Sex – Cuttlefish Style
July 6, 2000 | Posted in: Cephalopods
Whyalla’s self-proclamation as the “Cuttle Capital” of Australia is absolutely true, for three months of the year – winter. From May to August, giant cuttles (Sepia apama) migrate from all over (scientists aren’t sure how far) to gather in False Bay, Whyalla and have a three month long sexfest!
I went to Whyalla with eleven other divers to experience this awesome spectacle. We went first to the most famous spot to see the cuttles, an inconspicuous-looking place simply called ‘the Fenceline’ (guess why). The sea was glassy calm and the sun was shining, we could not have ordered better weather. We kitted up and plodded our way down to the water, dreading the cold! In only 2m of water we started to see cuttles and at 4m who needed to go deeper? There they all were, hundreds of them, in all their glory, we could hardly move without inadvertently touching them or kicking them with our fins. What I loved about this spot was that it would have been safe for children too.
Adjectives are poor things to use in describing this sight! There were cuttles of all sizes displaying numerous behaviours – courtship, aggression, sex, protection, egg-laying, sleeping, just about everything except eating! Even with 14-16 divers in the water with them they could not have cared less that we were there. Those creatures have a one-track mind at this time of year and there is a feeling of desperation in the water as the process continues both day and night. Oh yes, we braved the icy night to watch the critters and there they were, still flashing away – but what is it that they can see that we cannot? We can’t see their flashes at night without our torches, so is there some kind of UV or IR signal that our eyes are too simple to pick up? The entire cephalopod family (consisting of nautilus, squid, cuttles and octopus) has very complex eyes, in some respects better than human eyes! They can most certainly see in colour with great acuity.
We were able to lie down on the rocky bottom and watch a group of cuttles interacting. Courtship seemed to consist of several activities, first up it is literally eyeing up another cuttle, they line up side by side and one will display to the other, never at the same time. The flashing display consists of only the side of the body facing the other cuttle producing a continuous series of black and white <-shaped stripes, originating in one corner of the body near the head and radiating out towards the rear. It is very difficult to describe. After this initial contact the other cuttle will decide whether to move on to the next step or disappear. The next step is not so clear, I saw several different sequences of steps. If the cuttle that did not display stays around, then sometimes they will also display while the other one watches. Then there is sometimes some special, gentle touching with the tentacles or some "dancing". The touching was one of the most beautiful and moving behaviours. Generally it was the smaller of the two cuttles that would move towards the other one and very, very tentatively reach out with most of its tentacles to gently touch the tentacles of the other cuttle. It was so amazingly gentle and delicate, like the way human adults touch babies in case they cry or break. The "dancing" was any kind of movement that consisted of both cuttles still looking at one another and swimming, either in circles or just in a seemingly random movement. There might be other behaviours associated with courtship that we did not observe, but generally after all these behaviours have been approved by both cuttles (yes it is a mutual decision) they latch on head to head. They may spend up to 5 minutes or so locked like that while the male deposits sperm inside the female with a special appendage on one of his tentacles. While they are locked like this they will generally stop swimming and settle on the substrate, unless one or both are startled in which case they will stay locked but swim away. After this lengthy procedure, the female will start to lay eggs, but none of us is quite sure how long after mating she does this. However, any female we saw laying eggs was jealously guarded by a male, most likely her mate, so he must stick around after sex! The male will fend off up to 6 other males at any one time. He stretches out to his full length and will (and this is the confusing bit) display the same black and white flashing that we all thought was courtship display. Now, as previously mentioned they were flashing at night too, so maybe whatever it is that they see that we can't changes but the black and white stays the same - I don't know! When a female is laying it is very obvious, not only to the male that she is guarded by as she tightens all her tentacles in a close bunch under her body and her entire head turns white. She looks as if she is really straining and struggling! Then when ready to deposit an egg, she will stretch out her tentacles to the underside of a rock that she has chosen and deposit an egg by attaching it to the rock. The eggs are obvious, they are large white round things that look like they could be some kind of bizarre ascidian. We couldn't tell whether each egg was one egg or many, but I suspect they each only contain one embryo. The variety of colours blew us all away, even me and I half knew what to expect. The few cuttles that chose not to participate in the mating activities displayed extraordinary camouflage amongst the Ecklonia. Between us we must have seen every colour in the rainbow - if only we could decipher this extraordinary form of communication!! I'm sure we all support Whyalla's bid to make this special place a Marine Protected Area. In fact an American marine biologist says he has been searching for something like this around the world for 15 years! So it has global importance too! I must admit to being a complete wuss and only doing three dives, everyone else did much more. However my last dive was completely different to where the cuttles were mating. The habitat where the cuttles were doing their thing, was rather a boring rocky substrate with a couple of sponges and ascidians, lots of one kind of urchin (some of which had cuttle eggs stuck on their spines) and some brown algae, not very diverse. We were on the side of a small peninsula, at the end of which is a beautiful lighthouse and dolphins on the side! There are actually eight pods of resident dolphins in the Whyalla area - what more could you want?! Anyway, the last dive was on a tyre reef, built especially for divers quite a few years ago. There is a small triangle within a large triangle, with old cars marking the corners. It is an area of moderate current flow so the habitat was dominated by filter feeders of every variety. There were zillions of different sponges, soft corals, ascidians, sea stars, cucumbers, pencil urchins. Fish included pygmy and full-size leatherjackets, a large porcupine fish, moonlighters, magpie perch, "grubs" and blennies. Other creatures included razor "fish" (I think I will start a personal lobby to change this name!), hydroids and filamentous red algae. The rest is all written down at home with my dive gear, but the list goes on. We went down to about 15m where it was very cold indeed and we could all feel the temperature change on the way back up. Whyalla may not be much to look at on the land, but under the water lay hidden treasures just waiting to be discovered. As I have repeated to so many people over the last few weeks, it was like watching a nature documentary, but instead of a flat two dimensional screen, we were right inside, watching a glorious three dimensional technicolour show!
After attending a Sea World show, Alexandra Gaut knew that she had to work in marine conservation. For the past 15 years, she has learned all facets of the field and has become a recognized leader who works tirelessly to protect and preserve Australia’s natural environment. Alex Gaut is currently the biodiversity program manager for Conservation Council of South Australia.