ON THE EGGS, REARING, HABITS OF THE FRY, AND GROWTH OF SOME CEPHALOPODA

SANG CHOE Biology Division, Atomic Energy Research Institute, Seoul, Republic of Korea

ABSTRACT Eggs of Sepia esculenta, S. subaculeata, Sepiella maindroni, Sepioteuthis lessoniana, and Euprymna berryi were hatched in concrete cisterns. The fry were fed live and dead invertebrates and fishes and were raised to near-adult sizes. Live mysids appeared to be a favored food. Details of the culture methods are given and observations noted on behavior and growth of each species.

INTRODUCTION There is a diversity of literature on the Cephalopoda, the most highly evolved of the invertebrates. Major works of importance to this paper include those by Naef (1923, 1928), Robson (1929, 1932), Sasaki (1929), and Voss (1956). There are about 650 known species of Cephalo- poda, but few of them have been studied as to life history or ecology. Knowledge of the life history of the various species would be of great value to the fields of taxonomy, phylogeny, and evolutionary theory. Many species of Cephalopoda are among the most desired and costly food items in the Orient, although they are seldom used for food in the West. These species are of great interest from a commercial, as well as purely biological, viewpoint. Four of the species discussed here, Sepia esculenta, S. subaculeata, Sepiella maindroni, and Sepioteuthis lessoniana, are as important as the octopus among Japanese fisheries products. For this reason, the author has engaged in experiments on the rearing of these four species and the smaller Euprymna berryi. It should be emphasized here that production of fry in large quantities is as important an aspect as control of reproduction and perfection of rearing techniques. All of the above mentioned species can be reared satisfactorily, under favorable conditions and with the proper food supply, and can be supplied in large quantities as fry. Growth experiments with these fry have given extremely favorable results, indicating a strong probability of success on an industrial scale. Reported in this paper are the spawning season, the form of the eggs, resistance of the egg and hatched fry to low salinity, the method of rearing, the characteristic behavior of fry, and growth. I am grateful to Dr. Y. Ohshima, University of Tokyo, and Dr. N. Nakamura, Director of Japan Freshwater Fisheries Research Laboratory for their manifold help throughout the work. I also express special thanks 1966) Choe: Rearing Cephalopods 331

22 -u ~20 GI 5 18 -o ; 16 D. ~ 14

-•. 12 / ~ ~ ~ 10 ______0/~---

March April May June July Spawning season FlGURE 1. The relation between the spawning season and water temperature. The water temperature represents a mean for the period from 1953 to 1957, at 10m depth in the main spawning ground of Atsumi, Aichi Prefecture. S.e., Sepia esculenta; S.s., S. subaculeata; S.m., Sepiella maindroni; E.b., Euprymna berryi; S.I., Sepioteuthis lessoniana. to Dr. G. L. Voss and Mr. E. McSweeney, Institute of Marine Science, University of Miami, for reading the manuscript and offering construc- tive help. MATERIAL AND METHODS Eggs used for the Sepia esculenta, S. subaculeata, and Sepiella maindroni experiments were those spawned on the egg-collectors made of bundles of azalea twigs, which had been sunk on the bottom on the spawning ground. In the case of Sepioteuthis lessoniana and Euprymna berryi, eggs spawned on the spawning ground were collected and used. Newly hatched fry were reared and cared for in two concrete cisterns of 167 cm X 167 cm x 50 cm and 335 cm X 335 cm X 90 cm, with flowing water. All the fry were fed primarily with the mysid Neomysis japonica Nakazawa until 20 to 40 days after hatching. Later, as they grew, they were given live shrimp (Palaemon nipponensis de Haan and Leander serrifer Stimpson), live, young, small fishes (primarily gobies) and, as a dead prey, anchovies. SPAWNING SEASON There are reports on the spawning season of Sepia esculenta by Yamamoto (1942a), Yasuda (1951), Koito et al. (1956), and Tomiyama 332 Bulletin of Marine Science [16(2)

FIGURE 2. The eggs of Sepia esculenta.

(1957); of Sepiella maindroni, by Yamamoto (1942b), and Koito et al. (1956); of Sepioteuthis lessoniana, by Choe & Ohshima (1961); of Euprymna berryi, by Maekawa (1961). The relation between the spawning season and the water temperature, observed for these species at Atsumi Bay, Aichi Prefecture, is shown in Figure 1. They move into the bay in spring for spawning, and the spawning lasts till the early summer. Habitually, Sepia esculenta, S. subaculeata, and Sepiella maindroni spawn on twig-like bodies on the muddy or sandy sea bed at an average depth of 10m. Slender twigs of trees or bamboo, stationary netting, annelid tubes, or Zostera marina (eel grass) make good material for the eggs to cling to. Sepioteuthis lessoniana, on the other hand, spawns its eggs in a lump on pebbles, broken pieces of shell, Chorda filum, etc., on the pebbly sea bed at a depth of 2 to 10m, while Euprymna berryi usually spawns on the stems of Zostera marina. The water temperature at spawning is 100-200e for Sepioteuthis lessoniana, and 17°-21 °e for Euprymna berryi.

EGGS Sepia esculenta.-Freshly spawned eggs are enclosed in a milky-white, 1966] Choe: Rearing Cephalopods 333

FIGURE 3. The eggs of Sepia suhaculeata. soft, gelatinous substance. The surface of the egg capsule is coarse, and on it can be seen four faintly protuberant lines which converge towards the tip. On either side of the protuberant lines traces of suckers are recognizable. The major axis is 16-21 mm long, and the minor axis 12-14 mm long (Yamamoto, 1942a). Eggs are spawned separately on the object chosen. In many cases, the surface of the egg capsule becomes darkly discolored with adhering sediment particles within two or three days after spawning (Fig. 2). Sepia subaculeata.-The eggs are enclosed in a milky-white, soft gelatinous substance, the capsules being larger and comparatively more slender than those of S. esculenta. The surface of the egg capsule is coarse; on it can be seen three to four faintly protuberant lines which spiral slightly counter- clockwise from the base of the egg capsule toward the tip. The capsules have a major axis of 27-34 mm (31.5 mm average) and a minor axis of 14-16 mm (14.7 mm average), and the individual egg is intertwined with and connected to the base through the egg stalk. Sediment particles often coat the surface, coloring it a muddy black (Fig. 3). Sepiella maindroni.-The egg is coated with much elastic, dark-brown, gelatinous substance, and measures, according to Lin (1935), 6.0-6.5 mm 334 Bulletin of Marine Science [16(2)

FIGURE 4. The eggs of Sepiella maindroni. long on the minor axis, or, according to Yamamoto (l942b), 7.5-10.5 mm on the major axis and 6.5-8.5 mm on the minor axis. The surface of the egg capsule is smooth, with no protuberant lines and usually with no adhering sediment particles (Fig. 4).

Sepioteuthis lessoniana.-The eggs are embedded in a milky-white, semi- transparent, soft gelatinous substance, and the capsules are long and slender, each capsule containing 2-9 eggs in a row (5.8 eggs average) (Choe & Ohshima, 1961). The egg capsule is 62-84 mm (76 mm average) in length, with a maximum breadth of 9-13 mm (11 mm average). The surface of the egg capsule is smooth and no sediment particles adhere to it (Fig. 5). Euprymna berryi.-The egg is heavily coated with milky-white elastic gelatinous substance, and presents a circular form, though the front end of the egg capsule projects slightly. The egg capsule is 5.2-7.7 mm (6.3 mm average) on the major axis and 4.7-5.7 mm (5.2 mm average) on the minor axis, and the surface is coarse, with irregular, faintly protuberant lines. No sediment particles adhere to it. Cephalopod eggs initially pass through a process of contraction and 1966] Choe: Rearing Cephalopods 335

FIGURE 5. The eggs of Sepioteuthis lessoniana. then increase in size again with the developing embryo and perivitelline space, reaching the maximum size just before hatching (Lin, 1935; Yamamoto, 1941, 1942a, 1942b; Choe & Ohshima, 1961). This phenomenon is typical of the egg of Sepia subaculeata; Figure 6 shows the change in size of the egg capsule during the egg development. The egg of Sepia subaculeata shows a variation of about 39 per cent for the major axis and about 50 per cent for the minor axis from its most contracted stage. For this reason, when giving a morphologic description of the eggs, size must always be correlated with age.

RESISTANCE OF THE EGG AND NEWLY HATCHED FRY TO Low SALINITY The first problem in obtaining healthy fry is the care of the eggs. As cephalopod eggs usually require a fairly long time to hatch, they are liable to be subjected to some variation in the environment. Their limitations in this respect must be considered when setting up an artificial environment. The length of time required for hatching varies greatly with water temperature for the species considered here. It is reported that Sepia esculenta requires 55-86 days to hatch at 12.3°-21.9°C or 29-42 days at 15.5°-23.6°C (Yamamoto, 1942a); Sepiella maindroni requires 336 Bulletin of Marine Science [16(2) TABLE 1 PERCENTAGE OF EGGS HATCHED AT VARIOUS SALINITIES ------Chlorinity Sepia Sepie/la Sepioteulhis (%0) esculenta maindroni lessoniana 8.4 0 0 0 10.5 0 18.8 0 12.6 46.1 37.5 9.0 13.1 10.6 14.7 65.5 50.0 22.5 15.8 25.0 16.8 57.7 62.5 47.6

28-30 days at 20°-26°C (Lin, 1935); or 35-53 days at 14.7°-23.2°C (Yamamoto, 1942b). According to the author's observations, at a water temperature of 23.5°-24.0°C, Sepia esculenta and S. subaculeata each required 29-31 days for hatching; Sepioteuthis lessoniana required 25-28 days; and Euprymna berryi required 20 days. It is logical to assume that, as both eggs and fry are kept in flowing sea water, changes in salinity will influence both the hatching and the rearing. Yamamoto (1940) reported that the minimum chlorinity at which newly hatched fry of Sepia esculenta and Sepiella maindroni can survive for 24 hours is 13.3%0 and 12.7%0 respectively, at 19.4°-22.5°C. Table 1 shows the percentage of eggs hatching in 3 liters of still sea water of various salinities at 15.0o-24.0°C. The eggs of Sepia esculenta yield a 58-66 per cent hatch and Sepiella maindroni a 50-63 per cent hatch at cWorinities of 14.7%0 or higher, and Sepioteuthis lessoniana yields a 48 per cent hatch at a chlorinity of 16.8j{0. The percentage of hatch decreases sharply, however, for each species at lower salinities. In Table 2 is shown the result of an experiment on low salinity resistance of fry which, for 5 days immediately after hatching, were reared in 25 liters of water of different salinities. Judged from this experiment, the presumed minimum chlorinity which affects the survival of each species is 13.0%0 for Sepia esculenta, 12.5%0 for S. subaculeata and Sepiella maindroni, and 14.6%0 for Sepioteuthis lessoniana. In other words, the resistance to low salinity is strongest with Sepiella maindroni and Sepia subaculeata and decreases with Sepia esculenta and Sepioteuthis lessoniana. Fifteen-day-old fry of Sepia esculenta require a slightly higher minimum salinity for survival than freshly hatched fry. In summary, a hatch of greater than 80 per cent can be expected for Sepia esculenta, S. subaculeata, Sepiella maindroni, Sepioteuthis lessoniana, and Euprymna berryi if the eggs are kept in flowing sea water of greater than 15%0 cWorinity. The fry, if kept under the same conditions, will feed and grow quite normally. 1966] Choe: Rearing Cephalopods 337 TABLE 2 RESISTANCE OF LARVAL CUTTLE-FISHES AND SQUID TO Low SALINITIES (AGE: NEWLY HATCHED FRY. MAXIMUM DURATION OF EXPERIMENT: 5 DAYS) ------Sepia Chlorinity escu/en/a (%,) 50%1 100%1 8.3 >0.5 1 10.2 4.3-5 6-8 10.9 12.2 13-22.5 34->1202 12.9 14.2 14.6 Water Temperature °C 21.3-22.5 21.7-23.5 21.3-22.5 26.7-27.7 1Figure< represent the time in hours for 50% or 100% mortality. "Indicates that 100% mortality was not reached before the end of the experiment. The mortalities after 5 days were 70% S. esculellla and 60% S. mailldrolli respectively.

REARING The egg expands gradually with the developing embryo, reaching its maximum size just before hatching. The outer cover of an egg thins immediately before hatching and becomes susceptible to any minor physical injuries. The embryo, as development proceeds, increases its activity within the egg, which, together with the thinning of the outer cover, is probably responsible for hatching. A sudden change in water temperature or in salinity, or a minor mechanical stimulus, just prior to hatching hastens the hatching of the egg, though the earlier hatched fry is likely to die due to imperfect absorption of the yolk or abnormal growth (premature hatching). Occasionally, when the egg develops under stable conditions with no unnecessary stimulus given, though the absorption of yolk proceeds satisfactorily and results in larger larvae, some of the individuals are found apparently "autointoxicated," slowed in their activity within the egg, and incapable of auto-hatching. When hatched by artificially breaking the outer cover, however, these larvae will grow normally (overmature hatching). It should be noted here that the properties of the perivitelline- space secretion of Sepia esculenta and S. subaculeata are, as far as pH and salinity are concerned, the same as those of the ambient sea water. The size-differences between premature-hatched and overmature-hatched larvae can be determined by comparing them to what may be called standard-hatched larvae. The standard-hatched larvae received natural care on the fishing ground but were placed in an experimental cistern for 2 to 5 days before hatching. Any effects of artificial stimuli should have 338 Bulletin of Marine Science [16(2)

E u 4.0 \ .!: \ \ ell \ \ 13.0~ D. o u

,, ,,

hatching~

2 4 6 8 10 12 14 16 18 Days after laid

FIGURE 6. The change of the egg size in the course of embryonal development (Sepia subaculeata). Closed circles represent the shorter diameter of egg capsule. Open circles represent the longer diameter of egg capsule. been nullified during the time in the cistern. The size differences for the three types of hatching are shown in Figures 7 and 8. Compared with the standard-hatched, the dorsal mantle length and the body weight arc smaller for the prematurely-hatched, and greater for the overmaturely-hatched. Fry of Sepia esculenta less than 4 mm dorsal mantle length and 20 mg body weight, or S. subaculeata less than 7 mm long and 100 mg in weight at hatching, seldom survive. Premature hatching is common in eggs with a soft capsule such as those of Sepioteuthis lessoniana, while overmature hatching is often observed with Sepia esculenta and S. subaculeata. Sizes of the newly hatched fry, with standard hatching, are shown in Table 3. Hatched fry, when reared in flowing sea water with proper salinity and fed from the beginning with live mysids, show a survival rate of 80 to 90 per cent (Ohshima & Choe, 1961; Choe & Ohshima, 1963). Fry of Sepia esculenta hatched under proper conditions acquire the inking ability within 7-8 hours after hatching and are capable of preying upon mysids approximately ] 0 mm long within 2-2 % days. With Sepia subaculeata, which hatch at a larger size than S. esculenta, rearing is easier and gives better results by the same method than the latter. The case is similar with Sepiella maindroni, Sepioteuthis lessoniana and Euprymna berryi. Within 1966] Choe: Rearing Cephalopods 339

90 en 80 E 70 c :c 60 m • GI 50 I ~ • • ~ 0 0 0 o "'tI>- 40 0 0 0 a:J 30 0 0 0 0 20 0

4.0 4.4 4.8 5.2 5.6 6.0 6.4 Mantle length in mm

FIGURE 7. Differences of hatched size in Sepia esculenta: Open circles, immature-hatched; closed circles, normal-hatched; circle and dot, overmature- hatched.

16 to 24 hours after hatching, Sepioteuthis lessoniana are capable of preying upon mysids 8-10 mm long. Prey attractive to the fry of these five species are, from the beginning, rather large-sized, active types. Larvae of shrimp which are similar to mysids in size make favorable prey. Daphnia, too, are preyed upon at times, though they do not seem to be as preferred. Chironomus larvae are unsuitable as prey. Young annelids are attacked but soon turned loose. It has often been observed that Sepia escuLenta or S. subacuLeata, out of hunger, attack sea lice crawling on the cistern wall above the water. A Sepia esculenta 4% days old eats a mysid 10 mm long in 40 to 56 min; an almost starved Sepia escuLenta 10 days old eats a mysid 10-12 mm long in about 10 min. Even Euprymna berryi, which is hatched at the smallest size of all, is able to prey upon mysids, approximately 10 mm long within 3 to 4 days. HABITS OF FRY Sepia esculenta.-Fry just hatched show a remarkable phototaxis, though it only lasts for 3 to 4 days. Being of a bottom-living nature, they surface and swim afloat only when they are searching for prey. When any well-fed individuals surface, it is certainly because they are physiologically affected. Moving alternatively the left and right fourth arm, they swim as if they 340 Bulletin of Marine Science [16(2) TABLE 3 THE SIZE OF NEWLY HATCHED FRY

------Sepia Sepia Sepiella Sepioteuthis ElIpr)'lIlna esculenta suhaclileata l11aindroni lessolliana berryi Mantle length Range 5.1-6.4 7.2-9.7 4.0-5.0 4.7-7.2 2.4-2.8 (mm) Average 5.72 8.72 4.61 5.59 2.63 Body weight Range 48-77 80-186 38-45 23-60 7-12 (mg) Average 61.6 151.1 41.5 37.0 9.4 Arm formula of length 4>1>3>2 4>1>3~2 4>1~2>3 3>2>4>1 2>3>4~1 were creeping on the cistern bottom. When catching prey still on the bottom, they approach it in a peculiar way, as they swing their left and right arms widely to the side. In the cistern, they habitually swarm together, but no swimming in a group has been observed. Individuals of more than 20 mm in mantle length hunt living shrimp and also eat pieces of dead fishes. Sepia subaculeata.-No phototaxis is observed at all in this species. They are, as with S. esculenta, of a bottom-living nature and swim as if creeping. When they aim at prey, they approach it with their first arms swinging to the left and right. Unlike S. esculenta, they are not gregarious and distribute uniformly in the cistern. They are more sluggish than S. esculenta and not excitable. When surprised, they stretch out their arms in an intimidating posture. As they grow, they begin to feed even on dead prey. The fascia in yellowish blue or yellowish purple on the mantle edge is characteristic. Sepiella maindroni.-Unlike Sepia esculenta or S. subaculeata, they have a strong shoaling instinct, and, except for the resting time at night, remain swimming afloat. In later stages, they can be easily reared even with dead prey. Sepioteuthis lessoniana.-Each individual has, as with Sepiella maindroni, a strong shoaling habit and swims the most brisk, varied sort of swimming. Live prey is necessary for successful rearing; they rarely feed on dead prey or prey on the bottom of the cistern. Euprymna berryi.-Being solitary and bottom-living, they only rise for feeding. Aiming at prey, they bind their arms into a stretched-out sheaf and, swimming briskly around the target, hunt in a bold manner that is rare with any of the other four species. Except for hunting, they hide under a shelter by camouflage, with debris attached to the body surface by a slime secretion. 1966] Choe: Rearing Cephalopods 341

180 m • E 160 c o (;) I .s:.- 140 S. I • m 00. •; 120 • ~ o • • o o ~ 100 0 o 8 a:I 80 o

7.0 7.4 7.8 8.2 8.6 Montie length in mm FIGURE 8. Differences of hatched size in Sepia subaculeata: Open circles, immature-hatched; closed circles, normal-hatched; circle and dot, overmature- hatched.

GROWTH Sepioteuthis lessoniana (hatched on June 24) and Euprymna berryi (hatched on May 22) were reared in 167 cm X 167 cm cisterns and fed with mysids. Sepia esculenta (hatched on June 6), S. subaculeata (hatched on June 26) and Sepiella maindroni (hatched on June 19) were fed with mysids in cisterns of the same size for 30 days after hatching, and then each species was divided into seven individual groups, and fed with small-sized live shrimp or fishes. The growths observed are shown in Figures 9 and 10. The sea water temperature and salinity conditions under which they were reared are seen in Figure 11. Sepia subacu/eata and Sepiella maindroni were moved into larger cisterns (335 cm X 335 cm extent) 70 to 80 days after hatching. Sepia subaculeata, a large-sized species, reached 350-400 gr in body weight or a full commercial size in 110 days after hatching. Sepioteuthis lessoniana, another large-sized species, is expected to make a growth no less than that of Sepia subaculeata, provided that it is fed, 20 to 30 days after hatching, with live prey larger than mysids. Yasuda (1951) and Tomiyama (1957) have reported on the natural growth rates of Sepia esculenta, but these authors could not be certain of the age of their specimens, so the present data could not be compared with their figures. When compared on the basis of the date, the reared specimens show higher growth rates. The average number of mysids captured per day by an individual Sepia esculenta was 4 on the 4th day after hatching, 24 on the 15th day, 106 342 Bulletin of Marine Science [16(2)

200 ~I~ 100 ~ ~.fl E / mt---I .••...• y E 70 V J~ - 1;-r c: 50 ~~fI1~ -'= -m c: 30 Q) 0.:I~tJ/9t ~ -Q) 20 -c: EtTJ~ C ~ /~ 10 ~....., ~

20 30 50 70 100 period of rearing in days

FIGURE 9. The growth (mantle length) of Sepioteuthis lessoniana (EB), Sepia subaculeata (0), Sepiella maindroni (.), Sepia esculenta (0), and Euprymna berryi (().

on the 25th day, and 243 on the 30th day (Fig. 12). Calculated from this, the daily feeding rate for Sepia esculenta ranges between 17 and 43 per cent. With a water temperature higher than 20°C, this rate is maintained continuously at 20 per cent. The feeding rate of Sepia subaculeata and Sepiella maindroni was between 25 and 31 per cent at a water temperature higher than 20°C. Feeding rate, as a percentage, is equal to feeding amount/body weight X 100. 1966] Choe: Rearing Cephalopods 343

400 ~ 300

200

(. 0, 100 II I 70 ~ I i[ 50 J111/

'r 30 J

20 ~ m"- (. ~ c: I ..r:: 10 -m III 7.0 3: 1// _ 5.0 >- 1/ ."0 al 4- - 3.0 /;,1,,,2 2.0 f/

1.0 / w 0.7 0.5 m

0.3 ? 0.2 -L

20 30 50 70 100 Period of rearing in days FIGURE 10. The growth (body weight) of Sepioteuthis lessoniana ($), Sepia subaculeata (0), Sepie/la maindroni ( • ), Sepia esculenta (0), and Euprymna berryi «). 344 Bulletin of Marine Science [16(2)

~. ~ 30 >. -c ~ 28 0 ~ 26 u

""'0 c: 24 0 ~ v 22 ..2- ~41 ::I -~0 41 D- E .!

L 41 12 ~ 30 10 20 30 10 20 30 10 20 30 1020 30 10 20 30 May+---June --+--July ----tl•...August--+September~I<-October->1 Dare

FIGURE 11. Water temperature (closed circle) and chlorinity (open circle) during the rearing of cuttlefishes and squids.

DISCUSSION In recent years, the tendency towards artificially and rigidly controlled culturing of high-cost marine products has gradually increased, demanding more and more research into the production of fry of the involved species. The Cephalopoda are generally rapid in their growth and, especially in Japan and Korea, there are many species which have a high economic value. The rearing of these species has, therefore, a great industrial potential. Although there have been no previous reports available on the rearing of Cephalopoda, the author has succeeded in rearing newly hatched fry to a near-adult stage with Sepioteuthis lessoniana of the Loliginidae, Euprymna berryi of the Sepiolidae, and Sepia esculenta, Sepia subaculeata and Sepiella maindroni of the Sepiidae. A necessary step in the rearing of fry is, first, to get healthy fry. In view of a rather long period required for hatching, successful rearing presupposes, as a matter of course, good care of the eggs. When kept in flowing sea water with more than 15%0 chlorinity and without direct exposure to the sun, one can be assured of a hatching rate of greater than 80 per cent. The direct exposure of the eggs to the sun results not only in 1966) Choe: Rearing Cephalopods 345

240

Q. 220 E •..200 ..c lit ~ 180 lit >- E 160

0 - 140 lit•.. Q) ...c 120 E ~ c: 100 50 -~ 0 ,0, .•...... ~ 80 I \. 40 Q) "'C I \. ,,0 , \. / > , - .- 60 '0'" 30 ~ "'C /5 c: ,, m 40 0- ____<::/ 20~ Q) 20 10 .f • 5 10 15 20 25 30 Days after hatching

FIGURE 12. Relationship of numbers of living mysids captured (closed circle) on a per-day basis to age (days) and feeding rates (open circle) (Sepia esculenta).

an abnormal embryonic development due to the wide range of water temperature, but also in an unsatisfactory hatching due to the attachment of great quantities of diatoms or green algae to the egg capsule. Observations reveal the prey suited for the feeding of fry are, from 346 Bulletin of Marine Science [16(2) the start, rather large-sized, active species. As for the five species mentioned above, live mysids (Neomysis japonica) 1 to 12 mm long are, even at the earliest stage, a very favorable prey, effecting a survival rate of 80 to 90 per cent. For rearing Sepia esculenta fry in large numbers, it has been found that six fry per 100 sq cm of surface area is the most effective concentration up to a dorsal mantle length of 20 mm. This accommodation can be far heightened by adding such other natant species as the concentration of the dissolved oxygen permits. Especially in the case of Sepiidae, when the fry reach a dorsal mantle length of greater than 20 mm, it is advisable to give more and more water space. A narrower cistern usually results in reduced growth, or death, of individuals that clash against the wall and sustain injuries at the rear part of the body. When the water oxygen content falls to 31 to 48 per cent, Sepia esculenta is affected by the oxygen deficiency, whereas S. subaculeata several days old are not affected, even at an oxygen content as low as 13.5 per cent. Sepia subaculeata and Sepiella maindroni are comparatively strong in their ability to withstand a decrease in dissolved oxygen, while Sepia esculenta and Sepioteuthis lessoniana are weak in this respect and grow more susceptible with age. So that these species will feed normally, it is necessary to maintain the oxygen content at 65-70 per cent or higher. As this report has illustrated, artificially reared Sepia esculenta, for example, surpasses the naturally reared ones in growth, and S. subaculeata is reared to a body weight of 350 to 400 gr or to a full commercial size within 110 days after hatching. A fair expectation even with other species is that they will reach full commercial size in 4 or 5 months, if the food is changed according to the stages and the water space is sufficient to allow proper feeding.

SUMARIO SOBRE LOS HUEVOS, CRIA, HABITOS DE LOS ALEVINOS y CRECIMIENTO DE ALGUNOS CEFAL6PODOS Sabre la base de datos obtenidos en ]a cria de alevinos de Sepia esculenta, Sepia subaculeata, Sepiella maindroni, Sepioteuthis lessoniana y Euprymna berryi, e1 autor trata aqui de la epoca de la puesta, morfologia externa de los huevos, resistencia de los huevos y de los alevinos a la baja salinidad, los habitos de los alevinos y el crecimiento durante la cria. 1. En ]a puesta ]a temperatura del agua es: 10-20°C para Sepia esculenta, 15-20°C para Sepia subaculeata y Sepiella maindroni, 14-2] °C para Sepioteuthis lessoniana y 17-21°C para Euprymna berryi. 2. Teniendo el agua una temperatura de 23.5-24.0°C, los dias requeridos para ]a incubaci6n son: 29-31 para Sepia esculenta y Sepia subaculeata, 25-28 para Sepioteuthis lessoniana y 20 para Euprymna berryi. ] 966J Choe: Rearing Cephalopods 347 3. Los huevos de decapodos cefa16podos cuando se mantienen en agua de mar circulando, de una c10rinidad de mas de ] 5%0 Y sin exponerse directamente al sol dan una cria de mas del 80 por dento. 4. Grandes presas m6viles son las favoritas de las crias de decapodos cefa16podos aun en los estados mas tempranos. Cuando se crian con Neomysis japonica viva (1-12 mm de longitud) con manto dorsal de hasta 20 mm de longitud, tienen una supervivencia de 80-90 por ciento. 5. La minima salinidad a la que los alevinos pueden supervivir con una alimentaci6n normal es: 13.0%0 de c10rinidad para Sepia esculenta, 12.5%0 para Sepia subaculeata y Sepiella maindroni y 14.6%0 para Sepioteuthis lessoniana. 6. Los alevinos de Sepia esculenta y Sepia subaculeata tienen naturaleza de moradores de fondo aunque la primera tiene un fuerte habito de agregaci6n y la ultima una fuerte tendencia a la independencia. Tanto Sepiella maindroni como Sepioteuthis lessoniana son nadadoras y extra- ordinarias en sus Mbitos de agrupaci6n. 7. Todas las especies son rapid as en su crecimiento. Cuatro 0 cinco meses se cree son suficientes para que a1cancen un buen tamaiio comercial.

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SASAKI, M. 1929. A monograph of the dibranchiate cephalopods of the Japanese and adjacent waters. Fac. Agric. Hokkaido Univ., Suppl., 20: 1-357. TOMIYAMA, A. 1957. On the cuttle-fish, Sepia esculenta Hoyle. Bull. inland Fish. Exp. Sta., Yamaguchi, 9: 29-39 (In Japanese). Voss, G. L. 1956. A review of the cephalopods of the Gulf of Mexico. Bull. mar. Sci. Gulf Carib., 6: 85-178. YAMAMOTO, T. 1940. Mortal influence of salinity on some cephalopod larvae. Botany Zool., Tokyo, 8: 1879-1882 (In Japanese). 1941. Some observations on the embryonal development of the eggs of Octopus ocellatus Gray. Botany Zool., Tokyo, 9: 239-243 (In Japanese). 1942a. Embryonal development of Sepia esculenta Hoyle. Botany Zool., Tokyo, 10: 125-130 (In Japanese). 1942b. On the embryonal development of Sepiella japonica Sasaki, with observations on its larval habits. Botany Zoo!., Tokyo, 10: 443-448 (In Japanese). YASUDA, J. 1951. Some ecological notes on the cuttle-fish, Sepia esculenta Hoyle. Bull. Jap. Soc. sci. Fish., 16: 350-356 (In Japanese).