10.2.4 Meiofauna (Gastrotricha, Kinorhyncha, Tardigrada)
The term “meiofauna” (or “meiobenthos”) include microscopic benthic invertebrates
(size mainly between 0.5 and 1 mm) that live in both marine and freshwater
environments. Most of the recognized animal phyla have representatives in
meiofauna, but only five of them are exclusively meiofaunal. These tiny animals
are a common component of the interstitial environment (between sand grains)
where they reach a high abundance and are ubiquitous and ecologically important
in sedimentary bottoms recycling detritus and dead organic matter. Nematodes are
the dominant group of the marine interstitial environment, but this group has not
been documented in the Alboran Sea. Other common components of marine
meiofauna are Gastrotricha, Kinorhyncha or Tardigrada. These are very little studied
groups (also in the Alboran Sea), and their rarity is due to limited knowledge rather
than to real scarcity.
Gastrotricha is a clade of aquatic microscopic animals that are among the smallest
metazoans, mainly living in the marine and freshwater interstitial environment and
on the surface of aquatic plants. Only one species of this group, Pleurodasys
helgolandicus, widespread along the North Sea and the Atlantic European coasts,
is known to form stable populations along the Spanish coast of the Alboran Sea
(Todaro et al. 2006).
Kinorhyncha is a phylum of meiobenthic organisms less than 1 mm in length and
found exclusively in marine or estuarine sediments, from coarse sand or shell gravel
to very fine mud. Sánchez et al. (2012) recorded about 12 kinorhynch species in
south Spain (Algeciras Bay and Granada coast). Among them, Echinoderes
dujardinii (Fig. 10.7) was collected by Sánchez-Tocino et al. (2011) in shallow
waters near Almuñécar (Granada, Spain). Subsequently, two new species,
Dracoderes gallaicus and Pycnophyes almansae, were described from specimens
collected in Algeciras and Almuñécar (Sørensen et al. 2012; Sánchez et al. 2014).
Tardigrada are micrometazoans that occupy a diversity of niches in freshwater,
marine and terrestrial habitats. In the Alboran Sea, this group has only been studied
in the Chafarinas Islands by Villora Moreno and de Zio Grimaldi (1996) who
recorded 14 species, 5 of which were new records for the Mediterranean Sea.
Three of them were the first record after its original description: Florarctus acer,
F. asper and F. stellatus. Further, Halechiniscus chafarinensis was described as a
new species by de Zio Grimaldi and Villora-Moreno (1995).
10.2.5 Cycliophora
Cycliophora is one of the most recently described animal phyla whose members live
commensally on the mouthparts of lobsters of the family Nephropidae (Obst et al.
2005). Up to date, two species have been described, Symbion pandora, from the
Norway lobster (Nephrops norvegicus), and S. americanus, from the American
10 Invertebrates: The Realm of Diversity
371
The term “meiofauna” (or “meiobenthos”) include microscopic benthic invertebrates
(size mainly between 0.5 and 1 mm) that live in both marine and freshwater
environments. Most of the recognized animal phyla have representatives in
meiofauna, but only five of them are exclusively meiofaunal. These tiny animals
are a common component of the interstitial environment (between sand grains)
where they reach a high abundance and are ubiquitous and ecologically important
in sedimentary bottoms recycling detritus and dead organic matter. Nematodes are
the dominant group of the marine interstitial environment, but this group has not
been documented in the Alboran Sea. Other common components of marine
meiofauna are Gastrotricha, Kinorhyncha or Tardigrada. These are very little studied
groups (also in the Alboran Sea), and their rarity is due to limited knowledge rather
than to real scarcity.
Gastrotricha is a clade of aquatic microscopic animals that are among the smallest
metazoans, mainly living in the marine and freshwater interstitial environment and
on the surface of aquatic plants. Only one species of this group, Pleurodasys
helgolandicus, widespread along the North Sea and the Atlantic European coasts,
is known to form stable populations along the Spanish coast of the Alboran Sea
(Todaro et al. 2006).
Kinorhyncha is a phylum of meiobenthic organisms less than 1 mm in length and
found exclusively in marine or estuarine sediments, from coarse sand or shell gravel
to very fine mud. Sánchez et al. (2012) recorded about 12 kinorhynch species in
south Spain (Algeciras Bay and Granada coast). Among them, Echinoderes
dujardinii (Fig. 10.7) was collected by Sánchez-Tocino et al. (2011) in shallow
waters near Almuñécar (Granada, Spain). Subsequently, two new species,
Dracoderes gallaicus and Pycnophyes almansae, were described from specimens
collected in Algeciras and Almuñécar (Sørensen et al. 2012; Sánchez et al. 2014).
Tardigrada are micrometazoans that occupy a diversity of niches in freshwater,
marine and terrestrial habitats. In the Alboran Sea, this group has only been studied
in the Chafarinas Islands by Villora Moreno and de Zio Grimaldi (1996) who
recorded 14 species, 5 of which were new records for the Mediterranean Sea.
Three of them were the first record after its original description: Florarctus acer,
F. asper and F. stellatus. Further, Halechiniscus chafarinensis was described as a
new species by de Zio Grimaldi and Villora-Moreno (1995).
10.2.5 Cycliophora
Cycliophora is one of the most recently described animal phyla whose members live
commensally on the mouthparts of lobsters of the family Nephropidae (Obst et al.
2005). Up to date, two species have been described, Symbion pandora, from the
Norway lobster (Nephrops norvegicus), and S. americanus, from the American
10 Invertebrates: The Realm of Diversity
371