The crustacean lacinia mobilis: a reconsideration of its origin, function and phylogenetic implications

The lacinia mobilis of the Crustacea Malacostraca is a more or less spine-like movable appendage of the medial mandibular edge, inserted near the base of the incisor process. It occurs in two or possibly three eumalacostracan superorders but is retained in the adult stage only in the Peracarida. The lacinia has been interpreted as the distal member of the spine-row found in many adult Malacostraca and/or their larvae, or alternatively as a derivative of a certain cusp ('cusp b') of the biting edge of the primitive lophogastrids. The distribution, ontogeny and function of the lacinia were studied in a variety of Eumalacostraca. There is great variability in the guiding and locking mechanisms involved in biting, within the subclass and even within single orders. A lacinia-based guiding and locking system is likely to function only in weak mandibles. New evidence is produced in favour of derivation of the lacinia from the spine-row, and the 'cusp b' derivation hypothesis is rejected, 'cusp b' being only a highly specialized lacinia. Doubt is cast upon the unity of the superorder Peracarida mainly because the place of the order Amphipoda within it is regarded as insecure.     

Light and Temperature Requirements during Fruit-Body Development of a Basidiomycete Mushroom, Coprinus congregates

Light initiated fruit body primordia of Coprinus congregatus Bull, ex Fr. grown at relatively high temperature (25°C) require a single dark period or low-temperature induction for completion of fruit-body development. The dark period requirement varied with the temperature regime during the inductive dark period A minimum requirement of 2.5 h was found al 15–20°C. Darkness always promotes development of fruit-body primordial, but cannot, be regarded as an absolute necessity until temperature exceeds about 17.5°C. Normal development of me primordia without darkness was obtained by lowering the temperature to 10°C for 6 h. It appeared that at high temperatures two successive stimuli were required for basidiocarp maturation, a light-off and a subsequent signal light-on signal. On the contrary, at 10°C a single low-temperature signal seemed to be involved. Thus, induction of fruit-body development could be produced by alternative pathways. These developmental features have been extended to other fungi and compared with the flowering processes of some short-day plants.     

Effects of Glyphosate on Metabolism of Phenolic Compounds

Light enhanced the inhibiting effect of root-fed glyphosate (5 × 10^?4M) on dry weight accumulation of soybean [Glycine max. (L.) Merr.] seedling axes. Inhibition of growth by light was greatest in hypocotyls, whereas by glyphosate it was greatest in roots. A synergistic effect of light and glyphosate on stimulation of phenylalanine ammonia-Iyase (PAL, E.C. 4.3.1.5) activity was also demonstrated. In continuous white light PAL activity increased linearly for 4 days in axes of seedlings exposed to glyphosate. Evidence of phytochrome involvement in the light effect was shown. The stimulatory effect of glyphosate on PAL activity was greater in roots than in hypocotyls. Soluble hydroxyphenolic compound levels were reduced by glyphosate but were increased by light on a per axis basis. On a fresh weight basis, hydroxyphenolics were more concentrated in glyphosate-treated than in control tissues in the light. When compared to other amino acids, disproportionate decreases in free pools of phenylalanine and tyrosine occurred in axes of seedlings treated with glyphosate and light. The effect of light on all measured parameters was mainly in the hypocotyl, while that of glyphosate was primarily in the root. In the light, glyphosate caused increases in levels of glutamine and other amino acids that may be the result of amination reactions, protecting from excess ammonia generated by enhanced PAL activity. These results suggest that PAL has a strong influence on its substrate levels in this system and/or that glyphosate inhibits synthesis of aromatic amino acids.     

Distribution of Fibronectin and Collagen during Mouse Limb and Palate Development

Indirect immunofluorescence has been used to study the distribution of fibronectin and collagen types I, II, and III in the developing primary and secondary palatal processes and forelimb buds of the Swiss Webster (NIH) mouse. In the palatal processes fibronectin and types I and III collagen are distributed throughout the mesenchyme. Fibronectin is present in the basement membrane, while types I and III collagen are localized in a linear, discontinuous fashion beneath the basement membrane. Fibronectin is not observed in the epithelium, including the presumptive fusion areas. In the forelimb bud these components show a similar distribution prior to chondrogenesis (early day 11). When chondrogenesis commences (late day 11 or early day 12) fibronectin and, to a lesser degree, types I and III collagen are apparently concentrated in the core mesenchyme, suggesting that fibronectin has a role in initiating chondrogenesis, perhaps by increasing cellular aggregation. Type II collagen is observed only in chondrogenic regions. The codistribution of fibronectin and types I and III collagen supports in vitro studies which indicate that cells use fibronectin to bind to collagen in the matrix. The developing chondrogenic regions appear to lose fibronectin gradually, concomitant with the appearance of type II collagen, suggesting that fibronectin is not involved in the maintenance of functional chondrocytes in their matrices.     

An Analysis of Specific Temperature Blocks in the Conjugation Sequence of Paramecium tetraurelia1

ABSTRACT. Temperature shifts have been used to block critical points in the conjugation sequence of Paramecium tetraurelia. Increasing temperatures above 27^°C reduced ciliary agglutination, pair formation, and nuclear exchange; a complete inhibition of these stages occurred at 37^°C. Temperatures below 19^°C had no effect on ciliary agglutination or nuclear exchange but completely inhibited pair formation. The bases for the cells’ inability to form pairs at 19^°C and 37^°C were sought. Cells placed below 19^°C were unable to deciliate or fuse membranes in the holdfast region; at 37^°C, membrane fusion in both the holdfast and paroral regions was prevented. Time course studies on cross-fertilization reveal that temperatures 35^°C block all stages of the process up to the actual exchange of pronuclei. After the exchange has begun, the process continues despite the elevated temperature. Temperature shifts are discussed as a means of conditionally blocking critical points in the developmental program of conjugation.     

The Role of Theory in Ecology

Theory can have many different kinds of use in illuminatingecological research. The examples sketched in this paper include:the uses and short-comings of population models currently usedin setting catch quotas for whales and for fisheries; the richarray of behaviour displayed by nonlinear equations and itsrelevance to understanding natural and managed populations;models for the interaction between populations (particularlythe regulation of natural populations by diseases); and somegeneral patterns of community organization. The paper concludeswith some remarks on the contrasts between public pieties about"The Scientific Method" and the way scientists actually work,from Darwin's day to our own.     

Zoophycos size may indicate environmental gradients

Detailed examination through a continuous stratigraphic interval representing nearly the entire Lower Devonian Onesquethawan Stage shows that the presence and size of the trace fossil Zoophycos varies systematically throughout the unit. The lithofacies of this sequence are interpreted to represent a double offshore-nshore cycle. Both maximum and mean diameters of the Zoophycos web (=spreite) are relatively large within a more offshore setting and become progressively smaller towards both margins of this geographic (= stratigraphic) zone. Close inspection of Zoophycos morphology reveals a nearly perfect correlation (r = 0.96) between Zoophycos web diameter and meniscus height. Meniscus height bears a constant relationship to the maximum body diameter of the animal creating the burrow, consequently, size of the web is directly proportional to body size. Thus the animal is largest near the center of its environmental range and smallest near the margins. Other ichnofossils in the section ( Scalarituba, Phycodes, Chondrites ), measured on a more limited scale, show similar size variations with smaller forms at the margins of their respective ranges. Therefore, trace fossil size may be a sensitive indicator of paleoenvironmental gradients.     

Nitrogen and the koala (Phascolarctos cinereus): some indirect evidence

Indirect evidence provides additional support for the hypothesis that the level of available nitrogenous food is the major limiting influence in the abundance of the koala. It appears that koalas may select for low fibre content which is usually correlated with high nitrogen levels of leaves.     

Systematics, similarity and Acanthaceae pollen morphology

SCOTLAND, R. W., 1992. Systematics, similarity and Acanthaceae pollen morphology. A brief discussion of the history of Acanthaceae classifications is provided. It is argued that several approaches utilizing pollen morphological data for the classification of the family can be identified. The Lindau pollen types are shown to have an indirect relationship to Lindau's own classification. Pollen morphological similarity is explored within the context of cladistic methodology. It is shown that some of the Lindau pollen types are analogous. It is demonstrated that shared similarities can be of three types: conflicting (homoplasious), plesiomorphic and apomorphic.