Microbial proliferation on gill structures of juvenile European lobster (Homarus gammarus) during a moult cycle

Karen L. Middlemiss,Rod W. Wilson,Mauricio A. Urbina

doi:10.1007/s10152-015-0445-4

Karen L. Middlemiss, Rod W. Wilson + Show 1 more

Open Access

https://doi.org/10.1007/s10152-015-0445-4

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Abstract

The morphology of gill-cleaning structures is not well described in European lobster (Homarus gammarus). Furthermore, the magnitude and time scale of microbial proliferation on gill structures is unknown to date. Scanning electron microscopy was used to investigate development of setae in zoea, megalopa and juvenile stages (I–V). Microbes were classified and quantified on gill structures throughout a moult cycle from megalopa (stage IV) to juvenile (stage V). Epipodial serrulate setae, consisting of a naked proximal setal shaft with the distal portion possessing scale-like outgrowths (setules), occur only after zoea stage III. After moulting to megalopa (stage IV), gill structures were completely clean and no microbes were visible on days 1 or 5 postmoult. Microbial proliferation was first evident on day 10 postmoult, with a significant 16-fold increase from day 10 to 15. Rod-shaped bacteria were initially predominant (by day 10); however, by day 15 the microbial community was dominated by cocci-shaped bacteria. This research provides new insights into the morphology of gill-grooming structures, the timing of their development, and the magnitude, timescale and characteristics of gill microbial proliferation during a moult cycle. To some degree, the exponential growth of epibionts on gills found during a moult cycle will likely impair respiratory (gas exchange) and ion regulatory function, yet further research is needed to evaluate the physiological effects of the exponential bacterial proliferation documented here.

Highlights

Gill structures in Crustacea contribute to several vital physiological processes such as respiration, osmoregulation, ion and pH regulation, as well as nitrogenous waste excretion (Henry et al 2012)
The magnitude and time scale of microbial proliferation on gill structures is unknown to date
The objectives of the present study were to (1) identify when setae first appear during the developmental stages, (2) describe the morphology of gill-cleaning setae and (3) provide the first report on magnitude, time scale and characteristics of microbial colonisation during a complete moult cycle in early H. gammarus development

Summary

Introduction

Gill structures in Crustacea contribute to several vital physiological processes such as respiration, osmoregulation, ion and pH regulation, as well as nitrogenous waste excretion (Henry et al 2012). Decapod crustacean gills are complex structures which fall into three distinct morphological categories: phyllobranchiate, dendrobranchiate and trichobranchiate (Boxshall and Jaume 2009). In crabs (Decapoda) for instance, the gills are phyllobranchiate consisting of lamellar structures (Taylor and Greenaway 1979). Shrimp (e.g. penaeoid and sergestoid) possess dendrobranchiate gill structures (Boxshall and Jaume 2009). In Homarus gammarus, each gill chamber contains 20 trichobranchiate gills and 7 epipodites, both playing a role in respiration and osmoregulation (Haond et al 1998; Lignot et al 1999; Lignot and Charmantier 2001)

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