The giant fiber system in the forelegs (whips) of the whip spider Heterophrynus elaphus Pocock (Arachnida: Amblypygi)

Summary The front legs of the whip spider H. elaphus are strongly modified to serve sensory functions. They contain several afferent nerve fibers which are so large that their action potentials can be recorded externally through the cuticle. In recordings from the tarsus 7 different types of afferent spikes were identified; 6 additional types of afferent spikes were discriminated in recordings from the tibia and femur. Most of the recorded potentials could be attributed to identifiable neurons serving different functions. These neurons include giant interneurons and giant fibers from diverse mechanoreceptors such as slit sense organs, trichobothria, and a joint receptor. In the present report these neurons are characterized using electrophysiological and histological methods. Their functions are discussed in the context of the animal's behavior.Abbreviations GN giant neuron - S segment     

Electrophysiological studies of olfaction in the whip spider Phrynus parvulus (Arachnida, Amblypygi)

The olfactory response of the whip spider Phrynus parvulus from Costa Rica was examined using a technique analogous to that used for insect electroantennograms on the tarsi of the antenniform legs which bear multiporous sensilla. Responses to 42 chemicals representing different chain lengths of alkanes, carboxylic acids, alcohols, aldehydes, and ketones, as well as some esters, monoterpenes, and phenolics were examined. Fifty-four percent of the chemicals tested elicited responses. Concentration-response curves were generated for guaiacol, hexanal, methyl salicylate, benzaldehyde, octanoic acid, and linalool. Guaiacol, benzaldehyde, and hexanol elicited the greatest responses and no differences were detected between the sexes. Compounds with chain lengths of six carbon atoms generated strong responses and most monocarboxylic acids and ring compounds elicited responses. Some compounds produced increases in potential believed to arise from a hyperpolarizing effect on the neurons. The broad spectrum of chemicals to which these animals respond is similar to results of other studies examining the general olfactory sense of insects. It is possible that odor learning plays a significant role in the behavior of amblypygids.     

Morphology and physiology of peripheral giant interneurons in the forelegs (whips) of the whip spider Heterophrynus elaphus Pocock (Arachnida: Amblypygi)

Summary The tarsi of the modified front legs (whips) of the whip spider Heterophrynus elaphus contain two afferent giant fibers, GN1 and GN2, with diameters at the tibia-tarsus joint of ca. 21 m and 14 m, respectively. The somata of these two neurons lie in the periphery, about 25 cm away from the CNS. These two neurons are interneurons which receive mechanoreceptive inputs from approximately 750 and 1500 bristles, respectively. The receptive fields of GN1 and GN2 overlap; they extend for 40 mm (GN1) and 90 mm (GN2) along the length of the tarsus. About 90% of the synapses onto the giant fibers are axo-axonic. Mechanical stimulation of a single bristle is sufficient to elicit action potentials in one or both interneurons. The response of the interneurons adapts quickly. Average conduction time from the soma to the CNS is 45 ms for GN1 and 55 ms for GN2. Mean conduction velocities are 5.5 and 4.2 m/s, respectively. Activity in the giant fibers does not elicit a motor response; hence the giant fibers do not mediate an escape response. Possible functions of these giant fibers are discussed and compared to those of giant fiber systems in other arthropods.Abbreviations GN giant neuron - S segment     

Coexistence of two species of whip spiders (Genus Heterophrynus) in the neotropical rain forest (Arachnida,Amblypygi)

Summary Heterophrynus longicornis Butler and H. alces Pocock are sympatric and syntopic in Serra do Navio in the central part of Amapá, N.-E. Brazil. Both species are of similar sizes during part of their life cycles. Competition is probably reduced by utilization of different hiding places and strata. In H. longicornis, adults are tolerant towards conspecifics. Male and female are usually found close to each other and, under laboratory conditions, courtship behaviour can be observed even when the female is not receptive. H. alces, on the other hand, is very intolerant, and usually only single specimens are found. Under laboratory conditions, cannibalism is frequent. The ecological implications of these differences are discussed.     

Fine structure of tarsal sensory organs in the whip spider Admetus pumilio (Amblypygi, Arachnida).

The sensory organs on the tarsi of the antenniform first legs of the whip spider Admetus pumilio C. L. Koch (Amblypygi, Arachnida) were examined with the scanning and transmission electron microscope. At least four different types of hair sensilla were found: (1) thick-walled bristles, which have the characteristics of contact chemoreceptors (several chemoreceptive dendrites in the lumen plus two mechanoreceptors at the base); (2) short club sensilla, innervated by 4-6 neurons which terminate in a pore on the tip; they are possibly humidity receptors; (3) porous sensilla, which are either innervated by 20-25 neurons and have typical pore tubules, or they have 40-45 neurons but no pore tubules; both types are considered to be olfactory; (4) rod sensilla occur in clusters near segmental borders; they are innervated by only one large dendrite which branches inside the lumen. Other tarsal receptors are the claws, which correspond to contact chemoreceptors, and the pit organ which resembles the tarsal organ of spiders. Compared to other arthropod sensilla, the contact chemoreceptors are very similar to those of spiders, while the porous sensilla correspond structurally to olfactory receptors in insects; the club and rod sensilla seem to be typical for amblypygids.     

Courtship and mating in the whip spider Phrynichus orientalis Weygoldt, 1998 (Chelicerata: Amblypygi)

Mating behaviour and spermatophore morphology of the south-east Asian whip spider Phrynichus orientalis is described. During courtship there is less bodily contact between mates than in other studied species of the same genus. However, a peculiarity for the species is that the pair often pauses for minutes, sitting front to front without any movement. For spermatophore formation, the male shifts his body under that of the female like in many other species. However, after spermatophore formation, the male lures the female to the spermatophore instead of pulling her as in most other species studied. The spermatophore differs from those of most other species of the genus by the fact that the cushions in front of the sperm masses are replaced by a hard, transparent mass which has the same function as the cushions. Mating behaviour and spermatophore morphology of P. orientalis thus show peculiarities that so far have not been described for other species of the genus. It is not clear whether these characters should be considered plesiomorphic or apomorphic. But it does clearly show that there is more diversity within this genus than expected.     

Evolutionary morphology of whip spiders: towards a phylogenetic system (Chelicerata: Arachnida: Amblypygi)*

The aim of this study is to present a cladogram and phylogenetic system and to use this to discuss the phylogeny and biogeography of the Amblypygi. A total of 29 morphological structures were studied, their plesiomorphic and apomorphic characters or character states were identified, and the resulting data matrix was analysed. As a result, the ‘old’Charontidae or Pulvillata emerge as a paraphyletic group; the genus Paracharon is the sister group of all other amblypygids, which are now termed Euamblypygi. The ‘new’Charontidae (sensu Quintero: the genera Stygophrynus and Charon) are the sister group of the Phrynida or Apulvillata; together they form the Neoamblypygi. The relationships of the genera of the Charinidae cannot be resolved with the available data. They may be a paraphyletic group. The genus Catageus is a possible candidate for being the sister group of the Neoamblypygi. The new system allows a discussion of the phylogeny and biogeography of whip spiders. It also points to unresolved taxa and thus indicates the questions future research should address.     

Metabolic rate in the whip-spider, Damon annulatipes (Arachnida: Amblypygi)

Metabolic rate estimates as well as a measure of their repeatability and response to laboratory acclimation are provided for the amblypygid Damon annulatipes (Wood). This species (mean +/- S.E. mass: 640+/-66 mg) shows continuous gas exchange, as might be expected from its possession of book lungs, and at 21 degrees C has a metabolic rate of 30.22+/-2.87 microl CO2 h(-1) (approximately 229.6+/-21.8 microW, R.Q. = 0.72). The intraclass correlation coefficient (r=0.74-0.89) indicated substantial repeatability in metabolic rate which did not change with laboratory acclimation over a period of 2 weeks. By contrast, absolute metabolic rate declined by c. 16-33%, although this was not a consequence of changes in mass (which were non-significant over the same period). Rather, it appears that a reduction in overall stress or activity in the laboratory might have been responsible for the decline in mass-independent metabolic rate. At the intraspecific level, metabolic rate scaled as microW = 342 M(0.857), where mass is in grams. Metabolic rates of this species are in keeping with its sedentary behaviour such that for a given body size they are lower than those of most arthropods (spiders and insects), higher than the very sedentary ticks, and equivalent to scorpions. These findings have implications for the understanding of the evolution of metabolic rates in arthropods.     

The water-repellent cerotegument of whip-spiders (Arachnida: Amblypygi)

The cuticle of arthropods is usually composed of layers of a chitin-protein-microcomposite, a proteinaceous epicuticle and a thin lipid coating. However, in some instances a thick cement layer (cerotegument) covers the cuticle and may produce elaborate microstructures. This has previously been described for millipedes and mites. Here we report the previously unknown presence of a superhydrophobic cerotegument in whip-spiders (Ambypygi) and reveal its variation in ultrastructure and water-repellence between species. We discuss the relevance of found micro-morphological and physical characters for taxonomy and phylogenetics of this group, and the potential biological functions.     

Tactile learning by a whip spider, <Emphasis Type="Italic">Phrynus marginemaculatus</Emphasis> C.L. Koch (Arachnida,Amblypygi)

The ability of animals to learn and remember underpins many behavioural actions and can be crucial for survival in certain contexts, for example in finding and recognising a habitual refuge. The sensory cues that an animal learns in such situations are to an extent determined by its own sensory specialisations. Whip spiders (Arachnida, Amblypygi) are nocturnal and possess uniquely specialised sensory systems that include elongated ‘antenniform’ forelegs specialised for use as chemo- and mechanosensory feelers. We tested the tactile learning abilities of the whip spider Phrynus marginemaculatus in a maze learning task with two tactile cues of different texture—one associated with an accessible refuge, and the other with an inaccessible refuge. Over ten training trials, whip spiders got faster and more accurate at finding the accessible refuge. During a subsequent test trial where both refuges were inaccessible, whip spiders searched for significantly longer at the tactile cue previously associated with the accessible refuge. Using high-speed cinematography, we describe three distinct antenniform leg movements used by whip spiders during tactile examination. We discuss the potential importance of tactile learning in whip spider behaviour and a possible role for their unique giant sensory neurons in accessing tactile information.     

The fine structure of spermiogenesis in the Amblypygi and the Uropygi (Arachnida)

Summary Spermiogenesis in one species from each of the arachnid groups Amblypygi and Uropygi is described by electron microscopy: The whip spider,Tarantula marginemaculata (Amblypygi), and the whip-scorpion,Mastigoproctus giganteus, (Uropygi). In both species the earliest spermatid has a spherical nucleus and soon acquires an anterior acrosome and a posterior flagellar tail. The flagellun is peculiar in having a 9 + 3 axonemal pattern. By the mid-spermatid stage, the nucleus becomes conspicuously elongated, possibly through the agency of a manchette of microtubules. In the late spermatid, the elongated nucleus begins to coil posteriorly; simultaneously the middle piece and the tail flagellum begin to retract into the cell body to form a coiled intracellular axonema. Membranous profiles appear in the peripheral cytoplasm, possibly to accommodate a decrease in the total area of plasma membrane. The mature sperm is a spherical cell, which includes the following organelles in twisted and fully coiled configuration: an elongated nucleus, an acrosome and an acrosomal filament, a long middle piece with helically arranged mitochondria and an intracellular axonema.     

Beobachtungen zum postembryonalen Wachstum vonTrichodamon froesi Mello Leitao (Amblypygi,Arachnida)

Zusammenfassung Das positive allornetrische Wachstum von Pedipalpen und Laufbeinen vonT. froesi wird demonstriet. Die Zahl der Tibialdornen an der Tibia wird vom vierten Stadium an reduziert bis nur noch die Dornen übrigbleiben, die die terminale Greifschere bilden. Das 1. Beinpaar wächst isometrisch, und die Zahl der Fühlerbeinsegmente bleibt vom 2. Stadium an nahezu konstant. Es wird vorgeschlagen, die Damoniae Simon 1936 und Phrynichinae Simon 1892 in der Familie Phrynichidae zusammenzufassen.

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Postembryonic growth inTrichodamon froesi mello leitao (Amblypygi, Arachnida)

Summary Positive allometric growth of pedipalps and walking legs is demonstrated inT. froesi. From the fourth instar onward, the number of spines on the pedipalp tibia is reduced, and finally only those which participate in the formation of the pincers remain. The first legs grow isometrically, and the number of antenniform leg segments remains nearly constant from the second instar onward. It is suggested that the subfamilies Damoninae Simon 1936 and Phrynichinae Simon 1892 belong to a single family, the Phrynichidae.

     

First evidence of neurons in the male copulatory organ of a spider (Arachnida,Araneae)

Spider males have evolved a remarkable way of transferring sperm by using a modified part of their pedipalps, the so-called palpal organ. The palpal organ is ontogenetically derived from tarsal claws; however, no nerves, sensory organs or muscles have been detected in the palpal bulb so far, suggesting that the spider male copulatory organ is numb and sensorily blind. Here, we document the presence of neurons and a nerve inside the male palpal organ of a spider for the first time. Several neurons that are located in the embolus are attached to the surrounding cuticle where stresses and strains lead to a deformation (stretching) of the palpal cuticle on a local scale, suggesting a putative proprioreceptive function. Consequently, the male copulatory organ of this species is not just a numb structure but likely able to directly perceive sensory input during sperm transfer. In addition, we identified two glands in the palpal organ, one of which is located in the embolus (embolus gland). The embolus gland appears to be directly innervated, which could allow for rapid modulation of secretory activity. Thus, we hypothesize that the transferred seminal fluid can be modulated to influence female processes.     

Spermatophores, female genitalia, and courtship behaviour of two whip spider species, Charinus africanus and Damon tibialis (Chelicerata: Amblypygi)

This paper describes courtship behaviour, spermatophore morphology, and the female genitalia of the African whip spiders Charinus africanus Hansen, 1921 (Charinidae) and Damon tibialis (Simon, 1876) (Phrynichidae). In C. africanus, only the first part of courtship behaviour, up to spermatophore formation, could be observed; though different in detail, it is similar to that of many other species. The small spermatophore of C. africanus contains one large median sperm package. Charinus africanus is one of the Charinus species with thin finger-like gonopods and the first species with such gonopods of which the spermatophore is known. Spermatophores and female genitalia of D. tibialis are similar, though different in details, to those of Trichodamon and Musicodamon. They thus suggest that these two genera are correctly included in the Damoninae.     

The structure of the cleaning brush on the pedipalps of some African Amblypygi (Arachnida)

The external structure of the cleaning organ or brush situated on the tarsus of the pedipalp in the Amblypygi has been examined in the following six species from tropical and southern Africa: Damon variegatus (Perty) Damon medius (Herbst), Titanodamon johnstoni Pocock, Phrynichus scullyi Purcell, Phrynichus bacillifer (Gerst.) and Hemiphrynus machadoi Fage.
In all except one of these species the organ consists of two approximately parallel rows of modified setae; in Hemiphrynus machadoi there is only one. When both rows are present the constituent setae of each are quite different in appearance and structure.
It is probable that the variations in number, size and shape of the setae in these forms furnish specific characters; further indirect support for this is afforded by the marked difference in the structure of the organ in Hemiphrynus as compared with the other five species; taxonomically Hemiphrynus belongs to the subfamily Tarantulinae while all the others are accommodated in the Phrynicinae or Damoninae.
A brush-like cleaning organ of some kind is found on the pedipalp-tarsus of both old and new world Amblypygi and most probably in all members of the order.     

The spider family Selenopidae (Arachnida, Araneae) in Australasia and the Oriental Region

We relimit and revise the family Selenopidae to include four new genera and 27 new species from Australia and the Oriental Region. The family is redefined, as are the genera Anyphops Benoit, Garcorops Corronca, Hovops Benoit, Selenops Latreille, and Siamspinops Dankittipakul & Corronca, to accommodate the new genera and to correct previous inconsistencies in the diagnoses and definitions of the aforementioned genera. The species of Selenops that occur throughout India and China are also reviewed. Three species occur in China: Selenops bursarius Karsch 1879, also known from Japan, Korea and Taiwan, Selenops ollarius Zhu, Sha, & Chen 1990, and Selenops radiatus Latreille 1819, the type of the genus and most widespread selenopid. Selenops cordatus Zhu, Sha & Chen syn. n. is recognized as a junior synonym of Selenops radiatus. Amamanganopsgen. n. is monotypic, with Amamanganops baginawasp. n. (♀; from the Philippines). Godumopsgen. n. is monotypic, with Godumops caritussp. n. (♂; from Papua New Guinea). Karaopsgen. n. occurs throughout Australia and includes 24 species. A new combination is proposed for Karaops australiensis (L. Koch 1875) comb. n. (ex. Selenops), and the new species: Karaops gangariesp. n. (♀, ♂), Karaops monteithisp. n. (♀), Karaops alanlongbottomisp. n. (♂), Karaops keithlongbottomisp. n. (♂), Karaops larryoosp. n. (♂), Karaops jarritsp. n. (♂,♀), Karaops marrayagongsp. n. (♀), Karaops ravenisp. n. (♂,♀), Karaops badgeraddasp. n. (♀), Karaops burbidgeisp. n. (♂,♀), Karaops karrawarlasp. n. (♂,♀), Karaops julianneaesp. n. (♀), Karaops martamartasp. n. (♀), Karaops manaaynsp. n. (♀, ♂), Karaops vadlaadambarasp. n. (♀, ♂), Karaops pilkingtonisp. n. (♀, ♂), Karaops deserticolasp. n. (♀), Karaops ngarutjaranyasp. n. (♂,♀), Karaops francesaesp. n. (♂,♀), Karaops toolbrunupsp. n. (♀, ♂), the type species Karaops ellenaesp. n. (♂,♀), Karaops jenniferaesp. n. (♀), and Karaops dawarasp. n. (♀).The genus Makdiopsgen. n. contains five species from India and Nepal. A new combination is proposed for Makdiops agumbensis (Tikader 1969), comb. n., Makdiops montigenus (Simon 1889), comb. n., Makdiops nilgirensis (Reimoser 1934) comb. n.,(ex. Selenops). Also, there are two new species the type of the genus Makdiops mahishasurasp. n. (♀; from India), and Makdiops shivasp. n. (♀). The genus Pakawopsgen. n. is monotypic. A new combination is proposed for Pakawops formosanus (Kayashima 1943) comb. n. (ex. Selenops), known only from Taiwan. A new combination is proposed for Siamspinops aculeatus (Simon)comb. n. (ex. Selenops). The distribution and diversity of the studied selenopid fauna is discussed. Finally, keys are provided to all of the selenopid genera and to the species of Karaopsgen. n.and Makdiopsgen. n.     

Muscular anatomy of a whipspider, Phrynus longipes (Pocock) (Arachnida: Amblypygi), and its evolutionary significance

Skeletal muscles in the whipspider Phrynus longipes are surveyed and compared with those of other chelicerates to clarify the evolutionary morphology and phylogenetic relationships of the arachnids. Representatives of 115 muscle groups are described and illustrated, and their possible functions are proposed. Principal results of this analysis include new functional models for the operation of the pharyngeal and sternocoxal mechanisms in Amblypygi and a greatly expanded list of apparently unique synapomorphies supporting the monophyly of Pedipalpi (= Amblypygi, Schizomida, Thelyphonida).     

Chinese whip scorpion using 2-ketones in defense secretion (Arachnida: Uropygi)

Summary North American as well as East Asian whip scorpions of the generaMastigoproctus andTypopeltis are known to use acetic acid and caprylic acid as a defense mechanism. In the secretion from defense glands of a ChineseTypopeltis species, 2-ketones (2-heptanone, 2-octanone, and 2-nonanone) were identified as constituents for the first time. While acetic acid is also present as a secretory product, no caprylic acid has been found.Abbreviations CI chemical ionization - EI electron impact - eV electron Volt - GCMS gas chromatography-mass spectrometry - m/z mass/charge ratio (Dalton)     

A phylogenetic analysis of the orb-weaving spider family Araneidae (Arachnida, Araneae)

We present the first cladistic analysis focused at the tribal and subfamily level of the orb-weaving spider family Araneidae. The data matrix of 82 characters scored for 57 arancid genera of 6 subfamilies and 19 tribes (and 13 genera from 8 outgroup families) resulted in 16 slightly different, most parsimonious trees. Successive weighting corroborated 62 of the 66 informative nodes on these cladograms; one is recommended as the 'working' araneid phylogcny. The sister group of Araneidae is all other Araneoidea. Araneidae comprises two major clades: the subfamily Araneinae, and the 'argiopoid' clade, which includes all other subfamilies and most tribes (((Gasteracanthinae, Caerostreae), (((Micratheninae, Xylcthreae), Eruyosaccus ), (Eurycorminae, Arciinae)), Cyrlarachninae), ((Argiopinae, Cyrtophorinae), Arachnureae)). Cyrtarachneae and Mastophoreae are united in a new subfamily, Cyr-tarachninae. The spiny orb-weavers alone (Gasteracanthinae and Micratheninae) are not monophyletic. The mimetid subfamily Arciinae and the 'tetragnathid' genus Zygiella are araneids, but .Nephila (and other tetragnathids) are not. On the preferred tree, web decorations (stabilimenta) evolved 9 times within 15 genera, and were lost once. The use of silk to subdue prey evolved once in cribellate and four times in ecribillate orb weavers. Sexual size dimorphism evolved once in nephilines, twice in araneids, and reverted to monomorphism five times. Evolution in other genitalic and somatic characters is also assessed; behavioral and spinneret features arc most consistent (male genitalia, leg and prosomal features least consistent) on the phylogeny.