Wednesday, December 8, 2021

[Ichthyology • 2021] Gobiomorphus dinae & G. mataraerore • Two New Cryptic Species of the Freshwater Fish Genus Gobiomorphus (Gobiiformes: Gobioidei: Eleotridae) in New Zealand

Gobiomorphus mataraerore 
 Thacker, Geiger & Shelley, 2021

Photos by Stella McQueen. 

We describe two new species in the genus Gobiomorphus, a radiation of fresh and brackish water gudgeons known from Australia and New Zealand. These species are a prominent component of New Zealand’s freshwater ichthyofauna and most are widely distributed throughout both the North and South Islands. Two of the inland species, G. breviceps and G. basalis, are composed of disjunct northern and southern populations that are distinguishable with molecular data. We examine individuals from across the ranges of both species, identify morphological differences between them, and describe two new species: Gobiomorphus dinae n. sp. (distinct from G. basalis) and Gobiomorphus mataraerore n. sp. (distinct from G. breviceps). Although the species are similar, they vary in dorsal spine count (G. dinae) and pectoral fin ray count (G. mataraerore). We provide mitochondrial COI sequences for each species pair to facilitate identifications by DNA barcoding. These species represent examples of divergence in allopatry, with diagnostic characters arising over the last 2−5 million years in the G. breviceps/G. mataraerore pair, and fewer than 2 million years in the G. basalis/G. dinae pair. We also designate a lectotype for G. basalis (the paralectotype is G. cotidianus) in order to clarify confusion surrounding the original syntypes.

KEYWORDS: Freshwater, amphidromy, endemic, gudgeon, Eleotridae, Gobiomorphus

Figure 1. Live colouration for Gobiomorphus basalis and Gobiomorphus dinae.
A. G. basalis male (Kirikiri stream, Coromandel). B. G. basalis female (Kirikiri stream, Coromandel).
C. Gobiomorphus dinae male (Turitea Stream, Manawatu). D. G. dinae female (Turitea Stream, Manawatu).
Photos of G. basalis by Rod Morris, photos of G. dinae by Stella McQueen.

Gobiomorphus dinae new species
Dinah’s bully 
Diagnosis: Gobiomorphus dinae is distinguished from G. basalis (Cran’s bully) in that it has one fewer dorsal spine (G. basalis have VIII; G. dinae have VII), usually more pectoral rays (18–19 instead of 16–18), and by its geographic range. It is distinguishable from G. breviceps and G. mataraerore in having more pectoral fin rays (18–19 instead of 14–16), and from G. alpinus in having more dorsal spines (VII as opposed to VI). Gobiomorphus dinae differs from G. hubbsi, G. huttoni, and G. gobioides in lacking open sensory pores on the head. It may be difficult to distinguish Gobiomorphus dinae from the common bully, G. cotidianus. Gobiomorphus cotidianus is widespread on both the North and South Islands and occurs throughout its range in both landlocked and amphidromous forms (Michel et al. 2008). The amphidromous form may be distinguished from G. dinae in that amphidromous G. cotidianus have open sensory pores on the head, at minimum a pair of lateral pores adjacent to the rear margins of the eyes and sometimes also a pair of median interorbital pores. Gobiomorphus dinae lacks these pores. The landlocked form of G. cotidianus does not have open sensory pores on the head and generally has fewer dorsal scales on the nape than the amphidromous form, such that the nape scalation pattern may be equivalent to that seen in G. dinae. Gobiomorphus dinae usually has one fewer anal ray than G. cotidianus (usually I, 8–9 vs. usually I, 10), and generally has a blunter head and more vertically inclined mouth; the head of G. cotidianus is flatter and more wedge-shaped in lateral view, and the mouth is correspondingly less acutely inclined. Mitochondrial COI (barcode) sequence for G. dinae is available under GenBank accession number MZ891637, and for G. basalis under MZ891638.

Etymology: The specific epithet dinae honours Dinah Arndt, in recognition of her unstinting support of freshwater fish research and fieldwork across both Australia and New Zealand.

Figure 4. Live colouration for Gobiomorphus mataraerore  and G. breviceps.
A. Gobiomorphus mataraerore male (Turitea Stream, Manawatu). B. G. mataraerore female (Turitea Stream, Manawatu).
C. G. breviceps male (Ohau River, MacKenzie Basin). D. G. breviceps male (back) and female (front; Stony Stream, Lammerlaw Range).
Photos of G. mataraerore by Stella McQueen, photos of G. breviceps by Rod Morris.

Gobiomorphus mataraerore new species
Kaharore bully
Diagnosis: Gobiomorphus mataraerore is distinguished from G. breviceps (Upland bully) in having one fewer pectoral ray (G. breviceps has 15–16; G. mataraerore has 14), usually fewer lateral scales (37–44 in G. mataraerore as opposed to 40–53 in G. breviceps), and by its geographic range. It is additionally distinguished from all other species in Gobiomorphus in having 14 pectoral rays (rather than 15–20 in the other species). Gobiomorphus mataraerore also differs from G. hubbsi, G. huttoni, G. gobioides and amphidromous G. cotidianus in lacking open sensory pores on the head. Mitochondrial COI (barcode) sequence for G. mataraerore is available under GenBank accession number MZ891639, and for G. breviceps under MZ891640.

Etymology: The specific name mataraerore is derived from the Maori words ‘mata’, meaning face (referring to the distinctive facial expression of Gobiomorphus fishes), and ‘rae’ meaning forehead (referring to the elongate forehead), and ‘rore’ in honour of the type locality that lies within the region traditionally referred to as Kaharore (a traditional bird snare). Noun in apposition.

We describe two new species, Gobiomorphus dinae and G. mataraerore, each representing geographically isolated subpopulations of existing species. Gobiomorphus dinae is separated from G. basalis by the Taupo Volcanic Zone on the North Island, and G. mataraerore is separated from G. breviceps by the Southern Alps. Both species pairs are similar but distinguishable by fin ray counts. We additionally resolve confusion surrounding the syntypes of G. basalis: the two syntypes are different species, and we designate one as the lectotype of G. basalis and the other as a paralectotype identified as G. cotidianus.

Christine E. Thacker, Daniel L. Geiger and James J. Shelley. 2021. Two New Cryptic Species of the Freshwater Fish Genus Gobiomorphus (Gobiiformes: Gobioidei: Eleotridae) in New Zealand. New Zealand Journal of Marine and Freshwater Research.  DOI: 10.1080/00288330.2021.2007959