Field studies of Cybocephalus nigriceps nigriceps (J. Sahlberg) (Coleoptera: Cybocephalidae) in Israel

Summary

Cybocephalus nigriceps nigriceps (J. Sahlberg) reproduces in Elat (the Arava region of Israel) during spring and summer. Eggs and larvae are present on date palms during these seasons only, whereas adults occur in the grove throughout the year. The adult population reaches its peak in mid-summer and decreases considerably during spring and autumn. Two main locations in which adults occur during the seasons, were found on date palm trees.

Due to the lack of reproduction and activity during autumn and winter, the predator takes almost no part in the biological control of the parlatoria date scale in these seasons.     

Pherbina mediterranea: immature stages,biology, phenology and distribution (Diptera: Sciomyzidae)

The egg, three larval instars, and puparium of Pherbina mediterranea are described. The duration of the various immature stages indicates that this specis is univoltine and spends the winter as quiescent larvae. The biology, phenology and geographical distribution are presented. The main features of the larvae are illustrated with scanning electron micrographs. A key to the adults of genus Pherbina is given.     

Seasonal reproduction in deep-sea Crustacea (Isopoda: Asellota)

A collection of Crustacea Isopoda (suborder Asellota) from a 10-year sampling programme in the Rockall Trough, NE Atlantic (54°40′N, 12°15′W) was analysed for evidence of breeding seasonality. No evidence of seasonal activity was found — adults and newly released juveniles were present throughout the year — but there was a strong seasonal pattern for breeding intensity. A significantly higher proportion of females was brooding during the winter months (25%) compared to the summer (5%), and the percentage of females brooding varied significantly with depth. The breeding pattern was synchronized to the seasonal deposition of organic detritus known to occur during the summer in the NE Atlantic. There were more newly released juveniles in samples during the summer than during the winter, with most females appearing to release their young at the time the deposition began. This deposition appears to be a major seasonal factor dominating the life-cycles of most benthic species in the Rockall Trough. Juvenile settlement for a range of taxa (echinoderms, molluscs and crustaceans) occurs while the detritus is present and most species maximize vitellogenesis at this time.     

LXI.—Notes on insects collected in West Greenland by the Oxford University Greenland expedition, 1936. With descriptions of a new species of Angitia (Hymenoptera,Ichneumonidæ)by A. Roman,and of Fannia (Diptera,Anthomyidæ) by J. E. Collin

Summary

A population of Chaetogaster limnaei limnaei Gruffydd, living on various molluscs in the Worcester-Birmingham canal, was studied from February 1971 to February 1973 in the course of a detailed study of the digeneans parasitizing the molluscs.

The incidence of C. l. limnaei on each of its hosts was recorded for each month during the sampling period.

The incidence of the worms was high during the winter months on Physa fontinalis (and Lymnaea peregra) but low during the summer, and was high during the summer and low during the winter on Bithynia tentaculata.

It is postulated that this pattern of incidence may have been due to a migration of the worms from the pulmonate hosts to B. tentaculata in late spring, when the large pulmonates died after breeding, and a return migration to the pulmonates the following autumn.

There was found to be no association between the digeneans parasitizing the molluscs and the occurrence of the oligochaetes, and it is suggested that in this case the oligochaetes have no influence on the parasitic burden of the molluscs.     

Ovoviviparity in carabid beetles of the genus Pseudomorpha (Insecta: Coleoptera)

Ovoviviparity is reported for the first time in the ground beetle family Carabidae. Eclosed larvae and fully developed embryos are found within the expanded lateral oviducts, bursa copulatrix and vagina of the putative myrmecophiles Pseudomorpha angustata and P. hubbardi. Eclosed larvae do not appear to be active while held inside the female prior to larviposition. Maximum larval numbers occur from mid-July to early September in these Arizona species, implying that larviposition is timed to coincide with summer rains. Larviposition is hypothesized as a means to eliminate egg mortality due to predation by ant hosts.     

Seasonal abundance and life cycle of Archaeomysis articulata (Crustacea: Mysidacea) on a sandy beach of western Hokkaido,Japan

Abundance and life cycle of the sandy beach mysid Archaeomysis articulata Hanamura were investigated based on seasonal collections over 2 years in the surf-swept intertidal zone of an open sandy beach in Ishikari Bay, western Hokkaido, Japan. The number of mysids in the intertidal zone increased from winter to spring, reaching its maximum in summer to autumn (average >2500 ind. m^-2), and decreased considerably towards the end of the year. The abundance was maintained at a minimal level (<200 ind. m^-2) throughout the winter. The breeding season was March to November, during which the liberation of young was most intensive from late April to mid-October. Three alternate generations, including overwintering, spring and summer generations, were suggested from field observations. Archaeomysis articulata is primarily iteroparous; only a restricted number of breeding females could produce more than two broods. The life span was estimated to be 7–9 months for the overwintering generation and 2.5–3.5 months for the spring–summer generations. The sex ratio fluctuated at samplings, with a tendency toward female dominance (overall mean=54%). The number of embryos carried by a single female ranged from 16 to 94, tending to increase with increasing size of females. The size of egg-like embryos varied seasonally from 0.45 to 0.54mm, being largest in spring and smallest in summer, with no correlation to the length of females; water temperature is considered an important factor in regulating the size of eggs. The embryonic development time was estimated to be 1.5 months for the spring generation (water temperature 5–10°C), and much shorter than this for the summer and overwintering generations. The mortality rate during embryonic development was estimated to be 7–18%.     

The larval development of Petalomera japonica (Henderson) (Decapoda,Dromiidae) reared in the laboratory

The complete larval development of Petalomera japonica (Henderson) is described, based on laboratory rearing. The species has two zoeal stages and a megalopa. Detailed comparisons are made with other dromiid larvae, particularly those of Petalomera wilsoni.     

Larval development of the circular crab,Atelecyclus rotundatus (Olivi) (Crustacea: Brachyura: Atelecyclidae) reared in the laboratory

The complete larval development is described of laboratory-reared Atelecyclus rotundatus and the stages are compared with larvae of other cancrideans (= corystoideans). The results suggest that the subfamily Atelecyclinae requires reappraising and that present larval evidence does not support the currently accepted grouping of families in the Cancridea.     

Observations on courtship,mating and sexual maturity in Portunus pelagicus (L., 1766) (Crustacea,Portunidae)

Summary

Larvae of Alpheus heterochaelis from North Carolina hatch from large eggs as advanced zoeae, usually moult three times, and exhibit almost no linear growth during a short (4 days at 25°c) larval development. Stage I lasts 6 hours at most and is sometimes skipped; III lasts about twice as long as II. Individuals simultaneously exhibiting characteristics of Stage III and the postlarva were occasionally seen. The three zoeal stages and postlarva are described in detail and illustrated. Stages in embryonic and juvenile development and the hatching process are briefly described.

An ‘extended’ pattern of larval development, characteristic of most alpheid species, is described in a general way, and the ‘abbreviated’ development of A. heterochaelis compared to it. At hatching, A. heterochaelis larvae bear rudimentary pereiopods and pleopods; other structures are at the same level of development in both patterns, but subsequent morphogenesis is faster in A. heterochaelis. Larval development of Synalpheus spp., some of which exhibit extreme abbreviation or direct development, is briefly described with reference to the A. heterochaelis pattern.     

Survival and reproduction of the mussel Xenostrobus securis (Lam.) (Mollusca: Bivalvia: Mytilidae) in a Western Australian estuary

Summary

The Swan estuary is subject to extreme temporal and spatial variations in salinity. Downstream populations of the mussel Xenostrobus securis (Lamarck, 1819) are exposed to a seasonal range from 1·5‰. Cl to 20·0‰. Cl. In summer the estuary is progressively filled with saline water from the sea; in winter it is flooded by fresh river run-off water from the heavy and concentrated winter rains. The autumn fall in salinity is usually very rapid and constitutes a severe physiological shock for organisms inhabiting the estuary.

The physiography and hydrology of the Swan estuary are described. Experiments are reported on the salinity tolerance and behavioural responses to salinity stresses of adult mussels and larval stages.

Adult mussels show no ability to osmoregulate (except possibly at very low salinities). They can tolerate environmental chlorinities at least as high as 31‰. Cl and can withstand sudden dilutions from at least 18‰. down to 1‰.. They are capable of survival at 1‰. for many months.

Closure of the shell valves in response to sudden dilutions of the medium is a behavioural mechanism minimizing physiological shock. Adult mussels remain inactive with the valves closed indefinitely at chlorinities below 2‰.. However, the internal body fluids of the mussels become isotonic with the medium after a few days. Adult salinity tolerance and behavioural responses are sufficient to meet the conditions occurring in the estuary, and adult salinity tolerance is unlikely to limit distribution of the species.

In laboratory dishes eggs may be successfully fertilized, and normal cleavage occurs in water between about 8 to 9‰. and 17·5‰. Cl. This tolerance range of developing larvae imposes upstream limits on the distribution of the mussel and precludes any possibility of larval dispersal between adjacent estuaries by way of the sea.     

The complete larval development of the crab Pilumnus spinifer (Brachyura: Xanthoidea: Pilumnidae) reared in the laboratory

The complete larval development of the crab Pilumnus spinifer from the western Mediterranean was obtained in the laboratory. All four zoeal stages and the megalopa are described and illustrated. The morphological characters of the larvae of Pilumnus spinifer are compared with those of other known larvae of the genus. The zoeae of P. spinifer show the rostral spine longer than the antennule (excluding aesthetascs); short lateral spines present on the carapace, and the mediolateral processes are present only in abdominal somites 2 and 3. The megalopa is similar to that of other Pilumnidae species. The morphology of the larval stages shows very similar characteristics to that of those of P. hirtellus and P. dasypodus, among the described stages of the family.     

Larval development of the fiddler shrimp,Metapenaeopsis stridulans (Alcock, 1905) (Decapoda: Penaeidae) reared in the laboratory

Larvae of Metapenaeopsis stridulans (Alcock, 1905) from Malaysia were successfully reared in the laboratory from the egg to the 1st post-larval stage. The larvae developed through six naupliar, three protozoeal and four mysis stages. The morphology of all these larval stages is described and figured.     

Larval growth rates and sexual differences of resource allocation in the cetoniine scarab Mecynorhina polyphemus Fabricius 1781 (Coleoptera: Scarabaeidae: Goliathini)

Larval ontogeny of the scarab Mecynorhina polyphemus was monitored throughout all instars, and larvae were weighed at 7-day intervals. Durations of the prepupal, pupal and postpupal stages were recorded. Larvae increase their body masses over 300 times during ontogeny. Male imagines are larger than females, and this is primarily a function of faster growth rates during instar III, resulting in significantly heavier larvae at the end of this instar. The durations of the three instars are not significantly different in males and females, but the duration of the prepupal and postpupal phases is significantly longer in males. There is a strong correlation in both sexes between maximal larval mass and the mass of the imago, but larval mass–imago mass scales with significantly different slopes in males and females. Male larvae must allocate increasingly more resources into production of cephalic horns with increments in larval mass, requiring differently proportioned pupal chambers.     

Larval development of Pandalus gracilis Stimpson (Crustacea: Decapoda: Pandalidae) reared in the laboratory

The complete larval development of Pandalus gracilis Stimpson is described based on larvae reared in the laboratory. The species has four larval stages (stages 1–4) and one postlarval stage (stage 5). The survival rate of the postlarva stage is very high. Of the 40 larvae reared individually, 39 larvae moulted to the postlarva stage within approximately 21 days at a rearing temperature of 15°C. Larval morphological characteristics of the species are described and figured. Larval development of P. gracilis is compared with other Pandalus and Pandalopsis species. Komai (1999 Komai, T. 1999. A revision of the genus Pandalus (Crustacea: Decapoda: Caridea: Pandalidae).. Journal of Natural History, 33: 1256–1372.  [Google Scholar]) divided species of Pandalus into four species groups based on adult morphology. Pandalus gracilis belongs to the P. hypsinotus group. In this study, using larval characters, the P. hypsinotus group can be divided into two groups by the appearance of the mandibular palp and the shape of the telson: the first group contains P. hypsinotus and P. danae, and the second group contains P. gracilis, P. prensor, and P. nipponensis.     

Population structure and breeding biology of the hairy crab Pilumnus vespertilio (Fabricius, 1793) (Crustacea: Brachyura: Pilumnidae) in southern Mozambique

The population structure and reproduction of Pilumnus vespertilio were studied for the first time in Mozambique. Random samples of crabs were taken monthly from January to December 2002 from a pebble area of Inhaca Island, southern Mozambique. A clear sexual dimorphism was observed in the present population with males reaching greater sizes than females. Sex ratio was female‐biased, and the monthly size–frequency distributions were often bimodal. The annual reproductive cycle of Pilumnus vespertilio was continuous with peaks of breeding in summer. Results suggest that embryonic development may be synchronized within the population as a result of the very high reproductive activity observed in summer. Juveniles are recruited mostly in winter in the study area.     

The status of Hemilecanium imbricans (Green) (Homoptera : Coccoidea) in Africa south of the Sahara

Summary

This paper describes the findings from two series of observations on variation in C. austropalpalis L. and R. In Series I the distribution of head capsule lengths of 174 larvae, collected from 11 breeding sites in S.E. Queensland, was polymodal. Polymodality was also shown by the wing lengths of 15♂, 27♀ reared from 7 of the sites. In Series II the head lengths of 302 larvae from 5 sites (one not in Series I) gave the same polymodality, interpreted as representing 3rd and 4th instars of two forms A (smaller) and B (larger). 276 of these larvae, grouped on head length, were reared on agar and small nematodes, producing 62♂, 70♀ C. austropalpalis and 13♂, 5♀ C. narrabeenensis. The latter was not the cause of the polymodality. Adult wing lengths were bimodal in each sex. Form B was longer winged than form A. Within each form there was no significant correlation between larval head length and adult wing length. Only one of the many additional characters (19 in ♀; 22 in ♂) examined, differed between the two forms. Form B had more distinctly patterned wings with the intercalary pale spot more obvious. The results are discussed.     

Developmental stages of Caligus epidemicus Hewitt,a copepod parasite of tilapia cultured in brackish water

The larval development of Caligus epidemicus comprises ten stages: two nauplii, one copepodid, six chalimus, and one preadult (young adult) stages. The morphology of each of these ten instars is described based on material reared from eggs in the laboratory. Addition of fifth and sixth chalimus stages in the ontogeny of C. epidemicus is discussed in the light of the developmental changes in the leg armature. Some peculiarities about the structure of the frontal filament in various chalimus stages are also discussed.     

Morphology and larval development of Polydora cf. websteri (Polychaeta: Spionidae) in a tropical region of north-eastern Brazil

Polydora websteri belongs to a group of the Spionidae known as the Polydora complex, members of which are known for building tubes within the shells of mussels and for their ability to infest commercially valuable bivalves, which causes serious losses for malacoculture. P. websteri is a species subjected to increasing research due to the global scale at which these infestations occur. In this paper, we describe the larval development of P.cf. websteri associated with the oyster Crassostrea cf. brasiliana in a tropical region of north-east Brazil. The main structures of all stages of development were analysed and compared to other populations of P. websteri. Ovigerous capsules of P.cf. websteri were cultured in the laboratory and the larval stages were analysed until metamorphosis. Ovigerous capsules were present in all sampling intervals, indicating that this population exhibits continuous reproduction. Up to 21 capsules per tube were found, and the number of eggs per capsule varied from 20 to 40. All observed eggs developed into larvae. Larval development from egg to recruitment stage did not exceed 13 days. Metamorphosis occurred when larvae attained 17 chaetigers, at which stage important diagnostic characteristics were revealed, such as the spines on chaetiger 5. The developmental stages of P.cf. websteri larvae, and the morphological features found at each stage, are in accordance with what has been recorded for temperate populations. In our study, the planktonic stage was found to be of shorter duration than elsewhere, which might be associated with the higher temperatures at which larvae were cultured compared to previous studies.