Gonodactylus
07/26/2013, 11:40 AM
I was recently asked how fast N. wennerae grow and how old do they get. I don't have good data for N. wennerae, but I do for a very similar species, N. bredini. Some of this information is buried in the sticky on molting, but since I wrote a reply, I thought it might be useful if I posted it again.
In gonodactylids, growth, measured as total length, is a function of the frequency of the molt and percent growth at each molt. (To get data before and after a molt, I measure the length of the old and new carapace.) Both decrease with age. but do not stop. For N. bredini, new recruits (7-10mm) grow 10 -15% (total length) each molt and molt every two weeks. At 15mm they molt monthly and grow around 10% Size at first reproduction is around 25-30mm and they can reach this size in a little over a year molting ever couple of months and growing 7-10%. 40mm animals are around 3 years old, grow 5% and molt every 3 or 4 months. 50mm animals grow 3-5% and molt every 4-5 months. Males may grow faster than females at larger sizes because females are not molting when they have eggs (every couple of months). However, there are very few large males in the population because they are picked off by predators when they abandon their cavity to their mate brooding eggs. These data are derived from a healthy, but cavity limited population in Panama. When competition for food and shelter is less, growth is a bit greater.
There are a few published estimates of age in gonodactylids that are much longer than mine. I believe this is due to the fact that animals were maintained in the laboratory and grew less per molt and molted less frequently. My data are obtained primarily from animals that were collected in the field with molt skins so the molt frequency and percent growth estimates are not influenced by capture. This was possible because over a period of 15 years we collected over 100,000 N. bredini from one population at Galeta, Panama. This gave us data on hundreds of animals collected with their molt skins.
Roy
In gonodactylids, growth, measured as total length, is a function of the frequency of the molt and percent growth at each molt. (To get data before and after a molt, I measure the length of the old and new carapace.) Both decrease with age. but do not stop. For N. bredini, new recruits (7-10mm) grow 10 -15% (total length) each molt and molt every two weeks. At 15mm they molt monthly and grow around 10% Size at first reproduction is around 25-30mm and they can reach this size in a little over a year molting ever couple of months and growing 7-10%. 40mm animals are around 3 years old, grow 5% and molt every 3 or 4 months. 50mm animals grow 3-5% and molt every 4-5 months. Males may grow faster than females at larger sizes because females are not molting when they have eggs (every couple of months). However, there are very few large males in the population because they are picked off by predators when they abandon their cavity to their mate brooding eggs. These data are derived from a healthy, but cavity limited population in Panama. When competition for food and shelter is less, growth is a bit greater.
There are a few published estimates of age in gonodactylids that are much longer than mine. I believe this is due to the fact that animals were maintained in the laboratory and grew less per molt and molted less frequently. My data are obtained primarily from animals that were collected in the field with molt skins so the molt frequency and percent growth estimates are not influenced by capture. This was possible because over a period of 15 years we collected over 100,000 N. bredini from one population at Galeta, Panama. This gave us data on hundreds of animals collected with their molt skins.
Roy