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Egg-laying & hatching

  Stages in reproduction include egg-tending & hatching, considered here, and COURTSHIP & COPULATION and PELAGIC DEVELOPMENT OF JUVENILES, considered in other sections. This account is divided into sections on OCTOPUSES and SQUIDS
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Research study 1

photograph of Octopus bimaculatus showing eyespotdrawings of developmental stages of Octopus bimaculatusA study on the reproductive biology of the 2-spotted octopus Octopus bimaculatus in Catalina Islands, California is uniquely carried out over a 6-yr period entirely with the use of SCUBA.  Matings occur May-July coincidental with increasing water histogram showing egg/clutch-laying success of Octopus bimaculatustemperatures (15-19oC).  Females lay their eggs in April-August and hatching is in June-September (50d to hatching at 19oC; see drawings above Right). Clutch sizes can reach 20,000 eggs

The females tend the eggs by cleaning and ventilating, and die soon after the eggs hatch.  Females that lay their eggs too early in the season, for example, from Jan-Mar, generally do not complete the layings (see histogram at Right)

The newly hatched octopuses spend several months in the plankton and then settle to the sea bottom. Interstices in kelp holdfasts Macrocystis pyrifera are attractive settling sites.  The juveniles are most abundant during summer, with a second peak in winter representing the late hatchlings.  The juveniles remain in the holdfasts until attaining about 5cm mantle length.  This occurs in late spring of the following year, at an age of about 8-10mo.  Adults are most abundant during late summer and autumn, but with drawing of hatchling Octopus bimaculatusconsiderable year-to-year variability.  Once adulthood is reached, an octopus' lifespan is approximately 8-10mo.  If the juvenile's several months in the plankton is included, the maximum life span isabout 2yr.  Ambrose 1988 Malacologia 29: 23. Photograph of O. bimaculatus courtesy Birch Aquarium, Scripps Institution of Oceanography, La Jolla, California.

NOTE  eggs of O. bimaculatus are 2-4mm in length, while those of the closely related O. bimaculoides are 10-12mm in length.  The hatchlings of O. bimaculoides immediately assume a benthic way of life, with no planktonic stage.  Forsythe & Hanlon 1988 Malacologia 29: 41.

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Research study 2

graph showing relationship between live mass and eggs laid in octopuses Octopus rubescensInformation on fecundity and embryonic development of octopuses Octopus rubescens in Monterey Bay, California is presented by a researcher at Moss Landing Marine Laboratories, California.  Mean numbers of eggs per brood range from 4,000-20,000 for females of 117-140g (see graph).  Times to hatch in the laboratory range from 50d at 18oC to 90d at 15oC.  Selected developmental stages of the 31 “distinct” ones described by the author are shown here along with their chromatophore patterns.  Hatchlings in laboratory culture are positively phototactic for just a few minutes.  Attempts to rear the hatchlings fail despite using many different combinations of rearing conditions and types of food.  Osborn 1995 MSc Thesis, 88pp, San Jose State University, California.

NOTE  blastulation alone comprises 10 of these "distinct" stages, and gastrulation 5



A few selected stages in embryonic development at 18oC. Sizes are not given by the author:

drawing of Stage 24 embryo of octopus Octopus rubescens
drawing of Stage 24 embryo of octopus Octopus rubescens
drawing of Stage 24 embryo of octopus Octopus rubescens
drawing of Stage 24 embryo of octopus Octopus rubescens
Day 28: arm definition & suckers are visible Day 32: orange chromatophores are visible Day 37: more chromatophores, including brown ones Day 50: hatchlings are positively phototactic for the first 15min of free-swimming life. This takes them from the bottom to the sea surface where they disseminate
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Research study 3

photograph of female Octopus rubescens tending eggs courtesy Roland Anderson and the Seattle Aquarium, WashingtonPresented here are photographs of developmental stages of a few west-coast cephalopods. Photographs on the immediate Right and far Right below courtesy of Roland Anderson and the Seattle Aquarium, Washington. First 3 photos below from Left to Right courtesy Shawn Robinson, Simon Fraser University, British Columbia.





Female Octopus rubescens tending
her eggs. The eggs are 3-4mm in length.

photograph of eggs of octopus Enteroctopus dolfleini courtesy Shawn Robinson, Simon Fraser University, British Columbia
Mixed fertilised and unfertilised eggs of Enteroctopus dofleini 1.5X
photograph of late-stage embryo of octopus Enteroctopus dolfleini courtesy Shawn Robinson, Simon Fraser University, British Columbia
Late-stage embryo of Enteroctopus dofleini 5X
photograph of newly hatched octopus Enteroctopus dolfleini courtesy Shawn Robinson, Simon Fraser University, British Columbia
Newly hatched octopus Enteroctopus dofleini 2X
photograph of egg sausages of a squid Loligo opalescens
Egg 'sausages' of squid Doryteuthis opalescens washed up on a B.C. beach 0.3X
photo composite of Rossia pacifica egg capsule and hatchling courtesy Roland Anderson and the Seattle Aquarium, Washington
Hatchling squid Rossia pacifica 1.5X
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Research study 4

graph showing gonadosomatic indices for female octopuses Enteroctopus dolfleini in Alaskagraph showing fecundity of octopuses Enteroctopus dolfleini in AlaskaResearchers from the Alaska Fisheries Science Center provide life-history statistics for giant octopuses Enteroctopus dolfleini collected from sites around Kokiak Island in the Gulf of Alaska. Both sexes mature at about the same live mass of 14kg (but with high variability) and egg-laying takes place from Jan-Mar. These maturity sizes are apparently larger than other values reported for the species. Mean fecundity, calculated as total number of eggs in the ovary, is 107,000 (again, with high variability; see graph on Left). Measurements of gonadosomatic indices in females show increasing values from spring to highest values in winter, with comparably increasing egg lengths over the same period (see graph on Right). Mating occurs predominately in spring/summer but, on the assumption that females are capable of storing sperm, the authors believe that mating may extend throughout the year. Conrath & Conners 2014 Fishery Bull 112 (4): 253.

NOTE calculated as the ratio of reproductive-tract mass to total live mass (presumably including reproductive tract) in 14kg live-mass females




A female squid encases her eggs by first extruding a sausage-shaped sheath through the siphon and holding it between her arms. She then pumps eggs into the case, closes the end in some way, and inserts it into the sand with a mucilaginous anchor, or attaches it to something firm on the sea bottom. As the embryos develop, the case absorbs seawater and becomes longer and thicker. The females dies shortly after producing the her case(s), and the eggs hatch within a few weeks without parental care to a pelagic juvenile stage known as a paralarva. During development the walls of the case weaken and degrade, allowing the juveniles to emerge.

photograph of a female squid Doryteuthis opalescens with egg case, courtesy Kevin Lee, Fullerton, CaliforniaNOTE this is commonly referred to by fisheries-orientated researchers as a capsule or egg capsule. This is unfortunate in that the egg capsule, by dint of about 1.5 centuries of previous use, is actually the membrane layers that surround the egg. Moreover, when a squid hatches, it does so from its egg capsule, not from the case. Another term, perhaps emergence, should be used for the young squid leaving its case. Paralarva is also a partial misnomer, as cephalopods do not have a free-living larval stage. There is nothing wrong in having a set of jargon terms specific to a subject, but not when it engenders confusion, as can be seen in some of the following studies

A female squid Doryteuthis opalescens holds the case in her arms while she
works on it. Each case contains between 50-300 eggs. It is not known how
many cases a female will produce during her single spawning period 1.5X
Photograph courtesy Kevin Lee, Fullerton, California diverKevin.

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Research study 1

drawing of squids copulating, with the male in an underneath positiondrawing of squids copulating in a head-to-head positionSquids  Doryteuthis (Loligo) opalescens in Monterey Bay, California undertake their most intense spawning in April-July.  A unique SCUBA-diving observation of spawning Loligo around La Jolla, California at 16m depth describes large masses of egg cases (also known as capsules), some covering areas up to 3-4m in diameter, with many actively swimming squids nearby.  The squids are about 15cm mantle length for males, and 14cm for females.  The author describes their appearance as “spent”, with flaccid bodies and shreds of loose epithelium, especially on the females.  Most of the egg cases are attached to other capsules, rather than to objects on the sea floor.  The juveniles hatch after about 7wk (14oC) at 4mm mantle length.  The author comments that the most common copulatory behaviour is with the male below as shown in the drawing on the Left, although another another type of head-to-head behaviour may sometimes be used (drawing on Right). McGowan 1954 Calif Fish Game 40: 47: for review of life cycle of D. opalescens see Hixon 1983 p. 95 In, Cephalopod life cycles Vol I (Boyle, ed.) Academic Press, London.

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Research study 2

A description of squids  Doryteuthis opalescens spawning on sandy bottom at 9m depth off Long Point, Santa Catalina Island, California goes as follows.  The male grasps the female from below and uses his left ventral arm, or hectocotylus, to transfer spermatophores from his siphon to the mantle cavity of the female.  The female later deposits eggs, encased in 10cm-long gelatinous capsules (cases), onto the sandy bottom.  Capsules are most commonly deposited around the periphery of egg masses left by other females.  The author notes the presence of many dead squids lying amongst and around the egg capsules. Hobson 1965 Underwater Nat 3: 20.

NOTE  the author does not actually see the transfer, but presumes that it must have occurred

Research study 3

photograph of mass of egg cases of squid Doryteuthis opalescens courtesy Kevin Lee, Fullerton, CaliforniaSquids Doryteuthis opalescens spawn commonly in Barkley Sound, British Columbia.  A typical mass, consisting of an average of 1,937 cases, each containing an average of 149 eggs, would therefore contain about 290,000 eggs.  The author estimates that 24,000 females may have been involved in a mass laying during a single night (31 May, 1982).  Shimek et al. 1984 Fish Bull 82: 445. Photographs courtesy Kevin Lee, Fullerton, California diverKevin.

NOTE  the authors’ terminology in this account is unclear.  Use of “egg capsule mass”, “capsule mass aggregation”, egg number “per solitary mass”, and “number of eggs per isolated mass” without definition is confusing. A better terminology, as used in the figure legend below, would be: a number of capsules, each containing a single egg, are contained within each case or sausage. A number of cases are laid by each female in large spawnings, leading to masses or egg mops


Mass laying of eggs by squid Doryteuthis opalescens in
southern California. The photograph shows numerous
cases containing egg capsules (inset photo) and a
single, dead squid, presumably female 0.2X

Research study 4

photograph of stubby squid Rossia pacifica courtesy Roland Anderson and the Seattle AquariumRossia pacifica can readily be cultured in the laboratory.  At seasonally varying seawater temperature in the northern Washington area, embryonic development takes 5-6mo. From hatching to senescence takes another 18-19mo, so the total life span is about 2yr.  Collections of Rossia in the Burrows Bay, Washington area reveal the presence of 2 distinct cohorts representing the 2yr of overlapping generations.  Hatching, which occurs in the lab from late Oct–Dec, appears to be synchronised with the appearance of the new moon.  The author suggests that the dark skies associated with declining daylight of late autumn and the new moon period may offer protection from predators.  Additionally, the prolonged hatching period may be a strategy to spread out the appearance of the offspring.  Summers 1985 Vie Milieu 35: 249. Photograph courtesy Roland Anderson and the Seattle Aquarium, Washington.

NOTE to see these data go to FEEDING & GROWTH: GROWTH

Stubby squid Rossia pacifica 1X

Research study 5

Eggs of stubby squids Rossia pacifica have been found in the Puget Sound region in the months of February, April, June, and November, with one individual being observed laying in November.  Eggs require 6-8mo to hatch.  The eggs are large, up to 1cm in diameter, and the resulting hatchlings are about 1cm in size.  Clutch sizes range from 50-75.  The volume of eggs deposited represents about half the female’s live mass, and she dies a couple of days after laying.  The eggs are usually deposited on underhangs of rocks, which perhaps keep them clean from “raining” sediments.  Unlike photograph of eggs of a stubby squid Rossia pacifica courtesy Roland Anderson and the Seattle Aquarium, Washingtonwith octopuses, there is no parental care of the eggs.  The authors note that previous to their observations there have been no reports of egg-laying/egg capsules for stubby squids in the field.  Anderson & Shimek 1994 Veliger 37: 117. Photographs courtesy Roland Anderson & Seattle Aquarium, photograph of copulating stubby squids Rossia pacifica courtesy Roland Anderson and the Seattle Aquarium, WashingtonWashington.

NOTE  in comparison, the eggs of Enteroctopus dofleini are about 6mm in diameter.  Pickford 1964 Bull Bingham Oceanog Coll 19: 1.

Eggs of a stubby squid R. pacifica

Copulating stubby squids R. pacifica.
The male is the smaller of the two 0.5X

Research study 6

An observation by researchers in California on a mass spawning of squids Doryteuthis opalescens in Monterey Bay  following a 1997 El Niño event provides the following statistics.  In an area of about 1000m2 there are 152 egg masses or “egg mops”.  Each egg mop contains an average of 259 cases, and each case contains an average of 164 eggs.  The commonest predator eating the eggs is the sea star Patiria miniata.Zeidberg et al. 2004 Bull Mar Sci 74 (1): 129.

NOTE  the terminology used in this paper has been modified to conform to that used in other Research Studies in this section

Research study 6.1

photograph of egg of Humboldt squid Dosicicus gigasA remarkable observation by researchers from institutions in California, Rhode Island, and Baja California is that eggs of Humboldt squids Dosidicus gigas are not deposited in the familar sausage-form of smaller, shallow-water species, but rather in a giant gelatinous, floating mass (see photograph on Left). Each egg is doubly protected by a chorion membrane and a jelly envelope (see photograph on Right). The single egg mass featured here was observed off the east coast of Baja California, and was 3m in diameter, about 3 cubic meters in volume, and contained an estimated 1.3 million eggs. The eggs within are homogenously distributed and over 99% fertilised. Although there is no obvious external barrier to maintain cohesiveness of the egg mass, any penetration as, for example, insertion of a collecting jar, immediately seals on withdrawal with no evident mark. Hatchlings from the mass appear healthy, swim about in laboratory dishes, and grow by 50% within the first 3d (at 20oC). Following this, and at a size of about 1.5mm mantle length, they begin to decrease in size as their yolk supply beomes exhausted. The mass is neutrally buoyant and floats at a level presumably deep enough to be clear of surface wave disturbance, but shallow enough that the eggs enjoy good conditions of temperature and oxygenation for growth. The authors note that their paper is the first to document field- and laboratory-deposition of eggs in this species. Staaf et al. 2008 J Mar Biol Ass UK 88 (4): 759.

photograph of large egg mass of a Humboldt squid Dosidicus gigasNOTE1 this estimate is consistent with direct counts of eggs in oviducts of large female D. gigas reported by other researchers; hence, an egg mass of this size could have come from a single female


NOTE3 the mass is thought by the authors to be created by coatings (chorion and envelope: involved in later fertilisation) added to the eggs during passage through the oviducal gland. The eggs then pass through the nidamental gland where concentrated jelly is added (this later expands to form the watery, gelatinous matrix of the floating egg mass), and exit via the gonopore and siphon to be fertilised within the buccal area by sperm released from the male’s spermatophore (called a spermatangium by these authors) that has been left there after copulation

Naturally spawned semi-transparent egg mass of Dosidicus gigas with
SCUBA-diver behind, at about 16m depth (the sea bottom is some 1800m below). Visible is the diver’s blue-water safety line. Evolution of a
floating egg mass would seem advantageous for a pelagic species

Research study 7

graph showing relationship of hatching percentage and culture temperature in squids Doryteuthis opalescensphotographs of symbiotic capitellid worm Capitella ovincola approaching and penetrating the egg-case sheath of a squid Doryteuthis opalescensAn investigation of temperature effects on hatching (actually, emergence of paralarvae from the egg case) of squids Doryteuthis opalescens at Hopkins Marine Station, Pacific Grove, California shows that optimal hatching (96%) occurs in the dark within the range 9-14oC (see graph).  Additionally, the authors find that a polychaete worm Capitella ovincola1, long thought to be commensal with the egg cases, actually feeds2 on the gelatinous matrix surrounding the egg capsules in the cases, but not on the eggs, embryos, or paralarvae.  In order to feed, the worms slice into the cases to gain entry, and several may form an intertwined clump within a case (see photographs).  Loss of matrix material caused by the worms, both in leakage via the slicings and by being consumed, and the sliced opening itself, appear to provide easier egress by the paralarvae from their egg cases. In fact, emergence percentage is slightly elevated for egg cases in the presence of the worm as compared with when it is absence (3% difference; note: the authors report 2 contradictory p values related to the statistical significance of these data).  For this reason and because the worms are provided nutrients and protection, the relationship is considered by the authors to be mutualistic3, rather than commensal or parasitic. The authors don’t consider predation as an option.  Zeidberg et al. 2011 Mar Ecol 32: 468.

NOTE1  this species and related capitellid species are known to occur in other species of squids, but none has ever been reported from other types of cephalopods.  The worms are commonly found in egg cases laid in the field, but not apparently in egg cases laid in the laboratory

NOTE2 this is determined through stable-isotope analysis, using changing ratios of 15N and 14N in purported prey and predator to indicate consumption

NOTE3 the authors actually use the term symbiotic for the relationship, which is more commonly used in Britain and Europe for what we in North America refer to as mutualistic

Research study 8

In an interesting application of sidescan-sonar methodology, a group of California researchers map the distribution of egg cases of squids Female squid Doryteuthis opalescens holding egg caseseries of images showing sidescan-sonar generated views of egg-mop clusters of squids Doryteuthis opalescens on the sand in Monterey BayDoryteuthis opalescens in the south part of Monterey Bay.  The method allows easy assessment of egg-mop densities over large areas with good resolution (see images).  The authors conclude that the method holds promise for determining site preferences for spawning squids and year-to-year egg-mop abundances for use in managing the fisheries.  Young et al. 2011 J Exp Mar Biol Ecol 407: 226. Photograph on Right courtesy Kevin Lee, Fullerton, California diverKevin.

NOTE  a spawning female will attach each case (or sausage) to something firm, like a rock in the sand, or to other egg cases.  When other females use the same attachment point, a flared-out “egg-mop” or mass is created.  Many such egg-mops may be clustered in areas providing good attachment points

Female Doryteuthis opalescens with egg case. The
egg capsules within the case are clearly visible 1X.


Research study 9

map of Carmel Bay, California showing distribution of squid egg cases Doryteuthis opalescens on different substrata and different depthsSimilar scanning methodologies are employed by another group of  fisheries scientists to survey spawning activity of squids Doryteuthis opalescens in areas around Monterey and the California Channel Islands.  The researchers report densities of cases (capsules) exceeding 1000 per m-2 in some areas, deposited at depths of 10-60m in central California and 20-90m in the Channel Islands.  Interestingly, 95% of the cases are found on sand.  Most favourable conditions for spawning, then, are sandy substrata, temperatures of 10-14oC, and depths of 20-70m.  Zeidberg et al. 2011 Mar Ecol 32: seen online only.

Research study 10

map showing historical and current distribution of Humboldt squids Dosidicus gigas along the west coast of the AmericasRecent northward range expansion by Humboldt squids Dosidicus gigas raises the question of temperature effects on their embryonic development.  This is investigated by scientists at Hopkins Marine Station, California who capture live gravid squids, remove eggs and sperm, arrange for in vitro fertilisation of the eggs, and culture the embryos over a range of temperatures from 5-30oC.  Results show that hatching occurs only between 15-25oC (maximal at 20oC) suggesting that this temperature range is optimal for early development.  The researchers then review past oceanographic data and discover that a large area of inshore California coastline has seasonably suitable temperatures for the squid’s early development.  It is possible, then, that spawning by D. gigas populations in this area may have facilitated the invasive spread of the species into more northern areas during the last decade.  Staaf et al. 2011 Mar Ecol Progr Ser 441: 165.

NOTE the process seems straightforward as written here, but in practise requires some deft technical innovation

NOTE temperature effects on post-hatching development are not mentioned by the researchers, and it may be that the techniques for culturing the hatchlings or paralarvae are not yet developed