J. Zoo/., Land. (1989) 217, 177-201 The biology of Schizomus vine; (Chelicerata: Schizomida) in the caves of Cape Range, Western Australia W. F. HUMPHREYS Department of Biogeography and Ecology, Western Australian Museum, Francis Streef, Perth, Western Australia 6000 M. ADAMS Evolutionary Biology Unit, South Australian Museum, North Terrace, Adelaide, South Australia 5000 AND B. VINE 86 Schruth Street, Kelmscolf, Wesrem Australia 6111 (Accepled 25 May /988) (With 6 figures in the text) The chelicerate order Schizomida is represented in Western Australia by a single species, Schi:umus vinei Harvey. from caves in the semi-arid Cape Range 011 the North West Cape peninsula. Schizomus vinci occurs in eight of 170 caves known from the range but is found only in areas where the relative humidity exceeds 92°/,.. The sehizomids are associated with a rich fauna (at least II species) mostly ofdetritivores, some ofwhich show troglobitic adaptations. They prey on the cave animals that feed on detritus and are known 10 eat oniscoid isopods. millipedes. cockroaches, worms and S. rinei. The size class structure of the population in cave C 118 was strongly skewed negatively suggesting that the smaller size classes occupy interstices of the infill ofsumps. Schizomids in this cave were found to be distributed at random up to the third nearest neighbour. The minimum population size. with gyX, confidence. was estimated to be 1323 individuals. Schizo/1/lis vinei grew very slowly in vivaria. One female produced nine eggs which did not survive. Schi:olllu$ rim'i has II high mean rate of water loss (470,4 rng g-I h- I) and a low resistance to water loss (15·2 em sec-I); their resistance is about 10 x grellter than that ofa free water surface, but is ahout two orders of magnitude lower than that of some spiders and scorpions. Schizolllus villei excretes a clear fluid and may be ammonotelic. • Al10zyme electrophoresis strongly suggests that individuals from the different caves are of the same species. Consideration ofdimate. age of separation of the caves and the general biology of the schizomids suggests that those caves containing schizomids may be linked. Contents Page Introduction 178 Methods 178 Field 178 Laboratory 179 Population analysis 179 Electrophoresis 179 Husbandry .. 179 177 0952-8369/89/002177 +25 $03·00 © 1989 The Zoological Society of London 178 W. F. HUMPHREYS, M. ADAMS AND B. VINE Water loss [80 Statistics 180 Description of the area 180 CaveCI18 181 Associated fauna [81 Results and discussion 181 Physical environment 181 Size. 184 Breeding. 185 Length/weight 185 Allometry 185 Growth 186 Dispersion 186 Numbers. 187 Food, fceding and habits 188 Genetics. 190 Excretion 191 Water loss 191 General discussion 193 Obligate troglobite? 193 Distribution 193 Population estimates 194 Rainfall necessary for nooding [95 Age of separation of caves as determined by aridity [96 Persistence of the populations 196 Constancy 196 Community relations [97 Connections of the caves 197 References . [98 Appendix I. 201 Introduction Many troglobites occur in exceedingly low numbers (Milchell, 1970), except for those associated with guano deposits where the large and predictable nulrient input sustains high population densities (Mazanov & Harris, 1971). This paper examines a relict population of Schizomus vinei Harvey (Arachnida: Schizomida) reported to occur in low numbers in two caves in Cape Range, Western Australia. The populations are supported indirectly by organic debris thai is washed into the caves by run-otT from intermittent and unpredictable heavy rainfall. Vine, Knott & Humphreys (1988) commented on the conservation of the populations in two caves. This paper examines the population status and degree of genetic isolation of S. vinei populations from four caves in Cape Range, and considers at length the conservation of the populations. Methods Field Cave C 118 (not named) was surveyed to Grade 5·3 using standard speleological methods (Ellis, 1976). Temperature and relative humidity were measured with both a whirling hygrometer (Brannan, England) and an electric hygrometer (KM 8004, Kane May, England) calibrated using saturated standard saIL solutions (Winston & Bates, 1960). Six replicate soil samples were collected from 5 areas within the cave where varying THE BIOLOGY OF SCHIZOMUS IN CAPE RANGE 179 numbers of schizomids occur. The water contcnt of the soil was determined gravimetrically after drying al 70 C. The organic carbon content was determined by the Walkley-Black dichromate oxidation method with glucose as a standard: the presence ofCaC03 up to 50% orthc sample volume gives no interference (Allison. 1965). Schizomid numbers were estimated by direct searching. by nearest neighbour analysis and by mark and recapture methods. Direct searching was conducted under torch-light by various numbers of people searching the same areas on different occasions; the schizomids found were trapped beneath inverted vials to await further examination. On 3 days, the distance to the 3 nearest neighbours (vials) was estimated, to within I em. with a tape measure. The schizomids were measured (total length) and marked with fluorescent powders (Daylight Pigments; Abel Lemon Company, Adelaide). Different colours were used for the north and south side of the cave on the first day, and a third colour on subsequem occasions throughout the cave. After the first day of sampling. all schizomids caught were ex.amined for powder marks under an ultraviolet lamp (Model MS-47: Ultra-violet Products Inc. San Gabriel. California). Laboratory Population analysis: this is considered at length because the status of the population must be known for conservation implications to be assessed. As the number of recaptures from the mark-recapture experiment was small, it is inappropriate to use the traditional algorithms to estimate the population (Otis. Burnham. White & Anderson. 1978) on account of the inherent and pronounced negative bias of their confidence intcrvals (Chapman. 1951: Robson & Regier. 1964: Ricker, 1975). The estimation was therefore conducted using the sequential Bayes algorithm as recently used by Gazey & Staley (1986). This algorithm is being actively developed to deal with the more intractable problems of population estimation (Raftery, Turet & Zeh, 1988). For comparison, the more familiar Bailey's (1951) modification of the Lincoln-Petersen Index 2­ census method was used for each day of recapture, assuming that no marked individual was recaplUred on sequential days; the probability of this, determined by simulation, is 0·037 at the minimum population size with 95% confidence (by Bayes algorithm) of 1323. In addition, the dispersion and density were estimated from the first 3 nearest neighbours following the methods of Thompson (1956) and Morisita (1954), respectively. Electrophoresis: cellulose acetate gel electrophoresis was conducted using standard methods (Richardson, Baverstock & Adams. 1986). Homogenates were made from whole frozen S. villei and used to examine the allozyme variation between populations. For systematic purposes, the null hypothesis under test was that all populations were sampled from the same gene pool ofa single species. Four individuals were examined from each ofcaves C 18 (Dry Swallett), C 106 (Shot Pot) and C 118 and 2 individuals from C 126. Such sample sizes are entirely adequate for systematic studies on allopatric populations (Richardson et al.. 1986). Interpretable gels were found for 20 enzymes and one non-enzymic protein, encoded by a presumptive 24 loci. The enzymes (and protein) used were: Aconitate hydratase (ACO . E.c. 4.2.1.3), Adenosine deaminase (ADA. E.C. 3.5.4.4), Aldolase (ALD, E.C. 4.1.2.13), Enolase (ENOL. E.C. 4.2.1.11), Esterase (EST, E.C. 3.1.1.1), Glyceraldehyde-phosphate dehydrogenase (GAPD, E.c. 1.2.1.2), Aspartate aminotransferase (GOT. E.C. 2.6.1.1), General protein (GP), Glyeerol-3-phosphate dehydrogenase (GPD, E.C. 1.1.1.8), Glucose-phosphate isomerase (GPI, E.C. 5.3.1.9), Hexosaminidase (HEX, E.C. 3.2.1.30), Hexokinase (HK, E.C. 2.7.1.1), Isoeitrate dehydrogenase (IDH, E.C. 1.1.1.42), Lactate dehydrogenase (LDH, E.C. 1.1.1.27), Malate dehydrogenase (MDH, E.C. 1.1.1.37), Peptidases (PEP, E.C. 3.4.11 or 13.*), Phosphoglycerate mutase (PGAM, E.C. 2.7.5.3), Phosphoglycerate kinase (PGK, E.C. 2.7.2.3), Phosphoglucomutase (PGM, E.C. 2.7.5.1), Pyruvate kinase (PK, E.C. 2.7.1.40), and Triose-phosphate isomerase (TPI. E.C. 5.3.1.1). The nomenclature and conventions for referring to alleles and loci follow Richardson el al. (1986). Husbandry: Schizomus vinei was maintained in the laboratory in either 50 ml vials or 50 x 10 x 10 em vivaria: in both cases the ftoorcomprised 1cm or more ofsoil from C 118. The soil was kept moist with distilled watcr 180 W. F. HUMPHREYS. M. ADAMS AND B. VINE TAULf. J The predictability ofvarious rainJall SIll/is/ies' 0/1 North West Cape from /965-/986 inclusive. Tlll'indices/olloll' Colwell ( 1974). The raif!fllll .\·/{IIi.~lic.\' (Ire (A) mOIl/hly raillj{t1I, (il) maximum rainfall ('lIl'11l per mOlllh, lind (ej lIumber v/rain day.5 (> 0·/ 111m) per mOl/til. All analyses ll'ere based Ofl logz chuses ill order 10 eliminate Ille correlal;oll betll'een rhe mea" und t"ariallce in Ihe dara Index A B C Predictability (P) 0·325 0·488 0·344 Constancy (C) 0·131 0·229 0·154 Contingency (M) 0·193 0·258 0·189 CfP 0·404 0·470 0·449 MIP 0·595 0·529 0·550 I Sources of rainfall dala: For Exmouth (Vlaming Head) [965-[967. Exmouth composite 1967-1975 and Lcarmonth 1975-1986 (Microfiche Climatic Averages. Australia and TABS Elements May [986. Bureau of Meteorology. Canberra) to maintain ncar saturated humidity. An incandescent light bulb maintained the temperature above 18 C but the temperature otherwise varied with the ambient weather.