Regional differentiation of fat bodies in larvae of the indianmeal moth,Plodia interpunctella

Larvae of the Indianmeal moth, Plodia interpunctella, contain two morphologically distinct fat bodies. Tan-colored, highly tracheated fat body located posteriorly in the abdomen was the predominant fat body tissue during the early larval instars. White, sheet fat body located more anteriorly became the predominant type during the fifth (last) larval instar and eventually occupied most of the space of the hemocoel. Ultrastructural morphology of tan fat body showed the tissue to be composed of cells containing numerous, large, spherical mitochondria, with only few lipid, glycogen, or protein storage structures. In contrast, white fat body was composed of cells that in later larval stages had organelles typical of storage functions. Both fat bodies produced storage proteins during the late fifth instar, whereas only white fat body accumulated the storage proteins. Tan fat body dispersed and apparently autolyzed in pharate pupae, whereas the white fat body metamorphosed and persisted into the adult stage. These observations indicate that fat body of the Indianmeal moth is functionally and morphologically differentiated along the anterior-posterior axis into two regional subgroups of cells.     

The auricularia-to-doliolaria transformation in two aspidochirote holothurians, Holothuria mexicana and Stichopus californicus

Abstract. The fragmentation and rearrangement of the ciliary bands that occurs during the auricularia-to-doliolaria transformation is described for the non-feeding auricularia larva of Holothuria mexicana and the more typical planktotrophic auricularia of Stichopus californicus. The ciliary band of the auricularia larva runs along a series of ridges that project from the sides of the body. Fragmentation results from a loss of ciliary band cells from the zones between the ridges. The remaining fragments then reorient, elongate, and fuse to form the 5 circumferential bands of the doliolaria. The fate of the band cells lost during this process could not be determined with certainty, but they disappear after being sequestered beneath the epithelium for a time, probably through histolysis. Cell counts indicate that significant numbers of cells are also lost from the ridges. Normal swimming ceases just before transformation begins, probably because the nerve supply to all or parts of the band is disrupted, and this may play a role in initiating morphogenesis.     

Why the term “larva” is ambiguous,or what makes a larva?

The term “larva” is used for many different metazoans. Although this implies a uniform meaning, the term has in fact been used to address immatures with very different characteristics. For providing more precise reference how the term larva is applied in a specific context, I outline here different criteria that have been used to identify an immature as a larva. These include larvae that (a) differ morphologically from their adult (morpho-larva s. l.); (b) differ morphologically from their adult and additionally possess structures that become reduced during ontogeny (morpho-larva s. str.); (c) have a different ecological niche than their adult (eco-larva s. l.); (d) have a different ecological niche than their adult and additionally fulfil a dispersal function (eco-larva s. str.); (e) transform by a metamorphosis to the non-larval immature or adult (metamorph-larva); (f) differ from the adult by having evolved new structures in the early stages (apo-larva); (g) differ from the adult as the adult has evolved new structures (plesio-larva). The differentiation of these criteria will provide a more precise reference reducing possible misunderstanding and allowing a more precise communication.     

Larval settlement of the green sea urchin, Strongylocentrotus droebachiensis, in the southern Gulf of Maine

Abstract. Settlement timing and differential settlement for the larval stage of the green sea urchin, Strongylocentrotus droebachiensis , in the southern Gulf of Maine was studied during the summer of 1996. Settlement densities on astroturf panels were highest in June and early July (13 to 37 m ⁻² d⁻¹), and peaked in mid-June (199 m⁻² d⁻¹). Settlement was low to nonexistent from mid-July through August (0 to 2 m⁻² d⁻¹). During the peak in settlement, no selection for substrate type was observed. In the remainder of the settlement period, differential settlement occurred, with a preference for substrate covered with live coralline algae. Test diameter of newly settled urchins varied among the substrates, with urchins settling on live coralline algae having the largest test diameter (0.43 ± 0.01 mm). There were no differences in test diameter among the different weeks in which sampling was done. Sustained onshore winds occurred only during peak settlement, suggesting that wind drift currents may concentrate larvae and influence patterns of larval settlement.     

Ultraviolet radiation, toxic chemicals and amphibian population declines

Abstract. As part of an overall ‘biodiversity crisis’, many amphibian populations are in decline throughout the world. Numerous factors have contributed to these declines, including habitat destruction, pathogens, increasing ultraviolet (UV) radiation, introduced non‐native species and contaminants. In this paper we review the contribution of increasing UV radiation and environmental contamination to the global decline of amphibian populations. Both UV radiation and environmental contaminants can affect amphibians at all life stages. Exposure to UV radiation and to certain contaminants can kill amphibians and induce sublethal affects in embryos, larvae and adults. Moreover, UV radiation and contaminants may interact with one another synergistically. Synergistic interactions of UV radiation with contaminants can enhance the detrimental effects of the contaminant and UV radiation.     

黑眶蟾蜍的两性异形与选型配对模式

本研究以黑眶蟾蜍(Duttaphrynus melanostictus)为研究对象,通过对比黑眶蟾蜍抱对个体的体长、头长、头宽、眼间距、鼓膜径、耳后腺长、眼径、前臂及手长、前肢长以及后肢长等形态特征,分析雌性黑眶蟾蜍繁殖输出与其体型的关系,探究黑眶蟾蜍两性异形模式及其与雌性生育力的关系;同时通过对配对个体形态学特征的相关性分析探究了黑眶蟾蜍的配对模式。结果表明,黑眶蟾蜍雌性体长和体重显著大于雄体;两性的所有局部形态特征均与体长成正相关;去除体长因素影响后,雄性头长以及后肢长均明显大于雌性,其余局部形态特征两性间则皆无显著差异。雌体的窝卵重、窝卵数均与其体长和体重成正相关关系。雌性成体的前肢长与抱对雄性成体的前肢长之间呈显著正相关,其余形态特征两性间均无相关性。研究表明,生育力选择是导致黑眶蟾蜍两性异形的重要驱动力;黑眶蟾蜍的选型配对模式未表现在个体大小上,而是体现在局部特征(前肢长),这不仅为揭示两栖类配对模式的普遍性提供了参考,还表明对两栖类选型配对的研究应以多个性状为对象。     

Larval growth patterns in Cyprinus carpio and Clarias gariepinus with attention to the finfold

During the larval period, most teleost fishes undergo a dramatic change in body form. Most functional systems are incomplete at hatching. Rapid development of swimming, feeding and respiration systems are expected. In this study, growth patterns of morphological characteristics related to these three functions were studied in two species of Ostariophysian teleosts: African catfish Clarias gariepinus and common carp Cyprinus carpio . Special attention was paid to the larval finfold, which is a remarkably common feature of fish larvae. The results confirmed that larval growth shows different phases. Many morphological characters showed fast allometric growth in early larvae, followed by isometric growth after an inflexion point. In carp, all larval growth curves showed such inflexion points at a total length of about 7 mm while in Clarias such a coupling was not found. The inflexion points in carp occur at a stage during which the typical larval swimming style changes towards the adult swimming style.     

Choice of optimal oviposition sites by Hoplobatrachus occipitalis (Anura: Ranidae) in an unpredictable and patchy environment

 The rock pools on the river bank of the Comoé National Park (West Africa) provide a very diverse and unpredictable environment for anuran larval development. Because rock pools differ considerably in biotic and abiotic parameters, it should be adaptive for reproducing anurans to choose the most suitable oviposition sites. During the beginning of each rainy season (March to May), from 1991 to 1995, we investigated the allocation of breeding sites by Hoplobatrachus occipitalis, counted the number of eggs, and measured several biotic and abiotic factors that might influence the choice of a spawning site. The probability of predation by conspecific cannibalistic tadpoles and the water-holding capacity (WHC) of pools were the best predictor of number of eggs laid. We experimentally investigated the influence of these two parameters on egg-laying and showed that adults potentially can assess the presence, density, and size of tadpoles in pools by chemical cues. Likewise, manipulation of the water-holding capacity caused a rapid change in egg-laying behavior. To assess the risk of desiccation, frogs have to visit familiar pools repeatedly to monitor the decrease in volume over time and thus gain information about the pools’ water-holding capacity. Received: 22 April 1996 / Accepted: 17 July 1996     

Staging larval and early juvenile Japanese anchovy based on the degree of guanine deposition

Japanese anchovy Engraulis japonicus larvae and early juveniles were assigned to one of three developmental stages based on the degree of guanine deposition. The development in terms of the guanine deposition was a function of body size and age and was more strongly associated with the former. The degree of guanine deposition is found to be valid as a criterion to distinguish Japanese anchovies at the end of the metamorphosing stage.     

EFFECTS OF CADMIUM ON HOUSEFLY: INFLUENCE ON GROWTH AND DEVELOPMENT AND METABOLISM DURING METAMORPHOSIS OF HOUSEFLY

Abstract The objective of this study was to elucidate the effects of cadmium on housefly, Musca domestica. It is suggested that of cadmium in low concentrations of had little influence on growth and development of housefly. Cadmium was mainly distributed in the digestive tracts of housefly larvae, where the cadmium content was higher than that of other parts. During the metamorphosis of housefly the change trend of the cadmium content was very apparent. The cadmium content increased gradually in larval period, whereas it decreased significantly after polarization. Until the sixth day after emergence, only negligible cadmium was left in adult housefly. All these results demonstrated that the response of housefly to cadmium is an evolution adaptation in natural selection.