biologe

Blog and online journal with editorial content about science, art and nature.

Tag: animal behavior

Isopoda: locomotion and aggregation behavior

Isopods represent Arthropoda. But they are no insects, no arachnids and no myriapods, although the glomerids or pill-millipedes can have a similar shape. Isopods are indeed crustaceans.  And the shape of pill-millipedes is a result of independent evolution (convergent evolution).

Isopoda represent a clade of the Malacostraca, whose members are originally native to aquatic habitats. Also isopods from the phylogenetic point of view represent aquatic/ marine organisms. But one clade, the Oniscidea, also named terrestrial isopods, evolved mechanisms to survive ashore.

The footage shows a species of Oniscidea of genus Porcellio from mediterranean habitats in Croatia. Land isopods retained their gills and thus usually prefer moist habitats. My model-isopods are reared in a terrarium, were they use to aggregate under moist pieces of bark.

As most terrestrial isopods, they are destruents and feed on decaying organic material. I add regularly pieces of fruits or vegetables and thus create conditions comparable with compost. Most of my footage is presented in slow motion.

I thank Jana Bedek, Croatian Biospeleological Society, for her determination of the isopods on a genus level.

Copyrights: Stefan F. Wirth, Berlin May 2017/ November 2018

Orange tip butterfly Anthocharis cardamines

Anthocharis cardamines is a butterfly species, belonging to the big taxon Pieridae. Members of this group with about 1100 species worldwide are typically characterized by a more or less white color. There is even evidence that the popular term „butterfly“ refers to a pierid species, namely the brimstone, Gonepteryx rhamni, which British researchers considered as looking like a butter-colored fly.

The video introduces some morphological characters of a male specimen of Anthocharis cardamines. In this gender the most conspicuous character concerns the orange colored tip on the insides of both wings. That color character represents a sexual dimorphism, as female wings are completely white.

The quite common butterfly is distributed in Europe and temparate Asian zones. Interestingly adult A. cardamines strictly prefer specific habitats, which differ in males and females. While males inhabit the edge areas of forests close to adjacent meadows, females prefer the open meadows. Both genders fly only in a bright sunlight and strictly avoid the shadow, even then, when a suitable host plant for the egg deposition grows in a shady environment. Females select their mating partners using pheromones, which either attract or reject a male. Mated females in order of their egg deposition will always reject male approaches.

Other female pheromones are used as markers to characterize a host plant as already containing eggs. This will prevent a new egg deposition by another female specimen, which happens to improve a positive breeding success, as caterpillars show a cannibalistic behavior against other eggs. Host specificy, mating behaviors and reproductiion are result of evolution.

 

Berlin May/November 2018. Copyrights Stefan F. Wirth

A scarab beetle’s larva and pupa: habitats for mites and other organisms

The micro-world is complex. Its habitats intertwine themselves, some even are unusual, because they are formed by single animal individuals. An example is a holometabolic insect, here the tropical rose chafer Eudicella colmanti. The larvae of my specimens are covered with deutonymphs of an astigmatid mite (Acaridae, eventually Acarus sp.).

This makes the beetle larva to a habitat for these mites, although the mites in this case don’t feed or reproduce there. They instead are „only“ passengers on their transportation to a new „real“ habitat, where they become adult, feed and reproduce. This strategy to be carried by other organisms from one living place to another is called phoresy.

The situation in my terrarium might be artificial in the sense that mites are putatively not of tropical origin as the beetles (reared in Germany) and thus do not originally „belong“ to the beetle species. The mites might have reached into the terrarium via fruit flies or similar native organisms or via the terraria of the online shop, where they were bought. But the mite deutonymphs show a distinct affinity for adult beetles and their larvae nevertheless, which they attached in great numbers (not the pupa). The microscopic footage of the mite deutonymphs contains activities of their genital openings, located close to the sucker plates on their undersides.

They occasionally open and close and discharge secretions or water. This might be due to osmoregulation and/or in order to prove the adjacent sucking structure with moisture for a more stable hold.

The larva after some months built its pupa chamber, consisting of soil particles and larva secretions. Tese pupa chambers offer on their outer sides obviously enough nutrients for collembolans, which appeared there in greater numbers, especially on an older chambers with its pupa waiting to hatch. Mites of the Gamasida and tiny annelids could also be observed there. The video consists of macro fotage and microscopic footage, all recorded in 4K and rendered in an uncompressed quality.

 

Berlin, December 2017/November 2018, copyrights Stefan F. Wirth