Laboratory Observations on Spawning and Embryonic Development of a Blue-Ringed Octopus

View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by OceanRep Marine Biology 27, 333-337 (1974) by Springer-Verlag 1974 Laboratory Observations on Spawning and Embryonic Development of a Blue-Ringed Octopus H. Overath I and S. von Boletzky 2 ;Institute of Neurobiology; JHlich, Germany (FRG) and 2C.N.R.S., Laboratoire Arago; Banyuls-sur-Mer, France Abstract from blue-ringed octopus bites follow an almost repetitive pattern" (Friese, ]972). Hapalochlaena A female blue-ringed octopus,Hapalochlaena sp. maculosa, the species living "in the more sub- (probably lunulata), was maintained in an aquarium tropical and temperate waters of the eastern coast for nearly 3 months, during which time it spawned of Australia" (Friese, ]972), has been studied by and cared for the eggs until hatching. The young several authors, and this species has also been are planktonic. Embryonic development does not reared in the laboratoy (Tranter and Augustine, differ markedly from that observed in other octo- 1973). Little is known, apparently, of the biology pods, uniting certain features of the development of the somewhat larger H. lunulata whose"distri- of Octopus vulgaris and Eledone cirrosa. In terms bution seems to extend from the northwest coast of of reproductive biology and development, the Australia throughout the Indo-Malayan Archipelago" species differs from the lesser blue-ringed octo- (Friese, 1972). pus Hapalochlaena maculosa in its mode of spawning, The present note is intended to draw attention egg size and mode of life of its young. These to the particularities concerning reproduction, differences correspond to conditions recorded for embryonic development and characteristics of newly- Octopus spp. and Eledone spp. hatched young of Hapalochlaena lunulata as com- pared to H. maculosa. The authors hope that biol- ogists working in the area where H. lunulata is Introduction apparently abundant will further contribute to the knowledge of this interesting species. The genus Hapalochlaena was created by Robson (1929) for the two known species of "blue-ringed octopus" from the Indo-Pacific Ocean, Octopus Material and Methods lunulatus Quoy and Gaimard, 1832, and Octopus pictus Brock, ;882. As the name O. pictus was pre- An adult female octopus (total length ca. 20 cm) occupied, Octopus maculosus Hoyle, 1883, was vali- was bought from a local dealer, by the first dated (Robson, 1929). Concerning his new genus, author, in late March 1973; the octopus was the Robson himself stated: "As for the generic status last surviving of a batch of 6 received from of these two species I am very doubtful", and Voss Manila, Philippine Islands. The octopus was (1971) actually considers them as species of Octo- placed in an aquarium with a closed-system sea- pus Lamarck (we retain here Robson's generic water supply (23 ~ to 24~ at the Institute of designation only because it is the mostly widely Neurobiology, JOlich (FRG). It was fed crabs and used, without stressing its taxonomic validity). the meat of mussels. When the octopus spawned, Adam (1938) described a new species of Octopus some eggs were taken from the aquarium for obser- (0. ~ierstraszi) from the Andaman Islands, and vation and photography and maintained in separate stated that this species shows several character- tanks, at a temperature of 26~ Newly-hatched istics of Robson's genus Hapalochlaena. A revision octopuses were kept in several aquaria and were of the systematics and distribution of blue-ringed presented with different food organisms such as octopuses, by Dr. G.L. Voss (University of Miami), Artemia salina and other small Crustacea. is actually planned (Voss, personal communication). A brief account of this experiment has been Until this study is completed, we consider the published earlier, by the first author who is identification of the species dealt with in the mainly interested in problems of laboratory main- present note as provisional. However, for easier tenance of marine animals (Overath, 1973). Upon reading, we use "H. lunulata" instead of the safer reading this report, the second author of the "Hapalochlaena sp. (probably lunulata)". present note inquired about the species of octopus In recent years, the little, colourful, blue- observed. The identification as Hapalochlaena ringed octopus has won singular fame as "Mini- lunulata was then ascertained, as far as this is Killer" (Cropp, 1972) and "Death in a small pack- possible, and it was decided to publish the obser- age" since "human fatalities and near fatalities vations in more detail, in order to compare them 354 H. Overath and S~ von Boletzky: Development of a Blue-ringed Octopus Fig. I. Hapalochlaena lunulata. Embryonic development. (a) Egg cluster with embryos at late develop- mental stage, prior to second reversion; (b) embryo at about Stage XV of Naef (1928), with still very large outer yolk sac; (c) similar stage, at higher magnification - note small size of inner yolk sac, comparatively long arms, dark pigmentation of retina; (d-f) later stages showing decreasing size of outer and increasing size of inner yolk sac, chromatophores on head (d) and on body and arms (e, f); (f) shows normal hatching position after second reversion; arrows indicate area shown in (g) with KSlliker organs, x marks the mantle ganglion. (Scale = I mm) H. Overath and S. von Boletzky: Development of a Blue-ringed Octopus 385 to the data of Tranter and Augustine (1973) on H. Embryonic development of Hapalochlaena lunulata maculosa and to discuss them with regard to general largely corresponds to that of Octopus vulgaris, characteristics of octopod development. The first whose eggs are slightly smaller (Naef, 1923, 1928; author provided all data from which the second Portmann, 1933), and of O. salutii (Boletzky, un- author compiled the present note. published), O. joubini (Boletzky, 1969), Eledone cirro~a (Mangold et al., 1971; Fuchs, 1973) and Hapalochlaena maculosa (Tranter and Augustine, Observations 1973), all having larger eggs. During organogenesis, the embryos reverse their position in the egg-case During the first 2 weeks of observation, the fe- (chorion), the animal pole taking up its position male Hapalochlaena lunulata fed regularly, and at the side of the chorion stalk (cf. Boletzky, frequently moved about in the tank. When the octo- 1971a, b). As in other cephalopod embryos, the pus was disturbed, e.g. by a strong light, the yolk apparatus becomes divided into an outer and typical iridescent blue rings in the integument an inner yolk sac; the latter decreases in size, became particularly distinct. Sometimes, however, during organogenesis and onward until about Stage the colour was rather uniformly greyish. The XV of Naef (1928) (Fig. Ic); in later stages, its general behaviour was in every respect that typi- size again increases by yolk transfer from the cal of benthonic octopods (cf. Lane, 1960). After outer yolk sac (Fig. Id-f; cf. Portmann, 1926). In two-and-a-half weeks, the octopus ceased feeding H. lunulata, the relative size of the outer yolk and actively rejected offered food; 3 days later, sac is somewhat larger, until late stages, than in it started spawning. Several clusters of about 20 O. vulgaris. The chromatophore development and eggs each (Fig. la) were attached to the wall of distribution closely resemble those of O. vulgaris the aquarium, close to the water inflow [the size (cf. Fioroni, 1965); chromatophores are absent of these eggs (ca.3.5mm) is consistent with Adam's from the dorsal mantle integument (unlike in H. (1954) description of apparently immature ovarian maculosa), but present on the dorsal wall of the eggs (2.5 mm) in H. lunulata]. The octopus cared visceral mass. As in H. maculosa, the iridescent for the eggs in the manner known for other ben- blue rings do not appear during embryonic develop- thonic octopods. Ten days from the beginning of ment. The integumental KSlliger organs, found in spawning, the octopus again accepted food. It died most octopod embryos, are present in H. lunulata about 3 weeks after the last young had hatched. (Fig. Ig). In contrast to O. vulgaris, the later Fig. 2. Hapalochlaena lunula~a. Young, about I day after hatching. (a) Normal swimming position; (b,c) exceptional "sitting" posture (see text). Note comparatively small size of visceral mass (cf. Fig. If), due to decreased inner yolk sac 336 H. Overath and S. von Boletzky: Development of a Blue-ringed Octopus embryonic stages are characterized by considerable Table I. Ho~alochlaena. Comparison of data on growth of the arms, with continual formation of spawning and development of H. lunulata suckers in an increasingly distinct biserial (present study) and H. maculosa (from arrangement (see below), Tranter and Augustine, ;973) Around Stage XIX of Naef, the embryos again reverse their position so that the mantle lies at the free end of the chorion (cf. Portmann, 1933). H. lunulata H. maculosa As in other octopods, this second reversion does not always occur. The octopuses then hatch at the Mode of spawning Egg clusters Egg clusters side of the chorion stalk (Boletzky, 1966). attached to carried by At a temperature of 26~ embryonic development substrate mother took about 25 days; it was slower at lower tem- peratures (Table I; cf. Mangold and Boletzky, Egg size (length of ca. 3.5 mm 6 - 7 mm 1973, for Octopus vulgaris). The outer yolk sac chorion excluding was almost completely taken in by the young Hapa- stalk) lochlaena lunulata by the time of hatching. This demonstrates that hatching was normal (premature hatching with a comparatively large outer yolk sac Length of embryonic is a phenomenon frequently observed in cephalopod development at embryos raised under artificial conditions). 21~176 ca. 60 days Newly-hatched H~palochlaena lunulata are plank- (Stage XV - tonic. In terms of morphometrics, they are quite Stage XX: similar to the planktonic young of Eledone cirrosa 25-35 days) that are, however, much larger (Mangold et al., 23~176 ca.

Load more