Complex copulatory behavior and the proximate effect of genital and body size differences on mechanical reproductive isolation in the millipede genus Parafontaria

The role of species-specific genitalia in reproductive isolation is unclear. Males of the millipede genus Parafontaria use gonopods (modified eighth legs) charged with sperm from the genital openings of the second legs as intromittent organs. Males perform both preliminary and true intromission during mating. During preliminary intromission, a male attempts to insert his gonopods into the female genitalia before charging the gonopods with sperm. If this intromission is completed, it is followed by the ejaculation of sperm to the gonopods and true intromission for insemination. In two sympatric species of Parafontaria that lack effective precopulatory isolation, copulation was terminated without insemination because of preliminary intromission failure caused by mismatched genital and body sizes. Thus, mechanical isolation between these sympatric species resulted from morphological differentiation mediated by the obligatory preliminary intromission. These findings demonstrate the proximate importance of genital and body size differences for reproductive isolation within this genus of millipede.     

Segmentation of the millipede trunk as suggested by a homeotic mutant with six extra pairs of gonopods

Background

The mismatch between dorsal and ventral trunk features along the millipede trunk was long a subject of controversy, largely resting on alternative interpretations of segmentation. Most models of arthropod segmentation presuppose a strict sequential antero-posterior specification of trunk segments, whereas alternative models involve the early delineation of a limited number of ‘primary segments’ followed by their sequential stereotypic subdivision into 2ⁿ definitive segments. The ‘primary segments’ should be intended as units identified by molecular markers, rather than as overt morphological entities. Two predictions were suggested to test the plausibility of multiple-duplication models of segmentation: first, a specific pattern of evolvability of segment number in those arthropod clades in which segment number is not fixed (e.g., epimorphic centipedes and millipedes); second, the occurrence of discrete multisegmental patterns due to early, initially contiguous positional markers.

Results

We describe a unique case of a homeotic millipede with 6 extra pairs of ectopic gonopods replacing walking legs on rings 8 (leg-pairs 10-11), 15 (leg-pairs 24-25) and 16 (leg-pairs 26-27); we discuss the segmental distribution of these appendages in the framework of alternative models of segmentation and present an interpretation of the origin of the distribution of the additional gonopods. The anterior set of contiguous gonopods (those normally occurring on ring 7 plus the first set of ectopic ones on ring 8) is reiterated by the posterior set (on rings 15-16) after exactly 16 leg positions along the AP body axis. This suggests that a body section including 16 leg pairs could be a module deriving from 4 cycles of regular binary splitting of an embryonic ‘primary segment’.

Conclusions

A very likely early determination of the sites of the future metamorphosis of walking legs into gonopods and a segmentation process according to the multiplicative model may provide a detailed explanation for the distribution of the extra gonopods in the homeotic specimen. The hypothesized steps of segmentation are similar in both a normal and the studied homeotic specimen. The difference between them would consist in the size of the embryonic trunk region endowed with a positional marker whose presence will later determine the replacement of walking legs by gonopods.     

Morphological phylogenetics of the sea spiders (Arthropoda: Pycnogonida)

Pycnogonids or sea spiders are a group of marine arthropods whose relations to the chelicerates have been an issue of controversy. Higher-level phylogenetic relationships among the lineages of sea spiders are investigated using 36 morphological characters from 37 species from all extant families and a Devonian pycnogonid fossil. This is one of the first attempts to analyze the higher-level relationships of the Pycnogonida using cladistic techniques. Character homoplasy (implied weights) is taken into account to construct a polytomous, most-parsimonious tree in which two major clades within Pycnogonida are obtained. Clade A includes Ammotheidae paraphyletic with Colossendeidae, Austrodecidae and Rhynchothoracidae, and clade B is formed by Nymphonidae, Callipallenidae (apparently paraphyletic), Pycnogonidae and Phoxichilidiidae. The analysis of equally weighted data is presented and helps to identify those characters less consistent. The reduction of the chelifores, palps and ovigers — shown independently within each of the clades as parallel evolution events — challenges the assumption of a gradual mode of reduction within the group, according to analysis of unordered vs ordered characters. Most of the phylogenetic affinities proposed here are compatible with traditional classifications. However, traditional taxonomic characters need to be complemented by sets of anatomical, molecular and developmental data, among others, to produce more robust phylogenetic hypotheses on the higher- and lower-level relationships of the sea spiders.     

The eunuch phenomenon: adaptive evolution of genital emasculation in sexually dimorphic spiders

Under natural and sexual selection traits often evolve that secure paternity or maternity through self‐sacrifice to predators, rivals, offspring, or partners. Emasculation—males removing their genitals—is an unusual example of such behaviours. Known only in insects and spiders, the phenomenon's adaptiveness is difficult to explain, yet its repeated origins and association with sexual size dimorphism (SSD) and sexual cannibalism suggest an adaptive significance. In spiders, emasculation of paired male sperm‐transferring organs — secondary genitals — (hereafter, palps), results in ‘eunuchs’. This behaviour has been hypothesized to be adaptive because (i) males plug female genitals with their severed palps (plugging hypothesis), (ii) males remove their palps to become better fighters in male–male contests (better‐fighter hypothesis), perhaps reaching higher agility due to reduced total body mass (gloves‐off hypothesis), and (iii) males achieve prolonged sperm transfer through severed genitals (remote‐copulation hypothesis). Prior research has provided evidence in support of these hypotheses in some orb‐weaving spiders but these explanations are far from general. Seeking broad macroevolutionary patterns of spider emasculation, we review the known occurrences, weigh the evidence in support of the hypotheses in each known case, and redefine more precisely the particular cases of emasculation depending on its timing in relation to maturation and mating: ‘pre‐maturation’, ‘mating’, and ‘post‐mating’. We use a genus‐level spider phylogeny to explore emasculation evolution and to investigate potential evolutionary linkage between emasculation, SSD, lesser genital damage (embolic breakage), and sexual cannibalism (females consuming their mates). We find a complex pattern of spider emasculation evolution, all cases confined to Araneoidea: emasculation evolved at least five and up to 11 times, was lost at least four times, and became further modified at least once. We also find emasculation, as well as lesser genital damage and sexual cannibalism, to be significantly associated with SSD. These behavioural and morphological traits thus likely co‐evolve in spiders. Emasculation can be seen as an extreme form of genital mutilation, or even a terminal investment strategy linked to the evolution of monogyny. However, as different emasculation cases in araneoid spiders are neither homologous nor biologically identical, and may or may not serve as paternity protection, the direct link to monogyny is not clear cut. Understanding better the phylogenetic patterns of emasculation and its constituent morphologies and behaviours, a clearer picture of the intricate interplay of natural and sexual selection may arise. With the here improved evolutionary resolution of spider eunuch behaviour, we can more specifically tie the evidence from adaptive hypotheses to independent cases, and propose promising avenues for further research of spider eunuchs, and of the evolution of monogyny.     

Additional moults into 'elongatus' males in laboratory-reared Polydesmus angustus Latzel, 1884 (Diplopoda, Polydesmida, Polydesmidae) - implications for taxonomy

The number of stadia during post-embryonic development is supposed to be fixed in most species of the millipede order Polydesmida. For the first time since 1928, additional moults were observed in two males of Polydesmus angustus Latzel, 1884 reared in the laboratory. These 'elongatus' males sensu Verhoeff reached stadium IX instead of stadium VIII, with addition of a further podous ring (32 pairs of legs). One male had well-developed gonopods at stadium VIII, which regressed at stadium IX; the other had no gonopods at stadium VIII, which developed at stadium IX. The two cases correspond to the 'regressionis' and 'progressionis' forms described by Verhoeff in Polydesmus complanatus (Linnaeus, 1761), which confirms entirely his results. Additional moults appear to be associated with small body sizes and possible underlying mechanisms are discussed. Comparisons between millipede orders indicate that post-embryonic development is less strictly canalized in Polydesmida than in Chordeumatida. This implies that the adult number of body rings is of limited taxonomic value in Polydesmida and should not be viewed as a character of generic importance.     

Homologies in phylogenetic analyses—concept and tests

Analyzing morphological characters in a phylogenetic context comprises two steps, character analysis and cladistic analysis, which are equivalent to two independent tests for hypotheses on homology. The concept of homology concerns comparable parts of the same or different organisms if their correspondences are the consequence of the same genetic or epigenetic information, and consequently of the same origin. The concept of homology is more inclusive than the character concept. Characters are seen as parts of transformation series. In the first step of morphological character analyses correspondences and non-correspondences between two characters are analyzed. A range of different examination methods and accurate study contribute to the severity of test. The hypothesis that two characters are homologous is corroborated if the correspondences outweigh the non-correspondences because the non-correspondences contradict the homology hypothesis whereas the correspondences contradict the analogy hypothesis. Complex characters possess a higher empirical content than less complex characters because they are more severely testable. The cladistic analysis tests characters against other characters which have all passed the first test. Characters which are congruent with the most parsimonious topology are further corroborated; incongruent characters are not seen as ‘falsified’ but as not further corroborated and subject to re-analysis. To test both homologies and topologies repeatedly is consistent with Popperian testability, and it is in such cycles of research that hypotheses will be critically re-evaluated.     

Lack of morphological coevolution between male forelegs and female wings in Themira (Sepsidae: Diptera: Insecta)

The complex, species-specific foreleg armature in males of the genus Themira (Diptera: Sepsidae) provides an ideal system for testing competing hypotheses for the evolution of sexually dimorphic character divergence. In sepsid flies, the male holds onto the female by clasping her wing base with his modified forelegs. In the present study, we document the male leg and the female wing morphology using scanning electron microscopy and confocal microscopy. We use a phylogenetic tree for Themira to reconstruct male foreleg and female wing evolution and demonstrate that the male legs have evolved elaborate structures with little or no corresponding changes in wing morphology. This lack of interspecific variation in female wings is not in agreement with the hypothesis of a morphological 'evolutionary arms race' between males and females. However, there is also no evidence for sex-specific wing differences in sensory organs on the wing base that may explain how females could assess males according to Eberhard's 'cryptic female choice' hypothesis. Finally, our study reveals the function of several novel morphological clasping structures and documents that the male foreleg characters in Themira are highly homoplastic. Male forelegs in two clades evolve considerably faster than in other species or clades. These two clades include Themira superba and Themira leachi , species that have some of the most dramatically modified forelegs known in Diptera.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 227–238.     

Central nervous system and sense organs, with special reference to photoreceptor-like sensory elements, in Polygordius appendiculatus (Annelida), an interstitial polychaete with uncertain phylogenetic affinities

Abstract. The phylogenetic position of Polygordius is still pending; relationships with either Opheliidae or with Saccocirrus are the most favored hypotheses. The present study of Polygordius appendiculatus was designed to look for morphological characters supporting either of these two hypotheses. The homology of the anterior appendages, and the structure of the central nervous system and nuchal organ all required clarification; we also examined whether photoreceptor‐like sense organs exist in adults. From their innervation pattern, it is likely that the anterior appendages represent palps. They lack structures typical of palps in Canalipalpata, such as musculature and coelomic cavities, which would be expected in the case of a saccocirrid relationship. Thirteen photoreceptor‐like sense organs were found in front of the brain, the only structures resembling photoreceptors in adults of P. appendiculatus. These multicellular sense organs comprise a supportive cell and several sensory cells enclosing an extracellular cavity. There are three different types of sensory cells: one rhabdomeric and two ciliary. These sensory cells are combined differently into three forms of sense organ: the most frequent uses all three types of sensory cells, the second possesses one rhabdomeric and one ciliary cell type, and the third has two types of ciliary sensory cells. Whereas similar sensory cells are frequently found in various polychaetes, their combination in one sensory organ is unique to Polygordius and is considered to represent an autapomorphy. The nuchal organs exhibit features typical of polychaetes; there are no specific features in common with Saccocirrus. Instead, the covering structures show obvious similarities to Opheliidae, as can also be found in the central nervous system. Altogether, the current observations do not contradict a relationship with opheliids but provide no evidence of a relationship with Saccocirrus as has been found in certain molecular analyses, and thus currently leave the phylogenetic position of Polygordius unresolved.     

Systematics of the parasitic wasp genus Yelicones Cameron (Hymenoptera: Braconidae: Rogadinae) and revision of the genus from the New World

Species of the braconid wasp genus Yelicones Cameron from North, Central and South America are revised and the first phylogenetic analysis of the world Yelicones fauna is presented. The results are considered from a biogeographical perspective and the effect of including and excluding colour characters is investigated. One hundred and twenty‐four species from throughout the world are recognised. Eighty‐five species are from the New World, 63 of which are new. A fully illustrated key to New World species is provided. A total of 116 characters were scored, of which 86 were morphological and 30 were based on the wasps’ colour pattern. All analyses show a near perfect diversion between New and Old World species. However, analyses excluding and including colour produced completely opposite results in terms of whether New or Old World species were basal. We found that in our data matrix colour characters performed at least as well as morphological characters in terms of their ensemble retention index, making it difficult to decide which phylogenetic hypotheses is correct. However, consideration of venom apparatus features leads us to prefer the hypotheses placing the New World taxa basally.     

Phylogenetic interrelationships of the barbets (Aves: Capitonidae) and toucans (Aves: Ramphastidae) based on morphology with comparisons to DNA-DNA hybridization

A phylogenetic analysis of the interrelationships of the barbets (Capitonidae) and the toucans (Aves: Ramphastidae, Superfamily Ramphastoidea) is presented. Thirty-two morphological characters from the literature and independent osteological observations were analysed. Character polarity was determined by outgroup comparison to the Picidae, Indicatoridae, Galbulidae, Bucconidae and Coraciiformes. Four alternative phylogenetic hypotheses were compared: (1) the overall most parsimonious morphological phylogeny, (2) the most parsimonious morphological phylogeny in which the capitonids and ramphastids were hypothesized as monophyletic sister groups, and (3) and (4) the most parsimonious hypotheses for the evolution of the morphological characters within two proposed DNA-DNA hybridization phylogenies of the ramphastoids. The analysis focused on the higher level relationships of ramphastids and capitonids and interrelationships among capitonid genera. Two cladistic analyses were performed using 26 phylogenetically informative characters, and the PAUP and CONTREE computer alogorithms. The most parsimonious morphological phylogeny required fewer character changes and had a lower consistency index than any of the alternative hypotheses but congruence between the most parsimonious phylogeny and the second, revised DNA-DNA hybridization hypothesis was very high. Based on these results the monophyly of the Capitonidae is rejected. The ramphastids and the Neotropical capitonids form a well corroborated clade within the pantropical ramphastoid radiation. Neither the African, Asian nor New World capitonids is monophyletic. The genus Trachyphonus is the sister group to all other capitonids and ramphastids. The sister group to the ramphastids is the genus Semnornis. The interrelationships of the Old World capitonids excluding Trachyphonus are not completely resolved by these morphological data but one of the alternative phylogenetic resolutions is presented as a preliminary hypothesis. The clades in this resolved phylogeny are diagnosed and the palaeontology and biogeography of the ramphastoids arc-reviewed in light of this new evidence. A phylogenetic classification is proposed in which the Capitonidae is rejected and the capitonids and ramphastids are placed in seven subfamilies of the Ramphastidae.     

Exclusive Male Egg Care and Determinants of Brooding Success in a Millipede

The evolution of exclusive male parental care is a major and controversial issue in behavioural ecology. Although arthropods practicing paternal care are thought to be key taxa for investigating this issue, few studies have attempted to clarify the selection factors associated with male behaviour and fitness consequences in arthropods. In the millipede Brachycybe nodulosa, males curl their bodies around egg masses on the undersides of decaying logs. Male‐removal experiments in the laboratory strongly suggest that males defend the eggs against fungal infection. Orphaned eggs were soon covered by hyphae and no eggs hatched, whereas almost all eggs brooded by males successfully hatched. The egg‐brooding males showed no aggressive responses when disturbed. Only some mature males bred in the field. Furthermore, the number of eggs brooded varied greatly among the males. Selected generalized linear models revealed that males with a wide seventh body segment, which possesses gonopods (genital legs), tended to succeed in brooding; and males with a wider body also obtained more eggs. Colony attributes had no significant effects on male brooding. We discuss the possible sexual selection mechanisms that could accomplish this pattern of brooding success among male B. nodulosa.     

Arboreallty and morphological evolution in ground beetles (Carabidae: Harpalinae): testing the taxon pulse model

Abstract.— One-third to two-thirds of all tropical carabids, or ground beetles, are arboreal, and evolution of arboreality has been proposed to be a dead end in this group. Many arboreal carabids have unusual morphological features that have been proposed to be adaptations for life on vegetation, including large, hemispheric eyes; an elongated prothorax; long elytra; long legs; bilobed fourth tarsomeres; adhesive setae on tarsi; and pectinate claws. However, correlations between these features and arboreality have not been rigorously tested previously. I examined the evolution of arboreality and morphological features often associated with this habitat in a phylogenetic context. The number and rates of origins and losses of arboreality in carabids in the subfamily Harpalinae were inferred with parsimony and maximum-likelihood on a variety of phylogenetic hypotheses. Correlated evolution in arboreality and morphological characters was tested with concentrated changes tests, maximum-likelihood, and independent contrasts on optimal phylogenies. There is strong evidence that both arboreality and the morphological features examined originated multiple times and can be reversed, and in no case could the hypothesis of equal rates of gains and losses be rejected. Several features are associated with arboreality: adhesive setae on the tarsi, bilobed tarsomeres, and possibly pectinate claws and an elongated prothorax. Bulgy eyes, long legs, and long elytra were not correlated with arboreality and are probably not arboreal adaptations. The evolution of arboreal carabids has not been unidirectional. These beetles have experienced multiple gains and losses of arboreality and the morphological characters commonly associated with the arboreal habitat. The evolutionary process of unidirectional character change may not be as widespread as previously thought and reversal from specialized lifestyles or habitats may be common.     

The phylogeny of charadriiform birds (shorebirds and allies) – reassessing the conflict between morphology and molecules

Multiple molecular analyses provide a congruent and well‐supported phylogeny of the charadriiform family‐level taxa, which conflicts with previous hypotheses based on osteological data. In order to revise the latter and to identify new characters of phylogenetic significance, skeletons of most charadriiform family‐level taxa were examined and 49 characters analysed. Tree topology was sensitive to outgroup choice, but the result of the analysis rooted with Columbidae (doves and pigeons) recovered a monophyletic Scolopaci, Charadrii, and nonturnicid Lari. With regard to the inclusion of Alcidae and Glareolidae in the Lari, the results of the present study are also in better concordance with the new molecular phylogenies than previous analyses of morphological data. Furthermore, for the first time an apomorphy of a clade including Thinocoridae, Pedionomidae, Rostratulidae, and Jacanidae was identified. Inclusion of Turnicidae in the Lari could not be supported, but there is no strong morphological evidence for an alternative placement. Pluvianus shares derived osteological features with the Burhinidae, and its position in the molecular analyses likewise cannot be corroborated with morphological data. Based on the topology of the molecular consensus tree, the ancestral state of selected characters is reconstructed. It is finally noted that recent calibrations of molecular analyses, which indicate an origin of extant charadriiform lineages in the Cretaceous, are based on incorrectly identified fossils. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 916–934.     

Systematic Zoology: Slicing the Gordian Knot with Ockham's Razor

Systematic zoology has undergone a revolution during the past25 years. A major step was in the formulation of an explicitand objective methodology for determining phylogenetic relationshipsthat results in testable hypotheses. The methodology of phylogeneticsystematics has spawned vicariance biogeography and is applicablenot only to traditional morphological characters but to newkinds of systematic characters. Innovative biochemical, cytogenetic,and developmental approaches to phylogenetic relationships havebroadened the scope of systematic zoology. This diversity increasesthe potential for generating and testing hypotheses of phylogeneticrelationships and temporal evolution.     

Comparative histology of the vaginal–cloacal region in Squamata and its phylogenetic implications

We described the histology and morphology of the vaginal–cloacal region in 18 species from 12 Squamata families. This comparative study revealed a wide variation in the cloacal morphology. Fifteen morphological characters were considered to be primary homology hypotheses and were optimized over the topology derived from the parsimony analysis of the available soft morphological evidence, including the characters described in this study. The synapomorphies optimized for Squamata are bifid urodaeum, common urodaeal cavity with similar histological features of the urodaeal horns, and presence of glands in the anterior urodaeum; for Scleroglossa the synapomorphy is the lateral position of the vaginal intrusion into the anterior urodaeal chamber, for Nyctisaura + Scincomorpha the synapomorphy is the presence of a bifid posterior urodaeum; and for Xantusidae + Annulata it is the presence of simple glands in the anterior urodaeum. The central position of the vaginal intrusion into the urodaeal chamber and the intraepithelial position of the glandular unit in the anterior urodaeum behave as autapomorphies for Iguanidae. This study contributes evidence that defines the relationships within Scleroglossa. Cloacal features provide interesting information that is useful as a source of morphological characters for phylogenetic studies in Squamata.     

How our view of animal phylogeny was reshaped by molecular approaches: lessons learned

In the late 1980s, researchers began applying molecular sequencing tools to questions of deep animal phylogeny. These advances in sequencing were accompanied with improvements in computation and phylogenetic methods, and served to significantly reshape our understanding of metazoan evolution. Prior to this time, researchers asserted phylogenetic hypotheses based on their experience with taxa and to some degree, their authority. Molecular phylogenetic tools provided discrete methods and objective characters for reconstructing phylogeny. Nonetheless, major changes to widely accepted views, such as animal phylogeny, take time to be accepted. Development and acceptance of our current understanding of animal evolution occurred in three main phases: initial hypotheses based on 18S data, confirmation with additional molecular markers, and continued refinement with phylogenomics. With the advent of ideas such as Lophotrochozoa and Ecdysozoa, flaws in the traditional view became apparent. We now understand that complex morphological and embryological features (e.g., segmentation, coelom formation, development of body cavities) are much more evolutionarily plastic than previously recognized. Here, I explore how the transition from the traditional to the modern phylogenetic understanding of animal phylogeny occurred and examine some implications of this change in understanding. As the field moves forward, the utility of morphological and embryological characters for reconstruction of deep animal phylogeny should be discouraged. Instead, these characters should be interpreted in the light of independent phylogeny.     

Pigmented eyes,photoreceptor‐like sense organs and central nervous system in the polychaete Scoloplos armiger (Orbiniidae,Annelida) and their phylogenetic importance

The phylogenetic position of Orbiniidae within Annelida is unresolved. Conflicting hypotheses place them either in a basal taxon Scolecida, close to Spionida, or in a basal position in Aciculata. Because Aciculata have a specific type of eye, the photoreceptive organs in the orbiniid Scoloplos armiger were investigated to test these phylogenetic hypotheses. Two different types of prostomial photoreceptor‐like sense organs were found in juveniles and one additional in subadults. In juveniles there are four ciliary photoreceptor‐like phaosomes with unbranched cilia and two pigmented eyes. The paired pigmented eyes lie beside the brain above the circumoesophageal connectives. Each consists of one pigmented cell, one unpigmented supportive cell and three everse rhabdomeric sensory cells with vestigial cilia. During development the number of phaosomes increases considerably and numerous unpigmented sense organs appear consisting of one rhabdomeric photoreceptor cell and one supportive cell. The development and morphology of the pigmented eyes of S. armiger suggest that they represent miniaturized eyes of the phyllodocidan type of adult eye rather than persisting larval eyes resulting in small inverse eyes typical of Scolecida. Moreover, the structure of the brain indicates a loss of the palps. Hence, a closer relationship of Orbiniidae to Phyllodocida is indicated. Due to a still extensive lack of ultrastructural data among polychaetes this conclusion cannot be corroborated by considering the structure of the unpigmented ciliary and rhabdomeric photoreceptor‐like sense organs. J. Morphol., 2009. © 2009 Wiley‐Liss, Inc.     

Differential diagnosis between Tunga penetrans (L., 1758) and T. trimamillata Pampiglione et al., 2002 (Insecta, Siphonaptera), the two species of the genus Tunga parasitic in man

Of the ten currently known species of sand fleas, only two, Tunga penetrans and Tunga trimamillata, are known to be parasites of man, besides other warm blooded animals, most of which are peridomestic. The hosts of the other eight are limited to a few genera of wild mammals. T. trimamillata was only recently identified and differentiated from T. penetrans by features of the gravid female phase. In the present paper the different morphological characters of both for non-gravid females and males of the two species are described. In the non-gravid-females the distinguishing characters are: a) differences in the length of the first two segments of the maxillary palps (the first is the longest in T. trimamillata, whereas the second is the longest in T. penetrans), this feature is associated with another character i.e. the presence of short, thick spines in addition to the bristles on the surface of the segments only in T. trimamillata; b) the presence, only in T. trimamillata, of a row of spines on the antero-medial surface of the libia of the 3rd pair of legs; c) the last abdominal spiracle protrudes in T. trimamillata but not in T. penetrans; d) the hood of the hilla in spermatheca is surrounded by a papilla only in T. penetrans. The following morphological characters differentiate males of T. trimamillata and T. penetrans: a) T. trimamillata has a row of spines on the antero-medial surface of the tibia of the 3rd pair of legs; b) the diameter of the abdominal spiracles of T. trimamillata is smaller than that of T. penetrans and the edges of the spiracles are more regular; c) the claspers and aedeagus of T. trimamillata are shorter than those of T. penetrans; d) the profile of the oedeagal apodeme differs between the two species.     

On the ground pattern of Annelida

Annelida, traditionally divided into Polychaeta and Clitellata, are characterized by serial division of their body into numerous similar structures, the segments. In addition, there is a non-segmental part at the front end, the prostomium, and one at the back, the pygidium. New segments develop in a prepygidial proliferation zone. Each segment contains four groups of chaetae made up of β-chitin, a pair of coelomic cavities separated by mesenteries, and septa. The nervous system is a rope-ladder-like ventral nerve cord with a dorsal brain in the prostomium. For the last stem species a trochophore larva and a benthic adult are commonly postulated. There are two conflicting hypotheses describing the systematization of Annelida: the first postulates a sister-group relationship of Polychaeta and Clitellata, the second sees Clitellata as a highly derived taxon forming a subordinate taxon within the polychaetes which, consequently, are regarded as paraphyletic. Depending on the hypothesis, different characters have to be postulated for the stem species of Annelida. Besides segmentation other characters such as nuchal organs, palps and antennae, body wall musculature, cuticle, parapodia as well as structure of the central nervous system and the foregut play an important role in this discussion. Here, the different characters and character states are critically reviewed and analyzed with respect to morphology and function. The consequences for systematization of their phylogenetic interpretation as autapomorphies, synapomorphies or plesiomorphies are outlined. The resulting hypotheses are compared with those relying on molecular data sets.     

Cladistic analysis of the Sepsidae (Cyclorrhapha: Diptera) based on a comparative scanning electron microscopic study of larvae

The result of a phylogenetic analysis of the Sepsidae based on larval characters is presented. It is shown that cyclorrhaphan larvae can be as rich a source of characters as Nematocera immatures when investigated using an SEM. The cladistic analysis comprised fifty-two species in sixteen genera of the Sepsidae and five outgroup species and used fifty-seven morphological characters. It found seven parsimonious trees which only differed with respect to the arrangement of some species within the genus Themira. The basal dichotomies of the phylogenetic trees are particularly well supported, indicating the conservative nature of larval characters. Orygma is confirmed as the sister group of all the remaining sepsids, the Sepsinae. There is good larval evidence that Ortalischema is the sister group of all remaining Sepsinae and that the Toxopodinae constitute an early radiation within the Sepsidae. According to larval data, some genera are paraphyletic ( Themira, Palaeosepsis ), but adult characters appear to contradict these findings. Among the traditionally recognized higher taxa within the Sepsidae, Hennig's Themira species-group and Steysbal's Sepsini have to be rejected as polyphyletic. However, Hennig's Sepsis species-group is confirmed as monophyletic and will probably constitute one major element of a future phylogenetic system of the Sepsidae. States of the strongly modified fore-legs of some adult sepsid males are mapped onto the phylogenetic tree, largely confirming Šulc's ideas about the evolution of these features. The origin and evolution of male sternites with brushes and a gland on the tibiae of the males ('osmeterium') are discussed. Whereas adult characters point to a sister-group relationship between the Sepsidae and the Ropalomeridae, larval characters appear to indicate a sister-group relationship between the Coelopidae and the Sepsidae. The evidence for both hypotheses is critically evaluated.