Jaw growth and replacement in<Emphasis Type="Italic"> Ophryotrocha labronica</Emphasis> (Polychaeta,Dorvilleidae)

Ophryotrocha labronica, as typical for Eunicida, has a complex jaw apparatus consisting of ventral mandibles and dorsal maxillae. Mandibles are not replaced but are retained throughout life. Larval mandibles have adult-sized cutting plates but their proximal shafts lengthen and enlarge as the worm grows. The maxillary apparatus of O. labronica undergoes three moults or replacements. The initial, or larval maxillae, consisting of two paired basal plates and two paired free denticles, develop in the unreleased larvae. They are replaced in the 5-setiger juvenile by the P1-maxillae consisting of falcate forceps and six denticles. The second moult occurs in the 8- to 9-setiger juveniles and results in the P2-maxillae with bidentate forceps and seven denticles, and the third and final moult results in the K-maxillae and seven denticles. The K-maxillae develop in 9- to 12-setiger males and 13- to 15-setiger females and are not replaced but enlarge proximally. Thus the K-forceps can be traced back through the P2-forceps, P1-forceps, to the larval basal plates, indicating the apomorphic state of the K-forceps. Three pulp cavities, separated by darker fusion lines are visible in weakly sclerotised young K-forceps suggesting the fusion of three separate elements. It is concluded that the Ophryotrocha forceps are homologous to the superior and probably inferior basal plates of other dorvilleids. The internal structure of the Ophryotrocha forceps demonstrates that they are not homologous to the labidognath maxilla I as has been suggested.     

The phylogeny of the annelid genus Ophryotrocha (Dorvilleidae)

Ophyotrocha is easy to keep in the laboratory and has therefore been used in several studies of evolution and speciation. The phylogenetic relationships within the group are, however, still not clear and morphological and molecular data are contradictory. Here we attempt to shed light on the phylogeny by adding an additional gene (cytochrome c oxidase subunit I) to the previous analyses of the group. However, the results are still incongruent with the results from the morphological data. We also include a species of the genus Iphitime, and conclude that this species falls within the Ophryotrocha clade. The implications are discussed.     

The ontogeny of two species of Darwinuloidea (Ostracoda, Crustacea)

The ontogeny of two species of the ostracod superfamily Darwinuloidea, Darwinula stevensoni (Brady and Robertson, 1870) and Vestalenula sp., is documented. The development of the appendages of the two species is very similar, with the exception of the antennule, which shows some variation. The general appearance of appendages during ontogeny of the two species is very similar to that of species of other podocopid superfamilies, such as the Cytheroidea, Terrestricytheroidea, Bairdioidea and Cypridoidea, and different from that of the Platycopida. Using the development of the antenna and the appearance of antennal features, a revised model of darwinulid antennal terminology is presented that homologizes these features with those of the Cypridoidea.     

Foregut morphology and ontogeny of the mud crab Dyspanopeus sayi (Smith, 1869) (Decapoda,Brachyura, Panopeidae)

The morphology of the foregut of the Say's mud crab Dyspanopeus sayi was described in adults and larvae. The ossicle system was illustrated based on a staining method with Alizarin-Red. The gastric teeth and cardio-pyloric valve were dissected and examined using optical and scanning electron microscopy. In the adults, the morphology of ossicles and gastric teeth of D. sayi is very similar to the related species Rhithropanopeus harrisii. The foregut of first zoea (ZI) presented a functional cardio-pyloric valve while the filter press was lacking. The filter press was observed in the pyloric chamber from ZII. The most significant changes in morphology take place after metamorphosis from ZIV to megalopa, including the occurrence of the gastric mill. The organization and morphology of many megalopal foregut ossicles are recognizable in the adult phase, although the morphology of the gastric teeth differs from the morphology of adults. A correlation of gastric mill structures with food preferences and their contribution to the phylogeny are briefly discussed.     

A new genus and species of Dorvilleidae (Annelida, Polychaeta) from Bermuda, with a phylogenetic analysis of Dorvilleidae, Iphitimidae and Dinophilidae

Neotenotrocha sterreri gen. et sp. n. is described from Bermuda. It is a gonochoristic. interstitial polychaete exhibiting sexual dimorphism. The maximum length of males is only 140 μm. while females may be up to 255 μm long. They are thus the smallest polychactes known to contain a mature ovary. The new species is referred to the polychaete family Dorvilleidae, primarily due to the presence of a etenognath jaw apparatus. In almost all external characters the new form is strongly reduced. lacking parapodia, setae, antennae, and palps, whereas larval characters such as trochae and a neurotroch are retained in adults. In the light of earlier literature on phylogeny within Dorvilleidae and the likelihood that Iphitimidae and Dinophilidae are closely affiliated with the latter family, the unique combination of characters in Neotenotrocha is of special interest. A phylogenetic analysis of all apparently valid genera in the three families leads to the hypothesis that Dinophilidae and Iphitimidae represent monophyletic and paraphyletic subgroups. respectively, within Dorvilleidae. Accordingly. the definition of Dorvilleidae is emended and a key to the genera provided. The species Ougia macilenta (Oug, 1978) is referred to Parougia Wolf. 1986 and the generic status of Meiodorvillea apalpata Jumars. 1974 and Protodorvillea gaspeensis Pettibone. 1961 is discussed. Some remarks on the applicability of concepts such as neoteny and progenesis in the characterisation of interstitial dorvilleids are included. On the basis of the cladogram mid these considerations. it is hypothesized that this group may have originated in the single evolutionary event.     

Population genetics of two asexually and sexually reproducing psocids species inferred by the analysis of mitochondrial and nuclear DNA sequences

Background

The psocids Liposcelis bostrychophila and L. entomophila (Psocoptera: Liposcelididae) are found throughout the world and are often associated with humans, food stores and habitations. These insects have developed high levels of resistance to various insecticides in grain storage systems. However, the population genetic structure and gene flow of psocids has not been well categorized, which is helpful to plan appropriate strategies for the control of these pests.

Methodology/Principal Findings

The two species were sampled from 15 localities in China and analyzed for polymorphisms at the mitochondrial DNA (Cytb) and ITS (ITS1-5.8S-ITS2) regions. In total, 177 individual L. bostrychophila and 272 individual L. entomophila were analysed. Both Cytb and ITS sequences showed high genetic diversity for the two species with haplotype diversities ranged from 0.154±0.126 to 1.000±0.045, and significant population differentiation (mean F _ST = 0.358 for L. bostrychophila; mean F _ST = 0.336 for L. entomophila) was also detected among populations investigated. A Mantel test indicated that for both species there was no evidence for isolation-by-distance (IBD). The neutrality test and mismatch distribution statistics revealed that the two species might have undergone population expansions in the past.

Conclusion

Both L. bostrychophila and L. entomophila displayed high genetic diversity and widespread population genetic differentiation within and between populations. The significant population differentiation detected for both psocids may be mainly due to other factors, such as genetic drift, inbreeding or control practices, and less by geographic distance since an IBD effect was not found.     

The ontogeny of feeding behavior and cranial morphology in the leopard shark Triakis semifasciata (Girard 1854): A longitudinal perspective

While much is known about the ecological and functional morphology of feeding in lower vertebrates, studies of elasmobranch feeding over ontogeny are broadly lacking. In this study, the ontogeny of feeding behavior and morphology were investigated in neonatal and young-of-the-year leopard sharks Triakis semifasciata using morphometric measurements of growth and high-speed videography in a longitudinal study. Five food types were used during filming sessions to facilitate differentiation of modulation and variation over ontogeny. Functional aspects of muscle and buccal volume scaling were investigated through dissection. Growth over ontogeny was shown to influence numerous kinematic variables, while intra- and inter-individual variability was the dominant factor affecting feeding behavior. Modulation of feeding behavior based on food size and elusiveness was present for timing variables and predator motion during the strike, but not for food motion or the relative extent of buccal expansion. Allometric growth occurred in all aspects of external cranial morphology measured, resulting in a shallower head profile, anterior displacement of the mouth, and relatively larger jaw musculature over ontogeny. While the degree to which morphology constrains or enhances behavior cannot be directly quantified, variability in behavior greatly exceeds variability in morphology over early ontogeny. Maintenance of a behaviorally and morphologically versatile feeding apparatus throughout ontogeny is proposed to enhance the exploitation of resources and facilitate a diverse diet in T. semifasciata under variable environmental conditions.     

The ontogeny of appendages of Heterocypris salina (Brady, 1868) Ostracoda (Crustacea)

The post-embryonic development of the appendages of the Cyprididae ostracod Heterocypris salina (Brady, 1868) are described in detail and compared with those of other podocope species documented in previous studies. Generally, the appearence of limbs during onotgeny of H. salina is similar to that of other species, but small differences in limb morphologies were identified between H. salina and other Cyprididae species, including other Heterocypris species. Some features appear either earlier or later in the development of H. salina compared with other species, even species of the same genus. These features may be useful characters for phylogenetic analyses at the genus and family levels.     

Comparative ontogeny of photobehavioural responses of charrs (Salvelinus species)

Synopsis The development of photobehavioural responses in brook (Salvelinus fontinalis) and lake (S. namaycush) charr was studied by monitoring the intrasubstrate movements and concurrent photoresponse behaviour of incubated embryos and alevins. Photoresponse behaviour of both F-1 hybrids of the parent species was also recorded. All embryos initially moved downward in the substrate, however brook charr descended farther and faster into the substrate than did lake charr. Photoresponse tests demonstrated a similar pattern of photoresponse transformation from a photonegative to a photopositive state in both species. However, photoresponse reversal was faster, more extensive and occurred later in brook charr than in lake charr. Patterns of photoresponse change in F-1 hybrids were intermediate between those of the parent species. Photoresponse shifts preceded the onset of alevin emergence in both species. occurring when differential development of various morphological characters existed. Developmental states of characters were synchronously maximal towards the end of alevin emergence. Intermediate measures of morphological development were observed for F-1 hybrids. Possible functions and mechanisms of photoresponse transitions are discussed in relation to ecological differences between the species.     

Ovary organization and oogenesis in two species of Lumbriculida (Annelida,Clitellata)

The aim of the present study is to describe the organization of the ovary and mode of oogenesis at the ultrastructural level in two representatives of Lumbriculida – Lumbriculus variegatus and Stylodrilus heringianus. In both species studied, the ovaries are small and conically shaped structures that are attached to the intersegmental septum via a thin ligament. The ovaries are composed of germline cysts formed by germ cells interconnected by stable cytoplasmic bridges. As a rule, the cyst center is occupied by a poorly developed anuclear cytoplasmic mass, termed a cytophore, whereas the germ cells are located at the periphery of the cyst. Germline cysts are enveloped by somatic cells. The ovaries of the species studied are polarized, i.e., along the long axis of the ovary there is an evident gradient of germ cell development. The data obtained suggest ovary meroism, i.e., two categories of germ cells were found: oocytes, which continue meiosis, gather nutrients, grow and protrude into the body cavity, and nurse cells, which do not grow and are supposed to supply oocytes with cell organelles and macromolecules via the cytophore. The ovary structure and mode of oogenesis in the species studied were compared with those of other clitellate annelids. As a rule, in all clitellates studied to date, the ovaries are composed of germline cysts equipped with a cytophore and associated with somatic cells; however, the ovary morphology differs between taxa regarding several quantitative and qualitative features. The ovary organization and mode of oogenesis in L. variegatus and S. heringianus strongly resemble those found in Tubificinae and Branchiobdellida studied to date. Our results also support a sister-group relationship between Lumbriculida and a clade comprising ectoparasitic clitellates (i.e., Branchiobdellida, Acanthobdellida and Hirudinida) with Branchiobdellida as a plesiomorphic sister group to Acanthobdellida and Hirudinida.     

Comparative exine ontogeny in some members of the family Zygophyllaceae sensu lato

Summary. Exine ontogeny is studied in five taxa of the family Zygophyllaceae sensu lato (Peganum harmala L., Zygophyllum album L., Fagonia cretica L., Tribulus terrestris L., and Nitraria retusa [Forsk.] Asch.). In the beginning of the tetrad stage, the plasmalemma is attached to the callose wall, except in T. terrestris, where it describes crests and hollows. The primexine matrix is fibrillar, bilayered in T. terrestris and unilayered in the other taxa. In all species except P. harmala, the procolumellae are heterogeneous with clear zones and they become compact later. In T. terrestris, they are built on the crests. In Z. album and T. terrestris, a primordial nexinic lamella is set up. It is tripartite with a white line seen at some levels; on its external leaflet, the foot layer is observed, and on its internal leaflet, there is the endexine with numerous lamellae. This white line disappears often in the mature exine. In T. terrestris, there is a thick nexine that is coarsely lamellate inside. In the aperture zone, the columellae are lacking, the tectum and the foot layer get thinner; they unite and form the apertural membrane with the external part of the endexine. There is a granulolamellar endexinic zone well developed in P. harmala, whereas it is threelayered and weakly developed in T. terrestris. Correspondence and reprints: Laboratoire de Botanique Fondamentale et Appliquée, Faculté des Sciences, Université de Tunis El Manar, Campus universitaire, 1060 Tunis, Tunisia.     

Description of two new interstitial species of Psammodrilidae (Annelida) from Bermuda

The family Psammodrilidae (Annelida) is a group of small polychaetes hitherto containing three nominal species in Psammodriloides and Psammodrilus. Psammodrilus swedmarki, n. sp. and P. moebjergi, n. sp. are described from subtidal coarse sand in Bermuda. Both new species are interstitial, as is the monotypic Psammodriloides fauveli Swedmark, 1958, which they resemble by their small size and lack of a muscular collar region. However, studies with scanning electron microscopy show that the larger, hermaphroditic P. moebjergi possesses a pair of peristomial dorsolateral non-ciliated areas with hexagonal cells representing those of the characteristic collar region of Psammodrilus. The uncini of both species resemble those of Psammodrilus balanoglossoides Swedmark, 1952. The systematically contradicting characters support a synonymization of the two genera. An emended diagnosis of Psammodrilus and a key to the species are presented.     

Elaborate petals in Australian Spermacoce (Rubiaceae) species: morphology, ontogeny and function

BACKGROUND AND AIMS: Australian Spermacoce species display various types of elaborate petals. Their precise morphology, ontogenetic origin, and function are hitherto unknown. The aim of the present paper is to unravel the development and nature of the diverse types of elaborate petals in Spermacoce through a floral ontogenetic study. METHODS: The floral ontogeny of six species characterized by different types of corolla appendages was studied by scanning electron microscopy and light microscopy. In order to elucidate the possible functions of the elaborate petals, field observations were conducted as well. KEY RESULTS: Scanning electronmicrographs show that full-grown petals of Spermacoce lignosa, S. phaeosperma and S. redacta bear appendages on their ventral side. Despite their different appearance at anthesis, the appendages develop very similarly in all three species. They are initiated at the same developmental stage and are first visible as two arcs of primordia converging from the upper margins of the petal towards its midvein and downwards. In S. brevidens, S. caudata and S. erectiloba, the full-grown petals have two long, concave protuberances, which develop from the tissue at both sides of the petal's mid-vein. In these three species, initiation of appendages on the ventral side of the petals is also observed, but they are hardly visible on the mature petals. The two types of elaborate petals tightly enclose the anthers, both in bud and during most of the flowering period. CONCLUSIONS: Among Australian Spermacoce species, two types of elaborate petals can be distinguished. The former hypothesis that the two types of elaborate petals are essentially homologous is here rejected. Field investigations point out that the elaborate petals might play a role in the pollination biology of the species.     

Floral structure and ontogeny in Globba (Zingiberaceae)

We present new comparative morphological and ontogenetic data on flowers and bulbils of Globba (Zingiberaceae) to clarify their homologies. Globba flowers are characteristically Zingiberaceous, possessing a single stamen and epigynous (``supragynopleural') nectaries, but are unusual as the anther bears triangular lateral outgrowths and the style is held tightly in position across the curvature of the filament like a bowstring. Floral ontogeny in Globba is similar to other Zingiberaceae. Characteristic features, such as anther wings, occur late in development, shortly before anthesis. Unusually Globba has zygomorphic style anatomy with only two abaxial vascular bundles, in contrast to most other Zingiberaceae, which possess three stylar traces. The ovary is unilocular and lacks septa. Bulbils have enclosing bracts and replace flowers in the lower part of the inflorescence; they consist of a shoot with an enlarged corky storage root forming the bulk of the propagule.     

Fine-scale comparisons of genetic variability in seed families of asexually and sexually reproducing Crataegus (hawthorn; Rosaceae)

The reproductive system is one of the key mechanisms that determine genetic diversity at different biological levels. However, few attempts have been made to assess the consequences of asexual reproduction by comparing genetic structure and fecundity of seed families in asexually and sexually reproducing individuals. We have examined two similar hawthorn species, Crataegus crus-galli and C. punctata, that differ in ploidy level and breeding system. Fecundity (per-fruit seed set) and microsatellite genotypes for five loci were determined in 18 and 26 seed families of C. crus-galli and C. punctata (totals of 83 and 118 embryos), respectively. Compared with the sexual diploid C. punctata, tetraploid C. crus-galli shows similar fecundity, but lower genotypic diversity within and between seed families. Reproduction in the tetraploid, while predominantly apomictic, is nevertheless accompanied by outcrossing and selfing. We conclude that in C. crus-galli pollen flow between conspecific individuals is limited, and the combination of pollen fertility, self-compatibility, and pseudogamous apomixis provides reproductive assurance in these tetraploids. Reproductive assurance, in turn, may explain the derived floral architecture seen in most North American tetraploid hawthorns. We also discuss analytical approaches for inferring mating-system parameters in tetraploids and for comparing microsatellite variation across ploidy levels.     

Systematics and biodiversity of Ophryotrocha (Annelida,Dorvilleidae) with descriptions of six new species from deep-sea whale-fall and wood-fall habitats in the north-east Pacific

Six new Ophryotrocha species are described from five whale-falls and two wood-falls off the southern Californian coast. Phylogenetic analyses based on the nuclear gene H3 and the mitochondrial genes COI and 16S using MrBayes and maximum likelihood analyses were performed on 40 dorvilleid taxa and one outgroup. Ophryotrocha batillus sp. nov. is morphologically identical to Ophryotrocha scutellus described from a shallow water whale-fall in the North Atlantic, although the two cryptic species differ genetically. Ophryotrocha langstrumpae sp. nov. is closely related in the molecular phylogenetic analyses to these two sibling species. Ophryotrocha flabella sp. nov. is similar to Ophryotrocha globopalpata, and although there are a few morphological differences, the genetic divergence is low between the two species. Ophryotrocha nauarchus sp. nov. is sexually dimorphic, with males having appendages on the first chaetiger. Ophryotrocha magnadentata sp. nov. and Ophryotrocha longicollaris sp. nov. are sister species in our molecular analyses, and together with O. nauarchus sp. nov. and O. flabella sp. nov. they fall within a clade that includes O. globopalpata and Exallopus jumarsi described from hydrothermal vents in the Pacific Ocean and Ophryotrocha longidentata from the shallow North Atlantic. Our results highlight the remarkable unknown diversity of deep-water habitats and the role of chemosynthetic ecosystems in the evolution of deep-sea life.     

Comparative lactation in two species of rat-kangaroo (Marsupialia)

1. Milk composition and energy content was measured in two related marsupials, Bettongia gaimardi and Potorous tridactylus. 2. Although protein content was consistently higher in bettong milk, lactational trends in both species are similar to those reported for other marsupials. 3. The faster relative growth rate of the bettong may be correlated with the increased protein and a higher milk intake.     

Ovary architecture of two branchiobdellid species and Acanthobdella peledina (Annelida, Clitellata)

The aim of this study was to present data about ovary organization and oogenesis in two small groups of clitellate annelids, i.e. in representatives of Acanthobdellida (Acanthobdella peledina) and Branchiobdellida (Branchiobdella pentodonta and Branchiobdella parasitica), and to compare them to ovaries known from true leeches and oligochaetous clitellates. In A. peledina, the ovaries have the form of elongated cords, termed ovary cords, and are enveloped by coelomic sacs, the so-called ovisacs. The ovisacs are paired and each one contains only one ovary cord. The morphology and structure of the ovary cords depend on the maturity level of the animal. In young specimens the ovary cords are short and contain mainly oogonial cells and germ cells entering meiosis. Oogonia divide mitotically without full cytokineses, and as a result germ-line cysts are formed. As the animals grow, the cords become more elongated and the germ cells within the cords differentiate into nurse cells and oocytes. Oocytes gather cell organelles and, finally, detach from the ovary cord and float freely in the ovisac lumen.In both examined branchiobdellidans the ovaries are also paired. They are short and conical and are not enclosed within ovisacs. The narrow end of each ovary is connected to the intersegmental septum via a ligament, whereas the outermost (broad) end of the ovary extends freely into the coelom. The ovaries are polarized. Their narrow ends contain oogonia, whereas nurse cells and growing oocytes, gradually projecting from the ovary, can be found in their middle and outermost parts. Early vitellogenic oocytes detach from the ovary and float freely in the coelom.In all of the species studied, the ovaries are made up of germ-line cysts associated with somatic (follicular) cells. The architecture of a germ-line cyst is exactly the same as in other clitellate annelids that have been studied to date. Each germ cell in a cyst has one stable cytoplasmic bridge connecting it with a central anuclear cytoplasmic mass, a cytophore. The fate of germ cells constituting cysts is diverse. The majority of the cells withdraw from meiosis and become nurse cells; only a few continue meiosis, grow and become oocytes. The meroistic mode of oogenesis is suggested. We suggest also that the formation of germ-line cysts and ovary meroism should be regarded as basal conditions for all Clitellata. The occurrence of ovisacs enveloping the ovaries in A. peledina and Hirudinida is regarded as a synapomorphy of both groups, whereas ovaries found in B. pentodonta and B. parasitica have no ovisacs and resemble ovaries described in Oligochaeta sensu stricto.