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PubMed1977

A layered rhabdom in an isopod (Crustacea). A case of convergent development.

The isopod species Astacilla longicornis (Sowerby) has a layered rhabdom, which is the first case reported in isopod crustaceans. The rhabdom comprises the rhabdomeres of six retinular cells. It is surrounded by an extracellular palisade. Usually, palisades are intracellular in arthropods. A layered rhabdom is found in taxonomically widely separated groups within the Arthropoda and no intermediate forms are found between the different, highly specialized rhabdom types present. It is concluded that the layered rhabdom represents an example of convergent development.

Animals↗
PubMed1982

[Neuroendocrine control of reproduction in Crustacea].

The neuroendocrine factors synthetized by various regions of the nervous system and which have inhibiting or stimulating effects can control the male and female physiology of malacostraca via sexual hormones and moulting hormone. There are between decapods and peracarids functional homologies but some differences can be noticed as to the localization of these antagonistic neurosecretory systems. The functioning of these systems is regulated by external factors such as the photoperiod and the temperature. The interactions between these different neurohormones, the sexual hormones and the moulting hormone are discussed.

Animals↗
PubMed1982

[Some aspects of hormonal interactions between molting and vitellogenesis in Orchestia gammarellus (Pallas) (Crustacea, Amphipoda)].

The mechanisms which coordinate and regulate secondary vitellogenesis and molting in Orchestia gammarellus have been studied in natural and experimental conditions. The onset of secondary vitellogenesis, requiring a protocerebral factor and a low titer of ecdysteroids, occurs only after normal folliculogenesis. The secondary follicular tissue would secrete vitellogenin stimulating ovarian hormone (VSOH) which stimulates the subepidermal adipose tissue to produce vitellogenin. VSOH and ecdysteroids are indispensable to normal vitellogenin synthesis during secondary vitellogenesis. Moreover, the Y-organ controls vitellogenin entry into the oocytes. In secondary vitellogenesis the ovary would stimulate the secretion of molt inhibiting hormone (MIH) which would act on the epidermis, rendering this tissue unresponsive to the stimulatory action of ecdysterone. The Y-organ and the protocerebrum are involved in the control of the molting processes independently of their action on vitellogenesis.

Animals↗
PubMed1981

Naturally occurring abnormalities (Bruchdreifachbildungen) in the chelae of three species of Crustacea (Decapoda) and a possible explanation.

Naturally occurring abnormalities (Bruchdreifachbildungen) in decapod crustacean appendages are described. They are similar to the range of structures experimentally produced by cutting notches in the sides of insect legs (Bohn, 1965). It is argued that they result from failure of wounds to heal. Regeneration from a free surface along the proximodistal axis is always in a distal direction. Surfaces regenerating circumferentially can regenerate in either direction around the circumference. Regeneration will proceed until the two surfaces of the wound meet. Then, where the two surfaces on either side are non-congruent, intervening tissues will be intercalated. This explanation accounts for the range of structures observed after notching experiments (Bohn, 1965) and seen in crustacean Bruchdreifachbildungen. The explanation says that regeneration will occur wherever wounds fail to heal. This avoids the difficulties of the complete circle rule (French, Bryant & Bryant, 1976) and explains why appendages with mirror-image symmetry are often capable of regeneration.

Animals↗
PubMed1981

Laboratory culture of Palaemon elegans (Rathke, 1837). (Crustacea decapoda) (third contribution).

A certain amount of Palaemon elegans larvae is bred in the laboratory under controlled conditions (at four different salty concentration rates). They were hatched from a number of egg laying females, which had previously been gathered along the Ligurian littoral. The larval development carried on for 25 to 30 days at an average temperature of ambient of 20 degree C during the seasonal period from May 23rd to June 23rd, 1980. Two hundreds out of the five hundreds larvae hatched from the eggs have been insulated and held for an adaptation period of about ten hours at the salinity of their home environment. Thus, the resistance of these froms to the salinity variations is evident. The results are confirmed by the biostatistical control.

Animals↗
PubMed1980

[Hormonal control of vitellogenin synthesis in the Amphipoda Crustacea Orchestia gammarella (Pallas)].

The presence of a vitellogenin stimulating ovarian hormone (VSOH) in Orchestia gammarella has been demonstrated by gonadectomy and ovary grafting. Vitellogenin synthesis is not affected by molting hormone injection; it decreases after Y-organ (molting gland) cauterization. Studies in progress seem to indicate that the destruction of the median area of the protocerebrum is followed by a decrease of this synthesis.

Animals↗
PubMedDate not supplied

[Esterase and amylase: two biochemical markers in the polytypic Idotea chelipes (crustacea, isopoda valvifera)].

In polytypic Idotea chelipes species, the slow esterase constitutes a subspecific biochemical marker which discriminates, without ambiguity, each of three subspecies. Amylase 2 is a diagnostic locus which separates I. chelipes bocqueti from the two other subspecies where each is characterized by particular frequencies of the most frequent allele. The analysed electrophoretic zymogram and the intersubspecific cross-breeding results attribute a monomeric structure for this enzyme which depends on diallelic gene.

Alleles↗
PubMed1978

[Septicemic infection by spore forming bacteria in Crustacea, Isotopa].

A new type of disease localized to haemolymph has been discovered and studied in the oniscoid Armadillidium granulatum. The infection is due to a bacterium showing particularities of shape, and sporulating form structures, of nutritional requirements and of very slow but lethal pathogenic effect in visceral cavity of isopods.

Animals↗