Daniel N. Proud

Diversity and Habitat Use of Neotropical Harvestmen (Arachnida: Opiliones) in a Costa Rican Rainforest

In tropical rain forests, harvestmen assemblages are extremely diverse, with richness often exceeding 25 species. In the neotropics, there are published accounts of harvestmen faunas in South America rainforests (especially Amazonia), but relatively little is known about the community ecology of harvestmen in tropical forests of Central America. In this paper, we provide the first insights into the diverse assemblage of harvestmen inhabiting a wet forest at La Selva Biological Station, Costa Rica. Over five field seasons, we recorded 38 species. During our 2009 field season, we examined variation in species abundance, richness, and composition between adjacent successional forests (young secondary, mature secondary, and primary forests) as well as between distinct habitats (ground/litter layer and shrub/tree layer). Based on night samples (but not day), our results indicate that there are only minor differences in species composition and relative abundance between the forest ages, but no differences in richness. The ground/litter layer and shrub/tree layer habitats differed markedly in species composition, species richness, and relative abundance of several species. Our analysis of covariance supports the hypothesis that leg length is related to climbing behavior for several species belonging to Eupnoi and Laniatores.

Activity Patterns of Two Species of Neotropical Harvestmen (Arachnida: Opiliones) from Costa Rica

ABSTRACT Natural history studies serve as important foundations for future investigations of behavioral ecology and provide biologists with critical information needed for the development of empirical research programs. Relatively little is known about the biology of most species of Neotropical harvestmen in Central America. In this field study, we investigated the activity patterns of two common species Cynorta marginalis (Cosmetidae) and Prionostemma sp. (Sclerosomatidae) in a wet tropical forest in Costa Rica. We used visual encounter surveys along randomly selected transects to compare the relative abundance of these species during morning, afternoon, evening, and late night sampling periods. To generate ethograms, we observed up to three individuals of each species for 10 min along each transect, generating 69 behavioral observations for C. marginalis and 51 for Prionostemma. Both species occupy perches on vegetation and are generally nocturnal with respect to activity. After dusk, individuals of C. marginalis actively climb, interact with conspecifics, and forage on the surfaces of small and large trees. During the day, adult Prionostemma form relatively inactive clusters of up to 40 individuals on arboreal perches and descend to the leaf litter after dusk to forage.

Morphological Changes During Postembryonic Development in Two Species of Neotropical Harvestmen (Opiliones, Laniatores, Cranaidae)

Morphological changes during postembryonic development in the Cranaidae are described on the basis of the examination of an incomplete series of larvae, nymphs, and adults of Phareicranaus calcariferus and Santinezia serratotibialis. The life histories of these species are hypothesized to consist of six nymphal stages, featuring the appearance of secondary male sexual characteristics in the antepenultimate nymph (N5). Color and body shape change dramatically during development. Growth rates for nymphs based upon leg measurements were similar for both species. In S. serratotibialis, the greatest increase in leg size occurred from larva to 1st nymph. The tarsomeres of legs I–IV varied by 1–2 segments per leg for each nymph stage, with the number of tarsal segments increased by 1–2 segments at each stage. Adults had nearly twice as many tarsomeres on leg II than other legs. Ontogenetic changes were observed in the armature of the proximal cheliceral segment, ocularium, pedipalp, opisthosoma, distitarsus III and IV, and leg IV. Morphological changes in postembryonic development in cranaid harvestmen are similar to those reported for other Laniatores. J. Morphol., 2009.

Parasitic and Phoretic Mites Associated with Neotropical Harvestmen from Trinidad, West Indies

Abstract Larval erythraeid mites are common ectoparasites of harvestmen (Opiliones). However, interactions between these mites and hosts in tropical environments have received little attention. In this study, we examined the prevalence and intensity of mite infestations for Neotropical harvestmen from the Caribbean island of Trinidad. Overall, the prevalence of infestation was 9.9%, with significant interspecific variation in the intensity of mite infestation and significant differences in parasitism of hosts between habitats. Harvestmen collected from lowland, crappo-cocorite forest exhibited the highest infestation rates. In our samples, the intensity of infestation varied from 1 to 17 mites per host. Examination by scanning electron microscopy revealed that harvestmen were infested by two taxa of mites, a species of Leptus and another unidentified erythraeid species. Our observations represent the first host records for erythraeid mites parasitizing harvestmen from the families Cranaidae and Manaosbiidae. Mites were found to attach preferentially to the tibia and femur of the leg (175 of 178 observations). In general, the harvestmen of Trinidad exhibited mite parasitism in a fashion similar to temperate species with respect to site of attachment and prevalence and intensity of mite infestation. In the field, we also collected an adult Cynortula sp. (Cosmetidae) that was transporting 30 gravid adults of an oribatid mite (Acariformes, Oribatida, Mixonomata). Cases of mite phoresy upon harvestmen are rare, with our observation representing the first report of phoresy by an oribatid mite upon a harvestman and the first documentation of mite phoresy upon harvestmen in the Caribbean.

Paternal care in a Neotropical harvestman (Opiliones: Cosmetidae) from Costa Rica

Abstract Although relatively rare among harvestmen in the superfamily Gonyleptoidea, paternal care has been observed in the families Manaosbiidae and Gonyleptidae, but not previously in the Cosmetidae. In this study, we describe multiple observations of egg guarding by adult males of an undescribed species of cosmetid harvestman from Volcán Cacao, Guanacaste Province, Costa Rica. Observations were made from 26–28 July 2010, during the wet season. In this species, males only guard eggs after dusk, leaving eggs unattended during the day. Based upon differences in color and size, males guarded eggs through several stages of development. When guarding, males contacted the first two pairs of legs with the eggs. Oviposition sites consisted of the undersides of leaves of small plants, with eggs closely packed together in a single layer covered by abundant, transparent mucus. The largest, darkest eggs were located near the distal tip of the leaf.

The Ecological Significance of Leg Autotomy for Climbing Temperate Species of Harvestmen (Arachnida, Opiliones, Sclerosomatidae)

Abstract In encounters with predators, sclerosomatid harvestmen may employ a variety of defensive tactics including the voluntary detachment of legs (autotomy). The long-term costs of this evasive defense are not fully understood, but prior studies have documented negative consequences for terrestrial locomotion and foraging. In this study, we investigated the impact of leg loss upon locomotion in adult harvestmen (Leiobunum spp.). In southeastern Virginia, these harvestmen regularly climb vegetation and occupy perches on tree trunks, branches, and leaves that are often 1–2 m or more above the ground. In our study, we measured walking and climbing speeds for individuals with 5, 6, 7, and 8 legs. The results of our field surveys conducted over three seasons revealed relatively high frequencies (36–63%) of leg loss. We also found that individuals with six legs occupied perches that were significantly lower in the understory than those with eight legs. In the lab, we observed significantly slower walking speeds for individuals missing one or more legs. We also found that individuals with five legs climb significantly slower than individuals with eight legs. On the bases of the observed frequencies of leg loss in the field, we infer that leg autotomy is a common (and effective) evasive tactic used by harvestmen. However, the reduction in walking and climbing speeds resulting from leg loss may also affect habitat selection, (e.g., perch height) and may ultimately reduce the survivorship of individuals in future encounters with predators.

Diversity of Neotropical Harvestmen (Arachnida: Opiliones) Inhabiting Logs and Palm Fronds in the Rain Forests of Trinidad

ABSTRACT In July and August 2005, we investigated the use of two distinct microhabitats by harvestmen (Arachnida: Opiliones) in crappo-cocorite seasonal forest, lower montane rain forest, and upper montane rain forest of the Northern Range of Trinidad, West Indies. In addition to new locality records, geographic distributions, and microhabitat use, this article provides a preliminary understanding of the species diversity, compositional similarity, and relative harvestmen abundance among forest stands located within three types of rain forest of different altitudes found in Trinidad. We collected harvestmen inhabiting the space within and underneath decaying logs as well as the leaf litter associated with the logs. In upper montane rain forest, in addition to logs, we sampled the sheaths of palm (Euterpe broadwayi Becc. ex Broadway) fronds, another shelter commonly used by harvestmen that was especially abundant at the higher elevations. We collected 173 individuals representing eight families and 14 species. The number of harvestmen per shelter varied from 3.2 individuals per log in crappo-cocorite forest to 0.8 individual per log or palm frond sheath in upper montane rain forest. In the crappo-cocorite seasonal forest, cosmetids, sclerosomatids and stygnids were most abundant. In upper montane rain forest, cranaids and manaosbiids were the most abundant taxa, whereas cosmetids and sclerosomatids were relatively rare. Crappo-cocorite and lower montane forests were very similar in species composition but differed greatly from upper montane forest. The cosmetids Paecilaema inglei Goodnight and Goodnight 1947, Cynortula granulata Roewer 1912, and the stygnid Stygnoplus clavotibialis (Goodnight and Goodnight 1947) were found to be strongly correlated with the crappo-cocorite and lower montane forests, whereas in upper montane forests Santinezia serratotibialis Roewer 1932 and Cranellus montgomeryi Goodnight and Goodnight 1947 were closely correlated.

SEASONAL VARIATION IN PARASITISM BY LEPTUS MITES (ACARI, ERYTHRAEIDAE) UPON THE HARVESTMAN, LEIOBUNUM FORMOSUM (OPILIONES, SCLEROSOMATIDAE)

Abstract We recorded the number of ectoparasitic erythraeid mite larvae (Leptus sp. Latreille 1796) that were attached to 1241 Leiobunum formosum Wood 1870 from a population in southeastern Virginia. The prevalence of infestation (percent of individuals parasitized) exhibited significant annual and seasonal variation, ranging from 0.5% to 20.3%. The mean intensity of infestation (number of mites per parasitized individual) varied from 1.0 to 1.3, with a maximum observed intensity of 3 mites/individual. This study provides the first description of annual and seasonal variation in mite infestation of harvestmen.

Two new species of Manaosbiidae (Opiliones: Laniatores) from Panama, with comments on interspecific variation in penis morphology

Abstract In Central America, the family Manaosbiidae is recorded only from Panama and Costa Rica. Four species occur in this region: Barrona williamsi Goodnight & Goodnight 1942, Bugabitia triacantha Roewer 1915, Poassa limbata Roewer 1943, and Zygopachylus albomarginis Chamberlin 1925. In this paper, we describe Barrona felgenhaueri new species (Coclé Province, Panama) and Bugabitia akini new species (Coclé Province, Panama) and report a new record for B. williamsi (Coclé Province, Panama). We used SEM to examine the penis morphology of Barrona Goodnight & Goodnight 1942 and the Caribbean species Cranellus montgomeryi Goodnight & Goodnight 1947 and Rhopalocranaus albilineatus Roewer 1932. We compared genital morphology of these species with published descriptions for Manaosbiidae from South America. With respect to genital morphology, we found that the most variable characters were the number and relative sizes of the setae that occur on the lateral margins of the ventral plate. Other features that exhibited interspecific variation included the shape of the ventral plate, the shape of the distal border of the ventral plate, and the shape and armature of the apex of the stylus.

PARENTAL CARE IN THE NEOTROPICAL HARVESTMAN PHAREICRANAUS CALCARIFERUS (OPILIONES, CRANAIDAE)

Abstract Parental care in harvestmen may take several forms including egg hiding, egg guarding, egg transport and young guarding. In most species, one adult, usually the female, performs guarding of the young. From 9 July–3 August 2005, we made observations of parental care by adults of the Neotropical cranaid harvestman Phareicranaus calcariferus (Simon 1879) in northern and central Trinidad. Nine observations involved an adult female and young while three appeared to include both an adult female and male with young. The number of young present was inversely related to the size of the young, indicating that parental care in this species may occur over an extended period of time.