Geoff A. Boxshall

The evolution of arthropod limbs

Limb morphology across the arthropods is reviewed using external morphological and internal anatomical data from both recent and fossil arthropods. Evolutionary trends in limb structure are identified primarily by reference to the more rigorous of the many existing phylogenetic schemes, but no major new phylogenetic inferences are presented. Tagmosis patterns are not considered, although the origins and patterns of heteronomy within the postantennulary limb series are analysed.

Global diversity of copepods (Crustacea: Copepoda) in freshwater

The zoogeographic distributions of the 2,814 species of copepods reported from freshwater are analysed. Faunal diversity is compared between zoogeographic regions: the Palaearctic region has more than double the species richness of the next most diverse region, the Neotropical. Historical factors affecting levels of diversity are identified. More than 90% of all freshwater copepods are endemic to a single-zoogeographic region and endemic genera occur in all regions except Antarctica. Species that are not endemic to a single region include the highly vagile and cosmopolitan species occurring in four or more regions. The greatest faunal connectivity, as identified by Sørensen’s Index, is between Palaearctic and Nearctic regions, and identifies the Holarctic taxa. Key human-related issues, such as the role of copepods as vectors for human parasites and the losses caused by parasitic copepods in commercial aquaculture, are mentioned.

The Salmon Louse Lepeophtheirus salmonis (Copepoda: Caligidae) life cycle has only two Chalimus stages.

Each year the salmon louse ( Lepeophtheirus salmonis Krøyer, 1838) causes multi-million dollar commercial losses to the salmon farming industry world-wide, and strict lice control regimes have been put in place to reduce the release of salmon louse larvae from aquaculture facilities into the environment. For half a century, the Lepeophtheirus life cycle has been regarded as the only copepod life cycle including 8 post-nauplius instars as confirmed in four different species, including L . salmonis . Here we prove that the accepted life cycle of the salmon louse is wrong. By observations of chalimus larvae molting in incubators and by morphometric cluster analysis, we show that there are only two chalimus instars: chalimus 1 (comprising the former chalimus I and II stages which are not separated by a molt) and chalimus 2 (the former chalimus III and IV stages which are not separated by a molt). Consequently the salmon louse life cycle has only six post-nauplius instars, as in other genera of caligid sea lice and copepods in general. These findings are of fundamental importance in experimental studies as well as for interpretation of salmon louse biology and for control and management of this economically important parasite.

A revision of the lichomologid complex (Copepoda: Poecilostomatoida), with the recognition of six new families

The superfamily Lichomolgoidea of Humes and Stock (1972, 1973) is revised to take account of the numerous new genera added since 1972. The Urocopiidae is recognized as only distantly related to the other lichomologid families. Six new families, the Anchimolgidae, Kelleriidae, Octopicolidae, Macrochironidae, Synapticolidae and Thamnomolgidae, are established and the concepts of the four remaining families are significantly altered. A diagnosis is presented for each of the 10 families, together with a list of included genera and a key to genera. Emphasis in the new system is placed more on the characteristics of the mouthparts than on swimming leg segmentation patterns. One new genus, Eupolymniphilus, is established, based on Scambicornus finmarchicus. An analysis of the phylogenetic relationships between the families of the lichomolgoid complex is presented.

The developmental sequence of Argulus foliaceus (Crustacea: Branchiura)

We describe and illustrate the complete development of Argulus foliaceus L. A metanauplius is followed by nine juvenile stages. Eggs were detected in the thorax of the female at the 11th stage. Comparisons are made between the development of A. foliaceus and the other freshwater species of Argulus currently found in the UK.

A new genus and two new species of cave-dwelling Misophrioid copepods from the Balearic Islands (Mediterranean)

Speleophriopsis balearicus n. gen., n. sp., and Speleophria gymnesica, n. sp. are described from the flooded coastal karst of the Balearic Is. Two existing species of Speleophria are transferred to the new genus. Speleophriopsis scottodicarloi (Boxshall and Iliffe), new combination, occurs on Bermuda (Atlantic) and S. campaneri (Boxshall and Iliffe), new combination, in the Palau Archipelago (Indo-West Pacific). The type species of Speleophria is known only from caves on Bermuda. Both genera are noteworthy for displaying the most primitive condition known in copepods of the allobasis of maxilla (setal formula 5,3), and of the male antennule which, in Speleophriopsis n. gen., is geniculate but exhibits a 27-segmented condition. They inhabit cave waters with salinities in excess of 18‰., avoiding lower salinity inland groundwater habitats. A Tethyan relict status is proposed for both taxa.

Fossil Crustaceans as Parasites and Hosts.

Numerous crustacean lineages have independently moved into parasitism as a mode of life. In modern marine ecosystems, parasitic crustaceans use representatives from many metazoan phyla as hosts. Crustaceans also serve as hosts to a rich diversity of parasites, including other crustaceans. Here, we show that the fossil record of such parasitic interactions is sparse, with only 11 examples, one dating back to the Cambrian. This may be due to the limited preservation potential and small size of parasites, as well as to problems with ascribing traces to parasitism with certainty, and to a lack of targeted research. Although the confirmed stratigraphic ranges are limited for nearly every example, evidence of parasitism related to crustaceans has become increasingly more complete for isopod-induced swellings in decapods so that quantitative analyses can be carried out. Little attention has yet been paid to the origin of parasitism in deep time, but insight can be generated by integrating data on fossils with molecular studies on modern parasites. In addition, there are other traces left by parasites that could fossilize, but have not yet been recognized in the fossil record.

Parasites Gained: Alien Parasites Switching to Native Hosts

Abstract Three parasitic copepods new to the well-studied Mediterranean fauna are reported. Two of them, Mitrapus oblongus (Pillai, 1964) and Clavellisa ilishae Pillai, 1962, are of Indo-Pacific origin and are considered here to have co-invaded the Mediterranean through the Suez Canal on Erythrean (Red Sea) immigrant hosts. Both are reported here from native Mediterranean clupeid fish hosts; this is the first evidence of host switching of any metazoan parasites from Erythrean immigrants to native fish hosts. The third parasite, Nothobomolochus fradei Marques, 1965, was previously known from the Gulf of Guinea and the Arabian Gulf. Possible explanations of its presence on clupeid hosts in Egyptian waters off Alexandria are discussed. The parasite utilizes an Erythrean immigrant clupeid and a native Mediterranean species as hosts. This account provides evidence of parasite and host faunal mixing on an unexpected scale.

Gauchergasilus, a new genus for Ergasilus euripedesi Montú, 1980, an abundant parasitic copepod from the Patos Lagoon in southern Brazil.

Ergasilus euripedesi is redescribed from newly collected material of both sexes. A new genus, Gauchergasilus, is proposed, with Gauchergasilus euripedesi n. comb., formerly Ergasilus euripedsi Montú, 1980, as its type and only species. The new genus is characterised principally by the five-segmented antennule, the presence of a conspicuous barb on the concave margin of the claw of the antenna, the two-segmented endopod of leg 1 and the reduced fifth leg comprising two setae, one papillate. The male lacks the barb on the antennal claw but its other appendages are similar to those of the female, except for the maxilliped which is absent in females. The affinities of the new genus lie with the Acusicola group of genera.

Phylogeny within the Chondracanthidae (Poecilostomatoida, Copepoda)

The existing systematics of the Chondracanthidae is based predominantly on female characters and divides them into two subfamilies: Chondracanthinae and Lernentominae. Phylogenetic analyses using maximum parsimony were performed using 186 male and female characters. Different trees were generated when male and female characters were analysed separately. Differential weighting showed that the female characters were dominant but not to a great extent and subsequent analyses were run with both partitions combined. Different trees were generated depending on the character setting (unordered, ordered and irreversible‐up). Interestingly, a basal backbone comprising the same nine ingroup taxa was present in all of the trees, although the sequence of those taxa could differ. Constraining the two subfamilies to be monophyletic caused the tree length to be increased and the Templeton and Kishino–Hasegawa tests showed the constrained tree to be significantly different from the unconstrained. The two subfamilies are considered invalid and Lernentominae Oakley, 1927 is formally synonymized with Chondracanthinae Milne Edwards, 1840. The validity of the Pharodidae was tested similarly. Pharodes tortugensis, representing the family Pharodidae, was always recovered nested deep within Chondracanthidae. The Pharodidae Illg, 1948 is therefore synonymized with the Chondracanthidae Milne Edwards, 1840.