Dear Vidar,
There are published photos of natal increments (for example my paper in J mar Biol Assoc UK 1986). There is a paper by Arkhipkin and Bizikov where statoliths counts and gladii conts were compared. But there is a paucity of such data in the literature. Daily, more than daily or sub-daily? There is no shortage of published evidence, but little physiological explanation. First evidence and argument of non-daily increments came from Claude Morris' PhD (1988) and there is a number of discussions about that in the literature. In the absence of a hard physiological explanation, it is always advisable to do good validation of one's counts each time.
Best
Marek
----- Original Message -----
From: "Vidar Öresland" <[log in to unmask]>
To: "FASTMOLL" <[log in to unmask]>
Sent: Friday, February 17, 2023 1:30:34 PM
Subject: cephalopod hatch rings
Hello,
Thank you all for your kind suggestions, references etc! I will soon mail you privately.
Three more things:
1. Does anyone have photos of the first hatch ring in beaks, statoliths etc (ideally from the same individual) that can be sent to me?
2. Any papers where the ring counts and hatch rings on both statoliths, beaks etc, have been done on the same individuals? To me it looks that this the obvious check that should always be done on at least some individuals in any study. If one gets different results there is a problem that need to be addressed.
3. Ring counts can be close to daily during constant conditions (see e.g., ref below) but to me the temperature and food availability in the environment that the cephalopods meet at different seasons and during vertical migration (daily to life cycle dependent) are far from constant (especially in temperate areas). Experiments (see e.g., references in Jaruwat Nabhitabhata 2022 paper) have shown that the formation of increments can be far from daily at e.g. different temperatures. So, my question is: How useful is ring counts from wild caught specimens when we e.g., want to estimate hatch periods and growth in temperate areas ?
Regards
vidar
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