Title Evolution of maternal investment strategies for the Common cuttlefish, Sepia officinalis, based on the environmental risk factors. Author Jessica Smith: jns@mail.usf.edu
Abstract Common cuttlefishes (Sepia officinalis) are short lived and females typically only have one spawning event in their lifetime. Each female can produce anywhere from 1000-3000 eggs per event. There is no maternal provisioning after the eggs have been distributed. Egg quality and egg quantity is compared graphically to determine the risk and investment strategy utilized by the common cuttlefish. It can be concluded that predation is far more likely cause of death for cuttlefish than starvation.
Introduction The common cuttlefish (Sepia officinalis) is one of the largest species of cuttlefish; their distribution ranges from the Atlantic, to the North Sea, the Mediterranean and even to northwestern Africa. They cuttlefish habitat is muddy bottoms around 200m in depth; however females come to near shore shal waters to spawn. Cuttlefish are in the Mollusca phylum and belong to the unique class of Cephalopoda, which includes squid and octopuses. The maximum mantle length of adult males is 300mm and 250mm for females. The egg size of this species is ly variable depending on the mantle length of the mother. Typical variance is 6-9mm in diameter. The females can produce anywhere from 1,000-3,000 eggs in on spawning event which also depends on size. Typically the larger the female the more eggs she is able to produce. The eggs are laid in the benthic region and ink is added to the yolk for additional protection. Cuttlefish are intermittent spawners; they reach sexual maturity at 14-18months and have a lifespan of 1-2years, typically only breeding once. Hatchling size is a total length of 50mm, and they grow rapidly. Methods Data on fecundity was located in Fecundity of the common cuttlefish, Sepia officinalis L.: a new look at an old problem. Data were analyzed and plotted using Excel. The relative body size of offspring at independence was estimated as fols: S x = m x, M Where 0 S 1 S x = expected probability of offspring mortality based on cycles of food scarcity; M = mass of mother at the time of offspring independence; m x = mass per offspring at the time of its independence.
Offspring number was used to estimate the probability of offspring mortality by predation. P(N) = 1 (2/N) Where N 2 and 0 P 1 P = expected probability of offspring mortality by predation; 2 = expected lifetime fitness per mother; N = the number of offspring produced by a mother per clutch or lifetime. Results Offspring quality was estimated by using the average weight of 46.1mg for the egg, with a diameter of 6mm. The average maternal weight at spawning was 844.5g and a body length of 250mm. The relative offspring quality was calculated to be 0.024, which also represents the percent of death due to starvation (~2%). Average offspring quantity is known to be 2,000 eggs per spawning event. The probability of death by predation was calculated to be 99.9%. This was calculated from the equation 1 (2/2,000). From this data we can conclude that the cuttlefish offspring are far more likely to face death by predation rather than starvation. See figure 1.
Common Cuttlefish Maternal Investment Probability of Starvation 1 0.1 1 10 100 1000 10000 100000 100000010000000100000000 0.01 0.001 RelativeOffspring Size Probability of predation Offspring Number Figure 1: The maternal investment strategy by the common cuttlefish has likely been shaped by environments with >.99 probability of death by predation, but < 0.024 probability of starvation. Discussion The common cuttlefish preys on mostly crustaceans and smaller fishes. Cuttlefish can camouflage themselves by changing the color and texture of their body, this als them to be very efficient hunters. The cuttlefish s primary natural predators are larger fish, such as monks, swordfish and sharks. Common cuttlefish are found in the sublittoral zone in depths up to 250m, they migrate toward shore to spawn. They place their eggs on the benthic region and their dark color and location partially protects them from predators. The mother offers no protection to the eggs after they are laid. The hatchlings
have no larval phase they are miniature forms of adults. The probability of predation is much er than the probability of starvation.
References Food and Agriculture Organization of the United Nations. (n.d.). Aquatic Species: Sepia officinalis. Retrieved October 20, 2013, from http://www.fao.org/fishery/species/2711/en Laptikhovsky, V., Salman, A., Önsoy, B., & Katagan, T. (2003). Fecundity of the common cuttlefish, sepia officinalis l. (cephalopoda, sepiidae): A new look at an old problem. Scientia Marina, 67(3), 279-284. doi:10.3989/scimar.2003.67n3279 Nabhitabhata, J. (1995). Mass Culture of Cephalopds in Thailand. World Aquaculture, 26(2), 25-29. Sussex Inshore Fisheries and Conservation Authority. (n.d.). Common cuttlefish: Sepia officinalis (l.). Retrieved October 20, 2013, from http://sussexifca.gov.uk/index.php?option=com_content&view=article&id=67:commoncuttlefish-sepia-officinalis&catid=15:speciesold&itemid=163 Wood, J. B. (1998). Cuttlefish Husbandry: Part IV - How Do Cuttlefish Reproduce? The Cephalopod Page: National Research Center for Cephalopods. Retrieved October 20, 2013, from http://www.thecephalopodpage.org/cuttle4.php