Scottomyzon Gibberum (Copepoda) Associated With White Sea Starfish Asterias Rubens in Spatial and Temporal Aspects

Artem Poromov1, Andrey Smurov2

 

 

 

1 Moscow State University Of Mechanical Engineering, Translational Science Laboratory, Moscow, Russia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

2 Lomonosov Moscow State University, Biology faculty, Department of General Ecology, Moscow, Russia

 

 

Abstract

This paper describes indices of population the copepods Scottomyzon gibberum (Scott & Scott, 1894) on common starfish Asterias rubens Linnaeus, 1758. The material was collected during the vegetation period of 2012 and 2013 at the White Sea. The population indices increases from June to September, increases with depth and average starfishes size. The population indices heterogeneity which is shown can be attributed to the anthropogenic load and the ecosystem type and can be used as bioindicators of marine environment.

Keywords: symbiosis, Scottomyzon gibberum, intensity, extensity, Asterias rubens, White Sea

 

 

Introduction

The aim of this paper is to study the spatial and temporal dynamics of the colonisation of common starfish Asterias rubens Linnaeus, 1758 (or common sea star) by the copepods Scottomyzon gibberum (Scott & Scott, 1894) in the coastal region of the White Sea.

Echinoderms contain parasitic and symbiotic copepods from 25 genera. Echinoderms provide their symbionts with two main micro-biotopes − the surface of the body and the various cavities. The term symbiosis was supplied by Anton de Bary (Robinson, 1970), who explained it as long-term relationship between two different species. Also mutualism, commensalism and parasitism can be added here.

S. gibberum currently is the only species in the monotypic genus Scottomyzon Giesbrecht, 1897 of the Asterocheridae. The copepod is associated with the starfish A. rubens, they were discovered in 1767 (Humes, 1986) in the North Sea and the White Sea in 1991 (Smurov, 1993) in addition to many different species of starfishes in the Sea of Japan.

In slightly more than 100 years since its description, this "highly interesting copepod" has been redescribed by Roettger (1969). Roettger considered the unusual variability among mature females. Ivanenko (1999) and Ivanenko & Smurov (1995, 1996) discussed the growth of the adult female, morphology and settlement of the first copepodid stage, and bacterial infestation of the exoskeleton of White Sea specimens. Adult females of S. gibberum live on the A. rubens body surface and can induce the formation of galls. The galls are soft tissues host overgrowth, by small hole connects with the outside cavity. There is one or more spherical adult females with eggs in gall (Roettger, 1969). Adult females located on the all host's sides. The larval stage, males and young females are free-living. They can live directly on the host's body surface as typical ecto-symbionts or in the bottom layer of water (Marchenko, 2001).

S. gibberum in the Northern Seas have 1.5 - year life cycle. The females die in in October-November (Rottger, 1969). The egg sack contains mature eggs during the all vegetation period.

 

Fig01
Figure 1: Adult females of Scottomyzon gibberum, electron microscope, 100 μ.

Materials and Methods

Starfishes A. rubens were collected during the summers in 2012-2013 from 10 different points, one time in 3 weeks on average. The collection points at Kandalaksha Bay of the White Sea are represented in Figure 2 and Table 1. 1500 starfishes were examined.

Specimens of the starfish A. rubens were isolated in the plastic bags during SCUBA dives near the White Sea Biological station of Lomonosov Moscow State University. Individual starfishes were washed in freshwater and then this washwater was filtered through a fine-mesh net. Copepods S. gibberum were collected from starfishes with a preparation needle under binocular glasses. Copepod stages of S. gibberum were placed in a Petri dish, fixed with 4% formaldehyde in sea water and then examined.

The relative age of female copepod was determined by the carapace colour: 1-white, 2-light-colored, 3-dark. Copepods square was calculated through the length and width of carapace. The sizes parameters of each starfish were measured: Hr (distance from the madreporite to the inner circle, counter-radius), r (the distance from the body centre to the inner circle, small radius), R (distance from the centre to the outer circle, large radius).

Indices which are widely used in parasitological studies were calculated in order to characterize invasion: prevalence (the average number of symbionts on the host), intensity (relative number of hosts with symbionts), abundance, aggregations indices (variance/mean, index of discrepancy, and k of the negative binomial) and also the copepods location on the host's body (Rózsa, 2000).

 

Fig02
Figure 2: Data collection points; Points: 1 - Babye Sea, 2 - Polovye Islands, 3 - Ermolinskay Bay, 4 - WSBS (west), 5 - WSBS (pier), 6 - Eremeevskye Islands, 7 - Kislaya Bay, 8 - near v. Chernaya Rechka, 9 - v. Chernaya Rechka, 10 - Krestovye Islands.

 

Table 1: Characteristics of data collection points
Tab01