Gerd Alberti

Gerd Alberti
Universität Greifswald · Institute of Zoology

Prof. em. Dr. rer. nat.habil, Dr. h.c.

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266
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April 1996 - March 2008
Universität Greifswald
Position
  • Head of Department

Publications

Publications (266)
Article
The parasitic deutonymphs of hypoderatid mites live within the subcutaneous layer of their avian hosts, where they become greatly engorged despite not having functional mouthparts. The method by which they take up nutrients has been mysterious up to now. Here, we report on the morphology of hypoderatid deutonymphs using scanning and transmission el...
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The external and internal structures of the notogaster of the enarthronote oribatid mite Heterochthonius gibbus are described, focused on the apodemal and muscular structures involved in the erection of setae. A functional model is suggested to explain the peculiar defensive movements of the setae. This model concerns the structure and deformation...
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The trichobothridium (bothridium and bothridial seta) of the enarthronote mite Heterochthonius gibbus is described using scanning and transmission electron microscopy. The cuticular wall of the bothridium shows three recognizable regions an external (distal) smooth part, a central region with a complex structured wall, and an internal (proximal) sm...
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The genital system of adult males of two species of Arctacaridae, Arctacarus rostratus Evans 1955 and Proarc-tacarus oregonensis Makarova 2003, has been studied. It consists in both species of an unpaired compartment that contains mature sperm. It continues into an unpaired deferent duct that descends ventrad and opens into a large unpaired accesso...
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A new species of Scissuralaelaps (Acari: Laelapidae: Iphiopsidinae), S. huberi sp. nov., is described from the millipede Acladocricus sp. (Spirobolida: Rhinocricidae) in the Philippines. The new species is close to S. bipartitus Ishikawa, which also has males with heavily sclerotised anterior and lateral margins of the peritrematal and metapodal sh...
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Heterozerconidae is a poorly known, early derived mite family belonging to Heterozerconina (Monogynaspida, Gamasida (= Mesostigmata)). The systematic position of the family is still controversial and little is known about the biology and anatomy of the taxon. In this paper, the gross anatomy, ultrastructure and functional morphology of the female r...
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Only about 20 species of microsporidia have been described from mites. All except one species produce typical spores with a long polar filament and a polaroplast. This paper is the first study of an atypical microsporidium infection in a feather mite (Falculifer rostratus). The infection of the pigeon feather mite is restricted to the colon epithel...
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The male genital system of the actinotrichid mite Rhagidia halophila is described and compared with other mites and arachnids. The large testes are composed of germinal and glandular parts and produce numerous small sperm cells. The glandular parts are connected via a testicular bridge. Spermiogenesis occurs in cysts containing spermatids in equal...
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The digestive tract starts at the tip of the infracapitulum, from where the preoral cavity, a tiny channel, leads to the mouth. The mouth opens into the pharynx. A small tube, the canal of the inferior commissure connects this region with the ventral surface , where it opens in the rostral fossette. The pharynx has only dilator muscles, the elastic...
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The fine structure of the ovary of Schizomus palaciosi is studied
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Rhagidia halophila, as other Rhagidiidae, possesses a distinct frontal idiosomatic protuberance, the naso. It bears an unpaired eye (ocellus) that is directed ventrally and consists of four receptor cells provided with numerous rhabdomeric microvilli. The cuticle overlying the microvilli is thin and smooth in contrast to the dorsal cuticle of the n...
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Adult Epicriidae are characterized by stigmata placed on lateral protuberances and the lack of an obvious peritreme. Mites of the genus Epicrius additionally show a pair of further prominent protuberances, which bear glandular pores. Both structures, glandular and stigmata protuberances, are occasionally called “pustules”, and both are investigated...
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The ameroseiid mite Hattena cometis has a male genital system that consists of an unpaired, u-shaped testis and paired deferent ducts leading into an unpaired accessory genital gland and ejaculatory duct. The genital opening is located anteriorly immediately in front of the sternal shield. Spermatogenesis is simple, probably due to the haploid natu...
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Many gamasid mites, mainly of the taxon Dermanyssina, possess a secondarily evolved insemination system that is generally described as occurring in two types, the laelapid and the phytoseiid-type, which are structurally considerably different. Considering that Dermanyssina represent the most recent and most diverse group of gamasid mites, it was ex...
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Most Labidostomatidae bear lateral protuberances called pustules on their idiosoma, which have been considered as "enigmatic" structures. Here, the fine structure of the pustules of Labidostoma luteum is described using scanning and transmission electron microscopy. It is shown that the pustules represent peculiar exocrine glands which extrude thei...
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The ultrastructure and functional adaptations of male chelicerae in Hattena cometis Domrow are discussed. In particular, as in many other gamasid mites, males of Hattena use the chelicerae, modified as gonopods, to transfer the sperm into the female. For such purpose, a slender process extending from the movable digit, the spermatodactyl, is mainly...
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A new species of mites of the family Veigaiidae (Acari, Gamasida) from the USA (Oregon, Mary's Peak) is described and figured.
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Camel spiders (Arachnida: Solifugae) are one of the arachnid groups characterised by a prosomal dorsal shield composed of three distinct elements: the pro-, meso- and metapeltidium. These are associated respectively with prosomal appendages one to four, five, and six. What is less well known, although noted in the historical literature, is that the...
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Heterochthonius gibbus is an oribatid mite which has three eyes located on the prodorsum: an externally unpaired median eye, and a pair of posterolateral eyes. The fine structure of these eyes shows that they consist of a few retinula cells bearing rhabdomeric microvilli. The median eye has two small retinas that are inverted with respect to the cu...
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Oribatida are one of the main groups of Acari comprising mostly important decomposers in soils. Most species are particle feeders, an exceptional mode of nutrition in Arachnida. Hence, their feeding organs, the gnathosoma, are of special functional interest. We studied nearly all components using scanning and transmission electron microscopies as w...
Article
Oribatida are one of the main groups of Acari comprising mostly important decomposers in soils. Most species are particle feeders, an exceptional mode of nutrition in Arachnida. Hence, their feeding organs, the gnathosoma, are of special functional interest. We studied nearly all components using scanning and transmission electron microscopies as w...
Article
Ricinuleid functional mouthparts are the cucullus, the chelicerae, the pedipalps, and the labrum. These structures are movably jointed to the rest of the prosoma, most likely protruded upon hydrostatic hemolymph pressure and retracted by prosomal muscles. Seta-like protrusions from the labrum and the pedipalpal coxae form a sieve-like filter inside...
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The early derivative actinedid Saxidromidae, Saxidromus delamarei, Bovidromus roussouwi, and Rhinodromus lootsi perform indirect spermatophore transfer by means of a peculiar mating behaviour. The anatomy and fine structure of the male genital systems are described and are shown to exhibit the organisation considered to be fundamental in Actinotric...
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Monogyny in spiders culminates in extreme traits, like dramatic male self-sacrifice and emasculation of the male by the female during copulation. Here we show that monogynous males can be highly adapted for this fatal sexual behaviour. Dwarf males of the one-palped theridiid spider Tidarren argo, which are cannibalised immediately after the inserti...
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The present study reveals, based on video-recording, that Epicriidae are predators using their long forelegs provided with a number of long clubbed setae for the capture of small arthropods. The mite walks slowly with raised and probing forelegs. Upon contact with a small isotomid springtail, the forelegs rapidly touch the prey with the tips of the...
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Solifuges are voracious and fast predators. Once having captured a prey item, mostly small arthropods or even small vertebrates, they start feeding on their prey by constant chewing movements with their huge chelicerae. At the same time, they squeeze out the soft tissue that passes the anterior lattice-like part of the mouthparts. The digestion of...
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The cheyletid family includes more than 370 predatory and parasitic species. According to their feeding habit, some are involved in the integrated pest management of stored food, while other species are parasitic both of men and domestic animals. They all suck up liquid food after piercing tissues with their mouthparts showing peculiar adaptations...
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Males of Parasitina and Dermanyssina (Gamasida=Mesostigmata) have chelicerae modified to function as gonopods. The slit-like spermatotreme in the movable digit of the chela in males of Parasitina was studied in three species: in Pergamasus quisquiliarum and Holoparasitus sp. a rather simple slit is indeed present, whereas in Vulgarogamasus kraepeli...
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Effects of starvation on gravid females of Neoseiulus californicus were investigated at 20°C and 85% RH. When females that had been reared with abundant prey were swapped, just after laying their first egg, to conditions without any prey and water, they laid 1.8 eggs and survived for 4.3 days. In the body of well-fed females, an egg with eggshell a...
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Due to their relative rareness and restricted distribution, little is known about the ultrastructure of ricinuleids. In particular, sense organs have not been the subject of electron microscopic research until now. Ricinuleids use their forelegs to explore their surroundings with tentative movements. The distal tarsomeres of legs I and II of two ca...
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The laterally positioned eyes of stylocellid mite harvestmen are simple ocelli composed of a uniconvex cuticular lens, a lentigen layer, a retina, and a layer of pigment cells. Basal laminae separate the lentigen layer (preretinal membrane) and the pigment layer (postretinal membrane) from the retina. The retina is composed of retinular cells and g...
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The Oogenesis and ovary ultrastructure in Psedocellus boneti (Arachnida: Ricinulei) as studied.
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The ultrastructure of spermatozoa is a widely accepted source of characters for phylogenetic studies. In this study the fine structure of sperm cells of representatives of six different New and Old World families (Ammotrechidae, Daesiidae, Eremobatidae, Galeodidae, Karschiidae, Solpugidae) of solifuges (Arachnida, Solifugae) were investigated in or...
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At present, little is known about the biology of Heterozerconidae (Heterozerconina), a very interesting family of gamasid mites. They are podospermic with males having the genital orifice in pre-sternal position and with a sperm transfer process on the chelicerae. This spermatodactyl arises near the basal region of the fixed digit and seems to have...
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We describe one new feather mite species Coraciacarus muellermotzfeldi sp. nov. (Acari, Astigmata) found as dried corpses on the feathers of the museum skin of the huia Heteralocha acutirostris (Gould, 183718. Gould , J. 1837. A synopsis of the birds of Australia, and the adjacent islands, Vol. I, London: Gould. 11 p1. View all references) (Passer...
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The gnathosoma is considered by most authors as the main constitutive character of a monophylum Acari. However, this has been questioned due to fundamental differences regarding its morphology in Anactinotrichida (=Parasitiformes s.l.) and Actinotrichida (=Acariformes). A key character which might indicate homology is represented by stout cuticular...
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Ricinulei possess movable, slender pedipalps with small chelae. When ricinuleids walk, they occasionally touch the soil surface with the tips of their pedipalps. This behavior is similar to the exploration movements they perform with their elongated second legs. We studied the distal areas of the pedipalps of the cavernicolous Mexican species Pseud...
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Solifugae possess an evertable, adhesive pedipalpal organ (suctorial organ) at the tip of the distal tarsus of each pedipalp that is unique among arachnids. When inverted inside the pedipalp, the suctorial organ is covered with two cuticular lips, a dorsal upper lip and a ventral lower lip, but it can be protruded rapidly in order to facilitate gra...
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The ultrastructure of sperm cells of representatives of all superfamilies of Hydrachnidia except Stygothrombioidea is described. The sperm are aflagellate cells with magnitudes reaching 1.3 μm up to 6 μm. They are mostly oval cells, but some show an irregular shape. All investigated mites have an acrosomal complex which is composed of an acrosomal...
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Sensory structures in the chelicerae of Pseudocellus pearsei (Chamberlin & Ivie, 1938) (Ricinulei, Arachnida) were studie under light and scanning electro microscope
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The laterally positioned eyes of stylocellid mite harvestmen are simple ocelli composed of a uniconvex cuticular lens, a lentigen layer, a retina, and a layer of pigment cells. Basal laminae separate the lentigen layer (preretinal membrane) and the pigment layer (postretinal membrane) from the retina. The retina is composed of retinular cells and g...
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The gut of the mite Acarus siro is characterized on the ultrastructural level. It consists of the foregut (pharynx, esophagus), midgut (ventriculus, caeca, colon, intercolon, postcolonic diverticula, postcolon), and hindgut (anal atrium). The gut wall is formed by a single-layered epithelium; only regenerative cells are located basally and these ha...
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Mites and ticks can be divided into two well-defined clades, Anactinotrichida and Actinotrichida, for which a recent work formalized a suite of putative autapomorphies and reciprocal differences. Whether they are sister-taxa – forming a monophyletic Acari – is more controversial. Earlier supporters of two independent origins for mites largely faile...
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Ultrastructural details of spermiogenesis, spermatozoa and the spermatophore of the early derived actinedid mite Saxidromus delamarei are described. Spermatids and mature sperm cells are provided with up to four acrosomal complexes and nuclei derivatives (chromatin bodies). Due to this reason, the sperm cells may be classified as synspermia, a sper...
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Brevipalpus (Acari: Tenuipalpidae) mites are important pests on a variety of host plant species. The mites damage their hosts directly by feeding and some species also serve as vectors of plant viruses. Among more than 200 described Brevipalpus species, three are recognized as vectors of plant viruses: B. phoenicis, B. californicus and B. obovatus....