page_title: Cephalopod size
section_title: Hatchlings
hierarchical_section_title: Cephalopod size / Early life stages / Hatchlings
caption_attribution_description: English: Egg string and embryos of Haliphron atlanticus, collected north of Cape Verde Islands (17°24′N 22°57′W﻿ / ﻿17.4°N 22.95°W). Eggs measure around 8&#160;mm in long axis. Identified by R. E. Young and Mike Vecchione "based on size of eggs and equal length of arms of embryos and their capture in a pelagic trawl at 300&#160;m depth over a bottom of about 3,000&#160;m". Held in collections of NMNH.
context_page_description: Cephalopods vary enormously in size. The smallest are only about 1 centimetre long and weigh less than 1 gram at maturity, while the largest—the giant and colossal squids—can exceed 10 metres in length and weigh close to half a tonne, making them the largest living invertebrates. Living species range in mass more than three-billion-fold, or across nine orders of magnitude, from the lightest hatchlings to the heaviest adults. Certain cephalopod species are also noted for having individual body parts of exceptional size. The giant and colossal squids, for example, have the largest known eyes among living animals.
  Cephalopods were at one time the largest of all organisms on Earth, and numerous species of comparable size to the largest present day squids are known from the fossil record, including enormous examples of ammonoids, belemnoids, nautiloids, orthoceratoids, teuthids, and vampyromorphids. In terms of mass, the largest of all known cephalopods were likely the giant shelled ammonoids and endocerid nautiloids, though perhaps still second to the largest living cephalopods when considering tissue mass alone.
  Giant cephalopods have fascinated humankind since time immemorial.
context_section_description: Hatchlings of Idiosepius thailandicus, possibly the smallest extant cephalopod species at maturity, have a mantle length of around 1 mm (0.039 in) (Nabhitabhata, 1998:32). The closely related Idiosepius pygmaeus weighs only 0.00033 g (1.2×10⁻⁵ oz) upon hatching and increases in weight to 0.175 g (0.0062 oz) as it reaches maturity in 50 days (Wood & O'Dor, 2000:93). Even smaller are the hatchlings of the commercially important Illex illecebrosus, with a mass of 0.00015 g (5.3×10⁻⁶ oz) (O'Dor et al., 1986:59; Wood & O'Dor, 2000:93). Hatchlings of the giant Pacific octopus (Enteroctopus dofleini)—one of the two largest octopus species—weigh 0.0253 g (0.00089 oz) on average (Cosgrove & McDaniel, 2009:88).
  At the other extreme are nautiluses, which upon hatching typically have a shell diameter of 25 mm (1 in) or more (depending on the species), the largest hatchling size among extant invertebrates (Grulke, 2014:105). Hatchlings of Nautilus belauensis, one of the larger species, are estimated to weigh on the order of 5.9 g (0.21 oz) and mature at around 1.2 kg (2.6 lb) after almost 4000 days, or around 11 years (Wood & O'Dor, 2000:93).
caption: Egg string and embryos of Haliphron atlanticus, collected north of the Cape Verde Islands. The eggs measure around 8 mm (0.31 in) across the long axis.
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