Life of a squid

The heathen at IIDB are talking about squid—it’s infectious, I tell you, and the godless seem especially susceptible—and in particular about this interesting paper on squid fisheries. Squid are on the rise, and are impressively numerous.

We can get an idea of the abundance of squid in the world’s ocean by considering the consumption of cephalopods (mainly squid) from just one cephalopod predator the sperm whale. Sperm whales alone are estimated to consume in excess of 100 million tonnes of cephalopods a year. This is equivalent to the total world fishery catch and probably exceeds half the total biomass of mankind on the earth (Clarke 1983). It is therefore highly likely that the standing biomass of squids within the world’s oceans probably exceeds the total weight of humankind on the earth. Given such importance squid have generally not been given the attention they deserve or have not been incorporated to the degree they need to in ecosystem models. Future research needs to rectify this.

Squid are creatures of speed: they grow fast and die young. Teleosts and cephalopods follow rather different life strategies.

The form of growth of squid is also unique and interesting. Squid just keep growing. They do not show the distinctive flattening in their growth curve shown by their fish competitors. Many species growth can be modeled with exponential or linear curves. The interesting thing is they continue growing even during their maturation phase until they die or are eaten. They seem to achieve this because of a number of unique qualities, (1) they have a protein based metabolism with efficient digestion so food is converted to growth rather than stored, (2) they are efficient feeders, using their suckered arms and beak they can remove only the highly digestible parts of prey and ‘spit out the bones’ and (3) they can grow by continually increasing the number of their muscle fibres (hyperplasia) a feature not shared by their fish counterparts. While juvenile fish recruit new muscle fibres by hyperplasia they reach a point where growth only occurs by increasing the size of existing muscle fibres (hypertrophy). This probably contributes to their flattening growth curve. Alternatively, squid show both hyperplasia and hypertrophy throughout their life span, thus they continue to recruit new fibres as well as increase the size of existing fibres (Figure 1). Such a strategy might account for their continuous growth. All of the above features contribute to the unique form of growth and the ability of squid to grow fast and fill available niches. Their life is very much life-in-the-fast-lane. They are the ‘weeds’ of the sea.

Live fast, die young…and leave a really decrepit corpse, it seems. Here’s a description of a species that really knows how to have a good time.

Much of my Southern Ocean research has focused on the warty squid Moroteuthis ingens. Up until recent years this species was poorly understood and delegated to obscurity due to lack of biological information. However, this species is regularly caught in both fishing and research trawls and my research has focused on New Zealand, The Falkland Islands and more recently Australia’s sub-Antarctic island regions. The biological understanding of this species is now perhaps the best of any sub-Antarctic squid. It is a large squid growing to over 500mm in mantle length and females achieve a much larger size than males. While M. ingens is epipelagic during its juvenile stage it undergoes an ontogentic descent to take up a demersal existence (Jackson 1993). This species has a biologically unusual and interesting reproductive strategy referred to as terminal spawning (Jackson & Mladenov 1994). Although it is a muscular squid, females (and to a lesser extent males) undergo a dramatic change associated with reproduction. Females produce a huge ovary that can reach the size of a rugby ball and weigh as much as a kilogram. In fact the ovary can weigh more than the total body weight of the male. In association with the development of the ovary the female undergoes a dramatic tissue breakdown in its body wall. This process results in a total loss of muscle fibres that transforms the muscular female into something more analogous to a jellyfish and death is associated with spawning. Moroteuthis ingens and other onychoteuthids are important prey for a number of vertebrate predators (at least four mammals, 17 birds, 13 fish, Jackson et al 1998). It is suspected that this tissue breakdown may result in dead individuals floating to the surface where they are accessible to mammals and birds.

Cool stuff…read the whole paper!


  1. says

    Terminal spawning. I didn’t know there was actually a term for that. Back in Alalska, my friend Mr. Whitekeys wrote a song about the plight of the female salmon. It started:

    My life is misery.
    It’s enough to make a young girl cry.
    I swim a thousand miles,
    Meet a guy, we do it once, and die.

  2. Monad says

    So if fish populations do crash (with not a little help from ourselves) could squid start to take over more niches previously occupied by fish (they already seem to dominate some of the more pelagic lifestyles)? I think as well as their advantages in terms of rapid growth and ability to exploit resources they also have greater behavioural and cognitive flexibility than most fish, so they have some advantages when ecosystems are changing rapidly due largely to human intervention and destruction of habitats.

    So maybe this is even the beginning of a major shift and in a few million years squid will have diversified and become dominant lifeforms in the oceans (if they aren’t already in terms of biomass). It would be interesting to consider whether, if intelligent lifeforms are still around then, they would look back and see this as the sort of punctuated event we often see when we look back on the fossil record – with one group crashing and another taking over all in a relatively short space of time.

    People say we can’t see evolution happening – well this is it.

  3. Jay Draiman says


    In order to insure energy and economic independence as well as better economic growth without being blackmailed by foreign countries, our country, the United States of America’s Utilization of Energy sources must change.
    “Energy drives our entire economy.” We must protect it. “Let’s face it, without energy the whole economy and economic society we have set up would come to a halt. So you want to have control over such an important resource that you need for your society and your economy.” The American way of life is not negotiable.
    Our continued dependence on fossil fuels could and will lead to catastrophic consequences.

    The federal, state and local government should implement a mandatory renewable energy installation program for residential and commercial property on new construction and remodeling projects with the use of energy efficient material, mechanical systems, appliances, lighting, etc. The source of energy must by renewable energy such as Solar-Photovoltaic, Geothermal, Wind, Biofuels, etc. including utilizing water from lakes, rivers and oceans to circulate in cooling towers to produce air conditioning and the utilization of proper landscaping to reduce energy consumption.

    The implementation of mandatory renewable energy could be done on a gradual scale over the next 10 years. At the end of the 10 year period all construction and energy use in the structures throughout the United States must be 100% powered by renewable energy. (This can be done by amending building code)

    In addition, the governments must impose laws, rules and regulations whereby the utility companies must comply with a fair “NET METERING” (the buying of excess generation from the consumer), including the promotion of research and production of “renewable energy technology” with various long term incentives and grants. The various foundations in existence should be used to contribute to this cause.

    A mandatory time table should also be established for the automobile industry to gradually produce an automobile powered by renewable energy. The American automobile industry is surely capable of accomplishing this task.

    This is a way to expedite our energy independence and economic growth. (This will also create a substantial amount of new jobs). It will take maximum effort and a relentless pursuit of the private, commercial and industrial government sectors commitment to renewable energy – energy generation (wind, solar, hydro, biofuels, geothermal, energy storage (fuel cells, advance batteries), energy infrastructure (management, transmission) and energy efficiency (lighting, sensors, automation, conservation) in order to achieve our energy independence.
    “To succeed, you have to believe in something with such a passion that it becomes a reality.”

    Jay Draiman, Energy Consultant
    Northridge, CA. 91325

    P.S. I have a very deep belief in America’s capabilities. Within the next 10 years we can accomplish our energy independence, if we as a nation truly set our goals to accomplish this.
    I happen to believe that we can do it. In another crisis–the one in 1942–President Franklin D. Roosevelt said this country would build 60,000 [50,000] military aircraft. By 1943, production in that program had reached 125,000 aircraft annually. They did it then. We can do it now.
    The American people resilience and determination to retain the way of life is unconquerable and we as a nation will succeed in this endeavor of Energy Independence.

    Solar energy is the source of all energy on the earth (excepting volcanic geothermal). Wind, wave and fossil fuels all get their energy from the sun. Fossil fuels are only a battery which will eventually run out. The sooner we can exploit all forms of Solar energy (cost effectively or not against dubiously cheap FFs) the better off we will all be. If the battery runs out first, the survivors will all be living like in the 18th century again.

    Every new home built should come with a solar package. A 1.5 kW per bedroom is a good rule of thumb. The formula 1.5 X’s 5 hrs per day X’s 30 days will produce about 225 kWh per bedroom monthly. This peak production period will offset 17 to 24 cents per kWh with a potential of $160 per month or about $60,000 over the 30-year mortgage period for a three-bedroom home. It is economically feasible at the current energy price and the interest portion of the loan is deductible. Why not?

    Title 24 has been mandated forcing developers to build energy efficient homes. Their bull-headedness put them in that position and now they see that Title 24 works with little added cost. Solar should also be mandated and if the developer designs a home that solar is impossible to do then they should pay an equivalent mitigation fee allowing others to put solar on in place of their negligence.

    Installing renewable energy system on your home or business increases the value of the property and provides a marketing advantage.