Trypauchen Valenciennes in Cuvier & Valenciennes, 1837

Edward O. Murdy, 2006, A revision of the gobiid fish genus Trypauchen (Gobiidae: Amblyopinae)., Zootaxa 1343, pp. 55-68 : 57-61

Trypauchen Valenciennes in Cuvier & Valenciennes, 1837

Trypauchen Valenciennes in Cuvier & Valenciennes, 1837 : 152 (type species: Gobius vagina Bloch and Schneider, 1801 , by original designation and monotypy)

Included species. Trypauchen comprises two species: T. pelaeos n. sp. and T. vagina

Etymology. From the Greek trypa (hole) and auchen (neck).

Diagnosis. Trypauchen is distinguishable from the other amblyopine genera with an opercular pouch in having: four pterygiophores anterior to the first hemal spine (rarely three); small funnel-like pelvic fin with I,4 or I,5 rays and well-developed interradial membrane; and abdomen with scales.

Description. The following description of meristic counts (Table 1) is based on radiographs, and four cleared and stained specimens (one each of T. vagina removed from AMS I.43479-001 and USNM 342640 and two of T. pelaeos from USNM 385741).

Total dorsal-fin elements 46-58; first dorsal fin with six flexible spines (one specimen of T. vagina with five); all second dorsal-fin rays segmented and branched; dorsal-fin base long and broadly joined with caudal fin. Total anal-fin elements 39-50, all elements segmented and branched; anal-fin height less than second dorsal-fin height; anal-fin membrane broadly joined with caudal fin. Pectoral fin with 15-20 rays, crescent-shaped or falcate with upper rays longer than lower ones; all pectoral-fin rays segmented and branched distally. Pelvic-fin rays I,4 or I,5; broad frenum present; medial rays longest and completely united by interradial membrane; pelvic fins forming a small funnel that is slightly pointed posteriorly. Caudal fin with 17 segmented rays including 8+7 branched rays and an upper and lower simple ray; unsegmented procurrent rays 4, 2 dorsally and 2 ventrally.

Scales cycloid, present only on body, largest posteriorly, scales overlapping in caudal peduncle area. Longitudinal scale count 59-98, difficult to count with accuracy.

Typically, two rows of teeth in the upper and lower jaws; all teeth caninoid. Outer-row teeth much larger and stouter than those of inner row; lower-jaw teeth larger than upperjaw teeth. Outer row of upper jaw with 4-16 enlarged, canine teeth; 8-15 enlarged, canine teeth in outer row of lower jaw; numerous smaller canine teeth in inner row of upper and lower jaws. When mouth closed, upper jaw overlapped by lower jaw. No palatine or vomerine teeth present.

Tongue thick, tip rounded, free from floor of mouth. Gape wide, mouth oblique; maxilla extending posteriorly to the vertical with anterior half of orbit; posteriorly, near tip of maxilla, upper lip expanded into large fold that joins similar fold of lower lip at rictus, fold completely covers posterior part of jaws even when agape. No barbels on underside of head.

Eye rudimentary and covered by skin in orbital depression, lens slightly larger than length of posterior naris. Posterior naris located on dorsoanterior rim of orbit; anterior naris at tip of small tube-like flap that slightly overhangs upper jaw. Chin, snout, and interorbital area with thickened flesh, which likely aids in burrow construction.

Cephalic sensory canals and pores absent. Sensory papillae present on head and body, but difficult to observe without use of a stain. Prominent pouch of unknown function along the dorsal margin of the opercle (Fig. 1).

Gill rakers short, blunt, and not ossified; gill opening narrow, extending only the length of pectoral-fin base or slightly more ventrally.

Genital papilla large. In males, the papilla is pointed posteriorly, in females it is slightly rounded or truncate posteriorly.

Proportional measurements are given in Table 2.

Osteology. Spinous dorsal-fin pterygiophore formula (PF) typically 3-1221 (one specimen of T. vagina with 3-122 and one specimen of T. vagina with 3-1211). Precaudal vertebrae 10, caudal vertebrae 19-20 or 23-24. Pterygiophore of the second soft dorsal-fin ray (posteriormost pterygiophore inserting in 7th interneural space) with an autogenous middle radial. Typically four anal-fin pterygiophores anterior to first hemal spine, two specimens with three. Epurals 2. Basihyal spatulate. No gap between dorsal aspect of symplectic and hyomandibula as symplectic is broadly joined to hyomandibula. An anteriorly directed laminar extension of the preopercle articulates with the ventroposterior edge of the symplectic. Frontal crest low, without serrated edge. Frontals divided by a septum anteriorly into two open canals. Atlas with well-developed parapophyses, in contact with first epineural rib. Epineurals present from 1st precaudal vertebra to at least the 14th and sometimes the 18th caudal vertebra. Well-developed pleural ribs on 3rd to 9th precaudal vertebrae.

Comparison of Trypauchen with other ‘Trypauchen’ group members and status of T. microcephalus , T. raha , T. taenia , and T. wakae . Based on their shared absence of an interneural gap, Birdsong et al (1988) created the monophyletic unit called the ‘Trypauchen’ group that comprised Amblyotrypauchen , Caragobius , Trypauchen , and Trypauchenichthys . Murdy (2002) added Ctenotrypauchen and a new genus ( Karsten ) to the ‘Trypauchen’ group and provided a key to the ‘Trypauchen’ group genera. Additionally, four species currently assigned to the genus Trypauchen are treated separately here as members of the ‘Trypauchen’ group : T. microcephalus , T. raha , T. taenia , and T. wakae . Monophyletic subunits of the ‘Trypauchen’ group can be hypothesized based on the following characters:

Opercular pouch (Fig. 1). Caragobius and Karsten lack an opercular pouch whereas the other members of the ‘Trypauchen’ group possess an opercular pouch, a unique character not found in any other amblyopines nor in any other gobioids. Hence, the presence of an opercular pouch is considered the derived condition.

Number of anal-fin pterygiophores anterior to the first hemal spine (AP). All ‘Trypauchen’ group members with an opercular pouch typically have three or fewer AP except for Trypauchen vagina and T. pelaeos n.sp., which typically have four AP. As the sister group ( Caragobius and Karsten ) to those ‘Trypauchen’ group members that have an opercular pouch typically have four or more AP, the condition of typically having three or fewer AP is hypothesized as the derived condition.

Structure of the pelvic fins (Fig. 2). United pelvic fins forming a cup- or funnel-shaped disc with the medial rays joined completely by an interradial membrane is the typical gobiid condition. This condition is considered plesiomorphic within the Gobiidae. All ‘Trypauchen’ group members with an opercular pouch have emarginate or separate pelvic fins except for Trypauchen vagina and T. pelaeos n. sp. Emarginate or separate pelvic fins are considered derived.

Presence of scales on the abdomen. Trypauchen vagina , T. pelaeos n. sp., and all other ‘Trypauchen’ group members with an opercular pouch have scales on the abdomen except T. microcephalus , T. raha , and T. wakae . The absence of scales on the abdomen is hypothesized as being the derived condition.

Frontal crest. All ‘Trypauchen’ group members with an opercular pouch lack an exposed frontal crest except Ctenotrypauchen , Trypauchenichthys , and T. taenia , which all have an exposed, serrated frontal crest. An exposed, serrated frontal crest is considered derived.

Presence of head scales. All ‘Trypauchen’ group members with an opercular pouch lack scales on the head except Amblyotrypauchen (Murdy, 2003). Amblyotrypauchen has scale patches on the head, cheek and opercle; this is considered a derived character.

Based on the character polarities described above, I hypothesize that Trypauchen vagina and T. pelaeos , n.sp. form the sister group to Amblyotrypauchen , Ctenotrypauchen , Trypauchenichthys and the four remaining nominal species of Trypauchen ( T. microcephalus , T. raha , T. taenia and T. wakae ). Three nominal species of Trypauchen (i.e., T. microcephalus , T. raha , and T. wakae ) are united by synapomorphies (i.e., three or fewer AP, emarginate pelvic fins, and absence of abdominal scales) not found in combination in any other ‘Trypauchen’ group genus and, thus, cannot be assigned at this time. As for T. taenia , this species is hypothesized to be a member of the monophyletic unit containing Ctenotrypauchen and Trypauchenichthys . These four nominal species of Trypauchen , T. microcephalus , T. raha , T. taenia , and T. wakae , will be treated in greater detail in forthcoming papers as revisionary studies of amblyopine gobies continue.

Key to the species of Trypauchen

1a. Total elements in dorsal fin 50-58; total elements in anal fin 43-50; caudal vertebrae 23 or 24, typically 24; SL typically 84% or more of total length; head length less than 18% of SL; predorsal length less than 22% of SL; prepelvic length less than 18% of SL; preanal length 36% or less of SL. (Kuwait, India, Thailand, Vietnam, Philippines, China) ............................................................................................................... T. vagina

1b. Total elements in dorsal fin 46-52; total elements in anal fin 39-44; caudal vertebrae 19 or 20; SL 84% or less of total length; head length 18% or more of SL; predorsal length typically more than 22% of SL; prepelvic length 18% or more of SL; preanal length more than 36% of SL. (Myanmar, Thailand, Malaysia, Vietnam, China) ........... .............................................................................................................. T. pelaeos , n. sp.