This past September Richard Pyle and Randall Kosaki published the official description of the deepwater Prognathodes basabei. Best of all it’s free to read and some great pictures of this Butterfly can be seen. Sidebar: Prognathodes remain one of my favorite group of fish. I’ve been fortunate enough to own a variety of species […]
This past September Richard Pyle and Randall Kosaki published the official description of the deepwater Prognathodes basabei. Best of all it’s free to read and some great pictures of this Butterfly can be seen.
Sidebar: Prognathodes remain one of my favorite group of fish. I’ve been fortunate enough to own a variety of species such as P. aya, or the Banks Butterfly. One of my most testing experiences in this hobby, and one I’ll never forget, was weaning a P. guyanensis onto prepared foods. (Thanks Copps…) These fish can be stubborn in captivity, but under the proper care (read: often need a chiller and docile tank mates) they can adapt well and be incredibly personable and intelligent.
Back to this fish: I’ve written about this particular species since 2009. It’s been known as P. basabei, or the Orange Margined Butterflyfish, well before that and before official description thanks to Peter Basabe’s early collection with Pyle. In the paper, Pyle and Kosaki explain the story, below, and also include a section where they discuss naming the species in Peter’s namesake for his contributions:
While conducting an exploratory dive using a mixed-gas closed-circuit rebreather off the south shore of O‘ahu on 17 May 1998, the senior author (RLP) observed (but was unable to collect) a group of three Prognathodes near an undercut limestone ledge at a depth of 114 m. Two weeks later (30 May 1998), with the assistance of Peter K. Basabe, RLP collected the first specimen of this species at a depth of 120 m near Kealakekua Bay on the Kona coast of the island of Hawai‘i (TenBruggencate 1998). The following day he collected several more individuals at a depth of 115 m near the site of the observation of 17 May (Allen et al. 1998). All of the collected individuals were brought to the surface alive and maintained in captivity. Unfortunately, when they eventually died, only one was preserved, and it was too badly deteriorated to serve as a type specimen.
The specimen shown here on GBD was collected in 2011 by Rufus Kimura via a mixed-gas re-breather in Hawaii, where it is known to be be endemic. (Some of you may know Rufus for his talk at MACNA ’14. A great guy and a major hat tip to him is in order for sharing his photos with GBD over the years.) P. basabei has been collected at depths of 45–187 m throughout the Hawaiian Archipelago. Interestingly it has not been seen at the nearby Johnston Atoll or throughout central or eastern Pacific for that matter.
One catch in the paper is authors note the species is typically only found in groups of three. Unfortunate for hobbyists’ wallets, but something to keep in mind if you’re serious about caring for this gem.
Every observation of adults of this species by the authors during mixed-gas dives in both the main Hawaiian Islands and NWHI (nearly two dozen instances), as well as observations by RLP during several submersible dives off south O‘ahu in 2011, involved groups of three individuals; the only exception was the solitary juvenile observed by RLP in 1998. Only two individuals of the Palau species were observed together, and none of the approximately ten individuals of Prognathodes guezei observed by RLP at depths of 115–120 m off Sodwana Bay in 2011 were found in a group of three.
The Orange Margined Butterflyfish shares the classic Prognathodes snout, strong dorsal spines and vertical striping. The paper cites its closest relative as an undescribed Prognathodes species found in Palau. Pyle et al. estimate the two species likely diverged ~4 million years ago!
Genetic comparisons provide another compelling justification for regarding Prognathodes basabei as distinct from the Palau species. The vertebrate mtDNA barcode sequences obtained from the holotype and two paratypes of Prognathodes basabei, compared to specimens of Prognathodes sp. collected in Palau, reveal 8% uncorrected sequence divergence. This is consistent with species-level divergences in other fish taxa. The accepted mtDNA clock rate of approximately 2% per million years in fishes indicates divergence between these species on the order of 4 million years.
No tissue samples or DNA sequences have been reported for Prognathodes guezei, but given the geographic distributions of Prognathodes guezei in the western Indian Ocean, the Palau species, and Prognathodes basabei, we anticipate that the genetic divergence between Prognathodes basabei and Prognathodes guezei will prove to be even deeper than that between Prognathodes basabei and the Palau species.
P. basabei is just the 12th member of Prognathodes and the authors suggest there’s more. P. basabei is the latest in Hawaii, while in the southwest Indian Ocean we have P. guezei as well as the undescribed species in Palau. The authors suggest, and I would agree, these gaps in Prognathodes known distribution is likely tied to “the death of mesophotic exploration across the tropical central and western Pacific and Indian Oceans.”