dashed lines of dazzling iridescent blue . They are usually found in groups with each one sitting in the small pit it has eaten into the kelp . The groups can be particularly obvious in the autumn , as they tend to congregate before moving down the kelp to avoid being cast adrift in winter storms . It seems I ’ m not the only one who finds these distinctive miniature molluscs appealing . When I recently posted a portrait of them on a kelp frond on social media , it got even more positive reactions than the usual obvious vote-winners like cuttlefish , blennies and catsharks .
Kelp can also be a very good place to spot those more well-known , attractive molluscs , nudibranch sea slugs . Nudibranchs are carnivores and often very specific in their choice of prey , with some species specialising on bryozoans . Particularly where kelp fronds are covered with the mesh-like sea mat colonies , you can find these slugs feeding , mating and laying their egg strings . With such a flat background behind them , it can also be an ideal location to observe how these animals are exemplars of total equality . Every individual sea slug is a hermaphrodite , both male and female at the same time , so if a couple are joined together by their right-hand sides , they are likely to be fertilising each other with both going on to lay eggs .
Shore sea urchin getting ready to spawn
Echinoderms such as starfish and sea urchins use kelp for romance too , albeit of a much more remote kind than the nudibranchs . They crawl up to a high vantage point on the kelp to release clouds of spawn , eggs or sperm , that can drift away in the current . Chemicals discharged with the animals ’ spawn are thought to encourage neighbours to do likewise and so maximise the chances of reproductive success .
Some of my favourite finds on kelp are the mobile predators that use the elevation from the seabed to their advantage . Sea scorpions sometimes
nestle into the fold of a kelp frond , where they adopt a kelpy colour for camouflage . Here , I am sure these ambush hunters are waiting for small fish such as groups of hovering two-spotted gobies to come within range . Great ( or ‘ sea toad ’) spider crabs can be seen clambering high up on kelp . After seeing them sometimes devouring pieces of jellyfish , I longsuspected that they might use the lofty position to grab at ‘ low-flying ’ jellies . I recently caught one in the act !
Paul ’ s photos and video clips capturing UK marine life stories are on Instagram @ paulnaylormarinephoto �
Spiny starfish releasing spawn from its vantage point
Spider crab clambering on the kelp
Reciprocal mating between a pair of orange clubbed sea slugs on sea mat bryozoan
A group of lined polycera nudibranchs feasting on sea mat bryozoan
A long-spined sea scorpion waits to ambush its prey
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