On the status of Arcitalitrus dorrieni (Crustacea: Amphipoda) on the island of Colonsay,Inner Hebrides

The presence of the landhopper Arcitalitrus dorrieni (Hunt) is reported on the island of Colonsay, Inner Hebrides. It is widely distributed there amongst deciduous leaf litter in forested areas but also occurs in bracken litter and scrub grassland. The species is an introduction from Australia, doubtless transported inadvertently among plants brought to the gardens at Colonsay House. It is, however, not restricted to the ornamental plantings but has colonized native woodland. Maximum population density recorded under leaf litter was 680 m². Amphipods avoid waterlogged or dry situations preferring to burrow in moist soil under litter from deciduous trees. Coniferous woodlands are more sparsely colonized. Rate of spread (minimum) from the original locus is calculated at c. 25 m/year. Arcitalitrus may prefer to eat sycamore leaves (cf. oak, beech). Ovigerous females are reported for May but no evidence exists for a release of young any earlier in the year. Immature amphipods seem to live more covert lives in the soil beneath the superficial litter layer. Eggs are relatively large and few in number. Amphipods may avoid ants but may have a mite living in phoretic or ectoparasitic association.     

Current status of an amphipod invader,Arcitalitrus dorrieni (Hunt, 1925), in Britain

The synanthropic landhopper Arcitalitrus dorrieni (Hunt) is largely restricted to the south-west of Britain although there are isolated populations outside this area. It has been recorded from 60 new 10-km squares since Harding and Sutton (1988 Harding, P. T and Sutton, S. L. 1988. The spread of the terrestrial amphipod Arcitalitrus dorrieni in Britain and Ireland: watch this niche!. Isopoda, 2: 7–10.  [Google Scholar]) last reviewed its distribution. Some of the new records, particularly in south Wales, could be interpreted as meaning that there has been range expansion in this time. However, the evidence is equivocal. It was not possible to explain the distribution of A. dorrieni in terms of association with native plant species. The main means of dispersal still seems to be synanthropic. Arcitalitrus dorrieni has retained a mainly coastal distribution, with penetration inland restricted to peninsular areas (with some notable exceptions, e.g. populations in London).     

Aspects of the life history and reproductive biology of the introduced terrestrial amphipod Arcitalitrus dorrieni (Hunt) at two sites in Co. Galway,Ireland

The reproductive biology of Arcitalitrus dorrieni (Hunt) was investigated over a period of 25 months at a deciduous and a coniferous forest site at Kylemore, Co. Galway, Ireland. The species has an annual, univoltine reproductive cycle with ovigerous females found throughout the year. Recruitment of juveniles begins in May–June with a peak of reproductive activity in August–September. The populations at each site show a bimodal size-distribution for most of the year, with a unimodal distribution in March, April and May. Mortality occurs exponentially, and the life-span is 20–22 months. Mean fecundity was 5·65 eggs per female and was dependent on female size, egg size and brood stage. Brood mortality was 37·5% at Addergoole and 29·8% at Tullywee Bridge.     

Notes on the occurrence of Talitrus dorrieni Hunt (Crustacea Amphipoda: Talitridae) in south-west England

Summary

The introduced amphipod crustacean Talitrus dorrieni is abundant in terrestrial localities on the Isles of Scilly, and has been found in three previously unrecorded localities in Cornwall. Although widespread on the islands, it is restricted to gardens and cultivated ground on the mainland. The origin of the colonies and the factors limiting their spread are discussed.     

Revision of the Amphipod (Crustacea: Stegocephalidae) genera Andaniotes Stebbing, 1897 and Metandania Stephensen, 1925

The amphipod (Crustacea: Stegocephalidae) genus Andaniotes Stebbing, 1897 currently comprises 11 species. Andaniotes abyssorum (Stebbing, 1888) is re-established as a valid species, and five new species are described. One species, Andaniotes islandica (Stephensen, 1925), is both re-established as a valid species and returned to its original genus Metandania Stephensen, 1925.     

Elevation of two eastern Atlantic varieties of Ampelisca brevicornis (Costa, 1853) (Crustacea,Amphipoda) to full specific rank with redescription of the species

Two species of Ampelisca, Ampelisca pectenata and Ampelisca cavicoxa, are studied here. These species were originally taken to be varieties of Ampelisca brevicornis, but they proved upon closer study actually to be different species. They are redescribed here in detail, and raised to the status of species. These two species have hitherto only been known to inhabit tropical Atlantic areas. Now for the first time they have been recorded on the French Atlantic coast, which shows that they have a wider geographical distribution than was previously assumed. Some biological data are also given which add to the knowledge available about this family of Amphipoda. Deux espèces d'Ampeliscidae sont étudiées dans ce travail, Ampelisca pectenata et Ampelisca cavicoxa. A l'origine, elles ont été décrites comme variétés de Ampelisca brevicornis, mais une étude détaillée montre qu'il s'agit d'espèces différentes. Elles ont donc étéentièrement redécrites et élevées au rang d'espèces. Ces espèces n'étaient connues jusqu'àprésent qu'en régions tropicales Atlantiques. Pour la première fois elles sont signalées sur les cô     

On Liljeborgia fissicornis (M. Sars, 1858) and three related new species from Scandinavia,with a hypothesis on the origin of the group fissicornis

The large and common Scandinavian amphipod Liljeborgia fissicornis (M. Sars) is split into four species: the deep-water L. caliginis sp. nov. and L. charybdis sp. nov., and the shallow-water L. fissicornis and L. ossiani sp. nov. The poorly known species L. polosi Barnard and Karaman, recorded from the deep Canadian Basin of the Arctic Ocean, is considered as belonging to the same group. All those northern species are completely devoid of eyes, while similar species from the Antarctic and sub-Antarctic continental shelf do have eyes. It is hypothesized that the group fissicornis, which is specific to cold waters, derives from ancestors living on the continental shelf of the Southern Ocean. These ancestors would have adapted to deep-sea environments, losing their eyes completely. Then they would have migrated northwards through the cold abyss, and reached the cold but shallow waters of the Arctic/sub-Arctic continental shelf, without redeveloping visual organs.     

Ultrastructure of the pereopodal dactyls in the family Phronimidae Dana, 1852 (Crustacea: Amphipoda: Hyperiidea)

Species of the Phronimidae were studied for the micromorphology of their pereopods. Novel structures were found on the dactyls and are described in detail. A hypothesis is advanced that these structures serve also for external digestion and absorption of the tissues of their gelatinous plankton hosts.     

A redescription of Cerapus tubularis Say, 1817, based on material of the first reviewer,S. I. Smith, 1880, (Crustacea: Amphipoda: Corophioidea)

Cerapus tubularis Say, 1817, type species of the genus, is redescribed, based on material used by the first reviewer (Smith, 1880). Because of confusion concerning the identity of C. tubularis, a neotype is selected. The genus is redefined, based on the type species.     

Anatomy of the alimentary canal of Parandania boecki (Stebbing, 1888) (Crustacea,Amphipoda, Stegocephalidae) from the Antarctic Ocean

The alimentary canal of Parandania boecki (Stebbing, 1888) has been investigated. Examination of gut contents shows that this species feeds on Cnidaria. The oesophagus, stomach and midgut are adapted to ingest and store large masses of soft food. The opening of the oesophagus is closed by a labral operculum and ‘double gate’ — like narrowings at the stomach entrance. The foregut is extremely enlarged and the funnel region is reduced. The midgut very probably is not connected to the foregut, and the resorption of food takes place only in the midgut caeca. The midgut forms a shallow, crescentic cavity over the midgut caeca.     

An introduced new species of Lecanoideus (Homoptera: Aleyrodidae) established and causing economic impact on the Canary Islands

Lecanoideus floccissimus sp. n. is described from material collected in the Canary Islands and Ecuador. A review of the economic impact of L. floccissimus in the Canary Is. is presented. The status of Lecanoideus Quaintance and Baker is discussed. Keys are provided to enable adults and puparia of L. floccissimus to be distinguished from Aleurodicus dispersus Russell, which is also established on the islands.     

Atlantic and Mediterranean species of the genus Andaniexis Stebbing (Amphipoda: Stegocephalidae)

The Atlantic and Mediterranean species of the genus Andaniexis Stebbing, 1906 (Amphipoda: Stegocephalidae) are reviewed, and three new species are described. The species Andaniexis abyssi (Boeck, 1871) which previously was considered a widely distributed species (from Baffin Bay to both Spitzbergen and the Skagerrak), is here divided into three species: Andaniexis abyssi s.str., Andaniexis gracilis n.sp. and Andaniexis lupus n.sp. These species, together with Andaniexis mimonectes Ruffo, 1975, all have allopatric distributions. This is especially evident in northern Norway, where A. abyssi has its northernmost limit: A. abyssi is found in Solbergfjorden (69°10′N), while Andaniexis lupus is found in the adjacent fjord Malangen (69°30′N, the southern limit of this species along the Norwegian coast). Andaniexis eilae n.sp. is described from Iceland. This species is not closely related to the other North Atlantic species of the same genus.     

A new species of Ischyrocerus (Crustacea: Amphipoda) from Ireland,with a review of Ischyrocerus anguipes and Ischyrocerus minutus from the North-East Atlantic

A new species of ischyrocerid amphipod, Ischyrocerus fractus sp. nov., is described from south-west Ireland. An examination of material from the Sars Collection at the Zoologisk Museum, Oslo, has confirmed that Ischyrocerus minutus Sars, previously placed as a synonym of Ischyrocerus anguipes Krøyer, is a valid species and is widespread in the British Isles, while I. anguipes is Arctic/boreal in distribution.     

Apodidymochelia,a new genus of gammaridean amphipod from the tropical Atlantic Ocean (Crustacea: Amphipoda: Didymochellidae)

Apodidymochelia castellata, new genus, new species is the second genus and fourth species in the rare and poorly known family Didymocheliidae. Apodidymochelia is separated from Didymochelia primarily on mandible structure. This record extends the known range of the family into the Atlantic Ocean.     

A new species of amphipod of the genus Neomegamphopus (Crustacea,Amphipoda, Neomegamphopidae) from Rodrigues,Indian Ocean

A new species of Neomegamphopus Shoemaker is described from Rodrigues, Indian Ocean. The systematics of the Neomegamphopidae from the Indian Ocean is discussed and a key to the species from that ocean is provided.     

Notes on the occurrence and biology of Xenoclarias Greenwood (Siluriformes: Clariidae) in Lake Victoria,East Africa

Summary

Xenoclarias inhabits the deeper (>50 m) waters of Lake Victoria. Specimens captured in a bottom trawl ranged in size from 10–22 cm TL (mode, 15–18 cm) and females grew to a larger size than males. Length-weight relationships between sexes were different only in the Kenya waters and resulted in significantly different KTL. Based on gonadal stages, Xenoclarias matured between 14–16 cm (age 1). Fecundity of 6 specimens (Stage VI) ranged from 744–1357 (mean 1009) and egg size from 1·45 to 1·98 mm (mean 1·79 mm).

Based on gravid and spawning females, Xenoclarias spawned prior to the rainy season (January–March) in Kenya and Uganda waters. During periods of increased reproductive activity females were consistently more numerous in samples (2:1) than males. Local meteorological and hydrological conditions may explain the apparently different spawning season in Tanzania waters of the Lake. This genus of small fish is not affected by the artisinal gillnet fishery but may be by the expansion of a bottom trawl fishery in Lake Victoria.     

Patterns of artificial avian nest predation by introduced rats in a fragmented laurel forest (Tenerife,Canary Islands)

The importance of introduced rats as damaging factors on island biotas is globally recognized. The predation of artificial avian nests by Ship rats (Rattus rattus) in fragmented laurel forests in Tenerife (Canary Islands) was explored. The influence of road edge, patch type, and position (ground versus tree) on nest survival in two forest remnants differing in conservation degree, were assessed using failure‐time analysis. Overall, nest predation was greater in the preserved than in the disturbed remnant. Nest predation also differed among and within patches, variation being greater within the disturbed remnant. The probability of nest failure was higher at the interior than along the road edge in both remnants, but the road edge effect on nest predation was more intense in the disturbed remnant. Predation pressure was higher in patches of mature, closed canopy or dense understorey with stump sprouting. Ground nests were predated at higher rates than tree nests at any location. These results contrast with other nest predation studies in fragmented landscapes where forest edges rather than the interior are more frequently used by predators. Predatory activity by rats seems negatively affected by forest disturbance and road edge effect. Overall, artificial nest predation patterns by rats confirm a potential predation risk for the avifauna of the Canarian laurel forest. This should be considered in implementing conservation management programmes.