Lembos Websteri Research Articles

Biodiversidad de los anfípodos bentónicos (Peracarida: Amphipoda) asociados a macroalgas de Puerto Progreso, Yucatán, México

Biodiversity, new species records, geographic distribution range extensions, and invasive species of benthic amphipods from Puerto Progreso, Yucatán, Mexico, were analyzed. A total of 39 species, belonging to 21 genus, 16 families, and 2 suborders Gammaridea and Corophiidea, were identified. The species Caprella equilibra Say, 1818, Dulichiella lecroyae Lowry and Springthorpe, 2007, Laticorophium baconi (Shoemaker, 1934), Lembos websteri Bate, 1857, Leucothoe ashleyae Thomas and Klebba, 2006, Leucothoe barana Thomas and Klebba, 2007, Leucothoe garifunae Thomas and Klebba, 2007, and Nasageneia yucatanensis Ledoyer, 1986, represented extensions of the previously reported geographic distribution into the southern Gulf of Mexico; also, the species Bemlos barnardi (Ortiz and Nazábal, 1988) represents a new record for the the gulf. Ampelisca schellenbergi, Ampithoe longimana and Monocorophium acherusicum were recognized as invasive species, and Ampithoe ramondi, Ericthonius brasiliensis, Plesiolembos rectangulatus and Stenothoe gallensis as potentially invasive species in this study. These results updated the checklist of benthic amphipods from the offshore Yucatán state continental shelf up to 62 species, whilst that from southern Gulf of Mexico increases to 94.

Amphipod community associated with invertebrate hosts in a Mediterranean marine cave

The present study explored the amphipod communities associated with the dominant host invertebrates inhabiting a marine cave of South Spain in order to describe their species composition and distribution patterns. Although they play a key role in the structure of mobile epifaunal communities inhabiting most rocky reef ecosystems, this component of marine caves communities has often been overlooked. Colonies of six sessile species were collected: Astroides calycularis, Parazoanthus axinellae, Pentapora fascialis, Aldeonella calveti, Filograna implexa, and Ircinia fasciculata. In each sample the mobile epifaunal community (mainly focusing on the amphipod group) was characterized, with Arthropoda and Amphipoda being the dominant phylum and order, respectively. Among amphipods, the gammarid Lembos websteri and the caprellids Phtisica marina and Pseudoprotella phasma were the most abundant species. The endangered coral Astroides calycularis showed the most distinctive amphipod community and multivariate analysis highlighted the existence of significant differences in the amphipod assemblages among invertebrate hosts in the cave. However, no host-specific species were found. Benthic hosts inside the cave are mainly used as a refuge by amphipods and all the sessile species studied seem to play an equivalent facilitation role. To what extent changes in the composition of sessile species may affect other associated species was also discussed.

Spinning a Marine Silk for the Purpose of Tube-Building

Amphipod silk is a fibrous, self-secreted, adhesive substance employed in tube-building by amphipod species within the Corophiidea, Ampeliscoidea and Aetiopedidea. In the present study we provide a detailed characterisation of a novel, marine-based silk production system situated in pereiopods 3 and 4 in the corophioid Crassicorophium bonellii and the aorid Lembos websteri. The silk material is a mixture of protein and mucopolysaccharides. Ultrastructural and histological analyses revealed that silk in both species is produced in several rosette-type glands, presumed to be of two different types. These glands are distributed among all limb articles apart from the coxa but mainly in the basis and merus of pereiopods 3 and 4. Secretion commences in the basis and a thread-like secretion product leaves the glandular pereiopod through a cuticular pore near the dactylar tip. The silk’s physical and chemical properties most likely change while moving through the dactylar duct, which subdivides into several small ductules and terminates in a spindle-shaped chamber. This chamber, which communicates with the exterior, may be considered a silk reservoir in which the silk appears fibrous. For the first time an independently evolved, marine arthropod silk processing and secretion system is described.

The effect of depth and sediment type on the spatial distribution of shallow soft-bottom amphipods along the southern Portuguese coast

The present study provides updated information on amphipod assemblages of the southern Portuguese coast, the most south-western part of continental Europe. The influence of depth and sediment type on the spatial distribution of shallow soft-bottom amphipods was tested by means of univariate and multivariate methods. Samples were collected down to 40 m depth within areas ranging from very fine sand to gravel. The ratio between density and diversity was found to increase with depth and from coarser to finer sediments. Both physical variables tested were found to play a major role in structuring amphipod assemblages. However, some dominance of depth was evident as samples were mainly separated according to this variable. Moreover, while only 15 taxa were common to all depth levels, 35 were collected from all sediment types. Both depth and sediment type may override the potential effects of geographical location, as samples from different areas along the southern Portuguese coast were biologically related. A peculiar habitat was sampled in this study: a maerl bed, which was confirmed to be a hotspot of density. Nevertheless, this habitat did not harbor a distinct amphipod assemblage but some taxa such as Caprella spp., Lembos websteri, lysianassids and Gammarella fucicola were preferentially collected there. The biogeographical analysis pointed out the occurrence of 8% of Mediterranean endemic species, confirming the influence of the Mediterranean Sea beyond the Strait of Gibraltar, and the Atlantic-Mediterranean feature of the amphipod fauna of this geographically relevant area. The present results support the need to interpret the spatial distribution patterns of marine species in relation to the combined effect of depth and sediment characteristics.

Trophic importance of Laminaria hyperborea to kelp forest consumers and the importance of bacterial degradation to food quality

The nutritional value of kelp Laminaria hyperborea (Gunn.) Foslie and the importance of bacterial degradation in making kelp available to consumers were tested by no-choice feeding experiments. Fresh and dead kelp material degraded in situ was sampled. In the laboratory, fresh kelp was degraded for 3, 14 and 44 d by kelp associated bacterial communities under aerobic and anaerobic conditions. The fresh and degraded kelp products were fed to the kelp associated amphipods Jassa falcata, Lembos websteri, Ampithoe rubricata and Gammarus locusta and the gas- tropod Rissoa parva. None of the amphipods tested could survive or grow on fresh kelp, but bacterial degradation decreased the C:N ratio and the phlorotannin content and made kelp available as food. In contrast, the gastropod survived on both fresh and degraded kelp. 13 C: 12 C and 15 N: 14 N isotope analysis of fauna and possible food items sampled in the field suggested that kelp derived particulate organic matter (POM) is an important food source for kelp epifauna.

A comparative study on the tubes and feeding behaviour of eight species of corophioid Amphipoda and their bearing on phylogenetic relationships within the Corophioidea

Observations are presented on mouthpart functional morphology, and on feeding, grooming and defaecatory behaviour of eight species of corophioid Amphipoda, viz.Corophium bonnellii,Lembos websteri,Aora gracilis,A. spinicornis,Gammaropsis nitida,Ericthonius punctatus,Jassa falcataandJ. marmorata. These data are considered in relation to tube structure and amphipod posture in relation to the tube. All these species occupy double-ended cylindreical tubes made from ‘amphipod silk’ secreted by the third and fourth preraeopods, incorporating sediment and other debris to varying degrees. Uniquely among this set of species, however,E. punctatushas a tube that is architecturally distinct. It tapers along its length and has a distinctive oblique main entrance at its widest end. This end is used preferentially. The other species studied use either opening with equal facility. Such a feature is adaptive in facilitating deployment of the antennae and shielding the head ofE. punctatus.Two groupings of species are propose: group A which feed inside their tube using pleopod-induced through-tube currents, and group B which feed outside or at the entrance to their tube using external water currents. Group A includesC. bonnellii,L. websteriand theAoraspecies. Group B includesE. punctatusand theJassaspecies.Gammaropsis nitidaexhibits traits from both groups, adding weight to its perceived status as a genus representative of the stem corophioid. The ischyrocerid habit of externalizing food-gathering may be regarded as the first step along an evolutionary line leading to the rod-building podocerid types and ultimately towards the caprellids. All species examined show a degree of flexibility in their feeding habits which helps to explain the success of this taxon, which has radiated into a great diversity of aquatic biotopes.

Karyological studies in amphipoda (Crustacea)

Abstract A survey of chromosome numbers of amphipods is presented on the basis of literature data and new observations. Chromosomes of8 amphipod species have been investigated: Aora gracilis (n = 4, 2n = 8); Atylus swammerdamei (n = 12, 2n = 24); Jassa marmorata (n = 6, 2n = 12); Lembos websteri (n = 18, 2n = 36); Halirages fulvocinctus (2n = 32); Haustorius arenarius (n = 20, 2n = 40); Hyale prevosti (n = 25); Hyperia galba (2n = 126). Aora gracilis has the smallest chromosome number and Hyperia galba the highest recorded in amphipods. Methodological problems and phylogenetic implications are discussed.

Biometry of brooding in seven species of amphipod (Crustacea) from the Clyde Sea area

Brood size was found to be correlated linearly with female body length in all species studied, except Ampelisca macrocephala, which is usually a single brooded species. Of the six multi-brooded species, Lembos websteri, Stegocephaloides christianiensis, Echinogammarus pirloti and Gammaropsis nitida produced small numbers of large eggs in the winter and large numbers of small eggs in the summer. In Bathyporeia pilosa larger numbers of smaller eggs were produced by the overwintering generation. In Corophium bonnellii, both maximum and minimum brood sizes were produced by the summer generation. The largest broods relative to female body size were produced by the smaller species. In L. websteri, C. bonnellii and B. pilosa mean female size was smaller in the summer than the winter generation.

The breeding cycles of females of seven species of amphipod (Crustacea) from the Clyde Sea area

The life cycles of females of seven species of amphipod were determined from fortnightly sampling of sites in the Clyde Sea area. Three species, Lembos websteri, Corophium bonnellii and Bathyporeia pilosa, exhibited semi-annual life cycles with an overwintering generation producing a shorter-lived summer generation. The deep-water species Stegocephaloides christianiensis exhibited continuous breeding, as did the sublittoral species Gammaropsis nitida. The other deep-water species, Ampelisca macrocephala, exhibited a biennial life cycle. The littoral species Echinogammarus pirloti exhibited a reproductive cycle that was closely correlated with the abundance of its food supply. With the exception of E. pirloti and S. christianiensis, the reproductive cycles of the species studied were closely correlated with photoperiod. Environmental temperature was of secondary importance to seasonal variation in breeding in all species. A female bias in the sex ratio was observed throughout the year in four of the seven ...

Breeding periodicity and sex ratios in epifaunal marine amphipoda in Lough Hyne, Ireland

Thirteen species of amphipod were recorded from sponges and associated biota, notably algae and tunicates, in Lough Hyne (Ine), south-west Ireland. The sex ratio rarely approached unity in any species. No male Corophium bonnellii were collected. Mature male Lysianassa ceratina were not collected between late July and early September. Ovigerous females occurred throughout the year in five species. Lysianassa ceratina had the most restricted breeding period (May to September). Breeding activity, based on this criterion of reproduction, was generally greatest between April and July, but this period was extended in some species. A secondary autumn peak in breeding activity was recorded in four species. A comparison between the data from the present study and those from a similar study in Scotland suggests that in the case of two of the species, Corophium bonnellii and Lembos websteri, egg production throughout the year may be related to differing summer maximum temperatures.

Tube-emergence behaviour in the amphipods Lembos websteri Bate and Corophium bonnellii Milne Edwards

The complete emergence from their tubes of the amphipods Lembos websteri Bate and Corophium bonnellii Milne Edwards has been the subject of laboratory investigation in Scotland. Few animals left their tubes during the day. Nocturnal emergence was clearly more frequent, but only in male Lembos websteri was it at all common. Both emergence onto the outer surfaces of Latninaria holdfasts (within which tubes are constructed) and swimming were rarely observed in this species and may be regarded as adaptations to life in wave-exposed habitats. Experimental evidence is presented which suggests that male L. websteri vacate their tubes at night to seek a new female partner. The seemingly parthenogenetic species Corophium bonnellii has no such tube-emergence requirement to facilitate reproduction.

The feeding habits of the amphipods Lembos websteri Bate and Corophium bonnellii Milne Edwards

The gut contents of both Lembos websteri Bate and Corophium bonnellii Milne Edwards include detritus and sand grains. Lembos websteri collected from Laminaria holdfasts also contain strands of filamentous algae although Corophium bonnellii do not. In addition, macroalgal fragments and naviculoid diatoms are present, more often in Lembos websteri than in the guts of Corophium bonnellii. Occasionally, in animals collected from a sheltered algal turf, arthropod appendages may also be observed in the gut of Lembos websteri. The size of particles consumed by Lembos websteri is larger than in Corophium bonnellii. Feeding in both species is primarily by filtration but a variety of other methods may be used, including deposit-feeding, consumption of food of animal origin (including the species' own eggs), and consumption of tube material. These alternative techniques are brought to bear increasingly in poor feeding conditions. The behavioural sequences involved in these activities are described in detail and food preferenda related to the nutritional state of the animals. Defaecation in Lembos websteri (males and females) is normally followed by immediate refection of the faecal pellet but again is more noticeable when food is scarce. Gut-residence time in both species is ≈ 2 h at 13–15 °C. The proposition is made that Corophium bonnellii is a more efficient small-particle filter-feeder than Lembos websteri and that as such, it has met no evolutionary requirement to recycle its faeces (large particles) in the manner of L. websteri. Lembos, on the other hand, having a very “plastic” feeding repertoire appears to be better adapted to withstand periods of low food availability. The larger particles on which L. websteri feeds will be scarcer and will require more turbulence to keep them in suspension and even at exposed localities where L.websteri is more common, periods of calm occur, so flexibility in food-gathering technique is clearly advantageous. The more efficient small particle filter-feeding technique of Corophium bonnellii is well suited to a life in sheltered waters, where only the smallest particles remain in suspension for long periods, which is so typical of the genus.

The biology of brooding in the amphipods Lembos websteri Bate and Corophium bonnellii Milne Edwards

Behavioural aspects of the brooding biology of the amphipod crustaceans Lembos websteri Bate (gonochoristic) and Corophium bonnellii Milne Edwards (parthenogenetic?) were studied at Millport, U.K. Brood survival was better in moving than in still water, with C. bonnellii broods generally surviving better than those of Lembos websteri. Hatching times were ≈ 10 days in both species (at ≈ 17°C). Once hatched, young generally spent < 1 day in their mother's marsupium. Ovigerous female Corophium bonnellii manipulated eggs in the brood pouch by “elbowing” movements of the first gnathopods and can remove eggs and eat them using these limbs. C. bonnellii has a more open mesh brood pouch than Lembos websteri and eggs may be lost accidentally. Such “lost” eggs can be replaced by the mother. Egg loss and replacement was never observed in L. websteri. “Replacement” of eggs of one Corophium bonnellii by those from another occurred, but eggs from a different species were not accepted. All eggs offered to Lembos websteri were eaten; Corophium bonnellii ate eggs (particularly Lembos eggs), but less often. Hatching in both species involved rupture of the egg membrane, probably by the telson spines, and was aided by pleonal flexure. Hatchlings were active in the brood pouch, feeding on detritus from a variety of sources. They did not appear to moult while in the marsupium. Irrigation of the brood by the female was achieved by pleopod beating and oostegite flexure. Brood release in L. websteri lasted < 1 day at both 16.5 and 19.5 °C, and was quickly followed by the female moulting < 1 day later. In Corophium bonnellii the female moulted > 2 days after brood release. Hatchings mostly emerged unaided by the mother. Premature hatchling loss could be rectified in C. bonnellii by the mother assisting reentry of the hatchling into the marsupium using gnathopods. Brood pouch reentry by “full-term” hatchlings was often observed, but only rarely did this occur after hatchlings had vacated the maternal tube; it was not assisted by the mother. Emergent young C. bonnellii sometimes resided in the maternal tube for only a matter of minutes; Lembos websteri stayed rather longer, usually < 1 day. Emerged hatchling L. websteri clustered inside the maternal tube in proximity to the mother rather than to the male attendant on her next moult (for fertilization of her next brood). Such hatchlings fed on detritus in the maternal tube, even taking material from the mother's gnathopods. They were never seen to take food from the male. Eviction of young from the maternal tube by the mother could be, but was not always, active. Female Corophium bonnellii frequently hindered the activity of young in the maternal tube. The differences in brooding biology between these two species are adaptive when viewed against differences in 1. (1) water movement regimes of their respective habitats 2. (2) feeding habits 3. (3) reproductive behaviour (mating vs. nonmating) of the adults.

The life histories of the amphipods Lembos websteri Bate and Corophium bonnellii Milne Edwards in kelp holdfasts

The life cycles of Lembos websleri Bate and Corophium bonnellii Milne Edwards are based on two generations per year. Eight cohorts have been identified in Lembos and nine for Corophium, each of which has a different longevity. In Lembos the summer generation proper lives ≈ 5–7 months whilst cohorts of the overwintering population may live up to 11.5 months. Males do not live as long as females, their longevity being ≈ 11% less in summer and 5% less in winter. C. bonnellii is parthenogenetic. Its summer generation lives ≈ 5 months and its winter generation 8–10 months. Corophium thus has a shorter life span than Lembos. It also grows faster. Growth is severely inhibited overwinter (but less so in Corophium) and picks up in spring. Year to year variations in timing of reproductive events may be related to temperature differences, sea state, and food supply. Population data for 1974 and 1975 were, however, generally very similar. Ovigerous females are present all the year in Lembos websteri but were never found in January in Corophium bonnellii. Egg-laying behaviour is described. Brood size is linearly related to maternal length in both species. A size-independent index of fecundity shows clear seasonal variation, with peak fecundity in summer. Minimum size of egg-bearing females is also a function of temperature in both species. A semi-lunar rhythmicity of brood production at summer temperatures is reported. Brood mortalities of ≈ 25–30% were found in both species which seemed unrelated to maternal size but which may (in Lembos) be seasonally variable (lower in winter). Egg size is similar in both species and egg volume more than doubles during development from Stage I to Stage IV. Corophium bonnellii eggs are bigger and individual female reproductive effort is higher than in other Corophium species. Corophium sometimes carried the ciliate Conidophrys on the basal segments of its antennae. Occasional endoparasites, namely cercariae and encysted metacercariae, were noted. Mortality due to fish predation was established to occur, the clingfish Apletodon microcephalus (Brook) and the sea snail Liparis liparis (L.) being important amphipod consumers.

Turbidity and kelp holdfast amphipoda. I. Wales and S. W. England

Analyses are given of a collection of over 65,000 amphipods derived from kelp holdfasts surveyed around Wales and S.W. England. Faunal affinity is predominantly biased latitudinally, warmwater elements being confined to the extreme southwest. Total amphipod density is related to holdfast weight. There are no significant differences in amphipod density with differences in wave exposure or turbidity. Standardized density is, however, higher in west coast than in east coast holdfasts. Diversity is lower in turbid waters due to the increased dominance of a few species. The distribution, population structure, and fecundity of the previously implicated turbidity-susceptible species, Lembos websteri Bate and Corophium bonnellii Milne Edwards are examined in the light of new ethological information. Supporting and conflicting data are examined and mechanisms are suggested to show how suspended inorganic particles could be directly detrimental to both species. In addition, indirect effects involving climatic fluctuation and competitive interactions, particularly with C. sextonae Crawford emend. Hurley and Jassa falcata (Montagu) cannot be excluded.

Tube building by the amphipods Lembos websteri Bate and Corophium bonnellii Milne Edwards

Lembos websteri Bate and Corophium bonnellii Milne Edwards are tubicolous. The morphology of tubes collected from Laminaria holdfasts is described and contrasted with that of tubes built amongst filamentous algae in a wave-sheltered environment. In both species tube length is a function of animal length. Corophium build tubes with openings raised above the substratum more commonly than Lembos, and will construct mats of tubes away from solid surfaces; Lembos tend to build against solid surfaces. Tube construction appears to depend upon the ‘knitting’ activity of the first two pairs of peraeopods, utilizing a secretion containing acid and sulphated mucopolysaccharides. The process of tube construction on substrata of known granulometry and the morphology of tubes built in the laboratory are described. The burrowing capabilities of both species are compared. On sand, Lembos tend to build on the sediment surface, whilst Corophium tend to burrow into the substratum. Corophium begin tube building after transference to a new situation much sooner than Lembos, with female Lembos starting to build sooner than male Lembos, Corophium can build a covering tube in < 15 min. In the absence of extraneous material, both species line glass tubes with a meshwork of mucoid filaments. In empty dishes, mucoid tubes are rarely built. The ability of Lembos to colonize wave-exposed sites may be related to its preference for more sheltered spaces within kelp holdfasts.