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Short communication

First feeding of Octopus vulgaris Cuvier, 1797 paralarvae using

Artemia: Effect of prey size, prey density and feeding frequency

J. Iglesias , L. Fuentes, J. Snchez, J.J. Otero, C. Moxica, M.J. Lago

Instituto Espaol de Oceanografa, Centro Oceanogrfico de Vigo, Apdo. 1552, 36200 Vigo, Spain

Received 23 June 2006; received in revised form 1 August 2006; accepted 1 August 2006

Abstract

Different assays related to the first feeding of Octopus vulgaris Cuvier, 1797 are compiled in this paper. They include: age at

initial feeding age, prey size selection and optimal density, attack timing after feeding, and effect of dose number on the number of

captures. Prey capture and ingestion processes were also analysed. Food supplied was cultured Artemia sp. Each assay lasted

15 min.

Although paralarvae already start to feed on the hatching day (day 0), it is during day 2 when a greater number of attacks is recorded

(81.7 14.7% paralarvae attack). They mainly prefer (significance level =0.05) large Artemia, 1.4 0.4 mm (77.0 5.6% of the total

attacks) than small Artemia, 0.80.1 mm (23.05.6%). There is also a slight predilection for the lowest Artemia concentration (33.3

12.6% paralarvae attack in a 0.1 Artemia ml1 density, opposite 16.77.6 and 18.37.6% in densities of 0.5 and 1 Artemia ml1

respectively). The greatest predatory activity is recorded during the first 5 min after food is supplied (72.225.5%). An increase in the

predatory activity was also observed when food was distributed in several doses instead of a single dose (75.0 10.0% and 46.7 17.6%

respectively). It was proved for the first time that paralarvae completely ingest their preys (including their exoskeletons), in this case

Artemia. Time needed for their total ingestion ranges between 4 and 10 min.

2006 Elsevier B.V. All rights reserved.

Keywords: Octopus vulgaris; Paralarvae; Artemia; First feeding; Ingestion process

1. Introduction

This work intends to approach the problem of Oc-topus vulgaris paralarval culture, and also to act as a link

between aquaculture and this species biological knowl-

edge, because different gaps still persist regarding their

first developmental stages (Roper et al., 1984).

Several studies have been focused on the octopus

paralarvae rearing. Itami et al. (1963) and Villanueva

(1995) achieved benthic paralarvae for the first time in

Japan and Europe respectively. Iglesias et al. (2002,

2004) and subsequently Carrasco et al. (2003, 2005)closed the octopus culture cycle and achieved adult

octopus from paralarvae cultured in intensive systems.

Diet utilized in all cases consisted ofArtemia and larval

stages of selected crustaceans (Palaemon serrifer, Maja

brachydactyla, and Pagurus prideaux). Nevertheless,

survival rates after the planktonic phase of paralarvae

were very low in general.

Furthermore, a number of diverse prey types and sizes

have been used, often under different feeding regimens

(concentrations, feeding times, and food treatments). As

Aquaculture 261 (2006) 817822

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Corresponding author. Tel.: +34 986 49 21 11; fax: +34 986 49 23

51.

E-mail address: [email protected] (J. Iglesias).

0044-8486/$ - see front matter 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.aquaculture.2006.08.002.
mailto:[email protected]://dx.doi.org/10.1016/j.aquaculture.2006.08.002http://dx.doi.org/10.1016/j.aquaculture.2006.08.002http://dx.doi.org/10.1016/j.aquaculture.2006.08.002mailto:[email protected]


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a result, no standardized methods or protocols exist at the

present for paralarvae rearing. It is globally accepted that

nutrition and feeding behaviour are the most important

factors for paralarval survival. Therefore, in this paper

we deal with items related to first feeding, such as prey

age, size and density, feeding timing and frequency, andcapturing and ingestion behaviour.

There are several previous works related to this

subject, such as Hernndez-Garca et al. (2000), that

concentrates on the evidence that O. vulgaris makes an

external digestion of crustaceans larvae used as a diet,

fact thoroughly verified both for juveniles and adults

(Nixon, 1984; Nixon and Mangold, 1996). Likewise,

Villanueva et al. (1996) presents a detailed description

of the natatory and food searching behaviour of the

planktonic phases of O. vulgaris. Besides, Villanueva

et al. (2002) also deals with the effect of food concen-tration on the proteolytic activity and on the growth of

O. vulgaris paralarvae.

2. Material and methods

The aim of this work was to determine highly re-

markable aspects of first feeding of octopus paralarvae:

age at which feeding starts, selected prey size and den-

sity, attack timing after food supply, effect of the number

of doses, and time to completely ingest preys. Prey

supplied as food was Artemia sp. cultured with Iso-

chrysis galbana Parke (Iglesias et al., 2005).Experiments were made in white plastic cylindrical

tanks (26 cm high and 25 cm in diameter) with a total

volume of 10 l containing 2.5 l of seawater. 20 para-

larvae were introduced in each of them. Water tem-

perature ranged between 18 and 20 C, salinity between

34 and 35, and light intensity in the tank surface was

300400 lx. In any case, paralarvae were starved in

100 l tanks, at a density of 5 paralarvae l1 and a

temperature of 1820 C, until the experiments began.

In the assays carried out to determine age at initial

feeding, 0-, 1-, 2- and 3 day old paralarvae were used.

These were fed on one single dose of 0.5 Artemia ml1

(1.50.0 mm of total length). Triplicates were estab-

lished for each age group. In the other experiments, 2-

day-old paralarvae were used and triplicates were

prepared for each treatment. The prey size selection ex-periment was made feeding paralarvae on a mixture of

small (0.80.1 mm total length) and large (1.40.4 mm

TL) Artemia with a ratio of 0.25 Artemia ml1 for each

size. Ingestion process was determined in paralarvae fed

on a dose of 0.5 Artemia ml1 (1.40.4 mm); contin-

uous observations under binocular magnifier were

carried out to estimate time invested in total ingestion.

Prey density selection was estimated using paralarvae

fed on three different densities of (1.40.1 mm TL)

Artemia (0.1, 0.5 and 1 Artemia ml1). The precise

moment in which attacks on Artemia (1.40.1 mm TL)

took place were calculated taking into account the rightmoment of the attack after the food supply.

Finally, the effect of the number of doses was studied

by supplying a single dose of 0.1 Artemia ml1 (1.6

0.2 mm TL) and the same quantity of Artemia divided

into three doses (minute 0, 5 and 10).

Each experiment lasted for 15 min and started when

food was added to the tank, in which paralarvae had been

previously placed. Though still water was maintained

during the assay, culture medium was gently shacked for

no more than 10 s at 0, 5 and 10 min in order to homo-

genize preys distribution.Each replicate was individually controlled by an

observer, in charge of constantly observing paralarvae

behaviour and score the number of attacks, defined as

the number of paralarvae that attack a prey and keep it in

their arms. For this purpose, paralarvae and prey were

together removed from the tank by a Pasteur pipette to

be observed by binocular magnifier, and the precise

capture time was recorded. Subsequently, neither para-

larvae nor preys were returned to the tank.

At the end of each experiment, in minute 15, every

captured prey was reviewed to describe its morphomet-

ric characteristics or to assess its ingestion degree. In theFig. 1. Average percentage of paralarvae that attack Artemia at eachage (0, 1, 2 and 3 days-old after hatching).

Fig. 2. Average percentage of attacks of 2-day-old paralarvae on Arte-

mia of two different sizes (small=0.80.1 mm; large=1.40.4 mm).

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case of the analysis of prey size selection, observation

was immediately carried out after the capture.

A statistical comparison among the different treat-

ments was carried out by one-way ANOVA (signifi-

cance level =0.05).

3. Results

3.1. Age influence on the number of attacks

Average percentages of prey attacks observed during

the first three days of life of octopus paralarvae are

shown in Fig. 1.

On day 0 hatching dayparalarvae present a scarce

capacity to attack their preys (only 13.35.8% para-

larvae attack). The number of attacks increases gradu-

ally, four-fold in day 1 (50.0 25.2% paralarvae attack),

and the greater number of prey captures is observed

(81.714.7%) in day 2. Nevertheless, if paralarvae are

kept starved one day more i.e. until day 3 a cleardecrease in the number of attacks is detected (47.8

24.4%).

An ANOVA among the number of attacks observed

in the three replicates corresponding to each age,

shows significant differences (pb0.05). Consequently,

future assays were carried out with 2-day-old

paralarvae.

3.2. Selected prey size

When 2-day-old paralarvae were supplied preys

having two different sizes, a clear tendency toward

those having a greater size was recorded (Fig. 2). Larger

Artemia (1.40.4 mm total length) were clearly preferred

(77.05.6%) to smaller Artemia (23.05.6%), showing

significant differences (pb0.05).

The continuous observation of the prey consumption

immediately after the capture, has allowed us to find out

for the first time that, when fed on Artemia, paralarvae

completely ingest it and they do not simply suck up its

internal content. The ingestion process of four para-larvae which completed it is shown in Table 1 (12 over

20 paralarvae attacked, and only the ingestion process of

4 of them could be entirely described).

In general, paralarvae hold their preys by their dorsal

area, and a suction, not only of their internal content but

also their complete exoskeleton takes place; this process

has a length of 4 to 10 min. In Fig. 3 Artemia appendices

(thoracopods) can be observed inside a paralarva di-

gestive tract.

Fig. 3. Stomach content of an O. vulgaris paralarva which has just

ingested an Artemia. Artemia thoracic appendices (thoracopods) canbe observed inside a paralarva digestive tract.

Table 1

Ingestion process of preys in O. vulgaris paralarvae

Half ingestion (min) Total ingestion (min)

Paralarva 1 1 min 59 s 4 min 3 s

Paralarva 2 No data recorded 5 min 20 s

Paralarva 3 2 min 54 s 8 min 54 sParalarva 4 4 min 28 s 10 min 25 s

Fig. 4. Average percentage of 2-day-old paralarvae that attackArtemia

at different densities (0.1, 0.5, and-1 Artemia ml1).

Fig. 5. Average percentage of attacks to Artemia distributed depending

on the observation time fraction (0 to 5, 5 to 10 or 10 to 15 min afterfeeding).

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3.3. Selected prey density

In Fig. 4 it can be observed that a greater number of

attacks (33.312.6%) exists at lower densities, 0.1 Ar-

temia ml

1

, than at 0.5 (16.7 7.6%) and 1Artemia ml

1

(18.37.6%), but these differences are not significant

( pN0.05).

3.4. Attack timing after feeding supply

In order to analyse the distribution in time of prey

catches, 2-day-old paralarvae attacks during 15 min,

divided into three consecutive intervals of 5 min starting

after food is provided, are represented in Fig. 5.

It is observed that most attacks (72.225.5%) take

place during the first 5 min, which approximately re-

presents one paralarva attack per minute, while duringthe subsequent time fractions values of 19.4 17.3% and

8.3 14.4% are consecutively recorded; significant

differences exist ( pb0.05) in the number of attacks

among the three fractions analysed.

3.5. Effect of the supply of a single food dose vs three

doses

In Fig. 6 it is observed that if a single food dose is

supplied, the average percentage of paralarvae that at-

tack in the three replicates is 46.7 17.6, while thispercentage considerably increases when three doses are

supplied (75.010.0%). Despite this fact, these differ-

ences were not significant ( pN0.05).

4. Discussion

During day 0 O. vulgarisparalarvae carry out very few

attacks. This may be due to the fact that they are not

physiologically ready to start their exogenous feeding.

The decrease in the number of captures observed at an age

of 3 days in starvation could be interpreted as reaching the

point of no return, after which paralarvae would have

considerably reduced their ability to catch, ingest and

digest their preys. In this work it is evidenced that at an

age of 2 days after hatching paralarvae show their greater

predatory activity. No previous works point out this

appraisal, but the authors obtained the same results using

wild zooplankton captured in the Ra de Vigo as a prey(unpublished data).

It also proved the convenience of using large size

preys (1.4 0.4 mm total length) in the first feeding of

octopus paralarvae. Iglesias et al. (2004); Moxica et al.

(2002) and Hamazaki et al. (1991) also used large size

Artemia specimens; Okumura et al. (2005) pointed out

that using large Artemia strains improves both growth

and survival in intensive rearing of octopus paralarvae.

Even Villanueva et al. (2002) and Carrasco et al. (2003),

who used nauplii for their experiments, indicate that

paralarvae subsequently need a prey having a greatersize; specifically, Villanueva et al. (2002) concludes that

enriched Artemia nauplii seem to be useful only as an

initial diet until a doubling in hatchling weight is

achieved.

In the case of 2-day-old paralarvae, it has been ob-

served that the number of attacks is greater at a prey

density of 0.1 Artemia ml1 than at higher densities (0.5

and 1.0 Artemia ml1), a result different to what could

be expected. An explanation to this fact could be that at

lower densities they can concentrate their attention

better and launch their attacks more effectively. Never-

theless, very different densities have been used to date.For example, Iglesias et al. (2004) used adult Artemia

(14 mm) at 0.050.1 ind ml1 and crustacean zoeae as

a complement; the concentration used by Moxica et al.

(2002) was 0.1 Artemia ml1. In other experiments

higher densities have been used: Villanueva et al. (2002)

worked with densities of 0.2, 2, 4 and 10 nauplii ml1

and recorded the best growth at the highest densities;

Carrasco et al. (2005) used densities of 0.20.8 Artemia

ml1 and Okumura et al. (2005) 2.0 Artemia ml1. As

there is not a general consensus on the optimum prey

density for octopus larval culture (that in any case isrelated to paralarvae density), we suggest that this

parameter, also related to growth and survival, should be

specially considered in future investigations.

The fact that during the first 5 min after food supply

paralarvae are most active, suggests that paralarvae

attacks and captures are stimulated by the first visual

contact with preys. This leads us to think that in the

larval culture of O. vulgaris it is advisable to distribute

the food supply in many doses along the day, instead of

one or two big doses. In fact, it is clearly observed that

immediately after the food dose is supplied, most

paralarvae catch their preys. Nevertheless, after a few

Fig. 6. Average percentage of attacks depending on the fact that food is

supplied in a single dose during the 15 min of the experiment, or in 3

successive doses at 0, 5 and 10 min after food supplies.



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minutes they scarcely show preys in their arms and the

number of attacks considerably decreases.

It has been observed that paralarvae make an external

digestion, at least of decapods larvae, extracting the

zoeae edible content and leaving the exoskeletons

completely empty (Hernndez-Garca et al., 2000). Ac-cording to them, paralarvae administer paralysing agents

on their preys (cephalotoxin), and digestive enzymes

break the muscle joints to make the extraction of the

edible content of exoskeletons easier. However, the

present paper has proved that, when paralarvae are fed on

Artemia, the prey is completely ingested in less than

10 min; therefore it could be possible that, besides the

external digestion, an internal digestion of the Artemia

takes place. The presence of Artemia gills and pieces of

appendices in the digestive systems of octopus paralarvae

has also been mentioned by other researchers (Roo,personal communication). The fact that adult Artemia

shows a thinner exoskeleton (1 m) than other crustacean

zoeae could increase its probability to be ingested.

5. Conclusions and recommendations

O. vulgaris paralarvae already start to feed on the

hatching day, although the number of attacks is very low.

They reach their maximum predatory activity 2 days after

hatching. Therefore, special attention should be paid to

prey size and density during the second day of life.

They preferably select larger Artemia (1.40.4 mmtotal length), instead of small Artemia (0.8 0.1 mm).

Therefore, when considering the establishing of an inten-

sive octopus paralarvae culture it is advisable to use alive

preys having a large size (total length greater than 1 mm).

Prey density producing the greater number of attacks

and captures was 0.1 Artemia ml1, in comparison to

greater densities of 0.5 and 1.0 Artemia ml1. Greater

densities have not produced a greater number of attacks.

Therefore, in order to reduce time and economical costs,

it is advisable to fit the prey quantity to the effective

consumption of paralarvae.During the first 5 min after food supply the greater

activity of attacks and captures in paralarvae is ob-

served. This agrees with the fact that distributing food

into three doses causes a greater number of attacks on

the preys in comparison to when a single dose is sup-

plied. Consequently, in octopus larval culture a supply

of alive food distributed in several doses throughout the

day is recommended instead of one or two daily doses.

Contrary to what is generally accepted, octopus

paralarvae completely ingest all their preys (adult Ar-

temia, in this case), process that takes from 4 to 10 min

to complete.

Acknowledgements

This study was funded by the projects PETRI: 1995-

0765-OP and INIA: ACU02-003. We would like to

thank the staff of the aquaculture facilities of the

Instituto Espaol de Oceanografa in Vigo for theircooperation in the experiments carried out.

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