Biomass and Pigment Production in Three Isolates of Azolla II. Response to Light and Temperature Stress

Two isolates of Azolla caroliniana Willd. (RAR, M-3) and oneof Azolla filiculoides LAM. (LA) were compared and characterizedin defined growth environments. A moderate environment (200–230µ mol m^–2 S^–1, 18/6 h photoperiod and 26/22C thermoperiods) was selected to record growth in near-optimumconditions. All isolates doubled their fresh and dry weightsin approximately 2–3 d during the first week of trials.Acetylene reduction rates were low for all isolates, but RAR(from Amazonian Colombia) generally grew the fastest. RAR alsoaccumulated more chlorophyll, its chlorophyll doubling times(2.14 0.1 d) were 1–2 d faster than those of M-3 orLA, and it retained the most stable chlorophyll a/b ratios andtotal chlorophyll densities. Growth data for all isolates convergedduring the second week. Dry-weight doubling times were longerthan 3 d. None of the isolates excreted measureable amountsof nitrogen in month-long trials. Stress trials were conducted using high light (450–510µ mol m^–2 s^–1) and/or high temperature (35/31C conditions Biomass yields were usually least inhibited, ifat all, with elevation of only photon flux densities. High temperaturealone stimulated the dry-weight growth only of M-3 comparedwith its growth under moderate conditions. Biomass, chlorophyll,and acetylene reduction data suggested that M-3 may have a higheroptimum growth temperature than RAR or LA. The combined effectof light and temperature stress depressed acetylene reductionrates in RAR and M-3 to a greater extent than did either parameteralone. High light levels had more effect than high temperatures ininhibiting chlorophyll doubling times and inducing anthocyaninproduction in RAR and M-3. These two isolates did not form anyanthocyanin in elevated temperatures. Pre-incubation in darknessbefore exposure to elevated light/temperature conditions facilitatedanthocyanin production in all isolates. LA, however, provedto be the isolate most sensitive to stress by heat, alone oraugmented by light stress, according to all criteria used. Azolla caroliniana Willd., Azolla filiculoides Lam., biomass and chlorophyll accumulation, anthocyanin production, acetylene reduction, light/temperature stress     

A cadaver unearthed: the anatomy of the Japanese living fossil Stirpulina ramosa (Bivalvia: Anomalodesmata: Clavagellidae) – the unique specimen in the collections of Emperor Shōwa

The only extant, preserved and complete specimen of Stirpulina ramosa has been discovered in the collections of the late Emperor Shōwa (Hirohito) and is described herein. Hitherto, only shells and the adventitious tubes of this species have been described. This study of the anatomy complements previous ones and adds further information as to how the adventitious tube is formed: that is, by the laying down of an organic, periostracum‐like, template that is then biomineralized internally to form the tube and is externally plastered with the clasts that constitute the enclosing burrow wall. Such secretions are produced by pallial lobes that unite on the right side to create the characteristic sutured pleat in this region of the tube. The periostracum enclosing the so‐interred animal is then secreted against the internal template of the tube. The shell of S. ramosa and, as a consequence, the musculature, is greatly disfigured as a result of the incorporation of the left valve into the fabric of the adventitious tube. This valve can, however, continue to grow within the tube, especially posteriorly. The right valve remains free inside the tube but grows only a little more anteriorly. The anterior mantle, with a minute pedal gape, is greatly thickened and secretes the watering pot component of the tube. In many anatomical respects, for example simultaneous hermaphroditism, S. ramosa still reflects the basic anomalodesmatan plan and such modifications as there are from the clavagellid form relate principally to the structure, formation and thus functioning of the adventitious tube. This study of S. ramosa has allowed the full spectrum of clavagellid adaptive radiation to be analysed and an evolutionary picture created which suggests that species of Clavagella/Dacosta and Stirpulina are Mesozoic (Late Cretaceous) remnants. Conversely, species of Bryopa and Dianadema are more modern, Late Oligocene and Palaeocene (Cenozoic), respectively, and possibly evolved in association with the emergence of the Indo‐West Pacific centre of coral diversity, with a postulated average age of just 30 Myr. © 2013 The Linnean Society of London     

Growth and Reproduction of Leptomonas oncopelti in the Milkweed Bug, Oncopeltus fasciatus

SYNOPSIS. A laboratory colony of Oncopeltus fasciatus was found to be infected with Leptomonas oncopelti. Inasmuch as the parasite is transmitted from parent to offspring an opportunity presented itself to study the biology and transmission of this parasite under controlled laboratory conditions. An apparatus for observing individual bugs was designed and the presence or absence of flagellates in the feces determined. Flagellates were not shed until the bugs became adults after which they appeared in every defecation. Dissection of infected bugs revealed that flagellates were not present in the rectum until adulthood. Further studies indicated that in the midgut of the insect there is a departure from binary fission to budding. The nucleus divides and one of the newly formed nuclei migrates toward a newly formed kinetoplast. Rarely there is still another kinetoplast/nucleus division. In the event the new axoneme grows within the cytoplasmic sheath of the parent flagellum, smaller organisms produced by unequal cytokinesis remain attached. If the axoneme grows free, the smaller daughter organisms become free-swimming. Passage into the rectum of the adult bugs causes a rounding up of all parasites although the leishmaniform organisms continue to divide. It is presumed that infection of clean bugs is accomplished by the ingestion of leishmaniform organisms through a common water source. The reason for the presence of flagellates in the rectum of the adult but not in the nymphal insect and the mechanism responsible for the change from binary to unequal fission are not known.     

Signal components, acoustic preference functions and sexual selection in a cricket

In many sexually reproducing organisms, females choose mates based on multiple male traits. This study examined how two temporal components of the male mating call – chirp rate and chirp duration – affect female mating preference in five populations of a widely distributed North American cricket, Allonemobius socius (Orthoptera, Gryllidae). Chirp rate and chirp duration of the A. socius mating call were varied independently, and the responses of virgin females to these experimentally manipulated calls were repeatedly measured using a sequential single-stimulus design. Significant among- and within-population variation in chirp-duration preferences of females were found. Contrary to many previous studies, call chirp rate had no effect on female phonotaxis. Also there was no evidence of an interaction between chirp rate and chirp duration on female response to male mating calls. Moreover, female responsiveness to average and above-average chirp duration appeared to decline with female (adult) age. Overall, these results suggest evolved differences among populations in chirp-duration preferences, and that selection can act within populations on female chirp-duration preference.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 461–472.