Functional morphology, ecology, and evolution of the Scaphitaceae Gill, 1871 (cephalopoda)

Scaphitids are heteromorph ammonites exhibiting morphologicaltrends counter to of those of the other main heteromorph ammonitegroups. These trends include the shortening of the body chamber,lateral compression of the whorl, closure of the coil, and moreregular, spiral coiling. Scaphitid-like morphologies may haveappeared in other heteromorphs, but the Scaphitaceae are monophyletic.The most primitive scaphitids are known from the Albian, butan important radiation occurred in the Western Interior Seawayof North America from the Santonian to Maastrichtian, some ofwhich spread to the Old World. The scaphitid morphology is consistentwith improved swimming abilities, but scaphitids remained associatedwith the seafloor and are best considered to have been nektobenthossimilar to modern nautiluses.     

Respirometry and swimming dynamics of the giant australian cuttlefish, sepia apama (mollusca, cephalopoda)

Swimming dynamics of the giant Australian cuttlefish, Sepia apama, were investigated using swimtunnel respirometry. Relationships between jet pressure, fin frequency, swimming speed and oxygen consumption were defined. Laboratory calibration of swimming parameters is necessary to allow estimates of swimming costs in the field.

Jet pressure was the best predictor of oxygen consumption with an averaged equation of MO₂ = 722 (jet pressure) + 107 r² = 0.51. Individually, fin frequency and jet pressure correlated highly to swimming speed, but due to the complicated usage of finning and jetting, the correlation between swimming speed and oxygen consumption was weaker. Cuttlefish were not optimal swimtunnel subjects and could not swim at high speeds for extended periods. At 15°C and a swimming speed of 0.06 m s^-1, the gross cost of transport was calculated to be 10.1 kg^-1 m ^-1, with a net cost of 4.1 kg^-1 m^-1.     

Pollen ontogeny in Brasenia (Cabombaceae, Nymphaeales)

Brasenia is a monotypic genus sporadically distributed throughout the Americas, Asia, Australia, and Africa. It is one of eight genera that comprise the two families of Nymphaeales, or water lilies: Cabombaceae (Brasenia, Cabomba) and Nymphaeaceae (Victoria, Euryale, Nymphaea, Ondinea, Barclaya, Nuphar). Evidence from a range of studies indicates that Nymphaeales are among the most primitive angiosperms. Despite their phylogenetic utility, pollen developmental characters are not well known in Brasenia. This paper is the first to describe the complete pollen developmental sequence in Brasenia schreberi. Anthers at the microspore mother cell, tetrad, free microspore, and mature pollen grain stages were studied using combined scanning electron, transmission electron, and light microscopy. Both tetragonal and decussate tetrads have been identified in Brasenia, indicating successive microsporogenesis. The exine is tectate-columellate. The tetrad stage proceeds rapidly, and the infratectal columellae are the first exine elements to form. Development of the tectum and the foot layer is initiated later during the tetrad stage, with the tectum forming discontinuously. The endexine lamellae form during the free microspore stage, and their development varies in the apertural and non-apertural regions of the pollen wall. Degradation of the secretory tapetum also occurs during the free microspore stage. Unlike other water lilies, Brasenia is wind-pollinated, and several pollen characters appear to be correlated with this pollination syndrome. The adaptive significance of these characters, in contrast to those of the fly-pollinated genus Cabomba, has been considered. Brasenia does not produce pollenkitt nor develop tectal microchannels as does Cabomba. Instead, the discontinuity of the tectum reduces the amount of sporopollenin in the wall, which may allow for more effective wind dispersal. The importance of reassessing palynological characters in light of new ontogenetic data and the phylogenetic implications of this reevaluation are also discussed.     

Pollen and anther ontogeny in Cabomba caroliniana (Cabombaceae, Nymphaeales)

Cabomba is a small water lily genus that is native to the New World. Studies of pollen development and associated changes in the anther yield valuable characters for considering the evolution of reproductive biology in seed plants. Here we characterized the complete ontogenetic sequence for pollen in Cabomba caroliniana. Anthers at the microspore mother cell, tetrad, free microspore, and mature pollen grain stages were studied using scanning electron, transmission electron, and light microscopy. Tetragonal and decussate tetrads both occur in C. caroliniana, indicating successive microsporogenesis. The exine is tectate-columellate, and the infratectal columellae are the first exine elements to form, followed by a continuous tectum and a thin foot layer. A lamellate endexine initiates in the early free microspore stage, but becomes compressed in mature grains. Tectal microchannels and sculptural rods also initiate during the early free microspore stage, and significant pollenkitt deposition follows, supporting the hypothesis that these elements function in entomophily. The tapetum is morphologically amoeboid, with migratory tapetal cells directly contacting developing free microspores within the anther locule. Results from this study illustrate the importance of including ontogenetic data in analyzing pollen characters and in developing evolutionary and ecological hypotheses. The new palynological data also emphasize the character plasticity that occurs in basal angiosperms.     

Campynemanthe (Campynemaceae): Morphology, microsporogenesis, early ovule ontogeny and relationships

Campynemanthe Baill. consists of three species endemic to New Caledonia. Two species are studied and compared. The tapetum is secretory with 2-nucleate tapetal cells. Microsprogenesis is successive, microspore tetrads are isobilateral and the pollen grains are free and inaperturate or have a weakly defined aperture. Placentation is axile with 3–4 ovules in each of the three locules. Ovules are anatropous and crassinucellate with the micropyle formed by the inner integument alone. The archesporial cell cuts off a parietal cell, which divides to form a parietal tissue. The nucellar epidermis divides periclinally at the nucellar apex to become 2-layered. The megaspore tetrad is T-shaped, in which the micropylar megaspore cells are separated by an oblique wall. The chalazal megaspore enlarges and apparently developes into a Polygonum-type embryo sac, but a mature embryo sac has not been seen. The ripe seeds are pale and non-phytomelaniferous. They have copious endosperm rich in fatty oils. The embryo is minute. These characters and gross morphological similarities support relationship with Campynema Labill., but there are also conspicuous differences. The two genera are considered related. They also closely approach genera of the variable family Melanthiaceae and there are reasons to include them in this family.     

Floral ontogeny, pattern formation, and evolution in Hibbertia and Adrastaea (Dilleniaceae)

Floral development was compared with scanning electron microscopy in 12 Australian species of Hibbertia representing most of its morphological variation, and in the related Adrastaea (Dilleniaceae). Calyx and corolla arise in quincuncial helices in radially symmetrical species, while the petals initiate unidirectionally from one side in zygomorphic species. Stamen number (3-200+) proliferates by centrifugal addition of individual primordia or by innovations of common primordia and ring meristems. Common primordia arise in single-stamen positions alternately with petals, and each produces one to several stamens centrifugally that remain attached to a shared base and form a stamen fascicle. A ring meristem in Adrastaea initiates a whorl of five stamens, alternate with the first stamens but outside their whorl. In radially symmetrical species of Hibbertia, a first ring of stamens is supplemented centrifugally by additional stamens on a meristem ring. The first stamens in zygomorphic species of Hibbertia initiate as a terminal ridge on the floral apex, with subsequent stamens added centrifugally on one side and two carpels initiated on the opposite side. The carpels arise as a simultaneous ring in radially symmetrical flowers, or as a simultaneous pair in zygomorphic species. Staminodial presence is viewed as of minor significance. Four pollinator syndromes are proposed for Hibbertia, related to differing floral architecture.     

Floral ontogeny inMazus pumilus (Scrophulariaceae)

InMazus pumilus, all the floral appendages are initiated in acropetal sequence in the second cell layer (except stamens) of the floral primordium by periclinal divisions. The actinomorphic calyx tube is formed due to zonal growth. The zygomorphy in corolla is evident from the inception of petal primordia which arise sequentially as independent units in order of one anterior, a pair of anterio-lateral followed by a pair of posterio-lateral. Later these primordia exhibit differential growth because of which zygomorphy becomes more pronounced. The upper corolla tube is formed by interprimordial growth and lower corolla tube by zonal growth. Stamens are initiated in the third layer of the floral apex. Unlike sepals and petals, in the development of stamens (4) underlying cells of corpus also contribute. Posterior stamen is absent. The stamens become epipetalous because of interprimordial and zonal growth in the common region below the bases of petals as well as stamens. The two carpel primordia arise as crescent shaped structures which become continuous due to interprimordial growth. The ovary is formed by a ring of zonal meristem. The style develops later between stigma and ovary because of intercalary growth. The residual apex grows vertically along with the ovary and forms the septum of the ovary. All the floral appendages exhibit similar pattern of histogenesis and early growth suggesting thereby the appendicular nature of these appendages.     

Femoral ontogeny and locomotor biomechanics of Dryosaurus lettowvorbecki (Dinosauria, Iguanodontia)

Ontogenetic changes in femoral morphology and locomotion were analysed in the iguanodontian dinosaur Dryosaurus lettowvorbecki using cross-sectional data and applying principles of beam theory. The results presented here suggest that locomotor ontogeny in D. lettowvorbecki was more complicated than has generally been recognized. The percentage cortical area (a measure of the relative amount of bone) increases abruptly over a relatively short period during early ontogeny and then remains uniform during subsequent increases in body size. Modifications in cross-sectional shape also occur with increasing size, as demonstrated by differences in second moment of area ratios. The patterns of change in these properties indicate that the orientation of mechanical loadings acting on the femur of D. lettowvorbecki differed at various stages of growth and development. It is suggested that the alterations in femoral architecture described here reflect a shift from quadrupedality to bipedality early in the ontogeny of this animal.     

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.     

Gone and ovule ontogeny in Phyllocladus (Podocarpaceae)

TOMLINSON, P. B., TAKASO, T. & RATTENBURY, J. A., 1989. Cone and ovule ontogeny in Phyllocladus (Podocarpaceae). Cones are borne directly on phylloclades, usually in the position of basal segments or as segment appendages. Each cone consists of a series of spirally arranged bracts, of which the middle bracts each subtend a single, sessile ovule. There is no ovuliferous scale. Ovules arise as ovoid outgrowths; integument development involves periclinal divisions of hypodermal cells with the integument becoming bilobed and extended laterally. The mature ovule is flask-shaped. The integument includes an extensive middle region bounded by an inner and outer epidermis; the outer hypodermis is differentiated as two contrasted cell layers. An aril differentiates late by periclinal divisions of the outer hypodermal cells at the base of the ovule. The three outermost layers of the integument become differentiated in the mature seed as an epidermis, with thick, cutinized outer tangential walls, an outer hypodermal tanniniferous layer and a sclerotic inner layer. Each ovule is vascularized by two strands that diverge from the axial bundles delimiting the gap left by the departing bract trace.     

Synchrony and heterochrony in ontogeny (of fish)

The ontogeny of an organism is a complex process that strongly depends on the timing of developmental processes. In this article, I discuss ontogeny of fish (and other organisms) in temporal terms, based on the hypothesis that organisms as self-organized entities may create their own times for their development, and that this development consists of a sequence of longer stabilized states (steps) with shorter, intermittent less-stable intervals (thresholds). If viewed within the context of structure-to-structure, organ-to-organ and/or organism-to-environment relationships, then the saltatory pattern of ontogeny emerges at each transition from one stabilized state to another. I consider two timing mechanisms essential to ontogeny - synchrony (coordinating) and heterochrony (implementing); their possible roles are discussed. Besides this, a new context and understanding for the term heterochrony is proposed. At least three levels of heterochrony should be distinguished: interspecific, intraspecific and intraindividual. However, the difference among these three types of heterochrony is not in the phenomenon itself but in the way we perceive and classify it.     

Limb ontogeny and trunk segmentation in Nebalia species (Crustacea, Malacostraca, Leptostraca)

The ’egg-larval’ development of two species of Nebalia has been examined with SEM. Various details concerning limb ontogeny and trunk segmentation are described. The most important of these are the following. The tripartite state of the peduncle of antenna 2 in the adult of Nebalia species is derived from the fusion of the third and fourth podomeres, present in late larvae. The proximal portion of the mandible in the adult of Nebalia brucei, carrying the ’coxal process’, is, based on the ontogenetic evidence, interpreted as the combined basis and coxa, and the bipartite palp is interpreted as the endopod. The early development of the thoracopods and the three anteriormost pleopods is identical. They all start as laterally directed, biramous limb buds. This suggests that tagmatisation of the trunk of the Leptostraca (and other Malacostraca) has been developed from an ancestor with an undivided trunk region with serially similar limbs. Certain early stages reveal an extra, ’eighth’, limbless pleon segment, as compared with the normal number of seven pleomeres of adult Leptostraca. The presence of a row of ventral, sternitic, triangular processes between the bases of the thoracopods, as they are found in certain stages of a species of Nebalia, is suggested as a possible ground pattern for the Malacostraca. Accepted: 1 February 2000     

The ontogeny of the cypridid ostracod Eucypris virens (Jurine, 1820) (Crustacea,Ostracoda)

The chaetotaxy (shape, structure and distribution of setae) of appendages and valve allometry during the post embryonic ontogeny of the cyprididine ostracod Eucypris virens are described. It is shown that the basic ontogenetic development of E. virens is very similar to that of other species of the family Cyprididae. During ontogeny, the chaetotaxy shows continual development on all podomeres of the limbs with the exception of the last podomere on the antennulae. The long setae on the exopodite and protopodite of the antennae have a natatory function until the actual natatory setae develop in later instars. Aesthetascs (presumed chemoreceptors) ya and y3 are the first to develop and may have an important function in the first instars. Cyprididae require a pediform limb in the posterior of the body presumably to help them to attach to substrates and this is reflected by the pediform nature of one limb at all times throughout all instars. This study has also shown that the fifth limb is most probably of thoracic origin and hence ostracods have only one pair of maxillae.     

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.     

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.     

Morphology, ontogeny and histochemistry of secretory trichomes of Geranium robertianum (Geraniaceae)

Geranium robertianum bears three types of glandular uniseriate trichomes which originate from a single protodermal cell and develop through periclinal divisions. Type I trichomes are procumbent and have an oval apical cell, two stalk cells and a basal cell. Type II trichomes are erect and have a pear shaped apical cell, two stalk cells and a basal cell. Type III trichomes are much longer than the other two types and have an elongated apical cell, five long stalk cells and a basal cell. Type I and type II trichomes are common on leaves while III trichomes are more abundant on flower structures.
Type I and type II trichomes secrete terpenoids and phenols. Type III trichomes are characterized by the accumulation of anthocyanins in the apical cell and secrete flavonoids.