Pair Of Pereiopods Research Articles

Structure and function of the chelate pereiopods of the banana prawn Penaeus merguiensis

Penaeus merguiensis de Man systematically searches the substratum and removes small particles of food from it using the small chelae of the first three pairs of pereiopods. One or more chelae are used to transfer food particles to the mouth. The propus and dactylus of these limbs bear numerous setae arranged in discrete groups along the length of the segments. The tip of each seta is elaborately sculptured and has a large sub-terminal pore. It is probable that these are chemosensory organs responsible for discriminating edible from non-edible material. Proximal to almost every setal group is a much-branched seta (rarely two) which probably measures the depth to which the chela has been inserted into the substratum. At the articulation of the propus and carpus of the first pereiopod are three groups of differently sculptured setae, whose function is to clean the other chelate pereiopods. An elaborate system of pegs and a ridge on the apposable fringes of the chelae might be a mechano-receptive device with a particle size discriminating function. The ridges merge into opposable terminal denticulate pads whose function is to grasp food and other particles, which may be quite small (10 to 20 μm upwards).

Manifestation d'un comportement territorial chez les crevettes pontoniinae associées aux mollusques pinnidae a tuléar (Madagascar)

Shrimps associated with molluscs are generally found in pairs in their host and observations show that this disposition leads to active competition, both intra- (between individuals of same sex) and interspecific. The territory in dispute is the entire palliai ensemble of the mollusc. The weapons are the second pair of pereiopods and their size is of prime importance in determining the outcome of any encounter. In interspecific confrontations, Paranchistus ornatus Holthuis is regularly expelled by Anchistus custos (Forskål), and Conchodytes biunguiculatus (Paulson) will displace both of these species.

The Effects of Temperature on the Development of Limnoria Eggs (Isopoda: Crustacea)

The study of the reproduction of marine invertebrates in relation to temperature has acquired an added interest in recent years because of the increasing number of electrical generating stations and other industrial plants that are being built on the shores of estuaries. The biological significance of these installations lies in the use of large volumes of sea water in their cooling systems. The water is heated in the process and discharged back into the sea at temperatures as much as 200 C above ambient. The effects of warm water effluents on marine life have been reviewed by Naylor (1965) who gives examples of the amounts of heat produced. Increased temperature may be expected to influence the reproductive processes and this paper is concerned with the effects of temperature changes on one reproductive aspect-egg development-of the gribble (Limnoria), a marine, wood-boring isopod. In view of the destructive habits of Limnoria, the matter is of some economic importance. There are three species of Limnoria in British watersL. (L.) lignorum (Rathke), L. (L.) quadripunctata Holthuis and L. (L.) tripunctata Menzies. Their distributions are given by Jones (1963). It has been found that warm water effluents can increase Limnoria damage in a number of ways. In the first place, the rise in temperature may stimulate the general boring activity and cause it to be continued into the normally quiescent winter months (Beckman & Menzies 1960; Eltringham 1965). Secondly, it may accelerate the onset of the breeding season in the spring and prolong its duration into the autumn and winter (Hockley 1963). Finally, it may shorten the developmental period of the young stages and thus permit the production of a larger number of broods each breeding season. Not much is known about this aspect. S0mme (1941) found that under conditions rising from 11 to 160 C, the eggs of L. lignorum took from 33 to 42 days to reach the stage at which the young forms leave the pouch. (The eggs develop within a brood pouch which is formed from the expanded epipodites (obstegites) of the second to fifth pair of pereiopods.) The only other published study appears to be that of Kampf (1957) who found that in L. tripunctata the total developmental time was 17 days at 200 C, 15 days at 220 C, 13 days at 260 C and 11 days at 300 C. Although the developmental time was accelerated by increased temperature, the percentage of eggs that reached the 'hatching' stage was reduced, e.g. .85%0 completed development at 200 C but only 51%0 at 300 C. Although these results are of great interest, it was clear that much remained to be learnt about the development of eggs in relation to temperature. One of the most important aspects, about which nothing is known, is the values of the limiting temperatures, both upper and lower, for successful development. Nor have the durations of the separate *stages through which the embryos pass been fully investigated, although Somme (1941) recorded those of a few eggs which had been extruded from the pouch by the movements of the female. The work to be described was carried out with eggs removed from the brood pouch and reared under constant temperature conditions in natural sea water of 33%, salinity.

Records of Macrobrachium carcinus (Linnaeus) and Macrobrachium acanthurus (Wiegmann), from Santa Catarina, Brazil

AMONG unidentified material kept at the Fish and Wildlife Service Laboratory at Florianopolis, capital of the State of Santa Catarina, were several specimens of the freshwater prawn Macrobrachium. These were identified as M. carcinus and M. acanthurus. The two specimens of M. carcinus, of 200 and 210 mm total length (excluding the second pair of pereiopods, which measured 230 mm), were from Lagoa da Conceicao, a brackish to freshwater lagoon on the Santa Catarina Island. The eight specimens of M. acanthurus of 80–140 mm total length (excluding the second pair of pereiopods, which measured up to 120 mm in length), were from Rio Pinheira (27° 50′ S.), a small river on the mainland, about 3 miles south of the southernmost tip of S. Catarina Island. Local fishermen stated that M. carcinus had occasionally been taken from Rio Pinheira, but this could not be verified.

The Biology ofCrangon VulgarisL. in the Bristol Channel and Severn Estuary

Collections of some 22,000 female and 6000 male Crangon vulgaris were made throughout the year from the shrimp fisheries of the Severn Estuary and Bristol Channel. All animals were measured.The habits of the species are described; it can withstand a wide range of temperature but, though euryhaline, resembles other Decapoda in the inability to withstand low salinity combined with low temperature.Osmo-regulation is apparently largely inhibited at low temperatures and to a greater extent in the males than the females.Growth rate decreases with increasing age; in the female there is no increase in length when moulting from the ' neuter' to the egg-carrying intermoult. The duration of this intermoult, if spawning is successful, is about double that of the normal intermoult under the same temperature conditions. Growth almost ceases in the winter.Secondary sexual characters are described, especially the differences between the endopodites of the pleopods in the two sexes.Females become mature at a minimum length of 45 mm. in the Channel and seldom less than 50 mm. in the Estuary. The effect of the female sexual cycle on the size of the ovary and the form of the pleopods is described. The process of copulation is described; it can occur in the brackish waters of the estuary. Egg-laying always follows within two days of moulting into the egg-carrying condition but eggs are not retained if copulation has not occurred.The females lie on their sides during the act of spawning and the eggs are firmly attached within thirty minutes to the egg-carrying setae on the basipodites of the first to fourth pair of pleopods, then to those on the endopodite of the first pleopod, finally to those on the coxopodites of the last two pairs of pereiopods.