goby and shrimp

昨日の明治と早稲田の試合、明治の方が動きが良かったですね。ラグビーはサッカーと違って実力がはっきりとスコアに反映されますね。
さて、東野圭吾の "JOURNEY UNDER THE MIDNIGHT SUN" を読んでいます。
'I would, if I had anything to charge him with. And besides, I know the one place he's most likely to show up - one you're well acquainted with.'
'Where's that?'
'Near Yukiho Karasawa.' Sasagaki wet his lips.' 'Ever heard about the goby and shrimp?'
'Sorry? Shrimp?' Kazunari blinked.
'Never mind. Suffice it to say, Yukiho Karasawa and Ryo Kirihara have what biologists call a symbiotic relationship. One can't live without the other. They're a pair for life.'

"goby and shrimp" の関係は小説内でも説明されているので特に調べる必要はありませんが、ネットを見るとこの "symbiotic relationship" についての紹介は幾つもあります。　その内の一つ、Scuba.comの記事 'The Fascinating Symbiotic Relationship Between Gobies and Shrimp' から引用します。

Before we answer this question, let’s first define what a symbiotic relationship is. Symbiosis is scientifically defined as the interaction between two different organisms that live in close physical association, usually to the advantage (though not always) of both parties.

A symbiotic relationship falls into three main categories:
Mutualism (both organisms benefit from the relationship),
Commensalism (only one organism benefits while the other neither benefits nor gets harmed), and
Parasitism (only one organism benefits at the expense of the other).
The symbiotic relationship between goby fish and snapping shrimp is described as being mutually beneficial. Studies have revealed that about 130 species of gobies are associated with about 20 species of pistol shrimp, the majority of which are found in the Indo-Pacific and nearby regions.

YukihoとRyoの関係は "symbiotic relationship" (共生関係)だと刑事のSasagakiは睨んでいます。私が　"Symbiosis" で連想したのは為政者と宗教です。