Advanced Larval Stages Research Articles

Larval development and the formation of the gut ofSiboglinum poseidoniFlügel & Langhof (Pogonophora, Perviata). Evidence of protostomian affinity

Abstract Larvae of Siboglinum poseidoni were reared in the laboratory. About 6 weeks after recovery from the central Skagerrak the larvae develop a small tentacular bud. On the opposite side a stomodaeum is formed. Electron microscopy of suitable sections shortly in front of the tentacular bud reveals a ciliated opening and tract. In the trunk this tract is reduced to a small tube by bulging endoderm cells containing large amounts of yolk. The lumen is obscured by densely packed cilia. In more advanced stages extracellular symbiotic bacteria occur within this transient digestive tract. They appear to be taken in via the transient mouth. As development progresses the mouth and ciliated foregut close. In the trunk of adult specimens the space between the dorsal and the ventral vessel is occupied by bacteriocytes forming the trophosome. The lumen ofthe digestive tract is reduced to small ciliated spaces. The tentacle develops opposite to the transient mouth and hence dorsally, while the main nerve trunk is ventral. More advanced larval stages closely resemble an elongated annelidian metatrochophora. A relationship between Vestimentifera (Obturata) and Pogonophora (Perviata) is confirmed and the placement of both groups within the phylum Annelida suggested.

Behavioural plasticity in the stinging act of female ectoparasitoids

Abstract. The plasticity of the stinging behaviour of female Eupelmidae (Eupelmus vuilleti Crawford, E. orientalis Crawford Hymenoptera: Eupelmidae) was analysed through the interrelationships of a parasitic community living on larval stage of Callosobruchus maculatus Fabricius (Coleoptera: Bruchidae). In traditional African grainstores, Eupelmus females have at their disposal all the larval stages of their host. Their exploitation is revealed by the sting observed on the host caused by the ovipositor of parasitoid females. This stinging behaviour begins immediately on the adult female's emergence, and thereafter there is a daily increase in the number of hosts stung. Stinging activity is linked to the age of the available hosts, but not all of the hosts available are exploited by the two species studied. This absence of total exploitation could indicate a threshold of activity in the stinging acts which could be in part linked to the secretion activity of the poison glands of parasitoid female.In females of E. vuilleti and E.orientalis the stinging act is usually associated with egg‐laying. The relationship between stinging and egg‐laying is stronger in more advanced larval stages of the host.In the presence of parasitized hosts, females of E. orientalis and E.vuilleti can exhibit hyperparasitism. The majority of larvae (i.e. primary parasitoid) that have been hyperparasitized have been stung and a large number of them are completely inactive. However, E. vuilleti females deposited their eggs in the available space of the pupation chamber of the host. The neonatal larvae from these scattered eggs could exploit any available host without the female having ‘prepared the ground’ at the time of egg‐laying.In Eupelmidae, all this happens as if there were a complementary action between the females and the neonate which could, if necessary, reinforce and/or compensate for the deficiencies in the host exploitation by the female.

Interannual variations of lipids and fatty acids during larval development of Crangon spp. in the German Bight, North Sea

Eggs and larval stages of the caridean shrimps Crangon crangon and C. allmanni were collected to determine their lipid and fatty acid compositions. Specimens were sampled after the extremely mild winter of 1989/1990 and during the following year, 1991. The fatty acid composition of the zoeal stages of both C. crangon and C. allmanni from 1991 were predominated by the polyunsaturated fatty acids which are typical for marine organisms. In contrast, unsaturated fatty acids were absent in the early larval stages of C. crangon collected in 1990; however, advanced larval stages showed a similar fatty acid composition compared to larvae from 1991. The major phospholipid of eggs and larvae was phosphatidylethanolamine. Eggs contained also phosphatidylcholine and phosphatidylserine, which are probably utilized during embryonic development until hatching because in the early larval stages, only phosphatidylethanolamine was found. In stage VII, again phosphatidylcholine and phosphatidylserine occurred. The lipid and fatty acid composition seems to be an indicator for the survival chances of the planktonic stages. The absence of unsaturated fatty acids may be interpreted as a consequence of unfavorable nutritional conditions during the early developmental phase of the shrimps.

Direct introduction of cloned DNA into the sea urchin zygote nucleus, and fate of injected DNA.

A method is described for microinjection of cloned DNA into the zygote nucleus of Lytechinus variegatus. Eggs of this species are unusually transparent, facilitating visual monitoring of the injection process. The initial fate of injected DNA fragments appears similar to that observed earlier for exogenous DNA injected into unfertilized egg cytoplasm. Thus after end-to-end ligation, it is replicated after a lag of several hours to an extent indicating that it probably participates in most of the later rounds of DNA synthesis undergone by the host cell genomes during cleavage. The different consequences of nuclear versus cytoplasmic injection are evident at advanced larval stages. Larvae descendant from eggs in which exogenous DNA was injected into the nuclei are four times more likely (32% versus 8%) to retain this DNA in cell lineages that replicate very extensively during larval growth, i.e. the lineages contributing to the imaginal rudiment, and thus to display greatly enhanced contents of the exogenous DNA. Similarly, 36% of postmetamorphic juveniles from a nuclear injection sample retained the exogenous DNA sequences, compared to 12% of juveniles from a cytoplasmic injection sample. However, the number of copies of the exogenous DNA sequences retained per average genome in postmetamorphic juveniles was usually less than 0.1 (range 0.05-50), and genome blot hybridizations indicate that these sequences are organized as integrated, randomly oriented, end-to-end molecular concatenates. It follows that only a small fraction of the cells of the average juvenile usually retains the exogenous sequences. Thus, even when introduced by nuclear microinjection, the stable incorporation of exogenous DNA in the embryo occurs in a mosaic fashion, although in many recipients the DNA enters a wider range of cell lineages than is typical after cytoplasmic injection. Nuclear injection would probably be the route of choice for studies of exogenous DNA function in the postembryonic larval rudiment.

Acetylcholinesterase activity in embryonic and larval development of Artemia salina leach (crustacea phyllopoda)

AbstractAcetylcholinesterase (AChE) activity has been studied in Artemia salina embryos and larvae by quantitative, histochemical, and electrophoretic methods. An AChE activity is present in dehydrated encysted gastrulae and remains low in rehydrated developing embryos, showing at hatching an increase that becomes faster during the nauplius stages (twice the gastrula activity at the nauplius II stage), and continues linearly in the first metanauplius stages. The histochemical staining, faint and diffuse in dehydrated gastrulae, in more advanced embryos becomes localized in cell membranes and stronger in differentiating tissues; most AChE activity is localized in the nervous and muscular cells, and a fainter one in the differentiating metanauplius segments. Dehydrated cysts show one electrophoretic AChE band, that is no longer detectable in rehydrated embryos and larvae, while two other bands appear, that migrate more slowly; in advanced larval stages, the more cathodic band is predominant. In dehydrated cysts, isoelectric focusing separates three AChE bands with isoelectric points (IP) at pH 5.0, 5.7, and 5.9; in hydrated embryos and larvae, the band at pH 5.0 is absent and another is seen at pH 5.5. Eserine, DFP, and BW284c51 inhibit the enzyme activity strongly and cause paralysis of larvae; also tubocurarine blocks the motility. These results are discussed in relation to the differentiation of the neuromuscular system and to the development of motility. As a hypothesis, in early embryonic stages, before any neuromuscular differentiation is evident, a cholinergic‐like system might regulate non‐neural cell activities and interactions, associated with embryogenetic events.

Long-term effects of water-soluble fractions of Kuwait crude oil on the larval and juvenile development of the mud crab Eurypanopeus depressus

Larvae of the mud crab Eurypanopeus depressus (Smith) were reared in various concentrations of the water-soluble fraction of Kuwait crude oil. The 48-h TLm (median tolerance limit) for Zoea Stage I was approximately 10 ppm total dissolved hydrocarbons and that for Zoea Stage II approximately 17 ppm. Chronic toxicity of more dilute solutions (4.3 and 8.7 ppm) was assessed independently for each larval stage and for subsequent developmental stages through Crab Stage 5. In the group continuously exposed to oil from hatching, there was differential mortality relative to controls in every larval stage and increased duration of intermolt periods was observed at every stage through Crab Stage 5. Mortality in groups not exposed until larvae had reached Zoea Stages III or IV was not greater than controls, suggesting that toxicity to advanced larval stages may be related to accumulation of toxic compounds by the larvae. Neither concentration (4.3 or 8.7 ppm) of crude oil caused increased mortality among juvenile crab stages regardless of the time of initial exposure. Increased occurrence of an extra and morphologically abnormal megalopa stage was associated with exposure to the crude oil. This has not been reported before.

The Broods of British Mysidacea (Crustacea)

All species of the Mysidacea (Crustacea) lay their eggs into a marsupium, thus allowing direct counts of brood sizes to be made. The different forms of the young stages in the marsupium are closely similar in all species. The most detailed embryological studies are those of Manton (1928) on Hemimysis lamornae (Couch), Wagner (1896) and Needham (1937) on Neomysis integer (Leach), and Nair (1939) on the tropical species Mesopodopsis orientalis (W. M. Tattersall). Kinne (1955) describes and figures the general body forms of the different stages of development of the larvae in the marsupium of Neomysis integer; Vannini (1930) examines the larvae of Leptomysis lingvura (G. O. Sars), while Kane (1904) illustrates the most advanced larval stage of Mysis relicta Lovén. The larvae of several non-British species have been described -Boreomysis arctica (Kröyer) by Jepsen (1965), Mysidium columbiae (Zimmer) by Davis (1966) and Neomysis intermedia Czerniavsky by Murano (1964b).

Some Recent Advances and Unsolved Problems in the Culture of Marine Fish Larvae1

ABSTRACTSuccessful rearing of marine fish larvae depends on numerous factors, but a suitable food supply in conjunction with reasonably good water quality are the two factors that are of greatest importance. Most newly hatched marine fishes have mouths that are too small to begin feeding on Artemia sp. nauplii, but some copepod nauplii, rotifers, mollusk larvae, and dinoflagellates provide suitable food. Size of food organisms and the food level maintained in rearing tanks are important for initiation of feeding and for subsequent growth and survival. Optimum rearing temperatures need to be determined for each species to assure that growth is rapid during the larval stage. Both growth and survival of fish larvae are enhanced when a phytoplankton bloom is maintained in the rearing system. Larvae grow and survive better in large culture tanks than in smaller ones.Little is known about optimum stocking densities of eggs and larvae in rearing systems. Abnormal development of larvae is a common occurrence and can be attributed to stresses of the rearing tank environment. Diseases and parasites may affect survival of eggs and larvae. Energy relations have been determined for egg and yolk sac larvae but similar research is required on advanced larval stages. The variability in egg quality that will result from artificial spawning procedures will also be a factor affecting subsequent rearing attempts.

Dodecaceria berkeleyi n.sp., a Polychaete (Family Cirrutulidae) from New Zealand

The described species of the genus Dodecaceria are reviewed. Fourteen species are recognized and their diagnostic characters are given. A new species, Dodecaceria berkeleyi, is described from New Zealand where it is found boring in the shells of large gastropod molluscs. An outline is given of the nature of the skin pigments, which are similar to the arenicolochrome of lugworms. Asexual reproduction in the genus is reviewed, and an account is given of autotomy in D. berkeleyi, followed by regeneration to give rise to two individuals, a method of reproduction similar to that which occurs in the colonial tube builder Dodecaceria fistulicola. An advanced larval stage found in the burrows of D. berkeleyi is described.

Ontogeny of the immune response to skin allografts in relation to lymphoid organ development in the amphibian Xenopus laevis Daudin

AbstractThe response of larval and adult Xenopus to first set skin allografts was studied by examination at regular intervals of the external appearance of the grafts and of serial sections through the graft region. Operations were performed on all stages of larvae ranging from those with rudimentary to those with mature lymphoid organs. Larvae received single allografts from either larval or adult donors, skin from the latter being a good morphological marker: adults received adult skin only. Control autografts were also applied to both larval and adult toads.All autografts were accepted; no incompatible phenomena were observed. Both adults and larvae, even those operated at the most immature stage of development, were able to repond immunologically to the skin allografts. The response was similar in larval and adult toads and included a lymphocytic invasion of the graft which disappeared when destruction of the graft was near completion. This invasion was correlated with the state of development of the lymphoid organs of the host: if these organs were immature at the time of application of the graft, the invasion was delayed but eventually occurred when the host reached a more advanced larval stage. The capacity to invade a graft with lymphocytes could be correlated with the lymphoid maturation of the thymus.These results support the view that the allotransplantation of tissues in immature amphibian larvae, before acquisition of immunological competence, does not necessarily preculude the possibility of an immune response to the same tissues in more mature larvae.

Localized Maturation of Lid-closure Reflex Mechanism by Thyroid Implants into Tadpole Hindbrain.

The lid-closure (wink) reflex of amphibians—retraction of the eye bulb upon tactile stimulation of the cornea or surrounding skin—appears comparatively late in development. Urodeles display it first in advanced larval stages, anurans at or about the time of metamorphic climax. In the latter group its dependence upon the metamorphosing agents was demonstrated by experiments in which metamorphosis was either suppressed (hypophysectomy) or advanced (hyperthyroidism);1 in the former case, the reflex failed to appear unless thyroid was administered, while in the latter case its onset was advanced almost, though not fully, as much as was the transformation of the body. Both the sensory (trigeminal) and motor (abducens) components of the reflex develop full functional capacity in very early larval stages, but their central linkage into a workable reflex mechanism is not effected until at the time of metamorphosis.The close association with metamorphosis suggested that maturation of the central mechanism of the r...