Sex-specific provisioning behaviour in a monomorphic seabird with a bimodal foraging strategy

Sexual differences in foraging and provisioning behaviour have been observed in several size-dimorphic seabird species. These differences are usually thought to be driven by size-related mechanisms such as the ability to compete for food or defend the nest. However, recent studies on monomorphic species suggest that sexual differences in foraging may arise independently of size. Selective forces driving sex-specific patterns are poorly known but essential to understand parental strategies. In this study, we examine sex differences in the provisioning behaviour of a monomorphic species, the Little Auk Alle alle . Using automated recording systems during two consecutive seasons at two colonies, we found that both sexes used a bimodal foraging strategy in which they regularly alternated single foraging trips of long duration with a cycle of several short-trips. The duration of long-trips was substantially longer in females than in males, and the sexes differed in the number of short-trips they performed in between long-trips, resulting in male-biased provisioning rates in both years. In species with a bimodal foraging strategy, long-trips have been interpreted as self-feeding trips to replenish body reserves. Our results therefore suggest that female Little Auks allocate more time to self-maintenance at the cost of chick provisioning, possibly due to different energetic constraints of the sexes prior and/or subsequent to chick-rearing. Our findings contribute to accumulating evidence that sex-specific foraging patterns may be widespread in sexually size-monomorphic seabird species.     

A phylogenetic test of the calcichordate scenario

The calcichordate scenario of Jefferies and colleagues purports to explain the origin and early evolution of the phyla Echinodermata and Chordata. Calcichordate proponents have argued that echinoderms are the sister group of the chordates and urochordates are the sister group of the craniates. These phylogenetic hypotheses, which differ from the traditional groupings, are derived primarily from morphological interpretations of carpoids (solutes, cornutes, and mitrates), an enigmatic fossil group usually held to be primitive stem-group echinoderms. Although the scenario has received only limited support, it has yet to be falsified. The difficulty with falsifying the calcichordate scenario is proving that the morphological interpretations, for example, that carpoids possessed notochords, dorsal hollow nerve cords, and other typical chordate or craniate characters, are incorrect. Here, rather than argue over the interpretation of fossils, the phylogenetic hypotheses embedded within the scenario are tested. It is found that the calcichordate scenario fails such a test, even if both the Recent and fossils forms are coded according to the calcichordate scenario. It is argued that: (1) the erection of scenarios must follow the construction of a cladogram; and (2) fossils are unable to dictate the relationships among phyla. □ Calcichordate scenario, Carpoidea, Deuterostomia, Echinodermata, Chordata, phylogeny, cladistics.     

Regulation of vitellogenin synthesis and uptake in the boll weevil, Anthonomus grandis

Abstract. Hormonal factors influencing reproductive development were examined in adult boll weevils, Anthonomus grandis (Boheman) (Coleoptera: Curculionidae). Long-day, high-temperature rearing conditions promote reproduction whereas short-day, low-temperature conditions do not. Implants of corpora allata (CA), brains, or brains plus retrocerebral complexes taken from long-day donors, or hormone analogue treatments were used to examine onset of vitellogenin synthesis and uptake in decapitated bodies of adult weevils reared in short-day, low-temperature conditions. Weevils decapitated within 2 days after eclosion and reared in short-day, low-temperature conditions never initiated vitellogenin production or ovarian development. Females and males decapitated on day 2 showed haemolymph vitellogenin within 5 days following treatment with Juvenile Hormone (JH) analogue or implantation of CA, but not after implantation of brain alone or implantation of muscle (sham). Uptake of vitellogenin into the oocytes did not occur unless both JH analogue and brain were given as replacement therapy. These experiments indicated that JH is necessary and sufficient to stimulate vitellogenin synthesis in this species but that a brain factor must be present for vitellogenin uptake.     

Tomato (Lycopersicon esculentum Mill., cv. 'Better Bush') Plant Response to Root Restriction

Observations presented here describe changes in the growth ofLycopersicon esculentum Mill., cv. ‘Better Bush’,at the onset of root-restriction stress. Plants were grown ineither 1500 cm³ (control) or 25 cm³ (treated) containers ina flow-through hydroponic culture system (FTS). Seeds were imbibed,germinated, held for 13 d in sterile germination bags, thenplaced into the FTS and designated day zero plants. Plants grownin the FTS were harvested, every 7 d, from day 11 to day 46.Plant height, root and shoot weights, leaf areas, leaf lengths,branching and flowering were measured to illustrate morphologicalchanges that occurred in response to root-restriction stress.Plants restricted to a 25 cm³ root volume experienced a markedstress after 18 d in the FTS. A reduction in leaf elongationwas evident and preceded the time (prior to day 25) when maximumdry weights were attained by restricted root systems. Controlplants had greater leaf areas and plant dry weights than thoseof root-restricted plants after day 18. Treated plants showedno significant increase in dry weights from day 32 to the endof the experiment. Between day 18 and 25 the root: shoot ratiofor the treated plants dropped below that of the controls. Adventitiousrooting was evident in treated plants by day 25. Roots of thetreated plants showed an apparent waterlogging indicated bybrowning of roots by day 32. Root turnover followed as the primaryroot system was replaced by adventitious roots. The number ofbranches or flowers did not differ between control and treatedplants. The timing of the events described here can be usedto further the study of specific physiological responses oftomato plants to root-restriction stress.     

Use of Lanthanum to Trace Apoplastic Solute Transport in Intact Plants

This electron microscopic study revealed that solutes enterthe apoplasm of root mcristems and move from there to the steleof the root and to the shoots of intact plants. Lanthanum wasused as a plasma membrane-impermeable electron-dense markerof apoplastic solute flux in Hordeum vulgare L., Saiicorniavirgimca L., Spartina alternflora Loisel. and Zea mays L. Thepresence of lanthanum in EM specimens was confirmed by X-raymicroanalysis. Lanthanum that entered the root apoplasm wasalso localized in membrane-bound compartments within cells ofeach plant Lanthanum was localized in vesicles, ER, and vacuolesof root and leaf cells. Following root application, lanthanumwas evident in the leaves of the three grass species studied.Lanthanum was rarely observed in S. virginica leaves. Only plantsexposed to 23 mol m^–3 lanthanum for 24 h or more showedlanthanum in root cell cytosol and this was concluded to bea toxic response. Key words: Apoplast, halophyte, lanthanum, root meristem, transport