Comparative fecundity and reproductive strategies in seventeen species of the Cumacea (Crustacea: Peracarida)

The fecundity of 17 species of cumaceans belonging to 5 families from the eastern and western temperate regions of the Atlantic and the Canadian Arctic and Subarctic Oceans are discussed separately and then compared. The species range from 0.78 to 10.11 mm (mean carapace length) with fecundities ranging from 15.1 to 168.9 (mean number of eggs brood^-1 female^-1). Interspecific comparisons show that carapace volume versus volume of brood yields a very strong relationship (r=0.99). Therefore, it is a combination of carapace volume plus egg volume which determines the fecundity in the Cumacea. A discussion of the various life-history and reproductive strategies employed by the Cumacea is included.     

Functional cytology of the hepatopancreas of Penaeus semisulcatus (Crustacea: Decapoda) during the moult cycle

In the shrimp Penaeus semisulcatus, the digestive gland functions as the main site for the digestion, absorption and storage of nutrients and metals during the feeding stages of intermoult and for the mobilization of reserves during the non-feeding stages of pre-and post-moult. These different activities are reflected directly in the cytology of the gland. All the epithelial cells show marked fluctuations in frequency and changes in structure, form and function which occur in phase with the moult cycle. The shrimp were collected offshore from Kuwait in 1980.     

Vertical distribution, population structure and life cycle of Neocalanus cristatus (Crustacea: Copepoda) in the Oyashio region, with notes on its regional variations

Vertical distribution and population structure of Neocalanus cristatus were investigated at Site H in the Oyashio region from September 1996 through October 1997 to evaluate their life cycle mode. Additional temporary samplings were also made at several stations covering the entire subarctic Pacific, Okhotsk Sea and Japan Sea, as a basis for regional comparison of life cycles of this species. At Site H, N. cristatus spawned throughout the year below 500 m depth, with a peak from October to December. The resulting eggs and nauplii floated/migrated upward, and formed an abundance peak of Copepodite Stage 1 (C1) in the surface layer in February. In the surface layer, the C1 developed and reached C5 by early June through a phytoplankton bloom which occurred in mid-March to end of June. The C5 migrated to deeper layers in July and August, where they molted to adults. Apparently, the developmental time from C5 to adults was highly variable (>1 month), and some might overwinter. The life cycle of N. cristatus appeared to be annual for the major portion of the population. Taking into account sampling season, temporal changes in vertical distribution and population structure data collected from regions other than Site H, there was a close correlation in the timing of the life cycle over the entire subarctic Pacific, but the reproduction season (April to June) was observed to be different in the Okhotsk and Japan Sea populations. Regional comparison of prosome length of C5 individuals, including those in the Bering Sea, indicated significantly larger sizes of specimens from the Japan Sea and Okhotsk Sea, as compared with those from the entire subarctic Pacific. Possible causes for regional variability in life cycle patterns and body sizes are discussed. Received: 18 December 1998 / Accepted: 19 April 1999     

An unusual abbreviated larval life in the estuarine burrowing prawn Callianassa kraussi (Crustacea: Decapoda: Thalassinidea)

The larval stages of Callianassa kraussi Stebb. were previously unknown. Larvae were bred out in the laboratory and found to be incapable of swimming. There are two larval stages, lasting 3 to 5 days in sea water of 34 to 35 S at 20 °C. Observations under simulated field conditions in the laboratory, and in the field—where burrow casts were made using a polyester resin, indicated that the larvae metamorphose to the first post-larval stage in the parent burrow, and then burrow directly into the wall of the parent burrow.     

Experimental studies on physiological and behavioural response mechanisms of Nitocra spinipes (Crustacea: Harpacticoidea) from brackish-water rockpools

Volume regulation and salinity-preference tests have been made on Nitocra spinipes Boeck (Crustacea, Harpacticoidea). This species is often dominant in Baltic brackish-water rockpools. The investigation attempts to evaluate the relative importance of some of the different response mechanisms of this species to salinity changes in relation to the unstable environmental conditions of the rockpools. Volume-regulation experiments have shown that N. spinipes is capable of hypoosmotic and probably hyperosmotic regulation in the tested salinity range of 1 to 20 S. In laboratory cultures, reproduction, hatching and moulting oecurred in salinities ranging from 0.5 to 30 S. Preference experiments showed that N. spinipes has a very weak behavioural response even to very large variations in salinity concentrations between the alternative; a significant choice could only be found under conditions which never occur in the natural biotope. It is therefore concluded that, in a biotope such as the rockpool, where salinity changes will affect the whole biotope rather than produce microclimatic variation, regulation and adaptation must have a higher ecological importance than escape responses.     

Aspects of the reproduction and life cycle of Rhabdopleura compacta (Hemichordata)

Rhabdopleura compacta Hincks is shown to be monoecious. It is suggested that the ovum is ovulated and extruded into the lumen of the coenecium via a temporary opening at the base of the metasome, and that the oviduct itself may serve only as a way for sperm to fertilise the ova internally. The zooids degenerate when reproducing sexually and when conditions are unfavourable. The larva and initial stages of astogeny are described. Some observations on seasonal variation in the colonies indicate that the dormant buds serve for storage of nutrients. Reproduction seems to occur throughout the year, but most actively in spring. Relationships with Cephalodiscus and the Bryozoa are briefly discussed.     

Observations on rock boring by Alpheus saxidomus (Crustacea: Alpheidae)

This study describes some aspects of the distribution, ecology, and rock boring behaviour of the shrimp Alpheus saxidomus Holthuis from the Pacific coast of Costa Rica. This species has a typical hammer-shaped dactylus on the first right pereiopod of females and males that shows tracks of abrasion at the hammer-head. Structural analysis of this hammer-dactylus proved that it is suited for the mechanical treatment of rocks. The very thick and calcified cuticle of the hammer is mostly formed by the sclerotinized, hard exocuticle, which has abundant pore canals.     

Larval development of Euphausia nana (Crustacea: Euphausiacea)

The larvae of Euphausia nana Brinton in Sagami Bay and Suruga Bay, Central Japan, are described and illustrated. The furcilia stage is separated into six stages on the basis of the form of the pleopods and the number of terminal telson spines. Furcilia I, no pleopod or non-setose pleopods and seven terminal telson spines. Furcilia II, nonsetose and setose pleopods and seven terminal telson spines. Furcilia III, five pairs of setose pleopods and seven terminal telson spines. Furcilia IV, five pairs of setose pleopods and five terminal telson spines. Furcilia V, five pairs of setose pleopods and three terminal telson spines. Furcilia VI, five pairs of setose pleopods and one terminal telson spine. Segmentation of the antennal endopod and mandible palp occurred at the furcilia V stage. The dominant forms of early furcilia larvae of E. nana differed during different seasons of the year. The total lengths of calyptopis III and furcilia I to VI larvae also showed seasonal changes; they were largest in May and smallest from September to December.     

Environmental influence on the locomotor activity rhythm of Talitrus saltator (Crustacea: Amphipoda)

The persistence and precision of the endogenous, nocturnal, circadian locomotor rhythm of the sand-beach amphipod Talitrus saltator is characterised, and the influence of substrate availability, photoperiod, temperature and relative humidity as potential environmental synchronizers of the rhythm is assessed. Individual, cyclic light-dark and temperature regimes synchronize and modify the laboratory activity pattern, but substrate availability and relative humidity have no significant long-term effect. Under simulateneous experimental regimes simulating field conditions of photoperiod, temperature and relative humidity the rhythm is entrained solely by photoperiod. The implications are discussed in relation to field behaviour.     

Group orientation in Neomysis mirabilis (Mysidacea: Crustacea)

The orientational behaviour of the neritic mysid Neomysis mirabilis in a swarm is considered under natural and experimental conditions. In nature, the swarms exhibit elements of inner integration, such as homogeneous age structure, collective behaviour, and relative constancy of inter-individual spacing. The mysids are guided by combined optomotor and vibrotactile cues, determining their disposition in aquaria of different shapes. Maximum accuracy of spatial arrangement is observed in round vessels. It is suggested that the stress encountered in an aquarium produces responses comparable to those elicited by the presence of a predator. The rigid spatial arrangement at the supra-individual level is interpreted as evolutionally-optimized prey strategy. These elements in the geometrical distribution of individuals in mysid swarms are inherent in other pelagic crustaceans also, and are not controlled by random taxes stimulated by hydrological factors.     

Offshore spawning by the portunid crabScylla serrata (Crustacea: Decapoda)

The portunid crabScylla serrata (Forskål) is shown to migrate offshore to spawn. Records of 447S. serrata caught as bycatch by trawlers in the tropical waters of northern Australia were analysed with respect to area, depth, distance offshore and month of capture as well as the sex and size of the crabs and whether the females were ovigerous. The crabs were caught mainly in three areas that correspond to the tiger prawn trawl fishery, at between 10 and 60 m depth (mean 28.5 m), 3 to 95 km offshore (mean 17.9 km). Most (87%) of the crabs were captured in October and November, which suggests they move offshore in September and October. No crabs were reported from offshore by February. Over 97% of the crabs caught offshore were female, of these 61.5% were ovigerous. The size range of females (100–109 to 200–209 mm carapace-width size classes) and males (120–129 to 200–209 mm carapace-width size classes) caught was similar. The frequent occurrence in coastal waters of females that are larger than the modal size at spawning, as well as mature females with spent ovaries, suggests that many females return to the coast after spawning. Although some species of portunid crab are euryhaline, mature females of estuarine species migrate to the sea to spawn. The migration byS. serrata described here is far more extensive than would be required to reach sea water salinities; it probably provides a dispersal mechanism for larvae to enable the megalopa stage to recruit to habitats distant from those of the parents.     

Orientation of Coenobita rugosus (Crustacea: Anomura): A field study on Aldabra

Experiments were designed to determine whether anemotaxis shown by the terrestrial hermit crab Coenobita rugosus H. Milne Edwards is (i) an orientational strategy leading the crabs to sea or (ii) a strategy improving rectilinear flight. In an arena with uniform landscape, hermit crabs from different beaches of the Aldabra atoll orientated during daylight in the direction of the sea of their own beach; this orientation was only slightly affected by wind direction. Under artificial wind conditions, at night, all hermit crabs displayed positive anemotaxis, independent of the orientation of the home beach, thus leaving little support for the first hypothesis. During the day, with the sea and beach both visible, all the hermit crabs on the beach moved landwards irrespective of wind and home beach direction.     

Growth and moulting of Neomysis integer (Crustacea: Mysidacea)

The growth and moulting of Neomysis integer (Leach) was investigated in the field and the laboratory. In the Ythan estuary, Aberdeenshire, Scotland, monthly samples taken from November 1976 to October 1978 revealed that the summer generation juveniles and mature individuals grew at a rate of 4 to 5 mm and 1 to 2 mm monthly, respectively. The winter generation had a growth rate of 3 to 4 mm monthly for juveniles and about 1 mm for mature individuals; during the winter there was a period of 3 mo when growth was almost completely stopped. Mysids reared in the laboratory on Artemia sp. nauplii had an average daily growth rate of 0.06 mm at 9°C and 0.09 mm at 16°C. The growth factors of N. integer ranged from 3 to 17% for mature and immature individuals, respectively. Intermoult periods ranged from 3 to 7 d in immature mysids to 12 to 18 d in mature mysids. Average laboratory growth curves calculated from information on growth factors and intermoult periods indicate that at 9°C (winter generation) it takes N. integer 277 d to grow to be a 15 mm mature individual, whereas at 16°C (summer generation) it takes 188 d. N. integer moults 24 times as it grows from a juvenile to a mature individual.     

Observations on the biochemical changes in gonads and other organs of Uca annulipes,Portunus pelagicus and Metapenaeus affinis (Decapoda: Crustacea) during the reproductive cycle

The fluctuations in biochemical constituents such as water, nitrogen, non-protein nitrogen, protein, lipid and glycogen in gonad, muscle and hepatopancreas have been followed in 3 decapod crustaceans, Uca annulipes (Latreille), Portunus pelagicus (Linnaeus) and Metapenaeus affinis (Milne-Edwards). The water and ash content of the entire body show no systematic fluctuation in relation to the annual reproductive cycle. The water content of the ovary diminishes as it matures. In the ovary of these crustaceans, the lipid fluctuated greatly in relation to the reproductive cycle. The maturing ovary contains more lipid than an immature or spent ovary per unit tissue weight. The changes in the biochemical constituents in the testis are not so pronounced as in the ovary, since the testicular cycle is often drawn-out and almost continuous in these crustaceans. There is an inverse relationship between water content and lipid content of the hepatopancreas; the greater the fat content, the lesser the water content. The hepatopancreas in these crustaceans is apparently a storage organ and contains much lipid and glycogen. At the height of the breeding season, when gonad production is intense, there is an indication of the mobilisation of at least a part of the lipid from hepatopancreas to gonad.Dissertation for the award of a Doctorate Degree of the Kerala University.Formerly the Marine Biological Laboratory.     

Studies of the pigments in the shrimp Crangon crangon (Crustacea: Malacostraca)

The material examined consisted of adult specimens (male and female) of the shrimp Crangon crangon (L.) collected during the summer of 1967 from the Gdask Bay of the Baltic Sea. Column and thin-layer chromatography was used for the separation of the carotenoids. The ester compounds and protein complexes of carotenoids were hydrolized with 15% KOH in methanol at room temperature in a nitrogen atmosphere for 48 h. The absorption maxima of the various fractions and spots were determined on the spectrophotometer Specol after eluation. The identification of the carotenoids was based mainly on the absorption maxima in appropriate organic solvents and on the R_t values. The acetone extract from the Crangon crangon specimens gave a light blue fluorescence and absorption maxima at wavelengths of 447, 463, 595 to 596 and 667 m. The following carotenoids were found to be present in the adult specimens of Crangon crangon: -carotene, cantaxanthin, astaxanthin, free and esterified lutein, zeaxanthin, and a form of xanthophyll which was not precisely identified. In addition to the above, biliary dyes were also found, probably of the mesobiliviolin and mesobilirhodin type.     

Mound building in Ilyoplax pingi (Crustacea: Brachyura: Ocypodidae)

The ocypodid crab Ilyoplax pingi, observed in Kanghwa I., Korea in 1992, builds a mound at the burrow entrance, by piling mud dug out from the burrow. The mounds were made by both waving and non-waving males, and by both ovigerous and non-ovigerous females. The burrow diameter at the widest part tended to be larger in crabs with mounds than in crabs without mounds, whereas the burrow depth was not different between them. The mound density increased in the late exposure period, when the crabs' surface activities declined. Mound removal and rebuilding experiments revealed that the presence of the mounds has the effect of keeping neighboring crabs away.     

Neighbor burrow-plugging in Ilyoplax pusillus (Crustacea: Brachyura: Ocypodidae)

The burrow living ocypodid crab Ilyoplax pusillus (De Haan, 1835) sometimes plugs the burrow of neighbors situated from 1.0 to 8.3 cm away with surface mud, while the neighbor, termed the pluggee, is in the burrow. Most pluggers were large males, whereas pluggees were smaller than pluggers and had a sex ratio close to 1:1. After being plugged, most pluggees usually reemerged on the surface within 5 min, but occasionally took up to 77 min to do so. The plugger always foraged or performed waving displays around the burrow of the pluggee while the pluggee stayed inside the burrow. Although the activity site of the pluggee was originally directed toward the burrow of the plugger or the adjacent area, after reemergence its activity site was oriented toward another direction. From these observations, it is suggested that neighbor burrow-plugging is a behavior adopted mainly by large males as a means of maintaining the area of their surface activities against smaller neighbors. My observations were made from June 1984 to June 1985 at Fukuro River Estuary, central Japan.     

Effect of hypophyseal gonadotropins (FSH and LH) on the ovaries of the sand shrimp Crangon crangon (Crustacea: Decapoda)

The effect of purified preparations of ovine hypophyseal gonadotropins NIH-FSH-S12 and NIH-LH-S19 on the histological structure of the ovaries of the sand shrimp Crangon crangon (L.) (Crustacea: Decapoda) was studied. All experiments were carried out on sexually mature females, out of the breeding season. The individuals treated with the gonadotropins included intact females as well as those in which the eyestalks were ligated to eliminate a source of gonad-inhibiting hormone (GIH). The results obtained indicate that both FSH and LH have a stimulating effect on the ovaries of the common shrimp, FSH causing growth in the number of somatic cells of the ovary, and LH — meiosis in the sex cells. The effect of each of the 2 gonadotropins was similar in intact and eyestalkless females which indicates its independence from the presence or absence of GIH. The response of crustacean ovaries to mammalian FSH and LH indicates that gonadotropins may act upon invertebrates.     

In-situ studies on deep-sea amphipods and their intestinal microflora

Amphipods, trapped at depths of 1 410 to 5 330 m and incubated in situ in the presence of a radiolabeled protein as a food source, were fractionated to measure the distribution of label in the major biochemical constituents: low molecular pools, ethanol and base soluble proteins, lipids, polysaccharides and nucleic acids. The results suggest lipid energy storage and enhanced microbial growth within the amphipod guts as compared to growth on the uningested food material. The merits and limitations of this general approach are critically evaluated.     

Trace-metal detoxification in the ventral caeca of Orchestia gammarellus (Crustacea: Amphipoda)

The talitrid amphipod crustacean Orchestia gammarellus (Pallas) was collected from metal-contaminated (Dulas Bay, Gironde) and control (Millport) sites in the UK and France. Irrespective of site of origin, the amphipods showed the same physiological mechanism of trace-metal detoxification, involving the ventral caeca. Copper was always present in lysosomal residual bodies in the ventral caeca. Following laboratory exposure to zinc and cadmium, the lysosomes usually contained both copper and zinc but cadmium was not detectable. The lysosomal copper concentration is positively correlated to that of sulphur, while the concentration of lysosomal zinc is related to that of phosphorus. Results are interpreted in terms of the differential rates of turnover of metallothioneins chelating copper, zinc or cadmium. Received: 9 February 1999 / Accepted: 2 December 1999