Octopus bimaculatus OCTMAC-041699-BATKEL-001

This entry was posted on Friday, April 16th, 1999 and is filed under Octopuses, Spawning Reports.

The Breeder’s Registry©Information contained in this report is taken from submitted observations from aquarist unless noted otherwise (see comments). Information may be reproduced providing the Breeder’s Registry is cited.

Breeder ID: OCTMAC-041699-BATKEL-001

Date: 4/16/99

Identification: Octopus bimaculatus

Geographic origin: Eastern Pacific

Taxonomy: (after I.C.Z.N.)

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Order: Octopoda

Family: Octopodidae

Subfamily: Octopodinae

Genus: Octopus

Species: bimaculatus

Description: One of two sympatric species of two-spotted octopus (other species O. bimaculoides). O. bimaculatus generally occurs subtidally. Lay smaller eggs in comparison to O. bimaculoides and reach size in excess of 2 – 3 kilograms.

Length of time in captivity (year): 6 months prior to spawning

Size (mm): Female, ~ 8 cm mantle length at time of arrival, ~ 13 cm at spawning.

Physical differences: Unlike most octopus species, males do not possess modified tenrtacles, but rather possess obviously enlarged suckers on the 2,3 and 6,7 arms (Morris, Abbot & Haderlie, Intertidal Invertebrates of California, 1980). In our experience, this is only noticeable in mature animals.

Adult diet: Frozen squid, shrimp and scallops; but primarily live crabs (grapsids, small cancrids or anomuran shore crabs, in particular Petrolisthes cinctipes when available. Fed a minimum of 3x per week.

Pre-spawning activity: None observed. Female was isolated from time of arrival and must have been inseminated prior to collection 6 months earlier. Gertilization was therefore the result of longterm sperm storage.

Time spawning began: Overnight

Area spawning occurred: Bottom corner of aquarium on glass in depression excavated by female.

Frequency of spawning: Only once, animal died several months following the incubation and hatching of young. Surprisingly, the mother began to accept crabs again after the eggs hatched. Unlike most octopus we have seen incubate eggs, she did not exhibit typical deterioration or arm-eating behavior after the end of incubation. She did, however, become soft and deteriorated rapidly prior to her death.

Egg description: Many stalked eggs attached to a central stalk, numerous “strings” of eggs.

Approximate quantity: 300+

Size: ~ 10 – 15 mm long by 3 – 4 mm in diameter.

Egg changes / development: Eggs laid 6/23/98. We felt the eggs were likely nonviable due to the prolonged isolation of the female until eyespots noticed on developing young 10/6/98. Motile juveniles with yolk sac begin moving within 2 weeks, developing yopung pulse and flash chromatophores periodically when observed. First hatching 11/12/98. 50% hatched by 11/14/98. Last hatching 12/5/98.

Transfer / removal method: Not moved until time of first hatching. Female was removed from tank, egg strings removed from tank wall by razor blade and transferred to one gallon jar with adult. Both placed (with jar) into rearing tank without any tankmates,

Incubation period: 4.5 to 5.5 months (duration from first hatching to last hatching) at 12\F0C. Most likely considerably shorter incubation at higher temperatures.

Time hatching occurred: Primarily at night, but some during day, especially when manipulated by mother. Mother manipulated eggs throughout incubation, but when juveniles began to hatch she would direct her exhalent siphon towards the hatchling and “jet” them out of the jar where the eggs were being incubated. After being ejected from the incubation jar, juveniles would swim randomly for a while, but quickly locate the bottom and crawl down into the crushed coral gravel. Pea-sized crushed coral appeared to the ideal grain size for the juveniles to crawl into and hide. Also provided various larger rocks, shells and pieces of PVC pipe cut into short 2.5 – 5 cm (1 – 2″) sections in their aquarium.

Massive hatching occurred due to disturbance at time of relocation (many with yolk sacs) but most died shortly thereafter. No hatched larvae with yolk sacs were observed to complete resorption and continue development.

Larvae attracted to light? No, prefer dim lighting and hid shortly after lights were turned on.

Newly hatched appearance: Small versions of parent. Young fully developed and capable of both inking and color change displays (pulsing chromatophores). Non-aggressive, and aggregative; young accumulate in areas of high food concentration without apparent aggression immediately after hatching.

Size at hatching: ~ 10 – 17 mm

Yolk sac present? Rarely, and those with yolk sacs usually died shortly after hatching.

First food offered: Brine shrimp (Artemia) both nauplii and adults enriched with Selcon®, Encapsulon®, Liquifry Marine®, RotiRich®, and VitaChem®. During first week we introduced copepod and amphipod cultures to tank. Daily feedings with Artemia. Juveniles actively hunt and capture brine shrimp, but after 2 weeks stop paying attention to nauplii, so feeding was stopped. Juvenile octopus aggregate at overflow where adult brine shrimp become trapped in filter mesh making for easy capture. Growth very slow.

Second food offered: Microgastropods following the third week after hatching (Lacuna and Littorina spp. averaging 3 – 5 mm shell diameter). Juvenile octopus recognized snails as choice prey immediately upon first introduction to aquarium. Many dropped the Artemia upon which they were feeding and moved across the aquarium to capture snails. Fed once per week, as many snails as available were introduced into the aquarium. Juveniles would ignore all other food and horde snails (often wrapping one in each arm and using one arm to feed) until all were consumed, at which point other foods would be taken again.

As the animals grew and learned to hand feed, alternative foods were offered: frozen mysids, squid,shrimp, smelt and scallops; as well as live shore crabs, ghost shrimp, guppies, snails, brine shrimp and amphipods. Live snails, ghost shrimp and shore crabs seemed to be the preferred foods. Growth and survival was noticeably higher on these food items than alternatives. Guppies, smelt and commercial shrimp were obviously the least favorite foods and were often left only partially consumed or completely ignored.

Survival: First month, only 5 dead juveniles found, real count not possible because young are nocturnal and highly cryptic during the day. Emergence of hundreds of babies at night precludes accurate counts.

After second month, joung become more aggressive, often fighting to horde snails when introduced. Cannibalism becomes quite prominent and numbers definitely decrease. Babies ink regularly during fights over hiding spots and/or food ond in response to disturbances. (Carbon filters added to maintain high water quality)

Longterm survival: 66 babies eventually isolated into ~15 cm x ~15 cm x ~11 cm (6″ x 6″ x 4.5″) flow-through containers (3 per) in 1.5 meter (5 feet) flumes. 50 survived 3 – 4 months until shipped to new homes. Other invertebrates were housed in the system and fed hatched brine nauplii and provided with commercial supplements, but juvenile octopus were hand fed as previoulsy described. Juveniles left alone in rearing tank grow at more than double the rate of the isolated individuals, but cannibalism reduces the hundreds remaing juveniles to 6 within the same time period (apparently siblings are the best food of all possible alternatives we offered). Due to a chiller failure, the aquarium warmed to room temperature, but all 6 appear healthy and continue to grow even more quickly. Within 3 – 4 months, animals are roughly 5 – 6 times the size of the isolated siblings. No apparent problems with being raised at room temperature.

Spawning tank size (liter):375 liters including sum (100 gallons). 140 cm L x 60 cm W x 30 cm H ( 55″ x 24″ x 12″)

Sides of tank covered? One side; sky blue.

Lighting & photo-period: None, ambient room fluorescents <12 hours per day when room occupied.

Filtration: Surface skimming from tank into sump where water is drawn through a deep carbonmate gravel bed ( composed of crushed coral, oyster shell and carbonate sand) before being pumped back into main aquarium (~3700 gph / 1000 gph). Natural seawater. 5% change per week.

Additives and dosages: VitaChem® / VitaBoost® irregular dosing.

Water temperature: 12 – 13 \F0C, fluctuation < 1\F0

Specific gravity: 32 – 35 ppt (measured with lab grade refractometer)

pH: unknown

Nitrate: unknown

Rearing tank size (liter): ~190 liters (50 gallon) including sump ~77 cm L x ~53 cm W x ~32 cm H (30.5″ x 21″ x 12.5″)

Sides of tank covered? No

Lighting & photo-period: Same as for rearing tank

Filtration: Same as for rearing tank

Additives and dosages: Same as for rearing tank

Water temperature: 13 – 14 \F0C fluctuation >1\F0C. When chiller failed temperature increased to 20 – 24\F0C with ambient room temperature fluctuations.

Water parameters Same as for rearing tank

Word origin: Octopus is from the Latin root oct, -i, -o, meaning eight (8) and -pus from the Greek root meaning foot. The genus bimaculatus is from the Latin roots bi meaning two; and maculat meaning spot or spotted.

Vernacular name: Two-spotted octopus, California two-spotted octopus

About this report: Information contained in this report is taken from submitted observations. Taxonomy, Synonomy, Original description , Word origin and Suggested reading are provided by member(s) of The Breeder’s Registry staff. Information is presented under the belief that it is accurate. If you have information in addition to, or contrary to that presented you are encouraged to contact the Breeder’s Registry. Permission is granted for “one-time” personal use. Reproduction as distributed or accessible media is prohibited without prior written permission. All rights reserved. 1999

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