WALL STRUCTURE AND ACANTHOPORES IN THE BRYOZOAN LEIOCLEMA ASPERUM

Leioclema asperum (Hall), a typical trepostomatous bryozoan, shows well developed acanthopores which are modified parts of orthodox zooecial walls and not separate skeletal entities. They resulted from locally accelerated forward growth of the wall, hence their distinctive cone-in-cone structure. The comparative absence of growth lines in the axial region of each acanthopore suggests that deposition of calcite in that situation was virtually continuous. There is no reason to believe that the acanthopores were originally hollow and they cannot have housed kenozooids, as is commonly supposed.     

Lymphopoietic Tissue and Plasma Cells in Amphibians

SYNOPSIS. Lymphoid tissue and lymphopoiesis in the urodelesand anurans was reviewed. Current information suggests the spleenas the principal site of lymphopoiesis in urodeles. Anuranspresent a more complex situation and the principally spleenicreaction of Rana pipiens to "red-leg" organisms was contrastedwith the kidney intertubular lymphoid reaction of Bufo marinusto bovine serum albumin. Intracisternal accumulations of slightlyelectron dense material, probably immunoglobulins, were morefrequently found in Bufo marinus plasma cells than cells withundistended cisternae suggesting some specialization of thesecells in cold-bloodedvertebrates. The superficial nature ofour current knowledge of lymphoid tissue function and immunityin this groups was emphasized.     

Antigenic Differentiation of the Kinetoplastids Leishmania braziliensis and Trypanosoma cruzi by Means of Monoclonal Antibodies1

BALB/c mice were hyperimmunized with non-infectious extracts of either Leishmania braziliensis promastigotes or Trypanosoma cruzi epimastigotes. When spleen cells from these mice were fused with P3X63Ag8 plasmacytoma cells, the resultant hybridomas synthesized monoclonal antibodies which displayed specific reactivity by indirect immunofluorescence with distinct subcellular components of the parasites. These studies revealed that antigens associated with the flagellum and with a nongranular component of the cytoplasm would account for much of the serologic cross-reactivity observed between the two species. Conversely, antigens associated with surface and/or cytoplasmic granules and with an intracellular organelle believed to be the kinetoplast appeared to be species-specific.     

Systematics and phylogenetic implications of the haplosclerid stromatoporoid Newellia mira nov. gen.

Wood, Rachel, Reitner, Joachim & West, Ronald R. 1989 01 15: Systematics and phylogenetic implications of the haploslerid stromatoporoid Newellia mira nov. gen. Lethaia, Vol. 22, pp. 85–93. Oslo. ISSN 0024–1164. The presence of spicules in a Palaeozoic stromatoporoid is here confirmed. Parallelopora mira Newell, 1935 from the Upper Carboniferous of the U.S.A. is redescribed as a calcified haplosclerid sponge with a primary siliceous spicule framework of isodictyally arranged styles, sub-tylostyles and strongyles and a secondary calcareous skeleton of stromatoporoid grade and probable aragonitic original mineralogy. P. mira is placed within a new genus Newellia, and family, the Newellidae. This form is postulated to have possessed large amounts of collagenous organic material which enveloped and bound the spicular framework in place. By the draping outline of the calcareous skeleton around the spicule framework and by analogy with the Recent demosponge genus Vaceletia, the calcareous skeleton is suggested to have formed by the direct mineralization of this collagenous template. Newellia mira nov. gen. is further proposed to constitute a member of a new clack of haplosclerid stromatoporoids, together with Euz-Miella erenoensis (Lower Cretaceous); a clade with some similarity to Recent non-calcified forms, e.g. Adocia. Most notably, the presence of different calcareous skeleton mineralogies and possibly microstructures in these two forms suggests the independent development of a calcareous skeleton at different times within this spicule clade. Demosponges appear to have produced calcareous skeletons independently in many different spicule clades. Calcified demosponges are now known from the Hadro-merida (Lower carboniferous; Upper Cretaceous - Recent), Axinellida (Upper Triassic - Lower Cretaceous; Upper Cretaceous; Recent), Poecilosclerida (Recent) as well as the Haplosclerida (Upper Carboniferous - Lower Cretaceous; Recent).□Upper Carboniferous, stromatoporoid, spicules, haplosclerid demosponges, calcareous skeleton biomineralization, demosponge clades, polyphyly.     

THE LOVE DART OF HELIX ASPERSA MULLER IS NOT A GIFT OF CALCIUM

The phenomenon of dart shooting in several species of land snailshas still not been explained. We were interested in whetherthe dart can function as a nuptial gift of calcium, as previouslyproposed. Donating calcium would increase the fitness of theoffspring and thereby result in a higher reproductive successfor the donor. We confirmed in Helix aspersa that the developingembryo takes up calcium from the egg shell for the formationof its embryonic shell. However, other results from behaviouralobservations and calcium measurements in various reproductivestructures do not support the calcium hypothesis. We found thatthe dart penetrated the skin in 91.7% or the shootings, butit was internalized by the recipient in only 6.3% of the shootings.The amount of calcium in one dart is roughly equal to that ofone egg, and thus it would not contribute significantly to anaverage clutch of 59 eggs. The spermatophore contains virtuallyno calcium, and therefore it is unlikely that the dart signalsa donation of calcium with the sperm. The dart is also unlikelyto influence egg laying since dart shooting does not predicteither the latency or the productivity of egg laying in theshooter or the recipient. We conclude that the love dart ofHelix aspersa is not a gift of calcium. Instead, we suggestthat it is a vehicle to introduce a substance into the partnerto influence the fate of the donated sperm. (Received 8 November 1996; accepted 25 April 1997)     

The effects of feeding regime on the growth and reproduction of the medicinal leech Hirudo medicinalis

1. The feeding frequency, the size of meals, the number of meals required to attain reproductive maturity and the number of meals taken between iteroparous reproductive bouts were determined in the laboratory under optimal conditions for the medicinal leech Hirudo medicinalis fed exclusively on mammalian (bovine) blood. In addition the number of bouts of reproduction and the numbers of cocoons and hatchlings per cocoon produced were determined.
2. The average time for H. medicinalis to reach reproductive maturity at 20°C was 289 days, at an average wet biomass of 8143 mg with two–nine separate bouts of cocoon production. The number of meals to first reproduction was 8.9 (mean meal size of 3066.7 mg), with a significant correlation between total mass of blood ingested and the numbers of reproductive bouts and number of cocoons produced. Mean lifetime cocoon production per individual was 12.43, with 3.9 hatchlings per cocoon.
3. The significant positive relationships between ingestion, fecundity and developmental rate observed support the hypothesis that declining abundances of field populations of H. medicinalis are the result of lower available energy for growth, reflecting leeches now feeding predominantly on amphibian blood of lower energetic value than mammalian blood.     

Signals for Survival in the Lives of Crickets

Two behavioral acts of undoubted survival value are predatoravoidance and mate choice. In field crickets both are mediatedby acoustic signals containing high frequency spectral energy.Nocturnally active bats use ultrasonic echolocation signalsto detect and locate their prey, which includes insects thatdisperse by flying at night. Many insects have developed ultrasoundavoidance behaviors in flight, in order to elude bats. In crickets,an auditory interneuron that is excited by ultrasound has beenidentified and shown to initiate the avoidance behavior; itis a putative bat-detector cell. Male field crickets produceacoustic signals during their courtship (females are mute).Courtship song appears to facilitate mating success (copulation),for its absence in courtship diminishes the likelihood of copulation.The possible role of the bat-detector neuron in courtship behavioris considered because it is activated by courtship signals aswell as bat-like ultrasound. The role of behavioral contextshapes the participation of neurons in the neural networks thatunderlie a given behavior.     

EFFECTS OF SAMPLE SIZE AND PRIOR MASTICATION ON TEXTURE JUDGMENTS

Two experiments were conducted. In the first, 25 untrained subjects judged the hardness and chewiness of three different food samples following either 0, 60, 120, or 180 s of adaptive chewing on an experimental gum compound. No effect of the adaptive chewing was found, in spite of observable and self-reported masticatory fatigue induced by the experimental procedures. These data fail to support the prevalent use of procedural limits on the number and temporal spacing of samples in sensory texture studies. In the second experiment, six groups of subjects (n = 107) judged the hardness and chewiness of two series of food samples that varied in physical size (volume). The groups differed in the degree to which cues about the true size differences were made available. Results showed both hardness and chewiness judgments to increase as a function of sample size, independently of subject awareness of the size differences. These data support the use of procedural controls on sample size, but fail to provide evidence of a size constancy phenomenon. A rheological explanation is proposed to account for the observed sensory effect.     

Leaf anatomy and the occurrence of false veins in Asplenium (Aspleniaceae, Pteridophyta)

False veins in African afro-alpine (2000–4700 m) Asplenium species with long creeping rhizomes and highly dissected leaves are morphologically and anatomically similar to true veins but differ in the absence of a vascular bundle. False veins in Aspleniaceae may have originated by the fusion of leaf lobes, and are more similar to those in Angiopteris and Thelypteris than to those in Davallia and Hymenophyllaceae. Because false veins are long and extend from the leaf margin to the junction of the neighbouring true veins in A. actiniopteroides , A. goetzei , A. majus , A. praegracile , A . sp. nov. and A. uhligii , but short, not reaching this junction in A. decompositum , A. demerkense , A. kassneri , A. linckii and A. mildbraedii , and even absent in A. aethiopicum , A. lademannianum , A. simii , A. stipicellatum and A. volkensii , they can be used for identification in this enigmatic group of ferns.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 187–194.