click for previous page Sepiidae 723 Sepiidae SEPIIDAE Cuttlefishes biserial suckers by A.L. Reid tentacular tetraserial club suckers stalk hectocotylus buccal membrane normal pocket for suckers at retractile distal end swollen dorsal tentacle of arm mantle protective funnel membrane fin proximal half of arm modified: modified region transverse folds suckers with reduced reduced, suckers widely spaced, and arm normal suckers swollen at proximal end of arm spine a) b) ventral view (after Sasaki, 1929) (after Nesis, 1982) Fig. 1 diagram of basic cuttlefish features Fig. 2 examples of male hectocotylized arms 5 suckers in (oblique) transverse row club suckers swimming uniform keel dorsal in size protective dorsal membrane club suckers protective differ in size, ventral membrane medial suckers protective swimming enlarged membrane keel dorsal and dorsal and membrane ventral ventral separating protective protective sucker-bearing membranes membranes face of club joined not joined from stalk a) Sepia apama b) Sepia esculenta c) Sepia latimanus (after Lu, in press) (after Okutani et al., 1987) (after Roper et al., 1984) Fig. 3 tentacular clubs 724 Cephalopods anterior last loculus (anterior smooth zone of cuttlebone) anterior striae anterior inverted striae U-shape inverted V-shape median sulcus (furrow) outer cone keel inner cone inner cone spine with keel forming a spine (ridge) thickened ledge posterior (or rostrum) posteriorly ventral view a) lateral view b) Fig. 4 cuttlebone I II IV I II IV III III buccal membrane funnel locking funnel valve cartilage mantle locking mantle cartilage funnel locking funnel organ cartilage anus renal gill papilla anus gill accessory nidamental genital genital gland opening opening nidamental gland renal sac fin ink sac ink sac ovary (containing a) male b) female eggs) Fig. 5 mantle cavity (Sepia officinalis) Sepiidae 725 iagnostic characters: Small to medium-sized cephalopods. Mantle robust, slightly flattened dor- Dsoventrally, may be broad or slender; oval, oblong or nearly circular in outline; anterior dorsal mantle margin projected forward, not fused with head. Fins narrow, located dorsolaterally on mantle, approximately equal to mantle length; posterior fin lobes free, not connected to each other (Fig. 1). Head robust, slightly narrower than mantle; eyes prominent, covered by a transparent membrane and a conspicuous secondary fold on the eyelid. Mouth surrounded by 10 appendages (8 arms, 2 tentacles). Arms with 2 to 4 suckers in transverse rows (Fig. 1). Males of some species with hectocotylized ventral arm(s) IV for holding sper- matophores; when present, usually consists of a modified region of reduced suckers (Fig. 2); hectocotylized region may also be swollen and crenulated by transverse folds (Fig. 2b). Tentacular clubs (Fig. 3) with 4 or more suckers in transverse rows; tentacles retractile into pockets on the ventrolateral sides of the head (Fig. 1). Arm and club suckers with chitinous rings. Mantle locking apparatus angular (Fig. 10a) or curved (Fig. 10b) in shape. Internal calcareous cuttlebone (Fig. 4) located dorsally underneath the skin, cuttlebone length usually equal to mantle length; cuttlebone shape ranges from lanceolate, oval, to diamond-shaped; dorsal side a calcareous plate (dorsal shield); ventrally, finely laminate, porous and comprised of thin, transverse septa supported by transverse calcareous rods. One pair of gills (Fig. 5); no branchial canal between afferent and efferent branchial blood vessels. Liver divided or bilobed. Buccal membrane present (Figs 1 and 5), with or without suckers; each radula tooth unicuspid (with a single projection). Olfactory organ a ciliated pit. Habitat, biology, and fisheries: On the continental shelf and upper slope to a maximum depth of approximately 600 m. Primarily bottom dwellers over a range of habitats, including rocky, sandy and muddy bottoms to seagrass, seaweed and coral reefs. Slower swimmers than the more streamlined squids. Able to attain neutral buoyancy by regulating the relative amounts of gas and fluid in the chambers of the cuttlebone; able to hover in midwater, with fins acting as stabilisers. Some species migrate seasonally in response to temperature changes and aggregate, usually in shallow water, at the time of spawning. Within a species, individuals may attain sexual maturity at very different sizes, depending upon the combined effects of temperature and light. Eggs, relatively few in number, are individually attached to various substrates in clusters; length of development varies with temperature. Life span (studied for Sepia officinalis) between 18 months and 2 years, though males may live longer; post-spawning mortality is high in females. Prey on a wide range of invertebrates and fish. Many species of cuttlefish are important to fisheries in the area. Fishing activity ranges from local, or subsistence fisheries, to major export industries. Sepiids are also an important component of finfish and prawn trawl bycatch in the area. They are used primarily for human consumption, but also as bait and are marketed fresh, frozen or dried. In 1995, FAO’s Yearbook of Fishery Statistics reports 96 198 t of cuttlefish (and bobtail squids) from the Western Central Pacific (about 44% of the total world catch of cuttlefish for that year). This figure comprises 42 700 t caught off Thailand, 37 000 t from Viet Nam, 2 836 t from the Philippines, and 3 t from Australia. Similar families occurring in the area Some species are superficially similar in appearance to the loliginid squid genus Sepioteuthis, but can be readily distinguished due to the presence of a calcareous cuttlebone in the sepiids. Loliginidae Sepiidae (Sepioteuthis) Identification note The taxonomy and biology of the cuttlefish from the area is generally poorly known and in need of review. While some, particularly commercial species, can be easily recognized, others which may occur in catches are not well defined. This presents difficulties in attempting to construct a key to all species occurring in the area, as particular character states for many species have been incompletely documented. For this reason, the key below should only be used in combination with the species accounts to follow to confirm identification. Many distinguishing features are seen only in males, so animals of this sex are generally required for identification. Where possible, however, features of the cuttlebone and tentacular clubs have been included in the key to enable females to be identified. Males can often be recognized by the presence of a hectocotylus. One (usually the left), or both ventral arms (IV) may be modified. Not all species have a hectocotylus. In addition, in juvenile males this secondary sexual character may not be fully developed, so 726 Cephalopods it may be necessary to check internal anatomical features to determine sex. To examine the contents of the mantle cavity, a median longitudinal incision needs to be made through the mantle on the ventral side of the animal. The internal features of males and females are shown in Figure 5. Mature females can readily be distinguished from males by the presence of a pair of leaf-shaped creamy yellow nidamental glands (Fig. 5b). Eggs may also be seen in the ovary, below and posterior to the nidamental glands. In immature females, the nidamental glands may be greatly reduced in size or visible only as two short slits. The shape of the male and female genital openings on the left side of the mantle cavity also differs slightly between the sexes (Fig. 5a, b). Any body patterning, such as transverse wavy lines or bands on the dorsal side of the mantle, is usually more pronounced in males and may be faint or absent in females. The number and size of the tentacular club suckers are important traits. If the tentacles are retracted, they can readily be extracted in fresh animals by gently probing inside the pouches between arms III and IV on either side of the buccal mass (Fig. 1). Extraction of the club may be more difficult in preserved specimens and dissection may be necessary.The number of club suckers given for each species, and used in the keys, refers to the number of suckers in transverse rows. This is determined by counting the number of suckers that are intersected in an oblique line midway along the tentacular club as shown in Fig. 3a. Other important features of the tentacular club include: 1. The relative sizes of the suckers: they may vary in size (Fig. 3a, c), or be of similar size (Fig. 3b); 2. The protective membranes may be joined at the posterior end of the sucker-bearing face of the club (Fig. 3a, c), or not joined (Fig. 3b); 3. The swimming keel may extend beyond the sucker-bearing face of the club (Fig. 3c), or may be equivalent in length to the sucker-bearing face; 4. The sucker-bearing face may be joined to the tentacle stalk (Fig. 3b), or may be separated from it by a membrane (Fig. 3c). Suckers are described as normal or normal-sized if they do not differ obviously in size from other suckers. As for club suckers, arm sucker “rows” refer to suckers positioned in transverse rows, that is, positioned in oblique lines approximately perpendicular to the longitudinal axis of the arm. “Series” refers to suckers positioned approximately parallel to the longitudinal axis of the arm. Biserial suckers are those arranged in 2 series, tetraserial are those arranged in 4 series. The cuttlebone (Fig. 4) can easily be removed from a fresh animal by making a median longitudinal incision along the length of the mantle, and two shorter incisions at the anterior end of the mantle as shown in Fig. 6. The skin can then be peeled open to reveal the cuttlebone below. Aside from its shape, important features of the cuttlebone include: 1. The width of the outer cone: it may broaden posteriorly (Fig. 4a, b), or be of approximately uniform width along the length of the cuttlebone (Fig.