Moulting and metamorphosis in insects

Svi kukci se moraju presvlačiti, jer im kutikula ograničava rast. S obzirom na tip metamorfoze, kukci mogu biti ametabolični, hemimetabolični ili holometabolični. Najviše utjecaja na presvlačenje i metamorfozu imaju mozak i žlijezde corpus cardiacum (CC), protorakalna žlijezda i corpus allatum (CA). Iz protorakalne žlijezde se luče fitoekdisoni koji potiču presvlačenje kukca, a iz CA se luči juvenilni hormon (JH) u čijoj odsutnosti počinje proces metamorfoze. Tokom metamorfoze se razvija odrasli kukac. Iz imaginalnih diskova se razvijaju organi karakteristični za odrasle kukce kao što su krila ili ticala. Odrasli kukci su spolno zreli i više se ne presvlače, osim u ametaboličnih kukaca i u slučaju hormonalnog poremećaja.Insects have to moult because their cuticle prevents their growth. Regarding types of metamorphosis, insects can be ametabolous, hemimetabolous or holometabolous. Most influential glands for moulting and metamorphosis are the brain, corpus cardiacum (CC), prothoracic gland and corpus allatum (CA). The prothoracic gland secretes ecdysteroids which are responsible for moulting. The CA secretes juvenile hormone (JH) in the absence of which the metamorphosis starts. An adult insect is developed during metamorphosis. Organs characteristical for adults, such as wings or antennae, are developed from imaginal discs. Adult insects are fertile and no longer moult, except in cases of ametabolous insects and hormonal disorders

Morphological diversity of the stone crayfish − traditional and geometric morphometric approach

Austropotamobius torrentium is one of four native European crayfish species inhabiting Croatian freshwaters. Existence of eight divergent monophyletic mtDNA phylogroups was described within A. torrentium; six of them are distributed in Croatia, with the highest genetic diversity established in its northern-central Dinaric region. Recent small-scale study of the stone crayfish morphological variability indicated significant differences among different phylogroups. In the present study larger sample size, covering populations from five phylogroups, was analysed with the aim of determining whether there are morphological characteristics that reliably separate stone crayfish from different phylogroups. Aiming this, 245 stone crayfish were analysed through traditional (TM) and, for the first time, geometric morphometric (GM) analyses. Multivariate discriminant analyses included 24 TM characteristics per crayfish, while GM comprised analyses of 22 landmarks on the dorsal side of cephalon. Both methods revealed congruent results, and significant differences among phylogroups in analysed features were obtained, with the cephalon shape contributing the most to crayfish discrimination. Research confirmed that both approaches, combined with statistical methods, are useful in distinguishing and separating crayfish phylogroups. Findings of present study are compatible with the previous molecular findings; stone crayfish present several distinct evolutionary lineages whose species status are currently undefined and require urgent clarification