Species-specific Scale Research Articles

A unique Late SilurianThelodussquamation from Saaremaa (Estonia) and its ontogenetic development

A partly preserved squamation of Thelodus laevis (Pander) from the Himmiste outcrop (Saaremaa Island, Estonia) is described. Most of the trunk with a pectoral fin fragment and three fragments of posterior fins are present, while part of the head and the caudal fin are absent. Ontogenetic development of the scale cover of T. laevis is explained by comparing it with the squamation of Lanarkia horrida Traquair, Loganellia scotica (Traquair) and a modern fish. It is supposed that newly forming trunk scales of early juvenile Thelodus were smooth and rhomboidal. When the individual grew, ridged scales were added between smooth ones in irregular rows in the posterior part of the trunk. Adult individuals were covered with species-specific scales with particular morphology and sculpture of the crown. Co-occurrence of smooth and ridged scales on the trunk in the specimen studied corresponds to a young stage of ontogeny.

A Re-Evaluation of Reineke's Rule and Stand Density Index

Abstract The self-thinning rule established by Reineke in 1933, N α d−1.605 (N, d = number of stems and quadratic mean diameter, respectively) assumes the same allometric relationship between size and density for a wide spectrum of species under self-thinning conditions. We re-evaluate this rule based on 28 fully stocked pure stands of common beech (Fagus sylvatica L.), Norway spruce (Picea abies [L.] Karst.), Scots pine (Pinus sylvestris L.), and common oak (Quercus petraea [Mattuschka] Liebl.) in Germany that date back to the year 1870. OLS regression of the model ln(N) = a + b · ln(d) results in b values of −1.789 for common beech, −1.664 for Norway spruce, −1.593 for Scots pine, and −1.424 for common oak. The allometric coefficient for common beech differs significantly from the other species. There is also a significant difference between the b values of Norway spruce and common oak. Except for Scots pine, the above allometric coefficients deviate significantly (common beech) and close-to-significantly (Norway spruce, common oak) from the coefficient −1.605 postulated by Reineke in 1933. To cover the species–specific oscillation of mortality rates, we additionally calculate the self-thinning coefficient for each survey period. Ecological implications of the species-specific scaling exponents are stressed and consequences regarding tools for regulating stand density are discussed. FOR. SCI. 51(4):304–320.

Siliceous protozoan plates in lake sediments

The silicified plates of certain testate amoebae have the necessary characteristics to be useful paleoindicators. These plates are usually abundant and well preserved in sedimentary deposits, where they can be studied using the same preparation techniques developed for other siliceous microfossils. Individual plates can usually be identified to the generic and, in some cases, to the species level. A preliminary survey of plates recorded in the surficial (top centimetre) sediments of 38 Adirondack Mountain (NY) lakes suggests that these testaceans may reflect catchment features (e.g. bog development) more closely than lakewater characteristics. The siliceous, species-specific scales of heliozoans are also shown to preserve in sedimentary profiles.