Let me tell you about bluebanded gobies.  In this hermaphroditic species, the greatest number o

Let me tell you about bluebanded gobies.  In this hermaphroditic species, the greatest number of offspring are produced when most of the fish are laying eggs.  So they form mating groups or families, typically of 3-7, in which one of the gobies’ bodies shifts to sperm-producing mode, and the rest shift to egg-laying mode.  The fish that takes on the inseminating mode needs to be robust, because it must continuously mate with the rest of the fish.  When mating groups form or change, the members all swim about actively, zipping toward one another.  (Actually, this behavior is quite common, and regularly occurs between all of the bluebanded gobies, including the egglaying ones in established groups.)  What determines which goby in a new group will take on the sperm-producing role is the behavior of the other fish.  A goby being zipped at by a zippier fish will dodge out of the way.  This gets called “submission” by scientists, but could just as well be termed “peacekeeping,” and would most accurately be simply called “getting out of the way.”  By engaging in this dance of zipping about, a new group of gobies determines which of the fish is the most energetic and robust.  Often it’s a large fish, but that’s not always the case.  That fish shifts to sperm-producing mode (unless it is already in that mode), and the others shift to egg-laying mode (unless that is already the case). This story is sadly distorted in most sites and articles about the bluebanded goby.  To find out more, see my full post here. -- source link

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