Germ cell cluster formation and cell death are alternatives in caste-specific differentiation of the larval honey bee ovary

Summary

Caste-specific differentiation of the female honey bee gonad takes place in the fifth larval instar. In queen larvae most ovarioles exhibit almost simultaneous formation of numerous germ cell clusters within the first 20 h after the last larval molt. Ultrastructurally distinctive fusomal cytoplasm connects these cystocytes. Germ cell differentiation is accompanied by morphological changes in somatic components of the ovarioles, the follicle and the terminal filament cells. Subsequently, queen ovarioles elongate and differentiate basal stalks that coalesce in a basal calyx. A second round of mitotic activity was found to occur in the late prepupal and early pupal queen ovary. This round may elevate germ cell numbers composing each cluster to levels observed in follicles of adult honey bee queens. In contrast, germ cell cluster formation does not occur in most of the 120–160 ovarioles of the larval worker ovary, but instead many cells in such ovarioles show signs of impending degeneration, such as large autophagic bodies. DNA extracted from worker ovaries did not reveal nucleosomal laddering, and ultrastructurally, chromatin in germ cell nuclei appeared intact. In the 4–7 surviving ovarioles of the small worker ovary, germ cell clusters were found with ultrastructural characteristics identical to those in queen ovarioles. The temporal window during which divergence in developmental pathways of the larval ovaries initiates shortly after the last larval molt coincides with caste-specific differences in juvenile hormone titer which have long been considered critical to caste-specific morphogenesis.     

Respiration of midges (Diptera; Chironomidae) in British Columbian lakes: oxy-regulation, temperature and their role as palaeo-indicators

1. The specific respiration rate of 13 chironomid taxa and Chaoborus were measured to test the hypothesis of the relation between a species' ability to regulate their oxygen uptake and their distributional patterns among nine study lakes in British Columbia, Canada.
2. Respiration patterns of individual taxa were modelled using piecewise linear regression with break point and simple hyperbolic functions. Three types of respiration curves were identified: (i) classical oxy-conformers (e.g. littoral Cricotopus ) which cannot sustain a sufficient oxygen uptake with decreasing oxygen availability; (ii) oxy-regulators (e.g. profundal Chironomus ) which can regulate and maintain a constant respiration until a certain critical point and (iii) oxy-stressors ( Micropsectra ) which increase their respiration rate with decreasing oxygen availability until a critical point.
3. Respiration was measured at two different temperatures (10 and 20 °C), and over the range of oxygen saturation conditions studied here (0–90%) mean Q ₁₀ values varied from 1.3 to 2.5.
4. The results show that different chironomid taxa have varying sensitivity to low oxygen concentrations and different respiratory responses to increased temperature. The critical point increased to higher oxygen saturation for six taxa, decreased for one taxon and was unchanged for two taxa.
5. The results illustrate one of the possible biological mechanisms behind the use of chironomids as temperature and climate indicators in palaeoecological studies by exploring the link between temperature and respiration physiology.     

Ultrastructure of the pharynx of Prorhynchus (Platyhelminthes, Lecithoepitheliata)

The pharynx variabilis of Prorhynchus is strongly muscular, with a small pharyngeal fold and a thin surrounding sheath. There is one row of inner longitudinal musclcs, up to six rows of inner circular muscles, many radial muscles, one row of outer circular and one row of outer longitudinal muscles, with no sphincter muscle groups. Three kinds of secretion, produced in a cluster of gland cell bodies posterior to the pharynx, enter the pharynx wall. They travel anteriorly in ducts and two kinds unite in a common duct just prior to discharging into the anterior region of the pharynx lumen. The perikarya of lumen epithelial cells lie within the pharynx musculature and, at the anterior and posterior margins of the pharynx, external to the pharynx. Bundles of ciliated receptors are numerous at the anterior and posterior constrictions. Similarities in the ultrastructure of flame bulbs of Rhabdocoela and Lecithoepitheliata suggest a relationship between these groups. However, the usefulness of pharynx ultrastructure for platyhelminth phylogeny cannot be assessed until complete ultrastructural studies of various groups of Rhabdocoela have been made.     

The auditory system in larvae of the migratory locust

ABSTRACT. The course and projection areas of the tympanal receptor fibres in the thoracic ventral cord were revealed by iontophoresis in the last three larval instars. There were no significant differences between the arrangement in larvae and that in adults. The threshold curves of the auditory organ of the last three instars were measured by recording summed potentials in the tympanal nerve. In the frequency range tested (1–20 kHz), larvae and adults differed only in sensitivity. More detailed information was obtained by single-cell recordings from receptor neurones in the tympanal nerve of last instar larvae. No differences could be shown between the threshold curves, or the suprathreshold activity, of low frequency receptors of last instars and adults. However, the high frequency receptors of the last instars are far less sensitive in the frequency range above 12 kHz. This seems to depend on the different mechanical properties of the tympanum in larvae. The response patterns of some typical ventralcord neurones (G-, K-, B-type) were identified by extracellular single-cell recordings in last instar larvae. Convergence of auditory and vibratory inputs onto the G-neurone and the B-neurone (as is known to exist in the adult) was found in larvae in the final and penultimate instars to be causing similar response patterns.     

The problematic Hadimopanella, Kaimenella, Milaculum and Utahphospha identified as sclerites of Palaeoscolecida

Hinz, I., Kraft, P., Mergl, M. & Müller, K. J. 1990 04 15: The problematic Hadimopanella, Kaimenella, Milaculum and Utahphospha identified as sclerites of Palaeoscolecida. Lefhaia , Vol. 23 , pp. 217–221. Oslo. ISSN 024–1164.
Hadimopanella Gedik, 1 977 , Kaimenella Marss, 1988 and Milaculum Müller, 1973 have been established on the basis of isolated elements of unknown origin. Recently, the latter genus has been tentatively related to the Agnatha (van den Boogaard 1988). By contrast, Bendix-Almgreen & Peel (1988) assigned Hadimopanella to the chordate stock but definitely excluded it from vertebrates. Well-preserved worm-like organisms of Palaeoscolecida Conway Morris & Robison. 1986 are known from the Lower Cambrian to the Lower Ordovician. They have their outer surface covered with a pattern of sequin-like sclerites which evidence the systematic affiliation with the isolated sclerites mentioned above. Based on similar structures on the outer surface, Utahphospha Miiller & Miller, 1976 is considered to belong to the same group. * Early Palaeozoic fossils, Palaeoscolecida, isolated sclerites, phosphatization .     

Gamone Production in Large-Scale Cultures of Euplotes octocarinatus1

We report a method that allows us to grow and maintain the freshwater ciliate Euplotes octocarinatus in large quantities. Frequent exchange of culture fluid proved more effective than aeration in obtaining high cell densities (4200 cells/ml) and reasonable doubling times in large-scale cultures. For harvesting gamone 1, the cell density was raised to 10,000 cells/ml. Under these conditions, the cells continued to produce and secrete gamone; they were slightly starved, but they no longer divided. Cell-free fluid with a steady and relatively high yield of gamone was obtained from two such cultures over a period of five months. We isolated gamone 1 also from cell homogenates and compared it with secreted gamone 1, but found no differences in the gamones from these two sources.     

Modification of the courtship song by visual stimuli in the grasshopper Gomphocerus rufus (Acrididae)

ABSTRACT. Males of Gomphocerus rufus L. perform a courtship song consisting of repetitive units, each of which is composed of three subunits (S1, S2, S3). S1 is characterized mainly by slow and fast head rolling; S2 and S3 are distinguished by different types of leg-stridulation. These movements and the associated sounds were recorded during presentation of visual stimuli, either linear displacement of a living female or optomotor stimuli generated by a striped drum. Females moved artificially through the binocular visual field of a courting male with a velocity of 1 cm/s or more are mounted by the male from any subunit S1, S2 or S3, although under natural conditions mounting occurs only from S2. Thus above a critical velocity the courtship programme can be modified. Rotation of a striped drum about the yaw axis of the male during the slow S1 induces asymmetrical leg position, following movements of the head, and prolongation of S1. During S2 the male is especially sensitive to optomotor stimuli and responds with marked changes in body position. In S3 the intensity of the song is reduced, and its duration shortened. Fast drum movements interrupt the courtship programme. Rotation of the drum about the roll axis elicits optomotor head turning that interferes with the head rolling of S1. The fast phase of S1 and the frequency of head-rolling during S1 cannot be modified by optomotor stimulation. The results can be interpreted by assuming certain interactions between three central nervous elements: a calling-song generator, a head-rolling generator, and an optomotor centre.     

The diversity and ontogenetic changes of phyllotaxis in wild-types and two leaf form mutants of Antirrhinum majus L.

We have analysed the phyllotactic patterns of the main shoot in vegetative and generative phases of growth in wild type and mutant plants of Antirrhinum majus L. Wild types 'Sippe50' and 'W l08' were compared to mutants grminifolia and phanlastica . The normal vegetative phyllotaxis of the wild type plants is decussate, but the inflorescence phyllotaxis is spiral and of the Fibonacci type. The phyllotaxis patterns of the mutants differ strongly from that of the wild type. Besides decussate phyllotaxis, whorls of three or four elements as well as spiral patterns in vegetative phase were observed. The vegetative phyllotaxis in mutants is ontogenetically unstable with frequent transitions between patterns, including the reversion of chirality of spiral phyllotaxis. The number of transitions per plant was larger in graminifolia than in phantastica . The inflorescence phyllotaxis was more stable and occasional non-typical phyllotaxis patterns finally transformed to a Fibonacci pattern. The results suggest a possible role of genetic factors in determining the regularity of spatial arrangement of organs.     

Endolith associations and their relation to facies distribution in the Middle Devonian of New York State, U.S.A.

Vogel, Klaus, Golubic, Stjepko & Brett, Carlton E. 1987 07 15: Endolith associations and their relation to facies distribution in the Middle Devonian of New York State, U.S.A.
Microborings of endolithic organisms (e.g. algae, fungi) provide valuable indicators of paleoenvironments. The present study documents the distribution of microborings in fossil skeletal substrates from a spectrum of shelf to basinal facies in the Middle Devonian of New York. Endolithic boring in brachiopod shells and corals were prepared using special embedding-casting method and were examined and photographed with SEM. About 13 distinct types of microborings were discovered, presumably produced by microorganisms (pro- and eukaryotic), sponges, bryozoans and worms. Brachiopod holdfast etchings are reported for the first time from Paleozoic rocks. Microborings are non-randomly distributed among Middle Devonian facies. The highest diversity and abundance of borings occurs in diverse brachiopod and coral-bearing calcareous mudstones; which appear to represent shallow, well-aerated and low turbidity environments. Microboring diversity and frequency decreases markedly into mudstones and siltstones recording higher turbidity as well as into dark gray to black basinal shale facies. 'Leiorhynchus' brachiopods from probable deeper water, dysaerobic environments display very low diversity of micro-boring assemblages. They include brachiopod pedicle borings and one endolith which shows similarities to a modem cyanobacterium. If the latter is correctly identified, it brackets all of the studied facies within the photic zone.