Cyprinodon brontotheroides (MARTIN & WAINWRIGHT, 2013) – Durophage Pupfish

Etymology

• “Cyprinodon” is derived from the Greek words “κυπρῖνος” (kuprinos), which means “carp,” and “ὀδούς” (odous), which means “tooth.”
• The species “brontotheroides” is named after its distinct protruding nasal region, which bears a striking resemblance to the horn-like skull appendages of the extinct Brontotheriidae family, a group of odd-toed ungulates.

Classification

Order: Cyprinodontiformes Family: Cyprinodontidae

Distribution

This species is found exclusively on San Salvador Island in the Bahamas and can be observed in six hypersaline lakes, namely Crescent Pond, Osprey Lake, Oyster Lake, Little Lake, Wild Dilly Pond, and Moon Rock Pond.

The type locality of this species is situated in Crescent Pond, which is approximately 1 km southeast of the Gerace Research Centre on San Salvador Island. Its geographic coordinates are 24°06’45″N latitude and 74°27’28″W longitude.

Habitat

Cyprinodon brontotheroides (MARTIN & WAINWRIGHT, 2013) – Durophage PupfishThis species can occasionally be found in wigeongrass (Ruppia maritima) patches, but in general, it does not exhibit any specific habitat preferences beyond the typical littoral habitat preferences of its genus.

It co-occurs with its congener C. variegatus in all six lakes and with C. desquamator in four of them.

While most Cyprinodon species have a diet consisting of algae and organic detritus and exhibit allopatric patterns of distribution, despite inhabiting a diverse range of environments, including freshwater rivers and lakes, brackish estuarine waters, isolated springs, and hypersaline lagoons, those residing in San Salvador and Lake Chichancanab in Quintana Roo state, Mexico, have evolved into groups of species that occur in sympatry and exploit a variety of specific resources, displaying remarkable morphological adaptations (refer to ‘Notes’).

Regrettably, some of the Chichancanab species are no longer found in their natural habitat due to the introduction of Oreochromis spp. (tilapia) and Astyanax affinis during the 1990s. Martin and Wainwright (2013b) have cautioned that a comparable situation may occur on San Salvador, given that Oreochromis has already been discovered in at least two bodies of water.

Maximum Standard Length

As of now, the individual with the greatest size on record measures 36.1 mm.

Diet

The animal in question is a specialized durophage, which means that it preys on hard-shelled invertebrates, notably gastropods and ostracods. Its physical adaptations for this behavior include altered jaw morphology that enables it to exert more force and crush shells effectively.

Sexual Dimorphism

Fully grown males of this species exhibit metallic blue speckling on their anterodorsal region, unlike their counterparts, which display dark pigmentation on their bodies and fins. They also have a black margin on their caudal fins. During breeding season, the males may show orange coloring on their ventral area. In contrast, females and juveniles have a black and white ocellus on their dorsal fin.

Reproduction

The male individuals of this species protect their breeding territories in midwater, typically at a depth of 0.5 to 1 meter. Although breeding behavior has been observed throughout the year, it appears to be more prevalent during the spring season.

Notes

Before it was officially described, this species was referred to as either “C. sp. ‘durophage'” or “C. sp. ‘bozo'”. One of its distinguishing features is that the anterior process of its maxillary head extends beyond the dentigerous arm of the premaxilla, resulting in a shorter upper jaw compared to other similar species like C. variegatus and C. desquamator. This bony extension can be seen as a fleshy bulge that almost envelops the upper jaw when it is retracted.

Compared to C. variegatus and C. desquamator, the paired nasal bones of this species do not appear to be enlarged but they form a sharper angle (around 120 degrees) with the dorsal margin of the neurocranium.

Since no other species in the Cyprinodon genus are known to specialize in consuming hard-shelled prey, researchers have conducted studies to determine the factors that may have driven the evolution of this ecological specialization. You can find more information by clicking on the provided link.

References

1. Martin, C. H. and P. C. Wainwright, 2013b – Bulletin of the Peabody Museum of Natural History 54(2): 231-240
   Remarkable Species Flock of Cyprinodon Pupfishes Endemic to San Salvador Island, Bahamas.
2. Martin, C. H. and P. C. Wainwright, 2013a – Science 339(6116): 208-211
   Multiple Fitness Peaks on the Adaptive Landscape Drive Adaptive Radiation in the Wild.
3. Martin, C. H. and P. C. Wainwright, 2011 – Evolution 65(8): 2197-2212
   Trophic novelty is linked to extremes rates of morphological diversification in two adaptive radiations of Cyprinodon pupfishes.