Sclerites in different tissues of Mediterranean Echinodermata

The presence of sclerites in different mesodermal tissues was studied in thirteen species of Mediterranean echinoderms representing the five living classes. In the species of Asteroidea and Crinoidea examined, sclerites were present only in specific tissues. In the species of Ophiuroidea and, especially, Echinoidea and Holothuroidea examined, sclerites were present in almost every tissue, but with considerable variation among species and tissues. Data on sclerite shape, size, and relative abundance (measured as tissue abundance) are presented. The data support the possible functional role of sclerites as reinforcing structures, as well as their possible use as taxonomic characters. Finally, the need of more studies to elucidate the ontogenetic and phylogenetic implications of sclerites is discussed.     

Paedomorphosis and heterochrony in the origin and evolution of the class holothuroidea

The role of paedomorphosis as a particular case of heterochrony in the origin and evolution of the class Holothuroidea is analyzed. It is shown that holothurians are characterized by the presence of some paedomorphic characters (reduced skeleton, absence of an axial complex in the shape of a morphologically integrated structure, single gonad with one gonopore). In many members of the subclass Holothuriacea, sclerites of the body wall are arranged in two layers. Sclerites of the deeper layer develop as a perforated plate and correspond to the skeletal elements forming in other echinoderms the body skeleton, for example, the test of sea urchins. Sclerites of the superficial layer frequently look like various tables, develop like spines of other echinoderm classes, in particular, juvenile tetraradiate spines of sea urchins, and correspond to spines of other classes of Echinodermata. Ontogenetic changes at the stage of five first tentacles resulted in interruption at an early stage of the development with the catastrophic metamorphosis, which is typical for other Eleutherozoa. The ontogeny of holothurians acquired the evolutive (gradual) character; the adult body began to develop on the basis of the larval body and larval tissues were partially included in the body of adult holothurians. As a result, the place and developmental pattern of the radial complex of organs changed and heterochrony in the development of characters concerned with different coordination chains intensified; therefore, the modern body plan of holothurians was formed. The processes of paedomorphosis and heterochrony played an important role not only in the origin and formation of the class Holothuroidea, but also during its evolution. Paedomorphic processes became rather important in the evolution of the order Synaptida. Paedomorphic features are particularly prominent in the structure of small interstitial forms. In some holothurians, the paedomorphosis resulted in the change in relationships between symmetry planes. The bilateral plane of symmetry of these holothurians coincide with the plane of symmetry 2–1–2, which is positioned in the majority of holothurians at about 72° to the bilateral plane. Independently, but frequently in parallel, the intestinal loop disappeared, so that the gut became straight and suspended on mediodorsal mesentery almost throughout its extent. The combination of these processes in holothurians of the order Synaptida resulted in the formation of almost complete pentaradially bilateral symmetry.     

System of the class Holothuroidea

Various interpretations of the holothurian system and phylogeny are critically reviewed and the main characters that form the basis of the existing systematics of this group are analyzed. A system of holothurians based on thorough analysis of their morphology and anatomy is proposed. Four subclasses are recognized in the class Holothuroidea: Arthrochirotacea, Synaptacea, Elpidiacea, and Holothuriacea. The subclass Arthrochirotacea includes the extinct Paleozoic order Arthrochirotida. The subclass Synaptacea includes the order Synaptida with two suborders and three families. The subclass Elpidiacea includes the order Elasipodida with four families. The subclass Holothuriacea includes four orders: Aspidochirotida with five families; Dendrochirotida with 15 families (14 extant and one extinct); Molpadiida with three families; Gephyrothuriida with one family and two genera Gephyrothuria and Hadalothuria. The order Gephyrothuriida is re-established. The order Dactylochirotida Pawson et Fell, 1965 is synonymized under the order Dendrochirotida. A new suborder Cucumariina and new family Mesothuriidae are described. The family Vaneyellidae is synonymized under the family Cucumariidae. Four subfamilies are classified as families: Cladolabidae, Sclerothyonidae, Monilipsolidae, and Thyonidiidae.     

New investigation technique for thoracic sclerites of mosquitoes (Diptera, Culicidae) for the correct identification of genera and species

A new technique for studying the external morphology of thoracic sclerites of mosquitoes (Diptera: Culicidae) was developed. According to this method, the shape of sclerites and the position of setae and scales can be examined using SEM or light microscopy even in cases when setae or scales have been lost. The method can be recommended for the damaged material which is often obtained during sampling. The bases of setae usually exceed 100 μm in diameter and thus differ significantly from the bases of scales which are about 30 μm in diameter. Analysis of the structure of sclerites and the arrangement of setae and scales on them in different specimens of one species may reveal intraspecific variation of this character complex. Comparison of species from different genera of the family Culicidae, as well as comparison of closely related species, will probably help to estimate the diagnostic value of thoracic sclerites as morphological characters.     

Critical Reexamination of Palynological Characters Used to Delimit Asclepiadaceae in Comparison to the Molecular Phylogeny Obtained from PlastidmatK Sequences

The family Asclepiadaceae (Dicotyledones) was created by Brown in 1810 by splitting in two the family Apocynaceae of Jussieu established in 1789. The morphological characters used to make this distinction were mainly palynological, such as presence of tetrads or pollinia and number and orientation of pollinia. Those characters, still used in higher taxonomic delimitation (families, subfamilies, and tribes), are here critically reexamined and compared to a molecular phylogeny obtained with one of the more variable plastid genes (matK) of 46 species in the order Gentianales. In this molecular phylogeny, Asclepiadaceae form a monophyletic group derived from within Apocynaceae. Each of the subfamilies of Asclepiadaceae is monophyletic and based on reliable palynological characters, but palynological characters are not useful to delimit tribes of the subfamily Asclepiadoideae. Based on the molecular data, these tribes have undergone parallelisms in several reproductive traits.     

Comparison of the neuromuscular systems among actinotroch larvae: systematic and evolutionary implications

A comparative analysis of the larval and presumptive juvenile neuromuscular systems among actinotroch larvae was performed using confocal laser microscopy with probes for F-actin and serotonin. Currently, there are two main categories of larval nervous systems based on the origin of the nerve fibers that innervate the larval tentacles. Characteristics of the serotonergic cells of the larval apical ganglion and juvenile nervous system have remained relatively conserved, but the structure of the secondary (hood) sense organ and the juvenile tentacles has diversified among species. Differences in larval musculature are mainly associated with differences in hood morphology. The presumptive, juvenile neuromuscular system is either integrated or separated from that of the larva based on the origin of the juvenile tentacles. Among species, the juvenile tentacles are made by remodeling the larval tentacles, developed from a basal tentacular thickening, or developed as a completely separate set in the larva. Differentiation of the neuromuscular structures of the juvenile tentacles is more diverse than their outward morphological characteristics would suggest. Importance of these larval characters is discussed in terms of current problems that exist within phoronid systematics. Evolutionary implications of these morphological characters are discussed among the phoronids, brachiopods, and related bilaterians. Overall, the integration or separation of larval and juvenile neuromuscular characters may yield insights into the evolution of lophotrochozoan body plans.     

Present status ofArisaema systematics

For an understanding of the systematics ofArisaema (Araceae), the history of infrageneric classification systems and recent studies of taxonomic characters ofArisaema are reviewed. Based on morphological information, a cladistic analysis is attempted. The most parsimonious cladgrams, with 32 steps and a consitency index of 0.69, involve assumed parallelisms and reversals in several characters. Ongoing molecular systematic studies are testing the proposed systematics.     

Morphological hemiplasies in cladistic studies of phylogeny,with examples from birds

Cladograms usually include many evolutionary reversions, parallelisms, and convergences united under the term homoplasy. Recently, it has become evident that molecular traits that look like homoplasy may be in fact true homologies. The processes of independent sorting of genes, which provide the basis of these events, were recently termed hemiplasy. The present study demonstrates theoretical possibility of independent manifestation of true homology (synapomorphy) in remote lineages of phylogenetic tree, as morphological characters are analyzed; this phenomenon is similar in manifestation (but not in nature) to hemiplasy. In the case of “morphological hemiplasy,” characters that appeared only once in evolution may formally be treated by a cladist as parallelisms, since they occur in remote lineages of phylogenetic tree. It is proposed that “morphological hemiplasy” is responsible for a number of uncertain cases in avian phylogeny. Examples are provided by the ducklike bill in Paleogene Presbyornithidae and extant Anatidae and Anseranatidae (Anseriformes), the apomorphic structure of the flying apparatus in Paleogene Jungornithidae (Apodiformes) and extant Trochilidae, and “independent” development of a highly-modified zygodactyl foot in Zygodactylidae and Pici.     

Phylogenetic studies of the subgenus Nialoe (s. lat.) (Coleoptera, Carabidae, Genus Pterostichus), part 1: Homology of the component parts of male genitalia and higher phylogeny

A phylogenetic hypothesis of the subgenus Nialoe (s. lat.) of genus Pterostichus is proposed based on a cladistic analysis of seventeen morphological characters. Through comparative studies of the sclerites on the endophallus of male genitalia, it became apparent that the arrangement of these sclerites reflects seven different origins. The results show that Nialoe (s. lat.) is monophyletic and composed of four clades, while some traditional taxa are para- or polyphyletic, and are defined only by symplesiomorphies. Pterostichus (Nialoe) mosaicus sp. nov., which is indispensable for tracing the homology of sclerites in this subgenus, is described.     

Male and female genitalia in some Libyan species of Acrididae (Orthoptera: Acridoidea)

A comparative study of male and female genitalia was carried out in thirty‐seven Libyan species representing twenty genera of the family Acrididae. An attempt has been made to describe and illustrate the different structures, namely, epiphallus, aedeagus, subgenital plate, supra‐anal plate and cerci of the male, and spermatheca, ovipositor, subgenital plate, supra‐anal plate and cerci of the female, in Acridids, with an aim to discover their significance in order to make the identification of genera and species, together with other generic characters, more perfect and convenient. Distinct family characters are shield or bridge‐shaped condition of epiphallus; presence or absence of dorso‐lateral appendices, oval sclerites and lophi on epiphallus; divided, undivided or flexured condition of aedeagus; presence or absence of gonopore process on aedeagus; condition of apical and pre‐apical diverticula of spermatheca; presence or absence of glandular pouches of Cornstock and Kellog on female subgenital plate; and rudimentary or well developed condition of egg‐guide. Stable characters for separating the subfamilies are taken to be presence or absence of ancorae on epiphallus, long or short condition of aedeagal sclerites; elongate, slender or short and broad condition of ovipositor valves: presence or absence of Jannone's organs and setae on posterior margin of female subgenital plate; and shape of diverticula of spermatheca. Useful generic characters are shape of male subgenital plate, supra‐anal plate and cerci, broad or narrow condition of bridge, presence or absence of branch of bridge connecting lophi with bridge of epiphallus; mono‐, bi‐ or tri‐lobate condition of lophi of epiphallus, length and upcurved or downcurved condition of apical valve of aedeagus, shape of posterior margin of female subgenital plate, presence of setae on the whole posterior margin or confined to lateral margins only; and toothed, tuberculate or smooth condition of ovipositor valves, length of the lateral apodeme in relation to the dorsal valves. Specific characters are shape of egg‐guide of female subgenital plate, shape of ovipositor valves and apical tips, shape of male supra‐anal plate and cerci, size of anterior and posterior lobes of lophi of epiphallus, size and shape of ancorae, shape of apical valves of aedeagus; and size of apical and pre‐apical diverticula and presence of protuberance on pre‐apical diverticulum.     

A unique ball-shaped Golgi apparatus in the rat pituitary gonadotrope: its functional implications in relation to the arrangement of the microtubule network

In polarized exocrine cells, the Golgi apparatus is cup-shaped and its convex and concave surfaces are designated as cis and trans faces, functionally confronting the rough endoplasmic reticulum and the cell surface, respectively. To clarify the morphological characteristics of the Golgi apparatus in non-polarized endocrine cells, the investigators immunocytochemically examined its precise architecture in pituitary gonadotropes, especially in relation to the arrangement of the intracellular microtubule network. The Golgi apparatus in the gonadotropes was not cup-shaped but ball-shaped or spherical, and its outer and inner surfaces were the cis and trans faces, respectively. Centrioles were situated at the center of the Golgi apparatus, from which radiating microtubules isotropically extended to the cell periphery through the gaps in the spherical wall of the Golgi stack. The shape of the Golgi apparatus and the arrangement of microtubules demonstrated in the present study could explain the microtubule-dependent movements of tubulovesicular carriers and granules within the gonadotropes. Furthermore, the spherical shape of the Golgi apparatus possibly reflects the highly symmetrical arrangement of microtubule arrays, as well as the poor polarity in the cell surface of pituitary gonadotropes.     

Morphological characters and classification of the subclass Monilifera (Pogonophora) and the problem of evolution of the bridle in pogonophorans

This paper presents the results of the revision of the subclass Monilifera (Pogonophora) based on an analysis of all currently known morphological features. The most important diagnostic characters of Monilifera are the presence of two tentacles without pinnules, a neurotroch on the forepart, a fragmented bridle, a transparent rigid tube, the lack of postannular region, and spermatophores. A few characters are newly proposed for the systematics of Monilifera: the length of tentacles, cephalic lobe, and forepart relative to the forepart diameter, average forepart diameter, paired coelom I, the presence of multicellular glands in the prefrenular region of first segment, the lack of muscular ridges of girdles, unfolded and nonconcave opisthosomal growth zone, teethed opisthosomal setae being arranged in four transverse rows or in a circle on each setigerous segment. The modified and expanded differential diagnoses of subclass Monilifera, order Sclerolinida, family Sclerolinidae, and genus Sclerolinum are given. Archeolinum gen. n. is erected to accommodate all moniliferan species, except for Sclerolinum sibogae Southward, 1961, on the basis of bridle and tube structure, as well as the most important morphometric parameters of forepart. All data on the morphology and evolution of the bridle as one of the most peculiar organs of pogonophorans are systematized. A complete series of transformations of the bridle structure is proposed: from plesiomorphic simple cuticular plaques scattered on the forepart dorsal surface to regular plaques with a thickened edge, ridge, and rodlike bodies. The merging of individual cuticular plaques and the reduction of their membranes resulted in the formation of a fused bridle. However, the traces of rodlike bodies and their derivates (the so-called blocks) can be found in many apomorphic bridles. Finally, total reduction of all elements of the initial cuticular plaque, except the thickened edge, led to the formation of a homogenous bridle, which is characteristic of most pogonophorans.     

Homology as a parsimony problem: a dynamic homology approach for morphological data

The primary data used to reconstruct phylogenies comes organized in the conceptual grid of homology correspondences, and the construction of this theory‐rich grid depends in part on knowledge of relationships. This situation is not satisfactory as a conceptual system, because the evidence is not clearly delimited from the results. I explore the testing of alternative hypotheses of morphological correspondences in a quantitative cladistic context. The varying homology assessments implied by classical criteria of homology (topological equivalence, or position and connections; composition of structures, or commonality in details of construction) can be expressed as regular characters in a cladistic analysis. Doing so provides adequate transformation costs for changes in schemas of correspondences. Correspondences imply evolutionary transformations, and multiple schemas of correspondences can be compared according to the evolutionary transformations that they imply. The method is used to test the correspondences in sclerites of the male copulatory organs of spiders of the subfamily Amaurobioidinae (Arachnida, Araneae, Anyphaenidae). The correspondences of three sclerites are tested, in a data set of 93 species having one, two or three sclerites, using a simultaneous analysis of all the morphological characters. Most parsimonious trees are identified together with the correspondences they imply. Once the correspondences are integrated in the phylogenetic analysis, it is easy to evaluate the robustness of trees or decay in optimality after changes in anatomical interpretations. A Bremer support for anatomical interpretations is proposed, calculated as the increase in tree length when the specific interpretation is not used. © The Willi Hennig Society 2007.     

Evolution and taxonomy in capitate hydroids and medusae (Cnidaria: Hydrozoa)

A cladistic analysis of Capitata groups the families in four suborders based on medusa characters (such as manubrium morphology, position of gonads, and position and number of marginal tentacles) and hydroid characters (such as presence or absence of an oral tentacle whorl, and the different development of the tentacles of the oral and aboral whorls). On the family and generic levels, the revision results in changes which unite the separate hydroid and medusa taxonomic systems, defining genera which are not based on characters solely relating to the reduction of medusae to fixed gonophores. In those families where the reduction of the medusa can be analysed, it is shown that the reduction occurred after all synapomorphies defining the genera had evolved and usually affected individual species within a genus rather than the original species from which the other species in the genus evolved. This supports the view that medusa reduction is not in itself a valid generic character. A discussion of the theories of 'inconsistent' or 'mosaic' evolution concludes that no difference in evolutionary rate or degree of specialization can be demonstrated among taxa with free medusae and taxa with gonophores.     

Relationships of the Hooded and Elephant seals (genera Cystophora and Mirounga)

The characters linking Mirounga and Cystophora in the subfamily Cystophorinae are the reduction of the incisors to ³/₁, the nasal sac of the male, and also the general similarity in shape of the postcanine teeth. Because of the unreliability of dental characters, and the possibility of convergence producing the nasal sac, the entire skeleton and some soft parts of the body have been considered. This examination has produced 17 good characters in which Cystophora agrees with other northern phocids, and Mirounga with other southern phocids. Other characters confirming this division, but not considered trenchant enough for inclusion in the table, have also been found.
It is suggested that the subfamily name Cystophorinae be abandoned. The family Phocidae is therefore divisible into two subfamilies; Cystophora being included in the Phocinae, and Mirounga in the Monachinae.
Certain characters suggest that Erignathus and Monachus may be the forms linking the typically northern and the typically southern phocids.     

Structural investigations of octocoral sclerites

A common structural pattern (as observed under the SEM) in the main body of sectioned sclerites of the family Alcyoniidae, and octocorals in general, is the arrangement of acicular crystals in concentric layers. The crystals roughly follow the direction of the spicule axis, however, the sectioned tubercles of large Sinularia spicules have the acicular crystals oriented in the direction of the tubercles (i.e. perpendicular to the spicule axis), contrary to the sectioned tubercles of Sarcophyton and Lobophytum spicules. They reveal some rod-like structures, furcating the acute processes at the top of the tubercles. Sectioned small, club-like Sinularia sclerites show numerous tiny acicular crystals, oriented with their long axes at a fairly constant degree of inclination around a central axis. SEM studies of sectioned Cladiella sclerites show a granulate structure organized in concentric layers, but lacking acicular crystals. The Silurian Atractosella cataractaca show important characters in common with Recent alcyoniid species.     

Homology of the genital sclerites of Megaloptera (Insecta: Neuropterida) and their phylogenetic relevance

The genitalia of Megaloptera are crucial for taxonomic identification and represent a significant component of characters for phylogenetic interpretation of this order. However, several complex genital structures, especially those related to segments 9 and 11 in Megaloptera, have yet to be subjected to a comprehensive survey of homology. The terminology for genital sclerites has been variously and even incorrectly used by different authors, a fact which could lead to much confusion about character evolution. In this paper, we first present a comprehensive morphological comparison of the sclerites of male and female genital segments in 23 megalopteran genera representing all major lineages of Corydalinae, Chauliodinae and Sialidae. Accordingly, we then provide new interpretations on the homology of the genital sclerites which often appear to be considerably different among Megaloptera. Based on our new and revised homology assessments, we conclude that: (i) the small to medium‐sized sclerite beneath the ectoprocts in males of Sialidae represents the fused gonocoxites 11; (ii) the male gonocoxites 11 in Corydalidae are largely reduced and are sometimes retained as a small sclerite beneath the anus; (iii) the predominant sternite‐like sclerite of the female abdominal segment 8 represents the fused gonocoxites 8; and (iv) a pair of sclerites amalgamated with the lateral arms of male gonocoxites 10 in Chauliodinae is the gonocoxites 9. Furthermore, based on our genital homology assessments, we reconstruct an intergeneric phylogeny including all genera of Megaloptera using genital characters in a parsimonious analysis to test their phylogenetic relevance. The phylogeny herein recovered is largely congruent with the results from several previous studies, thus underlying the significant phylogenetic relevance of the megalopteran genital sclerites. The present work provides new insights into the evolution of insect genitalia.