Critter of the Week: Grumpy crab Pilumnus novaezelandiae.
Never complain about a bad hair day again! This week’s crab arguably gives more the impression of disbelief than grump, but we love the ‘head shots’ our talented photographer Chazz Marriott produces at sea.
Let us introduce you to Pilumnus novaezelandiae, with the very fitting common name ‘bristled black-finger crab’. These bunches of longer coarse hairs (setae) give the crab a distinctive appearance and make is easily distinguishable from the closely related species Pilumnus lumpinus, which is much more evenly coiffed.
Pilumnus novaezelandiae can be found from the low intertidal to 130 m and hides under boulders and in rock crevices in sheltered harbours and on wharf piles all around New Zealand. It can be found in large numbers and is considered gregarious, perhaps as a consequence of its unusual reproductive strategy (see fun fact below).
It’s not a large species, with a carapace width of up to 20 mm.
Fun fact: Pilumnus novaezelandiae has a much abbreviated development. Eggs are few in number and very large. The larval stage (megalopa) hatches from the egg and young are carried by the female until they moult into the first crab stage. While it is common for freshwater decapods to provide parental care for juveniles, this behaviour is very rare among marine decapods (1).
1) Referceen: McLay (1988) Brachyura and crab-like Anomura of New Zealand:
Mnyama wa Wiki: Pilumnus novaezelandiae, yule kamba mwenye hasira. Kamwe usilalamike juu ya siku mbaya ya nywele tena! Krab ya wiki hii bila shaka inatoa hisia zaidi ya kutokuamini kuliko kukasirika, lakini tunapenda 'picha za kichwa' mchoraji wetu mwenye talanta Chazz Marriott hutengeneza baharini. Acheni tukutambulishe Pilumnus novaezelandiae, aliye na jina la kawaida linalofaa sana <unk>bristled black-finger crab<unk>. Mifuko hii ya nywele ndefu (setae) huwapa krabu sura ya kipekee na hufanya iwe rahisi kutofautisha na spishi inayohusiana sana Pilumnus lumpinus, ambayo ina nywele sawa zaidi. Pilumnus novaeezelandiae hupatikana kutoka chini ya maji hadi mita 130 na hujificha chini ya miamba na katika nyufa za mwamba katika bandari zilizohifadhiwa na kwenye rundo la bandari kote New Zealand. Inaweza kupatikana kwa idadi kubwa na inachukuliwa kuwa ya kijamii, labda kama matokeo ya mkakati wake wa kawaida wa uzazi (tazama ukweli wa kufurahisha hapa chini). Si spishi kubwa, na upana wa carapace ya hadi 20 mm. Jambo la kupendeza: Pilumnus novaezelandiae ina maendeleo mafupi sana. Mayai ni machache na makubwa sana. Mfano wa megalopa (megalopa) hutoka kwenye yai na watoto huchukuliwa na mwanamke hadi wanapochukua hatua ya kwanza ya kuwa kamba. Ingawa ni kawaida kwa decapods maji baridi kutoa utunzaji wa wazazi kwa vijana, tabia hii ni nadra sana miongoni mwa decapods baharini (1). "Mfano: ""Brachiura"" na ""Anomura"" kutoka New Zealand."