Research Study 1

Fig. 2.  A small Octopus sp. with hectocotylus visible. This specimen has been preserved for class study 

Fig. 1.  Octopuses copulating

Courtesy Pearse et al. 1987 Living invertebrates Blackwell Sci. Publ., Palo Alto, California

Courtship has not been described in detail for all west-coast species, but some field and aquarium descriptions of mating are available for Enteroctopus dofleini.  Courtship and mating may be done from a distance, or with the male “mounted” on the female, either on top or on the side (Fig. 1).  Some accounts describe the male being positioned outside a den, with a presumed female being inside. Copulation is preceded and often accompanied by colour and skin-textural changes, especially in the male. Rather than just being a mechanism for spermatophore transfer, there is some thought that the male may use the spoon-shaped tip of its hectocotylus (Fig. 2) to clean out residual sperm or spermatophores deposited from previous mating(s) from the female’s oviducal openings in a strategy of sperm competition. 

Research Study 2

Fig. 1.  Fighting or courting? is there a difference?!

A description of an unusual “aggressive” encounter between two adult octopuses Enteroctopus dofleini in Puget Sound, Washington is acknowledged by the authors as possibly being courtship behaviour (Fig. 1).  In this instance the interaction lasted about 5min and included reciprocal "attacks" with interlocking arms and alternating colour changes: mottled reddish-brown for the attacker and blanching for the one "attacked". The authors note that the behaviour they witnessed is somewhat different than that reported for usual reproductive behaviour in octopods. Sexes of the "protagonists" could not be determined.

Research Study 3

Fig. 1.  Squid egg mass stranded at low tide.  The mass comprises several cases each containing many eggs, likely laid by several females

An unusual behaviour in squids Doryteuthis opalescens involves the guarding of egg masses (Fig. 1) by males. The observations were made on squids caught at Santa Catalina Island and San Diego, California and studied on shipboard, or on squids caught commercially and studied in the laboratory.  After an egg case is attached to the aquarium tank a male may take up guarding position over it, directing postural and colour changes to challenging males. Most often the challenging male retreats but, if not, the two males may square off and lunge back and forth, sometimes with damage being inflicted. The “resident” or dominant individual usually wins these interactions. If not, the challenging individual becomes dominant and takes up position over the egg mass. Interestingly, females are allowed to approach, but not males. It is not known if such behaviour occurs in the field. 

NOTE from a subjective viewpoint, the behaviour seems to be one of guarding. However, from an objective viewpoint, there may be other interpretations.  For example, is it possible that the males, through reception of pheromones from the eggs, may be perceiving the egg mass to be signifying a female's presence? 

NOTE  the case, incorrectly termed a capsule by the author is 8 x 1.2cm in size, and contains 180 - 300 encapsulate eggs

Research Study 4

Fig. 2.  Eggs of octopus Enteroctopus dofleini. These particular eggs are unfertilised as indicated by the empty contents

Courtesy Shawn Robinson, Simon Fraser University, Burnaby

Fig. 1.  Enteroctopus dolfleini ventilating

Courtesy Shawn Robinson, Simon Fraser University, Burnaby

During mating a male Enteroctopus dofleini (Fig. 1) uses his hectocotylus to transfer two spermatophores from his vas deferens into the genital or oviducal openings of a receptive female. The spermatophores are quite long and, following copulation, the empty ends may hang free of the female’s mantle cavity for a time.  About 40d after copulation the female attaches strings of fertilised eggs (18,000 – 70,000 eggs in total, each egg 6mm diameter) onto the undersides of rocks in crevices at 10 - 30m depth (Fig. 2). The female guards and cares for the eggs during the approximately 160d developmental period. The eggs hatch directly to juveniles that spend 1 - 2mo floating and feeding in the plankton before settling to the sea bottom. The male parent dies a few weeks after mating, while the female parent dies a few months after mating.  Both sexes of Enteroctopus mature early, and are thought to live for about 5yr, or until first mating.

Research Study 5

Fig. 1.  Reproductive system of a male Enteroctopus dolfleini

Reproductive maturation in a male Enteroctopus dofleini culminates in the formation and storage of spermatophores, which are long rope-like structures containing sperm. Up to 10 mature spermatophores may be present in a special storage sac known as the spermatophoric sac (Neeham's Sac) and two are normally used during a copulation. The sperm are manufactured in the testes (Fig. 1) and move through several regions of the vas deferens where they are coiled into a rope, and where various gels and membranes are added. The spermatophore eventually enters the opening to the prostate and, like a train on a blind-ending track, it has to back out after receiving other modifications.  It then moves into the spermatophoric sac.  From there the spermatophores, usually in pairs, are moved into the diverticulum and thence to the penis.  A single spermatophore in Enteroctopus is 1m in length, contains a coiled sperm rope over about half the length, and a complicated ejaculatory apparatus in the other half. The sperm rope contains about 10⁸ - 10¹⁰ spermatozoa.  If unraveled the rope would be about 4m long. Multiple copulations are the norm for a male Enteroctopus but, with only about 10 spermatophores in total, its reproductive activity is limited. 

NOTE lit. “sperm carry” G.  Spermatophores in E. dofleini are the longest described for any cephalopod species

NOTE John Needham (1713 - 1781) was an English naturalish and catholic priest, with interest in squid anatomy and other aspects of biology.  He is known best for his theory of spontaneous generation, that fostered much criticism and near ridicule amongst fellow scientists and educators

Research Study 6

Fig. 1.  Spermatophore of Enteroctopus dolfleini

Fig. 2.  View of spermatophore of Enteroctopus dolfleini with sperm concentrated in the now swollen distal end

After a short courtship, the male Enteroctopus dolfleini grabs the thin or distal end of a spermatophore from its penis using the groove in its hectocotylus arm and thrusts it into the orifice of one of the female’s oviducts. This initiates a complex series of events within the spermatophore that cause the sperm rope to be pushed into the thin or distal end, which swells to accommodate the incoming load of sperm and leads to evagination of the ejaculatory apparatus (Fig. 1). This action locks the sperm-filled swelling in place within the oviduct and prevents it from dropping out of the female. The sperm rope is moved along by pressure from seawater diffusing into the proximal end of the spermatophore and from elastic contraction of the sperm rope itself. The movement takes about an hour. These actions haul the entire mass of tightly encapsulated spermatozoa over a distance of a meter from the proximal to distal end of the spermatophore. The sperm are now positioned in a swollen bladder or reservoir located at what was previously the thin or distal end of the spermatophore (Fig. 2). The next step, evagination of the ejaculatory apparatus, occurs suddenly and produces a crink in the tube that locks it in place in the oviduct. The locking-in may additionally ensure that spermatozoa are not lost in “back-flow” from the oviduct. The swollen end of the spermatophore now bursts and the sperm are moved into the female’s sperm receptacle for later use. The process is repeated with a second spermatophore. About 2 - 3h after the arm is first inserted and after repeated pokings, the female has two empty spermatophores hanging from its oviducal orifices. 

NOTE a spermatophore similar in morphology to this is described for Octopus bimaculoides; in this case, a torpedo-shaped tube containing sperm at one end and an ejaculatory apparatus at the other. The author of the work on O. bimaculoides appears not to have witnessed ejaculation (Peterson,1959); see also Longo & Anderson (1970) for details of spermatophores of O. bimaculatus

Research Study 7

Fig. 1.  Alaskan Enteroctopus dolfleini with double hectocotylus arms (4th on each side)

As if one weren’t enough, a giant Pacific octopus Enteroctopus dolfleini is discovered off the coast of Unalaska Island in the Aleutian archipelago that bears not one, but two, hectocotylus arms.  This unusual condition has been seen in other octopus species, but has always involved the 3rd pair of arms.  In the present case, unique for E. dolfleini and for octopuses in general, it involves a double hectocotylisation of the 4th arms (Fig. 1). The University of Alaska Fairbanks researchers who found this anomalous individual report no additional unusual features, reproductive or other. 

NOTE the spermatophore-transferring arm in octopuses is normally the 3rd right arm, while in squids it is the 4th left arm

Research Study 8

Fig. 1.  Octopus bimaculoides

Courtesy Roger Hanlon, Marine Biological Laboratory, Massachusetts

Research at the University of Texas Marine Science Institute, Port Aransas on octopuses Octopus bimaculoides (Fig. 1) collected in southern California finds that male competition for mates depends upon female maturity, but not in the way you might think. In this case, male-male aggression is significantly greater in the presence of immature females than mature ones. The significance of the behaviour is not immediately clear, as immature females by definition are not ready to mate. However, as both types of females resist mating advances of the males to a similar extent, it may be that greater male-male aggression leads to the dominant male being able to spend generally more time in contact with females. The authors conclude, not surprisingly, that males are able to assess the reproductive status of females. 

NOTE greater aggression involves early and more frequent attacks between the males, and longer fights. The authors do not define what constitutes a “fight”

NOTE such resistance, described by the authors, takes the form of grappling by the female before or after making sudden moves in an "apparent effort to dislodge the male's hectocotylus from her mantle cavity".  Does this make sense, do you think?

Research Study 9

Fig. 1.  An octopus is shown splayed-out with arm designations.  The R3 arm tip, or hectocotylus, is labelled

Fig. 2.  So-called kernal-density estimations of arm-tip locations measured as distances from eye to tip for male and female Octopus rubescens on each respective side of the body.  Red clusters represent R3 arm tips, while black clusters represent the other 7 arm-tips

As a kind of oddity observation, researchers at Friday Harbor Laboratories, Washington discover that male red octopuses Octopus rubescens hold their third Right arms (R3) closer to their bodies than do females.  This is presumably to protect this particular arm, for its tip, the hectocotylus¹, is specially modified to transfer sperm packets into the mantle cavity and oviduct of reproductively receptive females (Fig. 1).  Other studies show the R3 arm of an octopus is least likely to be injured.  The observation itself is sort of 'ho hum...is that so?', but it is the way in which the researchers determine the behaviour that is the thing.  Just think of the almost impossible task of monitoring arm positions in a curling tangle of arms while an octopus is moving around.  The researchers do it using computer modelling that automatically identifies eye, mantle, and arm-tip locations of octopuses crawling across the middle of an aquarium tank.  The locations are initially identified and keyed in to the computer from over 2000 images by an experimenter.  Data used in analyses were eye-to-arm tip distances from 11h of video data, involving nearly 400,000 video frames.  Results show that males hold their R3 arms about 30% closer to their bodies than do females, and significantly closer than the other posterior arms (Fig. 2).  To anticipate a question about the R3 arm in males possibly being shorter than other arm lengths, the authors confirm that the R3 arm in males does not differ significantly in length from the other posterior arms.  Other notable results are that both sexes extend their anterior L1 and R1 arms significantly farther from their bodies than the other arms, and that arm R3 suffers less injury in field animals than the other arms.  The study is marvelous, not only for the results, but for the "can-do" approach of the researchers to a gnarly problem, and they are to be congratulated.

NOTE  the word originated from a mid-1800's observation of a naturally detached mating arm of a male argonauta (paper nautilus) that was found in a female and misidentified as a parasitic worm (genus Hectocotylus).  The name stuck for many decades.  Nowadays, the word is generally used to refer to the heocotylus arm of a male cephalopod

NOTE  does the close-in position of the R3 arm in males actually reduce injury?  Reference to a Research Study in OCTOPUSES & RELATIVES>PREDATORS>RS1 confirms that R3 arm in Octopus rubescens is injured less than any of the other 7 arms