Incomplete Molt Research Articles

Metamorphosis in the Cirripedia Rhizocephala and the homology of the kentrogon and trichogon

The Rhizocephala are considered to be monophyletic due to several synapomorphies in the ontogeny of the cndoparasitic phase. The various types of metamorphosis described in the Rhizocephala are discussed and compared to metamorphosis in the Cirripedia Thoracica and Acrothoracica. In males and females of the suborder Kentrogonida. the cyprid settles and metamorphoses into a new instar, in males the trichogen and in females the infective kentrogon. The kentrogon goes through yet another. incomplete moult associated with the development of the stylet. Within the three kentrogonidan families. the Iernaeodiscid‐peltogastrid type of kentrogon differs from the sacculinid type in the mode of attachment to the host. in the complexity of internal anatomy. in the position and penetration of the stylet, and in whether or not the cyprid carapace must be shed prior to penetration of the stylet. In the Akentrogonida metamorphosis never results in a new instar. Where observed (Clistosaccidae and Thompsoniidae). both male and female cyprids settle and penetrate into their substrate (female parasite or new host) with one of the antennules. Using the antennule as a syringe. male cyprids inject spermatogonia while female cyprids injects embryonic cells developing into an endoparasite. By comparison with metamorphosis in the Cirripedia Thoracica and Acrothoracica it is concluded that the presence of a metamorphic moult leading to a post‐cyprid instar is plesiomorphic and that the trichogon and kentrogon are homologous with the first metamorphosed juvenile in these outgroups. The abbreviated ontogeny in the Akentrogonida without metamorphic moult and post‐cyprid larval instars is considered apomorphic. This contradicts the long‐held supposition that the Akentrogonida are the most‘primitive’Rhizocephala and dovetails with new information that this suborder contains many advanced traits. Within the Kentrogonida. the lernacodiseid‐peltogastrid type of kentrogon is considered more plesiomorphic than the sacculinid type, which resembles the clistosaccidthompsoniid type in having the antennules involved in the penetration process. The homologization of the kentrogon with a juvenile barnacle indicates that presence of a kentrogon is plesiomorphic within the Rhizocephala and that the Kentrogonida is paraphyletic.

Control of Spodoptera spp. using ULV formulations of the acylurea insect growth regulator, flufenoxuron: Field studies with Spodoptera exempta and effect of toxicant concentration on contact activity

AbstractField trials in Kenya showed that an ultra‐low‐volume (ULV) application of flufenoxuron (25 g a.i. litre−1; 1–0 litre ha−1) gave consistently good control of late‐instar larvae (L4‐L6) of the armyworm, Spodoptera exempta Walk. Flufenoxuron gave equivalent or greater control of S. exempta than did cypermethrin (24 g a.i. litre−1; 1–0 litre ha−1) from 96 h after ULV application. While initial (24–48 h) levels of larval mortality were greater with cypermethrin, many larvae treated with flufenoxuron showed signs of incomplete moulting after 48–72 h and would have been unable to feed normally. Laboratory spray bioassays with L3 Spodoptera littoralis suggested that the ULV formulation of flufenoxuron was most active at 25 g a.i. litre−1 when compared with higher (50 g) or lower (6.25 and 12.5 g a.i. litre−1) rates. Topical application studies with ULV formulations containing [14C]flufenoxuron showed that the accumulation of pesticide by L3 S. exempta over 1–4 h was consistently greater in larvae treated with 25 g than with 12.5 g flufenoxuron litre−1 and while initially lower, accumulation of pesticide appeared to be greater in larvae treated with 25 g than with 50 g flufenoxuron litre−1 after 2–4 h. The potential of ULV formulations of flufenoxuron for control of S. exempta is discussed.

The life history of Labiostrongylus eugenii, a nematode parasite of the Kangaroo Island Wallaby ( Macropus eugenii): Development and hatching of the egg and the freeliving stages

Smales L. R. The life history of Labiostrongylus eugenii, a nematode parasite of the Kangaroo Island Wallaby ( Macropus eugenii): development and hatching of the egg and the free living stages. International Journal for Parasitology 7: 449–456. Labiostrongylus eugenii (Trichonematidae) occurs in the stomach of the Kangaroo Island Wallaby. Egg morphology is similar to that of other strongyloids. When incubated at 25°C embryogenesis is completed in about 30 h. An incomplete moult occurs within the egg, and larvae hatch at a sheathed second-stage 43 1 2 –83 1 2 h later. Development occurred at all temperatures between 2° and 37°C with an optimum about 25°C and an upper limit near 37°C. The hatching process is very rapid, taking about 2 min. It is signalled by increased larval activity followed by a change in shell permeability. The larva hatches at that pole of the shell which has become plastic. The sheathed second-stage larva measures 659.50 ± 22.54 μm by 27.98 ± 1.22 μm. Its internal structures are concealed by a mass of opaque granules which were demonstrated as neutral lipid by oil red O staining. A second incomplete moult at 3–4 days results in a doubly sheathed infective larva from which the lipid gradually disappears. The mouth never appears patent and the larvae neither feed nor grow but rather decrease in size with age. Optimal temperatures for larvae range between 15°–25°C with 37°C about the upper limit. The significance of this developmental pattern is discussed.

STUDIES ON THE IN VITRO AXENIC DEVELOPMENT OF TRICHINELLA SPIRALIS. I. BASIC CULTURE TECHNIQUES, PATTERN OF DEVELOPMENT, AND THE EFFECTS OF THE GASEOUS PHASE.

Trichinella spiralis larvae from rat muscles were cultured axenically in roller tubes. In chick embryo extract and rabbit serum medium, male and female external genitalia appeared after the second incomplete molt. Molting was preceded by cuticular swelling around the neck, followed by constriction and ultimate rupture. The worms did not increase in size. Digestive enzymes and bile salts did not promote exsheathment and were often toxic. With added vitamins, the second molt was reached after 24 hours in vitro (as against 48 hours in the basic medium), but amino acids and glucose had no effect on survival and development. Under nitrogen or 5% CO2 in nitrogen the worms survived longer than in the presence of 5% oxygen or under air. Development was better in the presence of 5% CO2 than under 5% oxygen, and still better under higher CO2 tensions. Because CO2 tension in the mammalian intestine is often high, this gas and (or) carbonic acid probably play an important part in the biology of intestinal parasites. The two incomplete molts represent advancement through two stages and the worms with external genitalia are believed to be immature adults (that is, fifth stage). Because direct microscopic evidence of molting prior to encapsulation in muscles of infected animals has been obtained, the infective larvae are believed to be in the third stage.

Incomplete moulting caused by inadequate feeding and some remarks on the relation between nutrition and moulting

Incomplete moulting caused by inadequate feeding and some remarks on the relation between nutrition and moulting