Pygmy Squids Females Favor Small Males and Fast Copulation

Females of some species in the wild may not be able to prevent unwanted sex with males. In many crustaceans, males forcibly mate with females who often receive sperm from multiple males. In other cases, females will not reject the male simply because doing so would waste precious energy reserves. When males harass female mosquito fish the efficiency with which the female finds food and consumes it decreases by half. But in both of scenarios the female may still get the last choice in who sires her offspring by make a cryptic choice. Female cryptic choice occurs when a female rids herself of a male’s sperm without his knowledge. Sneaky and effective.

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From Sato et al. 2013

In the Japanese pygmy squid, Idiosepius paradoxus, mating includes neither a pleasant courtship nor aggressive behavior. Males copulate freely with females. Pygmy squid males will dart toward a female, grasp hold of her, and attach a capsule (the spermatangia) contain sperm to the base of her arms. However, females will often remove the spermatangia. Females will stretch out their buccal mass (mouth and pharynx) to search for the spermatangia at the base of the arms. Once picking up these spermatangia with their beaks, females with either eat them or blowing them away from water from the funnel.

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From Sato et al. 2013

So when does a pygmy squid female choose to keep or discard spermatangia? In a recent study, Sata et al. found the elongation of the buccal mass of females post copulation was predicted by the length of the male partner and the duration of the copulation. Males who were longer than 8-9mm or lasted longer than 3 seconds faired poorer than their shorter, in every possible way, male competition. Why small males and quickies? Both of these may be a evolutionary result decrease risk from predators. Shorter pygmy squid males may stay hidden more easily amongst seagrass. Likewise, mating can make squid pairs more conspicuous to predators and quickies would be favored or long tromps.

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A female pygmy squid blowing spermatangia away by jetting water using her funnel. From Sato et al. 2013

And because the females does this all post coitus, the males are none the wiser.

Noriyosi Sato, Takashi Kasugai, & Hiroyuki Munehara (2013). Sperm transfer or spermatangia removal: postcopulatory
behaviour of picking up spermatangium by female
Japanese pygmy squid Marine Biology, 160, 553-561 : 10.1007/s00227-012-2112-5

Noriyosi Sato, Takashi Kasugai, & Hiroyuki Munehara (2013). Female Pygmy Squid Cryptically Favour Small Males and Fast Copulation as Observed by Removal of Spermatangia Evolutionary Biology : 10.1007/s11692-013-9261-4

Dr. M (1729 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, a National Science Foundation supported initiative. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web. His forthcoming book, Science of the South (, connects cultural icons of South such as pecan pie with the science behind them.

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