Developmental stages and growth of Pseudocaligus fugu Yamaguti, 1936 (Copepoda: Siphonostomatoida: Caligidae) host-specific to Puffer

The post-embryonic development of the copepod Pseudocaligus fugu is described. This sea louse only parasitizes toxic pufferfish, and causes commercial loss of cultured Takifugu rubripes in Japan. Two naupliar, one copepodid and four chalimus stages preceding the adult are recognized in the species. The development pattern is similar to that of Caligus except for the suppression of leg 4 in the early chalimus phase. Pseudocaligus fugu lacks any preadult stage, as in Caligus, but contrasts with Lepeophtheirus species in which two preadult stages are reported. The nature of the metamorphic changes in size and even in degree of expression of articulations can occur without moulting. The validity of some chalimus stages recognized in Lepeophtheirus species is questioned. Growth and egg production in P. fugu were obtained in the laboratory. Pseudocaligus fugu attained adulthood 9 days after the infective copepodid attached to the host.     

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.     

Development of Caligus multispinosus Shen,a caligid copepod parasitic on the black sea bream (Acanthopagrus schlegeli) cultured in Taiwan

The development of Caligus multispinosus was studied using instars reared from eggs in the laboratory and specimens obtained from the gills of pond-cultured black sea bream. Nine stages were identified, namely, two nauplii, one copepodid, four chalimus stages, one preadult and the adult. The distinctive feature of the spinulose outer spines on leg 4 appeared late in development (preadult stage) and the frontal filament produced in chalimus I is kept throughout the chalimus stages.     

Copepodid stages of Lichomolgus forficula Thorell 1859 (Copepoda,Poecilostomatoida, Lichomolgidae), a copepod associated with Phallusia mammillata (Cuvier, 1815)

The five copepodids of Lichomolgus forficula, a poecilostomatoid copepod (family Lichomolgidae), are described. Sexual dimorphism first occurs in copepodid V in which the male maxilliped, unlike that of female, shows a row of spinules on its second segment. Changes of leg armatures during copepodid development are discussed.     

Aestivating sexual morphs in the aphid genus Thelaxes (Insecta: Homoptera)

The sexual morphs of the aphid Thelaxes dryophila are redescribed and compared with the sexuales of other Thelaxes species. The unusual life-cycle of the species, in which the immature sexuales pass the entire summer aestivating, is also described.     

Copepodid stages of laboratory-reared Astericola asterinae (Bocquet, 1952) (Copepoda,Poecilostomatoida, Lichomolgidae), a copepod associated with Asterina gibbosa (Pennant, 1777) of Lake Faro (Messina)

We describe the five copepodids of Astericola asterinae (Bocquet, 1952) a poecilostomatoid copepod (family Lichomolgidae), reared in the laboratory. It shows only very slight sexual dimorphism in the third segment of C5 maxilliped. Our study of the copepodid development, together with the observations of Carton (1964), Bocquet et al. (1970) and Conradi et al. (1993), support the separation of A. asterinae from its sister species A. clausi (Rosoll, 1889).     

A new species of Phyllodistomum (Digenea: Gorgoderidae) from Australian and New Zealand freshwater fishes with notes on the taxonomy of Phyllodistomum Braun, 1899

Phyllodistomum magnificum sp. nov., is described from the urinary bladder of Australian and New Zealand freshwater fish. Australian hosts were Anguilla reinhardtii, Tandanus tandanus, Hephaestus fuliginosus and Scortum hilli. New Zealand hosts were Anguilla australis and A. dieffenbachii. A presumed part of the life-cycle is described. Typical cystocercous cercariae are produced by sporocysts in the gills of a Pisidium species and are eaten by aquatic arthropods in which they encyst. The taxonomy of the genus Phyllodistomum is discussed and it is suggested that those species with cystocercous cercariae form a phylogenetic unit with Gorgodera, Gorgoderina, Progorgodera and Gorgotrema species.     

The association of Amphisbaena alba (Reptilia: Amphisbaenia) with the leaf-cutting ant Atta cephalotes in Trinidad

Evidence suggests that Amphisbaena alba is a facultative inquiline of nests of the leaf-cutting ant Atta cephalotes in Trinidad. The evidence is culled from three main sources: (i) direct excavation of Atta nests; (ii) the ability of A. alba to follow Atta trail pheromones; (iii) the analysis of A. alba intestinal or faecal contents. When inside ant nests, A. alba may feed primarily on arthropods, notably beetles, which are themselves inquilines in ant nests. Studies on the life-cycle of a pentastomid parasite of A. alba, which depends for transmission on ant and beetle inquilines, also indicates that A. alba and Atta are intimately associated. The literature suggesting a regular association between ants (and termites) and amphisbaenians in general is reviewed.     

A revision of Monocotyle Taschenberg, 1878 (Monogenea: Monocotylidae) with descriptions of three new species from Australia

Monocotyle is revised and three new species are proposed. Monocotyle corali sp. nov. is described from the gills of the cowtail ray, Pastinachus sephen (Forsskål) (Dasyatididae), and is distinguished from other members of Monocotyle by the large hamuli with a distinct tail on the guard and by the male copulatory organ with three loops and a wing-like accessory piece at the distal end. Monocotyle jordani sp. nov. from the gills of the southern eagle ray, Myliobatis australis Macleay (Myliobatididae), is differentiated by the male copulatory organ with a large, unique accessory piece. Monocotyle youngi sp. nov., from the gills of Himantura fai Jordan and Seale (Dasyatididae), has marginal haptoral papillae armed with 12 to 15 sclerites, a male copulatory organ with 20 loops and a unique accessory piece at the distal end. Monocotyle trygoni (Venkatanarsaiah and Kulkarni, 1980) Timofeeva, 1985 is synonymized with M. spirophallus Tripathi, 1959 and M. spirophallus is redescribed fully. There are now 16 valid species of Monocotyle and a key to species is presented. Additional data and illustrations of important taxonomic characters are provided. The developmental sequence of the male copulatory organ of M. spiremae Measures, Beverley-Burton and Williams, 1990 from juvenile to adult is described. The anterior glands and the type of secretion they contain are also documented for several species of Monocotyle.     

The larval development of Argulus coregoni Thorell (Crustacea: Branchiura)

Summary

The larval development of Argulus coregoni from the first to the ninth stage was studied, with special reference to the morphological changes of the appendages and some other parts of the body.

A newly hatched larva is a copepodid-form measuring 0·6–0·7 mm long and approaches the shape of the adult after moulting into the second stage (0·7–0·9 mm). Throughout the larval stages, the first maxilla shows the most remarkable modification. The larvae of the first to the fifth stage are equipped with two strong, curved claws, which act as a clasping organ, at the terminal segment of the first maxilla. The basal segment expands considerably at the third stage (0·9–1·1 mm) prior to forming a sucker at the sixth stage (1·7–2·2 mm). The claws start to degenerate at the fifth stage (1·4–1·8 mm), but are still recognizable as a rudiment after the seventh stage (2·2–2·6 mm). The other distinct morphological changes that occurred are: (1) bifurcation of the anterior part of the dorsal ridges on the carapace, (2) development of the male accessory copulatory organ at the basal segments of the second to the fourth legs, (3) number of posteriorly directed minute spines on the ventral surface of the carapace, (4) number of elements in the supporting ribs of the suckers, (5) number of spines found at the first segment of the second maxilla, and (6) number of setae on the four pairs of thoracic legs.

The larval forms of A. coregoni younger than the fourth stage (1·1–1·4 mm) are indistinguishable from those of A. japonicus and A. foliaceus.     

Three new species of Pseudohaliotrema Yamaguti, 1953 (Monogenea: Ancyrocephalidae) from Siganus species (Siganidae) and the description of a mechanism for cross-insemination

Three new species of Pseudohaliotrema Yamaguti, 1953 were collected from two Siganus species caught off Singapore. They are Pseudohaliotrema virgata n. sp. and P. molnari n. sp. from Siganus virgatus and P. falcata n. sp. from S. guttatus. They differ in the shape and size of both the body and haptoral sclerites and in the morphology of the male organ (modified copulatory organ). Pseudohaliotrema species from siganids are characterized by having a large prominent vaginal pouch, an eversible spermatophore transfer tube associated with the vaginal pouch, ovoid spermatophores (in mature worms), a male organ adapted for spermatophore formation, a large prostatic reservoir, and a testis and ovary arranged side by side. Pseudohaliotrema plectocirra Paperna, 1972 is re-assigned as Tetrancistrum plectocirra (Paperna, 1972) n. comb. Pseudohaliotrema species from non-siganid fish do not possess these characteristics and belong elsewhere. The generic diagnosis of Pseudohaliotrema is amended. Pseudohaliotrema species use a spermatophore for sperm transfer, which is documented in detail for P. virgata n. sp. The same reproductive strategy is used by P. molnari n. sp. and P. falcata n. sp., as indicated by the presence of spermatophores on the spermatophore transfer tube and inside the vaginal pouch. The presence of individuals exchanging spermatophores indicates that P. sphincteroporus Yamaguti, 1953 and P. sigani Yamaguti, 1953 also employ the same mechanism. The spermatophore, assembled in the sclerotized male organ and stored in the spermatophore chamber, is retrieved by the eversible spermatophore transfer tube (housed within the vaginal pouch) and drawn into the vaginal pouch as the spermatophore transfer tube invaginates. Within the vaginal pouch, the wall of the spermatophore disintegrates releasing spermatozoa.     

New insights on the external features of egg capsules and embryo development in the squid Loligo vulgaris

The embryonic development of the squid Loligo vulgaris was observed from 183 egg masses collected from special devices deployed throughout Cabrera National Park (Baleares Islands, western Mediterranean Sea). Sequence alignment analysis of the cytochrome oxidase I gene revealed that all embryos belonged to L. vulgaris. In total, 549 egg capsules were examined. Viable egg capsules (n = 420) were classified into one of five maturation stages according to the primary external features. The length of the viable egg capsules varied between 40 and 170 mm, and increased with embryonic development. The non-viable capsules (n = 129) were categorized into four groups: I (Ginger root), non-viable II and III, and empty egg capsule (IV). The percentage of non-viable capsules (i.e. grades I, II and III) was 92.25%. Empty capsules accounted for 7.75% of the total non-viable egg capsules. Embryonic development was classified into a second scale of eight stages. Egg capsule stage and embryonic stage were significantly related (n = 420; p < 0.001), facilitating the determination of the embryo developmental phase based on the outward appearance of the egg capsules. The embryo development stage based on the external features of the egg capsules might constitute an innovative tool for in situ embryological data collection. This new method is neither time consuming nor invasive, and could be helpful in fishing cruises, for scuba diving visual census in natural habitats and for laboratory culture. Slight variability in the developmental embryonic stages within egg capsules from the same egg mass was identified. The origin of this asynchrony is discussed. Chronological appearance of organs was similar to that of the six loliginid species previously examined. However, some developmental changes in the timing or rate of events (heterochronies) were observed: Hoyle’s organ was formed earlier in L. vulgaris and the appearance of ventral chromatophores was slightly delayed (2 days) compared with the other species considered.     

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.     

Progenesis as a principle in meiofauna evolution

The interstitial meiofaunal taxa may have evolved in very different ways, which are shortly discussed and schematically represented. Several taxa reveal the possibility of an evolutionary pathway by early maturation of larvae or juvenile stages of large size species with a pelago-benthic life-cycle. This presumed progenetic (= neotenic) evolution can be sustantiated in, for example, various Polychaeta and Crustacea by larval or juvenile morphological features. The progenetic origin of several of these taxa is also strongly supported by morphological series, of which species conforming well with typical larvae form the endpoint. The monophyletic origin of similar progenetic taxa, however, is only proved with difficulties. The theoretical available phylogenetic reconstructions for a series of progenetic taxa are discussed. It is emphasized that progenetic evolution is not regressive or degenerate but novel morphological features like derived reproductive organs are characteristic indications of the progenetic origin of a species. In general, progenesis may have a significant role in the evolution of higher taxa in the interstitial habitat.     

Zoeal stages of Hiplyra variegata (Rüppell, 1830) (Crustacea: Brachyura: Leucosiidae) reared in the laboratory and collected from plankton at Al-Kharrar creek,central Red Sea

The zoeal stages of Hiplyra variegata are described and illustrated for the first time. Zoea I was obtained from an ovigerous female, and the zoea II and zoea III stages were captured in the plankton (their identity was confirmed by rearing some of them from earlier stages). Comparisons are made with the only other species of the genus of which larvae are known, i.e. H. platycheir. The presence of a lateral spine on the carapace of zoea I is one of the most important characters that can be used for easy recognition of H. variegata. It is important to note that the third zoea of H. variegata has four small spines at each posterolateral margin of the carapace, in contrast to three spines in other species.     

Stridulation in Aphodius dung beetles: Songs and morphology of stridulatory organs in North American Aphodius species (Scarabaeidae)

The acoustic behaviour of four Aphodius dung beetle species from the Pacific Northwest of the USA was investigated. Male Aphodius produce substrate vibrations when they meet a conspecific female in a dung pat. The temporal structure of the substrate vibrations and the stridulatory organs are described. The vibrations are species-specific songs that are emitted during courtship. The stridulatory organ is of the abdomino-alary type in the investigated species. Morphological differences with regard to the detailed structure are present.