entire sample was preserved in formalin 4% and sorted the latter 9 but 4 islands, on islands, only later in the laboratory under a dissecting microscope. islands (Cuba, Hispaniola, Puerto Rico, and Chlorinities have been measured with an EEL electric chlorinimeter, or according to the ASTM method D512. St. Croix) have both groups represented in their In the the present paper term "hadziids" is applied to a groundwaters (fig. 2). of of group strictly stygobiont Amphipoda the family Gam- The whether or not the absence of question the treated maridae, essentially genera by Stock (1977) the one of and the group crustaceans, and Bousfield (1977), or by Barnard & Karaman (1982) simultaneous under the name "Hadziids and Weckeliids". presence of the other is statistical- Only the inland-water are considered the ly significant, is examined in detail in the genera (thus excluding anchihaline the marine or hypersaline genus Saliweckelia or Possible for the observed present paper. causes genus Protohadzia). distribution also discussed. patterns are The hadziids are particularly rich in species in the On the Lesser is Neotropics. Antilles, only one genus A shortened and draft of this with endemics preliminary present, Metaniphargus, on a number of islands. On several other the Greater Antilles genera, in paper has been presented as a congress lecture addition to Metaniphargus , are known (see for anenumera- Thermosbaenacea to be in Cuba tion in in ') appear more common Stock, Botosaneanu, press). than these single records in the literature suggest The thermosbaenaceans of the West Indian inland (Delamare Deboutteville, in litt., 1977). waters comprise uniquely Monodella-like forms. The Downloaded from Brill.com10/03/2021 09:45:49PM via free access 236 - J. H. STOCK PREDATION IN GROUNDWATER CRUSTACEA Halosbaena has been marine to anchihaline not con- calculate the genus even pattern, one can expected sidered. The entire is stygobiont. group number of The joint occurrence. taxon m is The number and Cyclopidae comprise a large of genera in fraction stations present a of the others also sampled, subgenera, some of them strictly stygobiont, 1 this fraction + 0 ■ Sq' being n . known from epigean waters. (0 m m + ) the is in fraction Likewise, taxon n present a (0„ 1 of the stations + 0 ' So' This m + n) sampled. 4. STATISTICAL METHODS leads to the following equation of the expected number of stations of occurrence joint (em + n): 4.1. Test 1 e = + 0 Sq' + 0 m + n (Om m + n ) ■ ■ (0„ m + n ) ■ 1 The or absence of n taxa 2 ■So" S or more e = + presence (1, m, • 0 , simplified: m + „ (0m l islands is A test for 0 + O on k different + f n) compared. m n)(0„ m + n)-S ( . variable for k essen- Since the value for e is based on the scores on one categories, m + n 2 test 1975: is observed values 0 and the tially a x (Meddis, 60) m 0„, expected sample size island will be N = 2e + 0 + 0„, appropriate. per e m + „ m 2 and the number of scores to be used in the x 4.2. Observed values test will be EN . One of the of the (0) e requirements 2 is that the observed X test EN must sum to t up The observed of frequencies solitary occurrence number of the for scores, TiNq. So, frequencies in of each taxon (0/ 0 ) are recorded n e f°r 0 and for 0 should be to m + n> m n adjusted unrelated pairs (0; with Op 0 with 0 ) m n EA with factor 0 by multiplication a T,Nq • with the observed of ~ along frequency the x T,N .