Biodiversity of nematodes in the Western Indian Ocean (WIO): taxonomy and assemblages

During the Netherlands Indian Ocean Program (NIOP) 1990-1995, benthic sampling was carried out to assess among other things, meiofauna densities, sediment community oxygen consumption and nematode assemblages. Four transects were sampled along the Kenyan coast in the Western Indian Ocean (WIO), from north to south: Kiwayu, Tana, Sabaki and Gazi. Samples were taken during two seasons: South East monsoon in June/July and the onset of the North East monsoon in November/December at depths: 20m, 50m, 500m, 1000m and 2000m. The samples were taken using a box core or lander. From each box two subsamples were taken to a depth of 5 cm using a plastic core 2.6 cm internal diameter. The two sub-samples from each box were mixed and fixed in hot, 4 % formaldehyde. In the laboratory, they were centrifuged in Ludox and nematodes were separated and enumerated. Between 100-200 nematodes were picked and processed using standard methods for slide preparation. They were then identified to genera level. Genus composition and distribution in the transects, in the two seasons and in depth were studied. Genus diversity was estimated using Hills diversity numbers (N0, N, N2, H’). From some selected families (Chromadoridae, Comesomatidae, Microlaimidae and Molgolaimus), the nematodes were identified to species level and where well represented they were described. For the selected families (Chromadoridae, Comesomatidae, Microlaimidae and Molgolaimus), genera and species composition and distribution were studied in the two periods, four transects and in depth. Species diversity was estimated using Hills diversity numbers and Hierarchical diversity. Environmental data from the same area (WIO) were obtained from published work or unpublished data analysed in other institutes. This included sediment community oxygen consumption (SCOC), DNA:RNA ratio, oxygen concentration and saturation, organic carbon, C:N ratio and sediment composition. Species description: from the three families, 42 new species were described and from 13 known species additional information provided. Of the 55 species described an average of 75 % of the nematodes were new. From Chromadoridae, 68 % were new species, Molgolaimus had 100 % new species, from Microlaimidae, 89 % were new species and from Comesomatidae, 75 % were new. This means that a lot of nematodes especially from the tropics are still not described both from the sublittoral and deep sea. Nematode density: nematode densities were highest at the shallowest stations (20m) which recorded 927 and 1350 ind/10cm2. At 50-2000m depth the density was 112 -669 ind/10 cm2. The low nematode density compared to the temperate region was associated to low food availability. The general trend in all transects was high nematode density at shallow depth which decreased upto 1000m, then increased slightly or decreased slightly upto 2000m. This trend was similar to the trend in oxygen concentration, and therefore oxygen was thought to be influencing nematode density. Nematode composition (in Transects and two periods): a total of 36 families were identified in June/ July and 38 families in Nov/Dec. The most dominant families were Xyalidae, Monhysteridae and Comesomatidae. Some temporal variation in family composition was observed in that Comesomatidae and Linhomoeidae had a higher relative abundance in June/ July compared to Nov/Dec, and Microlaimidae and Chromadoridae had a higher relative abundance in Nov/Dec compared to June/July. In June/July a total of 199 nematode genera were identified while in Nov/Dec 217 genera were identified. In June/July, 19 genera had at least 1.0 % which contributed to 50 % of the community. In Nov/Dec, 20 genera had at least 1.0 % and this contributed to 50 % of the community. The most dominant genera in both periods were Monhystera (7 %, 8 % respectively), Halalaimus (6 %, 5%), Sabatieria (5 %, 4%), Daptonema (4 %, 6 %) and Acantholaimus (3 %, 5 %). There was some temporal variation in genera distribution between the two periods in that during June/July Terschellingia had a higher dominance compared to Nov/Dec and in Nov/Dec Acantholaimus and Molgolaimus had a higher dominance compared to June/July. In the transects, the most dominant genera were similar, although the relative abundance varied from transect to transect. Some of the most dominant genera common in all transects were Monhystera (4-10%) and Halalaimus (4-6 %). Some temporal variation was observed in that again Terschellingia was the most dominant genus in only Sabaki in June/July and in the Training transect in Nov/Dec, Microlaimus was the second most dominant genus. Species (genus) diversity was estimated using Hills diversity numbers. Average diversity (Hill’s Ni) was lower in June/July (24) compared to Nov/Dec (26). In the transects, diversity was lowest in Sabaki in both periods (19 and 20 respectively). In Jule/July, genus diversity was highest in Tana (27) while in Nov/Dec it was highest in Training transect (29). Ecological groups (Depth): on the basis of nematode genera composition, TWINSPAN and DCA analysis identified four groups of stations. The four groups were A- stations at 20m, 50m and 200m depth, B- stations at 20m and 50m C- stations at 500m and 1000m and D- stations at 1000m and 2000m This shows that depth had a lot of influence on structuring the nematodes composition in the area. Besides depth, nematode composition may have been influenced by sediment composition. Station groups A and B were at nearly the same depths but group A stations had sediment with high sand content and very low silt content. Further analysis of the nematodes was therefore done with the groups separated on the basis of depth but group A and B were kept separate. Therefore, the following groups were considered for further analysis; 1 -A 2-B 3 -500m stations 4 -1000m stations 5 -2000m stations. Nematode composition in the ecological groups: in all five ecological groups, the most dominant families were Xyalidae (8-21 %), Monhysteridae (3-32 %), Chromadoridae (6-10 %), Comesomatidae (4-17 %) and Oxystomatidae (6-9 %). The most notable trend in family distribution in the groups was the increase in relative abundance of Monhysteridae and the decrease of Xyalidae from group 1 to 5. The two shallow station groups had also high relative abundances of Linhomoeidae (12 %) in group 1 and Microlaimidae (13 %) in group 2. Some of the most dominant genera were common in all the five groups of stations, although their relative abundance differed from group to group. The dominant genera were Monhystera, Sabatieria, Halalaimus, and Daptonema. Acantholaimus was also dominant but it was completely absent in group 1. The shallow station groups, 1 and 2, were distinctly different from the deeper stations in some of their dominant genera, while the deeper station groups 3, 4 and 5 had nematode genera composition that shifted gradually with depth from 3 to 5. In group 1, the most dominant genera were Daptonema (11 %), Terschellingia (9 %), Dorylaimopsis (7 %) and Halalaimus (4 %). In group 2, the most dominant genera were Microlaimus (6 %), Halalaimus (6 %), Daptonema (5 %) and Sabatieria (4 %). Terschellingia and Dorylaimopsis were typical for group 1 and Microlaimus was one of the typical genera for group 2, where they had higher relative abundance than in any other. The deeper station groups were characterised by varying proportions of Sabatieria (6 %, 7 %, 2 % respectively), Monhystera (5, 9, and 23 %), Acantholaimus (4, 5, 8 %) and Molgolaimus (4, 4, 2 %). Halalaimus had a high relative abundance in all the five groups (4, 6, 6, 6, 5 %). Genus diversity in the station groups was compared using Hills diversity numbers. It was highest in group 2 and 3 intermediate in group 1 and 4 and lowest in group 5. All indices indicated a low diversity at group 1, increased to a maximum at group 2 or 3 and then decreased to a minimum in group 5 stations. This trend in diversity followed the same trend as the average sediment sand content in the station groups. It appears like sediment sand content had an influence on nematode diversity. Besides, Spearman Ranked Order correlation (SROC) showed a significant positive correlation between genus diversity and sand and a negative correlation with silt content in the sediment. Genus diversity was a function of high number of genera combined with low dominance. In group 2 and 3, with the most diverse nematode communities, at least 129 and 121 genera (respectively) had 0.1 % relative abundance, and 50 % of the population was made up by 22 genera in group 2 and 19 genera in group 3. In group 1 and 4, at least 110 genera had relative abundance of 0.1 %, and 50 % of the community was made up by 15 genera in both groups. In group 5, only 94 genera had 0.1 % relative abundance and 50 % of the population was made up by only 10 genera. Temporal variation was observed in nematode composition and diversity in the deep station groups. In the 500m stations higher genus diversity (using Hills Ni) was observed in June/July (32) compared to Nov/Dec (28). In the 2000m stations, higher genus diversity was observed in Nov/Dec (19) compared to June/July (18). Trophic composition Wieser’s classification of nematodegenera into, selective deposit feeders (la), non-selective deposit feeders (lb) epistrate feeders (2a) and predator/omnivore feeders (2b) were analysed in the ecological groups for trophic composition. Ecological groups 1 and 2 had almost similar trophic composition (la, lb and 2a: 28-33 %), ecological groups 3 and 4 had almost similar (la was dominant with 38 %) and group 5 was close to the last two albeit some minor differences (lb was dominant with 41 %). In all the ecological groups, trophic category 2b contributed to less than 10% of the nematode population. Species distribution: Chromadoridae :19 genera and 81 species were identified. The most dominant genera were Acantholaimus (49%) followed by Dichromadora (14 %) and Actinonema (10 %). Except for Acantholaimus that increased in relative abundance with increase in depth, most other genera of the Chromadorids were more dominant at the shelf than on the slope stations. A high number of morphospecies (species identified on the basis of qualitative morphological characters alone without measurements because sometimes only juveniles were available) of Acantholaimus (38) were recorded leading to a high species richness in the slope stations. However, the number of genera was higher in the shelf than the slope stations. All transects recorded higher diversity in Nov/Dec compared to June/July period. The Northern most transect had higher species diversity compared to the southern one, although a south-north trend was not quite clear. Generally, species diversity seemed to increase with increase in depth while genera diversity showed the opposite trend. This kind of a trend may have been mainly due to the distribution of Acantholaimus suggesting that Acantholaimus is very important in this area. Comesomatidae 12 genera and 44 species were identified in the family Comesomatidae. The family was dominated by the genus Sabatieria (40%) followed by Cervonema (20 %) and Dorylaimopsis (15 %). The first two were the most dominant in the deeper station groups while the last one was dominant at the shallow station group 1. The number of genera was highest in station groups 1 and 3 while the number of species was highest in group 3 and 4 stations. Hills diversity (Ni) index showed that November/ December period had a higher species diversity compared to June/July period. Species diversity was highest in group 3 station and decreased with increase in depth. Among the two shelf stations, group 1 had a higher diversity than group 2. Thus, most Comesomatidae had a preference for fine sand with high silt content rather than course sand. In November/December higher diversity was observed in Kiwayu compared to Gazi while in June/July, Gazi had a higher diversity compared to Kiwayu. Microlaimidae + Molgolaimus 9 genera and 41 species were identified. The most dominant genera were Microlaimus (35 %) and Molgolaimus (35 %). Molgolaimus had a higher relative abundance during the first campaign (in June/ July) than in the second campaign while Microlaimus had a higher relative abundance in November/December compared to June/July period. Microlaimus dominated the two shallow station groups 1 and 2 while Molgolaimus dominated station groups 3 and 4. Overall diversity was highest during November /December compared to June/July. In June/July campaign, Kiwayu had the highest diversity index while in November/December, the diversity index increased from North to South. The diversity index N0 was highest in group 3 stations and decreased with depth while Ni was highest in group 2 stations and decreased with increase in depth. Among the Microlaimidae, most genera and species appear to prefer coarse sands rather than sand with high silt content. This work presents the first comprehensive study of free living nematodes of the Indian Ocean

The mangrove forest as a feeding ground and nursery habitat for the ichthyofauna: Mida Creek in Kenya

peer reviewedMangrove forests are among the most productive ecosystems, sustaining both terrestrial and aquatic fauna (Kathiresan, 2011). They are important to coastal fisheries by providing foraging and hiding places for commercially valuable fishes (Tomlinson, 1986; Rönnbäck 1999). This research investigated the fish assemblage of Mida Creek (Kenya, East Africa) as well as the presumed feeding and nursery functions of the area for the ichthyofauna present. This explorative study contributes to a Kenyan-Flemish project in which scientists aim to identify the impacts of human exploitation and management regimes of mangroves on biodiversity richness and abundance, including demersal fish. The species composition of the ichthyofauna of Mida and trophic interactions therein was studied for five representative sampling areas. These sites are located at various distances from local villages in order to include the effect of different degrees of human disturbance. Samples were collected during 5-6 consecutive days close to spring tide in mid July 2011. Fishes were caught using several types of passive fishing gears such as large and small fyke nets, gill nets and occasionally beach seine. Each individual was identified to species level, measured and weighed. We performed stomach content analysis to provide information about fish diet. Furthermore, stable isotope analysis was applied on most fishes in order to detect whether the source of primary production for the higher trophic levels is mangrove-related or not. A total of 29 fish species was found with a catch of 939 teleost specimens. Our analyses showed that a majority of fish belonged to the zoobenthivorous/omnivorous trophic mode, they were mainly feeding on invertebrates. Their diet was quite similar over different locations and life stages. Two species (Sphyraena barracuda and Synodus variegatus) exhibited a mixed diet with a piscivorous preference. Results concerning the population structure suggested that the fish community of Mida consisted of both transient and resident species. Juveniles were, however, numerically more abundant in the whole area than adult specimens. Based on our restricted sampling period and methodology, we were not able to accurately detect human impacts on fish stock and species composition between locations. Finally, our results confirm that Mida Creek mangrove is an important habitat for the ichthyofauna especially for juvenile fishes. Its role as feeding and nursery ground appears well established

New Desmodoridae (Nematoda: Desmodoroidea): Three new species from <i>Ceriops</i> mangrove sediments (Kenya) and one related new species from the North Sea

Three new species of nematodes (Chromaspirina okemwai sp.n., Pseudochromadora interdigitatum sp. n. and Eubostrichus africanus sp. n.) from Ceriops mangrove sediments and one new species (Eubostrichus longosetosus sp. n.) from the North Sea, along the Belgian coast, are described. Chromaspirina okemwai is characterized by four cephalic sensillae and unispiral amphids; Pseudochromadora interdigitatum has unique lateral alae where body annules split into two, three or four smaller ones. Eubostrichus africanus has short (6 m) cephalic and subcervical setae and five pairs of strong broad based setae at the tail region; Eubostrichus longosetosus has long (14 m) cephalic and subeervical setae, three pairs of strong setae on the tail and two fine ones at the tail tip. Eubostrichus parasitiferus as described by Hopper and Cefalu (1973) is given a new name, E. hopperi sp. n. A revision of the genus Chromaspirina and Pseudochromadora is also included

Invasive Salmonellosis in Kilifi, Kenya.

BACKGROUND: Invasive salmonelloses are a major cause of morbidity and mortality in Africa, but the incidence and case fatality of each disease vary markedly by region. We aimed to describe the incidence, clinical characteristics, and antimicrobial susceptibility patterns of invasive salmonelloses among children and adults in Kilifi, Kenya. METHODS: We analyzed integrated clinical and laboratory records for patients presenting to the Kilifi County Hospital between 1998 and 2014. We calculated incidence, and summarized clinical features and multidrug resistance. RESULTS: Nontyphoidal Salmonella (NTS) accounted for 10.8% and 5.8% of bacteremia cases in children and adults, respectively, while Salmonella Typhi accounted for 0.5% and 2.1%, respectively. Among 351 NTS isolates serotyped, 160 (45.6%) were Salmonella Enteritidis and 152 (43.3%) were Salmonella Typhimurium. The incidence of NTS in children aged <5 years was 36.6 per 100 000 person-years, being highest in infants aged <7 days (174/100 000 person-years). The overall incidence of NTS in children varied markedly by location and declined significantly during the study period; the pattern of dominance of the NTS serotypes also shifted from Salmonella Enteritidis to Salmonella Typhimurium. Risk factors for invasive NTS disease were human immunodeficiency virus infection, malaria, and malnutrition; the case fatality ratio was 22.1% (71/321) in children aged <5 years and 36.7% (11/30) in adults. Multidrug resistance was present in 23.9% (84/351) of NTS isolates and 46.2% (12/26) of Salmonella Typhi isolates. CONCLUSIONS: In Kilifi, the incidence of invasive NTS was high, especially among newborn infants, but typhoid fever was uncommon. NTS remains an important cause of bacteremia in children <5 years of age

Practical actions to strengthen capacity for deep-water research in Africa

While Africa's deep marine biodiversity offers economic prospects it also supports crucial ecosystem services and sustainable development is dependent on knowledge of these systems. Building understanding of deep-water ecosystems is key, but there are substantial discrepancies in countries' abilities to achieve this. Coinciding with the 2024 Ocean Decade Conference, the Challenger 150 African Network of Deep-water Researchers is pleased to release a report on “Practical Actions to Strengthen Capacity for Deep-water Research in Africa”. Through a series of online workshops, the ANDR brought together 98 individuals from 19 African nations to discuss challenges for deep-water research in Africa, identify solutions to overcome these and propose practical actions going forward

Risk of nontyphoidal Salmonella bacteraemia in African children is modified by STAT4

Nontyphoidal Salmonella (NTS) is a major cause of bacteraemia in Africa. The disease typically affects HIV-infected individuals and young children, causing substantial morbidity and mortality. Here we present a genome-wide association study (180 cases, 2677 controls) and replication analysis of NTS bacteraemia in Kenyan and Malawian children. We identify a locus in STAT4, rs13390936, associated with NTS bacteraemia. rs13390936 is a context-specific expression quantitative trait locus for STAT4 RNA expression, and individuals carrying the NTS-risk genotype demonstrate decreased interferon-gamma (IFN gamma) production in stimulated natural killer cells, and decreased circulating IFN gamma concentrations during acute NTS bacteraemia. The NTS-risk allele at rs13390936 is associated with protection against a range of autoimmune diseases. These data implicate interleukin-12-dependent IFN gamma-mediated immunity as a determinant of invasive NTS disease in African children, and highlight the shared genetic architecture of infectious and autoimmune disease.Peer reviewe

A global horizon scan of issues impacting marine and coastal biodiversity conservation

The biodiversity of marine and coastal habitats is experiencing unprecedented change. While there are well-known drivers of these changes, such as overexploitation, climate change and pollution, there are also relatively unknown emerging issues that are poorly understood or recognized that have potentially positive or negative impacts on marine and coastal ecosystems. In this inaugural Marine and Coastal Horizon Scan, we brought together 30 scientists, policymakers and practitioners with transdisciplinary expertise in marine and coastal systems to identify new issues that are likely to have a significant impact on the functioning and conservation of marine and coastal biodiversity over the next 5–10 years. Based on a modified Delphi voting process, the final 15 issues presented were distilled from a list of 75 submitted by participants at the start of the process. These issues are grouped into three categories: ecosystem impacts, for example the impact of wildfires and the effect of poleward migration on equatorial biodiversity; resource exploitation, including an increase in the trade of fish swim bladders and increased exploitation of marine collagens; and new technologies, such as soft robotics and new biodegradable products. Our early identification of these issues and their potential impacts on marine and coastal biodiversity will support scientists, conservationists, resource managers and policymakers to address the challenges facing marine ecosystems

A blueprint for an inclusive, global deep-sea Ocean Decade field programme

The ocean plays a crucial role in the functioning of the Earth System and in the provision of vital goods and services. The United Nations (UN) declared 2021–2030 as the UN Decade of Ocean Science for Sustainable Development. The Roadmap for the Ocean Decade aims to achieve six critical societal outcomes (SOs) by 2030, through the pursuit of four objectives (Os). It specifically recognizes the scarcity of biological data for deep-sea biomes, and challenges the global scientific community to conduct research to advance understanding of deep-sea ecosystems to inform sustainable management. In this paper, we map four key scientific questions identified by the academic community to the Ocean Decade SOs: (i) What is the diversity of life in the deep ocean? (ii) How are populations and habitats connected? (iii) What is the role of living organisms in ecosystem function and service provision? and (iv) How do species, communities, and ecosystems respond to disturbance? We then consider the design of a global-scale program to address these questions by reviewing key drivers of ecological pattern and process. We recommend using the following criteria to stratify a global survey design: biogeographic region, depth, horizontal distance, substrate type, high and low climate hazard, fished/unfished, near/far from sources of pollution, licensed/protected from industry activities. We consider both spatial and temporal surveys, and emphasize new biological data collection that prioritizes southern and polar latitudes, deeper (&gt; 2000 m) depths, and midwater environments. We provide guidance on observational, experimental, and monitoring needs for different benthic and pelagic ecosystems. We then review recent efforts to standardize biological data and specimen collection and archiving, making “sampling design to knowledge application” recommendations in the context of a new global program. We also review and comment on needs, and recommend actions, to develop capacity in deep-sea research; and the role of inclusivity - from accessing indigenous and local knowledge to the sharing of technologies - as part of such a global program. We discuss the concept of a new global deep-sea biological research program ‘Challenger 150,’ highlighting what it could deliver for the Ocean Decade and UN Sustainable Development Goal 14

Nematodes from the Indian Ocean: description of six new species of the genus Molgolaimus Ditlevsen, 1921 (Nematoda: Desmodoridae)

Six new species of the genus Molgolaimus Ditlevsen, 1921 are described from the Indian Ocean. Molgolaimus abyssorum n. sp. is characterised by a small body (L = 287-370 µm), amphids close to the anterior end (2-3 µm behind the anterior end), short (2 x abd) curved spicules and absense of pre-cloacal supplements.Molgolaimus tyroi n. sp. is characterised by a small body size (L = 225-290 µm), amphids close the anterior end (2 µm behind anterior), long thin spicules curved twice and one or two pre-cloacal supplements. Molgolaimus gazii n. sp. is characterised by narrow anterior end with the head region slightly offset, wide amphids (70% cbd) located at 2.6-3.0 x hd behind the anterior end, thin, long spicules with anterior one third parallel to the body axis and posterior two thirds of its lenght curved. Molgolaimus sabakii n. sp. is characterised by narrow anterior end, sexual dimorphism in size of amphids [wide amphids in males (70-80% cbd), smaller ones in females (55% cbd)] located at 17-20 µm (3.4-4.0 x hd) behind the anterior end, thin long spicules which have anterior half parallel to the body axis and the posterior half curved and two ventral pre-cloacal supplements located within the spicule region. Molgolaimus kiwayui n. sp. is characterised by head region off set by a constriction, amphids located close to anterior end (1.0-1.5 x hd behind the anterior end), short slightly curved spicules with capitulum.Molgolaimus tanai n. sp. is characterised by cephalic setae (2-3 µm long) located at 5-6 µm behind the anterior end, amphids located at 7-9 µm behind the anterior end, long slender spicules (3.8-5.1 abd long) and a complex gubernaculum with lateral pieces. A key to the species of Molgolaimus is provided