|Checklist of the Collembola: Physiology|
Frans Janssens, Department of Biology, University of Antwerp, Antwerp, B-2020, Belgium
Newly hatched Collembola are pale,
except in well pigmented species, in which the ocular patches are coloured;
the freshly hatched animal remains immobile for a while before starting with
its active life
Several ecdyses are passed through before
full growth is attained, but the changes involve no important differences
between the young and the adult. They mainly consist of an increase in size
and in pigmentation, and a further differentiation of the joints of the
antennae and furca (Imms, 1948:231-232).
In Hypogastruridae, the morphological differences between juvenile and adult
instars are mainly the sensilla of the apical antennal segment, the body
size and pigmentation and the genital plate; in addition, the chaetotaxy
in juveniles is more simple than in adults (Thibaud, 1970:146-147).
Moulting cycle. After each ecdysis, a postexuvial feeding period is followed by a preexuvial fasting period (Humbert, 1979:52). In the postexuvial stage, the intestinal peritrophic membrane, the endocuticle and moulting granules are secreted; in the preexuvial stage, the new intestinal epithelium is formed, and after apolysis, moulting granules and haemocytes migrate to the exuvial fluid, the epicuticle and exocuticle is secreted; just before ecdysis the old intestinal epithelium is rejected (Humbert, 1979:52-53).
The maximal number of instars untill death can be very large, such as 50 in Orchesella (Schaller, 1970 cited from Blancquaert & Mertens, 1979:128), although in Symphypleona maximum 10 are found (Blancquaert & Mertens, 1979:128). In Hypogastruridae, sexual maturity (first ovipostion in females or first spermatophore depostion in males) is reached at the age of 1.5-3.5 months (5th to 7th instar) (Thibaud, 1970:123-124,132). Sexual maturity is reached at the third instar in Megalothorax (Blancquaert & Mertens, 1979:128) up to the eigth instar in Folsomia (Agrell, 1948 cited from Blancquaert & Mertens, 1979:128). The maximum life span is about 32 days in Sminthurinus up to 270 days in Orchesella (Blancquaert & Mertens, 1979:128). In Hypogastruridae, the longevity is about 6-18 months (Thibaud, 1970:123). In Hypogastruridae, the life cycle (egg to egg) is about 2-5 months (Thibaud, 1970:123-124).
Number of generations per year. To be completed.
Respiration. Respiratory movements are lacking Lubbock (1873:78). To be completed.
Reproduction. In Hypogastruridae, sexual dimorphism does not occur (Thibaud, 1979:124). The sperm is ejaculated from a simple genital opening (see fig.2) in a spermatophore (Hopkin 1997:134). A parthogenetic reproduction occurs in Megalothorax (Blancquaert & Mertens, 1979:127). In Hypogastruridae, eggs are deposited on the substrate in batches of 30 eggs; a female has 2-6 batches during her lifetime (Thibaud, 1970:128). To be completed.
Many Hypogastruridae live in the narrow spaces available in litter,
between stones, in the soil: they behave positively thigmotactic
Hypogastruridae behave negatively phototactic
The intertidal Anurida maritima has an endogenous tidal rhythm of
positive and negative phototaxis (Manica & al., 2000:371).
Exuviation. In Hypogastruridae, the exuviation takes about 20-45 minutes; before it begins, the animal becomes totally immobile; the new cuticle is already formed; the old cuticle is detached from the new cuticle, giving the animal a blown-up appearance with a whitish colour; the body takes a dorsally convex pose; medio-dorsally a longitudinal suture opens starting at the head capsule and progressing backwards due to the pulsating contractions and extensions of the body, releasing respectively the head, the thorax and the abdomen; after freeing itself from the exuvy, the animal rests for about 15 minutes before starting to walk; the exuvy is never ingested (Thibaud, 1970:148).
To be completed.
Collembola can be classified in two groups based on the form of the mouth-parts.
Those possessing a well developed mandibular molar plate chew their food and are
probably vegetarian, while those without molar plate are suctorial and
(Macnamara, 1924 cited from Adams & Salmon, 1972:270).
The suctorial forms are fluid feeders
(Poole, 1959 cited from Adams & Salmon, 1972:270).
The suctorial forms can be classified in two groups based on the form of the
maxilla head: piercing and sucking, where the maxilla head is stylet-like,
and rasping and sucking, where both maxilla and mandibula heads are toothed
(Wolter, 1963 cited from Adams & Salmon, 1972:270).
No one has actually observed and described a sucking feeding process in Collembola.
Until an actual suction method of feeding is demonstrated, it is preferable
to avoid the term sucking
(Adams & Salmon, 1972:270-271).
In Hypogastruridae, the intermoult cycle can be divided into three periodes: 1. one day of fastening just after exuviation, 2. 7-11 days of feeding, 3. 4-6 days of fastening before the next exuviation (Thibaud, 1970:149).
Locomotion, Senses, Digestion, Excretion, Metabolism. To be completed.