Hannen parrer sig med hunnen lige efter at hun har skiftet skal da hun der er blød. Foto: Ar rouz CC BY-SA 3,0, Wikimedia
I Danmark har vi over 7000 km kyststrækning. Her kan man finde masser af spændende dyr og planter. Et af dem er strandkrabben.
Danmarks almindeligste krabbe. Strandkrabben (Carcinus maenas) er den mest almindelige krabbe i Danmark og også den vi oftest støder på ved fjorden og havet. De fleste børn og barnlige sjæle har prøvet at fiske efter krabber. Det er en oplagt aktivitet med børn gerne fra en mole eller badebro. Man tager blot en snor med en tøjklemme, hvorpå madingen sættes fast f.eks. et stykke pølse eller en musling. Begejstringen kan være stor når en af krabberne bider på, men faktisk er strandkrabben ikke særlig aktiv om dagen. De er nemlig nataktive. Om dagen vil den helst gemme sig bag nogle sten eller lignende og er det ikke muligt graver den sig gerne ned i sandbunden så kun klosakse og hoved ses.
Kan smide et ben i forsvar. Som de fleste nok er bekendt med har strandkrabben to kraftige klosakse. Primært bruges de til at fange og fastholde bytte med, men de kan også bruges til forsvar.
Strandkrabben har dog et ekstra forsvar udover sine klosakse og sit skjold. Hvis en fjende griber fat i et af krabbens ben, kan den smide benet – næsten som et firben, der taber halen. Imens fjenden har fokus på benet, kan krabben ofte nå at stikke af. Et nyt ben vokser ud igen efter 2-3 skalskifte. Da krabben ikke har et indvendigt skelet, men et udvendigt skjold skal det skiftes i takt med at krabben vokser. Når krabben lige har skiftet skal er den ekstra sårbar og blød og derfor gemmer den sig. Som voksen skifter krabben skallen en gang om året, men de første leveår sker det hele 14-17 gange om året.
Strandkrabben kan variere en del i farverne. Foto: taget med undervandskamera CC BY-SA 3,0, Wikimedia
Fakta om strandkrabben:
Skjoldet er op til 7 cm bredt, femkantet og med kraftige savtakker i forenden.
Strandkrabben har ti ben, hvoraf de forreste to er udviklet til kraftige klosakse.
Bagkroppen er flad og trykket op under krabbens underside. Hunnens bagkrop er bred mens hannens er smal og spids.
Den kan variere i farven, men er oftest brunlig eller grønlig.
Den har ikke et indvendigt skelet, men et udvendigt; nemlig skjoldet.
Dens naturlige fjender er blandt andet måger, edderfugle og skrubber. Når den lige har skiftet skal og er blød er den også udsat for angreb fra eksempelvis hummere, ulk, ål eller andre krabber.
Vidste du;
Den bedste måde at holde krabben på er med flad hånd. Foto: S. Rae CC BY 2,0, Wikimedia
At den bedste måde at holde en krabbe på er i en flad hånd? Krabber napper kun når de føler sig truet og hvis man holder ovenpå skjoldet vil krabben forsøge at forsvare sig med kløerne.
At man i Danmark kender til 23 forskellige arter af krabber?
At krabber løber sidelæns fordi det er den hurtigste måde for dem at komme frem på? Krabberne er bredere end de er lange hvilket giver dem mindst vandmodstand ved sidelæns løb.
At krabbens flade og brede form gør det nemt for dem at grave sig ned i sandbunden?
At krabber stort set er altædende?
At strandkrabbens hoved og krop er sammenvokset? Den kan derfor ikke bevæge sit hoved, men bevæge øjnene fra side til side.
At strandkrabbens lugtesans sidder på dens to følehorn og det er dem den bruger til at finde føde med?
MR/
Kilde: fugleognatur.dk, fjordbaelt.dk, skaldyrscenter.dk, naturhistoriskmuseum.dk. Featured foto: Strandkrabbe, foto: D. Hazerli CCO, Wikipedia.
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