Abstract

In this paper we review the research on aquatic and terrestrial isopods

during the last four decades at the Chair of Zoology, Department of Biology, Biotechnical

Faculty, University of Ljubljana. Isopods have attracted substantial attention from

our research team in the following areas: functional morphology and developmental

biology, host-microbiota specific interactions, ecotoxicology, and systematics and

evolution. We present the rationale for using two isopod species as our central model

organisms: the waterlouse ( Asellus aquaticus ) and the woodlouse ( Porcellio scaber ).

We summarize the most important and interesting findings about the structure and

function of the integument and digestive systems of several amphibious and terrestrial

woodlice species during molting and developmental stages, the importance of P. scaber

as a model organism in the study of arthropod-microbe interactions, and its central role

as a test model in terrestrial ecotoxicity studies. We highlight the role that A. aquaticus

has played in studying the evolution of subterranean biodiversity and in the evolution

of troglomorphies. In addition to the retrospective view on our research with isopods

we also present the scope of our future research, and the importance for zoology (biology).

We wish to dedicate this work to our late co-worker, Prof. Dr. Pavel Ličar, who

devoted much of his research into studying the digestive system of freshwater asellids

(Isopoda: Asellota).

Keywords

isopods, terrestrial, aquatic, functional morphology, developmental biology, host-microbiota interactions, terrestrial isopod, aquatic isopod, ecotoxicology, systematics, evolution

Abstract

In the fluorescence microscopy of biological specimens the structures

in cells and tissues usually need to be labelled with various fluorescent markers. The

three main groups of fluorescent markers are small organic fluorochromes, fluorescent

proteins and quantum dots. Fluorescent markers differ according to photophysical

properties and binding specificity for the selected target structures in the sample. For

the labelling of specific structures with small organic fluorochromes or quantum dots

it is usually necessary to conjugate them with target specific macromolecules. For the

labelling with fluorescent proteins it is necessary to introduce a fluorescent protein

gene into the observed cells or organism. The most important photophysical properties

of fluorescent markers are absorption and emission spectra, Stokes shift, extinction

coefficient and quantum yield. Currently, various super-resolution fluorescent microscopy

techniques exploit special fluorochromes that enable fluorescence modulation by

specific wavelength illumination, to achieve the resolution below the diffraction limit.

Keywords

organic fluorochromes, fluorescent proteins, quantum dots, fluorescence microscopy, labelling

Abstract

Terrestrial isopods of the family Trichonscidae possess calcium bodies,

epithelial sacs that accumulate calcium minerals. Previous studies have demonstrated

that two pairs of these organs are present in the species Titanethes albus and Hyloniscus

riparius . In T. albus , all calcium bodies are filled with bacteria, whereas only

the posterior pair of calcium bodies contains bacteria in H. riparius . In the present

work we studied the ultrastructure of calcium bodies in Androniscus roseus and Haplophthalmus

mengei . Two pairs of calcium bodies containing rod-shaped bacteria are

present in both species. The bacteria-containing mineralized matrix is enclosed in a

simple epithelium with a folded apical plasma membrane, which is covered by a thin,

electron dense envelope. Our results show that the presence of bacteria is a general

feature of trichoniscid calcium bodies, which are ultrastructurally similar. A combination

of bacteria-containing calcium bodies and calcium bodies lacking bacteria has

only been found in the genus Hyloniscus , in which bacteria-free calcium bodies likely

functionally replace sternal CaCO 3 deposits.

Keywords

Trichoniscidae, biomineralization, symbiosis, crustacean

Abstract

The catchment area in urban and agricultural landscapes is greatly influenced

by human activities that reflect also in physical and chemical characteristics

of water as well as in species diversity in waterbodies. The diversity and the species

composition of epilithic diatom communities in the Savinja River, as well as basic

environmental parameters were analysed. Sampling sites were selected in reaches

subjected to different influences from the catchment area and with different physical

and chemical characteristics. Samples were collected at the site where the Savinja

River enters the urban area of the town Celje, at the end of urban landscape and

downstream of the Celje waste water treatment plant outflow. The most common and

dominant diatom species in the periphyton community was Achnanthes biasolettiana.

Other common diatom taxa that were found in all samples and at least in one sample

exceeded relative abundance of 10% were Nitzschia fonticola, Amphora pediculus and

Nitzschia dissipata. The results of the redundancy analyses (RDA) revealed that the

variance of the epilithic diatom community was explained by O2 saturation (35%) and

saprobic index (33% of TVE). Diatom species richness was positively correlated with

O 2 saturation. Shannon-Wiener diversity index was positively correlated with saprobic

index values based on all algae and trophic index calculated on the base of diatoms

indicating a relatively low organic matter and nutrient input into the river system. The

results showed that no significant changes in epilithic diatom species composition and

no negative impacts on diversity of epilithic diatom community in the Savinja River

were detected on its flow through the urban landscape. Moreover, changes between

the seasons were more evident than changes between sampling sites, confirming the

importance of sampling date for monitoring.

Keywords

Diatoms, microphytobenthos, periphyton, environmental factors, t orrential river

Abstract

Little information is available for aquatic plants regarding their architectural

response to strong environmental drivers like water flow. We examined

architectural variability in Myriophyllum spicatum L. in the short terminal section of

a small canal earlier used for inland navigation. This stretch is characterised by decreasing

water depth towards a final spill-over construction, which causes increasing

current velocity. Visibly different plant beds had developed at three sampling sites,

located between the upstream end of the study reach and the end at the spill-over. This

situation bears some resemblance to an experimental flume due to regulated water

flow and constant discharge, yet with aquatic plant beds still located in their permanent

environment during the whole year. Following this precondition our hypothesis

envisaged a close relationship between current velocity and realised plant architecture.

Current velocity was measured with an electronic vane device, and representative architectural

features of plants were recorded from plant samples at the sites of different

flow. Characteristic and significant variation in the architecture of M. spicatum was

demonstrated at the sites of different current impact. Regarding other environmental

parameters like sediment composition, water chemistry or the effect of shading no

influence seems likely expected, as samples were collected across the canal width at

each site. The mean values of all architectural parameters of M. spicatum follow the

same trend with high significance, regarding the increase in plant length, branching,

and the overall dimension of the plant beds, which is in close relationship to the current

velocity at the sampling sites. The few other records available in literature cited

in this paper point into the same direction, but these studies were also carried out in

the field. In our opinion the clear results may not comply with a final and experimentally

generalised relationship between aquatic plant architecture and water flow. But

our contribution offers some statistical proof that our hypothesis is not too far from

explaining the effects of current velocity, which is one of the main environmental

parameters defining aquatic plant growth.

Keywords

aquatic macrophytes, water flow velocity, architectural adaptation, Myriophyllum spicatum