Transient Aggregations Research Articles

Putative spawning aggregations of giant trevally in the Red Sea

Timing and location of transient reef fish spawning aggregations are fundamental data required to effectively manage populations, particularly those exposed to commercial fisheries. The giant trevally (Caranx ignobilis) is a semipelagic apex predator of ecological, economic, and cultural significance across its Indo-Pacific range, yet information regarding regional spawning aggregations for the species remains scarce. Here we present documentation to record, for the first time, putative transient spawning aggregations of giant trevally in the Red Sea. Considering that other C. ignobilis aggregations demonstrate highly predictable and specific spatiotemporal dynamics, relevant resource managers should pursue protection strategies to avoid rapid overexploitation of the stock.

The need for long-term population monitoring of the world’s largest fish

Many large marine species are vulnerable to anthropogenic pressures, and substantial declines have been documented across a range of taxa. Many of these species are also long-lived, have low individual resighting rates and high levels of individual heterogeneity in capture probability, which complicates assessments of their conservation status with capture-�mark-�recapture (CMR) models. Few studies have been able to apply CMR models to whale sharks Rhincodon typus, the world’s largest fish. One of their aggregation sites off Mafia Island in Tanzania is characterised by unusually high residency of this Endangered species, making it an ideal target for CMR methods. Three different CMR models were fitted to an 8 yr photo-identification data set to estimate abundance, population trend and demographic parameters. As anticipated, resighting rates were unusually high compared to other aggregations. Different CMR models produced broadly similar parameter estimates, showing a stable population trend with high survivorship and limited recruitment. Tagging and biopsy sampling for concurrent research did not negatively affect those sharks’ apparent survival or capture probabilities. Scenario-based power analyses showed that only pronounced abundance trends (±30%) would be detectable over our study period, at a 90% level of probability, even with the relatively high precision in yearly abundance estimates achieved here. Other, more transient whale shark aggregations, with reduced precision in abundance estimates, may only be able to confidently detect a similar trend with CMR models after 15-20 yr of observations. Precautionary management and long-term monitoring will be required to assist and document the recovery of this iconic species.

Spawning aggregation sites of the cubera snapper, Lutjanus cyanopterus, on the continental shelf of Bahia state, Northeastern Brazil

The cubera snapper (caranha), Lutjanus cyanopterus, is an important resource for reef fisheries in Northeastern Brazil, currently classified as Vulnerable (VU) on the Red List of Threatened Species. This species forms large transient reproductive aggregations, concentrating their reproductive efforts in a short period of the year and in specific spawning sites, which have already been well documented in the Caribbean. These aggregations are predictable in time and space, making them considerably vulnerable to overfishing and other sources of anthropic impacts. These tend to reduce the population’s renewal capacity and genetic diversity, thus contributing to the decline of fish stocks and to the process of local extinctions. Between 2009 and 2010 we identified two L. cyanopterus aggregation sites, commonly known as “Caranheiros”, in two sub-areas located at the continental shelf-break zone of Bahia state, Northeastern Brazil, in the East Brazil Shelf Large Marine Ecosystem (LME16), between latitudes 12 °S and 15 °S. The present study aims to (1) describe patterns of spatial and temporal distribution, and the biological characteristics of L. cyanopterus’ catches from line fisheries targeting the specific aggregations in the two Caranheiros sites; and (2) validate the reproductive character of these aggregations through macroscopic evaluation of sexual maturity phases of the fishes caught. We analyzed fisheries and biological sampling data from the catches of artisanal fleets monitored in the two sub-areas between 2005 and 2014. The identified aggregations occur annually from December to May, with capture peaks concentrated in waning to waxing moon phases, in January, February and March. The predominance of mature, pre-spawning and spent (recent spawning) individuals, males and females, in these aggregations revealed the reproductive activity in both sites. Identifying and validating these spawning sites may contribute to the development of recovery and conservation plans for this threatened species. The continuous monitoring of fisheries on aggregations is a priority, aiming to trigger management responses and adaptative fisheries management. Considering these sites are highly vulnerable and have high local socioeconomical importance, especially to traditional fishers, the exact location of the analyzed “Caranheiros” is not revealed in this publication. However, it has been made available to the government agencies responsible for fisheries control and surveillance, as well as for implementing management and conservation measures for the sustainable use of fisheries resources.

Patagonian grouper Acanthistius patachonicus (Jenyns, 1840) forms massive spawning aggregations in the Southwest Atlantic.

Here we describe massive spawning aggregations and seasonal changes in the large-scale distribution of the Patagonian grouper Acanthistius patachonicus in the Southwest Atlantic based on three sources of information: (a) data from bottom trawl research surveys covering the distributional range of the species within the Argentine continental shelf; (b) folk ecological knowledge gathered from experienced captains of the Argentine industrial trawl fisheries; and (c) sampling of an artisanal trap fishery targeting the Patagonian grouper in a specific location off the coast of Buenos Aires Province. The trawl surveys showed a general pattern of aggregation of Patagonian grouper towards the coast during the reproductive period (September-December). Captains described massive aggregations of the species at specific near-shore locations, where trawl catches of up to 15 t in a single haul were registered during the reproductive season. At a local scale, the artisanal trap fishery described operates exclusively during the reproductive period, targeting near-shore aggregations with a high proportion of individuals releasing gametes onboard. These three sources of information provide evidence of the existence of massive transient spawning aggregations of Patagonian grouper in the Argentine shelf. This is the first report of a reef fish spawning aggregation in the southern region of the Southwest Atlantic. Anecdotal information gathered in this study points to the depletion of many of the aggregations targeted during the 1980s and 1990s by the industrial fleet. At the same time, the spawning aggregation site off Buenos Aires Province has been productive for the last 34 years, being exploited exclusively by traps. The Patagonian grouper is classified as Data Deficient by the International Union for Conservation of Nature, which highlights the need for further research to determine its stock status. Mapping its current spawning aggregations should be a priority to inform the design of a targeted monitoring program and management plan for this species.

Seasonal monitoring of deep-sea megabenthos in Barkley Canyon cold seep by internet operated vehicle (IOV).

Knowledge of the processes shaping deep-sea benthic communities at seasonal scales in cold-seep environments is incomplete. Cold seeps within highly dynamic regions, such as submarine canyons, where variable current regimes may occur, are particularly understudied. Novel Internet Operated Vehicles (IOVs), such as tracked crawlers, provide new techniques for investigating these ecosystems over prolonged periods. In this study a benthic crawler connected to the NEPTUNE cabled infrastructure operated by Ocean Networks Canada was used to monitor community changes across 60 m2 of a cold-seep area of the Barkley Canyon, North East Pacific, at ~890 m depth within an Oxygen Minimum Zone (OMZ). Short video-transects were run at 4-h intervals during the first week of successive calendar months, over a 14 month period (February 14th 2013 to April 14th 2014). Within each recorded transect video megafauna abundances were computed and changes in environmental conditions concurrently measured. The responses of fauna to environmental conditions as a proxy of seasonality were assessed through analysis of abundances in a total of 438 video-transects (over 92 h of total footage). 7698 fauna individuals from 6 phyla (Cnidaria, Ctenophora, Arthropoda, Echinodermata, Mollusca, and Chordata) were logged and patterns in abundances of the 7 most abundant taxa (i.e. rockfish Sebastidae, sablefish Anoplopoma fimbria, hagfish Eptatretus stoutii, buccinids (Buccinoidea), undefined small crabs, ctenophores Bolinopsis infundibulum, and Scyphomedusa Poralia rufescens) were identified. Patterns in the reproductive behaviour of the grooved tanner crab (Chionnecetes tanneri) were also indicated. Temporal variations in biodiversity and abundance in megabenthic fauna was significantly influenced by variabilities in flow velocity flow direction (up or down canyon), dissolved oxygen concentration and month of study. Also reported here for the first time are transient mass aggregations of grooved tanner crabs through these depths of the canyon system, in early spring and likely linked to the crab’s reproductive cycle.

Diverse activities of viral cis-acting RNA regulatory elements revealed using multicolor, long-term, single-cell imaging.

Cis-acting RNA structural elements govern crucial aspects of viral gene expression. How these structures and other posttranscriptional signals affect RNA trafficking and translation in the context of single cells is poorly understood. Herein we describe a multicolor, long-term (>24 h) imaging strategy for measuring integrated aspects of viral RNA regulatory control in individual cells. We apply this strategy to demonstrate differential mRNA trafficking behaviors governed by RNA elements derived from three retroviruses (HIV-1, murine leukemia virus, and Mason-Pfizer monkey virus), two hepadnaviruses (hepatitis B virus and woodchuck hepatitis virus), and an intron-retaining transcript encoded by the cellular NXF1 gene. Striking behaviors include "burst" RNA nuclear export dynamics regulated by HIV-1's Rev response element and the viral Rev protein; transient aggregations of RNAs into discrete foci at or near the nuclear membrane triggered by multiple elements; and a novel, pulsiform RNA export activity regulated by the hepadnaviral posttranscriptional regulatory element. We incorporate single-cell tracking and a data-mining algorithm into our approach to obtain RNA element-specific, high-resolution gene expression signatures. Together these imaging assays constitute a tractable, systems-based platform for studying otherwise difficult to access spatiotemporal features of viral and cellular gene regulation.

Indirect signals of spawning aggregations of three commercial reef fish species on the continental shelf of Bahia, east coast of Brazil

AbstractLutjanus analis (Mutton snapper), Lutjanus jocu(Dog snapper) and Mycteroperca bonaci (Black grouper) are reef fishes of high commercial value, and are among the principal exploited reef resources on the eastern and northeastern coast of Brazil. These species share the habit of forming transient spawning aggregations, predictable in time and space, which leaves them particularly vulnerable. The present study aimed to obtain indirect indicators of periods and places of spawning aggregations for these species, based on the exploratory analysis of available data on commercial catches and fishing efforts in Southern Bahia. Line fishery landings data were monitored in 12 locations in the region, and catch records of Mutton snapper (1320 landings), Dog snapper (654) and Black grouper (1162) were analyzed. A strategy was developed for exploratory analysis of monthly CPUE variation and individual distribution of CPUE per trip. The results showed the occurrence of aggregations in 26 specific sites, with values of relative abundance far above the annual mean, during spring/summer and autumn/winter. The occurrence of these anomalous catches was validated with the fishermen responsible for respective fishing trips. Additional studies are needed to confirm spawning activity at these sites. Analysis of inter-annual variation suggests a decreasing trend in relative abundance of Black grouper and Mutton snapper, possibly associated with unregulated fishing of spawning aggregations.

Fish populations forming transient spawning aggregations: should spawners always be the targets of spatial protection efforts?

Abstract Many coral reef fish form transient spawning aggregations at sites located a few to hundreds of kilometres from their normal residence areas. Reef fish spawning aggregations (“FSAs”) are often heavily exploited, which make them targets for management with marine reserves. We used a per-recruit model to compare the long-term conservation (impacts on female spawning-stock biomass-per-recruit (SSBR) and female : male sex ratio, SR) and fisheries effects (impacts on yield-per-recruit, YPR) of spawning reserves vs. normal residence reserves for two data-poor populations from Seychelles with contrasting life history traits and sexual modes: the Siganus sutor population of the main granitic islands, which has a fast life history and is gonochoristic and the Epinephelus fuscoguttatus population of Farquhar Atoll, which has a slow life history and is protogynous. Overall, our results suggest that normal residence reserves are more effective at improving both the SSBR and YPR of S. sutor. In contrast, the protection of a substantial fraction of spawning sites is preferable for E. fuscoguttatus to ensure the reproductive output of this protogynous population through normalization of SR and maintenance of high SSBR. Neither spawning reserves nor normal residence reserves improved the YPR of E. fuscoguttatus. However, yields of E. fuscoguttatus may increase on the long term via recruitment subsidy if a substantial fraction of spawning sites is protected. This may occur only if the population was recruitment limited in the absence of reserves and increases in SSBR compensate for lost opportunities caused by the area closures. Sensitivity analyses revealed that the relative effects of spawning reserves and normal residence reserves relate more to the change in catchability occurring with FSA formation than to life history traits. Thus, normal residence reserves should be preferred over spawning reserves for S. sutor essentially because its catchability at spawning sites is low relative to many other aggregation-forming populations. S. sutor therefore suffers higher fishing mortality in normal residence areas than at FSA sites. Our study demonstrates that spawning reserves are not always the most effective tool for balancing conservation and exploitation objectives for FSA-forming populations, and that this measure should ideally be weighed against other management options.

The influence of natural cycles on coral reef fish movement: implications for underwater visual census (UVC) surveys

Movement patterns of some coral reef fishes change with natural cycles (e.g., tidal, lunar and seasonal), resulting in short-term shifts in fish assemblages. We reviewed the literature on temporal changes in coral reef fish assemblages derived from underwater visual census (UVC) and found that movement was rarely considered in experimental design and analysis or as cause of change in interpretation of the results. Studies of vagile species, large individuals, species forming transient spawning aggregations and studies of fishes in contiguous habitats are most likely to be affected by such movements. Ignoring predictable patterns of movement associated with such natural cycles in survey design and analysis increases “unexplained” variation, making it more difficult to detect longer-term changes in fish assemblages and reducing the effectiveness of UVC as a monitoring tool.

Evaluation of the effectiveness of marine reserves for transient spawning aggregations in data-limited situations

Abstract Many coral reef fish species form predictable, transient spawning aggregations. Many aggregations are overfished, making them a target for spatial management. Here, we develop a per-recruit model to evaluate the performance of no-take marine reserves protecting transient spawning aggregations. The model consists of only 14 demographic and exploitation-related parameters. We applied the model to a protogynous grouper and a gonochoristic rabbitfish from Seychelles and tested six scenarios regarding the extent of protected areas, the level of fish spawning-site fidelity, and fishing effort redistribution post reserve implementation. Spawning aggregation reserves improve spawning-stock biomass-per-recruit and reduce the sex ratio bias in protogynous populations for all scenarios examined. However, these benefits are often small and vary among the different scenarios and as a function of sexual ontogeny. In all scenarios, increases in yield-per-recruit do not occur or are negligible. The long-term yield increases due to spawning aggregation reserves may still occur, but only if spawning-stock biomass recovery results in a recruitment subsidy. Given these limited benefits, the value of no-take reserves must be weighed against those of other management options, such as fishing effort reduction and seasonal fishery closures. The latter is particularly appropriate when spawning and non-spawning areas overlap in space.

Metrics to characterize vertical distributions of pelagic fauna in large acoustic datasets.

Active acoustics are a valuable addition to ocean observatories, allowing the detection of animals throughout the water column with high temporal and spatial resolution. The resulting datasets are large and can be difficult to describe and visualize in their entirety. We assembled a suite of metrics to parsimoniously characterize the vertical distribution of animal densities, including measures of abundance, density, location, dispersion, occupancy, evenness, and aggregation. We also developed and tested an unsupervised algorithm for detecting and counting backscatter layers within an echogram, using a gradient‐based classification. These metrics were used to analyze data from the Deep Echo Integrating Marine Observatory System (DEIMOS), a 38 kHz upward‐looking acoustic package deployed at the MARS observatory node in Monterey Bay, CA. The metrics successfully captured biological dynamics across multiple time scales, including seasonal, diel, and tidal variability, in addition to episodic events such as transient aggregations. All metric series showed significant positive autocorrelations at lags less than 26 days and as long as 103 days. Their frequency spectra were power‐law distributed with exponents between −0.84 and −1.73. This approach could be expanded to two or three dimensions, providing an effective means to quantify the temporal variability of any spatial density distribution.

Connectivity of a large embayment and coastal fishery: spawning aggregations in one bay source local and broad-scale fishery replenishment

Ichthyoplankton sampling and otolith chemistry were used to determine the importance of transient spawning aggregations of snapper Chrysophrys auratus (Sparidae) in a large embayment, Port Phillip Bay (PPB), Australia, as a source of local and broad-scale fishery replenishment. Ichthyoplankton sampling across five spawning seasons within PPB, across the narrow entrance to the bay and in adjacent coastal waters, indicated that although spawning may occur in coastal waters, the spawning aggregations within the bay were the primary source of larval recruitment to the bay. Otolith chemical signatures previously characterized for 0+ year C. auratus of two cohorts (2000 and 2001) were used as the baseline signatures to quantify the contribution that fish derived from reproduction in PPB make to fishery replenishment. Sampling of these cohorts over a 5 year period at various widely dispersed fishery regions, combined with maximum likelihood analyses of the chemistry of the 0+ year otolith portions of these older fish, indicated that C. auratus of 1 to 3+ years of age displayed both local residency and broad-scale emigration from PPB to populate coastal waters and an adjacent bay (Western Port). While the PPB fishery was consistently dominated (>70%) by locally derived fish irrespective of cohort or age, the contribution of fish that had originated from PPB to distant populations increased with age. At 4 to 5+ years of age, when C. auratus mature and fully recruit to the fishery, populations of both cohorts across the entire central and western Victorian fishery, including two major embayments and c. 800 km of coastal waters, were dominated (>70%) by fish that had originated from the spawning aggregations and nursery habitat within PPB. Dependence of this broadly dispersed fishery on replenishment from heavily targeted spawning aggregations within one embayment has significant implications for management and monitoring programmes.

Prediction and verification of possible reef‐fish spawning aggregation sites in Los Roques Archipelago National Park, Venezuela

This study attempts to predict and verify possible spawning aggregation sites and times in the Los Roques Archipelago National Park, Venezuela, based on physical reef characteristics and the knowledge of experienced local fishermen. Three possible aggregation sites were selected for monitoring based on satellite images, low-cost bathymetric mapping and interviews with experienced local fishermen. Abundances and sizes of 18 species that are known to form reproductive aggregations were monitored at these sites using underwater visual census for 7 days after each full moon from February to August, 2007. While spawning events were not observed, possible indirect evidence of spawning aggregations was found for Lutjanus analis at Cayo Sal and Boca de Sebastopol, Lutjanus apodus at Cayo Sal, Lutjanus cyanopterus at Cayo Sal and Piedra La Guasa and Epinephelus guttatus at Bajo California and Cayo de Agua. Additionally, indirect evidence was identified for the past existence of a spawning aggregation of Epinephelus striatus in the northern part of the archipelago, which may have been eliminated by overfishing c.15 years ago. Bathymetric mapping showed that the shelf edge at sites monitored in this study was shallower than at spawning aggregation sites in other parts of the Caribbean, and that sites were not proximal to deep water. While this study does not prove the existence or locations of spawning aggregations of reef fishes in the archipelago, it does add insight to a growing understanding of generalities in the relationship between seafloor characteristics and the locations of transient reef-fish spawning aggregations in the Caribbean.

Correlation of dendritic cell maturation and the formation of aggregates of poly-ubiquitinated proteins in the cytosol.

Dendritic cells (DCs) are the most powerful antigen presenting cells (APCs) in the immune system. Therefore, they are able to take up antigen by phagocytosis, macropinocytosis or endocytosis, process it in the cytosol and present it to naive T cells. It is known that presentation of the immunodominant influenza virus nucleoprotein-derived CTL epitope is delayed in bone marrow-derived DCs (BMDCs) compared to non-professional APCs. This delay coincided with the formation of transient aggregations of ubiquitinated proteins (DALIS, dendritic cell aggresome-like induced structures), which contain probably defective ribosomal products (DRiPs). DRiPs appear in the cytosol of maturing DCs and macrophages. Normally, DRiPs are degraded rapidly by proteasomes. However, their storage in DALIS delays their degradation. So, it is hypothesized that DALIS can function as antigen depots allowing DCs to coordinate maturation and antigen presentation during their migration to the lymph nodes. Upon inhibition of several pathways among the in signal transduction pathways of DCs, like the phosphatidylinositol 3-kinase (PI3-K) or the mammalian target of Rapamycin (mTOR), the cells show a rendered maturation profile. The formation of DALIS is inhibited in these cells which can be expected to influence antigen processing and presentation.

Hydrogen adsorption on Ru(0 0 1) studied by scanning tunneling microscopy

The adsorption of hydrogen on Ru(0 0 1) was studied by scanning tunneling microscopy at temperatures around 50 K. Hydrogen was found to adsorb dissociatively forming different ordered structures as a function of coverage. In order of increasing coverage θ in monolayers (ML) these were (√3 × √3) R30° at θ = 0.3 ML; (2 × 1) at θ = 0.50 ML, (2 × 2)-3H at θ = 0.75, and (1 × 1) at θ = 1.00. Some of these structures were observed to coexist at intermediate coverage values. Close to saturation of 1 ML, H-vacancies (unoccupied three fold fcc-hollow Ru sites) were observed either as single entities or forming transient aggregations. These vacancies diffuse and aggregate to form active sites for the dissociative adsorption of hydrogen.

Reproductive behaviour of a temperate serranid fish,Paralabrax clathratus(Girard), from Santa Catalina Island, California, U.S.A.

The reproductive behaviour of the kelp bassParalabrax clathratuswas studied on Santa Catalina Island, California, U.S.A. from April 2000 to September 2002. Adults formed aggregations of three to > 200 individuals, and spawning occurred within subgroups of three to 23 individuals that contained a single female. The gonado‐somatic index (IG) of collected ripe males (mean = 5·8%, range = 0·5–13·1%) indicated a large investment in sperm production that is common in group‐spawning fishes characterized by intense sperm competition. Spawning occurred 32 min before sunset to 120 min after sunset, and both males and females were capable of spawning multiple times during a single evening. Behavioural observations of adults and estimates of spawning periodicity from the collection of females with hydrated oocytes suggested that spawning occurred continuously throughout the summer months and showed no significant relationship with the lunar cycle. In general, the spawning behaviour of kelp bass was similar to other functionally gonochoric, group‐spawning serranids. The dynamics ofP. clathratusspawning aggregations, however, were inconsistent with that of tropical reef fish spawning aggregations, including the transient spawning aggregations of some tropical serranids. Aggregation spawning appeared to be an important component of the annual reproduction of this species.

Regional Differences in the Ontogeny of the Serotonergic Projection to the Cerebral Cortex

We used light and electron microscope immunocytochemistry to compare the development of the pattern of innervation and synaptic organization of the serotonin (5-HT) afferent system in sensory (visual and somatosensory) and motor areas of the rat cerebral cortex. Serotonin-labeled fibers were present in all cortical areas at birth appearing as two tangential streams, one above and one below the cortical plate. These fibers gradually arborized sending branches into all cortical layers in an “inside-out” sequence that broadly paralleled the gradient of neurogenesis and differentiation in the cortex. A striking feature at the early stages of postnatal development of the visual and somatosensory cortex was the transient presence of a dense accumulation of 5-HT fibers in layer IV. In agreement with earlier reports, transient aggregations of serotonergic axons characterized sensory but not motor areas of the cortex. The innervation pattern characteristic of the adult cortex was attained by the end of the 3rd postnatal week. Electron microscopic analysis of the developing visual cortex showed that 5-HT-containing axonal varicosities formed synaptic contacts, predominantly of the asymmetrical variety, throughout postnatal life. The proportion of varicosities forming synapses increased gradually from birth to reach a peak at the end of the 2nd week, then declined markedly in the subsequent week before rising again at later stages. It appears that the formation of exuberant synapses by 5-HT axons coincides with the period of maturation of the neuronal circuitry of this cortical area. When quantitative analysis was restricted only to layer IV, the proportion of varicosities forming synapses reached a peak at the end of the 1st week of life, when transient innervation was most prominent in this layer. These results suggest that the effects of this dense band of serotonergic axons may be mediated through axodendritic synapses. The types of postsynaptic elements involved in the formation of synapses varied according to age, suggesting progressive morphological differentiation of cortical target neurons or, alternatively, a continuous process of removal and establishment of new connections by 5-HT axons in the visual cortex. In contrast, analysis in the motor cortex revealed a continuous increase in the proportion of 5-HT varicosities engaged in synaptic contacts from birth to the late stages of development. The results presented here provide anatomical evidence for a differential role of 5-HT in the maturation of the cerebral cortex.

The role of cell-wall associated lipids in the pathogenesis of lesions in experimental murine nocardiosis vs lesions produced by Mycobacterium fortuitum

The pulmonary pathogens, Nocardia asteroides and Mycobacterium fortuitum classically produce a markedly different tissue response ranging from the acute suppurative lesion of nocardiosis to the granulomatous disease produced by the Mycobacterium. Both organisms have similar cell-wall associated lipids which have been chemically characterized as types of saturated and unsaturated fatty acids. Earlier studies of virulence factors from M. tuberculosis and other Mycobacteria have shown that much of the host response is due to lipid constituency of the organism cell wall. In order to determine that contribution which the cell-wall associated lipids make in the pathogenesis of nocardiosis produced by N. asteroides and mycobacteriosis due to M. fortuitum, separate lipid fractions were obtained using the Anderson extraction technique as modified by Asselineau (Asselineau, J. 1966. The Bacterial Lipids. Hermann, Paris). These lipid fractions were injected into mice and the lesion development observed. Waxes A and D from the two organisms exhibited distinct differences in tissue response. Wax A from Nocardia produced a pronounced tissue response composed of multiple abscesses, macrophages, and reactive fibrous tissue. Wax A from Mycobacterium showed transient aggregations of polymorphonuclear leukocytes. Mycobacteria-derived wax D elicited a marked granulomatous response which persisted throughout the duration of the study, contrasting with a minimally acute inflammatory response to Nocardia-derived wax D. The phosphatide and soluble-fat fractions also showed aggressive lesions; however, these were similar for both organisms. These results indicate that the differences in tissue response elicited by lipids from N. asteroides and M. fortuitum may reside in wax fractions A and D.