''Rehderella'' is an unusual and

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in eros ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

restricted to

Easter Island Easter Island ( rap, Rapa Nui; es, Isla de Pascua) is an island and special territory of Chile in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian Triangle in Oceania. The island is most famous for its nearl ...

and

Pitcairn Island Pitcairn Island is the only inhabited island of the Pitcairn Islands, of which many inhabitants are descendants of mutineers of HMS ''Bounty''. Geography The island is of volcanic origin, with a rugged cliff coastline. Unlike many other ...

. ''Rehderella belyaevi'' is its only species. Two other barnacle species are found in the intertidal zone of these islands. '' Euraphia devaneyi'' is much larger, and possesses calcareous basis. '' Tesseropora'' sp. has four shell plates with a single row of pores in shell wall. Both ''Euraphia'' and ''Rehderella'' have six shell wall plates. ''Rehderella'' differs from both in its membraneous basis and fusion of opercular plates on each side. '' Nesochthamalus intertextus'' is the only other

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

barnacle with fused opercular plates. ''Nesochthamalus'' possesses a partially calcareous saucer-shaped basis, and fused opercular plates which show no visible trace of former articulation. ''Rehderella'' shows a line at the former articulation.

Diagnosis and discussion

Shell wall of six plates with membraneous basis, and no basal infolding of shell wall. Sutures between wall plates are straight, and do not fuse at any time during its life cycle. The animal is small, about 5 mm length, and flattened, with a pinkish-yellow color. Opercular plates of ''Rehderella'' are distinctive in the scutum and tergum of each side fusing in young stages. A slight step in basal margin marks the former articulation between plates. Scutal adductor scar is deep and narrow, depressor pit indistinct. Tergal depressor crests 6-8, distinct, depending from basal margin. Soft part distinctions include card setae on cirri develop only after animal reaches a size of 5 mm. Caudal appendages are present, growing longer with age, up to 20 segments in large specimens.

Synonymy and nomenclature

''Rehderella''

* ''Rehderella'' , 1987: 327; (original description): , 2006: 85; (discussion). * Type species: ''Chthamalus belyaevi'' , 1973: 187 by original designation.

''Rehderella belyaevi''

* ''Chthamalus belyaevi'' , 1973: 187; (original description): , 1976
41
(summary of references). * ''Rehderella belyaevi'' (). , 1987: 327; (generic reassignment): , 1996: 993; (discussion: 2006: 85; (supplementary description, discussion). * Type locality:

. * Types and Repository: Zoological Museum, Moscow State University: Foster & Newman's topotypes; USNM 233268, 233269; British Museum (Natural History) Reg. No. 1987-3.

Habitat and geographical range

This species is found only on

and

in the uppermost

intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of Marine habitat, habitats with var ...

and

surf zone As ocean surface waves approach shore, they get taller and break, forming the foamy, bubbly surface called ''surf''. The region of breaking waves defines the surf zone, or breaker zone. After breaking in the surf zone, the waves (now reduced in ...

, where it forms dense colonies.

Whelk Whelk (also known as scungilli) is a common name applied to various kinds of sea snail. Although a number of whelks are relatively large and are in the family Buccinidae (the true whelks), the word ''whelk'' is also applied to some other marine ...

predation sets lower environmental limits. During times of calm seas, colonies can be exposed to air and sun for extended periods. In this upper zone, dominance is shared by the gastropod '' Nodolittorina pyramidalis pascua'', an algal grazer. Near the base of the barnacle zone, another grazer, '' Nerita morio'' becomes more common, along with other fauna.

References

External links

WoRMS
{{Taxonbar, from=Q16989036 Barnacles