INVERTEBRATE ZOOLOGY - H. I. Shcherbak - 2008

KINGDOM MULTICELLULAR ANIMALS (METAZOA)

SUBKINGDOM TRUE MULTICELLULAR ANIMALS (EUMETAZOA)

SECTION TRIPLOBLASTIC (TRIPLOBLASTICA) OR BILATERAL (BILATERIA) ANIMALS

SUBSECTION MOLTING ANIMALS (ECDYSOZOA)

PHYLUM ARTHROPODS (ARTHROPODA)

SUBPHYLUM TRACHEATES (TRACHEATA)

SUPERCLASS MYRIAPODS (MYRIAPODA)

CLASS CENTIPEDES (CHILOPODA)

Centipedes, like other myriapods, lead a secretive lifestyle; they inhabit soil, leaf litter, decaying wood, and under stones, though some species can spend considerable time in Water. All centipedes are exclusively predatory. Over 3,000 species have been described, with no more than 50 known in Ukraine.

Centipede sizes range from a few millimeters to 26.5 cm (Scolopendra gigantea). They are most often yellowish or brown in color, although greenish and even bluish specimens occur among scolopendromorphs.

Morphology. The body is dorsoventrally flattened and divided into a clearly differentiated HEAD and a segmented trunk. The head cuticle forms a head capsule. The head bears a pair of bead-like antennae and simple or compound eyes (sometimes absent). On the lower

side of the head are a pair of mandibles and two pairs of complex maxillae. The mouthparts also include the first pair of trunk appendages, which have transformed into poison claws (forcipules) (Fig. 346). Each of these ends in a sickle-shaped claw near the tip of which the duct of the venom gland opens. The poison claws are involved in capturing and subduing prey, as well as in defense against enemies.

The trunk may consist of 15 to 180 more or less homonomous segments. All trunk segments except the last two bear a pair of walking legs. As a rule, the posterior legs are the longest; the ultimate pair primarily performs a sensory function, helping centipedes navigate narrow crevices both forward and backward.

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Fig. 346. Head of the stone centipede Lithobius forficatus from the ventral side (from Füller):

1 - antenna; 2 - Mandible; 3 - first Maxilla; 4 - trunk leg; 5 - poison claw (forcipule); 6 - second maxilla

Integument. The sclerotization of the integument in different body regions of centipedes varies, but all lack the epicuticular wax layer, making centipedes highly dependent on environmental moisture. The cuticle is most heavily sclerotized on the head, the posterior end of the body, and the appendages.

The Muscular System partially retains features of a Skin-Muscle sac: in some groups (geophilomorphs, scolopendromorphs), a partial continuous layer of circular and longitudinal Muscles is preserved, but longitudinal muscles are often broken down into bundles running from one segment to the next or to subsequent ones; dorsoventral and pleurosternal bands are also present. Trunk muscles, together with appendage muscles, participate in locomotion.

Digestive System. The Mouth opening is located on the ventral side of the head, flanked laterally by sickle-shaped mandibles and ventrally by the first maxillae. The second pair of maxillae does not directly participate in food fragmentation and is used solely to hold prey. The digestive system is a straight tube (Fig. 347, a), which varies among species only in the relative length of its three regions. Salivary Glands are part of the digestive system; there may be three to five pairs, with their ducts opening into the Oral Cavity or onto the second pair of maxillae. Centipedes are predators characterized by extra-intestinal Digestion. Using their poison claws, they pierce the prey, inject venom along with saliva into the wound, and then suck out the semi-digested Contents of the prey.

Fig. 347. Internal Organs of centipedes (from Dogiel):

a - digestive System of the stone centipede Lithobius forficatus; b, c - male and female reproductive systems, respectively

1 - Esophagus; 2 - salivary gland; 3 - Malpighian tubule; 4 - anus; 5 - hindgut; 6 - midgut; 7 - Testis; 8 - Seminal Vesicle;

9 - accessory gland; 10 - ejaculatory duct; 11 - paired part of the vas deferens; 12 - Ovary; 13 - seminal receptacle;

14 - gonopod; 15 - genital aperture; 16, 17 - paired and unpaired PARTS OF THE oviduct, respectively

The excretory system is represented by a pair of Malpighian tubules. In centipedes of the orders Lithobiomorpha and Scutigeromorpha, There are also maxillary organs resembling the excretory organs of crustaceans.

The Circulatory system is well developed. The Heart is elongated and consists of multiple chambers corresponding to the number of trunk segments; each chamber has two lateral openings (ostia), and it is blindly closed at the posterior end. Anteriorly, the heart continues into the main aorta, which extends to the Brain; an arterial ring branches off the sides of the aorta, loops around the gut, and empties into the ventral vessel. Aside from the ostia leading to the pericardial cavity, each heart chamber gives rise to two lateral Arteries. These arteries branch extensively, pouring hemolymph into the lacunae of the mixocoel, from which it returns to the pericardial cavity and re-enters the heart through the ostia. Blood flows through the cardiac vessel from the posterior end to the anterior, and in the reverse direction through the ventral vessel.

Respiratory system. The Structure of the tracheal system varies somewhat among different orders, but it is well developed in all of them. The tracheae are highly branched, and there are interconnections between the tracheal bundles of adjacent segments.

The Nervous system has a typical arthropod structure, consisting of a brain, circumesophageal connectives, a subesophageal ganglion, and a ventral nerve cord.

Sense Organs. In chilopods, antennae are associated with the Senses of Touch and smell. Simple ocelli are present on the sides of the head, numbering from two to four up to large clusters resembling the compound eyes of insects.

Reproductive System. The Gonads are unpaired and located above the gut in both sexes. The genital ducts (vas deferens and oviduct) bifurcate, looping around the intestine, and reconnect beneath it. Two pairs of accessory glands empty into the unpaired parts of the ducts (Fig. 347, b, c). Connected to the male vas deferens are two sac-like Seminal Vesicles and a pair of seminal receptacles. The genital aperture in both sexes is located on the penultimate segment.

Reproduction. Fertilization is via spermatophores. Postembryonic development occurs in two ways: epimorphic (Geophilus, Scolopendra) and anamorphic (in all others). In the latter case, the animal hatches without the full Complement of segments, and their number increases during molting. Parental care is well developed in many species.

The following orders of chilopods are quite widespread, including in Ukraine.

Order Geophilomorpha (Geophilomorphs) are found under fallen leaves, stones, tree bark, etc., but as their name implies, they most frequently inhabit the soil, where they live and hunt various invertebrates. They possess a thin, elongated, sometimes ribbon-like body with numerous trunk segments (from 31 to 173). Body length ranges from 1–4 cm, though some species are longer, such as the thermophilic *Himantarium barbarum*, which reaches up to 22 cm. The presence of a well-developed cutaneous-muscular sac allows geophilomorphs to move similarly to earthworms, enabling them not only to crawl through existing soil burrows and crevices but also to excavate their own. Geophilomorphs prey on earthworms—which are frequently much larger than the predators themselves—as well as numerous insect larvae, while the species *Scolioplanes acuminatus* prefers heavily sclerotized millipedes.

Certain geophilomorph species, such as *Scolioplanes maritimus*, become true marine shore dwellers, colonizing rocky intertidal zones where they hunt Mollusks, various crustaceans, and other small animals.

Order Lithobiomorpha (Stone centipedes) typically inhabit forest litter and herbaceous plant debris in meadows and steppes; they can also be found beneath tree bark and in moss. Many species live near water or in caves. Lithobiomorphs have a shorter trunk consisting of 18 segments with 15 pairs of relatively long legs. Their size ranges from 3 to 51 mm (in *Polybothrus fasciatus*). Their coloration varies from yellowish to brown, featuring one to three longitudinal stripes on the dorsal side. Stone centipedes are agile runners. At night, they hunt various small insects, spiders, etc. Additionally, they ambush prey in shelters where the victims themselves hide from sunlight. The most widespread species in the fauna of Ukraine, *Lithobius forficatus* (Fig. 348, a), is frequently encountered near human habitation, including urban areas.

Fig. 348. Chilopods (after Dogiel):

a — stone centipede Lithobius forficatus; b — centipede Scolopendra angulata; c — house centipede Scutigera coleoptrata

Order Scolopendromorpha (Scolopendrid centipedes) are the largest of the chilopods. As previously mentioned, *Scolopendra gigantea* reaches a length of 26.5 cm. The trunk consists of 25 segments with 21 pairs of legs (Fig. 348, b). The legs are well developed, enabling the animals to run rapidly. The posterior pair of legs has a specialized structure: they are hook-shaped, heavily thickened, and often bear long, stylet-like processes. This serves as an organ for capturing prey and defending against enemies; furthermore, the centipede uses its rear legs to anchor firmly to the substrate when subduing large prey.

Scolopendrid centipedes inhabit spaces beneath large, flat stones, where they construct horizontal passageways and excavate fairly large, rounded chambers for shelter. Like geophilomorphs, they achieve movement through the antagonistic contraction of circular and longitudinal muscles. They prey on earthworms, insect larvae, and other invertebrates. Large species, such as *Scolopendra gigantea*, attack small birds, lizards, and frogs. In addition to animal prey, they consume succulent fruits.

Order Scutigeromorpha (House centipedes) inhabit the tropical and subtropical Zones of the Earth. The fauna of Ukraine is represented by a single species, the house centipede (*Scutigera coleoptrata*), which is found on the southern coast of Crimea and the Northern Black Sea region, and is currently listed in the Red Book of Ukraine. Scutigeromorphs live in rock crevices, under stones, in coniferous and deciduous leaf litter, and in various shelters, including human buildings. Their size is small, ranging from 2.5 to 4.5 cm. They possess exceptionally long legs and are capable of swift running (Fig. 348, c).

Unlike other chilopods, which lead a secretive, nocturnal or crepuscular lifestyle, house centipedes hunt during the day. They move with extreme rapidity—almost blindingly fast (50 cm/s)—across open surfaces, including the walls of buildings, preying on various Arthropods, particularly insects and spiders, which explains their common name.