Family SEPIOLIDAE

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Family SEPIOLIDAE

Compiler and date details

July 2001 - C.C. Lu, National Chung Hsing University, Taichung, Taiwan

Introduction

Sepiolids are small animals of less than 10 cm mantle length (ML). The Sepiolidae Leach, 1817 is very speciose family, comprising 13 genera in three subfamilies: Sepiolinae Appellöf, 1898; Heteroteuthinae Appellöf, 1898; and Rossiinae Appellöf, 1898. In Australian waters, subfamily Sepiolinae is represented by several species in the genera Euprymna and Sepiola; Heteroteuthinae is represented by several species of the genera Heteroteuthis, Iridoteuthis and Sepiolina; and Rossinae is represented by several species in the genera Rossia and Neorossia. Fifty-six nominal species are known worldwide, and nine species are known from Australian waters. At least six additional new species await naming and full description (Lu, unpublished data).

Although this is a large and diverse family with members occurring in all oceans, it has never been reviewed taxonomically in great detail. Naef (1923), Sasaki (1929) and Voss (1955, 1956, 1963) have treated regional faunas, i.e., the Mediterranean, Japanese, Caribbean Sea and Gulf of Mexico, and the Philippines faunas, respectively in some detail, but Joubin's (1902) work remains the only major taxonomic revision on a worldwide basis.

The first Australian record of a member of this family is of Sepiola tasmanica, described from a specimen from Bass Strait (Pfeffer 1884), and currently known as Euprymna tasmanica (Sepiolinae). Brazier (1892), in his catalogue of cephalopods from Australia, listed Sepiola rondeletii, Inioteuthis stenodactyla, and Inioteuthis tasmanica; the identity of the animal Brazier referred to as Sepiola rondeletii is unclear; the other two species are now referred to the genus Euprymna. Berry (1918) described Rossia australis (Rossinae) from the Great Australian Bight. Allan (1945) described Heteroteuthis serventyi (Heteroteuthinae) from near Jervis Bay, New South Wales. Lu & Phillips (1985) published the first Australian records of the genera Iridoteuthis and Sepiola (from unidentified species) and of Sepiolina nipponensis. Adam (1986) described Euprymna hoylei from northern Western Australia and Reid (1991) reviewed the Australian Rossiinae and described Neorossia leptodons from south-eastern Australia. Norman & Lu (1997) redescribed Euprymna tasmanica from southern Australia and revised the genus.

Little is known of the life history and biology of most sepiolids, and nothing is known about food and feeding of Australian sepiolids. A study on Rossia pacifica, a species common in the North Pacific, from Japan to California, reported that 80% of their diet in their natural habitat consists of shrimps, crabs, small fishes and cephalopods (Brocco 1970; Hochberg & Fields 1980). Aside from Lu (2001), data on non-Australian sepiolids are derived largely from diets given in laboratory rearing experiments. For example, Rossia macrosoma of the Mediterranean Sea was fed live prawn (Boletzky & Boletzky 1973). Euprymna berryi, a species found in China, Japan and Korea, has been reared on live mysids (Choe & Oshima 1963; Choe 1966). Adult Euprymna scolopes, from Hawaii, were reared on adult Leander debilis and Gambusia affinis. Laboratory-hatched young of E. scolopes were fed Anisemysis, Artemia salina and occasionally newly hatched Octopus cyanea (Arnold et al. 1972). Boletzky et al. (1971) reared six sepiolid species in the Mediterranean in a laboratory (Sepiola rondeleti, S. robusta, S. affinis, S. ligulata, Sepietta obscura, and S. neglecta): young animals were fed mysids (Leptomysis mediterranea); older juveniles and adults were fed Leander species. Boletzky (1983) also fed Sepiola robusta with crangonid shrimps of the genus Philocheras. Bergstrom & Summers (1983) successfully cultured Sepietta oweniana in aquaria, feeding juveniles on mysids (Praunus flexuosus and P. inermis), amphipods (Ericthonius) and large copepods; on rare occasions cannibalism occurred. The adults were fed one of the mysids (Praunus flexuosus) as well as shrimps (Palaemon elegans, Thoralus cranchii and Crangon crangon).

Much of the information on eggs and egg-laying also derives from laboratory studies. In aquarium studies (English 1981), Euprymna tasmanica laid eggs individually; the eggs were attached to the substratum and to adjoining eggs in the clutch. Each egg was coated with a tough, opaque gelatinous capsule, and development took approximately 29 days at 20°C. Similar eggs have been described for another sepioline, Sepiola robusta (Boletzky 1987). Nothing is known about the eggs of Australian Rossinae and Heteroteuthinae. Rossia palpebrosa of the North Atlantic laid eggs in sponges (Akimushkin 1963; Aldrich & Lu 1968), Rossia macrosoma laid in bivalve shells (Boletzky & Boletzky 1973), and Rossia pacifica attached its eggs, singly or in small groups, to seaweed or other objects on the bottom (Hochberg & Field 1980).

Most benthic sepiolids (Rossinae and Sepiolinae) bury themselves in the soft bottom sediments during the day. This 'burrowing' process is reported to have two phases. In the first phase, the animal blows the sand with jets of water, gradually settling down as it does so. In the second phase, the dorso-lateral arms are stretched out over the surface to gather sand particles to completely cover the animal. This behaviour has been observed in four species of Sepiola and three species of Sepietta (Boletzky & Boletzky 1970; Bergstrom & Summers 1983). Newly hatched Euprymna tasmanica settled immediately and adopted the benthic mode of life of adults; within one day of hatching juveniles initiated burying behaviour, but no successful burying was achieved prior to death at three days old in aquaria (English 1981).

Many sepiolids have luminescent organs, including Australian sepiolids in the genera Heteroteuthis, Iridoteuthis, Sepiolina, Sepiola and Euprymna. Herring (1988) reviewed information on these organs in cephalopods: in Sepiola and Euprymna they are paired, separate and ear-shaped, while in Heteroteuthis, Nectoteuthis, Iridoteuthis, Stoloteuthis and Sepiolina the paired structures are fused to form a single rounded entity. It is generally accepted that bacterial luminescence is involved in sepiolid photophores, although luminescent bacteria have not been identified or cultured in vitro for some genera, such as Heteroteuthis and Sepiolina. Nothing is known about the luminescent organs of any Australian sepiolids.

Ecological Descriptors

Marine.

Diagnosis

The mantle is short with the posterior end rounded. The anterior dorsal mantle margin may be fused with the head or articulated by means of nuchal cartilages. The head is large, as wide as, or wider than the mantle. The fins are lateral, large, kidney-shaped with well-developed anterior lobes. The tentacles are retractile with a well-defined club. The arms are short, and lack protective membranes. The gladius, if present, is chitinous and rudimentary; in some genera it is absent. Most members of the family have luminous organs on the ink sac. In males, one or both dorsal arms or a laterodorsal arm are hectocotylised. In females, only the left oviduct is developed.

Members of the subfamily Sepiolinae are distinguished by the fusion of the anterior dorsal mantle margin with the head by a muscular band. The nuchal cartilage is absent. The funnel-mantle locking cartilages are simple, straight lines. The arm suckers in most taxa are biserial, except in the genus Euprymna where they are tetraserial (with the exception of the Philippines species, E. phenex Voss, 1962, which has biserial arm suckers). The club suckers are in 4, 8, 10 or more series, depending on the generic identity. The shell is absent in the genus Euprymna, while in the remaining genera e.g. Sepiola, Rondeletiola, Sepietta and Inioteuthis, the shell is present but rudimentary.

Members of the subfamily Heteroteuthinae have their anterior dorsal mantle margins either articulating with the head by the nuchal cartilage (Heteroteuthis, Nectoteuthis) or completely fused with the head (Iridoteuthis, Sepiolina and Nectoteuthis). The ventral mantle margin may, extraordinarily, extend forward covering the funnel and part of the head (Iridoteuthis and Nectoteuthis) or may project forward only slightly (Stoloteuthis and Sepiolina) or be intermediate between these two states, as in Heteroteuthis. In all taxa, the first three pairs of arms are united by a deep web. The arm suckers are in two series. The fins are large. The shell is absent. Coloration is rich, with a metallic sheen. Most members of the subfamily have luminescent organs on the ink sac.

Members of the subfamily Rossinae have large semicircular fins with conspicuous anterior lobes sometimes reaching beyond the mantle margins. The posterior lobes of the fins are barely discernable. The mantle margins are connected with the head dorsally by means of the nuchal cartilage and ventrally by the funnel-mantle locking cartilages. The nuchal cartilage is spade-shaped. The funnel locking cartilages are oval, deeply grooved. The large funnel reaches the level of the centre of the eyes. The arms are short with 2 series of suckers which are spherical with the aperture minute. In males both dorsal arms are hectocotylised. The tentacles are long and slender and bear an elongate club occupying about ¼ of the length. The club is not expanded and is covered on its oral aspect with numerous minute suckers. The gladius is chitinous and rudimentary, slender, lanceolate and shorter than the body. The surface of the body is smooth. The chromatophores are several shades of reddish brown.