Phylogenetic relevance of the genital sclerites of Neuropterida (Insecta: Holometabola)

Abstract Segment 9 of male Raphidioptera, comprising tergite, sternite, gonocoxites, gonostyli and gonapophyses, is a benchmark for homologies in the male and female terminalia of the three Neuropterida orders Raphidioptera, Megaloptera and Neuroptera. The segments relating to genitalia are 9, 10 and 11 in males and 7, 8 and 9 in females. Results from holomorphological and recent molecular cladistic analyses of Neuropterida agree in supporting the sister‐group relationships between: (1) the Raphidioptera and the clade Megaloptera + Neuroptera, and (2) the suborder Nevrorthiformia and all other Neuroptera. The main discrepancy between the results of these studies is the nonmonophyly of the suborder Hemerobiiformia in the molecular analysis. The monophyly of the Megaloptera (which has been repeatedly questioned) is further corroborated by a hitherto overlooked ground pattern autapomorphy: the presence of eversible sacs within the complex of the fused gonocoxites 11 in Corydalidae and Sialidae. The recently discovered paired complex of gonocoxites 10 (parameres) in Nipponeurorthus (Nevrorthidae) indicates that the curious apex of sternite 9 of Nevrorthus and Austroneurorthus is the amalgamation of the sclerites of gonocoxites 10 with sternite 9, interpreted as synapomorphic. In the molecular study, the Nevrorthidae, Sisyridae and Osmylidae branch off in consecutive splitting events, a result that is supported by the analysis of male genital sclerites reported here. Extraordinary parallel apomorphies (e.g. excessive enlargement and modification of gonocoxites 10 ending in a thread‐like ‘penisfilum’) in derived representatives of Coniopterygidae, Berothidae, Rhachiberothidae and Mantispidae corroborate the dilarid clade of the morphological analysis and leads us to hypothesize a sister‐group relationship of the Coniopterygidae with the dilarid clade. A re‐interpretation of the tignum of Chrysopidae as gonocoxites 11 means that the structure previously called the gonarcus represents the fused gonocoxites 9. In Hemerobiidae, the corresponding sclerite is consequently also homologized as fused gonocoxites 9. The enlargement of the lateral wings of the gonocoxites in both families is interpreted as a synapomorphy. Excessive enlargement of gonostyli 11 in the Polystoechotid clade and Myrmeleontiformia supports a sister‐group relationship of these two clades. The occurrence of certain serial homologues of female genitalia structures (gonocoxites and gonapophyses), such as the digitiform processus together with the flat appendices in segment 8 of certain Myrmeleontidae, or the wart‐like processus together with the flat circular sclerites in segment 7 of certain Berothidae, as well as the presence of gonocoxites 8 as pseudosternites in certain Nemopteridae and Coniopterygidae, are probably character reversals. The digitiform processus of tergite 9 (pseudogonocoxites) in Rhachiberothidae and Austroberothella (Berothidae) are either independently developed acquisitions with a function in oviposition, or are homologous sclerites, possibly of epipleurite origin.     

The annual cycle in body weight of small mammals from the Transvaal, South Africa, as an adaptation to a subtropical seasonal environment

Seasonal breeding of non-hibernating small mammals is generally associated with a reduction in body weight during the non-breeding period. In aseasonal breeders and in exceptional situations, when winter breeding occurs, this pattern cannot be found.
The reduction in body weight is thought to be a means to reduce energy requirements during the harsh non-breeding season that can either be winter, in the Holarctic, or the dry season in the Transvaal highveld.
The controlling mechanism in the strongly seasonal subtropical environment in southern Africa seems to be photoperiod as in small mammals from the northern hemisphere.
Since a general agreement in body weight changes was found in rodents and shrews from both areas, further similarities in adaptations to strongly seasonal environments in the subtropics are expected.
For the first time it is shown that the adaptive responses of small mammals to unfavourable seasons are similar in the Holarctic and seasonal subtropical areas.     

Convergent evolution of the cavefish Astyanax (Characidae, Teleostei): genetic evidence from reduced eye-size and pigmentation

More than 20 populations of the cave-dwelling characid Astyanax occur within a restricted karst area in Mexico. The fish possess reduced eyes without lenses and visual cells. It is still an open question as to whether this condition evolved convergently after multiple entries of the surface ancestor into the different caves or whether a single cave ancestor, already characterized by reduced eyes, spread secondarily within them. In the crosses between specific populations, specimens appear that deviate considerably from those of the parents. They possess larger and better-developed eyes with histologically intact lenses and visual cells; they thus have the structural potential for vision. This indicates that in different cave populations, different mutations in the eye gene system have occurred. In cases where these non-functional rudimentary genes are recombined in hybrid specimens, gene expression may be restored. This is the result of separate evolution of several Astyanax cave populations.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80 , 545−554.     

The effect of diet and live host presence on the growth and reproduction of Terebrasabella heterouncinata (Polychaeta: Sabellidae)

Summary

The effect of diet type and the presence or absence of a live host on the growth and production of eggs and larvae by Terebrasabella heterouncinata were quantified. Diet was shown not to have a significant effect on the time in which the worms on live hosts reached their maximum size. Diet did, however, influence the maximum size and consequently the growth rate of worms, which were larger and grew faster on kelp-fed abalone than on those fed a commercial pellet diet. Despite diet having no effect on fecundity and offspring size, kelp-fed worms matured earlier. The maximum size of kelp-fed worms was unaffected by the absence of a live host, suggesting that the worms do not rely on the host for food. The absence of a live host reduced the growth and sexual maturation rates of worms. There was no difference in the size of offspring in the two treatments, but fewer worms matured sexually and fewer broods were produced on “shells only” than on live hosts. The lower growth rate and reproductive output of worms on “shells only” may be due to the diversion of energy from growth and reproduction to burrow expansion.     

Homology of the genital sclerites of Megaloptera (Insecta: Neuropterida) and their phylogenetic relevance

The genitalia of Megaloptera are crucial for taxonomic identification and represent a significant component of characters for phylogenetic interpretation of this order. However, several complex genital structures, especially those related to segments 9 and 11 in Megaloptera, have yet to be subjected to a comprehensive survey of homology. The terminology for genital sclerites has been variously and even incorrectly used by different authors, a fact which could lead to much confusion about character evolution. In this paper, we first present a comprehensive morphological comparison of the sclerites of male and female genital segments in 23 megalopteran genera representing all major lineages of Corydalinae, Chauliodinae and Sialidae. Accordingly, we then provide new interpretations on the homology of the genital sclerites which often appear to be considerably different among Megaloptera. Based on our new and revised homology assessments, we conclude that: (i) the small to medium‐sized sclerite beneath the ectoprocts in males of Sialidae represents the fused gonocoxites 11; (ii) the male gonocoxites 11 in Corydalidae are largely reduced and are sometimes retained as a small sclerite beneath the anus; (iii) the predominant sternite‐like sclerite of the female abdominal segment 8 represents the fused gonocoxites 8; and (iv) a pair of sclerites amalgamated with the lateral arms of male gonocoxites 10 in Chauliodinae is the gonocoxites 9. Furthermore, based on our genital homology assessments, we reconstruct an intergeneric phylogeny including all genera of Megaloptera using genital characters in a parsimonious analysis to test their phylogenetic relevance. The phylogeny herein recovered is largely congruent with the results from several previous studies, thus underlying the significant phylogenetic relevance of the megalopteran genital sclerites. The present work provides new insights into the evolution of insect genitalia.     

Effect of Zinc Deficiency on Proton Fluxes in Plasma Membrane-Enriched Vesicles Isolated from Bean Roots

Plasma membrane-enriched vesicles were isolated by density gradientcentrifugation from roots of zinc-sufficient and zinc-deficientbean (Phaseolus vulgaris L. cv. Prélude) plants. Thetwo populations of vesicles had similar activities of specificmembrane marker enzymes and ATP hydrolysis and were competentfor proton transport. However, vesicles from zinc-deficientroots showed lower rates of ATP-dependent intravesicular acidificationand increases in passive permeability to protons as well asin the rate, of dissipation of a non-metabolic transmembranepH gradient. The decrease of the rate of proton accumulationin isolated vesicles closely paralleled the increase in potassiumleakage from intact roots and the appearance of visual zincdeficiency symptoms in the shoots. Re-supply of zinc to deficientplants for 24 h promoted shoot growth, reduced potassium leakagefrom roots and led to partial recovery of the proton accumulationcapacity and to a decrease in passive permeability to protonsin isolated vesicles. The results obtained with isolated vesiclesconfirm the previously observed ‘in vivo’ effectsof zinc deficiency and are consistent with the idea that analteration of plasma membrane lipids leads to an increase inpermeability and an impairment in trans-plasma membrane protongradient. Key words: Plasma membrane, H⁺ fluxes, ATPase, zinc deficiency