Beaks and radulae of Early Carboniferous goniatites

About one hundred goniatite beaks (jaws) and five radulae from the Late Mississippian (Early Carboniferous) of Arkansas wgere studied with light and scanning electron microscopy (SEM). Four beaks were found within the body chamber of the goniatite Girtyoceras. Owing to the three-dimensional preservation, these oldest known beaks could be studied in detail and compared with those in living coleoids. The beaks are univalved, and the lower one is larger than the upper. Each beak consists of an organic outer and inner lamella; only the rostrum is weakly calcified. In the lower beak the outer and inner lamellae are about the same length, but in the upper beak the outer lamella is considerably shorter than the inner lamella. The goniatite beaks resemble those in living coleoids in the relative length of the outer and inner lamellae in the upper beak, which probably indicates similarity in muscle insertion. Concerning the length of the inner and outer lamellae, the lower beak is similar to that in Vampyroteuthis and the pelagic octopod Tremoctopus. Late Mississippian goniatite beaks dealt with here are similar to those of Carboniferous and Permian goniatites in general morphology, but differ from those of Mesozoic ammonoids. In the latter ammonoids, the lower beak has a long outer lamella and a short inner lamella, whereas both lamellae have about equal length in the goniatites. Goniatite radulae remain stable during ammonoid evolution and demonstrate a more or less distinct similarity with those in living coleoids.     

Population status, trends and a re-examination of the hypotheses explaining the recent declines of the southern elephant seal Mirounga leonina

1. Between the 1950s and 1990s the southern elephant seal Mirounga leonina underwent large decreases in population size throughout most of its breeding range in the Southern Ocean. While current population estimates suggest a recent recovery, some breeding populations have continued to decrease in recent years (Macquarie and Marion Islands), others have either remained stable (South Georgia, Kerguelen and Heard Island) or have increased (Peninsula Valdés, Argentina). 2. Intrinsic hypotheses for patterns of regional decline include factors that are affected by density-dependent mechanisms: (i) paucity of males, (ii) population ‘overshoot’ and (iii) pandemic disease. Extrinsic hypotheses include (iv) predation, (v) competition with fisheries concerns, (vi) interspecific competition, (vii) environmental change and (viii) human disturbance. Of the eight hypotheses proposed and examined here, we conclude that three can be discounted (i, v, viii), three are unlikely, but may require more testing (ii, iii, iv) and two are plausible (vi, vii). 3. The interspecific competition hypothesis is difficult to test because it requires the simultaneous monitoring of species that overlap directly with elephant seals, many of which have not been identified or little is known. However, an analysis of the relationship between log variance and log abundance (Taylor's power law) for populations of southern and northern elephant seals suggests that interspecific competition is not a significant factor in the decline of the southern elephant seal. 4. The hypothesis that decreases in southern elephant seal populations between the 1950s and 1990s were caused by the environmental change is the easiest to test and most plausible of the hypotheses. We propose a framework by which to test this hypothesis to determine how food availability affects individual survival.     

Recognition of Prey by Suctoria: The Role of Cilia

ABSTRACT. The interaction between the predator, Discophrya collini , and the prey, Tetrahymena pyriformis , was investigated in order to determine what prey factors(s) may be recognized, facilitating the feeding response of the suctorian predator. When viable, deciliated T. pyriformis were offered to starved D. collini , only 12% of the suctoria captured a ciliate compared to 98% when presented with ciliated T. pyriformis . Starved suctoria were also offered three types of tanned sheep erythrocytes used as artificial prey. After exposure to erythrocytes coated with sonicates of T. pyriformis , 16% of the D. collini displayed one or more attached erythrocytes but after incubation with erythrocytes coated with T. pyriformis cilia, 72% of the suctoria had tentacles with attached cells. No untreated, tanned erythrocytes were captured. When T. pyriformis were treated with ciliary antiserum and then offered to starved D. collini , the resulting capture rate was low (13%), but T. pyriformis treated with normal rabbit serum were captured at a rate comparable to controls (92%). These results suggest that the prey's cilia and/or their surface macromolecules may facilitate prey capture.     

The Effect of a Eugregarine Gregarina polymorpha (Hammerschmidt) on the Mealworm Larva of Tenebrio molitor (L.)

SYNOPSIS. The larva of the beetle Tenebrio molitor (Coleoptera, Tenebrionidae), commonly referred to as the mealworm, harbors considerable numbers of gregarines in its midgut. These are not necessary for normal growth, nor do they prolong the life of larvae grown under optimal conditions of temperature, relative humidity and diet. When the larvae were grown under optimal conditions there was no significant difference between the length of larval life or the final pupal weight of mealworms harboring gregarines when compared with mealworms which had been reared free from gregarines. This applied both to infected and non-infected larvae grown singly and in communal cultures.
When, however, larvae were grown on a sub-optimal diet, the gregarines had a considerable effect on the final pupal weight and the ability of the larva to complete development.     

Climate effects on inter‐annual variation in growth of the freshwater mussel (Anodonta beringiana) in an Alaskan lake

1. Warming trends are evident in many parts of the globe but are especially marked at higher latitudes, with complex effects on the biota that include direct effects on growth potential and indirect effects through food webs. 2. Air temperatures have been increasing over the past 50 years in southwestern Alaska, affecting the growth and population dynamics of many organisms, including a variety of aquatic species such as the freshwater mussel Anodonta beringiana. 3. We collected freshwater mussels from Iliamna Lake, in the Bristol Bay region of Alaska, and measured their shells to examine climatic effects on growth patterns. 4. Linear mixed effects models and ordinary least square linear regressions revealed strong positive correlations between local air temperatures (especially in May, October and the summer months) and inter‐annual variation in mussel growth. Slower mussel growth was also significantly correlated with later date of ice break‐up, which was linked to air temperatures in late spring.     

Myxosoma pendula n. sp. (Protozoa,Myxosporida) from the Creek Chub Semotilus atromaculatus*

SYNOPSIS. A new species, Myxosoma pendula, was found surrounded by tissue fluid with granulocytes in pedunculated cysts formed from the mucous membrane of the gill arches of Semotilus atromaculatus collected in the Kewaunee River in Wisconsin. This species has a spherical vegetative stage with 2-layered ectoplasm composed of an outer homogeneous layer and an inner layer with canaliculi, and avoid spores that differentiate in the central area of the endoplasm.     

OLFACTORY RESPONSIVENESS TO DIACETYL

Odor thresholds in the headspace over aqueous solutions of diacetyl (butane-2,3-dione) were measured in quadruplicate by a forced-choice procedure in 53 individuals. Mean individual thresholds varied over a factor of 256, with the group average at .005 μg/ml. Thresholds showed a modest negative correlation with suprathreshold intensity ratings. Intensity ratings were distributed bimodally, consistent with the existence of insensitive and sensitive groups and suggesting the possibility of a specific anosmia for this compound.     

Predicting spatial and temporal patterns of bud‐burst and spring frost risk in north‐west Europe: the implications of local adaptation to climate

The timing of spring bud‐burst and leaf development in temperate, boreal and Arctic trees and shrubs fluctuates from year to year, depending on meteorological conditions. Over several generations, the sensitivity of bud‐burst to meteorological conditions is subject to selection pressure. The timing of spring bud‐burst is considered to be under opposing evolutionary pressures; earlier bud‐burst increases the available growing season (capacity adaptation) but later bud‐burst decreases the risk of frost damage to actively growing parts (survival adaptation). The optimum trade‐off between these two forms of adaptation may be considered an evolutionarily stable strategy that maximizes the long‐term ecological fitness of a phenotype under a given climate. Rapid changes in climate, as predicted for this century, are likely to exceed the rate at which trees and shrubs can adapt through evolution or migration. Therefore the response of spring phenology will depend not only on future climatic conditions but also on the limits imposed by adaptation to current and historical climate. Using a dataset of bud‐burst dates from twenty‐nine sites in Finland for downy birch (Betula pubescens Ehrh.), we parameterize a simple thermal time bud‐burst model in which the critical temperature threshold for bud‐burst is a function of recent historical climatic conditions and reflects a trade‐off between capacity and survival adaptation. We validate this approach with independent data from eight independent sites outside Finland, and use the parameterized model to predict the response of bud‐burst to future climate scenarios in north‐west Europe. Current strategies for budburst are predicted to be suboptimal for future climates, with bud‐burst generally occurring earlier than the optimal strategy. Nevertheless, exposure to frost risk is predicted to decrease slightly and the growing season is predicted to increase considerably across most of the region. However, in high‐altitude maritime regions exposure to frost risk following bud‐burst is predicted to increase.     

VISUAL HAZE DETECTION THRESHOLD ASSESSMENT BY ASCENDING METHOD OF LIMITS AND A TRANSFORMED STAIRCASE PROCEDURE IN APPLE JUICE SIMULATIONS UNDER " STORE LIKE" CONDITIONS

Visual haze detection thresholds were assessed in thirty panelists by two methods: the ascending method of limits and a transformed staircase procedure (UDTR, from Wetherill and Levitt 1965). The 3AFC test was used as the response procedure for both methods. Experimental samples consisted of an apple juice simulation (water with food coloring). Haze was added to the samples using formazin, and was calibrated to eleven levels ranging from 0.75–13.30NTU. Haze detection thresholds under store-like conditions (3.55 ± 0.57 [mean ± S.E.] and 3.16 ± 0.50 NTU by the two methods, respectively) were higher than those found previously under more controlled viewing conditions. No differences were found between methods, genders, or order of method presentation ( p > 0.05); a practice effect showed a slight improvement in detection thresholds between sessions ( p = 0.05). Nonparametric tests confirmed the similarities in the threshold estimates from the two methods. The two methods estimated visual haze detection thresholds equally well. However, the ascending method of limits may be preferred method due to the shorter time involved in administration.