Otocinclus

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Otocinclus

Zebra Oto - Otocinclus cocama
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Siluriformes
Family:	Loricariidae
Subfamily:	Hypoptopomatinae
Tribe:	Hypoptopomatini
Genus:	Otocinclus Cope, 1871
Type species
Otocinclus vestitus Cope, 1871
Species
Over a dozen, see text.
Synonyms
Lampiella Isbrücker, 2001 Macrotocinclus Isbrücker & Seidel, 2001

Otocinclus is a genus of catfish (order Siluriformes) of the family Loricariidae commonly called Dwarf Suckers or Otos. Otocinclus originate from tropical, freshwater rivers in South America.

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Taxonomy

Edward Drinker Cope described this genus in 1871. The type species is O. vestitus. Otocinclus is pronounced "ahto-SINK-luss". The name is derived from the Greek word oto, ear, and the Latin word cinclus, meaning a latticework; an allusion to the holes in the head in the region of the ear.^[1]

Otocinclus is the most basal genus of the tribe Hypoptopomatini of the subfamily Hypoptopomatinae. However, phylogenetic relationships are currently under study and this genus may eventually be relocated.^[2] Its monophyly is supported by seven derived features. There are currently about 16 species.^[2] O cocama, O. huaorani, O. bororo, O. mariae, and O. mura, and O. batmani form a monophyletic group within this genus.^[2] A monophyletic group is also formed by O. flexilis, O. affinis, O. xakriaba, and O. mimulus, which all share mimicry as a synapomorphy.^[3]

Distribution

Otocinclus are widely distributed east of the Andes of South America, throughout the lowlands from northern Venezuela to northern Argentina, but is generally absent from the Amazon and the Orinoco lowlands.^[3]

Description

Otocinclus, like other Loricariids, are characterized by rows of armour plating covering the body as well as underslung suckermouth. They are generally small in size; Otocinclus tapirape is the smallest of the species (2.4 cm), while Otocinclus flexilis is the biggest (5.5 cm). These fish do not exceed 50 millimetres (2.0 in) SL.^[4]

Otocinclus have adaptations that allow these fish to breathe air. A duct forms at the junction between the esophagus and the stomach and expands into an enlarged, ring-like diverticulum. This characteristic is diagnostic of this genus. This diverticulum allows air-breathing of these fishes.^[5]

Ecology

Otocinclus species are diurnal and generally found in small streams or along the margins of larger rivers, clinging to substrates using the mouth as a sucker, and feeding from algae or aufwuchs on roots, stones, macrophytes, and broad-leaved grasses.^[3] They inhabit well-oxygenated, moderate- to slow-flowing environments, often near river banks.^[4] They are found near the surface of the water, but are often associated with vegetation or other structures.^[2] They lay adhesive eggs and do not guard them; this is in contrast to many other Loricariids where the male builds a nest and guards the eggs.^[6] These fish live in shoals or schools.^[3]

Otocinclus are able to breathe air. Prior to surfacing, they will release air through their gills and mouth. Upon returning to the bottom, the fish does not need to pump their buccal cavity, indicating that they are absorbing oxygen from the swallowed air.^[5]

O. mimulus, O. flexilis, O. affinis, and O. xakriaba are considered to be Batesian mimics of certain Corydoras species (C. diphyes, C. paleatus, C. nattereri, and C. garbei, respectively). These Corydoras species have bony plates of armor and strong spines as defenses, making them less palatable; by mimicking these species in size and coloration, Otocinclus avoid predation.^[3]

In the aquarium

Otocinclus macrospilus

Otocinclus are a popular aquarium fish. They are often purchased as algae eaters, and are more suitable for the job in smaller aquaria than many of the larger Loricariid relatives such as plecostomus. Water quality should be kept clean for these fish. As otos like company, they should be kept in groups of 3 or more individuals, unlike most other plecos.^[6] They are generally delicate fish, and only thrive in heavily planted aquariums. If not enough algae is present in the aquarium, their diet can be supplemented with algae wafers, blanched Zucchini, and other plant foods.