bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Phylogenetic Position of the Rhizocephala: Are They Truly Barnacles?
Authors: Høeg Jens T. 
Published: April 2010

AbstractIncorporation of the Rhizocephala in the Cirripedia, reflecting the traditional view that these parasites evolved from a setose feeding barnacle, has recently been challenged in favour of rhizocephalans being the sister group to all other Thecostraca or a scenario where they evolved from a free‐living, ‘precirripede’ ancestor. Adult morphology is useless in discussing the monophyly of the Cirripedia, since rhizocephalan adults are too reduced to furnish any phylogenetic evidence. But numerous, detailed similarities in nauplii and cyprids of the Thoracica, Acrothoracica and Rhizocephala as well as the ultrastructure of their sperm are synapomorphic relative to other Thecostraca and indicate that these three orders form a monophylum. There is evidence that the stylet in the rhizocephalan kentrogon is homologous to an element in the ancestral mouth field. If so, the Rhizocephala probably evolved before setose feeding was adopted, and constitute the sister group to the Acrothoracica and Thoracica. This conclusion is based on frail evidence so the term Cirripedia should be retained to comprise the Rhizocephala, Thoracica, and Acrothoracica. These three orders all possess remarkably similar cyprids, adapted to accomplish irreversible settlement by cement secretion and initiate metamorphosis, so their last common ancestor was most probably a permanently sessile organism.
Holistic Pattern Analysis as an Alternative to Pattern Cladistics in Hypothesizing Crustacean Phylogenetic Sequences
Authors: Watling Les 
Published: April 2010

AbstractThere has been a growing realization that ‘true’ phylogenetic relationships cannot be determined using pattern cladistical methods alone. The applications of such techniques to the problem of crustacean evolution is first examined using the results presented by Wilson (in this issue). It is found that the degree of correlation of characters in the head vs trunk regions explains very well the grouping of taxa in the cladograms, suggesting that the groups are nothing more than mathematical constructs. The argument is presented that functions of different parts of the crustacean body need to be determined, along with an understanding of how the body morphology is designed in accordance with the dominant functions. A method for producing hypothesized phylogenetic sequences from an analysis of body morphology is proposed and examined using the amphipod family Iphimediidae. It is suggested that cladograms are merely hypotheses and can be tested using functional morphological information of the type outlined.
On the Distribution of the Crustacean Dorsal Organ
Authors: Martin Joel W. , Laverack Michael S. 
Published: April 2010

AbstractAn oval, dorsal organ, variously bearing four minute pits around a central pore and/or encircled by a cuticular border, has been reported for the cephalic region of various groups of living and fossil crustaceans. Although varying somewhat in location and in size, the organ appears basically uniform in organization in at least two of the major crustacean taxa: Branchiopoda (especially Laevicaudata) and Malacostraca (Decapoda and Syncarida). Little is known about its ultrastructure and function in various groups, and it is likely that the term ‘dorsal organ’ also has been applied to several nonhomologous structures. In particular, the embryonic dorsal organ, reviewed recently by Fioroni (Fioroni, P. 1980.—Zoologische Jahrbücher (Anatomie) 104: 425–465) and apparently functioning in nutrition and ecdysis, is not the topic of this paper; that organ is similar in name and location only and appears in embryonic uniramians, chelicerates, and crustaceans. The function of the dorsal organ in branchiopods is in ion regulation, possibly a secondary modification of the original function in marine crustaceans, which is unknown. In larval decapods, the organ probably functions as a chemo‐ or mechano‐receptor. We review the known occurrence of the crustacean dorsal organ, describe the similarities and differences in structure in various taxa, and review the competing hypotheses concerning its function. Phylogenetic implications are discussed.
To the Question of Eyes in Primitive Crustaceans
Authors: Elofsson Rolf 
Published: April 2010

AbstractBased on a review of studies of functional and comparative anatomy of crustacean eyes, a hypothesis is formed on eyes in primitive crustaceans. It is suggested that they were similar to present‐day frontal eyes of the malacostracan type. Neuronal architecture suggests that the development to apposition compound eye followed two main routes, one seen in malacostracans and the other in non‐malacostracans. Within the two subgroups different and separate lines have been followed to form specialized apposition types and, within the Malacostraca, superposition eyes as pointed out by Nilsson (Nilsson, D. E. 1989. Facets of vision, pp. 30–73).
Phylogeny of Selected Maxillopodan and Other Crustacean Taxa Based on 18S Ribosomal Nucleotide Sequences: A Preliminary Analysis
Authors: Abele L. G. , Spears T. , Kim W. , Applegate M. 
Published: April 2010

AbstractRelationships among the following taxa were examined based on 18S ribosomal RNA and DNA nucleotide sequences: Branchiopoda (Branchinecta packardi), Ostracoda (two podocopid species), Branchiura (Argulus nobilis), Pentastomida (Porocephalus crotali), Copepoda (Calanus pacificus, Macrocyclops albidus), Thoracica (Balanus eburneus, Calantica villosca), Acrothoracica (Trypetesa lampas), and Decapoda (Procambarus leonensis, Callinectes sapidus). Phylogenetic relationships were inferred by maximum parsimony and results evaluated by bootstrapping. With Branchinecta packardi as an outgroup, the following tree was inferred: the first branch leads to a node that joins a pentastome, a branchiuran and the two ostracodes; the second branch leads to a node that has the two copepods as a sister taxon to a clade that includes the acrothoracican and thoracicans; the last branch leads to a node joining the two decapods. The analyses suggest: (1) acrothoracicans diverged very early from the cirripede line and are not derived from a lepadomorph‐like ancestor; (2) branchiurans are not related to either copepods or thecostracans but are closely allied with pentastomes; and (3) the Maxillopoda, broadly defined, is not a monophyletic taxon. These results differ from previous studies of these groups.
Chemical Nature and Mode of Stabilization of Egg‐shell in Helicometra pulchella (Rudolphi, 1819) (Digenea: Opecoelidae)
Authors: Kalantan A. M. N. , Arfin M. , Alyousif Mohamed S. 
Published: April 2010

AbstractThe chemical nature and mode of stabilization of egg‐shell protein in digenetic trematode Helicometra pulchella (Rudolphi, 1819) have been investigated using histochemical techniques. It was found that the egg‐shell is stabilized by quinone‐tanning together with dityrosine. Other structural proteins (elastin, collagen and keratin‐like proteins), glycogen and acid mucopolysaccharides were absent in egg‐shell. Tyrosine was present in vitelline cells and immature egg‐shell indicating that the proteins involved in quinone‐tanning were tyrosine rich and tyrosyl residues are modified to form dityrosine in mature egg‐shell.
Glial Cell Composition and Ultrastructure of the Caudal Spinal Cord of Young and Adult Tuataras, Sphenodon punctatus
Authors: Alibardi Lorenzo 
Published: April 2010

AbstractResearch on the caudal spinal cord (SC) of three young and three adult tuataras (Sphenodon punctatus) has revealed that most of the glial cells were well differentiated as astrocytes and oligodendrocytes. The former type was not completely differentiated 3 months post‐hatching, but was the main glial cell type at the age of 1 yr and in adulthood. Smaller numbers of oligodendrocytes were found in the white matter of adult animals than fibrous astrocytes. It was concluded that during growth, there is a progressive decrease in the dark, basophilic and electron‐dense glioblasts, most of which develop as astrocytes.
Light and Electron (SEM, TEM) Microscopy of Taste Buds in the Tench Tinca tinca (Pisces: Cyprinidae)
Authors: Żuwata Krystyna , Jakubowski Michał 
Published: April 2010

Abstract The ultrastructure and quantitative distribution of the taste buds (TBs) were studied in the oropharyngeal cavity and in skin from the head of the tench. All TBs are of similar structure, following an orthodox plan: the basal cells (1–2) are the basis of the bud, and vertically elongated gustatory cells and supporting cells span from the basal membrane to the apex where they form a sensory zone (known as the gustatory pore).The basal cells have finger‐like processes pointing towards the nerve plexus. They do not show any hemidesmosomal connections with the basal membrane. Typical afferent synaptic contacts were found only at the basal cells and gustatory cells while no such contacts were found at the supporting cells.The highest concentration of TBs (up to 170 TBs mm 2) occurs in the epithelial lining of the distal part of the pharynx, the least (12 TBs mm 2) in the epidermis of the distal part of the head. The tops of most TBs protrude above the epithelium but their gustatory pores are slightly sunken, thereby protecting the apical processes of the gustatory cells from mechanical stimulation.
The Morphology of the Naupliar Stages of Sacculina carcini(Crustacea: Cirripedia: Rhizocephala)
Authors: Collis Sarah A. , Walker Graham 
Published: April 2010

AbstractA morphological study was carried out on the fournaupliar stages of Sacculina carciniusing mainly scanning electron microscopy. Frontal horns were present and throughout development the typical nauplius limbs remained simple and gnathobases were lacking. Such features are characteristic of other lecithotrophic barnacle nauplii. The presence of a vestigial ventral thoracic process was evident on the stage III nauplius and was even more prominent on the stage IV nauplius. These observations confirm that the rhizocephalan nauplius is close to the thoracican nauplius form and lend strong support for the retention of the Rhizocephala within the Cirripedia.
Fine Structure of the Female Intoshia variabili(Alexandrov & Sljusarev) (Mesozoa: Orthonectida)
Authors: Slyusarev George S. 
Published: April 2010

AbstractThe morphology and fine structure of female Intoshia variabili, new combination for Rhopalura variabiliAlexandrov & Sljusarev, 1992, were studied with transmission electron microscopy. The body surface is covered with a 3‐layered cuticula, under which is a layer of ciliated + non‐ciliated cells arranged in alternating rings around the body. Ciliated cells have lateral extensions that intercalate with the non‐ciliated cells. The kinetosome of each cilium has two longitudinally oriented cross‐striated rootlets. The outer surface of the ciliated cells is covered with small tubercles, and the cytoplasm of these cells contains granules, vacuoles, mitochondria, fibrillar structures and lamellary bodies. A band of dense fibrils passes through the upper part of each ring of cells, going from one cell junction to another, encircling the entire body. Between the layer of ciliated + non–ciliated cells and the oocytes, elongated contractile cells from 4–5 longitudinal columns and 1 ring, the latter at the level of ciliated rings 7–9. The contractile cells contain thick and thin longitudinally oriented fibrils. The oocytes contain a large nucleus, numerous mitochondria, electron–dense granules and 1–2 spherical structures. An anteriorly situated, ciliated goblet–like receptor, not described for any other orthonectids, consists of three closely apposed cells, the upper part of which contains densely packed cilia. The genital pore opens through a non–ciliated cell and is surrounded by several cells with granules.
Variability in the Presence of Elastic Fibre‐like Structures in the Ventral Aorta of Agnathans (Hagfishes and Lampreys)
Authors: Welsch U. , Potter I. C. 
Published: April 2010

AbstractThis paper investigates whether elastic fibre‐like structures are present in the ventral aorta of hagfishes and lampreys. Fibres, which are morphologically similar to the elastic fibres of gnathostomatous (jawed) vertebrates, are shown to be present in the ventral aorta of the hagfish Paramyxine atami, and also, but to a lesser extent, the dorsal aorta of this species and the ventral aorta of another hagfish, Eptatretus stouti.The ‘elastic’ tissue formed irregular sheet‐like aggregates, comprising well‐defined amorphous material surrounded by tubular microfibrils, whose diameters ranged from 10 to 15 nm. While this tissue was most abundant in the same region of the aortae as that occupied by the elastica interna in the blood vessels of gnathostomes, it was also found deeper in the wall of these blood vessels. Although tubular microfibrils were found in the ventral aorta of the hagfish Myxine glutinosaand the lamprey Geotria australis, these were never associated with well–defined, amorphous material. This parallels the results of previous studies on Myxine glutinosaand another species of lamprey, Petromyzon marinus.Thus, the elastic fibre–like tissues found in the ventral aortae of P. atamiand E. stoutiprovide the first examples of such structures in this region in agnathan vertebrates.
Ultrastructural Study of Oogenesis in the Compound Ascidian Botryllus schlosseri(Tunicata)
Authors: Manni Lucia , Zaniolo Giovanna , Burighel Paolo 
Published: April 2010

AbstractOn the basis of ultrastructural observations, Botryllus schlosserioogenesis is divided into five stages, of which stages 1–3 and 4–5 refer to previtellogenic and vitellogenic phases, respectively. Special attention was paid to the mechanisms of acquisition of nutrient, organelle differentiation, yolk formation and relationships between oocyte and its complex investment.In the gonadal blastema of young buds, small oocytes are recognized early, partially covered by a few primary follicle cells, the presumptive source of all the cellular envelopes of the fully grown oocyte. Some oocytes are seen in the zygotene–pachytene phase, characterized by synaptonemal complexes, but most are found at the end of the diplotene, when oocytes commonly stop meiosis, grow and migrate through blood vessels into blastozooids of successive generations. In laboratory animals, only 1–3 oocytes per blastozooid can reach complete maturity.Detailed observations on the time of appearance and development of organelles, microvilli and endocytotic activity in growing oocytes are also reported. Ultrastructural differentiation and the relationships between oocytes and their envelopes all indicate that both auto– and hetero–synthetic mechanisms for yolk formation occur in B. schlosseri.These mechanisms and the possible role of egg envelopes in the process are discussed, comparing the large yolky eggs of B. schlosseriwith those of solitary species.
Comparative SEM Studies of Lattice Organs: Putative Sensory Structures on the Carapace of Larvae from Ascothoracida and Cirripedia (Crustacea Maxillopoda Thecostraca)
Authors: Jensen Peter Gram , Moyse John , Høeg Jens , Al‐Yahya Hamad 
Published: April 2010

AbstractPutative sensory structures, called lattice organs, were studied with scanning electron microscopy from ascothoracid or cypris larvae representing a wide range of families of the Ascothoracida and Cirripedia. These organs, situated dorsally on the carapace were, with few exceptions, always found in two anterior and three posterior pairs. The lattice organ morphology displayed by the Ascothoracida, a seta–like structure with a terminal pore, is believed to be the most plesiomorphic condition. Within the Cirripedia lattice organ morphology varied from types resembling the Ascothoracida in the Acrothoracica and the lepadomorph Capitulum mitella, to an elongate pore field with a larger terminal pore in most Thoracica and Rhizocephala. Akentrogonid Rhizocephala seem to display the most apomorphic condition. While lattice organ morphology was generally constant at the family level, cases were seen where closely related species such as Chthamalus stellatusand Chthamalus montaguishowed minor, but clear cut differences.Lattice organs in 2 + 3 pairs are argued to represent a synapomorphy for the Ascothoracida and the Cirripedia. The results confirm that the cyprid morphology at the ultrastructural level will prove to be of high value in estimating phylogeny within the Cirripedia.
Ultrastructure of the Spermatozoon of Avitellina centripunctata(Cestoda, Cyclophyllidea), a Parasite of the Small Intestine of Cattle in Senegal
Authors: Bǎ Cheikh T. , Marchand Bernard 
Published: April 2010

AbstractThe Avitellina centripunctataspermatozoon is filiform, tapered at both ends and lacks mitochondria. The anterior extremity exhibits an apical cone and a crested–like body 150–200 nm thick. The axoneme is surrounded by a fine layer of lucent cytoplasm and a sheath of electron–dense material. The cytoplasm is slightly electron–dense at the anterior tip of the apical cone and in region IV of the spermatozoon. Over the rest of the gamete it is subdivided into numerous electron–lucent compartments by irregularly spaced walls. The nucleus is electron–dense. It interposes itself between the cortical microtubules which are all electron–dense centred and spiralized along their whole length. An apical zone containing spiralized microtubules, cortical microtubules which are all electron–dense centred and stop before reaching the posterior extremity of the nucleus, as well as the subdivision into cavities by intracytoplasmic proteinaceous material, have never been described before in a cestod. Moreover, the crested–like body of Avitellina centripunctatais the thickest of those which have been described to date in the cestods.
Ultrastructure of Spermiogenesis and the Spermatozoon of Mathevotaenia herpestis(Cestoda), Intestinal Parasite of Atelerix albiventrisin Senegal
Authors: Bǎ Cheikh T. , Marchand Bernard 
Published: April 2010

AbstractSpermiogenesis in M. herpestisbegins with the formation of a differentiation zone which contains two centrioles associated with an electron–dense, finely granular material. This granular material very quickly becomes striated, a median cytoplasmic extension forms, one of the centrioles becomes laterally oriented in a cytoplasmic bud and the other gives rise to a flagellum. After the migration of the nucleus, a helicoidal crested–like body forms, then the old spermatid separates from the residual cytoplasm. The mature M. herpestisspermatozoon exhibits an apical cone of electron–dense material, a crested–like body and cortical microtubules which are electron–dense centred and spiralized except at their posterior extremity where they are parallel to the spermatozoon axis. The axoneme is of the 9 + ‘1’ pattern. It reaches the posterior extremity of the gamete where the cytoplasm is very electron–dense. The presence of centrioles flanked by ‘striated roots’ has never, to our knowledge, been reported in a platyhelminth. Likewise, a nucleus with an annular cross–section and unevenly distributed electron–dense peri–axonemal material has never been described in a cestod.
Ultrastructural Studies of the Visceral Muscles of Chaetognaths
Authors: Duvert Michel , Salat Christiane 
Published: April 2010

AbstractThe visceral musculature of Chaetognaths was studied with special attention given to the digestive apparatus muscle. In the head the digestive apparatus muscle is relatively thick; individual muscles are difficult to distinguish at the anatomical level; in the anterior part of the oesophagus discontinuous bundles and layers of cross‐striated fibers are found. As a group however, the oesophageal musculature completely covers the oesophageal epithelium. The prominent muscle layers around the oesophagus probably help to force food into the intestine against the turgor pressure of the trunk cavity which tends to collapse the intestine. Around the intestine the musculature is largely circular and smooth. The intestinal epithelium is ciliated despite its muscular covering. Muscle fibers are not individually innervated. They form myoepithelial structures with various intercellular junction types. In the intestinal muscle the fibers show myoendothelial‐like junctions. Sphincters composed of myoepidermal cells surround the anus and the female gonopores. The somatic side of the general cavity is lined with a polymorphic squamous epithelium. Sometimes myoepithelial cells are found, with the occasional presence of extracellular matrix basal to the layer of the squamous epithelium. The ontogenetic relations between the polymorphic epithelium and the composite ‘mesenteries’ remain to be established. We have now some idea about the architecture of the body of Chaetognaths in relation to contractile structures.
Skeletal Ultrastructure in some Cyclostome Bryozoans of the Family Lichenoporidae
Authors: Taylor Paul D. , Weedon Michael J. , Jones Chris G. 
Published: April 2010

AbstractThe ultrastructure of the skeleton is described in six species of lichenoporid cyclostome bryozoans using field emission SEM. Both interior walls (vertical, interzooidal walls, and brood chamber roofs and floors) and exterior walls (basal walls) are initially secreted as tiny wedge‐shaped crystallites without a strong preferred orientation. These are seeded directly onto pre‐existing crystallites in the case of interior walls, but onto the organic cuticle in exterior walls, the bases of the crystallites forming a tightly packed mosaic against the cuticle. With growth the wedges become longer, broader and relatively flatter, developing into platey crystallites. These crystallites grow predominantly distally (i.e. parallel to wall growth direction) and are closely imbricated in a foliated fabric. Local disruptions to this pattern occur, especially in association with crystallite division along “divergent zones”. The pattern also breaks down in old walls where crystallite growing edges become less evident and imbrication is poorly developed. Although conforming to this general model, some differences exist between species of lichenoporids, and in the patterns found in different parts of the skeleton (e.g. apertural spines). Lichenoporid ultrastructure differs from that of both cinctiporid and hornerid cyclostomes: notably, lichenoporids lack the layer of transverse fibres found in cinctiporids, and their predominant distal growth direction of crystallites contrasts with the proximal direction found in hornerids.
Hair Cell Orientation Patterns on the Saccules of Juvenile and Adult Toadfish, Opsanus tau
Authors: Edds‐Walton Peggy L. , Popper Arthur N. 
Published: April 2010

AbstractSaccules from 10 adult (five female, five male) toadfish (Opsanus tau), 13.5–26 cm standard length, were examined for individual/sexual variation in the hair cell orientation pattern. In addition, saccules from two juveniles (5 and 6 cm standard length) were compared with those of the adults to determine whether maturational differences exist in the hair cell orientations. The hair cell orientation pattern is unlike any reported previously for this species or its congener, O. beta. There are no major differences between the hair cell orientations of males and females, nor between the juveniles and the adults. A slight individual variation is present in the proportion of hair cells oriented in a particular direction in a specific area of the sensory epithelium. Potential ramifications of this hair cell orientation pattern are discussed with regard to development and auditory processing.