Morphology data of Plesionika trispinus
Identification keys
Main Ref. Squires, H.J. and J.H. Barragan, 1976
Appearance refers to

Sex attributes

specialized organs
different appearance
different colors
remarks

Descriptive characteristics of juvenile and adult

Striking features
Body shape lateral
Cross section
Dorsal head profile
Type of eyes
Type of mouth/snout
Position of mouth
Diagnosis The species has a long up-curving rostrum about 1.5 time s as long as the carapace. The rostrum has 11 to 14 spines above, the first three of which on the carapace are in front of the orbit and in rapidly ascending height, and form a group separated from the others by a short space. The group of three are sutured at the base and moveable. The others on the rostrum are not sutured but are fixed spines in an almost equidistant series. One sub apical spine is separated fro m the others by a space almost one-half the length of the rostrum. Ventrally on the rostrum are 10 to 18 closely spaced and fixed spines progressively mo re separated distally. The integument of the carapace appears to be minutely pitted, although no scales were seen. The antennal spine is very strong and has a low rounded carina. The pterygostomian spine is small. Laterally on the carapace is a low curving ridge extending from near the orbit to near the posterior edge. Beside and above the ridge in the hepatic region is one oval depression and two others below the ridge. There is also a faint impression of a cervical groove dorsally. The abdomen has no dorsal spines on any of the tergites but the area of muscle attachment dorsally on the second and third segments is deeply indented transversely. The pleura of the fourth and fifth segments are produced posteriorly, each ending in a spine. The sixth segment is not quite twice the length of the fifth and has a spine ventrolaterally at the posterior end. The telson is slightly (one-tenth) longer than the sixth segment and has two low carinae that bear four pairs of moveable spinules, the first pair of which is separated from the others. The apex is acuminate, with a lateral pair of long spines and a median pair much smaller (less than half the length). The outer edges of the outer branches of the uropods end in a sharp projection in the axil of which is a moveable spine. A fringe of short setae is inside the edge of this branch for its entire length. The first and second pereiopods are about the same length, reaching forward just beyond the series of dorsal spines on the rostrum. The first have microscopic chelae. The second pereiopods are approximately equal to each other in size, length, etc., with 14 to 17 annulations on the carpus and with slender chelae. The third to fifth legs are longer than the first and about equal in length to each other (not quite reaching the tip of the rostrum when stretched forward), but their dactyli are unequal, decreasing in size from the third to the fifth leg. The dactylus of the fifth leg is a little more than one-half the length of the propodus. The pleopods have endopods modified according to sex: in the male the first pleopod is short, wide, and foliacious with a truncate appendix interna tipped with cinncinnuli; in the female it is long and tapering to a point and with many setae. The appendix masculina of the otherwise unmodified second pleopod is slightly longer than the appendix interna in mature males and is tipped with several long setae.
Ease of Identification

Meristic characteristics of Plesionika trispinus

Lateral Lines Interrupted: No
Scales on lateral line
Pored lateral line scales
Scales in lateral series
Scale rows above lateral line
Scale rows below lateral line
Scales around caudal peduncle
Barbels
Gill clefts (sharks/rays only)
Gill rakers
on lower limb
on upper limb
total
Vertebrae
preanal
total

Fins

Dorsal fin(s)

Attributes
Fins number
Finlets No. Dorsal   
Ventral  
Spines total
Soft-rays total
Adipose fin

Caudal fin

Attributes

Anal fin(s)

Fins number
Spines total
Soft-rays total

Paired fins

Pectoral Attributes  
spines     
soft-rays   
Pelvics Attributes  
Position    
spines     
soft-rays   
Main Ref. (e.g. 9948)
Glossary (e.g. cnidaria)
Comments & Corrections
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