Natural history of coastal Peruvian solifuges with a redescription of Chinchippus peruvianus and an additional new species (Arachnida, Solifugae, Ammotrechidae).
Two species of Chinchippus (Ammotrechidae) were studied in central
Peru. Both species are endemic to the hyper-arid coastal desert and
appear to derive most of their energy and nutrients from maritime prey,
such as intertidal amphipods feeding on beach-cast algae or as arthropod
scavengers feeding upon seabird and pinniped carcasses. Data on the
spatial distribution of the two species were obtained from analyzing
stomach contents of one common predator, the gecko Phyllodactylus
angustidigitus, and suggest that both species are more abundant in
insular than in mainland habitats. We redescribe Chinchippus peruvianus
Chamberlin 1920, known only from a female specimen and describe the male
for the first time while C. viejaensis is recognized as new. The new
species is distinguished from C. peruvianus by its darker coloration,
smaller size, and differences in cheliceral dentition.
Keywords: Camel spiders, coastal desert, ecology, Gekkonidae, Peru, Phyllodactylus angustidigitus, taxonomy
(Identification and classification)
Camel spiders (Natural history)
Camel spiders (Distribution)
Brookhart, Jack O.
Cushing, Paula E.
|Publication:||Name: Journal of Arachnology Publisher: American Arachnological Society Audience: Academic Format: Magazine/Journal Subject: Biological sciences; Zoology and wildlife conservation Copyright: COPYRIGHT 2009 American Arachnological Society ISSN: 0161-8202|
|Issue:||Date: May, 2009 Source Volume: 37 Source Issue: 2|
|Topic:||Event Code: 690 Goods & services distribution Advertising Code: 59 Channels of Distribution Computer Subject: Company distribution practices|
|Geographic:||Geographic Scope: Peru Geographic Code: 3PERU Peru|
In the process of investigating the ecology of terrestrial
organisms in the coastal desert and guano islands of central Peru, we
have come across a series of Chinchippus peruvianus Chamberlin 1920 and
a closely related species. These solifuges, along with other terrestrial
predators, thrive in places that could be defined as a barren land of
gravel, sand, and granitic outcrops--a moonscape where arachnids and
lizards somehow manage to survive, reproduce, and colonize new habitats.
The western coast of South America is among the driest places on Earth
(Dietrich & Perron 2006), where arid conditions have persisted for
the last 14 million years (Alpers & Brimhall 1988). Facing this
hyper-arid ecosystem is one of the world's most productive marine
ecosystems, the Peru-Chile cold current (Tarazona & Arntz 2001). The
stark contrast in productivity promotes the exchange of energy and
nutrients between these two adjacent ecosystems, and marine-derived
resources subsidize terrestrial predators along the Peruvian coast
(Catenazzi & Donnelly 2007a) and in other coastal deserts (Polis
& Hurd 1996). In this study we describe the taxonomy and natural
history of the two Chinchippus species and explore their distribution in
relation to the availability of marine-derived resources.
The genus Chinchippus was established by Chamberlin (1920) based on a single female from the Peruvian island of Chincha. He considered it to belong to the African family Daesiidae. Roewer (1934) included Chinchippus in the ammotrechid subfamily Saronominae based on the segmentation of legs I, II, and IV and the palpal spination. Muma (1976) tentatively included it with the saronomines although its placement was still based on Chamberlin's sole female. Based on Chamberlin's single female, the genus Chinchippus can be recognized by: all the legs having a single tarsal segment, no claws on leg I, stridulating ridges on the mesal surface of the chelicera, lateral plates of the "rostrum" shorter than the median plates, and a recurved cephalothorax.
One of us (AC) conducted fieldwork at the Paracas National Reserve (PNR; 13[degrees]51'S, 76[degrees]16'W), ~19 km S of the Chinchas islands, in the Peruvian Region of Ica (Fig. 1). This reserve protects 335,000 ha of coastal waters and subtropical Peruvian coastal desert, including a variety of arid and hyper-arid terrestrial habitats. The PNR includes the Paracas Peninsula, which forms the southern edge of Paracas Bay, and the islands of Sangayan and La Vieja. The coastal topography is extremely heterogeneous and includes sandy, gravel, pebble and boulder beaches; cliffs; wind-shaped landforms; and uplifted ancient beaches. The climate is characteristic of the arid coastal desert of Peru and northern Chile and receives less than 2 mm of rain per year (Craig & Psuty 1968). Temperatures are mild and range between an average high of 22.9[degrees] C in February to an average low of 16.3[degrees]C in August (Environmental Resources Management 2002).
Using the methods of Muma (1951), Brookhart & Muma (1981, 1987), Muma & Brookhart (1988), and Brookhart & Cushing (2004), we measured total length; length ofpalpus, leg I, leg IV; length and width of chelicera and propeltidium; width of base of fixed finger; and length and width of female genital operculum using Spot Basic [TM] with an Olympus SZX12 microscope at 25X magnification. All measurements are in millimeters. Ratios used previously by Brookhart & Cushing (2002, 2004) were computed. These ratios are as follows: A/CP: the sum of the lengths of palpus, leg I, and leg IV divided by the sum of length of chelicera and propeltidium indicating length of appendages in relation to body size. Longlegged species have larger A/CP ratios. Because there is no fondal notch, the cheliceral width/fixed finger width ratio is used to indicate whether the fixed cheliceral finger of the male is thin or robust in relation to the size of the chelicera. Genital operculum length/genital operculum width represents the relative size of the female genital operculum in terms of length and width. Species determinations were based on a combination of color comparisons, the shape and dentition patterns of the male chelicerae, palpal setation, and color patterns of the propeltidium, palpus, and legs. The shape of the female chelicerae and the female genital operculum margin were observed using the method of Brookhart & Cushing (2004). Cheliceral dentition patterns were based on the method of Maury (1982) in which, for example, PT-1-2-AT indicates one primary tooth, two intermediate teeth, and one anterior tooth.
[FIGURE 1 OMITTED]
Collections from which material was borrowed or deposited include the Museum of Comparative Zoology at Harvard University, Cambridge, Massachusetts, USA (MCZ); the Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima, Peru (MUSM); and the Denver Museum of Nature and Science, Denver, Colorado, USA (DMNS).
We collected solifuges by using pitfall traps or by opportunistically collecting during nocturnal walks. We used pitfall traps consisting of plastic cups 9 cm in diameter and 10 cm deep filled with a mix of water and detergent along the southern end of Paracas Bay between 6-9 January and 6-11 April 2003. During the January trapping, a series of three pitfall traps were placed near sandy/muddy beaches in coastal dunes and the adjacent desert at 5, 10, and 15 m distance from shore. During the April trapping, we placed pitfall traps near shelly beaches along transects at 0, 0.1, 1, 10 and 100 m from shore. We installed three transects, each one composed of three lines of pitfall traps. In addition to pitfall trapping, we also counted and measured solifuges in 90 1-m2 plots in the intertidal zone in March 2003. Count data of the March and April trapping period were reported by Catenazzi & Donnelly (2007a). Here we report count data from the January trapping, as well as solifuge size-distribution data from the March trapping along the shelly beach. Means are reported 6 SE and statistical tests are considered significant at P < 0.05.
We include anecdotal observations on predators, prey, and behavior of solifuges observed in the field. Some of these observations were captured in photographs and video and are available online at http://acatenazzi.googlepages.com/chinchippus.
We relied upon stomach content examinations of the gecko Phyllodactylus angustidigitus Dixon & Huey 1970, a common and ubiquitous reptile in the coastal desert, to better understand the distribution of solifuges in the coastal desert of the Paracas Peninsula and the islands of Sangayan and La Vieja. These geckos feed opportunistically on any live terrestrial arthropod of appropriate size, including beach hoppers, centipedes, arachnids, and insects (Catenazzi & Donnelly 2007a), and do not masticate their prey, facilitating the task of identifying prey remains in the stomachs. Stomach contents were obtained by inserting a small catheter through the esophagus and by flushing the geckos' stomachs with water (Catenazzi & Donnelly 2007a). Stomach contents (n = 814) were collected from Isla La Vieja (4 sites), Isla Sangayan (3 sites), and the Paracas Peninsula (10 sites). We considered whole prey items only to calculate frequency of occurrence of Chinchippus prey with respect to number of geckos sampled and with respect to total number of prey items in all pooled stomach contents.
[FIGURES 2-8 OMITTED]
Family Ammotrechidae Roewer 1934 Subfamily Saronominae Roewer 1934 Genus Chinchippus Chamberlin 1920 Chinchippus peruvianus Chamberlin 1920 (Figs. 2-8)
Chinchippus peruvianus Chamberlin 1920:36-37.
Material examined.--Type: PERU: Ica Region: female holotype, Islas Chinchas (13[degrees]37'37"S, 76[degrees]23'21"W), 26 October 1919, R.C. Murphy (MCZ 519).
Other material: PERU: Ica: Paracas Bay: 2 [female] (1 from the stomach content of Phyllodactylus angustidigitus), Cangrejal (13[degrees]51'03"S, 76[degrees]17'08"W, 1 m elev.), 3 March 2003, A. Catenazzi (DMNS); 2 [male] same data except 25 March 2003, A. Catenazzi (DMNS); 2 [female], La Aguada (13[degrees]51'44"S, 76[degrees]16'15"W, 2 m elev.), 7 January 2003, A. Catenazzi (DMNS); 1 [male], Museo de Paracas Julio C. Tello (13[degrees]52'00"S, 76[degrees]16'26"W, 13 m elev.), 25 March 2003, A. Catenazzi (DMNS).
Diagnosis.--Chinchippus peruvianus is larger and lighter than C. viejaensis and differs by cheliceral dentition (compare Figs. 7 and 11).
[FIGURE 9 OMITTED]
Description.--Female holotype: Color: Overall color as described by Chamberlin (1920): chelicera mottled violetbrown; propeltidium violet-brown with a pale creamy light ovate area highlighted by a lighter median band extending from eye tubercle to posterior end of propeltidium; eye tubercle dark (Fig. 2); mesapeltidium, metapeltidium white; abdomen creamy yellow with a median mottled violet-brown stripe dorsally and creamy grey laterally and dorsally; palp darker on tarsus and femur, metatarsus and tibia pale to white, coxa creamy yellow (Fig. 3). Legs II, III, IV light, violet-brown on tarsus, metatarsus, and apical parts of the tibia, darker on distal end of tibia as in femur, coxa creamy white. Leg I creamy white except for femur, which is a light violet; malleoli white.
Chelicera: fondal teeth graded III, I, IV, II; Fixed finger teeth arranged 1-PT-1-MT-1-AT; movable finger teeth arranged PT-1-2-AT (Fig. 4; however, Chamberlin illustrates PT-1-AT). Six to seven stidulatory ridges on the meso dorsal aspect of the chelicerae.
Palp: tarsus/metatarsus ratio 3:1.
Legs: leg IV tarsus with ventral paired setae arranged 2-2-2-2-2-1.
Abdomen: genital operculum: clavate with anterior arms thick, median edge recurved forming a deep central cavity accessing the genital opening, posterior edge straight (Fig. 5).
Male: Color: color pattern, including appendages, the same as in the female except the median pale stripe extends only from the posterior third of the propeltidium towards the ocular tubercle (Fig. 6); chelicera mottled dorsally and ectally coalescing anteriorly (Fig. 7); pale ventrally; malleoli white.
Chelicera: fondal teeth graded I-III-II-IV ectally and I, III, II mesally; fixed finger teeth arranged PT-1-2-MT-1-AT; movable finger teeth arranged PT-1-2-AT (Figs. 7, 8). Flagellum a broadly elliptical structure attached to the fixed finger above the primary tooth, slightly to the dorsal edge. The attachment appears to be a concave structure. No setae or fringes are seen on the edges of the flagella. It bears some resemblance to the flagella of Saronomus capensis (Kraepelin 1899) (Maury 1982:127-130, figs. 1-8). Six to seven stridulatory ridges on the mesal dorsal aspect of the chelicerae (Fig. 8).
Palpus: tarsal/metatarsal ratio of 3.4:1 (Fig. 3).
Legs: all legs with a single tarsal segment; leg I with no claw and slightly enlarged (bulbous) tarsus; leg IV with ventral spination of 2-2-2-2-2-1.
Dimensions.--Female holotype: total length 10.0, cheliceral length 5.0, cheliceral width 1.7, propeltidium length 1.75, propeltidium width 3.15, palpus length 10.0, first leg length 8.0, fourth leg length unknown (damaged). Ratios: A/CP (cannot be computed), genital operculum length/width 0.5.
Females (n = 4): total length 12.0-16.0, cheliceral length 4.4-4.85, cheliceral width 1.37-1.65, propeltidium length 1.82.2, palpus length 12.0-16.0, first leg length 10.0-11.0, fourth leg length 16.0-20.0. Ratios: A/CP 7.26-7.48.
Males (n = 3): total length 12.5-13.5, cheliceral length 2.52.7, cheliceral width 0.88-0.99, propeltidium length 1.7-1.75, propeltidium width 1.8-2.2, palpus length 12.5-13.5, first leg length 9.0, fourth leg length 17.0-19.0. Ratios: A/CP 10.3-11.7.
Chinchippus viejaensis new species (Figs. 9-14)
Material examined.--Types: PERU: Ica Region: male holotype, Isla La Vieja, Reserva Nacional de Paracas, 14[degrees]26'28.4"S, 76[degrees]12'28.4"W, 230 m, 15 September 2003, A. Catenazzi (DMNS). Allotype female collected with holotype (MUSM).
[FIGURES 10-14 OMITTED]
Etymology.--Named for the type locality, Isla La Vieja, Peru.
Diagnosis.--This species can be differentiated from C. peruvianus by its darker coloration, smaller size, and differences in cheliceral dentition (compare Figs. 7 and 11).
Description.--Male holotype: Color: pale mottled violet to dark violet-brown overall; palpal tarsus, metatarsus, tibia, and apical two thirds of the femur dark violet-brown dorsally, creamy white ventrally; legs I and II dusky brown and violetbrown at the tibia-femur; legs III and IV violet-brown dorsally on tibia, fibula, and apical portion of tarsus; propeltidium darker violet-brown with a very pale ovate area and a median thin, pale stripe extending from eye tubercle to the posterior of the propeltidium (Figs. 9, 10); chelicerae mottled violet-brown (Figs. 9, 11); abdomen with dorsal violet-brown patches on each sternite dorsally (Fig. 9); malleoli white.
Chelicera: fondal teeth three of equal size, fixed finger dentition 1-P-M-1-A, movable finger dentition P-1-A. Six to seven stridulatory ridges found on posterior mesal surface of chelicerae (Figs. 11, 12). Flagellum of C. viejaensis similar to C. peruvianus with a slightly narrow anterior opening and perhaps a more medial attachment above the primary tooth. No setae or fringe is visible. The cheliceral dentition pattern shows some similarity to Ammotrechula gervaisii (Pocock 1895) (Roewer 1934:600) but has no mesal tooth and no fringed flagellum. Palpus: metatarsus/tarsus ratio 3:1; no spine-like setae (Fig. 13).
Legs: leg I with no claw; leg IV with 2-2-1 spine-like setae on the ventral aspect of the tarsus and 2-2-1-1 on the metatarsus.
Female allotype: Color: very similar to the male with the abdominal tergites a lighter color (Fig. 9). The median pale ovate area of the propeltidium is lighter in the female. Leg III femur creamy white.
Chelicera: fixed finger dentition P-1-M-1-A; movable finger P-1-A; fondal teeth III, I, II, IV ectally and mesally; 5-6 stridulatory ridges on the dorsal mesal aspect (Fig. 12).
Palps: metatarsi/tarsi ratio of 2.5:1.
Legs: leg IV with 2-2-1 spine-like setal pattern on ventral aspect of the tarsus and 2-2-1-1 on the metatarsus.
Abdomen: genital operculum similar to C. peruvianus with a deep central cavity forming the entrance to the genital orifice.
Dimensions.--Male holotype: length 10.0, cheliceral length 2.35, cheliceral width 0.97, propeltidium length 1.54, propeltidium width 2.02, palpus length 10.0, first leg length 7.0, fourth leg length 8.0. Ratios: A/CP 6.84. Female allotype: total length 11.0, cheliceral length 2.75, cheliceral width 1.04, propeltidium length 1.51, propeltidium width 2.27, palpal length 7.0, first leg length 6.0, fourth leg length 6.5. Ratios: A/CP 5.64.
Previous to this study, Chinchippus was a monotypic genus based on a single female specimen. The identification of the associated male and a second species supports Chamberlin's (1920) erection of this genus. These two species are in the subfamily Saronominae based on tarsal segmentation of the 4th leg and the flagellar structure. These characters differentiate the species in the Saronominae from all species currently placed in the Ammotrechinae. The genital opercula of the two species of Chinchippus are very similar and differ from other members of the subfamily Saronominae or Ammotrechinae.
[FIGURE 15 OMITTED]
ECOLOGICAL RESULTS AND DISCUSSION
Chinchippus peruvianus.--Murphy (1925) collected the holotype in a building of the Compaflia Administradora del Guano on the Islas Chinchas and reported that individuals hunt for invertebrates attracted to a light source at night. We made most of our collections and observations on the natural history of C. peruvianus at the Paracas Peninsula and on Isla Sangayan. The species appeared to be extremely abundant along a 2 km stretch of shelly beach near the southern end of Paracas Bay (Catenazzi & Donnelly 2007a, b), where individuals could easily be found by lifting rocks, empty shells, and dried marine wrack near shore. At Isla Sangayan, we observed C. peruvianus under rocks and carcasses of South American sea lions (Otaria flavescens Pearon 1816).
Results of the January pitfall trapping near sandy/muddy beaches of Paracas Bay (Table 1) suggest that C. peruvianus was more frequent along shelly beaches (see results in Catenazzi & Donnelly 2007a) than it was along sandy or muddy beaches (see below for data from gecko stomach content analyses in support of this hypothesis). Body length distribution for individuals captured on shelly beaches during March 2003 (Fig. 15) averaged 9.4 (+ OR -) 0.4 mm for the population including immatures (n = 101); the maximum body length was 20.2 mm for a female.
Chinchippus peruvianus was found in stomach contents of P. angustigitus from most sites in the Paracas Peninsula and from all sites on Isla Sangayaan (Tables 2, 3; Fig. 1). Note that the site with 100% frequency of occurrence of C. peruvianus (gull colony on Sangayaan) was based on the stomach contents of only three geckos. At the Paracas Peninsula, near-shore sites along Paracas Bay and Lagunillas Bay had the highest frequencies of occurrence, possibly because of the large amount of beach-cast macro-algae supporting abundant populations of intertidal arthropods and/or because these beaches were easily accessible to both solifuges and geckos. Frequencies of occurrence were low at coastal sites near cliffs (Arquillo, Yumaque, Playa Roja) or sites that are exposed to the ocean (Los Viejos, Talpo), similarly to distribution patterns found in P. angustidigitus geckos (Catenazzi & Donnelly, unpublished data). Chinchippus peruvianus readily excavates burrows in fine sand when disturbed. The burrowing behavior included biting, raking, and plowing sand at irregular intervals. However, C. peruvianus was also found in pebble beaches and in coarse soil where other microhabitats replace burrows (e.g., dried macroalgae, sea lion and seabird carcasses; A. Catenazzi pers. obs.).
Other species of South American solifuges seem to be associated with vegetation cover and soil characteristics: for example Xavier & Rocha (2001) detected a preference of Mummucia mauryi Rocha (in Xavier & Rocha 2001) for areas covered by Opuntia inamoena (Cactaceae) during the dry season, whereas Rocha & Carvalho (2006) and Martins et al. (2004) noted that white sandy soils where solifuges can easily excavate their burrows may facilitate colonization by Mummucia taiete Rocha & Carvalho 2006 and M. coaraciandu Pinto-da-Rocha & Rocha 2004 respectively. In the case of C. peruvianus (as well as C. viejaensis, see below), vegetation cover is unlikely to explain distribution patterns because it is extremely scarce and absent at most sites. Island and coastal habitats colonized by the two Chinchippus also differ widely in soil types (A. Catenazzi, pers. obs.; see habitat descriptions). The higher frequency of occurrence of these solifuges in places that receive marine-derived energy and nutrients, such as beaches with stranded marine macroalgae colonized by arthropods or insular seabird colonies with arthropod scavengers and ectoparasites suggests that food availability in the hyper-arid Peruvian coastal desert may explain distribution patterns.
Seasonal activity can be inferred from results of the geckos' stomach contents, by assuming that the feeding preference of geckos did not vary seasonally. Solifuges at Paracas Bay were most frequent in the geckos' stomachs during the austral summer (Table 3), and their frequency of occurrence with respect to the total number of prey items from March to December 2003 (including data from December 2004) followed a polynomial curve (y = 0.42[x.sup.2] - 6.8x + 27.7, R = 0.81) with a minimum predicted value for August (0.3% frequency of occurrence). This seasonal activity contrasts with the phenology described by Martins et al. (2004) for M. coaraciandu in the Brazilian Cerrado, where surface activity based on pitfall traps was negatively correlated with monthly temperature. However, higher temperatures in the Cerrado were associated with higher rainfall, which could also influence solifuge activity. Rainfall in Paracas is negligible throughout the year, but average night temperatures can be low in the austral winter and could limit solifuge activity.
The diet of C. peruvianus is dependent upon marine sources of energy and nutrients. In the case of supratidal populations, such as those in Paracas Bay (Tables 3 and 4), solifuges rely on intertidal algivores for their diet (Catenazzi & Donnelly 2007a). The beach hopper Transorchestia chiliensis (Amphipoda, Talitridae) was the most common prey item based on field observations (5 out of 10 feeding events). Analyses of stable carbon isotopes also suggested that these beach hoppers were an important prey item for C. peruvianus (Catenazzi & Donnelly 2007a, b).
Insular solifuge populations likely feed on ectoparasites and other arthropods found in detritus or on the carcasses of seabirds and pinnipeds because the Islas Chinchas (type locality of C. peruvianus) are entirely devoid of vegetation, and Isla Sangayaan has scant vegetation that occupies a tiny fraction of the island (the site Lomas in Fig. 1); both islands are mostly cliff-bound. For solifuge populations near the Otaria flavescens colony on Isla Sangayan (site Lobera in Fig. 1), arthropod scavengers of pinniped carcasses are likely to be important dietary items, as suggested by the high carbon and nitrogen stable isotope values (albeit only two individuals were analyzed, with [[delta].sup.13]C = -14.64 [per thousand] and 14.89 [per thousand] and [[delta].sup.15.N] = 24.33 [per thousand] and 25.58 [per thousand]; A. Catenazzi, unpubl. data). Nitrogen isotopic values increase on average by 3.4 [per thousand] for each trophic interaction and therefore can be used to estimate the trophic position of an organism (Post 2002). Nitrogen isotopic values of O. flavescens on Sangayaan average 17.44 6 0.35 [per thousand] (Catenazzi & Donnelly 2008); therefore, isotopic values of C. peruvianus are consistent with the idea that solifuges feed on scavengers of O. flavescens; (i.e., that they are two trophic positions above O. flavescens).
Natural predators of C. peruvianus at the Paracas Peninsula and Sangayaan include, in addition to P. angustidigitus, the scorpion Brachistosternus ehrenbergii (Gervais 1841), the spider Odo sp. (Zoridae), as well as conspecific individuals. Cannibalism is likely to be common, because these solifuges occur at high density in the first meters from shore. We observed cannibalism in the field on two occasions, and all captive encounters of pairs of C. peruvianus resulted in one individual devouring the other one.
The tsunami that followed a 7.8 magnitude earthquake on 15 August 2007 modified the coastal landscape in Paracas Bay. High waves removed many of the supralitoral dunes where C. peruvianus specimens had been collected for this study. It is possible that the flooding of the supratidal areas caused a decline in local populations because Catenazzi & Donnelly (2007a) noted that most C. peruvianus are found in the supratidal zone within 1 m from the high mean tide level. However, C. peruvianus could recolonize supratidal areas from sections of beach that were protected from the tsunami by a steeper slope of the beach and/or by the presence of rocks and other topographic features.
Chinchippus viejaensis.--This species has only been collected from Isla La Vieja (also called Isla Independencia) in central Peru. This island (area 60.86 ha) is located in Independencia Bay, approximately 6 km west of the mainland and 1.6 km north of a smaller island, Santa Rosa (Fig. 1). Both La Vieja and Santa Rosa are guano islands where hundreds of thousands of seabirds, mainly guanay cormorants (Phalacrocorax bougainvillii Lesson 1837) and Peruvian boobies (Sula variegata Tschudi 1843), used to congregate. At the time of our visits between July and November 2003, La Vieja did not have any breeding colony of these two guano bird species. However, the upper parts of the island were interspersed with nests of kelp gulls (Larus dominicanus Lichtenstein 1823) and Peruvian diving-petrels (Pelecanoides garnotii Lesson 1828). Most specimens of Chinchippus viejaensis were collected in pitfall traps and stomach contents of the gecko P. angustidigitus from a small ridge on the southern slope of the island (type locality, site AB on Fig. 1). The slope measures ~12[degrees] and is exposed towards the south. The ground is covered with coarse pebbles (16-32 mm grain size) interspersed with a few granitic outcrops. No plants grow along the ridge or neighboring areas; however, a thin lichen crust covered some rocks along the top of the ridge. Predominant winds carry ocean aerosols and moisture towards the ridge, which may explain the presence of lichens in an otherwise unproductive environment. During our November visit, we observed many nests of kelp gulls; most nests had been built between rocks along the ridge.
Based on our observations, we can document predation of this solifuge by P. angustidigitus only. Chinchippus viejaensis was found in 18.7% of the gecko stomach contents from the entire island, and in 54.5% (12 in 22) of the stomach contents collected at the AB site (Fig. 1, Table 4). Additional sampling locations (Fig. 1) included the western slope of the island (site AC), the beach near Pan de Azuacar, and the guano area north of Pan de Azuacar. Site AC is similar to site AB in being a barren slope with granitic outcrops and seabird nests. However, this slope is steeper (19[degrees]) and exposed to the west. The ground is composed of fine to medium pebbles with some large rocks and several granitic outcrops. Subterranean nests of Peruvian diving-petrels occupy areas of very fine pebbles and coarse sand, whereas nests of kelp gulls (much less frequent than at the AB site) are located among rocks in the granitic outcrops, along with very few plants of Solanum murphyi I.M. Johnst. (four plants within a 2.25-ha quadrant plot). The beach near Pan de Azuucar is made of coarse pebbles frequently littered with marine wrack including kelp and crustacean carcasses. The ground adjacent to the beach is a gentle slope that abuts on a shallow depression to the northwest of Pan de Azuacar beach. Much of this slope had been used by guanay cormorants and Peruvian boobies for nesting ground because at the time of our visit, the ground was covered with--30 cm of guano. Similarly, guano birds once occupied the guano area to the north of the mentioned shallow depression.
It is likely that invertebrates feeding upon seabirds or consuming detritus associated with seabird activity (e.g., regurgitates, feathers, guano, etc.) are important prey items for this solifuge species because the extreme aridity and scant primary productivity of the island supports very few herbivores. In support of this hypothesis, the occurrence and frequency of C. viejaensis in the gecko stomach contents almost doubled at the onset of the breeding season of kelp gulls in November (Table 5).
We thank the Reserva Nacional de Paracas for logistic support, the National Institute for Natural Resources (INRENA) for issuing research and collecting permits, PROABONOS and its staff for authorizing our visit to Isla La Vieja, and J. Carrillo for field assistance. We thank anonymous reviewers who provided helpful comments that improved the manuscript. AC was funded by a Florida International University (FIU) Dissertation Year Fellowship and by grants from the Organization for Tropical Studies, the PADI Foundation, the American Museum of Natural History, the FIU Graduate Student Association and the Tinker Field Research Grant. PEC and JOB were supported by National Science Foundation grant DBI-0640245 awarded to PEC. This is publication number 152 of the Tropical Biology Program at FIU.
Manuscript received 25 March 2008, revised 11 December 2008.
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Alessandro Catenazzi (1): Department of Biological Sciences, Florida International University, Miami, Florida 33199, USA
Jack O. Brookhart and Paula E. Cushing: Department of Zoology, Denver Museum of Nature and Science, 2001 Colorado Blvd., Denver, Colorado 80205-5798, USA
(1) Current address: Department of Integrative Biology, University of California, Berkeley, 3060 Valley Life Sciences Bldg #3140, Berkeley, California 94720-3140, USA. E-mail: firstname.lastname@example.org
Table 1.--Average number of Chinchippus peruvianus captured per pitfall trap near sandy and muddy beaches at Paracas Bay between 6-9 January 2003. Position = distance from the mean high tide level. Traps = number of pitfall traps. No males were captured in pitfall traps. Position Traps Females Immatures 5m 27 0.11 [+ or -] 0.06 0.04 [+ or -] 0.04 10m 27 0.07 [+ or -] 0.05 - 15 m 27 0.07 [+ or -] 0.05 0.04 [+ or -] 0.04 Total 81 0.09 [+ or -] 0.03 0.02 [+ or -] 0.02 Table 2.--Spatial variation in the frequency of occurrence of Chinchippus peruvianus in stomach contents of the gecko Phyllodactylus angustidigitus in 10 sites of the Paracas Peninsula, Peru between March and December 2003. See Fig. 1 for site locations. Geckos = number of stomach contents examined; Occurrence = frequency of C. peruvianus in the geckos' stomach contents; Prey items = number of all prey items in the geckos' stomach contents; Frequency = frequency of C. peruvianus relative to the number of prey items. Site Geckos Occurrence Prey items Frequency Paracas Peninsula Cangrejal 127 22.8% (29) 607 5.8% (35) La Aguada 43 4.7% (2) 383 0.5% (2) Sequioan 33 12.1% (4) 218 1.8 % (4) Yumaque 17 - (0) 81 - (0) Talpo 41 - (0) 171 - (0) Lagunillas 41 9.8% (4) 235 2.1 % (5) Playa roja 24 8.3% (2) 166 1.2 % (2) Los Viejos (beach) 54 - (0) 421 - (0) Los Viejos (desert) 38 5.3% (2) 96 2.1% (2) Arquillo 18 5.6% (1) 123 0.8% (1) Isla Sangayan Lobera 178 1.1 % (2) 1408 0.2% (3) Gull colony 3 100.0% (3) 65 20.0% (13) Lomas 27 3.7% (1) 164 0.6% (1) Total 644 7.8% (50) 4138 1.6% (68) Table 3.--Seasonal variation in the frequency of occurrence of Chinchippus peruvianus in stomach contents of the gecko Phyllodactylus angustidigitus at Paracas Bay, Peru during March-December 2003. See Fig. 1 for site location and Table 2 for table headings; * includes 15 stomach contents collected in December 2004. Month Geckos Occurrence Prey items Frequency March 12 25.0% (3) 40 10.0% (4) April 35 20.0% (7) 130 7.7% (10) May 43 18.6% (8) 176 5.7% (10) June 27 18.5% (5) 188 2.7% (5) July 9 -(0) 35 -(0) August 16 6.3% (1) 143 0.7% (1) September 3 -(0) 89 -(0) October 8 25.0% (2) 65 3.1% (2) November 13 -(0) 112 -(0) December * 19 26.3% (5) 55 9.1% (5) Total 170 18.2% (31) 990 3.7% (37) Table 4.--Spatial variation in the frequency of occurrence of Chinchippus viejaensis in stomach contents of the gecko Phyllodactylus angustidigitus in four sites of Isla La Vieja, Peru. See Fig. 1 for site locations and Table 2 for table headings. Site Geckos Occurrence Prey items Frequency AB 22 54.5% (12) 449 3.6% (16) AC 19 15.8% (3) 96 3.1 % (3) Pan de Azuacar Beach 36 2.8% (1) 224 0.4% (1) Zona guanera 14 7.1% (1) 182 0.5% (1) Total 91 18.7% (17) 951 2.2% (21) Table 5.--Seasonal variation in the frequency of occurrence of Chinchippus viejaensis in stomach contents of the gecko Phyllodacty- lus angustidigitus at Isla La Vieja, Peru. See Fig. 1 for location and Table 2 for table headings. Month Geckos Occurrence Prey items Frequency July 35 14.3% (5) 403 1.2% (5) September 38 18.4% (7) 376 2.4% (9) November 18 27.8% (7) 172 4.1% (7) Total 91 18.7% (17) 951 2.2% (21)
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