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The effects of 0.01, 0.1, 1.0 and 10.0 ppb mirex on the development of blue crabs,Callinectes sapidus, from hatching to first crab stage are described. None of the concentrations of mirex showed any appreciable effect on the larvae during the first five days. Thereafter 0.01 ppb and 0.1 ppb mirex were found to be sublethal. These concentrations had no effect on the duration of development from hatching to megalopa or from hatching to first crab stage. Concentrations of 1.0 ppb and 10.0 ppb mirex proved to be acute. No one stage of development was particularly sensitive to 0.01 ppb mirex, but in the other three concentrations some stages were more sensitive (statistically) than others. The results of residue analyses are given for larvae reared in four concentrations of mirex at different periods of development. Residues of mirex in developmental stages increased with concentration, but biological magnification was greatest in larvae reared in the lowest concentration of mirex and lowest in larvae reared in the highest concentration.

Laboratory experiments wer conducted to determine the effects of Kepone on the larval development of the mud-crab,Rhithropanopeus harrisii, and the commercial blue crab,Callinectes sapidus, from the time of hatching until the 1st crab stage was reached.

Survival of Rhithropanopeus harrisii larvae from hatching to first crab stage occurred in Na2CrO4 concentrations from 1.1 to 29.1 ppm. Estimated LC50 for complete zoeal development was 17.8 ppm Na2CrO4 and it was 13.7 ppm for development to first crab stage. A concentration of 1.1 ppm Na2CrO4 was nontoxic, while Na2CrO4 concentrations of 7.2 and 14.5 ppm were sublethal and concentrations of 29.1 to 58.1 ppm were acutely toxic. Low concentrations of Na2Cr04 caused an increase in swimming speed and high concentrations caused a decline.

Laboratory experiments were conducted to determine the effects of methoxychlor on the larval development of the mud-crab, Rhithropanopeus harrisii, and the commercial blue crab, Callinectes sapidus, from the time of hatching until the 1st crab stage was reached. The effect of a range of concentrations of methoxychlor on survival of larvae of C. sapidus and R. harrisii was determined, as well as the concentrations which were sublethal and lethal. Since concentrations as low as 1.3, 1.6 and 1.9 ppb (μg l−1) methoxychlor were acutely toxic to C. sapidus larvae, and it took a concentration as high as 7.0 ppb to be acutely toxic to R. harrisii larvae, it was concluded that C. sapidus larvae were much more sensitive to methoxychlor than R. harrisii larvae. Zoeal and total development to the 1st crab stage of R. harrisii and C. sapidus were prolonged in relation to increased concentrations of methoxychlor. The developmental stages in which larvae were particularly sensitive varied in the two species. Methoxychlor residues of R. harrisii and C. sapidus larvae reared in concentrations of methoxychlor were determined.

The complete larval development of the spider crab Mithrax (Mithrax) pleuracanthus from hatching to first crab stage was obtained by culture in the laboratory. A prezoea, two zoeal stages, and one megalopal stage are described and illustrated. Larvae were reared in 12 different combinations of temperature and salinity. Best survival to first crab stage occurred at 25°C and salinities of 30‰ and 35‰ and at cyclic temperatures of 30–35°C in 35‰ salinity. Development to first crab was 14 days (at 25°C) and 9-10 days (at 30°C, cyclic 30–-35°C). Morphological characters of M. pleuracanthus larvae were compared with those of two other members within the genus. The subgenera Mithraculus and Mithrax were originally based on only adult characters, but it is suggested that a reevaluation of these subgeneric diagnoses should be considered to include larval characters.

The mud aqueous fraction (MAF) and suspended particulate phase (SPP) of low-density lignosulfonate type mud with uerrochrome added were nontoxic to larvae during the complete larval development of Rhithropanopeus harrisii. Five percent (5000 ppm, 0.5 % v/v mud in water) MAF and SPP were not toxic to Callinectes sapidus. Survival of C. sapidus larvae decreased as concentrations of MAF and SPP increased from 5 % (5000 ppm, 0.5 v/v mud in water) to 50% (50000 ppm, 5 % v/v mud in water). No larvae reached the 1st crab stage in 100% (100000 ppm, 10% v/v mud in water) MAF and SPP. Statistical analysis of the data on survival, mortality, and behavior are presented.

Larvae of the land-crab, Cardisoma guanhumi , Latreille. were maintained in 24 different combinations of salinity and temperature from the time of hatching. Survival to the first crab occurred in salinities of 15–45 p.p.t., 25° and 30°C. Duration of the five zoeal and one megalops stages was similar in salinities of 20–40 p.p.t., but at 15 and 45 p.p.t. a greater period of time was required for total development. Mortality of all the larvae at 20°C suggests that temperature plays a more important role in survival and distribution of the larvae of C. guanhumi than salinity. Increments of size in crabs during the first seven post-larval molts were similar in salinities of 5–35 p.p.t., 25°C, but in fresh water increase in size at the time of molting was reduced. Although there was no apparent relationship between frequency of molting and salinities of 5–35 p.p.t., the duration of intermolt was reduced in crabs maintained in fresh water, and survival was also lower. From the present study there is no indication that the morphological and physiological processes that are associated with adaptation of the adult crab to the terrestrial environment are initiated during larval development. Although the adult crabs have successfully penetrated the terrestrial environment, the pelagic larvae are still subject to the numerous ecological variables of the estuarine and marine environments.

Numerous incomplete descriptions exist of larval development of the Grapsidae l)ut they are usually based on reconstructions from planktonic material or confined to the first zoeal stage obtained from hatching in the laboratory. Cano (1891) described the development of Pachygrapsus marmoratus up to the crab stage but Hyman (1924) questioned the staging of the three zoeal stages by Cano (1891) and describes 5 zoeal stages from material collected at Beaufort, N. C. Conn (1884), comparing portions of larvae of Brachyura and Macrura, includes some appendages and the telson of Sesarma before and after hatching. Hyman (1924) gave a description of the first zoeae and appendages of Sesarma reticulata and, in describing the first stage of S. cinereum, noted that the two species are very similar morphologically. Aikawa (1929) described the first zoeae of Sesarma sp. l)riefly and figured the first stage of S. picta (1937), comparing setation of some append ages with the description given by Hyman. Thus only the first zoeal stage of any species of Sesarma has been described. The purpose of the present study has been to rear the larvae of Sesarma cinereum (Bosc) in the laboratory, from hatching to the first crab stage, and provide a description of all larval stages.

The crabs which comprise the family Portunidae include several commercially important species and studies on their life history have been in progress for the last 100 years. Of the British species only Portunus puber (L.) has been successfully reared in the laboratory through all larval stages to the first crab (Lebour, 1928). Larvae of Carcinus maenas Penn. have been described by a variety of workers but the complete development is not known from laboratory rearing. Of the American species Callinectes sapidus Rathbun is the most important commercial crab in the Western Atlantic and Gulf of Mexico. Churchill (1942) described the larval development of C. sapidus by reconstructing the sequence of stages from planktonic material. Hopkins (1943, 1944), rearing the larvae through the third zoeal stage, found that not all of the stages fit the description given by Churchill (1942) and was of the opinion that the larvae described by Churchill (1942) represented several different species. The complete larval development of C. sapidus, from hatching to the first crab stage and beyond, was first reported from laboratory rearing by Costlow, Rees and Bookhout (1959). While a brief account is given of the number of stages, the duration of the intermolt periods, and the time required for complete development, the larval stages are not described nor is detailed information given on the various environmental factors under which complete development occurred. The present study has had two major objectives: one, to provide a detailed description of all the larval stages of Callinectes sapidus Rathbun reared in the laboratory; and two, to determine the effects of salinity and temperature on larval development. METHODS

A technique has been devised for rearing segregated barnacle nauplii, under controlled laboratory conditions, which permits daily observations on the frequency of molting, the number of stages, and the specific characteristics of each stage. From a study of 121 segregated Balanus eburneus, plus hundreds in mass culture, reared on Chlamydomonas sp. and Arbacia larvae at 26° C. the following conclusions may be drawn:1. Ecdyses provide a definitive method for staging nauplii. The larval phase of B. eburneus consists of six naupliar stages and one cyprid stage. Secondary criteria, such as body size, spine structure, and appendage setation, are given for the larval stages.2. The duration of the six naupliar stages is as follows: first stage, 15 minutes to 4 hours; second stage, one to two days with an average of one day; third stage, one to four days with an average of 1.5 days; fourth stage, one to four days with an average of two days; fifth stage, one to five days with an average of 2.6 days; and the sixth ...

The larvae of six species of Brachyura have been successfully hatched by detaching the eggs from the female, placing them in compartmented boxes, and maintaining them on an Eberbach variable speed shaker at constant temperatures at different salinities. In addition to providing thousands of normal larvae of known species for experimental purposes, the method has the following advantages: it provides adequate aeration, prevents the spread of fungi and protozoans throughout the egg mass, and permits the use of a relatively small number of eggs from the same animal in a limited space.

[Les larves de Pagurus prideauxi Leach ont ete elevees en laboratoire de l'eclosion jusqu'a la glaucothoe. Les larves ont ete soumises a des conditions de temperature differentes (16°C, 19°C et 24°C) et nourries avec des nauplii d'Artemia salina. Des illustrations de chaquc stade larvaire sont donnees et tous les appendices decrits et figures en detail. Nos descriptions sont suivies de comparaisons morphologiques entre les stades de developpement de Pagurus prideauxi et de Pagurus alatus., Les larves de Pagurus prideauxi Leach ont ete elevees en laboratoire de l'eclosion jusqu'a la glaucothoe. Les larves ont ete soumises a des conditions de temperature differentes (16°C, 19°C et 24°C) et nourries avec des nauplii d'Artemia salina. Des illustrations de chaquc stade larvaire sont donnees et tous les appendices decrits et figures en detail. Nos descriptions sont suivies de comparaisons morphologiques entre les stades de developpement de Pagurus prideauxi et de Pagurus alatus.]

The Cirripedia differ from other arthropods in that the body is enclosed by calcareous plates which are not shed with the chitinous layers of the animal body and the inner lining of the mantle. As early as 1854 Darwin reported that members of the families Balanidae and Chthamalidae underwent periods of exuviation. He reports that Mr. W. Thompson of Belfast kept twenty specimens of Balanus balanoides alive, presumabLy in the laboratory, and on the twelfth day all had moulted once and one individual twice. The frequency of moulting over an extended period of time has not been determined accurately for any sessile barnacle, presumably because of the difficulties involved in maintaining them in the laboratory. Thomas (1944) reports that moults of a selected group of Balanus perforatus of uniform size but unknown age occurred about every fifth day but makes no reference to the period over which these observations were made. Other than these observations there has been no statement, to our knowledge, concerning the relationship between growth of shell plates and ecdyses nor is the frequency of moulting and the intermoult period, from the time of settling, known for any length of time in any barnacle. The purpose of this investigation was to determine, therefore, a medium which would support growth of barnacles in the laboratory, to ascertain the time of moulting, period of intermoult, and the relationship of shell growth to the moulting cycle. Balanus improvisus Darwin, a barnacle which settles at Beaufort, N. C. during the winter and spring months, was selected for this study.

Le developpement larvaire de Sesarma reticulatum a ete suivi en laboratoire de l'eclosion au premier stade crabe et au dela. Il y a trois stades zoe et un stade megalope dans le developpement complet avant le stade crabe. Les auteurs donnent une description de chaque stade larvaire et discutent les caracteres qui peuvent etre utilises pour distinguer les larves de S. reticulatum de celles de S. cinereum. Environ 1200 larves ont ete elevees sous cinq photoperiodes experimentales et une naturelle: 24, 18, 12, 6 et 0 heures de lumiere. La photoperiode n'affecte ni la duree des stades larvaires individuels, ni la survie jusqu'au stade crabe. Le developpement complet jusqu'au crabe (25° C, 25 ‰ necessite un minimum de 15 jours et un maximum de 30 jours apres l'eclosion. La survie jusqu'a la megalope varie de 46 a 100 %, alors que de 1 a 33% des larves survivent jusqu'au premier stade crabe dans toutes les conditions experimentales. Aucune variation dans les details morphologiques ni dans le nombre des stades larvaires n'a ete observee avec les photoperiodes experimentales.

The larvae from two Pagurus bernhardus females were reared in the Marine Biological Laboratory, Heisinger, Denmark, in two series at 10° C. and in five salinities from the time of hatching until death occurred or until the hermit stage was reached. In a range of salinities from 15‰ to 3S‰ there was an increase in mortality with a decrease in salinity. Additional causes of mortality included cannibalism of zoeae, particularly in the higher salinities, and failure of glaucothoe to enter a small snail shell. A salinity of 15‰ was too low for first stage zoeae to molt to the second zoeal stage, but some lived for over four weeks. In salinities of 20‰ some zoeae molted twice but at a slower rate than those in higher salinities. Larvae maintained at 25‰, 30‰ and 35‰ molted at a remarkably uniform rate in both series. Zoeal development was completed in 39 to 47 days and development from the time of hatching to the hermit stage took from 52 to 70 days with the majority completing metamorphosis in 60 days...

LITT LE is known of the influence of physical factors on the complete larval development of Xanthid crabs. In reports on the successful rearing of the larvae in the laboratory, data on salinity and temperature are either omitted (Hart, 1935; Knudsen, 1958) or, when given, are limited in range (Chamberlain, 1957). Connolly (1925) mentions that the larvae of Rhithropanopeus harrisi were obtained from waters of different salinity but does not give the hydrographic data for the collecting stations. Bousfield (1955), concerned primarily with distribution of barnacle nauplii in the Miramichi Estuary, does indicate the range of salinity in which he found adults and zoeae of R. harrisi. Studies on the development of the Xanthidae have been primarily confined to descriptions of larval stages based on reconstructions from the plankton (Birge, 1883, Neopanope texana sayi; Hyman, 1925, N. texana sayi, Panopeus herbstii, Eurypanopeus depressus and a few stages of other Xanthids; Connolly, 1925, R. harrisi). More recently the larvae of some species of this family have been reared successfully in the laboratory (Hart, 1935, Lophopanopeus bellus; Chamberlain, 1957, N. texana sayi; Knudsen, 1958, 1959a, 1959b, L. leucomanus leucomanus, L. bellus diegensis, Paraxanthias taylori; and Costlow and Bookhout, 1961a, E. depressus, and 1961b, P. herbstii).

1. Four crabs,Rhithropanopeus harrisii, Hexapanopeus angustifrons, Libinia emarginata andCallinectes sapidus, were reared from the egg to the first crab stage on freshly hatchedArtemia salina nauplii from two sources: salt pools in California, and the Great Salt Lake in Utah. All larvae showed better survival on California nauplii than on Utah nauplii. The crab larvae fed on California nauplii showed normal development, whereas allR. harrisii megalopa and someH. angustifrons showed a particular set of abnormalities. 2. There is evidence that the difference in normality and survival of developmental stages of the four species of crabs may be due to a difference in the quantity of DDT inArtemia nauplii from California and from Utah. There was approximately three times as much DDT inArtemia nauplii from Utah as in the nauplii from California. The nature of the abnormalities which appeared in larvae fed on Utah nauplii resembled DDT poisoning which has been reported in juvenile and adult crabs.

Le developpement du pagure, Pagurus alatus Fabricius recolte dans la baie de Naples, a ete suivi en laboratoire a une temperature de 18°C et une salinite de 35% de l'eclosion au premier stade crabe. La duree moyenne de chacun des quatre stades zoe et du stade megalope a ete respectivement de 7,6 jours, 5,6 jours, 6,5 jours, 9,3 jours et 11,6 jours. La duree totale du developpement de l'eclosion au premier crabe a varie de 38 a 42 jours. Quatre stades zoe et une stade megalope sont decrits. Une illustration detaillee est presentee pour montrer la sequence des changements qui ont affecte, au cours du developpement aux appendices de toutes les zoes et de la megalope. Les soies et l'armature de la rame externe des antennules, le lobe coxal de la maxillule, le scaphognathite de la maxille et les trois maxillipedes, aussi bien que les differences dans le developpement du troisieme maxillipede et la forme du telson, sont les caracteres qui permettent de distinguer les zoes de Pagurus alatus des zoes des autres especes de la sous-famille des Pagurinae qui ont ete elevees. Les caracteres utiles pour separer les glaucothoes de Pagurus alatus des autres especes comprennent la forme du rostre, les ecailles oculaires, la longueur des pedoncules oculaires rapportee a leur largeur et l'ensemble des traits des appendices.

The larval development of Eurypanopeus depressus (Smith) has been followed in the laboratory from hatching to the first stage crab and beyond. Approximately 1200 larvae were maintained on Artemia nauplii and fertilized Arbacia eggs at four salinities (12.5, 20.1, 26.7, and 31.1 p.p.t.) and three temperatures (20° C., 25° C., and 30° C.). From these studies the following conclusions may be made: 1. There are four zoeal stages and one megalopa stage in the complete development to the first crab stage. These are figured and described. 2. The setation of all functional appendages has been described and figured for each larval stage. There is a progressive increase in setation of the endites of the maxillule as development progresses. Setation of these appendages may serve to distinguish the zoeae of E. depressus from zoeae of P. herbstii. In living zoeae, the presence of chromatophores in the antennules of E. depressus may also be used to differentiate the zoeae from those of P. herbstii. 3. Although the megalopa of E. depressus may be distinguished from the megalopa of P. herbstii, differentiation of larval stages of Neopanope texana sayi, E. depressus, and P. herbstii will require a more complete description of the larvae of N. texana sayi.

While there have been numerous studies on Cirripedia larvae based on reconstructed life-histories, to date there have been only three reports on nauplii reared from the egg through all larval stages to the sessile form, that of Herz (1933) for Balanus crenatus, Hudinaga and Kasahara (1941) for Balanus amphitrite hawaiiensis, and Costlow and Bookhout (1957) for Balanus eburneus. This method has the advantage over reconstructed life-histories in that one can be sure of the identity of the adult, the source of eggs and future larvae. Once the life-histories of all species of barnacles in a given area have been described, ecological studies may be made with a greater degree of assurance. Ecological investigations based on sampling, such as that of Bousfield (1955), may provide the number of stages, the approximate duration and mortality of the individual stages, and the distribution and fluctuations in large populations. Laboratory studies on individually reared larvae, however, can give more detailed information on all phases of the life-history other than distribution and population fluctuations. Both types of research are required before a complete picture can be obtained. Laboratory studies are necessarily prerequisite to physiological and genetic investigations. Balanus amphitrite denticulata Broch is one of the most widely distributed acorn barnacles. It has been reported from the tidal waters of Britain which are artificially heated by industrial effluents (Crisp and Molesworth, 1951), the estuaries of South Africa (Sandison, 1954), and the East and West coasts of North America (Dr. Dora Henry, personal communications). In spite of its world-wide distribution only the first two larval stages have been described (Sandison, 1954). Bishop (1950) believes that Balanus amphitrite denticulata merits a more thorough study and questions its position as a variety of B. amphitrite. Thus it should be of interest to compare the larval development of this variety with the descriptions of larvae of Balinus amphitrite albicostatus (Ishida and Yasugi, 1937) and Balanus amphitrite hawaiiensis (Hudinaga and Kasahara, 1941). Balanus amphitrite denticulata is the most abundant fouling organism in the inter-tidal region at Beaufort, North Carolina and breeds during the same summer months as Balanus eburneus. During the past two years we have followed the larval development of B. amphitrite denticulata in the laboratory to determine the number of stages, the frequency of molting, and the duration of the intermolt periods. Our secondary objectives were to compare the appendage setation and body form with the corresponding naupliar stages of the other two varieties of Balanus amphitrite which have been described and with the larvae of barnacles belonging to different species and genera.

The larvae ofPinnotheres maculatus, say, a small commensal crab commonly found in the scallopAequipecten irradians, have been reared from hatching to the crab stage under laboratory conditions. The zoeae were reared at 30%. 25°C and fed recently hatchedArtemia, nauplii and fertilizedArbacia eggs. The five zoeal stages and one megalops stage are described and figured. The larvae ofP. maculatus can be distinguished from all others which have been described on the basis of general morphological features.

The larval stages of the Xanthid crab,Hexapanopeus angustifrons (Benedict and Rathbun) have been reared under constant conditions in the laboratory. The four zoeal stages and one megalops are figured and described. The zoeae can be differentiated from larvae of other Xanthid crabs by the absence of dorsal or lateral spines on the telson. The rostral spines of the megalops ofH. angustifrons distinguish it from megalops of other Xanthid crabs which have been described. At 25°C, 30 p.p.t., development to the crab required a minimum of 21 days and a maximum of 37 days. Survival to the first crab ranged from 30 to 74%.