The circulatory system of Hutchinsoniella macracantha consists of a tubular heart in thoracic segments 1–6, a dorsoposterior channel, and body fluid (“haemocoelic”) sinuses. The heart, which is possibly closed anteriorly, has three paired ostia dorsolaterally in thoracic segments 2–4. The heart wall is formed by two cellular layers: an inner myocardium and an outer epicardium. The myofibrils are oriented in various directions within the cells. Hutchinsoniella differs from all other crustaceans by lacking a tubule system in the myocardium. The connections between the myocardial cells, called intercalated discs, also differ from those of other crustaceans. The construction of the dorsoposterior channel is unlike that of a typical blood vessel. The body space is organized into a dorsal and ventral haemocoel separated by a thick, cellular, multifunctional, horizontal septum. There is no dedicated pericardial septum. Additional septa and openings between the body cavities channel the circulation of haemocoelic fluid. Resting on the horizontal septum and filling the space between the intestine and the dorsal longitudinal muscles are large cells, here called balloon cells, with few organelles and an otherwise undetermined cytoplasmic content. The function of this new cell type remains obscure.

We have restudied some of the material of a fossil anostracan originally discussed and illustrated by Palmer from the Middle Miocene, Barstow Formation, near Yermo, California, and we now recognize it as a new species, Branchinecta barstowensis. It is the best-preserved fossil anostracan known to date. The closest affinities of this species are with B. pollicifera Harding, 1940, collected from the mountains of Peru and Bolivia around Lake Titicaca.

Setation sequences of the appendages, as well as other characters of cirriped nauplii reared in the laboratory, are invaluable in identification of nauplii taken from the plankton, and in the past few decades those of numerous coastal and a few oceanic species have been described. In addition, larval characters have provided insights into the relationships between various taxa, and it is now apparent certain clades exhibit unique patterns. However, setation sequence patterns of the sixth or last naupliar stage have not been used in phylogenetic studies. Therefore, we have compiled and attempted to standardize them for a preliminary cladistic analysis. Setal characteristics of 31 taxa are compared cladistically with a previously published matrix of largely other naupliar characters. While the results fell short of expectations, rank-order comparisons with a generally accepted classification demonstrates a moderately strong positive correlation between them, that between larval characters and setation sequencing being stronger than either set of larval characteristics was with the classification. Analyses of certain species groups run to test various hypotheses were eminently more satisfactory. Although the present database is limited by the reliability of the original data and our manipulations of them, the results indicate there is sufficient phylogenetic information in larval characters and setation sequences to allow comparisons with generally accepted phylogenies based on adult characters. Refinements of setation sequencing appearing in several recent studies, including recognition of additional setal types and more rigorous comparative approaches in establishing homologies, hold great promise for the future.

The Nauplius is a wobbly thing, a head without a body:

He flops about with foolish jerks, a regular Tom-noddy.

Some said he was an ancestor, but others said: “What, HIM?

He's just a Nectochaeta with Crustacean skin and limb!”

–Walter Garstang, 1954

Doridicola similis n. sp. (Poecilostomatoida, Rhynchomolgidae) is described from specimens found on the gills of a squid (Sepiotheuthis lessoniana Lesson) caught in the Gulf of Thailand. It is close to its congeners D. longicauda (Claus, 1860) and D. sepiae (Izawa, 1976) but can be distinguished from them by the possession of longer caudal rami. A cladistic analysis of the genus revealed that the 12 species of Doridicola associated with mollusks (Gastropoda, Bivalvia, and Cephalopoda) are on the same clade that diverged early in cladogenesis from those species occurring mostly on the octocorallian (alcyonacean) cnidarians. The three species occurring on cephalopods are monophyletic and closely allied with D. agilis Leydig, 1853, occurring on nudibranchs in Europe.

A new highly transformed parasitic copepod, Arthurhumesia canadiensis new genus, new species, is described based on specimens parasitizing the zooids of a compound ascidian, Aplidium solidum (Ritter and Forsyth, 1917), collected near Bamfield Marine Station, British Columbia, Canada. The new genus is distinguishable from its closest allied genera, Gonophysema Bresciani and Lützen, 1960, Capistrum Monniot, 1985, and Tarificola López-González, Bresciani, and Conradi, 1998, in the shape of the dwarf male and its relationship to the female's body. The possible convergence in body shape in these four genera is also discussed.

The description of Dichelina phormosomae is supplemented by study of new material from a deep-water echinoid collected in the North Atlantic, and the homology of some mouthparts is reinterpreted. The phylogenetic relationships between Dichelina and other echinoderm-inhabiting siphonostomatoids are analysed. Based on inferences from the phylogenetic analysis, two new families of siphonostomatoid copepods parasitic on echinoderms are established, the Dichelinidae and the Codobidae. The hitherto unplaced genus Stephopontius is formally assigned to the family Nanaspididae.

The Splanchnotrophidae is a small family of bizarre poecilostomatoid copepods which utilize marine opisthobranch gastropods, including nudibranchs and pteropods, as hosts. Species have traditionally been placed in this family primarily on the basis of host affiliation, largely neglecting the fundamental differences in morphology and paying virtually no attention to the concept of homology. Morphological analysis based on detailed re-examination of types and newly obtained material from existing museum collections revealed that the Splanchnotrophidae comprises genera drawn from three different families in addition to one non-copepodan taxon. The family Splanchnotrophidae is redefined to include only Splanchnotrophus Hancock and Norman, 1863, Ismaila Bergh, 1867, Lomanoticola Scott and Scott, 1895, and two new monotypic genera. All splanchnotrophids are endoparasites of nudibranch and sacoglossan opisthobranchs and show a vast size disparity between the sexes caused by hypermorphosis in the female. The genus Splanchnotrophus is restricted here to the European species and assumes a boreo-mediterranean distribution. It is redefined on the basis of redescriptions given for S. gracilis Norman and Hancock, 1863, and S. angulatus Hecht, 1893. The Western Australian species S. elysiae Jensen, 1990, and S. sacculatus O'Donoghue, 1924, are re-examined and placed in two new genera, Arthurius and Ceratosomicola, respectively. Re-examination of the mouthparts provided unambiguous evidence justifying formal placement of Briarella Bergh, 1876, in the Philoblennidae, a family thus far known only as ectoparasites from prosobranch gastropods in the Far East. The inadequately described genus Chondrocarpus Bassett-Smith, 1903, is provisionally placed as genus incertae sedis in this family. A new family Micrallectidae is proposed to accommodate Micrallecto Stock, 1971. The genus Nannallecto Stock, 1973, is regarded as a junior subjective synonym of the latter because the generic distinction was largely based on two glaring observational errors: the absence of maxillae in M. uncinata Stock, 1971, caused by imperfect removal of the parasite from the host, and the presence of a chelate leg 2 in N. fusii Stock, 1973, which in reality is a feature of the developing nauplii visible through the body wall of the brooding female. Previous interpretations of the mouthparts in Micrallecto were essentially unsound. Micrallectids are ectoparasites of gymnosome pteropods and di

Bunderia misophaga gen. et sp. nov. is described from an anchialine cenote located on the Cape Range peninsula, northwestern Australia. This is the first epacteriscid calanoid known from Australia and represents the third genus of this family of mainly stygobiont copepods recorded in the Indo-Pacific region. Ordinary phenetic analysis points to the monotypic Enantronoides Fosshagen, Boxshall, and Iliffe, from an anchialine cave on the Bahama Islands, as the closest relative of the new genus. This suggests an ancient, relictual status for the new taxon. The predatory habits of the family Epacteriscidae are confirmed after the gut contents of Bunderia yielded remains of a not-yet-described misophrioid copepod.

Both sexes of a new genus and species of Ancorabolidae are described from the San Diego Trough in the Northeastern Pacific. Arthuricornua anendopodia, new genus, new species, is placed in the newly defined Ceratonotus-group which includes the genera Ceratonotus Sars, Dorsiceratus Drzycimski, and Polyascophorus George. Members of this group are characterized by the cylindrical body shape, presence of dorsal processes on somites bearing P2–P4, rostral shape, proximal antennulary elongation, 3-segmented condition of ♂ P3 endopod, and absorption of P5 endopodal lobe in both sexes. The major evolutionary transformations within the Ceratonotus-group are discussed and polarized by outgroup comparison with the Cletodidae. Parsimony analysis confirmed Dorsiceratus and Ceratonotus as monophyletic genera, but demonstrated the polyphyletic status of Polyascophorus. Polyascophorus schminkei George is identified as the earliest offshoot within the Ceratonotus-group and is transferred to a new genus Touphapleura. The common ancestry of Arthuricornua and Dorsiceratus, and the sistergroup relationship between Ceratonotus and Polyascophorus, are strongly supported. A basal dichotomy divides the genus Ceratonotus into two geographically separated clades. The genus Polyascophorus is redefined to include only P. martinezi George and P. gorbunovi (Smirnov).

A new species of leptostracan, Nebalia schizophthalma, is described from a single female specimen from one of the deep-sea stations along the Gay Head-Bermuda Transect. The new species differs from all other known species of the Leptostraca in that the distal margin of the eye is strongly invaginated. Other unusual features include a short, upturned ocular scale, a small indentation along the ventral margin of the carapace, and the absence of strong spinelike setae on the fourth article of the antennule. The new species represents only the fifth species of leptostracan known, and the second in the genus Nebalia, from the east coast of North America.

A new genus, Humesosquilla, is recognized for Squilla decimdentata Manning, 1970. It can be distinguished from all recognized species of Squilla sensu Manning, 1969, sharing a single lateral process of the fifth thoracic somite by the presence of 10–11 teeth on the dactylus of the raptorial claw.

Eleven families of the isopod suborder Valvifera are diagnosed, and a key to differentiate them is presented. Three families, Antarcturidae, Rectarcturidae, and Arcturididae, are erected as new on the basis of a cladistic analysis of 14 families, genera, and genus-groups. Phylogenetic relationships between the families are suggested. The genera of each family, 81 in all, are listed. The generic name Austridotea, previously a nomen nudum, is made available within the Idoteidae. Differentiation of the families is based on fusion of the head and pereionite 1, length of the peduncle of pleopod 1, the male first pleopods, and fusion of the penes. Three families (Chaetiliidae, Holognathidae, Idoteidae) have pereionite 1 free from the head; pereiopod 1 subchelate, similar to others or larger; all pleopods simple and similar; and penes free or a basally fused penial plate. Those families with pereionite 1 fused to the head, pereiopod 1 smaller than other pereiopods and with different structure, an elongate pleopod 1 peduncle, and a fused penial plate have either the exopod of the male pleopod 1 laminar and excavate laterally (Arcturidae) or the exopod thickened and diagonally grooved (Arcturididae, Antarcturidae, Austrarcturellidae, Holidoteidae, Pseudidotheidae, Rectarcturidae, Xenarcturidae).

The endemic Australian eusirid amphipod genus Sancho Stebbing, 1897, is revised based on new material. A neotype is established for Sancho platynotus Stebbing, 1897, which is redescribed, and the new species S. kuiteri is described. Members of Sancho are considered to be obligate commensals of sponges. Their depressed body form and entire telson may be an adaptation to their commensal life-style, but their cantilevered second gnathopods may indicate a phylogenetic relationship with the Eusirus-like members of the Eusiridae.

Most nannastacid cumaceans collected from tropical waters belong to just a few genera, among them the nearly ubiquitous genus Cumella. A new nannastacid genus is described from the West Indian island of Guadeloupe. Members of the genus possess a very long and robust pleonite 6 and short and stubby uropods and share the loss of the ischium on pereiopod 2 and maxilliped 2. This new genus is clearly allied to three species within the genus Cumella, all of which have elongate pleonite 6 and short, but not robust, uropods. These three species are known from the Caribbean Sea, Red Sea, and Gulf of Thailand.

Species of the hermit crab genus Diogenes that either were described by Herbst or attributed to him have been reevaluated, and the ambiguity, both in matters of species authorship and species identity, have been assessed. The species that Herbst incorrectly identified as Cancer diogenes Linnaeus has not, to date, received an available name; therefore, the new name, Diogenes alias, is proposed. The actual holotype of D. miles Fabricius has been identified, and a neotype has been selected for D. custos Fabricius. The “true” D. custos has proved to be the senior synonym of D. affinis Henderson, and the misinterpreted D. custos of numerous authors have been reassigned to D. dubius Herbst. Diogenes platvoeti McLaughlin and Clark (a new name for D. intermedius De Man, non D. pugilator intermedius Bouvier) has been found to be a junior synonym of D. hainanica Wang and Dong and both taxa are synonymous with D. mixtus Lanchester.

The leucosioid genus Praebebalia Rathbun, 1911, is revised. Of the 12 species assigned to Praebebalia, only P. extensiva Rathbun, 1911, and P. septemspinosa Sakai, 1983, are retained in the genus, and two new species are added: P. madagascariensis and P. magna. The four species are described and illustrated, and a key is presented.

The freshwater crabs of the genus Tiwaripotamon Bott, 1970 (Potamidae) are revised and the identities of two poorly known species, T. simulum (Alcock, 1909) and T. araneum (Rathbun, 1905), are clarified after a re-examination of the types. Tiwaripotamon, sensu stricto, is restricted to five species, T. annamense (Balss, 1914); T. araneum (Rathbun, 1905); T. pingguoense Dai and Naiyanetr, 1994; T. xiurenense Dai and Naiyanetr, 1994; and a new species, T. edostilus, from Vietnam. Tiwaripotamon simulum is transferred to the genus Kanpotamon Ng and Naiyanetr, 1993. Keys to the species of Tiwaripotamon and Kanpotamon are also provided.

Biometrical analyses have been carried out on 26 population samples of Carcinus from the Pacific (1), Atlantic (17), and Mediterranean (8), to investigate the validity of the taxonomic division of the genus into C. maenas (Atlantic) and C. aestuarii (Mediterranean). Consideration of carapace width to carapace length and carapace width to carapace depth ratios, and a set of 10 biometric characters by canonical variates analysis, showed that there were two different statistical populations in the European data set apparently corresponding to Atlantic and Mediterranean specimens of Carcinus. There was still overlap of individuals between the Atlantic and Mediterranean data sets, such that individual crabs could not be assigned unequivocally to one group or the other on the basis of shape. The presence or absence of setae on the frontal distal margin of the cheliped carpus varied geographically. Mediterranean crabs possessed prominent setal brushes, while crabs from the Atlantic north of (and including) Porto in Portugal lacked these setae. Crabs from the other Portuguese sites, from the Palmones estuary in southern Spain, and from Gibraltar did, however, sometimes have a few setae on the cheliped carpus. This observation indicates lack of complete genetic separation of the Atlantic and Mediterranean populations of Carcinus, with the potential existence of a hybrid zone between them. The morphological data do not support the separation of European Carcinus into two taxa distinct at the species level, but additional genetic data are needed to verify the presence of any real gene flow and a hybrid zone between Atlantic and Mediterranean crab populations.

A new genus and species of symbiotic, semi-parasitic nemertean worm, Ovicides julieae n. gen., n. sp., is described from the xanthid crabs Chlorodiella nigra and C. xishaensis. The new genus possesses accessory stylet pouches and exhibits simultaneous hermaphroditism, features new to the family Carcinonemertidae. The new species has a relatively small anterior proboscis chamber and small basis, yet it possesses the largest stylet to basis ratio (up to 0.650) reported for the family. It also has a flame cell pattern of at least 2[(3 3)], which is different from those reported for two other species. The worm occurred in a lightly granulated sheath on the abdominal sterna, pleopods, and clutches of its host, but few adult worms were found. The species exhibited a high host specificity and was more frequently found on C. nigra than on C. xishaensis (7.5 vs. 0.4%, overall prevalence, respectively). Worms were only found on female crabs, and worm intensity showed a modest but significantly positive correlation with host size. Ovicides julieae represents the second genus in the Carcinonemertidae, the fifth described carcinonemertid species from Australia, and the eleventh described species in the family.