Pighead prickleback COSEWIC assessment and status report: chapter 3

Species Information

Name and classification

Family:

Stichaeidae (pricklebacks)

Subfamily:

Lumpeninae

Genus:

Acantholumpenus

Species:

mackayi

English common name:

Pighead Prickleback

Synonym:

Blackline Prickleback

French common name:

terrassier à six lignes

Inuit name:

none (McAllister 1987)

Description and taxonomy

As a member of the family Stichaeidae, pighead pricklebacks have a slender eel-like (anguilliform) body and a long dorsal fin consisting of spinous rays that extend behind the head to the base of the tail (Fig. 1).  Their abdominal vertebrae do not have haemal arches unlike similar-looking gunnels (family Pholidae).  Baxter (1988ms) and Wilimovsky (1958) assigned Alaskan pighead pricklebacks to the genus Lumpenus and identified it by:  1) the gill membranes extending well forward on the gill isthmus without forming a free fold or being broadly fused to the gill isthmus; 2) the lateral line absent or rudimentary; 3) presence of two spinous anal fin rays; 4) more than 67 spinous dorsal rays; 5) shorter snout; 6) tips of dorsal spines not free of fin membranes; and 7) lower pectoral fin rays shorter than middle rays.  Morphologically, pighead pricklebacks can be distinguished from their closest related congener, Lumpenus, by thickened lips, a stout head and proportionally smaller eyes having a less distinct border (Fig. 2).  Their lips (especially maxilla) are considerably deeper in large fish (Fig 2).  When their mouth is completely closed, the lower jaw fits inside the maxillary and pre-maxillary bones, causing a ventral orientation to the mouth expected on bottom living fish.

Figure 1. Illustration of Acantholumpenus mackayi (from Environment Canada, “Species at Risk” web page 2002).

Figure 1.  Illustration of Acantholumpenus mackayi (from Environment Canada, “Species at Risk” web page 2002).

Figure 2. Diagrammatic comparison of head and mouth structure in larger specimens of Lumpenus-like fishes: A) 288 mm specimen of Acantholumpenus mackayi (Royal BC Museum specimen) from Bering Sea, with much thicker maxilla, blunter head, and smaller eye having an indistinct border;
B) similar view of 297 mm Lumpenus sagitta (Royal BC Museum 974-448) with narrower lips, proportionally larger eye with distinct borders and more elongate snout.

Figure 2.  Diagrammatic comparison of head and mouth structure in larger specimens of Lumpenus-like fishes.

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