The dartfishes of the family Ptereleotridae have been taxonomically mobile in recent years and some taxonomists now include them in the wormfish family Microdesmidae. I place them here alongside the family Eleotridae because they are also gobioids and share the clearly-divided pelvic fins of the eleotrids. Larval ptereleotrids most closely resemble the "long" larvae of my Group 4 gobies. There are only two dartfishes in the region, a pair of sibling species that vary only slightly in color: their larvae are likely identical.
The sleepers of the family Eleotridae (some use Eleotrididae) are similar to gobies but have divided and well-separated pelvic fins (photograph of the separated pelvic fins in
Eleotrids are typically found in tropical freshwater habitats, but they do penetrate brackish and mangrove environments. Some species get large as adults and can even become gamefishes in the major river systems of central America. Their larvae, however, are small to medium-sized and exhibit similar body shapes and marking patterns to the larvae of their goby relatives.
Larval eleotrids share many basic characters of larval gobies. While most of the true gobies have fused pelvic fins, several genera have divided pelvic fins like the eleotrids (although they do not have the fins completely separated at the base as do the sleepers). pelvic-fin morphology is not always easily apparent on small larvae, but fortunately there are only a few species of eleotrids in the Caribbean and larval eleotrids do have a somewhat different appearance from the usual goby gestalt.
Most eleotrid larvae share a distinctive suite of characters. They have long ventral midline streaks of melanophores that extend onto the abdomen. Most also have linear internal melanophores extending up from the anal-fin base along myomere edges. Pre-transitional stages usually have odd-shaped narrowed eyeballs, some with unusual pigmented membranes over the iris that can expand to essentially cover the shiny surface completely. Also unusual is the high number of procurrent caudal-fin rays, up to 14, in several eleotrid species; true gobies almost always have 10 or fewer, often many fewer. The goby exceptions are the larvae of the river gobies of Sicydium and Awaous. Interestingly, the common factor is freshwater habitat; the high number of procurrent caudal-fin rays is likely an adaptation for living in fast-flowing streams. Eleotrid larvae also exhibit some of the more dramatic eye-shape changes during development and at transition found in larval fishes.
Eleotrid larvae tend to share basic melanophore patterns and general morphology, and fin-ray count differences are slight. There is also a marked degree of variation within species, making species identifications more difficult. Some characters common in one larval type will occur occasionally (or later in transition) in another larval type; for example, the characteristic melanophore patterns along the jaws of Eleotris amblyopsis larvae match closely those found on the late transitional larvae of Erotelis smaragdus. Typically, a suite of characters in combination serve to distinguish the larval types and unite transitional series.
The literature reports of fin-ray counts of sleepers can differ by two fin rays or more, and sometimes disagree on whether there are equal numbers of dorsal and anal-fin rays or more or less. The literature on larval sleepers is also not helpful, since features common to the entire family are typically cited as unique to one species or other and line drawings omit other diagnostic features (likely a result of inadequate sample sizes of highly-variable larvae).
Complex neuromast patterns develop on the head, body and caudal fins of late transitional eleotrid larvae. These patterns are more developed on juveniles and adults and are commonly used for taxonomic studies. Unfortunately, the neuromasts can be hard to highlight on most transitional larvae (photograph below, from the top, larval Erotelis smaragdus, Gobiomorus dormitor, and Eleotris amblyopsis).
The Gobiiformes /ˈɡoʊbi.ɪfɔːrmiːz/ are an order of fish that includes the gobies and their relatives.[1][2] The order, which was previously considered a suborder of Perciformes, is made up of about 2,211 species that are divided between seven families. Phylogenetic relationships of the Gobiiformes have been elucidated using molecular data.[3][4] Gobiiforms are primarily small species that live in marine water, but roughly 10% of these species inhabit fresh water. This order is composed chiefly of benthic or burrowing species; like many other benthic fishes, most gobiiforms do not have a gas bladder or any other means of controlling their buoyancy in water, so they must spend most of their time on or near the bottom.[5][6] Gobiiformes means "goby-like".
The 5th Edition of the Fishes of the World reclassified the former superfamily Goboidei as the order Gobiiformes and also rearranged the families within the order compared to the previous edition. The largest change is that the Oxudercidae and the Gobiidae are split into two families, with the Oxudercidae containing the species formerly classified as the Gobiidae subfamilies Amblyopinae, Gobionellinae, Oxudercinae and Sicydiinae while merging the families Kraemeriidae, Microdesmidae, Ptereleotridae and Schindleriidae into the family Gobiidae, though no subfamilies within the Gobiidae were proposed.[1]
Phylogeny of Gobiiformes[7][2] Trichonotoidei GobioideiOxudercidae (Gobionellidae)
Under this classification system the Gobiiformes is divided into the following families:
The loach-gobies are a small family, with only three species split between two genera, which inhabits marine and fresh water in Oceania and the western Pacific. These are thought to be among the more primitive species of the Gobiiformes.[1]
The Odontobutidae, or freshwater sleepers, contains 22 species between 6 genera from eastern Asia. This family is the sister to all the other Gobiiformes in a clade with the Rhyacichthyidae.[1]
The Milyeringidae contains two genera of cave fish, one in Western Australia and one at the other side of the Indian Ocean in Madagascar; both genera contain three recognized species. This family forms a second clade of the Gobiiformes.[1]
The sleeper gobies are a family of twenty six genera and 126 species found in freshwater and mangrove habitats throughout the tropical and temperate parts of the world as far north as the eastern United States and as far south as Stewart Island, New Zealand, except for the eastern Atlantic. Fossils of Eleotrid gobies are known from the Late Oligocene. The families Milyeringidae and Butidae were formerly classified as subfamilies of the Eleotridae but are not found to be close to the Eleotridae senus stricto in this system.[1]
The Butidae are one of the two families which are given the common name "sleeper gobies", and indeed were formerly classified as subfamily of the traditional sleeper goby family Eleotridae, although some phylogenies have placed them closer to the Oxucerdidae and the Gobiidae than to the Eleotridae. They are found in the Indo-Pacific and in West Africa, and contains 10 genera with 46 species split between them.[1]
The family Thalasseleotrididae is considered to be a sister group to the family Gobiidae and is separated as a family by the authors of this classification based on recent molecular studies. It comprises two genera of marine gobies from the temperate waters of Australia and New Zealand, with a total of three species between them.[1]
Oxudercidae is a family of gobies comprising species previously split between four subfamilies of the family Gobiidae. The family is sometimes referred to as the Gobionellidae, but Oxucerdidae has priority. The species in this family have a cosmopolitan distribution in temperate and tropical areas and are found in marine and freshwater environments, typically in inshore, euryhaline areas with silt and sand substrates. The family contains 86 genera and about 600 species. Many species in this family can be found in fresh water and a number of species are found on wet beaches; some are able to survive for extended periods out of water, most famously the mudskippers.[1]
The Gobiidae as recognized in this classification now includes the former members of several families which other classifications have regarded as valid families. As classified in this work the family remains one of the most speciose families of marine fish, as well as being one of the most numerous groups of fishes in freshwater habitats on oceanic islands. Many species have fused pelvic fins that can be used as a suction device; some island species, such as the red-tailed stream goby (Lentipes concolor), are able to use these pelvic fins to ascend rock faces alongside waterfalls, allowing them to inhabit waters far from the ocean.[10] Some of the species that are found in fresh water as adults spawn in the ocean and are catadromous, not unlike the eels of the family Anguillidae. With the blennies, the Gobiidae constitute a dominant part of the benthic, small fish fauna in tropical reef habitats. They are most diverse in the tropical Indo-West Pacific but the family is well represented in temperate waters in both the northern and southern hemispheres. They are mostly free living fishes found alone or in small schools, but some form associations with invertebrates, especially in coral reefs. About 120 species are known to form such symbiotic relationships; members of the genera Amblyeleotris and Cryptocentrus, for example, cohabit in burrows with alpheid shrimps, while other species live as cleaner fish, e.g Elacatinus. They can be sequential hermaphrodites and numerous species are known to exhibit parental care.[1]
The tidewater goby (Eucyclogobius newberryi) was listed as an endangered species in 1994; it is the only species of goby in the genus Eucyclogobius. E. newberryi is native to the coastal region of California, in marshes and lagoons with brackish water, predominantly in waters where the salinity is less than 12 parts per thousand (ppt), but has been documented in waters with a salinity of 42 ppt. E. newberryi prefers water with mild temperatures (8 to 25 °C) and waters with a depth from 25 to 200 cm. These gobies often use thick patches of aquatic vegetation to hide in if threatened or disturbed. The average lifespan of E. newberryi is only one year. Spawning and reproduction is at its peak during spring and into late summer. However, in the southern region of its range where waters remain at a warmer temperature, E. newberryi will reproduce year round. The females lay between 300 and 500 eggs into a burrow dug out vertically by the male, which is 10 to 20 cm deep. Spawning locations are usually located out in the open away from any vegetation. The male then guards the eggs until they hatch, which is 9 to 11 days.
Habitat loss and modification are the main threats to E. newberryi. The brackish areas where saltwater and freshwater meet are where they live usually, such as along the coast of California; this area has been altered by development. Barriers such as dikes and levees have been built to protect residents from potential flooding, but the creation of these barriers has reduced habitat for E. newberryi. Other reasons for population declines are attributed to exotic fish and amphibians which have been introduced to the region. Many of these fish prey on E. newberryi, and others outcompete them for food and habitat. The altering of streams flow with diversions has affected the salinity of the water and changed the habitat at creek mouths where E. newberryi has historically lived. Restoration projects have been started to bring populations back to a more stable number by making more habitat available, as well as providing protective areas. Some levees have been removed and exotic species reduction programs are being initiated.[11]
The Gobiiformes /ˈɡoʊbi.ɪfɔːrmiːz/ are an order of fish that includes the gobies and their relatives. The order, which was previously considered a suborder of Perciformes, is made up of about 2,211 species that are divided between seven families. Phylogenetic relationships of the Gobiiformes have been elucidated using molecular data. Gobiiforms are primarily small species that live in marine water, but roughly 10% of these species inhabit fresh water. This order is composed chiefly of benthic or burrowing species; like many other benthic fishes, most gobiiforms do not have a gas bladder or any other means of controlling their buoyancy in water, so they must spend most of their time on or near the bottom. Gobiiformes means "goby-like".
